ASTIGMATISM
Astigmatism is a general and treatable condition in which the surface of the cornea is abnormally curved, leading to blurred vision.
- Astigmatism is neither an eye disease nor a health problem. Rather, it is a refractive error that is associated with a defect on how the eyes focus
- Other refractive errors include near sightedness or farsightedness and presbyopia.
- Astigmatism may occur in combination with other refractive errors.
- There are two types of astigmatism namely: corneal astigmatism and lenticular astigmatism
- Corneal astigmatism happens when your cornea is abnormally curved
- Lenticular astigmatism happens when the lens located behind the cornea inside the eyes is irregularly shaped.
- Astigmatism can occur in children and adults.
- It may be present at birth or develop later in life.
The American Optometrist Association (AOA) recommends eyes test for children:
- At 6 months
- At 3 years
- Before first grade
- Every 2 years after that
Adults should have their eye tested every two years and more often if they have chronic conditions such as diabetes.
CAUSES
There are two structures in the eyes (cornea and lens) with curved surfaces that transmit and focuses light on the retina, which makes images. In a normal eye, these two elements have a round curvature like the surface of a ball. If either the cornea or lens is irregularly shaped (like an egg), light rays won’t bend properly causing blurred vision. This condition may be caused by:
- An eye injury
- Disease
- A certain type of eye surgery
- A family history of astigmatism
- Scarring or thinning of the cornea
SYMPTOMS
- Distorted or blurred vision
- Eyestrain or discomfort
- Headaches
- Squinting
- Eye irritation
- Difficulty with night vision
DIAGNOSIS AND SYMPTOMS
DIAGNOSIS
A thorough eye test is carried out during diagnoses by an optometrist or ophthalmologist. Your doctor uses these tests to check different aspects of your eyes and vision. The series of test carried out include:
- Refraction test where an optical refractor is used to determine how your eyes bend light.
- Visual acuity test, you will be asked to read letters from a chart at a certain distance to check how well you can see.
- Keratometry, where the curvature of your cornea is measured through a keratometer.
- Corneal topography which gives more information about the shape and curve of the cornea
TREATMENT
The aim of treatment is to improve sight and eye comfort. The most common types of treatment are corrective lenses and surgery.
Corrective lenses are available in form of glasses or contact lenses. Corrective lenses bend the incoming light into your eye properly in such a way that compensates for the uneven curvature of your cornea and lens.
Eyeglasses may be a better option for children under 12.
To reduce the risk of an eye infection in people using contact lenses, understanding good contact lens hygiene is essential.
Refractive surgery enhances vision and reduces the need for contact lenses or eyeglasses. The curved shape of the cornea is reshaped with the help of a laser beam. This corrects the refractive error. Before surgery, an evaluation is carried out to determine if you are a candidate for such surgery. The types of refractive surgery for astigmatism include
- Photorefractive keratectomy
- Laser-assisted subepithelial keratectomy (LASEK)
- Laser-assisted in-situ keratomileusis (LASIK).