Bardet−Biedl Syndrome
Dongyou Liu in 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).
Non-Organic Vision Loss
Vivek Lal in A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
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.
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.
Gene therapy for the treatment of X-linked retinitis pigmentosa
Published in Expert Opinion on Orphan Drugs, 2018
Cristina Martinez-Fernandez De La Camara, Anika Nanda, Anna Paola Salvetti, M. Dominik Fischer, Robert E. MacLaren
RP presents clinical variability in age of onset, progression of the disease, and secondary clinical manifestations. Generally, primary degeneration affects photoreceptor rods, causing night blindness as the first clinical manifestation. Degeneration advances from the periphery toward the fovea, progressively decreasing the visual field and leading to tunnel vision. In the end stages of a typical rod-cone dystrophy, cones are also affected, leading to the loss of visual acuity [2]. In some cases where the causative gene is expressed in cones and rods, patients can present with a cone rod dystrophy phenotype, in which visual acuity loss and peripheral rod loss occur synchronously. RP can also be syndromic, in which other organs are affected. The most common forms of syndromic RP are Usher syndrome, characterized by RP and hearing loss with or without vestibular dysfunction, and Bardet-Biedl syndrome, where other major signs are obesity, intellectual disability, polydactyly, and kidney abnormalities [3,4].
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.
Related Knowledge Centers
- Chromosome 17
- Color Vision
- Cone Cell
- Heredity
- Photoreceptor Cell
- Rod Cell
- Visual Acuity
- Visual Impairment
- Eye Disease
- Bardet–Biedl Syndrome