3 - Decreased Vision Evaluation Flashcards
1
Q
Three crucial history points in patient with decreased vision?
A
- Unilateral vs Bilateral
- Unilateral — prechaism
- Bilateral — bilateral ocular, chiasm, post-chiasm, systemic
- Patient with R homonymous hemianopia may mistake temporal VF defect as problem with vision of R eye only
- Time course
- Days to weeks — inflammatory
- Acute — ischemic
- Months to years — toxic, nutritional, compressive, glaucoma (May be noticed acutely however)
- Need to distinguish between sudden vision loss and sudden awareness of vision loss
- Associated symptoms
2
Q
If CDVA < 20/400, next test?
A
- Should quantify CDVA using E optotype chart. Record distance at which patient able to discern letter orientation (“5/200” in meters). This provides more accurate and reproducible measurement than CF method.
3
Q
VA examination points to note?
A
- Presence of eccentric fixation (possible central scotoma).
- Tendency to read half of chart (hemianopic field defect).
- Improvement in CDVA when reading single optotypes (may suggest amblyopia)
4
Q
Ishihara pseudoisochromatic color plates
A
- Designed to detect red-green color deficiencies and may also identify acquired dyschromatopsias though it may miss mild cases
5
Q
Best color discrimination test?
A
- Farnsworth-Munsell 100-hue test which uses 85 colored discs BUT takes time to test and score
6
Q
Testing for APD
A
- When light shone in eye with impaired afferent conduction — pupillary constriction in both eyes is slower and smaller in amplitude
- Absence of APD — no optic neuropathy or bilateral ON involvement
- RAPD may be seen from substantial retinal disease like CRAO or RD
- Chiasmal lesions may produce RAPD secondary to asymmetric ON involvement
- Unilateral Optic Tract lesion — RAPD on side of temporal VF defect due to the fact that crossed fibers (53%) greater than uncrossed fibers (47%)
- Rare cases RAPD — cataract, VH, amlyopia
7
Q
Difficult RAPD testing?
A
- Dark irides, sluggish pupils, dilated pupils, miotic pupils may make RAPD eliciting difficult THUS use brightness sense testing or color intensity with red perception testing with red cap top
8
Q
ONH Pallor 2/2?
A
- Damage to RGC anywhere from RGC cell body to synapse at LGN
- Takes 4-6 weeks for pallor to develop
- Mild forms of ON pallor may be difficult to detect
- Evaluation of capillary net, network of fine blood vessels on ONH may be helpful — net becomes thin or absent in early atrophy even when pallor still very mild
- True temporal pallor must be distingushed from pallor of ONH in pseudophakic eye — if only 1 eye pseudophakic difficulty of comparing ONH pallor in 2 eyes challenging
9
Q
Rake defects
A
- When viewed with red-free filter, fine defects appear as dark bands among normal striations
10
Q
ONH edema
A
- ICP, local mechanical compression, ischemia, inflammation
- May see:
- blurring of margins
- elevation of ONH
- peripapillary RNFL opacification
- hyperemia and dilation of ONH surface capillary net
- retinal venous dilation and tortuosity
- peripapillary hemorrhages, exudates, CWS
- retinal/choroidal folds
- macular edema
11
Q
Confrontational Testing
A
- Only a screening test and not a replacement for perimetry
- Accuracy depends on density of VF defect
- Single test with best specificity and sensitivity is kinetic testing with a red target
12
Q
Extinction
A
- Inability to see a target in an affected hemifield ONLY during simultaneous stimulation of both hemifields (target presented only in affected hemifield may be seen) — visual neglect characteristic of parietal lobe lesion
13
Q
Amsler grid testing
A
- Screens central 20° of visual field (10° from fixation)
- Use near vision correction
- Low sensitivity
14
Q
Kinetic Perimetry
A
- Goldmann perimetry
- Can evaluate entire VF
- Stimuli of varying sizes and stimuli used from peripheral to central location
- Typically 2 or 3 isopters plotted
15
Q
Automated Static Perimetry
A
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