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F. A. Proudlock, N. Sarvananthan, M. Surendran, I. Gottlob; Meridional Distribution of Refractive Astigmatism in Infantile and Acquired Nystagmus. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1997.
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© ARVO (1962-2015); The Authors (2016-present)
Previous literature suggests that emmetropization occurs preferentially for the horizontal axis in infantile nystagmus, leading to ‘with the rule’ astigmatism. Suggested reasons for this include the reduced motion smear blur for horizontally oriented images and mechanical induced changes due to the horizontal nystagmus. We investigated the meridional distribution of refractive astigmatism in a representative group of patients with infantile nystagmus.
The refractive errors of 376 patients with infantile (108 idiopathic (IIN, or unassociated), 43 with albinism, 47 with manifest latent nystagmus (MLN), 82 associated with low vision or retinal disease (LV/RD)) and acquired nystagmus (n=96) were compared to an age-matched control group derived from 602 healthy individuals without nystagmus. Proportions of ‘with the rule’ (WTR) and ‘against the rule’ (ATR) astigmatism were compared to controls for each group using a criteria of 90°±15° and 180° ±15° axis, respectively .
The relative proportions of WTR and ATR astigmatism in infantile nystagmus (mean age 26.9, SD 21.6) were 34.3% and 13.9% for IIN, 44.2% and 14.0% for albinos, 40.4% and 10.6% for MLN, 35.4% and 15.9% for LV/RD, respectively. The proportion of WTR to ATR astigmatism was significantly higher than controls (14.5% and 16.4%, respectively; mean age 26.1, SD 24.7) for all groups (p<=0.007). The degree of astigmatism (mean cylinder±SD) was 1.00±1.14D for IIN, 1.52±1.20D for albinos, 1.02±1.01D for MLN and 1.42±1.43D for LV/RD, in comparison to 0.37±0.60 for controls. The degree of astigmatism was higher than controls for all groups (p<<0.0001).
WTR astigmatism is consistently higher than ATR astigmatism in infantile nystagmus with a WTR/ATR ratio of 2.2-3.8 for all subtypes in contrast to controls where the ratio was 0.88. This confirms the association between nystagmus and WTR astigmatism in all common infantile forms.
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