Common Refractive Errors

Astigmatism vs Myopia,Short Sighted, Long Sighted…

What does it all mean?

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astigmatism vs myopia


Myopia is the clinical term for nearsightedness. Nearsighted eyes can see near objects clearly, but have a difficult time seeing objects far away. Myopia affects approximately 1/3 of Americans.

Myopia typically occurs when the eye is too long. This causes a distant image to be focused in front of the retina, therefore causing distance blur. Blurred vision can be corrected with glasses, contact lenses, or refractive surgery (such as LASIK).

As children grow, the eye tends to get longer over time. This means myopic children must often get stronger glasses every year as the eye grows.

What causes myopia?

Myopia is thought to be caused by a combination of genetics, lifestyle and environmental factors. A child with one myopic parent is 2 times more likely to develop myopia, but those with 2 myopic parents are 5 times more likely. This Nearsightedness Assessment tool by CooperVision can show you what your child sees with different degrees of myopia.

The prevalence of myopia is on the rise, and this is thought to be because children are spending less time outdoors. Research shows that spending 2 hours per day outdoors may be able to delay or prevent myopia development in at-risk children.

Black Diamond Eye Care has a number of myopia control protocols available to assist in reducing myopic progression for your child. Click here to learn more about Myopia Control.


Hyperopia, or farsightedness, is a vision condition in which distant objects are usually seen more clearly than close ones. Farsightedness is due to the eye not bending light properly, so it focuses behind the back of the eye or the cornea has too little curvature. Hereditary factors often control the growth and development of the eye.

Common signs of hyperopia include difficulty concentrating and maintaining a clear focus on near objects, eye strain, fatigue and/or headaches after close work, aching or burning eyes, and irritability or nervousness after sustained concentration.


Astigmatism is an irregularly shaped cornea or lens that prevents light from focusing properly on the retina, the light-sensitive surface at the back of the eye. The surface of the cornea is shaped more like a football instead of round like a basketball and the eye is unable to focus light rays to a single point. In this case, vision becomes out of focus at any distance. In addition, the curvature of the lens inside the eye can change, resulting in an increase or decrease in astigmatism. This change frequently occurs in adulthood and can precede the development of naturally occurring cataracts.

Astigmatism frequently occurs with other vision conditions like myopia (nearsightedness) and hyperopia (farsightedness). Together these vision conditions are referred to as refractive errors because they affect how the eyes bend or “refract” light.

Astigmatism can be hereditary and is usually present from birth or it might develop following an eye injury or eye surgery. It can decrease or increase over time and could possibly occur due to a relatively rare condition called keratoconus in which the cornea becomes progressively thinner and cone-shaped.


Presbyopia is a vision condition in which the shape of the crystalline lens of your eye changes. These changes make it difficult to focus on close objects.

Presbyopia may seem to occur suddenly, but sight reduction occurs over several years. Presbyopia usually becomes noticeable in the early to mid-40s, but the reduction of your focus starts as early as childhood.

Some signs of presbyopia include holding reading materials at arm’s length, blurred vision at normal reading distance and eye fatigue along with headaches when doing close work.

Presbyopia is a natural part of the aging process of the eye. It is not a disease, and it cannot be prevented, but it’s effects on your daily life can be minimized with glasses or a variety of types of contact lenses (bifocal, multi-focal or mono-vision).

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