Nanophthalmos in a Melanesian population

Purpose: To characterize the ophthalmic features and causes of visual loss in a cohort of Melanesians living in New Caledonia with nanophthalmos. Methods: In this observational study, axial length, visual acuity (VA), cycloplegic autorefraction were assessed and dilated fundus examination was performed. Visual impairment was defined as VA<6/12 in the better eye, hypermetropia as >+1.0 dioptre (D), astigmatism as ≥1.0D and anisometropia as ≥1.0D difference between both eyes. Unilateral amblyopia was defined as at least a two-line difference in VA between both eyes and bilateral amblyopia as VA<6/12 in both eyes which was not adequately explained by refractive error and macular folds. Results: Seventeen community-dwelling participants (aged 1.1-45.3 years) with short axial length (range from 16.1 to 21.6mm) were identified. Of the 17 subjects, 14 were found to have crowded optic discs, three with papillomacular folds, three with a papillomacular band and three with macular radial folds. Further, all subjects demonstrated bilateral hypermetropia (range from + 1.3D to + 15.1D). A high proportion of subjects had astigmatism (12) and anisometropia (nine) in at least one eye. Visual impairment was found in nine subjects: five bilateral and four unilateral. Causes of visual impairment included amblyopia (seven), ametropia (seven) and macular folds (two). Amblyopia was attributed to several factors, including hypermetropia, anisometropia, astigmatism and esotropia. Conclusions: In this sample of Melanesians with nanophthalmos, a spectrum of ophthalmic features that was consistent with intraocular crowding was found. Over half of the subjects were visually impaired, mostly due to amblyopia and ametropia. Further characterization of the underlying genetic cause of nanophthalmos in this cohort will be the focus of future studies.