AMBLYOPIA 2 Ralph P Garzia Nonvisual acuity deficits

AMBLYOPIA - 2 Ralph P. Garzia

Non-visual acuity deficits in amblyopia reduced contrast sensitivity deficient accommodative skills amplitude, facility, lag deficient oculomotor skills fixation, pursuits, saccades spatial uncertainty spatial distortion eccentric fixation

Amblyopia & contrast sensitivity Note the differences in CSF function between amblyopes

Amblyopia & accommodation normal accommodative stimulus-response curve

Amblyopia & accommodation Amblyopic accommodative stimulus-response curve

Accommodation & amblyopia Effects of eccentric fixation Normal accommodative responses as a function of amount of eccentric fixation or retinal eccentricity

Accommodation & amblyopia Latency increased Gain reduced Amplitude reduced Facility reduced

Amblyopia & fixation instability fixating a + > steady fixation >

Amblyopia & steady fixation EOG’s more instability > with greater acuity loss > >

Amblyopia & smooth pursuits EOG of smooth pursuit to sinusoidal stimuli acceleration uniform velocity saccadic intrusions

Amblyopia & saccades Dysmetria multiple small saccades in the direction of the target displacement

Oculomotor deficits in amblyopia Fixation unstable increased drift amplitude Saccades increased latency decreased peak velocity dysmetric Pursuits increased number of loses of fixation increased number of saccadic intrusions decreased gain

Snellen Acuity vs grating acuity Anisometropic amblyopes A’s cluster on the 1: 1 line Strabismic amblyopes S’s are far to the right normal eyes > Strabismic amblyopes: oculomotor problems spatial distortion problems

Oculomotor effects Snellen vs. grating acuity VEP’s CSF Interferometry What these have in common is a spatially redundent pattern.

Amblyopia and visual acuity behavior Typical letter confusions made by amblyopic eyes Note the confusion similar shapes sequence errors transpositions What’s the VA?

Characteristics of visual acuity measurements in amblyopia crowding effects distortions / misperceptions loss of place / out of order noisy short and long term variability

Amblyopia and visual acuity behavior Typical letter confusions made by amblyopic eyes Note the confusion similar shapes sequence errors transpositions What’s the VA?

Amblyopia & contour interaction Test stimulus used to determine contour interaction

Contour interaction normal eyes and amblyopic eyes Contour interaction as multiples of gap width (critical detail) normal eyes > amblyopic eye > ci effects are similar in normal & amblyopic eyes as a function of visual acuity

Psychometric chart Landolt C’s are the targets There are 8 at each VA level There are equal spacing between each of the test optotypes (C’s) and the nearest contour on all 4 sides Spacing is equal to the overall size of the test optotypes or 5 x’s the critical detail

Psychometric or “S” graph Normal eye has a steep function Amblyopic eye has a very gradual dropoff of visual acuity

Crowding phenomenon Entire chart vs. Whole line vs. Single letter

Eccentric fixation & visual acuity combine all the lines and get a best fit curve or linear formula: MAR’=. 4(ef∆)+1 e. g. ef=1 deg=1. 75∆ MAR’=. 4(1. 75)+1 MAR’=0. 7+1=1. 7’ VA=20/34

Visuoscopy central fixation > nasal eccentric fixation >

Haidinger’s brushes Fixate on the dot: where are the brushes perceived