Early signs of longitudinal progressive cone photoreceptor degeneration in achromatopsia
ABSTRACT To characterise longitudinal progressive retinal changes in achromatopsia.
Ultrahigh-resolution spectral optical coherence tomography (Copernicus, 3 μm axial resolution) was used to obtain tomograms of the fovea from five children and three adults with achromatopsia. Each patient was scanned twice with a mean follow-up time of 16 months. Progressive changes in reflectivity at the inner segment/outer segment (IS/OS) junction, the central macular and outer nuclear layer thickness were analysed.
Younger patients (<10 years; patient 1-5) showed progressive morphological changes at the IS/OS junction between visits 1 and 2. However, older patients (>40 years; patients 6-8) did not have any changes in the retinal morphology between visits 1 and 2. In patients 1 and 2, IS/OS discontinuities (visit 1) developed into a hyper-reflective zone confined to the fovea (visit 2). In patient 3, the hyper-reflective zone (visit 1) progressed to form an IS/OS disruption and early formation of a small hypo-reflective zone (visit 2). Patients 4 and 5 had a hypo-reflective zone (visit 1) which subsequently increased in size (visit 2). There was a decrease in central macular and outer nuclear layer thickness between visits 1 and 2 in children.
For the first time, we show progressive longitudinal changes in retinal morphology in achromatopsia. Early changes include subtle IS/OS reflectivity alterations. The dynamic retinal changes in younger patients provide evidence that it represents a progressive disorder, and implementation of gene therapy during the early stages of the disease may provide best prognosis.
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ABSTRACT: Autosomal-dominant idiopathic infantile nystagmus has been linked to 6p12 (OMIM 164100), 7p11.2 (OMIM 608345) and 13q31-q33 (OMIM 193003). PAX6 (11p13, OMIM 607108) mutations can also cause autosomal-dominant nystagmus, typically in association with aniridia or iris hypoplasia. We studied a large multigenerational white British family with autosomal-dominant nystagmus, normal irides and presenile cataracts. An SNP-based genome-wide analysis revealed a linkage to a 13.4-MB region on chromosome 11p13 with a maximum lod score of 2.93. A mutation analysis of the entire coding region and splice junctions of the PAX6 gene revealed a novel heterozygous missense mutation (c.227C>G) that segregated with the phenotype and is predicted to result in the amino-acid substitution of proline by arginine at codon 76 p.(P76R). The amino-acid variation p.(P76R) within the paired box domain is likely to destabilise the protein due to steric hindrance as a result of the introduction of a polar and larger amino acid. Eye movement recordings showed a significant intrafamilial variability of horizontal, vertical and torsional nystagmus. High-resolution in vivo imaging of the retina using optical coherence tomography (OCT) revealed features of foveal hypoplasia, including rudimentary foveal pit, incursion of inner retinal layers, short photoreceptor outer segments and optic nerve hypoplasia. Thus, this study presents a family that segregates a PAX6 mutation with nystagmus and foveal hypoplasia in the absence of iris abnormalities. Moreover, it is the first study showing detailed characteristics using eye movement recordings of autosomal-dominant nystagmus in a multigenerational family with a novel PAX6 mutation.European Journal of Human Genetics advance online publication, 14 August 2013; doi:10.1038/ejhg.2013.162.European journal of human genetics: EJHG 08/2013; 22(3). DOI:10.1038/ejhg.2013.162 · 4.23 Impact Factor
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ABSTRACT: To describe the unique diagnostic fundus autofluorescence (FAF) patterns in patients with achromatopsia and the associated findings on optical coherence tomography (OCT). Observational case series. We evaluated 10 patients with achromatopsia by means of best-corrected visual acuity (BCVA), ophthalmoscopy, Goldmann visual field, full-field electroretinography (ffERG), OCT, and FAF photography. FAF patterns were compared with patient age and foveal changes on OCT. Patients fell into two dichotomous age groups at the time of evaluation: six patients ranged from 11 to 23 years of age, and 3 patients ranged from 52 to 63 years of age. All patients had severely reduced photopic ffERG responses, including those exhibiting preserved foveal structure on OCT. The younger patients had absent to mild foveal atrophy on OCT, and four of the six demonstrated foveal and parafoveal hyperfluorescence on FAF. In addition, a 7-month-old child with compound heterozygous mutations in CNGA3 demonstrated similar foveal hyperfluorescence. The older patients demonstrated advanced foveal atrophy and punched-out foveal hypofluorescence with discrete borders on FAF imaging corresponding to the area of outer retinal cavitation on OCT. Foveal hyperfluorescence is an early sign of achromatopsia that can aid in clinical diagnosis. In our cohort, patients with achromatopsia demonstrated age-dependent changes in FAF, which are likely to be progressive and to correlate with foveal atrophy and cavitation on OCT. This finding may be useful in charting the natural course of the disease and in defining a therapeutic window for treatment.American Journal of Ophthalmology 08/2013; DOI:10.1016/j.ajo.2013.06.033 · 4.02 Impact Factor
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ABSTRACT: To characterize retinal structure and function in achromatopsia (ACHM) in preparation for clinical trials of gene therapy. Cross-sectional study. Forty subjects with ACHM. All subjects underwent spectral domain optical coherence tomography (SD-OCT), microperimetry, and molecular genetic testing. Foveal structure on SD-OCT was graded into 5 distinct categories: (1) continuous inner segment ellipsoid (ISe), (2) ISe disruption, (3) ISe absence, (4) presence of a hyporeflective zone (HRZ), and (5) outer retinal atrophy including retinal pigment epithelial loss. Foveal and outer nuclear layer (ONL) thickness was measured and presence of hypoplasia determined. Photoreceptor appearance on SD-OCT imaging, foveal and ONL thickness, presence of foveal hypoplasia, retinal sensitivity and fixation stability, and association of these parameters with age and genotype. Forty subjects with a mean age of 24.9 years (range, 6-52 years) were included. Disease-causing variants were found in CNGA3 (n = 18), CNGB3 (n = 15), GNAT2 (n = 4), and PDE6C (n = 1). No variants were found in 2 individuals. In all, 22.5% of subjects had a continuous ISe layer at the fovea, 27.5% had ISe disruption, 20% had an absent ISe layer, 22.5% had an HRZ, and 7.5% had outer retinal atrophy. No significant differences in age (P = 0.77), mean retinal sensitivity (P = 0.21), or fixation stability (P = 0.34) across the 5 SD-OCT categories were evident. No correlation was found between age and foveal thickness (P = 0.84) or between age and foveal ONL thickness (P = 0.12). The lack of a clear association of disruption of retinal structure or function in ACHM with age suggests that the window of opportunity for intervention by gene therapy is wider in some individuals than previously indicated. Therefore, the potential benefit for a given subject is likely to be better predicted by specific measurement of photoreceptor structure rather than simply by age. The ability to directly assess cone photoreceptor preservation with SD-OCT and/or adaptive optics imaging is likely to prove invaluable in selecting subjects for future trials and measuring the trials' impact. The authors have no proprietary or commercial interest in any of the materials discussed in this article.Ophthalmology 10/2013; 121(1). DOI:10.1016/j.ophtha.2013.08.017 · 6.17 Impact Factor