Photopic ON- and OFF-responses in complete type of congenital stationary night blindness in relation to stimulus intensity

Abstract

The complete type of congenital stationary night blindness (complete CSNB) is a retinal disorder where the ON-response b-wave of the photopic electroretinogram is reduced, while the ON-response a-wave and OFF-response d-wave are preserved. These findings are related to ON-bipolar cell dysfunction, whereas the effects of myopia, which is usually associated with complete CSNB, have not been studied yet. The aim was to investigate ON-bipolar cell dysfunction in complete CSNB with variable-intensity stimuli, while excluding effects of myopia. ON- and OFF-responses were recorded from six complete CSNB patients, 10 control subjects (no refractive error; emmetropic control group) and 14 myopic subjects with similar refractive error and axial length as those with complete CSNB (myopic control group). Responses were elicited with stimulus intensities from 0.4 to 2.1 log cd s/m2 on a 20 cd/m2 background. Stimulus/response (S/R) functions were fitted to the Naka-Rushton equation and statistically evaluated. In complete CSNB, the S/R function of the a-wave measured at the time corresponding to the controls showed a lower Vmax than for the emmetropic controls, while all parameters were similar to the myopic control group. The b- and d-wave S/R functions of the complete CSNB group were similarly different to both control groups--for the b-wave, the Vmax and n were significantly lower, and for the d-wave, the sigma was significantly higher. These findings suggest that in complete CSNB, dysfunction of ON-bipolar cells influences the dynamics of the ON-response b-wave and OFF-response d-wave, independently of the effects of myopia.

Full-field electroretinogram response to increment and decrement stimuli

“…For example, the b-wave is either eliminated or reduced more than the d-wave in certain retinal diseases, including congenital stationary night blindness [27,[31][32][33][34][35], malignant melanoma associated retinopathy [9,36,37], x-linked retinoschisis [17,38,39] x-linked retinitis pigmentosa [26] and phosphomannomutase deficiency [40]. Conditions in which the ERG d-wave is more reduced than the b-wave have been reported in few cases, but which had uncertain underlying etiology [33,41].…”

Quantifying the ON and OFF Contributions to the Flash ERG with the Discrete Wavelet Transform

“…The recording electrode (HK-loop 5 ) was hooked to the lower lid as previously reported elsewhere. 6,7 The reference and ground electrodes (Grass silver cup electrodes; Grass Technologies, West Warwick, RI) were pasted at the level of the external canthus and on the forehead, respectively. The pupils were maximally dilated with 1% tropicamide (Mydriacyl; Alcon, Inc., Fort Worth, TX).…”

On and off responses of the photopic fullfield ERG in normal subjects and glaucoma patients

“…All significant results after correction for multiple testing are included. Observe the inverse scaling for the amplitudes of the a-wave and the PhNR on however, indicated that the PhNR can be attributed to activity in the inner retinal layers [7], [10], [18], [20][21][22][23], suggesting that the fullfield ERG can be of importance in glaucoma diagnosis. Stimulation in those studies was obtained with monitors, fullfield systems or specific LED set-ups.…”

“…The white light as used in our measurements could be an explanation for the observation in our study that the diagnostic value of the PhNR off is higher than the one of the PhNR on . More studies in different patient groups [22] are necessary to investigate the diagnostic utility of the long-flash ERG with white and colour stimulation.…”