Astigmatism is one of the four most common refractive error (errors resulting from inability of the eye to clearly focus the images from the outside world) enlisted by WHO. It is a vision disorder which occurs due to irregular curve error in the cornea. Due to change in this curvature, the refracted light to the retina no longer converges at the focal point and form two foci instead, causing blurred vision.
10 Fast Facts About Astigmatism
- It is mostly accompanied with other refractive disorders i.e. myopia, hyperopia or both.
- There are two types of astigmatism depending on where the defect or distortion has taken place i.e. corneal (defect in cornea) and lenticular (defect in lens).
- Astigmatism is also categorised based on the direction of curvature i.e. regular (curvature is evenly shaped) and irregular astigmatism (curvature is uneven).
- The most common symptoms of astigmatism include strain in eye, headache, squinting or difficulty in night vision.
- The major causes of astigmatism are genetics, eye disease, injury or surgery of the eye. Very rarely astigmatism can also occur due to keratoconus, a condition which makes our cornea thinner and cone shaped.
- Globally 88.4 million people suffer from vision impairment or blindness due to unaddressed refractive errors. A 2017 study showed that astigmatism was more common than hyperopia and myopia in both children and adults and the highest prevalence of astigmatism was observed in South-East Asian adults.
- Astigmatism cannot be prevented but it can be managed by wearing corrective glasses, lenses or laser eye surgery.
- Astigmatism takes time to show symptoms and the diagnosis require tools such as phoropter (find the perfect lens), keratometer (measures the bend in centre of cornea), autorefractor (measures the change in light as it bounces back from your eye) and corneal topographer (detailed information on the cornea’s shape).
- Many infants are born with astigmatism, but it becomes normal till their first birthday.
- Diabetics are at higher risk of developing lenticular astigmatism as high blood glucose levels in blood alters shape of lens. Patients getting treatment for diabetes over a period of time show improvement in lens condition.
Surgical Management of Astigmatism
Laser eye surgery is an expensive, painless method and it corrects your vision permanently in many cases. There are three major type of laser surgeries LASIK®, PRK® and LASEK®. These surgeries take around 10 minutes for one eye and use laser to remove a thin layer of cornea and reshape it.
- LASIK® is an acronym for Laser-Assisted In Situ Keratomileusis wherein an excimer laser is used to cut a flap in the cornea. A very thin layer of flap is removed and it is put back on. The flap then provides natural healing. Vision is recovered after 24 hours.
- In PRK® (Photo-Refractive Keratectomy) the outer layer of cornea is completely removed using a surgical instrument and then cornea is reshaped with a laser and a new layer of epithelium grows back in 5 days.
- LASEK® (Laser Sub-Epithelial Keratomileusis) involves taking a thinner layer than in LASIK and similar treatment is followed after which the flap is repositioned.
These surgeries are accompanied with some side effects such as blurred vision, infection in the eyes or dry eyes.
Laser surgery is not suitable for patients whose vision is still changing such as individuals under 21 years of age or older people. It is not advisable for diabetics, pregnant or breastfeeding mothers, people with immune conditions such as rheumatoid arthritis, HIV, lupus. People suffering from other eye ailments such as glaucoma or cataracts need to manage these conditions before going for laser surgery.
Astigmatism is a condition which can be managed easily in majority of cases but requires surgical intervention in some cases. If left untreated, these refractive errors of the eye can even result in blindness.