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Non-Organic Vision Loss
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Ashwini Kini, Mangayarkarasi Thandampallayam Ajjeya, Padmaja Sudhakar
Cone dystrophy: Patients with cone dystrophy present with vision loss, sensitivity to bright lights and poor color vision. It can occur in late teens to the sixties. The fundus exam may be normal in early stages and definitive changes usually occur well after visual loss. Fundus fluorescein angiography, ERG and color vision tests are important tools in the diagnosis of cone dystrophy.
Bardet−Biedl Syndrome
Published in Dongyou Liu, Handbook of Tumor Syndromes, 2020
Among the primary (cardinal) features of BBS, retinal degeneration includes rod-cone dystrophy, choroidal dystrophy, and global severe retinal dystrophy, of which rod-cone dystrophy (also referred to as retinitis pigmentosa due to defects in the transport of phototransduction proteins from the inner to the outer segments of photoreceptors causing rod and cone cell death) is most common, affecting 90%–100% of patients. Rod-cone dystrophy is a progressive retinal degeneration that usually manifests as night blindness by age 7 or 8, loss of color discrimination, and progressive tunnel vision (lose of peripheral vision) by the first decade of life, then loss of central vision and legal blindness by the second or third decade of life (Figure 25.1) [21–23]. Additional ophthalmologic features consist of nystagmus (rapid, involuntary eye movements), strabismus (lazy eye), high myopia, cataract (clouding of the lens), and glaucoma (damage to the optic nerve conducting signals to the brain).
Variability of retinopathy consequent upon novel mutations in LAMA1
Published in Ophthalmic Genetics, 2022
Elena R. Schiff, Nancy Aychoua, Savita Nutan, Indran Davagnanam, Anthony T. Moore, A. G. Robson, C. K. Patel, Andrew R. Webster, Gavin Arno
To the best of our knowledge, this is the first report of ISCEV-standard ERG and PERG findings in LAMA1-related retinopathy and is the first to further characterise retinal dysfunction using photopic On-Off and S-cone ERGs. The ERGs revealed a cone-rod dystrophy in three cases and a mild cone dystrophy in one other individual, with preservation or relative sparing of short-wavelength retinal sensitivity in three of three adult cases. The same three siblings showed a low b:a ratio in the LA 3 ERG but with mild a-wave reductions in two, suggesting greatest cone system dysfunction post-phototransduction and consistent with On-Off ERG evidence of both on- and off-bipolar cell system involvement. This is broadly consistent with the low photopic ERG b:a ratio described in a 3-year-old child with PTBHS but tested using a non-standard ERG protocol (26). It is emphasized that the DA ERG a-wave reductions in 3 of 4 of the current series were consistent with significant loss of rod photoreceptor function, and that the normal DA 10 ERG b:a ratios suggest that additional dysfunction post-phototransduction is confined to the cone system. PERG P50 components were undetectable in two cases and subnormal in one other, as is common in other forms of cone and cone-rod dystrophy and in keeping with relatively early macular dysfunction.
Effectiveness of Low Vision Rehabilitation Using Microperimetric Acoustic Biofeedback Training in Patients with Central Scotoma
Published in Current Eye Research, 2021
Esra Sahli, Deniz Altinbay, Pınar Bingol Kiziltunc, Aysun Idil
Macular diseases such as AMD, Stargardt disease, and cone dystrophy are characterized by the development of central scotoma which reducing fixation stability.40 Most of the studies related to acoustic biofeedback training include patients with AMD and Stargardt disease. To our knowledge, there is only one study evaluated the efficacy of biofeedback training in patients with cone dystrophy.40 In that study, which included five patients with central scotoma, one with cone dystrophy, an increase in visual acuity, fixation stability, retinal sensitivity, and reading speed was found after training. When we evaluate the groups separately, unlike the AMD and Stargardt disease patients we did not find a statistically significant change in the group of patients with cone dystrophy. Cone dystrophy has been demonstrated to cause dense central scotoma in some cases. Visual acuity and fixation stability in the eyes with central scotoma were worse than those with ring scotoma. All the patients with cone dystrophy included in this study had central scotoma and eccentric fixation. Ineffectiveness of training in patients with cone dystrophy may be related to the fact that the cone dystrophy is a generalized dystrophy and the cone cell functions of these patients are affected more than the patients with AMD and Stargardt disease. In the absence of sufficient functional cones, reorganization in the primary visual cortex, which plays a role in neural plasticity, cannot be achieved and PRL cannot develop with biofeedback.
Novel compound heterozygous mutation in the POC1B gene underlie peripheral cone dystrophy in a Chinese family
Published in Ophthalmic Genetics, 2018
Xin Jin, Lanlan Chen, Dajiang Wang, Yixin Zhang, Zehua Chen, Houbin Huang
POC1B (POC1B; OMIM 614784) was firstly cloned in 2008, it deduced 478-amino acid protein contains an N-terminal WD40 domain predicted to fold into a 7-bladed beta propeller and a C-terminal coiled-coil domain. It was predominantly expressed in the ciliary region of photoreceptor cells and synapses of the outer plexiform layer. Immunofluorescence analysis revealed POC1B localized in the periciliary region at the basal body and the adjacent centriole of the photoreceptor cilium, POC1 proteins are essential for both structure and stability of the basal body (6). Homozygous or compound heterozygous mutations in the POC1B gene were firstly found to be associated with CORD in 2014 (7). Subsequently, Durlu et al. reported a Turkish CORD family caused by novel POC1B mutation (8). Actually, POC1B mutations could cause autosomal-recessive COD or CORD. It was very interesting that the patients could occur the phenotype of cone dystrophy or CORD even in the same family, in which some were related to ages however the others were not.