Robert C. Polomeno

Usher Syndrome 1D and Nonsyndromic Autosomal Recessive Deafness DFNB12 Are Caused by Allelic Mutations of the Novel Cadherin-Like Gene CDH23

Genes causing nonsyndromic autosomal recessive deafness (DFNB12) and deafness associated with retinitis pigmentosa and vestibular dysfunction (USH1D) were previously mapped to overlapping regions of chromosome 10q21-q22. Seven highly consanguineous families segregating nonsyndromic autosomal recessive deafness were analyzed to refine the DFNB12 locus. In a single family, a critical region was defined between D10S1694 and D10S1737, approximately 0.55 cM apart. Eighteen candidate genes in the region were sequenced. Mutations in a novel cadherin-like gene, CDH23, were found both in families with DFNB12 and in families with USH1D. Six missense mutations were found in five families with DFNB12, and two nonsense and two frameshift mutations were found in four families with USH1D. A northern blot analysis of CDH23 showed a 9.5-kb transcript expressed primarily in the retina. CDH23 is also expressed in the cochlea, as is demonstrated by polymerase chain reaction amplification from cochlear cDNA.

Mutations in NYX, encoding the leucine-rich proteoglycan nyctalopin, cause X-linked complete congenital stationary night blindness

During development, visual photoreceptors, bipolar cells and other neurons establish connections within the retina enabling the eye to process visual images over approximately 7 log units of illumination. Within the retina, cells that respond to light increment and light decrement are separated into ON- and OFF-pathways. Hereditary diseases are known to disturb these retinal pathways, causing either progressive degeneration or stationary deficits. Congenital stationary night blindness (CSNB) is a group of stable retinal disorders that are characterized by abnormal night vision. Genetic subtypes of CSNB have been defined and different disease actions have been postulated. The molecular bases have been elucidated in several subtypes, providing a better understanding of the disease mechanisms and developmental retinal neurobiology. Here we have studied 22 families with complete X-linked CSNB (CSNB1; MIM 310500; ref. 4) in which affected males have night blindness, some photopic vision loss and a defect of the ON-pathway. We have found 14 different mutations, including 1 founder mutation in 7 families from the United States, in a novel candidate gene, NYX. NYX, which encodes a glycosylphosphatidyl (GPI)-anchored protein called nyctalopin, is a new and unique member of the small leucine-rich proteoglycan (SLRP) family. The role of other SLRP proteins suggests that mutant nyctalopin disrupts developing retinal interconnections involving the ON-bipolar cells, leading to the visual losses seen in patients with complete CSNB.

Prevalence and Severity of Hypertensive Retinopathy in Children

The National High Blood Pressure Education Program (NHBPEP) report recommends a retinal exam seeking evidence of target organ damage in hypertensive children. This study aimed to determine the prevalence and severity of hypertensive retinopathy among hypertensive children, evaluated by pediatric ophthalmologists in the “real world” clinical setting using direct ophthalmoscopy. The authors retrospectively reviewed the medical records of the 83 children diagnosed with hypertension by a pediatric nephrologist between 1999 and 2006. Of the 35 children examined by an ophthalmologist within 12 months of the diagnosis of hypertension, only 3 (8.6%; 95% CI, 1.8%-23.1%) were diagnosed with hypertensive retinopathy. Despite the fact that those selected for retinal examination were likely at higher risk for retinopathy, the prevalence of retinopathy was low, and only mild abnormalities were detected. Given the lack of evidence linking mild retinal abnormalities with adverse outcomes, the NHBPEP recommendation for retinal examinations in hypertensive children should be reconsidered.

Herpes Simplex Keratitis and Amblyopia

Herpes simplex keratitis can cause severe loss of vision in children. The findings in five children show that amblyopia is caused by stimulus deprivation and/or anisometropia. Early medical treatment, occlusion therapy, and frequent refractions are crucial for a good visual prognosis.

The effect of diphenylhydantoin on the electroretinogram

Acute administration of diphenylhydantoin (DPH) in rabbits produces a significant increase in the amplitude of the a-wave. A marked increase in the amplitude of the b-wave is also noted but the time course is slower than that for the a-wave. While in controls the oscillatory potential (OP) recordings essentially consist of three major types, recordings taken after DPH injection consist of one major OP (OP2), which appears to be a result of the fusion of the original OP2 with another OP produced by the DPH injection. A similar blend of OPs was also seen in ERGs recorded from three human subjects on DPH therapy.

Acquired restrictive strabismus and high axial myopia: diagnosis and management

OBJECTIVEnThis paper documents the clinical, ultrasound, magnetic resonance imaging (MRI), and anatomic characteristics of 6 patients with esohypotropia and high axial myopia. The results of strabismus surgery performed on these patients are evaluated.nnnSTUDY DESIGNnRetrospective cohort study.nnnPARTICIPANTSnSix patients with esohypotropia and high axial myopia were selected from the practice of the second author (Michael Flanders).nnnMETHODSnWe extracted the history and data from the preoperative and postoperative ophthalmic and orthoptic examinations, recorded the surgical procedures, and tabulated the postoperative results. A- and B-scans, orbital MRI images, and photo documentation were obtained for all patients. Supramaximal recession and resection on the horizontal rectus muscles, using adjustable sutures, was performed in all patients. A surgical outcome was deemed successful if, in primary position, postoperative horizontal ocular alignment measured 15 prism diopters (PD) or less and (or) if diplopia was eliminated.nnnRESULTSnEchographic and MRI findings demonstrated an enlarged globe in all cases. Globe flattening on the orbital walls was found in 5 cases. Lateral rectus depression was visualized on MRI images in 4 cases. Surgical success was obtained in all patients. The average preoperative primary position esotropia measured 60 PD (25 to 90 PD) and the esodeviation after surgery was 7.0 PD (0 to 15 PD). Ductions were also improved.nnnCONCLUSIONSnDifferent surgical approaches to realignment of eyes with high myopia and esohypotropia have been attempted. In this study, supramaximal amounts of recession and resection on the rectus muscles provided satisfactory results.