Refractive error means that the shape of your eye does not bend light correctly, resulting in a blurred image. The main types of refractive errors are myopia (nearsightedness), hyperopia (farsightedness), presbyopia (loss of near vision with age), and astigmatism.
Difficulty reading or seeing up close
Crossing of the eyes in children (esotropia)
Overuse of the eyes does not cause or worsen refractive error. The causes of the main types of refractive error are described below:
Myopia (close objects are clear, and distant objects are blurry)
Also known as nearsightedness, myopia is usually inherited and often discovered in childhood. Myopia often progresses throughout the teenage years when the body is growing rapidly. Watch a video explaining myopia.(link is external)
Hyperopia (close objects are more blurry than distant objects)
Also known as farsightedness, hyperopia can also be inherited. Children often have hyperopia, which may lessen in adulthood. In mild hyperopia, distance vision is clear while near vision is blurry. In more advanced hyperopia, vision can be blurred at all distances.
Presbyopia (aging of the lens in the eye)
After age 40, the lens of the eye becomes more rigid and does not flex as easily. As a result, the eye loses its focusing ability and it becomes more difficult to read at close range. This normal aging process of the lens can also be combined with myopia, hyperopia or astigmatism.
Watch a video explaining presbyopia(link is external).
Astigmatism Astigmatism usually occurs when the front surface of the eye, the cornea, has an asymmetric curvature. Normally the cornea is smooth and equally curved in all directions, and light entering the cornea is focused equally on all planes, or in all directions.
In astigmatism, the front surface of the cornea is curved more in one direction than in another. This abnormality may result in vision that is much like looking into a distorted, wavy mirror. Usually, astigmatism causes blurred vision at all distances. Watch a video explaining astigmatism(link is external).
People with high degrees of myopia have a higher risk of retinal detachment which may require surgical repair.
Tests and Diagnosis
A refractive error can be diagnosed by an eye care professional during a routine eye examination. Testing usually consists of asking the patient to read a vision chart while testing an assortment of lenses to maximize a patient’s vision. Special imaging or other testing is rarely necessary.
Treatment and Drugs
Refractive disorders are commonly treated using corrective lenses, such as eyeglasses or contact lenses. Refractive surgery (such as LASIK) can also be used to correct some refractive disorders. Presbyopia, in the absence of any other refractive error, can sometimes be treated with over-the-counter reading glasses. There is no way to slow down or reverse presbyopia.
TYPES OF REFACTIVE ERRORS
SYMPTOMS OF MYOPIA
· Blurriness of vision at distance.
· Clear vision at near
HYPEROPIA ( FARSIGHTEDNESS OR HYPERMETROPIA)
SYMPTOMS OF HYPEROPIA
· Blurred vision at near
· Complain of tired eyes
· Blurred vision at distance and near.
It is a type of refractive error resulted from unequal refraction of light in different angles.
· Uneven cornea ( cornea astigmatism)
· Irregularity in the lens ( Lenticular astigmatism)
CAUSES OF CORNEA ASTIGMATISM
· Cornea inflammation/ cornea scar
· Dry eyes
· Pressure of swelling on the lid (eg: chalazion)
CAUSES OF LENTICULAR ASTIGMATISM
· Deconcentration of IOL (intraocular lens)
SYMPTOMS OF ASTIGMATISM
· Blurred of vision at distance and near.
· Confusion of letters and numbers.
· Difficulty in night driving/glaring.
A natural aging process of the eyes in which the crystalline lens loses the elasticity and results in difficulty to focus at near.
Happens at around 40 years and above.
SYMPTOMS OF PRESBYOPIA· Difficulty in reading small prints at work.
· Fatigue from doing close work.
· Eyestrain/headache after doing near work.
· Need brighter lightning when reading/ near work.
Distancing the reading material to focus