Bitten by Ophthalmology Professor Helen Danesh-Meyer University of Auckland

5 Keys steps for assessment of optic nerve function VA Colour Vision Relative afferent pupillary defect Visual Field Optic Nerve

1. Visual Acuity Best Corrected Pinhole

Papillo-macular bundle

GlaucomaGlaucoma A collective term for group of potentially blinding ocular conditions Characterised by peripheral visual field loss and characteristic changes to the optic nerve head Can be: –primary (occur by themselves), or –secondary (other ocular condition causes it)

Primary Open Angle Glaucoma Adult onset (> 40yrs) Angle normal and open Higher IOP greater risk Glaucomatous optic nerve head damage Visual Field loss Normal Glaucoma cup disc cup disc c/d = 0.3 c/d = 0.8

Open Angle Glaucoma Asymptomatic Genetic Visual loss is irreversible Most common cause of preventable blindness Treatment is lifelong

2. Colour vision Optic nerve disease has decreased colour out of proportion to VA. Red desaturation classic for compressive optic neuropathies Tests: –Ishihara –Red target

3. Relative Afferent Pupillary Defect

Objective sign of optic nerve compromise Can be used to monitor progression Provides a comparison of the two optic nerves

Relative Afferent Pupillary Defect (RAPD) Test in dim room with pt looking at the distance Use bright source of light about 30cm from pt’s eyes Swing light b/w the eyes (2-3 sec on each eye) Make your decision within 2-3 swings

ObserveObserve Photopic illuminationScotopic illumination

Light responses Consensual responseDirect response

Light responses Direct responseConsensual response

Abnormal response Right Relative Afferent Pupillary Defect

Circumstances when RAPD assessment difficult Both pupils dilated Dark irides Elderly- small constricted pupils Damage to iris by surgery (cataract) Presybopic examiner

Surrogate Tests for RAPD Brightness sense Red perception

Brightness sense Test in dim room with pt looking directly at the light Use bright source of light Ask: 1.Is light equally bright in both eyes? 2.If light is 100% bright in this eye (or worth 100 dollars) then how many percent (or how many dollars) is it in the other eye?

4. Visual Field Assessment

Anatomy of visual pathway Right eyeLeft eye Temporal Nasal

Anatomy of visual pathway Modified from Kahle W.Frotscher M: Color Atlas and Textbook of Human Anatomy. 5 th ed. Stuttgart: Thieme. Vol.3 p.355, 2003 Optic nerve Nasal retina Optic chiasm Optic tract Optic radiation Temporal retina Lateral geniculate body Striate cortex

Case 2 24 yr old male ~ 1 yr Hx of headaches, worse last 2-3/12 Examination: 6/6 OD6/6 OS No RAPDPallor + CT head – pituitary adenoma

Visual Fields – 2/7 pre-op 39 year old: 6/6 VA both eyes

Localising lesions by type of visual field defect Left eye Right eye

Visual Acuity Pupil Testing Visual Fields Colour vision Fundus Examination