The diagnostic usefulness of the negative electroretinogram

Review: Clinical findings and genetic characterization of children affected with X-linked retinoschisis in the Spanish population

X-linked retinoschisis (XLRS) is an inherited retinal disorder due to mutations in retinoschisin 1, characterized by impaired central vision secondary to parafoveal cystic cavities and visual field loss by splitting through the retinal nerve fibre layer in the peripheral retina. It is the leading cause of juvenile macular degeneration in males, and currently there is no approved treatment but carbonic anhydrase inhibitors can be used. A retrospective review of the medical records of 17 children with confirmed XLRS seen in the Paediatric Ophthalmology Department of La Paz University Hospital from the 1st of January 2009 to the 1st of June of 2023 was conducted. Complete ophthalmological studies, genetic testing and full-field electroretinogram were performed. Topical brinzolamide was given to patients with foveoschisis, adding oral acetazolamide in those who did not improve with topical treatment alone or with very extensive foveoschisis at diagnosis. Surgical treatment was performed in retinal detahment (RD) or in no clearing hemovitreous cases. Mean age at diagnosis was 5,86 years and the most common reason for consultation was strabismus, followed by RD. The most frequently affected retinal later on Optic coherence tomography was the inner nuclear layer and throughout the follow-up we observed a decrease in central macular thickness. We found some genotype-phenotype correlation in our series and more severe phenotypes if the first amino acid of the protein is affected or in frameshift mutations. We found that medical treatment (topical and oral) improves foveoschisis, and that surgery shows poor outcomes, especially in younger patients.

Visual impairment induced by prosthetic cobaltism

The case of a 68-year-old patient with visual loss secondary to prosthetic cobaltism is reported. The degeneration of the metallic hip prosthesis can produce a systemic absorption of cobalt with cardiac, neurological, endocrine, auditory, and visual manifestations. The diagnostic suspicion is confirmed by serum cobalt measurements. Treatment with early surgery and chelating agents can lead to improvement of the visual, and the other disorders.

Diagnosis of an X-linked type 2 congenital stationary night blindness using electroretinography and CACNA1F sequencing

A 4-year-old boy, with no history of relevance, presented with bilateral visual impairment, more so in scotopic conditions, and did not improve with optical correction. No significant funduscopic abnormalities were seen, leading to a suspicion of retinal dystrophy. Sequencing of the CACNA1F gene detected the c.3081C>A (p.Tyr1027Ter) mutation, which had occurred de novo in the patient's mother. This mutation, in the aforementioned clinical context, and with a compatible electronegative pattern, establishes the diagnosis of X-linked type 2 congenital stationary night blindness. Electrophysiology and genetic testing should be part of the diagnostic protocol for any unexplained loss of vision in children. The description, nomenclature and classification of hereditary retinal dystrophies based on their genotypic and electroretinograpic characteristics, avoids diagnostic errors due to their usual clinical and phenotypic overlap.

X-linked juvenile retinoschisis: phenotypic and genetic characterization

Juvenile X-linked retinoschisis (XLRS, MIM#312700) belongs to a group of the vitreoretinal dystrophies. We aimed to describe the phenotype-genotype correlation of three XLRS cases in juveniles with different novel mutations from the Lithuanian population. The patients demonstrated macular retinoschisis and typical cyst-like cavities on spectral-domain optical coherence tomography (SD-OCT) images. The mean central foveal thickness was 569.7 µm. Two patients presented with peripheral retinoschisis. Flash electroretinogram demonstrated a reduced b/a ratio (<1.0) in all patients. RS1 (NM_000330.3) gene coding exons Sanger sequencing was performed. RS1 c.599G>T (p.R200L) mutation was detected in one case, showing to be pathogenic in silico analysis. c. (92_97) insC (p.W33fs) mutation was identified for another patient, indicating the variant is possibly damaging in silico analysis. The third case was identified with a pathogenic mutation c.422C>G (p.R141H), HGMD CM981753. These are the first cases of XLRS in the Lithuanian population confirmed by molecular genotyping. Presented patients had a different genotype but similar phenotypic traits.