VISFUN: SEMINARS (2) - Ageing Vision, ARC Flashcards
What are the major eye conditions over 40yo [Ageing Vision #1]
Presbyopia Glaucoma AMD Cataract DR
What are the major eye conditions over 60yo [Ageing Vision #1]
Glaucoma
Cataract
AMD
DR
What should an Optometrist consider when dealing with an older patient? [Ageing Vision #1]
- ability to live independently
- quality of life + operation necessity (shorter benefit)
- disability
- driving
How does ageing affect eyelids? [Ageing Vision #2]
- gradual tissue atrophy (redundant skin folds/wrinkles)
- loss of structural support (tarsus, canthal tendons, orbicularis muscle)
- — orbital fat prolapse, eyelid malposition, blepharoptosis, tearing
- ectropia/entropia
How does ageing affect horizontal eye fissure? [Ageing Vision #2]
Decreases by about 10%
How does ageing affect cornea? [Ageing Vision #2]
- increased epithelial permeability
- changed integrin subunit distribution
- reduced phagocytic ability of granulocytes (in response to infection)
How does ageing affect size/density of corneal layers? [Ageing Vision #2]
- thickened epithelial basement membrane
- decrease nerve density
- decreased stromal cell density
- Thickened Descement’s membrane + appearance of hassall-henie bodies
- Decreased number of corneal endothelial cells
How does ageing affect TM and Iris? [Ageing Vision #2]
TM: increased pigmentation, increased aq. outflow resistance
Iris: decreased pigmentation, less refractive + more difficult to dilate, decreased size
How does ageing affect crystalline lens? [Ageing Vision #2]
- decreased lens optical density
- nuclear sclerosis (lens hardening)
- more yellow pigment
- decreased elasticity of capsule
- decreased fibre compactness
How does ageing affect the vitreous? [Ageing Vision #2]
- harmless floaters
- condensation of vitreous gel
- increased mobility of fibrillary structures
- lacunae (optically empty spaces)
- vitreous body shrinkage
How does ageing affect the retina? [Ageing Vision #2]
- thickened ILM (internal limiting membrane)
- neuronal cell loss + degradation
- gliosis (in peripheral retina)
- disorganisation of ora serrata and RPE
- reduced nuclei in ONL
- corpora amylacea
- loss of rods
How does ageing affect retinal vessels? [Ageing Vision #2]
- loss of cellularity in peripheral capillaries
- attachment of ILM to peripheral vascular arcades
- reduced number of capillaries around fovea
- arteriosclerotic changes
How does ageing affect dark adaptation? [Ageing Vision #3]
Decreased light sensitivity due to impaired visual cycle (poor regeneration of rhodopsin)
How does ageing affect contrast sensitivity? [Ageing Vision #3]
Decreased at intermediate and high spatial frequencies due to retinal + neural factors
How does ageing affect visual acuity? [Ageing Vision #3]
Worse VA (compared to young) in low luminance and contrast conditions
How does ageing affect Critical Flicker Frequency? [Ageing Vision #3]
Decreases. Not due to pupil size but potentially due to stimulus persistence theory
How does ageing affect visual fields? [Ageing Vision #3]
Depends on ocular disease progression
What is Anomalous Retinal Correspondance? [Arc #1]
A.K.A ‘Abnormal Retinal Correspondance’
- is a binocular adaptation to compensate for eye deviation where the fovea of one eye has a common visual direction with an extrofoveal area in the other eye.
Explain how ARC works [Arc #1]
When you have a turned eye, an image falling on the fovea of that turned eye will be projected at a non-corresponding point to the other eye. In ARC, the image lands on a “psuedofovea” of the turned eye: a compensation mechanism to prevent diplopia
What is Normal Retinal Correspondance? (NRC) [Arc #1]
Is when an image falls on both foveas, regardless of whether one eye is turned or not
Describe the vision of a strabismic (turned eye) patient who has NRC? [Arc #1]
Diplopia
Describe the vision of a strabismic patient who has ARC? [Arc #1]
Not diplopia
What is the angle of anomaly? [Arc #1]
describes the degree of visual deviation between eyes for a strabismic patient (i.e. the degree of shift in visual direction)
How do you mathematically calculate the angle of anomaly in a strabismic patient? [Arc #1]
Objective Angle - Subjective Angle
- objective angle: difference between location of the ‘true fovea’ and image location
- subjective angle: difference between location of the ‘pseudofovea’ and image location
What does the objective angle represent (in strab with ARC)? [Arc #1]
difference between location of ‘true fovea’ and image location
What does the subjective angle represent (in strab with ARC)? [Arc #1]
difference between location of ‘psuedofovea’ and image location
Name the 3 different types of ARC [Arc #2]
- Harmonius: angle of anomaly = angle of deviation
- Unharmonius: angle of anomaly less than angle of deviation
- Paradoxical: angle of anomaly more than angle of deviation
What visual symptom arises from unharmonius and paradoxical ARC [Arc #2]
Diplopia, because the psuedo-fovea does not fully compensate for the angle of deviation
Can unharmonius ARC be made harmonius? [Arc #2]
Yes it can
What type of diplopia results from the following in unharmonius ARC: esotropia and exotropia? [Arc #2]
Esotropia: uncrossed diplopia
Exotropia: crossed diplopia
What type of diplopia results from the following in paradoxical ARC: esotropia and exotropia? [Arc #2]
Esotropia: crossed diplopia
Exotropia: uncrossed diplopia
(because it’s paradoxical)
What 2 techniques can you use to classify ARC? [Arc #2]
- Synoptophore
- Worth 4 light
Explain the worth’s 4 light test setup [Arc #2]
4 circular lights (2 green, 1 red, 1 white). Right eye with red filter sees red dot and white dot; left eye with green filter sees green dots and white dots
What would a person NRC see in the worth 4 light test? [Arc #2]
Sees all dots correctly in each eye and only sees 4 dots (simultaneous perception and sensory fusion). (right eye sees red and left eye sees green)
What would a person with harmonius ARC see in the worth 4 light test? [Arc #2]
Sees 4 lights
How many lights on the worth 4 light test would be seen in a patient with double vision? [Arc #2]
Will see 5 lights
In the worth 4 light test, how would the dots appear in diplopia with esotropia vs exotropia? [Arc #3]
esotropia (uncrossed): red dots on right side, green on left
exotropia (crossed): red dots on left side, green on right
How does the horopter for exotropic subjects with harmonius ARC compare to normal? [Arc #3]
- similar but steeper curve (slightly skewed)
- abnormal points peripherally
- points don’t really align very well
How does the horopter for esotropic subjects with harmonius ARC compare to normal? [Arc #3]
- horopter exhibits a local convexity or ‘notch’ which is closer to the visual axis of the better eye
How would you describe the spatial vision of amblyopic patients [Arc #3]
Experience distortion patterns
What treatments are available for ARC? [Arc #4]
- Occlusion,
- Orthoptic Exercise
- Surgery
- Prisms
