Color Vision in Aniridia

Abstract

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.

Characteristics and Utility of Fundus Autofluorescence in Congenital Aniridia Using Scanning Laser Ophthalmoscopy

“…All 35 aniridia patients in the original group underwent a general ophthalmologic examination, including ophthalmoscopy and OCT, accompanied by classification of aniridiaassociated keratopathy, cataract, and foveal hypoplasia. 16,20 Fourteen of the participants were selected in order to obtain the best-quality fundus photographs. The selection was based on lowest degree of keratopathy and cataract.…”

“…Patients with pseudophakia or aphakia were allowed to take part, but not if significant secondary cataract and/or capsular phimosis were present. Genetic analysis of participants with aniridia was performed as described by Pedersen et al 16 The study was approved by the Norwegian Regional Committees for Medical and Health Research Ethics (Application 2014/382). After receiving oral and written information about the study, all participants signed a written informed consent, as did parents of participants younger than 16 years.…”

“…Visual acuity (logMAR) was measured with a digital high-contrast chart at 6 m (TestChart 2000; Thomson Software Solutions, London, UK). Test distance was reduced to 3 or 1 m if a reliable measurement was unattainable at 6 m. 16 The examiner considered presence of nystagmus (yes or no) while the patient was resting and kept eyes in primary gaze position. Each subject was further examined in a slit-lamp biomicroscope.…”

“…15 Interestingly, rod and cone function were equally affected. This suggests that not only may the central retina be affected in aniridia, evident as foveal hypoplasia, 5,16 but the midperipheral and peripheral part may also be affected.…”

The Cone Photoreceptor Mosaic in Aniridia

“…[9][10][11] Aniridia associated mutations within the PAX6 gene are known to alter retinal cell composition and subsequent post-receptoral organization including arrested formation of the fovea. [12][13][14] It is not known if the degree of PAX6 haploinsufficiency correlates with the degree of foveal hypoplasia 15 and impaired migration of cone photoreceptors towards the fovea center. [9][10][11] Few studies have used high-resolution imaging to investigate retinal layer structure in aniridia, 13,16 and none have investigated the cone photoreceptor mosaic.…”