Can Someone Have Both Myopia and Astigmatism?

Yes, it is quite common for people to have both myopia and astigmatism. Approximately 80% of eyeglass wearers have some form of astigmatism, whether it occurs alone or in combination with myopia, hyperopia, or presbyopia.

Understanding Astigmatism

By Ben Wilkinson FRCSC

A normal magnifying lens is perfectly round, meaning its curve has the same steepness throughout. When the curve becomes steeper in one direction and less steep in another, it is referred to as astigmatism. This can be described in two ways: either the weaker long axis strength is quoted and the difference added, with the direction of the ovalness given (e.g., 5.00 2.00 x 180), or the same lens might be described as 7.00 -2.00 x 90.

The ideal eye, from an optical perspective, would have a prescription of 0.00. Factors that can distort the eye's shape, such as genetic predisposition, developmental anomalies, or external pressures, can cause astigmatism. Genetic causes are the most common, as the eye might naturally grow more oval. Lesser-known causes include a lump in the eyelid pushing on the eye, or a tumor pushing on the eyeball. The amount of astigmatism in an individual's eye typically remains relatively constant. A significant change, such as 1.00D or more, should be carefully examined for a cause, especially if it only affects one eye.

Understanding Myopia

By Ben Wilkinson FRCSC 2020 Dec.

Myopia, or nearsightedness, is a condition where the eyeball grows too long optically. It's largely a genetic hereditary condition that develops with growth, stabilizing around age 17-21. Myopia has become increasingly common in recent years, with various explanations. One of the most compelling is that the development of myopia is linked to growth. As people are growing taller and faster, this is more evident in countries like Japan. Prior to World War I, Japanese people were characterized as small and rarely wearing glasses. Following significant dietary changes, they grew taller and became more nearsighted, with current studies showing nearly all Japanese being myopic. Another explanation, though less likely, is that they have always been myopic, but glasses were not available. This is improbable given that good distance vision was not a valued skill in warrior times.

At present, there is no known method to control the growth of the eyes, and thus myopia is considered untreatable. Surgical correction through LASIK is a viable option once growth has ceased. Early signs of myopia should be monitored closely to distinguish between pseudomyopia (eyeball cramping) and true myopia. High myopia, with prescriptions -6.00D or stronger, carries a risk of certain complications, which increase with prescription strength. These complications are thought to be related to the stress between the size of the sclera (the tough outer layer of the eye) and the retina (the light-sensitive 'film' in the eye), which originate from different tissues in the embryo.

Treatment Options for Myopia and Astigmatism

Refraction errors caused by myopia and astigmatism can be corrected using glasses, contact lenses, or ortho-keratology. Ortho-keratology involves wearing contact lenses at night to reshape the cornea, eliminating the need for corrective lenses during the day. Refractive surgery, such as LASIK, is another option to alter the curvature of the cornea. Once glasses or contacts are needed, the debate arises about whether to wear them all the time. Wearing glasses changes the optics to normal, allowing the eyes to relax in the far distance and switch focus when objects come close. This mirrors natural vision and has no effect on myopia progression.

My recommendation is to wear glasses consistently if needed frequently. This minimizes the risk of misplacing the glasses and avoids scratching them, making life more convenient in general, except when swimming, bathing, or in bed.