Hisao Ohde

Dominant Mutations in RP1L1 Are Responsible for Occult Macular Dystrophy

Occult macular dystrophy (OMD) is an inherited macular dystrophy characterized by progressive loss of macular function but normal ophthalmoscopic appearance. Typical OMD is characterized by a central cone dysfunction leading to a loss of vision despite normal ophthalmoscopic appearance, normal fluorescein angiography, and normal full-field electroretinogram (ERGs), but the amplitudes of the focal macular ERGs and multifocal ERGs are significantly reduced at the central retina. Linkage analysis of two OMD families was performed by the SNP High Throughput Linkage analysis system (SNP HiTLink), localizing the disease locus to chromosome 8p22-p23. Among the 128 genes in the linkage region, 22 genes were expressed in the retina, and four candidate genes were selected. No mutations were found in the first three candidate genes, methionine sulfoxide reductase A (MSRA), GATA binding 4 (GATA4), and pericentriolar material 1 (PCM1). However, amino acid substitution of p.Arg45Trp in retinitis pigmentosa 1-like 1 (RP1L1) was found in three OMD families and p.Trp960Arg in a remaining OMD family. These two mutations were detected in all affected individuals but in none of the 876 controls. Immunohistochemistry of RP1L1 in the retina section of cynomolgus monkey revealed expression in the rod and cone photoreceptor, supporting a role of RP1L1 in the photoreceptors that, when disrupted by mutation, leads to OMD. Identification of RP1L1 mutations as causative for OMD has potentially broader implications for understanding the differential cone photoreceptor functions in the fovea and the peripheral retina.

Clinical application of the multifocal VEPs

Purpose. To determine whether visual field defects can be detected by the multifocal VEP technique. Methods. Multifocal VEPs were elicited by a pseudorandom binary m-sequence stimulus (VERIS II). The stimulus was a dartboard-like pattern of 61 sectors, and the luminance of each sector alternated between white and black. The stimulus area subtended approximately 25 degrees. Each recording was divided into 8 equal segments, and the total recording time was about 4 min. Multifocal VEPs were recorded from 25 normal subjects and six patients with visual field loss. The responses summed within 4 quadrants were used in the analysis and were compared with the visual fields obtained by perimetry. Results. In six perimetrically-documented visual field defects, the responses summed over each quadrant of the field were reduced in the corresponding affected quadrants. In addition, recovery of the visual field loss following treatment was accompanied by a recovery of the responses. Conclusions. Multifocal VEPs summed within four quadrants can be used for an objective evaluation of the visual fields. The testing can be obtained in 4 min with no pain or discomfort to the patient.

On- and off-responses of the photopic electroretinograms in X-linked juvenile retinoschisis.

PURPOSE To examine the physiologic condition of the middle retinal layer of patients with X-linked juvenile retinoschisis (xlRS) by studying the on- and off-responses of the photopic electroretinograms (ERGs). METHODS Eleven unrelated Japanese men (mean age; 24.9 +/- 7.6 years) who were clinically diagnosed with xlRS and molecularly confirmed as having XLRS1 mutations were investigated. For the photopic ERGs, the a-, b- and d-wave amplitudes elicited by long duration stimuli were recorded, and the responses from the xlRS patients were compared to those recorded from normal subjects (n = 14, mean age, 27.5 +/- 4.5 years). We also examined the relationship between the photopic ERG responses and the genotype. RESULTS No significant difference was found between the a- and d-wave amplitudes in the xlRS patients (34.2 +/- 8.7 microV, 52.5 +/- 10.4 microV, respectively), and those in normal subjects (40.4 +/- 10.3 microV, 44.7 +/- 6.3 microV, respectively). The mean b-wave amplitude in the xlRS patients was significantly smaller (10.5 +/- 7.7 microV) than the mean of normal subjects (46.4 +/- 10.2 microV) (P < 0.0001). No significant correlation was found between the ERG responses and the locus of the mutation. CONCLUSION The photopic ERG demonstrated considerable impairment of the on-pathway arising from an abnormality of the on-bipolar cells or possibly secondary to Müller cell abnormality in xlRS.

Fundus autofluorescence in autosomal dominant occult macular dystrophy.

OBJECTIVE To characterize fundus autofluorescence (FAF) images of eyes with autosomal dominant occult macular dystrophy (OMD). METHODS All patients received a comprehensive ophthalmologic examination for diagnosis of OMD. We evaluated the FAF images in 13 eyes of 7 patients with autosomal dominant OMD by confocal scanning laser ophthalmoscopy with excitation at 488 nm and emission more than 500 nm. RESULTS The FAF images showed unspecific weak foveal hyperfluorescence in 4 eyes of 2 patients; one showed a thin hyperfluorescence in the temporal fovea bilaterally and the other showed weak hyperfluorescence in the fovea bilaterally. The optical coherence tomographic images showed abnormalities of the photoreceptor inner segment-outer segment line and cone outer segment tip line in all patients. However, 5 patients had normal FAF images regardless of morphological abnormalities of the photoreceptor. CONCLUSIONS Fundus autofluorescence is a useful method to acquire additional information of photoreceptor/retinal pigment epithelium function in eyes with OMD. Fundus autofluorescence will be also helpful for the differential diagnosis of eyes with OMD vs eyes with other dystrophies that have a distinctive FAF pattern.

Clinical characteristics of occult macular dystrophy in family with mutation of RP1l1 gene.

Purpose: To report the clinical characteristics of occult macular dystrophy (OMD) in members of one family with a mutation of the RP1L1 gene. Methods: Fourteen members with a p.Arg45Trp mutation in the RP1L1 gene were examined. The visual acuity, visual fields, fundus photographs, fluorescein angiograms, full-field electroretinograms, multifocal electroretinograms, and optical coherence tomographic images were examined. The clinical symptoms and signs and course of the disease were documented. Results: All the members with the RP1L1 mutation except one woman had ocular symptoms and signs of OMD. The fundus was normal in all the patients during the entire follow-up period except in one patient with diabetic retinopathy. Optical coherence tomography detected the early morphologic abnormalities both in the photoreceptor inner/outer segment line and cone outer segment tip line. However, the multifocal electroretinograms were more reliable in detecting minimal macular dysfunction at an early stage of OMD. Conclusion: The abnormalities in the multifocal electroretinograms and optical coherence tomography observed in the OMD patients of different durations strongly support the contribution of RP1L1 mutation to the presence of this disease.

Macular nerve fibers temporal to fovea may have a greater potential to recover function in patients with Leber's hereditary optic neuropathy

PURPOSE It is known that even after visual loss, younger patients with Lebers hereditary optic neuropathy (LHON) can recover vision. The purpose of this study was to determine the mean age at onset for LHON patients with and without visual recovery who carried the 11778 mutation, and to determine the pattern of central vision recovery. METHODS Thirty-five LHON patients with the 11778 mutation of mitochondrial DNA who had visited the Keio University Hospital between 1980 and 1999 and were followed for 2 to 20 years, were the subjects of this retrospective study. The patients who had recovered vision were tested by Goldmann perimetry, Humphrey perimetry, and landmark-driven fundus microperimetry with a scanning laser ophthalmoscope (SLO). The fixation status was assessed by SLO microperimetry. RESULTS Nine of the 35 patients (14 of 70 eyes) demonstrated a recovery of visual acuity to better than 0.3 in at least one eye. The mean age of disease onset was 15.9 +/- 4.6 years in patients with visual recovery and 25.5 +/- 8.9 years in patients without visual recovery. This difference in the mean age at onset was significant (P =.0001; Welch t-test). These 9 patients (14 eyes) showed fenestrated central scotomas in testing by Humphrey 10-2 threshold and SLO microperimetry. The nasal side of the central visual fields had a higher sensitivity than the temporal side in 7 of the 9 patients in Humphrey 10-2 threshold testing. Areas insensitive to 0 dB were detected on the nasal side of the central retina in these patients by SLO microperimetry, and fixation stability was related to the degree of clinical visual acuity. CONCLUSION The LHON patients with the 11778 mutation and a younger age of onset were more likely to show visual recovery. The findings made by perimetry suggest that the nerve fiber bundles in the nasal field (retina temporal to the fovea) may have a greater potential to recover function in LHON patients.

Receptive-field properties of adult cat’s retinal ganglion cells with regenerated axons

Abstract Receptive-field properties of retinal ganglion cells (RGCs) that had regenerated their axons were studied by recording single-unit activity from strands teased from peripheral nerve (PN) grafts apposed to the cut optic nerve in adult cats. Of the 286 visually responsive units recorded from PN grafts in 20 cats, 49.7% were classified, according to their receptive-field properties, as Y-cells, 39.5% as X-cells, 6.6% as W-cells, and 4.2% were unclassified. The predominant representation of Y-cells is consistent with a corresponding morphological study (Watanabe et al. 1993a), which identified α-cells as the RGC type with the largest proportion of regenerating axons. Among the X-cells, we only found ON-center types, whereas both ON-center and OFF-center Y-cells were found. As in intact retinas, the receptive-field center sizes of Y-cells and W-cells were larger than those of X-cells at corresponding displacements from the area centralis. Within the 10° surrounding the area centralis, the receptive fields of X-cells with regenerated axons were larger than those in intact retinas, suggesting that some rearrangement of retinal circuitry occurred as a consequence of degeneration and regeneration. Receptive-field center responses of Y-, X-, and W-type units with regenerated axons were similar to those found in intact retinas, but the level of spontaneous activity of Y- and X-type units was, in general, less than that of intact RGCs. Receptive-field surrounds were weak or not detected in more than half of the visually responsive RGCs with regenerated axons.

Genetic variants of TP53 and EPHX1 in Leber’s hereditary optic neuropathy and their relationship to age at onset

PurposeTo determine whether genetic polymorphisms of the genes for oxidative stress and apoptosis cause the clinical variability in patients with Leber’s hereditary optic neuropathy (LHON).MethodsEighty-seven unrelated Japanese LHON patients carrying the 11778 mitochondrial mutation were studied at the Keio University Hospital. Their mean age (±SD) was 25.0 ± 13.0 years with a range 3 to 65 years. Eleven polymorphisms in nine genes were studied: seven genes related to oxidative stress (SOD2, GSTT1, GSTM1, EPHX1, NQO1, p22 PHOX, and NOS3), and two genes related to apoptosis (TP53 and CD95). Each genetic polymorphism was analyzed in relation to the age at onset and the final visual acuity.ResultsAmong the oxidative stress-related polymorphisms, a significant association between Tyr113His in the EPHX1 gene and the age at onset of the disease was identified (P = 0.026). LHON patients who were homozygous for His113 developed the disease earlier than those without this genotype (21.9 vs. 27.9 years). Among the apoptosis-related polymorphisms, a significant association between Arg72Pro in the TP53 gene and the age at onset was identified (P = 0.007). LHON patients who were homozygous for Arg72 developed the disease earlier than those without this genotype (20.5 vs. 28.1 years). In addition, LHON patients with both genotypes developed the disease significantly earlier (17.5 years, P = 0.011). No associations were found between the final visual acuity and the genetic polymorphisms examined.ConclusionNuclear genetic polymorphisms related to oxidative stress or apoptosis may modify the age at onset of LHON.

Woman with atypical unilateral Leber's hereditary optic neuropathy with visual improvement.

We describe a patient with Lebers hereditary optic neuropathy (LHON) who had a unilateral involvement and a gradual recovery of vision. A 50-year-old woman was referred to our clinic in December 2004 for the treatment of left optic neuritis. The visual acuity was 0.01 in her left eye and 1.5 in her right eye. The left eye had a central scotoma and a relative afferent pupillary defect. Ophthalmoscopy revealed a hyperaemic optic disc with indistinct margins in the left eye. Fluorescein angiography showed circumpapillary microangiopathy in both eyes and staining of the left optic disc. An nt 11778 mutation was identified and she was diagnosed with LHON. The central scotoma gradually improved, and the visual acuity had recovered to 0.3 in August 2007. LHON should still be considered even in older female patients presenting with unilateral acute visual loss when microangiopathy is seen. In such cases, molecular testing is effective in confirming a diagnosis of LHON.We describe a patient with Lebers hereditary optic neuropathy (LHON) who had a unilateral involvement and a gradual recovery of vision. A 50‐year‐old woman was referred to our clinic in December 2004 for the treatment of left optic neuritis. The visual acuity was 0.01 in her left eye and 1.5 in her right eye. The left eye had a central scotoma and a relative afferent pupillary defect. Ophthalmoscopy revealed a hyperaemic optic disc with indistinct margins in the left eye. Fluorescein angiography showed circumpapillary microangiopathy in both eyes and staining of the left optic disc. An nt 11778 mutation was identified and she was diagnosed with LHON. The central scotoma gradually improved, and the visual acuity had recovered to 0.3 in August 2007. LHON should still be considered even in older female patients presenting with unilateral acute visual loss when microangiopathy is seen. In such cases, molecular testing is effective in confirming a diagnosis of LHON.

Rhinogenous optic neuritis with drastic diurnal variation of visual function

We report a case of rhinogenous optic neuritis in a 50-year-old man demonstrating drastic diurnal variation in visual function. His left vision was 20/15 in the morning, which gradually decreased to counting fingers at night. Pupillary reaction and visual field showed the same fluctuation as vision. Complete remission of visual symptoms was achieved after endonasal ethmoid sinusotomy.