Whilst there are many signs that may indicate the possible need for glasses, these five are the most common we experience in our clinics:
- Difficulty reading road signs & TV subtitles – if you’re far enough away from anything then you’ll most likely find it hard to see, but there’s a difference between just being too far away and experiencing blurred or distorted vision. Refractive error is a general term to describe the eye’s inability to refract (bend) light accurately to form a sharp image on the retina. It is the formation of this sharp image that is perceived as “clear” by our brains. There are three main types of refractive error: myopia (short-sightedness), astigmatism (angle based distortion), and hyperopia (long-sightedness). The first two are the main cause of blurred distance vision, however the third, despite its misleading lay-term implying good “long” vision, generally causes similar problems later in life when the ageing eye is unable to self-adjust for this error.
- Reading or computer work is hard – trying to read written print at a near range also has its challenges. Your eyes actually have to engage the accommodation (focus zoom) system. The closer you work to something the more work your accommodation system has to do. Generally speaking, virtually everyone over the age of 40 years will experience near range focusing problems due to a condition known as Presbyopia, caused by the hardening of the natural crystalline lens responsible for accommodation. Common symptoms include blurred vision at near range or having to hold reading material further away to see it clearly. In younger people, near range vision difficulties are commonly caused by excessive hyperopia, astigmatism, and binocular vision disorders (eye movement & focus coordination problems).
- You are constantly squinting – having to squint to see more clearly may indicate a number of problems. The strategy involves narrowing the gap between the eyelids to create a slit to peer through. This improves vision clarity via an optical phenomenon known as “depth of focus”. This is well known to photographers who utilise the phenomenon by narrowing the camera lens aperture to increase the range of clarity in a photo, rendering both near and distance objects clear simultaneously. The most common cause is refractive error. Squinting to see in the distance may be due to myopia, astigmatism or excessive hyperopia. At near range it is more likely to be due to hyperopia, presbyopia and binocular vision disorders, however astigmatism may also affect vision at this range.
Light emitted from computer screens can also contribute to glare, and squinting is a natural reaction to this. To combat glare, glasses can be prescribed with a selection of filters that may include anti-reflection coatings and tints.
- You have difficulty seeing in poorer light – if the lighting conditions are poor enough then it will become harder to see, however refractive error is also detrimental. People with myopia find that their distance vision problems worsen at night, whereas reading at near range becomes much harder with the onset of presbyopia, where low contrast situations make it difficult for accommodation to lock in focus clarity for extended periods.
- Frequent headaches – there are many causes of headache and sinister possibilities must first be excluded. Assuming all health issues and postural problems have been eliminated as a cause, it is possible that excessive focus stress may cause headaches. Generally these are experienced in the forehead and brow regions, usually after excessive periods of concentrated focusing at any distance. Working in poor light and regular squinting may also contribute to headaches. Once again this may be due to any refractive error, presbyopia, and binocular vision disorder.
Some people are highly susceptible to glare that may also result in headache symptoms. Examples of strategies to alleviate glare induced discomfort include the use of tinted glasses for outdoor use, anti-reflection coated lenses for use under artificial lights and driving at night, and blue light blocking filters when working on LED illuminated screens.
As you can see, refractive error is the main cause of these five signs, however other common conditions affecting vision, including binocular vision disorders, presbyopia and glare, can be precipitating factors. All of these conditions can be corrected or treated with glasses.
By Dr. Ed Kosmac – Optometrist and Director at Kosmac & Clemens Optometrists