Bitten by Ophthalmology Professor Helen DaneshMeyer University of

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

Glaucoma • 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 (> 40 yrs) • Angle normal and open c/d = 0. 3 cup Normal disc • Higher IOP greater risk Glaucoma • Glaucomatous optic nerve head damage c/d = 0. 8 • Visual Field loss cup disc

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

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 30 cm from pt’s eyes • Swing light b/w the eyes (2 -3 sec on each eye) • Make your decision within 2 -3 swings

Observe Photopic Scotopic illumination

Light responses Direct response Consensual response

Light responses Consensual response Direct 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 eye Temporal Left eye Nasal Temporal

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

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

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

Visual Acuity Pupil Testing Colour vision Visual Fields Fundus Examination