Enhanced S-cone syndrome (ESCS) is mainly associated with mutations in the NR2E3 gene. However, rare mutations in the NRL gene have been reported in patients with ESCS. We report on an ESCS phenotype in additional patients with autosomal recessive NRL (arNRL) mutations. Three Moroccan patients of two different families with arNRL mutations were enrolled in this study. The mutation in the DNA of one patient, from a consanguineous marriage, was detected by homozygosity mapping. The mutation in the DNA of two siblings from a second family was detected in a targeted next-generation sequencing project. Full ophthalmic examination was performed, including best-corrected visual acuity, slit-lamp biomicroscopy, funduscopy, Goldmann kinetic perimetry, optical coherence tomography, fundus autofluorescence, and extended electroretinography including an amber stimulus on a blue background and a blue stimulus on an amber background. One patient carried a homozygous missense mutation (c.508C>A; p.Arg170Ser) in the NRL gene, whereas the same mutation was identified heterozygously in the two siblings of a second family, in combination with a one base-pair deletion (c.654del; p.Cys219Valfs*4) on the other allele. All patients had reduced visual acuity and showed a typical clumped pigmentary retinal degeneration (CPRD). Foveal schisis-like changes were observed in the oldest patient. An electroretinogram (ERG) under dark-adapted conditions showed absent responses for low stimulus strengths and reduced responses for high stimulus strengths, with constant b-wave latencies despite increasing stimulus strength. A relatively high amplitude was detected with a blue stimulus on an amber background, while an amber stimulus on a blue background showed reduced responses. The arNRL mutations cause a phenotype with typical CPRD. This phenotype has previously been described in patients with ESCS caused by NR2E3 mutations, and rarely by NRL mutations. Based on our findings in ERG testing, we conclude that S-cone function is enhanced in our patients in a similar manner as in patients with NR2E3-associated ESCS, confirming previous reports of NRL as a second gene to cause ESCS.

To describe the natural disease course of CRB1-associated retinal dystrophies, and to identify clinical endpoints for future clinical trials. Single center, prospective case series. An investigator-initiated nationwide collaborative study that included 22 patients with CRB1-associated retinal dystrophies. Patients underwent ophthalmic assessment at baseline and 2 years after baseline. Clinical examination included best-corrected visual acuity (BCVA) using ETDRS charts, Goldmann kinetic perimetry (V4e isopter seeing retinal areas), microperimetry, full-field electroretinography (ERG), full-field stimulus threshold (FST), fundus photography, spectral-domain optical coherence tomography and fundus autofluorescence imaging. Based on genetic, clinical and electrophysiological data, patients were diagnosed with retinitis pigmentosa (n = 19; 86%), cone-rod dystrophy (n = 2; 9%) or isolated macular dystrophy (n = 1; 5%). Two-year analysis of the entire cohort showed no significant changes in BCVA (p = 0.069) or V4e isopter seeing retinal areas (p = 0.616), although signs of clinical progression were present in individual patients. Macular sensitivity measured on microperimetry revealed a significant reduction at 2-year follow-up (p < 0.001). FST responses were measurable in patients with non-recordable ERGs. On average, FST responses remained stable during follow-up. In CRB1-associated retinal dystrophies, visual acuity and visual field measures remain relatively stable over the course of 2 years. Microperimetry showed a significant decrease in retinal sensitivity during follow-up, and may be a more sensitive progression marker. Retinal sensitivity on microperimetry may serve as a functional clinical endpoint in future human treatment trials for CRB1-associated retinal dystrophies.

Purpose: To identify the gene defect and to study the clinical characteristics and natural course of disease in a family originally diagnosed with oligocone trichromacy (OT), a rare congenital cone dysfunction syndrome. Methods: Extensive clinical and ophthalmologic assessment was performed on two siblings with OT and long-term follow up data were analyzed. Subsequently, whole exome sequencing (WES) and Sanger sequence analysis of CEP290 was performed in the two siblings. Additionally, the identified CEP290 mutations were analyzed in persons with achromatopsia (ACHM) (n = 23) and autosomal recessive or isolated cone dystrophy (CD; n = 145). Results: In the first decade of life, the siblings were diagnosed with OT based on low visual acuity, photophobia, nystagmus, and absent cone response on electroretinography , but with normal color discrimination. Over time, the phenotype of OT evolved to a progressive degenerative disease without any CEP290-associated non-ocular features. In both siblings, two nonsense mutations (c.451C>T; p.(Arg151*) and c.4723A>T; p.(Lys1575*)) in CEP290 were found. Previously, p.(Arg151*) was demonstrated to induce nonsense-mediated alternative splicing events leading to intact open reading frames of the resulting mRNA products (p.(Leu148_Glu165del) and p.(Leu148_Lys172del)). mRNA analysis for p.(Lys1575*) confirmed a suspected hypomorphic character, as exon 36 skipping was observed in a small fraction of CEP290 mRNA, resulting in a 36 aa in-frame deletion (p.(Glu1569_Trp1604del)). No additional cases carrying these variants were identified in the ACHM and CD cohorts. Conclusions: Compound heterozygous hypomorphic mutations in CEP290 may lead to a rare form of cone-dominated retinal dystrophy, a novel phenotype belonging to the CEP290-associated spectrum of ciliopathies. These findings provide insight into the effect of CEP290 mutations on the clinical phenotype.

The authors wish to make the following correction to this paper [1].

Purpose: The purpose of this study was to describe the association among nystagmus characteristics, foveal hypoplasia, and visual acuity in patients with albinism. Methods: We studied nystagmus recordings of 50 patients with albinism. The nystagmus waveform was decomposed into two types: dominantly pendular and dominantly jerk. We correlated the nystagmus type, amplitude, frequency, and percentage of low velocity (PLOV) to Snellen visual acuity and foveal hypoplasia grades. Results: The grade of foveal hypoplasia and visual acuity showed a strong correlation (r = 0.87, P < 0.0001). Nystagmus type and PLOV had the strongest significant (P < 0.0001) correlation with visual acuity (r = 0.70 and r = −0.56, respectively) and with foveal hypoplasia (r = 0.76 and r = −0.60, respectively). Patients with pendular nystagmus type had the lowest PLOV, and the highest grade of foveal hypoplasia (P < 0.0001). Severe foveal hypoplasia (grade 4), was almost invariably associated with pendular nystagmus (86%). Conclusions: Foveal hypoplasia grade 4 is associated with pendular nystagmus, lower PLOV, and worse visual acuity. Based on these results, nystagmus recordings at a young age may contribute to predicting visual outcomes.

Purpose: To describe the association between nystagmus characteristics and pattern-reversal VEP (prVEP) P100 amplitude and peak time in patients with albinism. Methods: We analyzed the prVEP (60’ and 15’ checksize) and nystagmus recordings from 47 patients with albinism, 17 with a relatively good visual acuity (≤ 0.3 logMAR), and 30 with a relatively poor visual acuity (≥ 0.6 logMAR). The nystagmus waveforms were classified into two types: dominantly pendular and dominantly jerk. We correlated the nystagmus type, amplitude, frequency, and percentage of low velocity (PLOV) to P100 amplitude and peak time. Results: For most patients (87%), reproducible responses were observed for the large checks (60'). Among patients with good visual acuity, 94% had reproducible responses of which the majority (82%) of P100 amplitudes fell within the normal reference range. In contrast, although 83% of patients with poor visual acuity showed reproducible responses, only a minority (17%) of P100 amplitudes were within the normal range. The P100 amplitude to 60’check sizes was statistically correlated with PLOV (r = 0.58, p < 0.0001), nystagmus type (r = −0.55, p < 0.0001), and nystagmus amplitude (r = −0.39, p = 0.0092). Patients with relatively good visual acuity and jerk nystagmus exhibited the highest PLOV and the largest P100 amplitude (p < 0.0001). In contrast, there was no significant correlation between P100 peak time and any nystagmus parameters in patients with good or poor visual acuity.93% normal peak time. For the small checks (15’), 76% of patients with good visual acuity, still showed reproducible responses, with the majority (71%) of P100 amplitudes falling within the normal reference range. In contrast, among patients with poor visual acuity, only 3% (1 patient) showed reproducible responses, but with amplitudes below the normal range. For the patients with good visual acuity, PLOV showed a significant correlation with P100 amplitude. P100 peak time was normal for 77% (10/13) of these patients. Conclusions: For the prVEP with 60’ checks, nystagmus in patients with albinism predominantly affects the P100 amplitude but not the P100 peak time. For 15’ checks the amplitude is often so small that clear responses are no longer discernable, especially in patients with poor visual acuity.