Assessment of night vision problems in patients with congenital stationary night blindness.

Congenital Stationary Night Blindness (CSNB) is a retinal disorder caused by a signal transmission defect between photoreceptors and bipolar cells. CSNB can be subdivided in CSNB2 (rod signal transmission reduced) and CSNB1 (rod signal transmission absent). The present study is the first in which night vision problems are assessed in CSNB patients in a systematic way, with the purpose of improving rehabilitation for these patients. We assessed the night vision problems of 13 CSNB2 patients and 9 CSNB1 patients by means of a questionnaire on low luminance situations. We furthermore investigated their dark adapted visual functions by the Goldmann Weekers dark adaptation curve, a dark adapted static visual field, and a two-dimensional version of the "Light Lab". In the latter test, a digital image of a living room with objects was projected on a screen. While increasing the luminance of the image, we asked the patients to report on detection and recognition of objects. The questionnaire showed that the CSNB2 patients hardly experienced any night vision problems, while all CSNB1 patients experienced some problems although they generally did not describe them as severe. The three scotopic tests showed minimally to moderately decreased dark adapted visual functions in the CSNB2 patients, with differences between patients. In contrast, the dark adapted visual functions of the CSNB1 patients were more severely affected, but showed almost no differences between patients. The results from the "2D Light Lab" showed that all CSNB1 patients were blind at low intensities (equal to starlight), but quickly regained vision at higher intensities (full moonlight). Just above their dark adapted thresholds both CSNB1 and CSNB2 patients had normal visual fields. From the results we conclude that night vision problems in CSNB, in contrast to what the name suggests, are not conspicuous and generally not disabling.

Functional assessment of the regional distribution of disease in a cat model of hereditary retinal degeneration.

PURPOSE: To establish a method for the recording of multifocal electroretinograms (MF-ERGs) in animals under fundus control using a scanning-laser ophthalmoscope (SLO) and to analyze the spatial distribution of disease in a strain of Abyssinian cats with a recessively inherited rod-cone degeneration (ARCD). METHODS: Four normal and 12 Abyssinian cats at four different clinical stages of ARCD were examined with the RETIscan MF-ERG system using 61 hexagonal elements within a visual field of approximately 30 degrees radius. The stimulus pattern was generated by the green laser beam (515 nm) of a Heidelberg Engineering HRA SLO, whose power was reduced with a Schott long-pass filter allowing for simultaneous infrared fundus imaging. RESULTS: Topographical recordings could be obtained in all animals except one in stage 4. Amplitudes were minimal at the optic disc and had a slight maximum at the area centralis. Implicit times had a tendency to lower values in the central region, most pronounced in progressed stages of ARCD. The clinical stages of ARCD correlated with a successive generalized loss of amplitude and a rise in implicit time. Without a decrease in retinal illuminance, topographical landmarks like the optic disc were no longer detectable, pointing to stray light as a possible cause. CONCLUSIONS: It was demonstrated that topographical MF-ERG recordings can be obtained in an animal model under fundus control using SLO stimulation. The appearance of retinal landmarks was found to be dependent on sufficient attenuation of laser power. Because the changes in ARCD are more patchy than in human retinitis pigmentosa (RP), a generalized loss of function was detected. However, like in RP, the central area was found to retain a better function than the periphery, especially in later stages of the disease. In summary, fundus controlled methods like the one presented will greatly improve the reliability of MF-ERG in future research on glaucoma, transplantation studies, and evaluation of gene therapy.