Table of Contents

    Topic review

    Achromatopsia

    View times: 10
    Submitted by: Catherine Yang
    (This entry belongs to Entry Collection "MedlinePlus ")

    Definition

    Achromatopsia is a condition characterized by a partial or total absence of color vision. People with complete achromatopsia cannot perceive any colors; they see only black, white, and shades of gray. Incomplete achromatopsia is a milder form of the condition that allows some color discrimination.

    1. Introduction

    Achromatopsia also involves other problems with vision, including an increased sensitivity to light and glare (photophobia), involuntary back-and-forth eye movements (nystagmus), and significantly reduced sharpness of vision (low visual acuity). Affected individuals can also have farsightedness (hyperopia) or, less commonly, nearsightedness (myopia). These vision problems develop in the first few months of life.

    Achromatopsia is different from the more common forms of color vision deficiency (also called color blindness), in which people can perceive color but have difficulty distinguishing between certain colors, such as red and green.

    2. Frequency

    Achromatopsia affects an estimated 1 in 30,000 people worldwide. Complete achromatopsia is more common than incomplete achromatopsia.

    Complete achromatopsia occurs frequently among Pingelapese islanders, who live on one of the Eastern Caroline Islands of Micronesia. Between 4 and 10 percent of people in this population have a total absence of color vision.

    3. Causes

    Achromatopsia results from changes in one of several genes: CNGA3, CNGB3, GNAT2, PDE6C, or PDE6H. A particular CNGB3 gene mutation underlies the condition in Pingelapese islanders.

    Achromatopsia is a disorder of the retina, which is the light-sensitive tissue at the back of the eye. The retina contains two types of light receptor cells, called rods and cones. These cells transmit visual signals from the eye to the brain through a process called phototransduction. Rods provide vision in low light (night vision). Cones provide vision in bright light (daylight vision), including color vision.

    Mutations in any of the genes listed above prevent cones from reacting appropriately to light, which interferes with phototransduction. In people with complete achromatopsia, cones are nonfunctional, and vision depends entirely on the activity of rods. The loss of cone function leads to a total lack of color vision and causes the other vision problems. People with incomplete achromatopsia retain some cone function. These individuals have limited color vision, and their other vision problems tend to be less severe.

    Some people with achromatopsia do not have identified mutations in any of the known genes. In these individuals, the cause of the disorder is unknown. Other genetic factors that have not been identified likely contribute to this condition.

    4. Inheritance

    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.

    5. Other Names for This Condition

    • achromatism

    • rod monochromatism

    • total color blindness

    The entry is from https://medlineplus.gov/genetics/condition/achromatopsia

    References

    1. Chang B, Grau T, Dangel S, Hurd R, Jurklies B, Sener EC, Andreasson S, DollfusH, Baumann B, Bolz S, Artemyev N, Kohl S, Heckenlively J, Wissinger B. Ahomologous genetic basis of the murine cpfl1 mutant and human achromatopsialinked to mutations in the PDE6C gene. Proc Natl Acad Sci U S A. 2009 Nov17;106(46):19581-6. doi: 10.1073/pnas.0907720106.
    2. Deeb SS. The molecular basis of variation in human color vision. Clin Genet.2005 May;67(5):369-77. Review.
    3. Kohl S, Baumann B, Rosenberg T, Kellner U, Lorenz B, Vadalà M, Jacobson SG,Wissinger B. Mutations in the cone photoreceptor G-protein alpha-subunit geneGNAT2 in patients with achromatopsia. Am J Hum Genet. 2002 Aug;71(2):422-5.
    4. Kohl S, Coppieters F, Meire F, Schaich S, Roosing S, Brennenstuhl C, Bolz S,van Genderen MM, Riemslag FC; European Retinal Disease Consortium, Lukowski R,den Hollander AI, Cremers FP, De Baere E, Hoyng CB, Wissinger B. A nonsensemutation in PDE6H causes autosomal-recessive incomplete achromatopsia. Am J HumGenet. 2012 Sep 7;91(3):527-32.
    5. Kohl S, Hamel C. Clinical utility gene card for: Achromatopsia - update 2013. Eur J Hum Genet. 2013 Nov;21(11). doi: 10.1038/ejhg.2013.44.
    6. Kohl S, Jägle H, Wissinger B, Zobor D. Achromatopsia. 2004 Jun 24 [updated2018 Sep 20]. In: Adam MP, Ardinger HH, Pagon RA, Wallace SE, Bean LJH, Stephens K, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University ofWashington, Seattle; 1993-2020. Available fromhttp://www.ncbi.nlm.nih.gov/books/NBK1418/
    7. Kohl S, Marx T, Giddings I, Jägle H, Jacobson SG, Apfelstedt-Sylla E, Zrenner E, Sharpe LT, Wissinger B. Total colourblindness is caused by mutations in thegene encoding the alpha-subunit of the cone photoreceptor cGMP-gated cationchannel. Nat Genet. 1998 Jul;19(3):257-9.
    8. Sundin OH, Yang JM, Li Y, Zhu D, Hurd JN, Mitchell TN, Silva ED, Maumenee IH. Genetic basis of total colourblindness among the Pingelapese islanders. NatGenet. 2000 Jul;25(3):289-93.
    9. Thiadens AA, den Hollander AI, Roosing S, Nabuurs SB, Zekveld-Vroon RC, CollinRW, De Baere E, Koenekoop RK, van Schooneveld MJ, Strom TM, van Lith-VerhoevenJJ, Lotery AJ, van Moll-Ramirez N, Leroy BP, van den Born LI, Hoyng CB, CremersFP, Klaver CC. Homozygosity mapping reveals PDE6C mutations in patients withearly-onset cone photoreceptor disorders. Am J Hum Genet. 2009 Aug;85(2):240-7.doi: 10.1016/j.ajhg.2009.06.016.
    10. Thiadens AA, Slingerland NW, Roosing S, van Schooneveld MJ, van Lith-VerhoevenJJ, van Moll-Ramirez N, van den Born LI, Hoyng CB, Cremers FP, Klaver CC. Geneticetiology and clinical consequences of complete and incomplete achromatopsia.Ophthalmology. 2009 Oct;116(10):1984-9.e1. doi: 10.1016/j.ophtha.2009.03.053.
    More
    1. Please check and comment entries here.