Question: When and how do you know when you have congenital night blindness?

Reference:
 Autosomal recessive congenital stationary night blindness autosomal recessive complete congenital stationary night blindness autosomal recessive incomplete congenital stationary night blindness Description Autosomal recessive congenital stationary night blindness is a disorder of the retina, which is the specialized tissue at the back of the eye that detects light and color. People with this condition typically have difficulty seeing and distinguishing objects in low light (night blindness). For example, they may not be able to identify road signs at night or see stars in the night sky. They also often have other vision problems, including loss of sharpness (reduced acuity), nearsightedness (myopia), involuntary movements of the eyes (nystagmus), and eyes that do not look in the same direction (strabismus). The vision problems associated with this condition are congenital, which means they are present from birth. They tend to remain stable (stationary) over time. Frequency Autosomal recessive congenital stationary night blindness is likely a rare disease; however, its prevalence is unknown. Causes Mutations in several genes can cause autosomal recessive congenital stationary night blindness. Each of these genes provide instructions for making proteins that are found in the retina. These proteins are involved in sending (transmitting) visual signals from cells called rods, which are specialized for vision in low light, to cells called bipolar cells, which relay the signals to other retinal cells. This signaling is an essential step in the transmission of visual information from the eyes to the brain. Mutations in two genes, GRM6 and TRPM1, cause most cases of this condition. These genes provide instructions for making proteins that are necessary for bipolar cells to receive and relay signals. Mutations in other genes involved in the same bipolar cell signaling pathway are likely responsible for a small percentage of cases of autosomal recessive congenital stationary night blindness. Gene mutations that cause autosomal recessive congenital stationary night blindness disrupt the transmission of visual signals between rod cells and bipolar cells or interfere with the bipolar cells' ability to pass on these signals. As a result, visual information received by rod cells cannot be effectively transmitted to the brain, leading to difficulty seeing in low light. The cause of the other vision problems associated with this condition is unclear. It has been suggested that the mechanisms that underlie night blindness can interfere with other visual systems, causing myopia, reduced visual acuity, and other impairments. Some people with autosomal recessive congenital stationary night blindness have no identified mutation in any of the known genes. The cause of the disorder in these individuals is unknown. Inheritance Pattern This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. Sources for This Page Audo I, Bujakowska K, Orhan E, Poloschek CM, Defoort-Dhellemmes S, Drumare I, Kohl S, Luu TD, Lecompte O, Zrenner E, Lancelot ME, Antonio A, Germain A, Michiels C, Audier C, Letexier M, Saraiva JP, Leroy BP, Munier FL, Mohand-Said S, Lorenz B, Friedburg C, Preising M, Kellner U, Renner AB, Moskova-Doumanova V, Berger W, Wissinger B, Hamel CP, Schorderet DF, De Baere E, Sharon D, Banin E, Jacobson SG, Bonneau D, Zanlonghi X, Le Meur G, Casteels I, Koenekoop R, Long VW, Meire F, Prescott K, de Ravel T, Simmons I, Nguyen H, Dollfus H, Poch O, Leveillard T, Nguyen-Ba-Charvet K, Sahel JA, Bhattacharya SS, Zeitz C. Whole-exome sequencing identifies mutations in GPR179 leading to autosomal-recessive complete congenital stationary night blindness. Am J Hum Genet. 2012 Feb 10;90(2):321-30. doi: 10.1016/j.ajhg.2011.12.007. Erratum in: Am J Hum Genet. 2012 Jul 13;91(1):209. 

Answer: People with congenital stationary night blindness  typically experience night blindness and other vision problems, including loss of sharpness (reduced visual acuity), severe nearsightedness (myopia),  involuntary movements of the eyes (nystagmus), and eyes that do not look in the same direction (strabismus).  These vision problems are usually evident at birth, and tend to be stable (stationary) over time.