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William Bobier, Raiju Babu, Simon Clavagnier, Benjamin Thompson; Suppression Mapping in Amblyopia. An investigation into the gradient and depth of suppression. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3993.
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© ARVO (1962-2015); The Authors (2016-present)
In our study, we report on a novel suppression mapping approach that allows a psychophysical mapping of the regional distribution of suppression in patients with amblyopia from strabismus or anisometropia.
14 amblyopic participants (Mean age: 34.6±10) and 10 normal observers (Mean age: 28.1±5) participated in the experiment. To map the suppression scotoma, a stimulus was presented dichoptically using the z800 head-mounted display. The visual stimulus was composed of five concentric annuli with opposite contrast polarity. Each annulus subtended 2 degrees of visual eccentricity and was divided in 8 wedges of 45 degrees of visual angle. The contrast of the whole stimulus was set to 80 % .While maintaining his/her gaze on a central black fixation dot, the participant had to successively adjust the contrast of each of the 40 different sectors in order to match the contrast of the corresponding annulus (method of adjustment).
A repeated measures ANOVA performed with ECCENTRICITY as the within subject variable (5 levels: 0-2, 2-4, 4-6, 6-8, 8-10) and GROUP (Strabismic, Anisometropic and Normal) as the between subject variable, revealed a statistically significant main effect of the GROUP factor (F(2, 21)=13.549, p<0.001). Post hoc Bonferroni test revealed significant differences between Normals and Strabismic amblyopes (p<0.001) and between Normals and Anisometropic amblyopes (p<0.03). There was also a statistically significant main effect of ECCENTRICITY (F(4, 84)=19.46, p<0.001) with a significant difference observed between 8-10 degrees and all other eccentricities (p<0.001) except for the eccentricity between 6-8 degree (closest to the periphery; p>0.05). There was no statistically significant interaction between GROUP and ECCENTRICITY (F(8, 84)=1.942, p =0.064). This interaction became statistically significant once we pooled the data for the anisometropes and strabismics (F(4, 88)=3.172, p<0.05).
Suppression is evident in all amblyopes, although the depth of suppression appears to show a gradation with greater suppression in the centre compared to periphery. The depth of suppression is also seen to be greater for strabismics compared to anisometropes.
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