Download Visual System - University of Auckland

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
Normal
• Adult onset (> 40yrs)
• Angle normal and open
c/d = 0.3
cup
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 30cm 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
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. 5th 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 +
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