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Refractive Errors
A refractive error means the eye does not focus light exactly on the retina, so vision is blurred. The four types — myopia, hyperopia, astigmatism and presbyopia — are the most common vision problems and are corrected with glasses, contact lenses, or at cataract surgery with the choice of lens implant. Dr. Michael E. Rom measures and corrects them at Insight Eye Center in Mentor.
What are refractive errors?
To see clearly, the front of the eye — the cornea and the lens — must bend (refract) light so it focuses exactly on the retina at the back of the eye. A refractive error means the focus lands in front of or behind the retina, or at two points instead of one, because of the length of the eye or the shape of the cornea or lens. The result is blurred vision.
Refractive errors are the most common vision problems and are not diseases: the eye is healthy, it simply focuses light imperfectly. They are measured at an eye exam (a refraction) and corrected with glasses, contact lenses, or — at the time of cataract surgery — the choice of lens implant.
Insight Eye Center does not perform LASIK. Dr. Rom corrects refractive errors with glasses and contact lens prescriptions and, for cataract patients, with toric and extended-range lens implants.
What are the types of refractive error?
There are four: myopia (nearsightedness), in which distant objects are blurred; hyperopia (farsightedness), in which near objects are blurred; astigmatism, an uneven curve of the cornea that blurs vision at every distance; and presbyopia, the age-related loss of near focus that makes reading glasses necessary after about 40. Many people have more than one.
Myopia (nearsightedness)
The eye is longer than its optical length, so light focuses in front of the retina. Near objects are clear; distant ones — road signs, the television — are blurred. Usually appears in childhood and can progress into the twenties. Corrected with minus-power lenses.
Hyperopia (farsightedness)
The eye is too short or the cornea too flat, so light focuses behind the retina. Distant objects are clearer than near ones, and the eye works harder to focus, which can cause eyestrain and headaches. Corrected with plus-power lenses.
Astigmatism
The cornea is curved more steeply in one direction than the other, so light focuses at two points instead of one and vision is blurred or distorted at all distances. Corrected with cylindrical lenses, toric contact lenses, or a toric lens implant at cataract surgery.
Presbyopia
A natural part of aging: the lens inside the eye stiffens and can no longer change shape to focus up close. It affects everyone, usually starting in the early forties, and is corrected with reading glasses, bifocals or progressive lenses, or with extended-range lens implants at cataract surgery.
How are refractive errors diagnosed?
A refraction — the "which is clearer, one or two?" part of an eye exam — measures the exact lens power that brings your vision into focus, and automated instruments measure the curve of the cornea. Symptoms that prompt the exam include blurred vision at distance or near, squinting, eyestrain, headaches, difficulty with night driving, and, after 40, holding reading material farther away.
Because a refraction is also part of a medical eye exam, Dr. Rom checks the health of the eye at the same time. A prescription that changes quickly, especially in an older adult, can be an early sign of a cataract, and sudden blur can have medical causes that deserve attention.
- blurred vision at distance, near, or both
- squinting to see clearly
- eyestrain or headaches after reading or screens
- difficulty seeing at night
- needing to hold print farther away
- a glasses prescription that keeps changing
How are refractive errors corrected?
Glasses are the simplest and safest correction; contact lenses give a wider field of view and suit active lifestyles. For patients having cataract surgery there is a third option: the lens implant itself can correct nearsightedness or farsightedness, a toric implant corrects astigmatism, and extended-range implants reduce presbyopia — so many patients depend far less on glasses after surgery than before.
Laser vision correction such as LASIK reshapes the cornea to correct a prescription; Insight Eye Center does not offer it, and Dr. Rom can advise whether it is worth discussing elsewhere. For most adults over 60 with a developing cataract, the lens implant is the better opportunity.
Common questions about refractive errors
Short answers to the questions patients ask most often. For anything specific to your eyes, ask Dr. Rom at your visit or call the office at (440) 286-1188.
What is the difference between nearsighted and farsighted?
Nearsighted (myopic) eyes see near objects clearly and distant ones blurred; farsighted (hyperopic) eyes see distant objects more clearly than near ones. Both are corrected with glasses, contacts, or the lens implant at cataract surgery.
Can astigmatism be corrected?
Yes. Glasses and toric contact lenses correct it day to day, and at cataract surgery a toric lens implant or limbal relaxing incisions correct it inside the eye.
Why do I need reading glasses after 40?
Presbyopia. The lens inside the eye stiffens with age and can no longer change shape to focus up close. It happens to everyone and is not a disease.
Does Insight Eye Center do LASIK?
No. Refractive errors are corrected here with glasses and contact lens prescriptions and, for cataract patients, with the choice of lens implant.
Can cataract surgery get rid of my glasses?
It can greatly reduce your need for them. The lens implant corrects your distance prescription, a toric lens corrects astigmatism, and extended-range lenses add nearer vision. Most patients still use readers for fine print.
Blurry vision? Start with an exam.
Request an eye exam with Dr. Rom in Mentor. A refraction measures your exact prescription, and the medical exam checks that nothing else is behind the blur.
