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PubMed This is a summary of 13 peer-reviewed journal articles Updated
Ophthalmology

The Science of Sight: Biology & Genetics

At a Glance

Achromatopsia is an inherited eye condition caused by gene mutations that prevent color-sensing cone cells from working properly. Inherited as an autosomal recessive trait, identifying a child's specific gene mutation and subtype helps determine the best low-vision aids and gene therapy options.

To understand Achromatopsia, it helps to think of the eye like a camera. For most people, the camera has two types of “sensors”: one for high-definition color video (the cones) and one for grainy, black-and-white night vision (the rods) [1]. In a child with Achromatopsia, the “color sensors” are either turned off or not functioning correctly, leaving them to navigate the world using only their night-vision sensors [2][1].

The Genetic Blueprint

Achromatopsia is an autosomal recessive condition [3]. This means a child must inherit one changed gene from each parent to have the condition. Because it is recessive, parents who carry the gene typically have completely normal vision. However, there is a 25% chance of the condition occurring in any future pregnancies. Speaking with a Genetic Counselor is highly recommended to understand these risks [4].

Scientists have identified six specific genes that, when mutated, cause the “circuitry” of the cone cells to fail:

  1. CNGB3 & CNGA3: These are the most common causes, accounting for about 80% of cases [3]. They provide instructions for building “gates” (ion channels) that let signals flow through the cone cells [5][6].
  2. GNAT2, PDE6C, & PDE6H: These genes are responsible for the chemical chain reaction (the phototransduction cascade) that happens when light hits a cone cell [7][8].
  3. ATF6: This gene is unique because it handles “quality control” within the cell. When it is mutated, the cone cells may struggle to fold proteins correctly, leading to cell stress [9][10].

Complete vs. Incomplete Achromatopsia

Not every child with Achromatopsia experiences the same level of vision. Doctors generally divide the condition into two main subtypes:

  • Complete Achromatopsia: In this form, there is a total lack of cone function [1]. These children see the world in shades of gray, black, and white. Their visual acuity is typically 20/200 or less, and they experience the most significant light sensitivity [1][11].
  • Incomplete Achromatopsia: This is a milder form where some cone cells still function [12]. These children may be able to perceive some colors and often have better visual acuity than those with the complete form [11].

Why the Subtype Matters

Understanding whether your child has the complete or incomplete form—and which specific gene is involved—is vital for the future. For example, some gene therapy trials specifically target mutations in the CNGA3 or CNGB3 genes [13][6]. Knowing your child’s genetic “subtype” is the key to participating in research and understanding how their vision may respond to different types of filters and low-vision aids.

Common questions in this guide

How is Achromatopsia inherited?
Achromatopsia is an autosomal recessive condition, meaning a child must inherit one mutated gene from each parent. Parents who carry the gene usually have normal vision themselves but have a 25% chance of passing the condition to their child in any future pregnancy.
What genes cause Achromatopsia?
There are six known genes that can cause the condition when mutated: CNGB3, CNGA3, GNAT2, PDE6C, PDE6H, and ATF6. The most common are CNGB3 and CNGA3, which account for roughly 80% of all cases.
What is the difference between complete and incomplete Achromatopsia?
In complete Achromatopsia, the eye's color-sensing cone cells do not function at all, resulting in total color blindness and significant light sensitivity. Incomplete Achromatopsia is a milder form where some cone cells still work, allowing for some color perception and often better visual sharpness.
Why is genetic testing important for Achromatopsia?
Knowing the specific gene mutation tells doctors which biological pathway is affected. This information is vital for understanding what low-vision aids might work best and can determine if your child is eligible for clinical research, such as gene therapy trials.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Which of the six genes (CNGB3, CNGA3, GNAT2, PDE6C, PDE6H, or ATF6) was identified in my child's genetic test?
  2. 2.Based on my child's clinical exams, do they have the 'complete' or 'incomplete' form of Achromatopsia?
  3. 3.Can you refer us to a Genetic Counselor to discuss the recurrence risks for our family?
  4. 4.Does the specific gene mutation my child has carry a higher risk of progressive changes over time, or is it typically stable?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (13)
  1. 1

    Mutation spectrum and clinical investigation of achromatopsia patients with mutations in the GNAT2 gene.

    Felden J, Baumann B, Ali M, et al.

    Human mutation 2019; (40(8)):1145-1155 doi:10.1002/humu.23768.

    PMID: 31058429
  2. 2

    Intact high-level visual functions in congenital rod-monochromacy.

    Shabat S, McKyton A, Elul D, et al.

    Frontiers in neuroscience 2024; (18()):1418916 doi:10.3389/fnins.2024.1418916.

    PMID: 39399382
  3. 3

    Comprehensive variant spectrum of the CNGA3 gene in patients affected by achromatopsia.

    Solaki M, Baumann B, Reuter P, et al.

    Human mutation 2022; (43(7)):832-858 doi:10.1002/humu.24371.

    PMID: 35332618
  4. 4

    Phenotype and genotype of 15 Saudi patients with achromatopsia: A case series.

    Danish E, Alhashem A, Aljehani R, et al.

    Saudi journal of ophthalmology : official journal of the Saudi Ophthalmological Society 2023; (37(4)):301-306 doi:10.4103/sjopt.sjopt_108_23.

    PMID: 38155673
  5. 5

    Inherited macular degeneration-associated mutations in CNGB3 increase the ligand sensitivity and spontaneous open probability of cone cyclic nucleotide-gated channels.

    Meighan PC, Peng C, Varnum MD

    Frontiers in physiology 2015; (6()):177 doi:10.3389/fphys.2015.00177.

    PMID: 26106334
  6. 6

    Structure-function analysis of CNGA3-associated achromatopsia patient variants complements clinical genomics in pathogenicity determination.

    Rasmussen DK, Sun YJ, Franco JA, et al.

    Orphanet journal of rare diseases 2025; (20(1)):261 doi:10.1186/s13023-025-03792-3.

    PMID: 40448196
  7. 7

    Monogenic Retinal Diseases Associated With Genes Encoding Phototransduction Proteins: A Review.

    Wong WM, Mahroo OA

    Clinical & experimental ophthalmology 2025; (53(3)):260-280 doi:10.1111/ceo.14511.

    PMID: 40013354
  8. 8

    Mutations in the gene PDE6C encoding the catalytic subunit of the cone photoreceptor phosphodiesterase in patients with achromatopsia.

    Weisschuh N, Stingl K, Audo I, et al.

    Human mutation 2018; (39(10)):1366-1371 doi:10.1002/humu.23606.

    PMID: 30080950
  9. 9

    CNGB3 mutation spectrum including copy number variations in 552 achromatopsia patients.

    Mayer AK, Van Cauwenbergh C, Rother C, et al.

    Human mutation 2017; (38(11)):1579-1591 doi:10.1002/humu.23311.

    PMID: 28795510
  10. 10

    Molecular and Clinical Characterization of CNGA3 and CNGB3 Genes in Brazilian Patients Affected with Achromatopsia.

    Amaral RAS, Motta FL, Zin OA, et al.

    Genes 2023; (14(6)) doi:10.3390/genes14061296.

    PMID: 37372476
  11. 11

    A new mutation in the PDE6C gene in achromatopsia.

    Jiménez-Siles L, Zamorano-Martín F, García-Lorente M, et al.

    European journal of ophthalmology 2023; (33(4)):NP133-NP137 doi:10.1177/11206721221093023.

    PMID: 35422133
  12. 12

    Differences in ocular findings in two siblings: one with complete and other with incomplete achromatopsia.

    Ueno S, Nakanishi A, Sayo A, et al.

    Documenta ophthalmologica. Advances in ophthalmology 2017; (134(2)):141-147 doi:10.1007/s10633-017-9577-y.

    PMID: 28197754
  13. 13

    One down but many more to go: the state of gene therapy for inherited retinal disease.

    Tan TE, Sun CZY, Poh SSJ, et al.

    Regenerative medicine 2025; (20(10)):509-526 doi:10.1080/17460751.2025.2571360.

    PMID: 41054259

This page provides educational information about the biology and genetics of Achromatopsia. Always consult a genetic counselor or pediatric ophthalmologist to discuss your child's specific genetic report and diagnosis.

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