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Lorraine Cassidy FRCOphth<br />
Paediatric cataract<br />
Cataract in children often interferes with normal visual<br />
development and is a significant cause of visual<br />
handicap. Therefore, it is an important problem to pick<br />
up and treat as early as possible.<br />
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The College of<br />
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CET credits. There are<br />
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pass mark of 60%.<br />
Cataract in childhood can be classified as<br />
congenital, infantile and juvenile,<br />
depending on <strong>the</strong> age of onset. Congenital<br />
cataract is present at birth, but may not be<br />
obvious and <strong>the</strong>refore can go unnoticed<br />
until it is observed to have an effect on <strong>the</strong><br />
child’s visual function. Infantile cataract<br />
refers to cataract which develops in <strong>the</strong> first<br />
two years of life, and juvenile cataract has a<br />
later onset (many lens opacities which are<br />
classified as infantile or juvenile are, in<br />
fact, congenital cataracts which were not<br />
picked up at birth).<br />
Childhood cataract can also be classified<br />
according to aetiology, (i.e. traumatic<br />
cataract, autosomal dominant cataract etc),<br />
and morphology (i.e. lamellar cataract,<br />
subcapsular, cortical etc).<br />
The importance of making <strong>the</strong> diagnosis<br />
and rapidly implementing treatment of<br />
cataract in <strong>the</strong> young child cannot be overemphasised,<br />
as it is <strong>the</strong> major preventable<br />
cause of lifelong visual impairment. A<br />
simple examination of <strong>the</strong> red reflex in <strong>the</strong><br />
newborn child allows this all too important<br />
diagnosis to be made (Figure 1).<br />
Aetiology<br />
1. Hereditary cataract<br />
Hereditary cataract is passed from one<br />
generation to <strong>the</strong> next in autosomal<br />
dominant fashion in 75% of cases of<br />
congenital cataract 1 . The affected<br />
individuals are usually perfectly well, and<br />
have no associated systemic illness. Less<br />
commonly, <strong>the</strong> inheritance may be<br />
autosomal recessive 2 .<br />
However, <strong>the</strong>re are a number of rare<br />
hereditary syndromes where <strong>the</strong> affected<br />
individual not only has cataract, but also<br />
has an associated systemic illness, for<br />
example kidney and brain disease in Lowe’s<br />
oculo-cerebro-renal syndrome, which is X-<br />
linked recessive. It is, <strong>the</strong>refore, important<br />
that all children with congenital cataract are<br />
examined by a paediatrician to exclude any<br />
underlying systemic disorder.<br />
2. Metabolic cataract<br />
Congenital, infantile or juvenile lens<br />
opacities may have an underlying metabolic<br />
cause, for example, galactosaemia 3 .<br />
Galactosaemia is a metabolic disorder in<br />
which <strong>the</strong> child’s body cannot metabolise<br />
galactose, a major component of milk and<br />
milk products. The baby will have vomitting<br />
www.optometry.co.uk<br />
Figure 1<br />
Red reflex revealing a posterior subcapsular cataract after X<br />
ray irradation of <strong>the</strong> eye<br />
and diarrhoea, and develops typical ‘oil<br />
droplet’ cataracts which are easily seen by<br />
examining <strong>the</strong> red reflex. These are<br />
reversible, and <strong>the</strong> lens returns to normal on<br />
removing dairy products from <strong>the</strong> diet. If<br />
this condition is not picked up and treated,<br />
it leads to dense cataracts, deafness and<br />
death.<br />
Glucose-6-phosphate dehydrogenase<br />
deficiency is an X- linked disorder and<br />
<strong>the</strong>refore affects mainly males. These babies<br />
present with jaundice and have haemolytic<br />
anaemia, and may also develop infantile<br />
cataract. Infection, acute illness and<br />
ingestion of fava beans will precipitate an<br />
attack of haemolysis (rupture of red blood<br />
cells) in <strong>the</strong>se children. Death may result,<br />
unless <strong>the</strong> condition is diagnosed and<br />
treated with an urgent blood transfusion.<br />
Hypoglycaemia of whatever cause may<br />
give rise to lens opacities in a child 4 . The<br />
majority of babies with hypoglycaemia this<br />
profound will also have convulsions and may<br />
have permanent brain damage.<br />
Hypocalcaemia may result in cataracts 5<br />
(Figure 2), though <strong>the</strong>se are usually<br />
functionally less significant than cataracts<br />
resulting from hypoglycaemia.<br />
Mannosidosis is an autosomal recesively<br />
inherited metabolic disease which can be<br />
associated with infantile cataracts 6 . In this<br />
disorder, <strong>the</strong> deficient enzyme is alpha<br />
mannosidase, and <strong>the</strong>se children also have<br />
corneal clouding and optic atrophy. O<strong>the</strong>r<br />
features include deafness, skeletal dysplasia<br />
and mental retardation which is variable.<br />
3. Traumatic cataract<br />
Trauma is <strong>the</strong> most common cause of<br />
unilateral cataract in children. Traumatic<br />
cataract is usually <strong>the</strong> result of a<br />
penetrating injury, though blunt trauma can<br />
also lead to cataract formation.<br />
Figure 2<br />
Lamellar cataract in a patient with a previous<br />
episode of hypocalcaemia<br />
27
ot<br />
4. Secondary cataract<br />
The most common type of secondary<br />
cataract seen in <strong>the</strong> paediatric<br />
ophthalmology clinic is as a result of uveitis<br />
seen in conjunction with arthritis (juvenile<br />
chronic arthritis (JCA)). The cataract may be<br />
as a direct result of inflammation within <strong>the</strong><br />
anterior segment, or can also result from<br />
<strong>the</strong> steroids used to treat <strong>the</strong> condition.<br />
Cataracts caused by steroid ingestion are<br />
usually posterior subcapsular. Progression of<br />
<strong>the</strong> cataract will be halted following<br />
cessation of treatment although not<br />
reversible.<br />
Less frequently, cataract may be seen<br />
secondary to an intraocular tumour such as<br />
retinoblastoma. Retinoblastoma is a<br />
malignant tumour of <strong>the</strong> retina and can<br />
spread to <strong>the</strong> brain resulting in death,<br />
thus immediate referral and treatment is<br />
vital.<br />
5. Cataract secondary to maternal<br />
infection during pregnancy<br />
The most common maternal infection to<br />
cause congenital cataract in <strong>the</strong> child is<br />
rubella, more commonly known as German<br />
measles. The cataracts caused by rubella<br />
may be present at birth, or develop several<br />
months later. These children may also have<br />
microphthalmia, glaucoma, retinal<br />
disease, microcephaly, deafness and heart<br />
defects.<br />
O<strong>the</strong>r infectious diseases which may<br />
have affected <strong>the</strong> mo<strong>the</strong>r during pregnancy,<br />
such as toxoplasmosis (picked up from cat’s<br />
faeces), toxocariasis (picked up from dog’s<br />
faeces), and cytomegalovirus (CMV) can also<br />
cause congenital cataracts along with<br />
systemic illness in <strong>the</strong> newborn baby.<br />
6. Iatrogenic cataract<br />
Iatrogenic cataract is most commonly seen<br />
in children who have had total body<br />
irradiation 7 for leukaemia, and in children<br />
who have had organ transplants and are on<br />
long-term systemic steroid <strong>the</strong>rapy 8 . These<br />
children are usually older children and do<br />
very well after cataract surgery.<br />
7. Syndromes and congenital cataract<br />
There are large variety of chromosomal and<br />
dysmorphic syndromes, in which <strong>the</strong> child<br />
will have a high risk of having congenital<br />
cataract (Table 1). It is important to notice<br />
any abnormal features in children presenting<br />
with cataract, such as unusual facial<br />
features, extra digits, unusual skin, short<br />
stature, developmental delay, microcephaly<br />
or hydrocephaly, as it is essential that <strong>the</strong><br />
child’s diagnosis is made so that any<br />
necessary treatment is given to <strong>the</strong> child,<br />
and so <strong>the</strong> parents can receive genetic<br />
counselling about <strong>the</strong> possible risks of<br />
producing o<strong>the</strong>r offspring with similar<br />
problems.<br />
Presentation<br />
How do children with cataracts present?<br />
Obviously, older children are able to tell<br />
<strong>the</strong>ir parents and carers that <strong>the</strong>y are<br />
having visual difficulties. A very shy and<br />
quiet child may not complain, but <strong>the</strong>ir<br />
school-work may deteriorate and an<br />
observant teacher may become suspicious<br />
that <strong>the</strong> child is having visual difficulties.<br />
However, all is not so straightforward<br />
with <strong>the</strong> non-verbal infant or child. These<br />
babies may present in different ways. For<br />
example, <strong>the</strong> mo<strong>the</strong>r or o<strong>the</strong>r family member<br />
may notice leukocoria (a white pupil). The<br />
Table 1 Chromosomal and dysmorphic syndromes associated with congenital cataract<br />
I. CONGENITAL CATARACT AND<br />
DYSMORPHIC FACIAL FEATURES<br />
II. CONGENITAL CATARACT AND<br />
SHORT STATURE<br />
III. CONGENITAL CATARACT<br />
AND MICROCEPHALY<br />
1. Trisomy 21 (Down’s syndrome)<br />
2. Hallermann-Streiff-Francois syndrome<br />
(characterised by certain facial features<br />
such as a thin pointed nose, small<br />
pointed chin, and can be associated<br />
with breathing difficulties and in 15%<br />
mental reardation)<br />
3. Lowe’s oculo-cerebro-renal syndrome<br />
(an X-linked recessive condition<br />
characterised by chubby cheeks, renal<br />
problems, congenital cataract and<br />
glaucoma)<br />
4. Nance-Horan syndrome (an X-linked<br />
condition characterised by abnormal<br />
dentition, prominent ears and congenital<br />
cataract)<br />
5. Smith-Lemli-Opitz syndrome (an<br />
autosomal recessive condition in which<br />
<strong>the</strong> children may have microcephaly,<br />
cleft palate, congenital cataract and<br />
overlapping fingers and toes)<br />
6. Congenital cataract, microphthalmia,<br />
septal heart defect and dysmorphic<br />
facial features<br />
IV. CONGENITAL CATARACT AND<br />
DIGITAL ABNORMALITIES<br />
1. Majewski syndrome (nornatal dawrfism,<br />
extra fingers [polydactyly], cleft palate<br />
2. Smith-Lemli-Opitz syndrome (see<br />
above)<br />
3. Schachat and Maumenee’s patient<br />
(1982) - congenital cataract, mental<br />
retardation; obesity; hypogenitalism;<br />
skull deformities; polydactyly<br />
1. Chondrodysplasia punctata (an<br />
autosomal recessive condition<br />
characterised by short limbs, abnormal<br />
skin and typical skeletal features on x-<br />
ray)<br />
2. Autosomal recessive mental retardation,<br />
cataract, ataxia, deafness and<br />
polyneuropathy<br />
3. Cataract, sensoryneural deafness;<br />
hypergonadism; hypertrichosis; short<br />
stature<br />
4. Marinesco-Sjögren’s syndrome (an<br />
autosomal recessive condition<br />
characterised by unsteadiness of gait,<br />
poor co-ordination, short stature and<br />
mental retardation)<br />
V. CONGENITAL CATARACT AND<br />
DERMATOLOGICAL DISEASE<br />
1. Conradi’s syndrome/Conradi-<br />
Hunermann syndrome (short limbs, skin<br />
changes [pitted skin] and skeletal<br />
abnormalities)<br />
2. Pollitt syndrome – (mental retardation,<br />
brittle hair, short stature and skin<br />
abnormalities)<br />
3. Menke’s disease (an X-linked condition<br />
characterised by severe mental<br />
retardation, kinky hair, bone and<br />
connective tissue abnormalities)<br />
VI. CONGENITAL CATARACT WITH HYDROCEPHALUS OR SKULL DEFORMITIES<br />
1. Autosomal cerebro-oculofacial skeletal<br />
syndrome (COFS) (an autosomal<br />
recessive syndrome characterised by<br />
microcephaly, joint contractures, typical<br />
facial features and failure to thrive)<br />
2. Autosomal recessive congenital<br />
infection-like syndrome (characterised<br />
by microcephaly, seizures and<br />
intracranial calcification)<br />
3. Autosomal dominant microcephaly, eye<br />
anomalies (congenital cataract and<br />
coloboma), short stature and mental<br />
retardation<br />
4. Autosomal recessive congenital<br />
cataract, mental retardation, motor,<br />
sensory and autonomic neuropathy<br />
5. Early onset Cockayne syndrome<br />
(thought to be <strong>the</strong> same condition as<br />
COFS)<br />
6. Cri du Chat syndrome (5p deletion)<br />
(microcephaly, mental retardation,<br />
round face and high pitched cry in<br />
infancy)<br />
7. Autosomal recessive cataract,<br />
microcephaly, renal tubular necrosis<br />
and encephalopathy with epilepsy<br />
8. Czeizal-Lowry syndrome (microcephaly,<br />
hip disease and mental retardation)<br />
9. Edwards syndrome (aniridia,<br />
microcephaly, small jaw and<br />
abnormalities of <strong>the</strong> nose)<br />
1. HEC syndrome: hydrocephalus, endocardial fibroelastosis, cataract<br />
2. Lerone; craniosynostsosis<br />
3. Martsolf’s syndrome<br />
4. Hydrocephalus and microphthalmia<br />
28<br />
March 9, 2001 OT<br />
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Module 3 Part 3<br />
differential diagnosis of a leukocoria is<br />
listed in Table 2. Suspicion may be aroused<br />
if a baby startles every time someone picks<br />
him/her up. In many cases, congenital<br />
cataracts are spotted by <strong>the</strong> health visitor<br />
at <strong>the</strong> six-week check.<br />
Assessment<br />
When a child presents with cataract, he/she<br />
must have a full ophthalmic examination.<br />
Visual acuity of each eye must be<br />
checked, as this will be a major factor in<br />
planning <strong>the</strong> management. In <strong>the</strong> verbal<br />
child, <strong>the</strong> Snellen chart, Sheridan–Gardner<br />
Singles and Kay Pictures are used to assess<br />
acuity. In <strong>the</strong> non or pre-verbal child, visual<br />
acuity is assessed using Cardiff Acuity Cards<br />
or Forced Choice Preferential Looking (FPL).<br />
It is important that <strong>the</strong> child’s ability to<br />
fixate a light source or torch is not used as<br />
an indicator of visual acuity, as a child with<br />
total cataracts significantly affecting visual<br />
acuity may fix and follow a light source<br />
normally, despite being blind to non<br />
luminous objects.<br />
Strabismus must be checked for and any<br />
co-existing amblyopia managed with<br />
occclusion <strong>the</strong>rapy.<br />
Slit lamp examination performed (a<br />
hand-held slit lamp is useful for examining<br />
very small children), and <strong>the</strong> laterality and<br />
density of <strong>the</strong> lens opacities assessed.<br />
All children should have <strong>the</strong>ir intraocular<br />
pressure checked in order to outrule coexisting<br />
glaucoma. This is best done using<br />
<strong>the</strong> hand-held air-puff tonometer.<br />
Before dilating <strong>the</strong> pupils, an afferent<br />
pupillary defect is excluded (<strong>the</strong>re may be a<br />
retinal or optic nerve lesion contributing to<br />
visual loss and cataract formation).<br />
Dilated fundoscopy is <strong>the</strong>n performed to<br />
ensure <strong>the</strong> retina and optic nerve is normal.<br />
If <strong>the</strong> cataract is so dense that no fundal<br />
details can be seen, B-scan ultrasonography<br />
can be carried out following referral in order<br />
to exclude a tumour or retinal detachment.<br />
The child <strong>the</strong>n has a full physical<br />
examination by a paediatrician, and has<br />
routine blood tests to test for congenital<br />
infection, galactosaemia, hypocalcaemia and<br />
hypoglycaemia. The urine is also checked for<br />
aminoaciduria which may be present in<br />
children with Lowe’s syndrome.<br />
In specialised centres, a visual evoked<br />
potential (VEP) is performed on very young<br />
babies in whom a visual acuity cannot be<br />
obtained, and in children with very dense<br />
cataracts, and in whom a possible coexisting<br />
visual pathway abnormality is<br />
suspected. The VEP gives <strong>the</strong> clinician<br />
information about <strong>the</strong> visual pathways, from<br />
<strong>the</strong> ganglion cell layer in <strong>the</strong> retina to <strong>the</strong><br />
occipital cortex.<br />
Management of<br />
paediatric cataract<br />
The management of cataract in <strong>the</strong> child<br />
www.optometry.co.uk<br />
Table 2 The differential diagnosis of leukocoria<br />
Retinoblastoma - malignant retinal tumour<br />
Cataract - lens opacity<br />
Toxoplasmosis - infection of retina or optic nerve with toxoplasma<br />
Toxocariasis - infection of retina or optic nerve with toxocara<br />
Retinal dysplasia - hereditary retinal maldevelopment<br />
Coats’ disease - congenital retinal telangiectasis and exudate<br />
Retinopathy of prematurity - retinal disease seen in some neonates born at less than 32<br />
weeks’ gestation<br />
Persistent hyperplastic primary vitreous<br />
Retinal astrocytoma - benign retinal tumour, can be associated with a systemic condition<br />
known as tuberous sclerosis<br />
High myopia with posterior staphyloma<br />
Eales disease - retinal vasculitis with haemorrhages<br />
Familial exudative vitreoretinopathy<br />
Extensive myelinated nerve fibres<br />
depends upon several factors: <strong>the</strong> child’s<br />
age; <strong>the</strong> extent of visual loss; whe<strong>the</strong>r or<br />
not <strong>the</strong>re is an associated illness or coexisting<br />
eye disease; and if <strong>the</strong> cataract<br />
affects one or both eyes.<br />
Surgery<br />
Intraocular lens (IOL) implantation<br />
is becoming an increasingly accepted<br />
procedure in young children and infants.<br />
Awareness of <strong>the</strong> rate of myopic shift which<br />
takes place in <strong>the</strong> developing eye, and <strong>the</strong><br />
use of biometry helps to predict appropriate<br />
IOL powers to try to ensure eventual<br />
emmetropia. However, final refraction is<br />
variable, such that emmetropia in adulthood<br />
cannot be guaranteed, as <strong>the</strong>re are<br />
insufficient long-term studies. Whe<strong>the</strong>r or<br />
not an IOL is inserted will depend on <strong>the</strong><br />
age of <strong>the</strong> child (recently in some centres<br />
IOLs are inserted into <strong>the</strong> eyes of babies as<br />
Table 3 The Great Ormond Street Occlusion Regime for Cataract<br />
Occlusion regime for bilateral cataract<br />
1. 0-1/2 octaves interocular difference<br />
in visual acuity – no occlusion<br />
2. 1-2 octaves interocular difference<br />
in visual acuity – 1-2 hours of<br />
occlusion of <strong>the</strong> better eye<br />
3. More than 2 octaves interocular<br />
difference in visual acuity – 2-4<br />
hours occlusion of <strong>the</strong> better eye<br />
4. If no improvement after stage 3 –<br />
full-time occlusion<br />
NB To be reviewed every 2 weeks<br />
* i.e. a child aged 2 months is patched for 2 hours a day,<br />
a 3 month old child for 3 hours/day etc.<br />
** The difference between each Cardiff Card is one octave<br />
young as four weeks of age), whe<strong>the</strong>r or<br />
not <strong>the</strong>re is any underlying ocular<br />
pathology in which IOL implantation is<br />
contra-indicated. In some instances, for<br />
example, in remote areas in less<br />
industrialised countries where it is unlikely<br />
that <strong>the</strong> child will be able to be brought<br />
back for regular follow-up, IOL implantation<br />
is not advisable.<br />
Bilateral cataracts<br />
Surgery is indicated when <strong>the</strong> cataracts are<br />
interfering with normal visual development.<br />
If <strong>the</strong> vision is good, <strong>the</strong>n surgery is not<br />
indicated, and <strong>the</strong> child has regular checkups.<br />
If <strong>the</strong>re is a significant deterioration<br />
in that child’s acuity at any stage, <strong>the</strong>n<br />
surgery is considered.<br />
If a child has bilateral dense cataracts,<br />
one eye is operated on followed by <strong>the</strong><br />
second eye one to two weeks later. The first<br />
Occlusion regime for unilateral cataract<br />
1. The phakic eye is occluded 1hour/day for<br />
each month of life* until 6 months of age.<br />
After 6 months occlusion depends on<br />
interocular difference (see 2-4 below)<br />
2. 0-1/2 octave interocular difference in visual<br />
acuity – 50% of waking hours<br />
3. 1-2 octaves interocular difference in visual<br />
acuity – 75% of waking hours<br />
4. More than 2 octaves interocular difference<br />
in visual acuity – 100% waking hours<br />
NB To be reviewed every 2 weeks<br />
29
ot<br />
eye is occluded post-operatively until <strong>the</strong><br />
second eye is operated on, to prevent<br />
amblyopia in <strong>the</strong> un-operated eye. In very<br />
young babies, an IOL is not inserted; <strong>the</strong>se<br />
babies are given contact lenses one to two<br />
weeks post operatively, and if contact lens<br />
are contra-indicated, <strong>the</strong> child is given<br />
aphakic spectacles. In some of <strong>the</strong>se<br />
children, an IOL may be inserted as a<br />
secondary procedure when <strong>the</strong> eye has<br />
grown. In general, an IOL is inserted into <strong>the</strong><br />
eye of older babies, and depending on <strong>the</strong><br />
age of <strong>the</strong> child, an IOL power is selected<br />
(according to <strong>the</strong> biometry) to make that eye<br />
appropriately hypermetropic, and hence allow<br />
for <strong>the</strong> myopic shift which takes place in <strong>the</strong><br />
developing eye; <strong>the</strong> aim is for emmetropia<br />
when <strong>the</strong> eye is fully grown.<br />
In <strong>the</strong> older child, for example a seven<br />
year old child with bilateral cataracts which<br />
are beginning to significantly interfere with<br />
visual acuity, <strong>the</strong> eye with <strong>the</strong> worst visual<br />
acuity is operated on, followed by <strong>the</strong><br />
second eye at least three to four weeks<br />
later.<br />
All surgery has potential complications,<br />
and <strong>the</strong> parents are warned about all<br />
possible complications pre-operatively (see<br />
later). Complications of lens aspiration and<br />
IOL implantation include post-operative<br />
uveitis, endophthalmitis, glaucoma and<br />
retinal detachment. In addition, <strong>the</strong>re is a<br />
greater than 90% risk that <strong>the</strong> posterior<br />
capsule will become thickened within in a<br />
year, which requires a fur<strong>the</strong>r procedure<br />
ei<strong>the</strong>r with laser or surgical capsulotomy to<br />
clear <strong>the</strong> visual axis and restore visual<br />
acuity to what it was initially postoperatively.<br />
In order to reduce <strong>the</strong> need for<br />
repeated general anaes<strong>the</strong>tics in order to<br />
perform laser and or surgery, a primary<br />
posterior capsulorhexis (and limited anterior<br />
vitrectomy) may be performed. This involves<br />
making a hole in <strong>the</strong> posterior capsule and<br />
removing a small amount of vitreous at <strong>the</strong><br />
time of <strong>the</strong> initial cataract surgery. This<br />
procedure significantly reduces <strong>the</strong><br />
development of posterior capsular<br />
opacification.<br />
Unilateral cataract<br />
In infants with unilateral cataract, <strong>the</strong><br />
cataract is most likely to be idiopathic and<br />
<strong>the</strong>re is usually no associated systemic<br />
disease. It is important not to confuse<br />
asymmetric bilateral cataract with unilateral<br />
cataract and, hence, careful slit lamp<br />
examination is essential in all children with<br />
cataract, as <strong>the</strong>re may be very subtle<br />
changes in one lens and dense cataract in<br />
<strong>the</strong> o<strong>the</strong>r.<br />
With regard to <strong>the</strong> management of<br />
unilateral cataract, <strong>the</strong> decision to operate<br />
depends on <strong>the</strong> density of <strong>the</strong> lens opacity,<br />
whe<strong>the</strong>r or not <strong>the</strong>re is any associated<br />
microphthalmos, and on <strong>the</strong> parent’s<br />
motivation to have <strong>the</strong> surgery performed.<br />
The parents need to be fully informed that<br />
surgery alone will not improve <strong>the</strong>ir child’s<br />
vision, and that <strong>the</strong> management of<br />
amblyopia is <strong>the</strong> key to a successful result.<br />
This entails optical correction and many<br />
hours of patching <strong>the</strong> normal eye every day<br />
(Table 3), which as one knows can be<br />
extremely difficult in a small infant or<br />
toddler, and needs to be maintained for<br />
many years. If occlusion is not performed<br />
<strong>the</strong> eye will remain densely amblyopic.<br />
It has been reported extensively in <strong>the</strong><br />
literature that children who have had<br />
surgery for bilateral cataracts have a much<br />
better visual outcome than children who<br />
have had surgery for unilateral cataract.<br />
Children with unilateral cataract need<br />
diligent occlusion <strong>the</strong>rapy of <strong>the</strong> unoperated<br />
eye toge<strong>the</strong>r with accurate optical<br />
correction of <strong>the</strong> operated eye to obtain a<br />
good visual result.<br />
Optical correction<br />
post-operatively<br />
Aphakia<br />
If <strong>the</strong> child has not had an IOL inserted and<br />
is <strong>the</strong>refore aphakic, contact lenses are<br />
fitted as soon as possible after surgery,<br />
regardless of age. This is usually done one<br />
to two weeks post-operatively. The baby is<br />
refracted and contact lenses fitted. Contact<br />
lenses are relatively safe 9 , <strong>the</strong>y can be used<br />
in combination with spectacles for near, and<br />
also to correct aniseikonia 10 . Rigid gas<br />
permeable contact lenses are most suitable<br />
for <strong>the</strong> management of aphakia, as <strong>the</strong>y<br />
have a wide range of powers, can correct<br />
astigmatism, and are relatively cheap. The<br />
disadvantages of contact lens wear are<br />
similar to those seen in adults, and include<br />
hypoxia and infective keratitis. Parents<br />
should be educated about contact lens<br />
hygiene and <strong>the</strong> signs and symptoms of<br />
possible complications associated with<br />
contact lens wear. All infants and<br />
children wearing contact lenses should be<br />
kept under constant review at a specialised<br />
unit.<br />
If contact lenses cannot be fitted (e.g.<br />
raised intraocular pressure, external eye<br />
disease, dry eye, severe microphthalmos or<br />
parents who are unable to cope with<br />
contacts), <strong>the</strong> child is given aphakic<br />
spectacles which have <strong>the</strong> advantage of<br />
increasing magnification and, <strong>the</strong>refore,<br />
enhancing <strong>the</strong> child’s acuity, and in can<br />
make <strong>the</strong> eyes of children with<br />
microphthalmia look slightly bigger.<br />
Pseudophakia<br />
To allow for <strong>the</strong> future growth of <strong>the</strong> infant<br />
eye (i.e <strong>the</strong> myopic shift) an IOL power less<br />
than that to result in emmetropia is used.<br />
This makes <strong>the</strong> child hypermetropic (<strong>the</strong><br />
amount of hypermetropia depends on <strong>the</strong><br />
age of <strong>the</strong> child), <strong>the</strong>n as <strong>the</strong> child’s eye<br />
grows emmetropia is approached. The child<br />
is <strong>the</strong>n given reading spectacles (and a<br />
distance prescription if required).<br />
Amblyopia management<br />
post-operatively<br />
The treatment of amblyopia is essential in<br />
order to obtain a successful outcome in<br />
patients who have had both unilateral and<br />
bilateral cataract surgery. Amblyopia is<br />
managed by giving <strong>the</strong> required optical<br />
correction and occluding <strong>the</strong> eye with better<br />
visual acuity. The occlusion is performed<br />
according to a standardised regime 11<br />
(Table 3). It is important to realise that<br />
excessive patching of <strong>the</strong> phakic eye in<br />
infants with unilateral aphakia may be<br />
associated with increased nystagmus and<br />
can have adverse effects on <strong>the</strong> phakic eye,<br />
hence it is imperative that <strong>the</strong>se children<br />
are reviewed every two weeks.<br />
Complications of<br />
cataract surgery<br />
Cataract surgery in <strong>the</strong> child and especially<br />
in babies has a higher incidence of<br />
complications than those seen after adult<br />
cataract surgery. This may be due to several<br />
reasons: cataract surgery is technically more<br />
difficult in <strong>the</strong> child’s eye, as <strong>the</strong> tissues are<br />
more elastic and behave differently to adult<br />
tissues; <strong>the</strong> child’s eye becomes more<br />
inflammed than an adult eye in response to<br />
an IOL; <strong>the</strong> very young child’s visual system<br />
is still developing and is <strong>the</strong>refore extremely<br />
sensitive to having a defocused image as is<br />
<strong>the</strong> case in aphakia; and a young child is<br />
less likely to fully comprehend <strong>the</strong><br />
importance of keeping dirty fingers away<br />
from <strong>the</strong> operated eye in <strong>the</strong> immediate<br />
post-operative period and, <strong>the</strong>refore, may<br />
rub <strong>the</strong> eye too vigorously resulting in<br />
wound dehisence and iris prolapse or<br />
infection.<br />
There have been many reports of <strong>the</strong><br />
visual outcome and complications of<br />
posterior chamber lens implantation in<br />
children 12-20 . The most common<br />
complications include:<br />
1. Glaucoma<br />
Glaucoma may arise in <strong>the</strong> first few weeks<br />
post-operatively, and may present as a<br />
watery eye with or without photophobia.<br />
The child is usually irritated or just “not his<br />
usual self”. Some children are asymptomatic,<br />
hence <strong>the</strong> importance of regular review with<br />
IOP checks post-operatively.<br />
Glaucoma may also occur as a late<br />
complication years later, and this type of<br />
glaucoma can be asymptomatic, <strong>the</strong>refore all<br />
children who have had cataract surgery<br />
should be followed up for life.<br />
2. Uveitis<br />
All children will develop a certain degree of<br />
uveitis post-cataract surgery. This is kept<br />
30<br />
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under control with frequent installation of<br />
topical steroids, which are given to all<br />
children routinely, and are eventually tailed<br />
off and discontinued. However, some<br />
children (approximately 30%) develop<br />
inflammation with fibrin formation. This<br />
accumulation of fibrin may result in<br />
secondary membrane formation blocking <strong>the</strong><br />
visual axis if not recognised and treated<br />
promptly.<br />
3. Irregular pupil<br />
An irregularly shaped pupil after cataract<br />
surgery may be due to: a) a strand of<br />
vitreous coming forwards from <strong>the</strong> vitreous<br />
cavity to <strong>the</strong> anterior chamber; b) damage<br />
to <strong>the</strong> iris during surgery; and c) iris<br />
prolapse, which may be due to accidental<br />
trauma to <strong>the</strong> eye post-operatively and<br />
requires urgent attention, as if left<br />
untreated that eye may become infected,<br />
and even <strong>the</strong> o<strong>the</strong>r eye may be at a risk<br />
from sympa<strong>the</strong>tic ophthalmia.<br />
4. Endophthalmitis<br />
Bacterial infection of <strong>the</strong> eye is a<br />
devastating complication which can occur in<br />
up to 0.4% of eyes after cataract surgery. It<br />
may occur early (i.e. within days to weeks)<br />
or late (months to years) post-operatively<br />
and presents with a sore painful red eye,<br />
and/or reduced vision, and requires urgent<br />
hospital admission and treatment.<br />
5. Posterior capsule opacification<br />
Posterior capsule opacification occurs in up<br />
to 90% of paediatric eyes after lens<br />
aspiration when <strong>the</strong> posterior capsule and<br />
anterior vitreous face are left intact. These<br />
children, having had a good visual result<br />
initially, later present with blurred vision.<br />
The thickened posterior capsule is seen<br />
using <strong>the</strong> slit lamp, or simply by examining<br />
<strong>the</strong> red reflex. These children are admitted<br />
as a day case and a posterior capsulotomy is<br />
performed. Older children can have laser<br />
treatment without a general anaes<strong>the</strong>tic. In<br />
some cases, <strong>the</strong> capsule thickens again and<br />
may require surgery to clear <strong>the</strong> visual axis.<br />
6. Retinal detachment<br />
Retinal detachment may occur years after<br />
cataract surgery, and present with reduced<br />
vision which may be preceeded by flashes<br />
and floaters.<br />
Conclusion<br />
Cataract in early childhood, if not picked up<br />
early and managed appropriately, can have<br />
devastating visual consequences. Treatment<br />
may not always be surgical, and parents<br />
need to be aware that those children who<br />
do require surgery will also need optical<br />
correction and, in many cases, many hours<br />
of occlusion <strong>the</strong>rapy for <strong>the</strong> treatment of<br />
amblyopia. It is also essential to be aware<br />
that <strong>the</strong>re are many syndromes and systemic<br />
disorders which may be associated with<br />
congential cataract and that may have<br />
implications for <strong>the</strong> child’s health.<br />
Acknowledegemt<br />
Figures 1 and 2 reproduced with kind<br />
permission from Consultant<br />
Ophthalmologist, Nicholas Phelps Brown.<br />
References<br />
1. Scott, M.H., Hejtmancik, J.F.,<br />
Wozencraft, L.A. et al (1994)<br />
“Autosomal dominant congenital<br />
cataract. Intraocular phenotypic<br />
variability”. Ophthalmology 101: 866-71.<br />
2. Forsius, H., Arentz-Grastvedt, B. and<br />
Eriksson, A.W. (1992) “Juvenile cataract<br />
with autosomal recessive inheritance. A<br />
study from <strong>the</strong> Aland Islands, Finland”.<br />
Acta. Ophthalmol. 70: 26-32.<br />
3. Stambolian, D. (1988) “Galactose and<br />
cataract”. Surv. Ophthalmol. 32: 33-49.<br />
4. Merin, S. and Crawford, J. (1971)<br />
“Hypoglycaemia and infantile cataract”.<br />
Arch. Ophthalmol. 86: 495-8.<br />
5. Hochman, H.I. and Mejlszenkier, J.D.<br />
(1977) “Cataracts and pseudotumour<br />
ceribri in an infant with vitamin D<br />
deficiency rickets”. J. Pediatr. 90: 252-4.<br />
6. Letson, R.D. and Desnick, R.J. (1978)<br />
“Punctate lenticular opacities in type II<br />
mannosidosis”. Am. J. Ophthalmol. 85:<br />
218-24.<br />
7. Henk, J.M., Whitelocke, R.A.F.,<br />
Warrington, A.P. et al (1993) “Radiation<br />
dose to <strong>the</strong> lens and cataract<br />
formation”. Int. J. Radiat. Oncol. Biol.<br />
Phys. 25: 815-20.<br />
8. Brocklebank, J.T., Harcourt, R.B.,<br />
Meadow, S.R. (1982) “Corticosteroid<br />
induced cataracts in idiopathic<br />
nephrotic syndrome”. Arch. Dis. Child.<br />
53: 30-4.<br />
9. Amaya, L., Speedwell, L. and Taylor,<br />
D.S.I. (1990) “Contact lenses for infant<br />
aphakia”. Br. J. Ophthalmol. 74: 150-4.<br />
10. Enoch, J.M. and Hamer, R.D. (1983)<br />
“Image size correction of <strong>the</strong> unilateral<br />
aphakic infant”. Ophthalmic Paediatr.<br />
Genet. 2: 153-65.<br />
11. Tayloe, D.S.I., The Doyne Lecture.<br />
(1998) “Congenital cataract: <strong>the</strong><br />
history, <strong>the</strong> nature and <strong>the</strong> practice”.<br />
Eye 12: 9-36.<br />
12. Thouvenin, D., Lesueur, L. and Arne,<br />
J.L. (1995) “Implantation<br />
Intercapsulaire dans les cataractes de<br />
l’Enfant. Etude de 87 cas et<br />
comparaison a 88 cas sans<br />
implantation”. J. Franc. Ophthalmol.<br />
18: 678-687.<br />
13. Knight-Nanan, D., O’Keefe, M. and<br />
Bowell, R. (1994) “Outcome and<br />
complications of intraocular lenses in<br />
children with cataract”. J. Cat. Ref.<br />
Surg. 22: 730-736.<br />
14. Brady, K.M., Atkinson, C.S., Kilty, L.A.<br />
and Hiles, D.A. (1995) “Cataract<br />
surgery and intraocular lens<br />
implantation in children”. Am. J.<br />
Ophthalmol. 120: 1-9.<br />
15. Sinskey, R.M., Stoppel, J.O. and Amin,<br />
P. (1993) “Long-term results of<br />
intraocular lens implantation in<br />
pediatric patients”. J. Cat. Ref. Surg.<br />
19: 405-408.<br />
16. Zwaan, J., Mullaney, P.B., Awad, A., Al-<br />
Mesfer, S. and Wheeler, D.T. (1998)<br />
“Pediatric Intraocular lens<br />
implantation: Surgical results and<br />
complications in more than 300<br />
patients”. Ophthalmology 105: 112-<br />
119.<br />
17. Gimbel, H.V., Basti, S., Ferensowicz, M.<br />
and DeBroff, B.M. (1997) “Results of<br />
bilateral cataract extraction with<br />
posterior chamber intraocular lens<br />
implantation in children”.<br />
Ophthalmology 104: 1737-1743.<br />
18. Crouch, E.R., Pressman, S.H. and<br />
Crouch, E.R. (1995) “Posterior chamber<br />
intraocular lenses: long term results in<br />
pediatric cataract patients”. J. Pediatr.<br />
Ophthalmol. Strabismus 32: 210-218.<br />
19. Burke, J.P., Wilshaw, H.E. and Young,<br />
J.D.H. (1989) “Intraocular lens<br />
implants for uniocular cataracts in<br />
children”. Br. J. Ophthalmol. 73: 860-<br />
865.<br />
20. Churchill, A.J., Noble, B.A., Etchells,<br />
D.E. and George, N.J. (1995) “Factors<br />
affecting visual outcome in children<br />
following uniocular traumatic cataract”.<br />
Eye 9: 285-291.<br />
ABOUT THE AUTHOR<br />
Lorraine Cassidy is Locum Consultant Ophthalmologist at Great Ormond Street Hospital for<br />
Children, and at St Helliers and Sutton Hospitals, Surrey. She has a special interest in<br />
paediatric ophthalmology and trained with David Taylor and Isabelle Russell-Eggitt at Great<br />
Ormond Street.<br />
www.optometry.co.uk 31
ot<br />
Multiple choice questions<br />
Paediatric cataract MCQs<br />
1. Hypoglycaemia in an infant is most likely<br />
to give rise to all of <strong>the</strong> following except:<br />
a. cataract<br />
b. convulsions<br />
c. permanent brain damage<br />
d. skeletal dysplasia<br />
2. ‘Oil droplet’ cataracts are<br />
associated with which disorder?<br />
a. Galactosaemia<br />
b. Mannosidosis<br />
c. Trauma<br />
d. Glucose-6-phosphate dehydrogenase<br />
deficiency<br />
3. Which one of <strong>the</strong> following statements<br />
is incorrect regarding cataract?<br />
a. Short stature may be associated with<br />
cataract<br />
b. Cataracts which result from <strong>the</strong> metabolic<br />
abnormality known as galactosaemia can be<br />
reversible<br />
c. Congenital cataracts are most easily seen by<br />
looking at <strong>the</strong> red reflex in <strong>the</strong> first week of<br />
life<br />
d. In babies with dense congenital cataract it<br />
is best to wait until <strong>the</strong> child is at least five<br />
years old before considering surgery<br />
4. Which one of <strong>the</strong> following statements is<br />
correct regarding cataract?<br />
a. Contact lenses are contraindicated in<br />
children under six weeks old<br />
b. Leukocoria is always a benign ocular sign<br />
which warrants routine referral<br />
c. Steroid induced cataracts are reversible on<br />
discontinuing steroid <strong>the</strong>rapy<br />
d. Microphthalmos may be a contra-indication<br />
of contact lens wear<br />
Please note <strong>the</strong>re is only ONE correct answer<br />
5. Steroid induced cataracts are typically:<br />
a. lamellar<br />
b. anterior polar<br />
c. cortical<br />
d. posterior subcapsular<br />
6. Which one of <strong>the</strong> following<br />
statements is correct?<br />
a. Children who have had surgery for unilateral<br />
cataract have a much better visual outcome<br />
than children who have had surgery for<br />
bilateral cataracts<br />
b. When a very young infant is having<br />
an IOL implanted, <strong>the</strong> power of <strong>the</strong><br />
IOL is calculated to make <strong>the</strong> child<br />
myopic<br />
c. Management of ambyopia is essential in<br />
improving visual function<br />
d. Bilateral cataracts are often operated in<br />
simultaneously<br />
7. Complications of cataract surgery in <strong>the</strong><br />
child include all of <strong>the</strong> following except:<br />
a. glaucoma<br />
b. uveitis<br />
c. retinal detachment<br />
d. diabetes<br />
8. A child who presents with a watery<br />
eye one or two weeks post cataract<br />
surgery is most likely to have:<br />
a. conjunctivitis<br />
b. a blocked tear duct<br />
c. glaucoma<br />
d. posterior capsular opacification<br />
9. Endophthalmitis occurs in what<br />
proportion of eyes following<br />
cataract removal?<br />
a. 0.4%<br />
b. 1%<br />
c. 0.2%<br />
d. 10%<br />
10. Posterior capsular opacification occurs in<br />
what proportion of eyes following<br />
cataract removal?<br />
a. 50%<br />
b. 60%<br />
c. 70%<br />
d. 90%<br />
11. According to <strong>the</strong> Great Ormond Street<br />
Occlusion Regime for Cataract, a child<br />
with bilateral cataract showing 1-2<br />
octaves interocular difference in visual<br />
acuity will be occluded for what period of<br />
time?<br />
a. One to two hours of <strong>the</strong> better eye<br />
b. No occlusion<br />
c. Two to four hours of <strong>the</strong> better eye<br />
d. Full-time occlusion<br />
12. According to <strong>the</strong> Great Ormond Street<br />
Occlusion regime for cataract, a child<br />
with a unilateral cataract showing more<br />
than 2 octaves interocular difference in<br />
visual acuity will be occluded for what<br />
period of time?<br />
a. 50% of waking hours<br />
b. 1 hour/day for each month of life<br />
c. 75% of waking hours<br />
d. 100% of waking hours<br />
An answer return form is included in this issue.<br />
It should be completed and returned to:<br />
CPD Initiatives (c2983d),<br />
OT, Victoria House, 178–180 Fleet Road, Fleet,<br />
Hampshire, GU13 8DA by April 4, 2001.<br />
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Module 3 Part 3<br />
Multiple choice answers - The epidemology of cataract<br />
Here are <strong>the</strong> correct answers to CPD module 3 part 2, which appeared in our February 9 issue.<br />
1. The UK government is aiming for how<br />
many cataract operations per year in<br />
its Action on Cataracts initiative?<br />
a. 175,000<br />
b. 250,000<br />
c. 1,500,000<br />
d. 30 million<br />
b is <strong>the</strong> correct answer<br />
The Department of Health, in its initiative<br />
Action on Cataracts, aims to increase<br />
cataract surgery from <strong>the</strong> current annual<br />
estimate of 175,000 cases to 250,000<br />
within three years, mostly by improving<br />
efficiency. There are 1,500,000 cataract<br />
surgeries a year in <strong>the</strong> United States, and<br />
it is estimated that <strong>the</strong>re are 38 million<br />
people blind from cataract in <strong>the</strong> world.<br />
2. Which one of <strong>the</strong> following<br />
statements is correct?<br />
a. Studies investigating cataract are easy to<br />
compare<br />
b. Cataract grading methods should not be<br />
sensitive to change<br />
c. Photographic grading systems are most<br />
reproducible and reliable<br />
d. Lens opacities usually regress in<br />
epidemiological studies<br />
c is <strong>the</strong> correct answer<br />
There have been many different cataract<br />
grading systems used, making comparison<br />
of different studies difficult. In order to<br />
detect change, cataract grading systems<br />
must be sensitive to detect that change,<br />
which is why many systems have been<br />
decimalised from simple 0-5 grading<br />
points, to 0.1, 0.2 etc, up to 5.0.<br />
Photographic systems are most<br />
reproducible and reliable as <strong>the</strong>re is ‘hard<br />
evidence’ to compare, compared to<br />
subjective systems. Lens opacities do not<br />
regress, and so studies with significant<br />
regression suggest that <strong>the</strong> grading of<br />
cataract was not reliable.<br />
3. Which one of <strong>the</strong> following<br />
statements is correct?<br />
a. Genes are important in congenital cataract<br />
b. The genes responsible for age-related<br />
cataract have been identified<br />
c. Environmental factors have been shown to<br />
be more important than genetic make-up<br />
d. Genes are unlikely to be important in agerelated<br />
cataract<br />
a is <strong>the</strong> correct answer<br />
The Twin Eye Study has shown that genes<br />
are important in age-related cataract, with<br />
a heritability of 48%. Environment only<br />
contributed to 14% of <strong>the</strong> variance,<br />
although this may still be important in<br />
individuals with particular genetic defects.<br />
The gene mutations involved in agerelated<br />
cataract are still unknown, but<br />
many mutations have been identified in<br />
congenital cataracts, which are often<br />
familial.<br />
4. The heritability of nuclear cataract<br />
has been reported as:<br />
a. 12%<br />
b. 38%<br />
c. 48%<br />
d. 66%<br />
c is <strong>the</strong> correct answer<br />
The heritability of nuclear cataract in <strong>the</strong><br />
Twin Eye Study was 48%.<br />
5. The prevalence of nuclear cataract:<br />
a. is greater in women than men<br />
b. is greater in men than women<br />
c. is <strong>the</strong> same in <strong>the</strong> two sexes<br />
d. is greatest in <strong>the</strong> 65-74 age group<br />
a is <strong>the</strong> correct answer<br />
The prevalence of nuclear cataract is greater<br />
in women than men, as it is for cortical<br />
cataract. The reasons for this are not<br />
known. The prevalence of cataract is also<br />
strongly age-related, so that cataract is<br />
more common in those aged over 75 than<br />
those aged 65-74 years.<br />
6. In patients over <strong>the</strong> age of 75 years:<br />
a. posterior subcapsular cataract is <strong>the</strong><br />
commonest cataract type<br />
b. cortical cataract is present in over 40%<br />
c. nuclear cataract is rare<br />
d. diabetes is <strong>the</strong> commonest cause of lens<br />
opacities<br />
b is <strong>the</strong> correct answer<br />
Cortical cataract is present in over 40% of<br />
individuals over <strong>the</strong> age of 75 years, and<br />
significant nuclear cataract in at least 50%.<br />
www.optometry.co.uk 33
ot<br />
Multiple choice answers - continued<br />
Posterior subcapsular cataract is least<br />
common, but is still present in over 10% of<br />
those aged over 75. Although diabetes is a<br />
risk factor for <strong>the</strong> development of cataract,<br />
it is only present in around 2% of <strong>the</strong><br />
population and so is not <strong>the</strong> most important<br />
cause of cataract in this age group.<br />
7. Which one of <strong>the</strong> following has NOT<br />
been shown to be associated with<br />
cataract formation?<br />
a. High myopia<br />
b. Marfan’s syndrome<br />
c. Myotonic dystrophy<br />
d. Myas<strong>the</strong>nia gravis<br />
d is <strong>the</strong> correct answer<br />
Cataract has been associated with various<br />
systemic conditions, such as connective<br />
tissue disorders (myotonic dystrophy which<br />
causes ‘Christmas tree’ cataracts) and<br />
Marfan’s syndrome (also associated with lens<br />
dislocation). It is also associated with<br />
intraocular diseases such as uveitis, and<br />
high myopia is a risk factor. Myas<strong>the</strong>nia<br />
gravis, a myopathy causing fatiguable ptosis<br />
and reduced eye movements, is not<br />
associated with cataract itself. (However,<br />
patients may require sustained oral<br />
steroids for its treatment and may<br />
develop cataracts as a result.)<br />
8. Which one of <strong>the</strong> following is<br />
associated with cortical<br />
cataract?<br />
a. Steroid intake<br />
b. Smoking<br />
c. Vitamin D<br />
d. Ultraviolet light<br />
d is <strong>the</strong> correct answer<br />
Cortical cataract is associated with<br />
increasing age, and is more common in<br />
women and people of Afro Caribbean<br />
descent. Ultraviolet light, in <strong>the</strong> form of<br />
sunlight, has been assoiciated with cortical<br />
cataract also. Smoking is not associated<br />
with cortical cataract, and while steroids<br />
may increase <strong>the</strong> risk of all types of<br />
cataract, <strong>the</strong>y are particularly associated<br />
with posterior subcapsular cataract.<br />
9. The London City Eye Study<br />
demonstrated that:<br />
a. alcohol may be related to cataract<br />
b. ultraviolet light exposure is related to<br />
posterior subcapsular cataract<br />
c. smoking is associated with cataract<br />
d. vitamin C is protective in cataract<br />
c is <strong>the</strong> correct answer<br />
The London City Eye Study suggested<br />
smoking was associated with cataract, and<br />
found a greater risk in smokers compared to<br />
ex-smokers, and <strong>the</strong> ex-smokers carried a<br />
greater risk than <strong>the</strong> non-smokers,<br />
suggesting a causal link.<br />
10. Which one of <strong>the</strong> following statements is<br />
incorrect regarding cigarette smoking?<br />
a. It is related to <strong>the</strong> development<br />
of nuclear cataract<br />
b. It is related to <strong>the</strong> development<br />
of posterior subcapsular cataract<br />
c. Ex-smokers have an increased risk of<br />
developing cataract compared<br />
to non-smokers<br />
d. It is related to <strong>the</strong> development<br />
of cortical cataract<br />
d is <strong>the</strong> correct answer<br />
Smoking has been particularly associated<br />
with nuclear cataract, although some<br />
studies have suggested it may also be<br />
associated with posterior subcapsular<br />
cataract. It has not been associated with<br />
cortical cataract, however. As above, <strong>the</strong><br />
London City Eye Study did suggest that exsmokers<br />
carried a greater risk than nonsmokers.<br />
11. Hypertension may be related<br />
to which type of cataract:<br />
a. nuclear<br />
b. cortical<br />
c. posterior subcapsular<br />
d. congenital<br />
c is <strong>the</strong> correct answer<br />
No consistent evidence has linked cataract<br />
to hypertension, although <strong>the</strong> Beaver Dam<br />
Eye Study did suggest that hypertensive<br />
patients were slightly more likely to have<br />
posterior subcapsular cataract than those<br />
without hypertension.<br />
12. Which one of <strong>the</strong> following statements<br />
is correct regarding cataract?<br />
a. 20 million people will be blind due to<br />
cataract by 2020<br />
b. Cataract is more common in men compared<br />
to women<br />
c. Tall height may be associated with cataract<br />
d. Diarrhoea may be associated with cataract<br />
d is <strong>the</strong> correct answer<br />
Case-control studies have suggested that<br />
severe diarrhoeal disease may be associated<br />
with cataract in later life. Low height or<br />
body weight may also be associated<br />
with cataract, and may reflect early<br />
malnutrition.<br />
34<br />
March 9, 2001 OT<br />
www.optometry.co.uk