Visual Acuity and How Eyesight is Measured

When your optometrist asks you to read the Snellen Chart, that chart with lines of letters of increasingly smaller size, what they are testing is the clarity of your vision–also known as your visual acuity. This can be impacted by several factors including how sensitive your brain’s interpretive faculty is, the functionality of the retina, and how sharp is the retinal focus of the eye.

How your eyesight is measured is important for determining whether you have vision concerns currently or may develop any in the future. Here’s more on what you need to know about the measurement of your eyesight.


You may have to identify optotypes in order to have your visual acuity measured

As in the above mentioned Snellen Chart, the use of black symbols on a white background is effective for determining the clarity of your vision. The symbols are known as optotypes, and they can include the following: letters that have been stylized, Landolt broken rings (rings that have a gap in them–the person being tested must state on what side the gap is located) and other symbols used for those who are illiterate. The symbols will typically be placed on a printed chart, though other formats are also used.


Charts with optotypes must be placed at a specific distance away depending on the type of test

Your optometrist can test your near visual acuity, by placing the chart at a reading distance, as well as your acuity for how far away you can see.


The measurement of your eyesight is a psychophysical procedure

The results of a test on your visual acuity is ultimately determined by your perception of the physical characteristics of the symbols and the resulting responses that you make.

It is essential that various factors in the room are controlled to ensure the most accurate results. This means that the chart and room must have the right lighting, the person being tested must be given an appropriate amount of time for responding, and an allowance should be made for error.

Please contact us to book an eye exam with our Dr. Alex G. Wilson & Associates today.

5 Tips on Computer Eye Strain Relief

At least half of people who use their computers on a regular basis at work end up experiencing eye strain, studies have shown. This can cause everything from red eyes and eye twitches to decreased productivity, a feeling of physical fatigue, and an increased number of on-the-job errors. Follow these 5 tips to get the computer eye strain relief you need.

#1: Adjust the lighting in the room

Both exterior and interior lighting can play a part in causing eye strain. Excessive light from outdoors may occur in your office if windows are not covered by blinds, drapes, or curtains. If possible, you should try to position your desk so nearby windows are to the side of you, rather than in front of your computer or behind you.

When it comes to interior lighting, install lower intensity light bulbs or fluorescent tubes in your office or reduce the number or bulbs or tubes that are in use. If there are fluorescent lights directly above where you work, try moving away from that spot or turning off the lights to see if this makes a difference–many people find that this type of lighting causes eye strain. Floor lamps that use halogen or incandescent lighting can be a good alternative.

#2: Get an eye exam

The best way to catch common eye problems before they get the chance to develop is to go in for an eye exam. Before you go in, measure how far away from the screen you usually sit–the optometrist can then test your eyes from this distance.

#3: Reduce the amount of glare on the screen

As glare can impact eye strain, consider installing an anti-glare screen on your desktop and, if you wear glasses, getting lenses that have anti-reflective coating.

#4: Use the 20-20-20 rule

Focusing for too long on your screen can cause fatigue. To prevent this, every 20 minutes spend 20 seconds looking at something at least 20 feet away. This will relax the focusing muscle in your eye.

#5: Get computer glasses

If you currently have a prescription for your eyes and are experiencing eye strain, ask Dr. Alex G. Wilson if a modified prescription for computer use would benefit you. Contact us to learn more.

When your child should first get an eye exam

As many as one out of ten preschool age kids and one out of four school age kids are likely to have a vision problem, but the only way to know for sure is to bring your child in for an eye exam.

Many parents wonder when they should first make an appointment with an Dr. Alex G. Wilson. This is an important matter to consider because some vision problems that can begin to develop in childhood can lead to vision loss, especially if they are not treated. The good news is that we can recommend the ideal ages when you should have your children’s eyes examined, starting from under the age of one up until the school-age years when regularly scheduled eye exams are possible.

The first eye exam should take place at six months of age

Six months may seem young, but detecting and preventing some eye conditions is possible at this age. After this initial exam, your child should next come in when they are three years old, and then once more when they are five or six years old.

If after these initial exams your child does not require any vision correction, an eye exam is only necessary for once every two years moving forward. If glasses or contact lenses are determined to be necessary, an annual exam may be recommended by your optometrist.

Eye exams are an essential part of ensuring your child can learn

In school, you child could become discouraged and unable to learn fully if they have difficulties focusing their eyes, seeing up close or far away, or using their peripheral vision. Hand-eye coordination and eye movement skills are also necessary for your child’s development.

Unfortunately, kids often cannot understand for themselves when they have limitations in these areas, and the concerns can be left unnoticed by adults and even by school vision tests. These are all aspects of your child’s vision that an optometrist will examine, ensuring that your child can get the vision assistance that they need.

Please contact us to book an appointment with our full family eye care in Calgary to get started.

The Most Common Eye Problems

Eye problems can begin to develop at a young age or they may show up later in the aging process. To help you to become aware of their causes and symptoms, here are a few of the most common eye problems.

Diabetic Retinopathy

If you have type 1 or type 2 diabetes, you could be at risk of developing this eye problem, due to the continual high blood pressure and high blood sugar that diabetes causes. Diabetic retinopathy comes in different forms that can damage separate parts of the eye. Most commonly, the tiny vessels in the eye can rupture or become blocked, which can cause intraocular bleeding among other issues.

Refractive Errors

Farsightedness, nearsightedness, and astigmatism fall in this category of eye conditions, which are widely known to be the most common of all conditions concerning the eyes. From a young age, people who will later show the symptoms of one of these problems will likely inherently have the condition present in their eyes to some extent.

The causes of refractive errors include aging lenses, eyeballs that are too long or too short, and the occurrence of a change in the shape of the cornea. Presbyopia is one condition in particular that can occur after the age of 40, due to a hardening of the lenses.


With this condition, the eye becomes less able to rid itself of old fluids because of blockages, which can cause excessive intraocular pressure. This can lead to optic nerve damage. It is more likely to develop in older people and in people with diabetes.


There are a couple of main reasons why cataracts can develop, and most of the time only in older people does the condition become severe enough to affect one’s vision. Cataracts is the result of one’s lenses becoming clouded, likely due to an injury (which may have occurred years before symptoms arise) or the long-term deterioration of proteins in the eyes. Unlike many other conditions, it can be cured through surgery. Dr. Alex G. Wilson and our optometrists can determine the appropriate treatment.

Please contact us to access our eye care services, whether you have the beginnings of one of these conditions or require an annual eye exam.