Rod densitometry in congenital stationary night blindness

Abstract

Rod densities were measured in ten patients with congenital stationary night blindness (CSNB) using the Utrecht densitometer. In five patients rod density was within the range observed in a group of control subjects. One of these patients reached a normal rod two-way density after a prolonged regeneration time. In five patients with different hereditary patterns of CSNB we found decreased amounts of rhodopsin. These observations deviate from the findings on four CSNB patients hitherto described in the literature, where normal concentrations and kinetics of rhodopsin were found. We observed no relationship between the age of CSNB patients and mode of rhodopsin kinetics. No inconsistencies between rod densitometry and electro-retinography were revealed. The different electroretinography patterns were not helpful in predicting the densitometric responses in CSNB. The present results included, five of fourteen CSNB patients ever studied with the technique of retinal densitometry show abnormal rhodopsin kinetics. We propose a schema of CSNB subtyping based on the different rhodopsin kinetics.

A computational model of the amplitude and implicit time of the b-wave of the human ERG

“…This should result in a large decrease in INL sensitivity (an increase in a P2 ) for CSNB patients (see references in Hood & Greenstein, 1990). More recently, it has been shown that some CSNB patients have reduced rod pigment content as well (Keunen et al, 1988). This would produce a decrease in receptor sensitivity (an increase in ff P3 ) for these patients.…”

Autosomal dominant stationary night‐blindness A large family rediscovered

“…Dark adaptation curves with similar diphasic appearance in night-blind individuals are presented, among others, by Keunen et al (1988). These cases, indeed, were presumed to be autosomal recessive types and incomplete types of CSNB.…”

“…In incomplete CSNB (Miyake et al 1986) the electrical cone characteristics are depressed, especially in the dark adapted state (Miyake et al 1987). Dark adaptation curves with similar diphasic appearance in night-blind individuals are presented, among others, by Keunen et al (1988). These cases, indeed, were presumed to be autosomal recessive types and incomplete types of CSNB.…”

“…Clinical subclassifications have been proposed according to electroretinographic characteristics into a Schubert-Bornschein type and a Riggs type (Auerbach et al 1969). Keunen et al (1988), using densitometric measurements, have demonstrated a group of CSNB with normal rho-dopsin kinetics (type I) and a group with impaired rhodopsin kinetics (type 11). Miyake et al (1986) proposed a subclassification into a complete CSNB type and an incomplete CSNB type.…”

“…Yet, we conclude that ERG's from night-blind persons belonging to the Rambusch family seem to be similar to ERG's from night-blind persons from other well-documented cases of autosomal dominant transmission. Some pedigrees with dominantly transmitted CSNB from which electroretinographical data are published, are characterized by sole maternal transmission, raising the suspicion that some of these cases might constitute examples of mitochondrial dysfunction (Francois et al 1965;Keunen et al 1988;Noble et al 1990). This interpretation is consistent with our knowledge of the key role held by mitochondrial enzyme systems in energy metabolism.…”