Purpose: To explore associations between refractive error and foveal hypoplasia in infantile nystagmus syndrome (INS).Methods: Fifty participants with INS (albinism n=33, non-albinism infantile nystagmus [NAIN] n=17) age 4-48 years were recruited. Cycloplegic refractive error and LogMAR acuity were obtained. Spherical equivalent (SER), most ametropic meridian (MAM) refractive error and better eye acuity (VA) were used for analyses. High resolution spectral-domain optical coherence tomography (SD-OCT) was used to obtain foveal scans which were graded using the Foveal Hypoplasia Grading Scale. Associations between grades of severity of foveal hypoplasia and refractive error and VA were explored. Results: Participants with more severe foveal hypoplasia had significantly higher MAMs and SERs (Kruskal-Wallis H p=0.005 and p=0.008 respectively). There were no statistically significant associations between foveal hypoplasia and cylindrical refractive error (Kruskal-Wallis H p=0.144). Analyses demonstrated significant differences between participants with albinism or NAIN in terms of SER and MAM (Mann-Whitney U p=0.001). There were no statistically significant differences between astigmatic errors between participants with albinism and NAIN. Controlling for the effects of albinism, results demonstrated no significant associations between SER and MAM and foveal hypoplasia (partial correlation p>0.05). Poorer visual acuity was statistically significantly associated with more severe foveal hypoplasia (Kruskal-Wallis H p=0.001) and with a diagnosis of albinism (Mann-Whitney U p=0.001). Conclusions: Increasing severity of foveal hypoplasia is associated with poorer VA, reflecting reduced cone density in INS. Individuals with INS also demonstrate a significant association between more severe foveal hypoplasia and increasing hyperopia. However, in the absence of albinism there is no significant relation between refractive outcome and degree of foveal hypoplasia suggesting that foveal maldevelopment in isolation does not significantly impair the emmetropisation process. It is likely that impaired emmetropisation evidenced in the albinism group may be attributed to the whole eye effect of albinism.
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- refractive error