East Asia has experienced an excessive increase in myopia in the past decades with more than 80% of the younger generation now affected. Environmental and genetic factors are both assumed to contribute in the development of refractive errors, but the etiology is unknown. The environmental factor argued to be of greatest importance in preventing myopia is high levels of daylight exposure. If true, myopia prevalence would be higher in adolescents living in high latitude countries with fewer daylight hours in the autumn-winter. We examined the prevalence of refractive errors in a representative sample of 16–19-year-old Norwegian Caucasians (n = 393, 41.2% males) in a representative region of Norway (60° latitude North). At this latitude, autumn-winter is 50 days longer than summer. Using gold-standard methods of cycloplegic autorefraction and ocular biometry, the overall prevalence of myopia [spherical equivalent refraction (SER) ≤−0.50 D] was 13%, considerably lower than in East Asians. Hyperopia (SER ≥ + 0.50 D), astigmatism (≥1.00 DC) and anisometropia (≥1.00 D) were found in 57%, 9% and 4%. Norwegian adolescents seem to defy the world-wide trend of increasing myopia. This suggests that there is a need to explore why daylight exposure during a relatively short summer outweighs that of the longer autumn-winter.

A number of pro-inflammatory cytokines are significantly elevated in tear fluid from aniridia patients, and correlate with parameters for MGD in aniridia. Increased inflammation of the ocular surface may be a factor in the development of MGD in aniridia patients, and explain the high prevalence of MGD and dry eye disease in these patients.

Purpose To investigate the association between PAX6 genotype and macular morphology in congenital aniridia. Methods The study included 37 participants (15 males) with congenital aniridia (aged 10–72 years) and 58 age-matched normal controls (18 males). DNA was isolated from saliva samples. PAX6 exons, intron/exon junctions, and known regulatory regions were amplified in PCR and sequenced. Multiplex ligation-dependent probe amplification (MLPA) was performed to detect larger deletions or duplications in PAX6 or known cis -regulatory regions. Spectral-domain optical coherence tomography images were acquired and segmented semiautomatically. Mean thicknesses were calculated for inner and outer retinal layers within the macula along nasal and temporal meridians. Results Mutations in PAX6 or regulatory regions were found in 97% of the participants with aniridia. Foveal hypoplasia was observed in all who had a mutation within the PAX6 gene. Aniridic eyes had thinner outer retinal layers than controls, but with large between-individual variation (mean ± SD, 156.3 ± 32.3 µm vs 210.8 ± 12.3 µm, P < 0.001). Parafoveal and perifoveal inner and outer retinal layers were thinner in aniridia. Participants with mutations in noncoding PAX6 regions had thicker foveal outer retinal layers than those with mutations in the PAX6 coding regions ( P = 0.04) and showed signs of postnatal development and maturation. Mutations outside the PAX6 gene were associated with the mildest retinal phenotypes. Conclusions PAX6 mutations are associated with significant thinning of macular inner and outer retinal layers, consistent with misdirected retinal development resulting in abnormal foveal formation and reduced number of neurons in the macula, with mutations in PAX6 coding regions giving the worst outcome.

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PurposeTo assess color vision and its association with retinal structure in persons with congenital aniridia.MethodsWe included 36 persons with congenital aniridia (10–66 years), and 52 healthy, normal trichromatic controls (10–74 years) in the study. Color vision was assessed with Hardy-Rand-Rittler (HRR) pseudo-isochromatic plates (4th ed., 2002); Cambridge Color Test and a low-vision version of the Color Assessment and Diagnosis test (CAD-LV). Cone-opsin genes were analyzed to confirm normal versus congenital color vision deficiencies. Visual acuity and ocular media opacities were assessed. The central 30° of both eyes were imaged with the Heidelberg Spectralis OCT2 to grade the severity of foveal hypoplasia (FH, normal to complete: 0–4).ResultsFive participants with aniridia had cone opsin genes conferring deutan color vision deficiency and were excluded from further analysis. Of the 31 with aniridia and normal opsin genes, 11 made two or more red-green (RG) errors on HRR, four of whom also made yellow-blue (YB) errors; one made YB errors only. A total of 19 participants had higher CAD-LV RG thresholds, of which eight also had higher CAD-LV YB thresholds, than normal controls. In aniridia, the thresholds were higher along the RG than the YB axis, and those with a complete FH had significantly higher RG thresholds than those with mild FH (P = 0.038). Additional increase in YB threshold was associated with secondary ocular pathology.ConclusionsArrested foveal formation and associated alterations in retinal processing are likely to be the primary reason for impaired red-green color vision in aniridia.