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T. R. Candy, S. R. Bharadwaj; The Effect of Induced Anisometropia on Accommodation and Vergence During Development. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2894.
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© ARVO (1962-2015); The Authors (2016-present)
Anisometropia is associated with abnormal visual development but does not result in routine presentation for an eye examination as it has no obvious signs and symptoms. Little is known about its influence on visual function during infancy and the pre-school years. Here, we optically induce anisometropia in typically developing infants and children for brief periods of time to determine the effect on accommodation and vergence - two functions that help maintain clear and single vision.
Accommodative and vergence responses were recorded simultaneously using a PowerRefractor (25Hz). Twenty subjects (3.7 months to 29.8 years) watched a high contrast cartoon movie (1/f amplitude spectrum) on an LCD screen that moved between 80cms (1.25D) and 33cms (3.0D) at 0.50D/s, with a stable period of 4s at each viewing distance. This protocol was performed under four viewing conditions: i) habitual binocular viewing, ii and iii) with a +2D or +4D lens over one eye (induced anisometropia conditions) and iv) with one eye occluded using an IR filter. Accommodative and vergence gains were calculated for the 1.75D or MA stimulus for each viewing condition.
Binocular accommodative gains (Mean +/- SEM: 0.99 +/- 0.08) were significantly different (p=0.001) from monocular accommodative gains (0.47 +/- 0.09) for all ages (main effect: p=0.55). Accommodative gains with 2D (0.77 +/- 0.08) and 4D (0.76 +/- 0.08) of induced anisometropia were not significantly different from each other (p=0.99) or the binocular (p= 0.27 & 0.26, respectively) and monocular (p=0.07 & 0.06, respectively) conditions. The vergence gains were also significantly different for binocular (0.91 +/- 0.04) and monocular conditions (0.30 +/- 0.05) (p<0.001). The vergence gains with 2D (0.85 +/- 0.04) and 4D (0.69 +/- 0.04) of anisometropia fell between the two values. Both were significantly different from monocular conditions (p<0.001), but only the 4D was significantly different from binocular conditions (p=0.01). Subject’s age only had a marginal effect on the vergence gain (main effect: p=0.04).
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