Equine Lens Problems - University of Florida

•The lens sits in thepatellar fossa of thevitreous.•The horse has weak accommodation (< 2.0 D) to maintain afocussed retinal image.

21/4/2009Cigoto – Segmentación - Blastulación –Gástrulación – OrganogénesisImagen real de una blástula4

ERU cataract/synechia

Matt Stevens

• Multifocal lens with horizontal pupil• Zones of optical discontinuity

Nuclear cataract

Immature cataract

Morgan horse hereditary nuclear cataract

Whip injury

Therapy for Uveitic Cataracts• Medical: Oral aspirin might delay cataractformation in a few ERU horses• 10 mg/kg q24h• Surgery: Only chance for vision– Not easy– Client must be educated about the risks andbenefits, and must have realistic expectations!

• healthy foals(Rhodococcus free) andadult horses• no uveitis• visual impairment• the personality to toleratetopical therapy• Brisk PLRs and a dazzleindicate a functionalretina.• US (RDs)• ERG (esp Appaloosas)Cataract PatientCriteria

• ERG: Dark adapt 20minutes

ERG

Light Stimulus

US: mature cataract

US: posterior lens capsule rupture

RD: “seagull” sign

Lens fragments lying on retina.

“Phaco”

Phaco Surgical Procedure• Paralysis with atracurium• Scleral tunnel w/cautery• CCC• Standard SA needle; 15 mm• Horse needle is 23 mm• Machines• Hylartin-V viscoelastic• Mean phaco time: 10:05minutes (range 4:32 – 15:49)

Medications Postoperatively• Sulfas systemically for 5 days• Banamine (+/- omeprazole): several weeks• Topical Atropine: 2 weeks• Topical antibiotics: 2 weeks• Topical Prednisolone acetate: 1-3 months• Hospital stay: avg 8 days, range 3-15 days

Phacoemulsification.• Success rate ~ 83-98%initially in horses.– Declines rapidly with timedue to capsuler scarringand persistent uveitis– 49% at one month (OSU)– 44% at one year (TAMU)– 39% at 18 months (UF)• Surgery is easiest in foalsand yearlings.

• Complications: corneal ulcers, persistent corneal edemaand ulcers, glaucoma, hyphema, and infectiousendophthalmitis– Vision is functional but the aphakic horse should be hyperopic“far-sighted”• The aphakic equine globe is +9.9 D hyperopic (20/1200).– A 25 D IOL = +8.0 D

IOL

Intraocular Lenses (IOLs) in Horses

Knotty06

Lens Luxation in HorsesAnterior lens luxation

Aphakic crescentTrauma from cross ties

Lens subluxation4 wks later

Lens Cysts