1 Visual Acuity Testing CMSft. Lynn Lawrence, CPOT ... - SECO 2011
1 Visual Acuity Testing CMSft. Lynn Lawrence, CPOT ... - SECO 2011 1 Visual Acuity Testing CMSft. Lynn Lawrence, CPOT ... - SECO 2011
Contrast Sensitivity � In the “real world” the eye responds to levels of luminance of a target and its background. � Snellen acuity charting does not reflect how the individual can visually function when: • driving at night • reading in poor light • in direct sunlight Contrast Sensitivity Testing � Sine wave gratings • Electronically on a television screen • Graphically on a chart � Pelli-Robson Chart • Common method of measuring contrast sensitivity • Letter tests usually give better results than sine gratings Infants �� Fix & Follow (F&F) �� Central, Steady, Maintained (CSM) �� Response to Light (+/-) � Opticokinetic Nystagmus Drum (OKN) � Preferential viewing �� VEP Pre-School Children � Allen picture cards � Tumbling E’s � HOTV 4
Elderly Patients �� Testing the vision of an elderly patient may require more time due to medical conditions such as: • Dry eye • Macular degeneration • Floaters • Decreased contrast sensitivity • Hard of hearing • Confusion Amblyopic Patients �� Watch carefully for peeking �� Test amblyopic eye first �� Crowding Phenomenon: single optotype Patients with Nystagmus � Do not occlude � Use a high plus lens to fog the eye not being checked Listen to What the Patient Says � “I can only see the letters on the left/right side.” � Important to “push” the patient to the next line to determine if a pattern is developing. Factors Other Than Disease That Can Affect Visual Acuity � Uncorrected ametropia � Eccentric viewing � Decreased contrast � Large (> 6mm) or small (< 2mm) pupils � Young or old age � Adults • Monetary Gain • Attention • Psychiatric Condition � Children • Want glasses • Reaction to stress/emotional problem • Attention Psychological Factors That May Affect Test Results � Attention 5
- Page 1 and 2: Visual Acuity Testing CMSft. Lynn L
- Page 3: � Each row has 5 letters � Read
Contrast Sensitivity<br />
� In the “real world” the eye responds to levels of luminance of a target and its<br />
background.<br />
� Snellen acuity charting does not reflect how the individual can visually function<br />
when:<br />
• driving at night<br />
• reading in poor light<br />
• in direct sunlight<br />
Contrast Sensitivity <strong>Testing</strong><br />
� Sine wave gratings<br />
• Electronically on a television screen<br />
• Graphically on a chart<br />
� Pelli-Robson Chart<br />
• Common method of measuring contrast sensitivity<br />
• Letter tests usually give better results than sine gratings<br />
Infants<br />
�� Fix & Follow (F&F)<br />
�� Central, Steady, Maintained (CSM)<br />
�� Response to Light (+/-)<br />
� Opticokinetic Nystagmus Drum (OKN)<br />
� Preferential viewing<br />
�� VEP<br />
Pre-School Children<br />
� Allen picture cards<br />
� Tumbling E’s<br />
� HOTV<br />
4
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