the eye blog
EYE CARE INFO & UPDATES
Colour vision deficiency (CVD), or otherwise called colour blindness, is a fairly common condition in the population. Around 8% of males (1 in 12) have some level of deficiency in colour matching, and around 0.5% of females (1 in 200). It is mostly a hereditary eye condition through a gene carried on the X chromosome (passing from mother's side), resulting in an imbalance of the numbers and densities of colour receptor cells (cones) in an individual's retina. Our eyes have three types of cone photoreceptors cells (green, red and blue) to detect colour information in our vision.
There are two main types of hereditary colour vision deficiency: deutan (green cone receptor deficient) or proton (red cone deficient). A third type, tritan (blue cone deficient), is usually an acquired rather than congenital condition and is very rare. In each of these types, an individual may have a mild deficiency (almost normal), a moderate or a severe colour vision defect (significant difficulty in differentiating between certain shades of colours).
At Eyecare Concepts, in addition to the standard Ishihara colour vision screening test (coloured dots forming numbers on a page) that most optometrists use, we have a more detailed colour vision test known as the Farnsworth D-15 colour matching test. While the common Ishihara screening tool can detect the presence of a colour vision defect, it does not differentiate between the type of colour defect or its severity.
With the Farnsworth D-15 test — which involves matching a series of coloured discs from one to the next in similarity — we can assess the type of colour vision deficiency (deutan, protan or tritan) and also grade the severity of the deficiency between normal-mild, medium or severe. This is important when colour vision assessment is required for certain vocations or career choices.
If you or your child has a colour vision deficiency, or there is a known family history, see us for a more comprehensive colour vision assessment test.
FAMILY & CHILDREN'S OPTOMETRIST — MELBOURNE
Philip Cheng - B.Optom (Melb) Ocular Therapeutics (GCOT). Optometrist at Eyecare Concepts Kew East, Melbourne. An experienced eye care & contact lens practitioner with expertise in myopia control & orthokeratology.