title: Investigating the relationship between foveal morphology and refractive error in a population with infantile nystagmus syndrome.
abstract: OBJECTIVE
  We explored associations between refractive error and foveal hypoplasia in infantile nystagmus syndrome (INS).
  
  
  METHODS
  We recruited 50 participants with INS (albinism n = 33, nonalbinism infantile nystagmus [NAIN] n = 17) aged 4 to 48 years. 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 test P = 0.005 and P = 0.008, respectively). There were no statistically significant associations between foveal hypoplasia and cylindrical refractive error (Kruskal-Wallis H test P = 0.144). Analyses demonstrated significant differences between participants with albinism or NAIN in terms of SER and MAM (Mann-Whitney U test 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 associated statistically significantly with more severe foveal hypoplasia (Kruskal-Wallis H test P = 0.001) and with a diagnosis of albinism (Mann-Whitney U test 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 impair significantly the emmetropization process. It likely is that impaired emmetropization evidenced in the albinism group may be attributed to the whole eye effect of albinism.
authors.affiliation: The University of Ulster, Vision Science Research Group, Coleraine, Northern Ireland. healeynatasha@hotmail.com
authors.forename: Natasha
authors.initials: N
authors.lastname: Healey
authors.forename: Eibhlin
authors.initials: E
authors.lastname: McLoone
authors.forename: Gerald
authors.initials: G
authors.lastname: Mahon
authors.forename: A Jonathan
authors.initials: AJ
authors.lastname: Jackson
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Saunders
authors.forename: Julie F
authors.initials: JF
authors.lastname: McClelland
mesh_terms: D000293:Adolescent; D000328:Adult; D016115:Albinism, Oculocutaneous / Q000150:complications*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005584:Fovea Centralis / Q000002:abnormalities*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020417:Nystagmus, Congenital / Q000150:complications*; D012030:Refractive Errors / Q000150:complications* / Q000175:diagnosis; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence; D014792:Visual Acuity; D055815:Young Adult