The human eye can only see distinctly and comfortably when the image is correctly focused on the retina. When it does not focus properly, the vision becomes blurred. It is called a vision defect.
The most common defects of the eyes are Myopia or short-sightedness, Hypermetropia or far-sightedness, and presbyopia. These can be corrected by wearing spectacles with bifocal lenses.
Presbyopia
The eye lens’s capacity to change shape and focus on near objects is diminished with age. It happens gradually and affects everyone over the age of 40. If you find it harder to read small print or notice that you must hold your books, magazines, or digital devices farther away from your eyes to see clearly, this is a sign of presbyopia.
Light enters the eye and passes through the cornea and pupil, which the iris controls. The lens then bends the light rays to focus on the retina at the back of the eye. A young vision can shift from a distance to a near object within seconds without difficulty, but the flexibility of the eye’s lens decreases with age.
If you have blurred vision, seeing a trusted optometrist serving the Ottawa area who can evaluate the cause and recommend a corrective solution is essential. You may need eyeglasses or bifocal lenses, contact lenses, or surgery to manage this common problem.
Myopia
Myopia is nearsightedness, which makes distant objects blurry and close ones clear. It arises from either an excessively long eyeball or an excessively steeply curved cornea, the transparent front portion of the eye covering the lens. Light entering the eye is, therefore, directly in front of the retina, the light-sensitive tissue at the back of the eye.
Experts don’t know what causes myopia, but it does tend to run in families. If one or both parents have myopia, a child is three times more likely to develop it. Spending a lot of time indoors and doing up-close work — such as reading, playing video games, or using computers and smartphones — also increases the risk.
Most cases of myopia are mild and can be corrected with eyeglasses, contact lenses, or refractive surgery. On the other hand, degenerative myopia, a severe form of myopia, can cause glaucoma and retinal detachment in adults.
Hypermetropia
Long-sightedness (hypermetropia) occurs when the eye focuses images behind the retina rather than directly on it. This blurs vision at medium and near distances. It is caused by either a misshapen cornea, weak focusing muscles in the lens, or an eyeball that is too short. Symptoms include blurred near or distant objects, eyestrain, and headaches.
People with hypermetropia can usually see far-away things clearly, but they may struggle when they get closer to an object, such as when reading or using a mobile phone. It can cause squinting and eye rubbing, leading to problems such as blepharitis or a stye (chalazion).
People with hypermetropia need to wear their glasses regularly, even when not wearing their contact lenses, to help with good vision. Teachers, primary care physicians, or optometrists should regularly screen people with hypermetropia for their visual acuity. It typically involves reading symbols from a standard test chart.
Astigmatism
Clear vision is achieved when light rays are focused directly on the retina by the lens, which is the transparent portion of the eye behind the colored iris, and the cornea, which is the eye’s front surface. But astigmatism causes blurry near and far objects if your eyes are irregular.
Your cornea or lens has mismatched curves. You may have regular astigmatism if the curves of your cornea are not all the same or lenticular astigmatism if your lens has mismatched angles.
Your doctor can diagnose astigmatism by doing a comprehensive eye exam. It includes placing lenses of different strengths in front of your eyes and looking at a Snellen chart. Your doctor will also use an autorefractor to measure how your eyes focus light.
The results of these tests help your doctor prescribe the correct lenses for you. If you have astigmatism, your prescription will include a correction for both nearsightedness and farsightedness.
