39.1 Features
Congenital stationary night blindness (CSNB) encompasses many disorders that have a spectrum of clinical and electrophysiologic findings as well as molecular causes. The gene associations are as follows:
CSNB1 (complete):
X-linked (NYX) (▶ Fig. 39.1).
Autosomal recessive (GRM6, TRPM1, GPR179, LRIT3).
CSNB2 (incomplete):
X-linked (CACNA1F) (▶ Fig. 39.2).
Autosomal recessive (CABP4, CACNA2D4).
Riggs:
Autosomal dominant (RHO, GNAT1, PDE6B).
Autosomal recessive (SLC24A1, GNAT1).
CSNB fundus with abnormalities:
Autosomal recessive (Oguchi [▶ Fig. 39.3]: SAG, GRK1; fundus albipunctatus [▶ Fig. 39.4]: RLBP1, RPE65, RDH5).
Fig. 39.1 CSNB1 (complete)—NYX. A 10-year-old boy with a history of nystagmus, strabismus, and nyctalopia. His best corrected visual acuity is 20/50 in the right eye and 20/63 in the left with myopic correction of –9.00 + 1.75 × 045 OD and –5.00 + 1.75 × 160 OS. (a) His visual field is full on Goldmann testing and fundus examination is normal. Full-field ERG demonstrates the electronegative waveform in response to bright flash (DA3) and no measurable response to a dim stimulus (DA0.01). (b) Under photopic conditions, the LA3 response has a distinct flattened trough followed by a sharp rising late response that produces a characteristic sawtooth appearance to 30-Hz flicker. Genetic testing revealed a mutation in NYX.
Fig. 39.2 CSNB2 (incomplete)—CACNA1F. A 16-year-old boy with no history of nyctalopia or nystagmus. His best corrected visual acuity is 20/80 in the right eye and 20/40 in the left with myopic correction of –17.25 + 4.00 × 089 OD and –15.50 + 1.75 × 119 OS. His visual field was full on Goldmann testing and color vision normal. (a) Fundus exam demonstrates myopic changes. Full-field ERG: Under scotopic conditions, the dim flash response (DA0.01) is reduced but clearly present, and the bright flash response (DA3) demonstrates the electronegative waveform. (b) The photopic ERG (LA3) is barely detectable and there is no measurable 30-Hz flicker ERG. Patient ERG responses are truncated at 10 to 150 ms due to blinks following the flash. Genetic testing revealed a mutation in CACNA1F. (Courtesy of Brian Brooks, NIH).
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