Astigmatism Correction- Ophthalmology

Astigmatism, a common type of refractive error, occurs when the curvature of the eye’s cornea or lens is unequal. Smooth and equal curvature of the cornea and lens helps to focus light rays onto the retina. Retina, a tissue that is located at the back of the eye, is the light-sensitive tissue. In this condition the eye does not focus light evenly onto the retina.

Astigmatism occurs due to an irregular or uneven curvature of the eye's cornea or lens. When the cornea or lens is not curved evenly, light rays cannot get refracted properly. Astigmatism is a very common condition and is known to get inherited. It can develop after an eye injury, eye disease or surgery.  Signs and symptoms may include discomfort in eye, headaches, blurred vision, difficulty driving during night-time, eyestrain, and squinting.

Which Doctor to Consult?

Astigmatism is corrected by an opthalmologist i.e a doctor who specializes in treating diseases of the eye.

How is astigmatism corrected?

Patients with astigmatism have various options available. It can be corrected by eyeglasses, contact lenses or surgery. Mild to moderate astigmatism can be corrected with eyeglasses or contact lenses. Surgery may be an option in patients whose astigmatism cannot be corrected by eyeglasses or contact lenses.

Eyeglasses:  Eyeglasses, the main choice of patients, are the safest and simplest way for correcting the astigmatism. They correct astigmatism by compensating for uneven curves in lens and cornea. They contain a distinct cylindrical lens which provides additional power to the lens to correct the astigmatism. Normally, in order to gain clear vision at all distances, a single-vision lens is recommended. Patients (> 40 years) with presbyopia may require a bifocal or progressive addition lens.

Contact Lenses: Many patients prefer contact lenses as they provide clearer vision and a wilder field of view with better comfort. If used appropriately, they are a safe and effective option. Contact lenses cause a more precise refraction as they are the first refractive surface for light rays entering the eyes. Soft lenses called toric contact lenses can correct many types of astigmatism. Contact lenses may not be right for everyone. As contact lenses are worn directly on the eyes, it is very important to clean them regularly.

Orthokeratology: This involves wearing a specifically fitted, rigid contact lenses, for certain length of time period such as overnight, to reshape the cornea. It does not permanently improve vision, but the patient may have better vision all day after wearing these. Rigid gas-permeable contact lenses can maintain their even shape while on the cornea. Thus, they can compensate for the cornea's uneven shape and improve vision. Once the patient stops wearing the lenses, their vision would return to its original condition.

Laser and other refractive surgical procedures: LASIK (laser in situ keratomileusis) or PRK (photorefractive keratectomy) can also be used to reshape the cornea to correct astigmatism. These surgeries change the shape of the cornea permanently. LASIK removes tissue from the inner layer of cornea while PRK removes tissue from both the inner as well as superficial layers of cornea. These surgeries basically allow the light rays to focus precisely on the retina and thus restore the focusing power of the eye and improves vision.

References:

• https://nei.nih.gov/health/errors/astigmatism
• https://www.aao.org/eye-health/diseases/what-is-astigmatism
• https://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/astigmatism

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