the eye blog

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.
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If this is you at work, you may have what is called Computer Vision Syndrome (CVS), or Digital Eye Strain.

​CVS is a common problem in our modern digital society where a large part of our days is spent staring at a computer monitor, on a laptop or tablet or using a smartphone, both at home and at work. CVS can affect up to 90% of people who spend more than 3 hours a day concentrating on digital devices.

Typical symptoms of CVS include headaches, blurred vision, sore eyes, red eyes, tiredness, neck pain, difficulty refocusing from near to far and occasionally could also include dizziness and double vision.

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​Why do we get Computer Vision Syndrome?

Prolonged periods of focusing on a near object causes the eye's focusing muscles to become tired. For some people when this happens their eyes start to lose focus up-close, making near vision blurry. And when they try to focus even harder to read their computer screen they can end up straining their eyes and getting a headache. Or they may lean forward towards their screen and getting neck pain from improper posture.

For other people, their far-distance vision can become blurred. This can occurs because their focusing system has become 'locked' at close-range, then when they look away into the distance their eyes are unable to relax, causing blurred vision. Some people can mistake this for 'short-sightedness' — where far-distance vision is always blurred relative to near — but in these cases it's actually the near work that causes the symptoms and far-distance glasses won't necessarily help. Some young adults, however, do develop true short-sightedness (myopia) from prolonged computer use. An experienced optometrist can distinguish between true short-sightedness and near-work-induced distance blur and recommend the most appropriate solution to the problem.

Staring at a computer screen can often also cause dry eye. This is because when we stare at a computer our blink rate is reduced. When we don't blink frequently enough our eye surface becomes dry. Common symptoms of dry eyes are redness, irritation and burning sensation. Some people experience watery eyes, thinking if their eyes are watering they can't be dry, when in fact the cause of the watery eyes is actually dry eyes, as strange as it may seem. When our eyes become too dry and irritated they can start to produce tears as a reflex response. Dry eye can also be exacerbated by environmental factors such as air conditioning in summer and heating in winter.
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How to get help for Computer Vision Syndrome?

​If you have symptoms of CVS, the first thing to do is to book an eye test with an experienced optometrist for a comprehensive assessment of your eyes' focusing and eye health. Sometimes it can be a simple focusing issue such as slight long-sightedness (increased focusing effort at near) or astigmatism (irregular eye surface curvature) that a pair of prescription glasses with anti-reflective coating will make a big improvement to your symptoms.

Often, a more specialised type of lens called an anti-fatigue lens will be what you need for your Computer Vision Syndrome. An anti-fatigue lens is like a mini-progressive lens with two power zones that help you relax your eyes when focusing up-close. Here at Eyecare Concepts, we offer the Essilor Eyezen and the Nikon Relaxsee​ anti-fatigue lenses, both specifically designed to relieve digital eye strain. The blue light protective coating of these lenses also help to reduce eye strain from brightly-lit digital devices. Our optometrist will recommend the optical solution tailored to your personal vision needs. Prescription glasses and anti-fatigue lenses are rebatable on your private health optical cover.

For individuals with dry eyes, we can also assess your dry eye condition with our special instrument that analyses the quality of your tears and how quickly your natural tear film evaporates in-between blinks. With this analysis we can treat your dry eye condition more effectively. As a therapeutically-endorsed optometrist we can prescribe medicated eye drop treatments if necessary for more severe cases of dry eye. And if you have oily or blocked tear glands we have in-office eyelid warming therapy to treat the underlying cause of your dry eyes.