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Shrikant R. Bharadwaj, Praveen Kumar Bandela, Gouthami Deshapathini; Distance Visual Acuity With Induced Astigmatism And Its Relation To The Ocular Accommodative State. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3657.
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© ARVO (1962-2015); The Authors (2016-present)
Astigmatism induces meridional differences in retinal image quality. The impact of polarity and axis of astigmatism on visual acuity under different viewing conditions and the role of accommodation in determining acuity with astigmatism remains poorly understood. This study determined the impact of induced myopic and hyperopic astigmatism on distance acuity under binocular, monocular and anisometropic viewing conditions.
Distance (3m) logMAR acuity was assessed after pupil dilation in 15 emmetropic adults (mean+SD: 22.3+2.0yrs) with +2D myopic and hyperopic astigmatism induced along 180º and 45º under three conditions: i) binocular viewing with lenses before both eyes, ii) monocular viewing with lens before left eye (right eye occluded) and iii) anisometropic viewing with lens before left eye and plano lens before right eye. The role of accommodation was determined by measuring consensual accommodation for the monocular distance target in 05 adults using an open-field autorefractor and by repeating the monocular condition in 06 adults after cycloplegia and in 15 emmetropic pseudophakes (57.9+9yrs) with monofocal IOL implants.
The main effect of viewing condition, polarity and axis of astigmatism on distance acuity was statistically significant (p<0.02). Relative to no astigmatism (-0.17+0.06), the acuity was poorer with induced myopic (0.21+0.32) than with induced hyperopic astigmatism (0.12+0.26) (p<0.01). Monocular acuity with induced astigmatism (0.22+0.32) was poorer than its binocular (0.10+0.26) and anisometropic (-0.16+0.07) counterparts (p<0.001). Acuity at 45º (0.08+0.30) was poorer than that at 180º (0.03+0.27) (p=0.02). Monocular distance accommodative states with induced myopic (0.60+0.64D) and hyperopic astigmatism (0.58+0.46D) were not significantly different from each other (p=0.93). The difference in accommodative state with induced myopic and hyperopic astigmatism was poorly correlated with the corresponding difference in acuity (r=0.25; p>0.1). Monocular acuity of cyclopleged phakic and pseudophakic eyes was poorer with induced myopic than with induced hyperopic astigmatism for both axes tested (both p<0.001).
Distance acuity with +2D induced astigmatism is poorer under monocular than under binocular and anisometropic conditions and it is poorer for myopic than for hyperopic astigmatism. Similarity in distance accommodative states with induced myopic and hyperopic astigmatism and the persistence of greater loss of acuity with myopic astigmatism in cyclopleged phakic and pseudophakic eyes, suggests minimal role of ocular accommodation in determining the asymmetric loss of acuity with induced astigmatism.
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