It is a common vision problem where the eye cannot accurately focus on light at a focal point causing blurry vision on objects near and far. The severity of the blur is defined by the magnitude of Astigmatism. If left unattended, Astigmatism could get worse with age.
In Astigmatism, the curvature of the eye or lens is irregularly shaped like a rugby ball rather than a football. This causes light rays to fall unevenly on the retina instead of normallyfocusing at a single point on the retina which is at the back of the eye.
When the cornea of the eye is irregularly shaped, it is called Corneal astigmatism. when the lens of the eye is distorted, it is known as Lenticular astigmatism. Corneal astigmatism is more common than the latter.
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Causes of Astigmatism
- When the curvature of the cornea or lens are unequally curved.
- When the curvature of the lens change causing Astigmatism to increase or decrease. This could eventually cause cataracts.
- After an eye injury or eye surgery.
- Keratoconus a rare condition when the cornea increasingly becomes thinner or cone-shaped. This results in enormous vision loss which cannot be corrected by eye-glasses.
- People can also be born with some degree of astigmatism. They may also have other refractive errors like nearsightedness (myopia) or farsightedness (hyperopia).
Types of Astigmatism
The type of astigmatism depends on the curve of the meridian of the eye that is perpendicular to the other meridian. Before we understand the types, let’s look into the technicalities of what lies behind.
Meridian of the eye – imaginary lines are drawn around the eyeballs with the centre of the pupil as the pole. These lines intersect at the poles. These lines are known as the meridians. The steepest and flattest of the meridians are called the Principal meridians.
There are many types of Astigmatism but the most common three are:
- Myopic astigmatism: When one or both the principal meridians of the eye are nearsighted. If they are both nearsighted, they will both have a varying degree.
- Hyperopic astigmatism: One or both principals become far sighted. If both meridians are farsighted, they are hyperopic in different degree.
- Mixed astigmatism: This occurs when one principal meridian is nearsighted while the other meridian is far sighted.
Regular and Irregular Astigmatism
Due to refractive errors, Astigmatism can be regular or irregular depending on how perpendicular principle meridians of the cornea are. Regular astigmatism has meridians that are 90 degrees apart from each other with uniform curvature at every point across the entrance of the pupil.
Irregular astigmatism has meridians that are not perpendicular to each other. The principal meridians are always at a variance other than 90 degrees from each other. The curvature is not uniform and changes at every point across the entrance of the pupil.
Symptoms of Astigmatism
- Blurred or distorted vision
- Squinting to see near and far objects
- Difficulty seeing at night
- Tired eyes
Tests could be one of the following:
- Vision test: You will be asked to read letters on a chart, 20 feet away from you. The test includes near vision, distance vision and, Amsler grid test.
- Refractiontest: you will be asked to look into a refractor device called Phoropter. As you look through it, the doctor will place many lenses and you will be asked which lens helps you see the best. Your doctor may also use a hand-held device called Retinoscope to measure the eyes.
- Keratometry: A keratometre is used to measure the curvature of your cornea. By focusing light into your cornea, it measures the deepest and flattest area of the curve. This helps in prescribing the correct measurement for wearing contact lenses.
- Corneal topography: It is an advanced technology to determine whether a surgery for astigmatism or cataract is needed. As you look into something specific in the device, thousands of tiny measurements are collected from your cornea. From this data, a computer builds a color map which will determine your case. This may also be used to fit contact lenses or diagnose keratoconus, a disease-causing large amounts of astigmatism.
Treatment of Astigmatism
To treat Astigmatism, your doctor may prescribe optical therapy using eyeglasses or contact lenses called a toric lens. But for severe astigmatism, refractive surgery may be the best option possible.
Different surgeries available are:
- Laser-assisted in-situ keratomileusis (LASIK): A surgery to reshape the cornea by making a thin, hinged flap on the cornea so that it can focus light rays better.
- Laser-assisted subepithelial keratectomy (LASEK): Instead of making a flap, the surgeon loosens the thin, protective cover of the cornea called the epithelium with a special alcohol.
- Photorefractive keratectomy (PRK): The surgeon removes the epithelium which then grows back naturally to conform to the shape of the cornea.
- Epi-LASIK: similar to LASEK, a specialized mechanical blunt blade is used, instead of an alcohol to separate the thin sheet of the epithelium.
- Astigmatic keratotomy: Making tiny cuts into the steepest curves of the cornea to allow light rays to focus precisely on the retina.
- Full evaluation of your eye including tests like corneal thickness, vision, mapping and prescription testing, eye pressure, and pupil dilation.
- Ensure that your doctor is fully informed about your medical history and medications being taken.
- Your doctor will give you the best option for surgery that is suitable for you.
- Ensure that you don’t wear makeup one or two days before surgery to prevent any infection.
- Make sure your face is clean without lotions, moisturizers, or perfume to avoid contact with the eye and cause eye infections.
- If you wear soft contact lenses, switch to wearing glasses one week before surgery. In case of hard contact lenses, start wearing glasses three to four weeks prior to surgery.
- Avoid alcohol one or two days before surgery.
- Wear something comfortable that is not wool and lint-free on the day of surgery.
- Anaesthetic eye drops will be administered on the eyes to numb them.
- The laser surgery will be around 30 minutes and you will be in the surgery room for about 2 hours.
- You will lie flat on the operating bed and the laser will be placed directly in line with your eye that is to be operated.
- A prop called speculum will be fitted to hold your eye open.
- For LASIK, the surgeon creates a hinged flap on top of your cornea to expose the tissue bed. An excimer laser is used to reshape your cornea. The flap is replaced for healing.
- If it is SMILE surgery, the surgeon makes a 3mm keyhole entry point with a laser. Within the cornea, a precise lens-shaped disc of a tissue is made which is then removed through the keyhole incision.
- With ASLA(PRK or LASEK), a topical solution is administered in the eye to remove the top layer of corneal cells. A reshaping of the cornea tissue is done with the help of an excimer laser. A bandage contact lens is placed to aid the healing process.
- If both eyes need surgery, it will be conducted on the same day.
- Your vision will be blurry for some time although you may be able to see distant objects.
- You will be asked to rest awhile before you are sent off home.
- You will be given medicated eye-drops to use and a follow up appointment will be scheduled one or two days after.
- Your eyes may appear red and water considerably, but this is normal.
- Avoid rubbing your eye at any cost.
- You will be given eye drops like – antibiotic, steroid, and lubricating eye drops.
- Depending on your surgery, you will be able to see the next morning or after 2 – 3 weeks.
- If you had an ASLA, you may experience pain, but oral medication will be provided.
- Your bandaged eye lens will be taken off 3-4 days after surgery.
- You must refrain from wearing eye-make up for some weeks, avoid swimming and exercise and contact sports for 2 – 4 weeks.
Every surgery is not without complications. Most of the problems could be solved with medical treatment or additional enhancement surgery. Possible outcomes could be:
- Temporary discomfort and visual disturbances like experiencing halos, glares in low light especially at night.Hazy vision and reduction in sharpness of the vision
- Dryness of the eyes
- Flap complications
- Eye infection
- Residual refractive error
- Epithelial growth
Factors Affecting Cost of the Treatment
The cost of Refractive surgery depends on the type of treatment. It could on average, start from $300 and above. Besides this, there may be other factors that may be considered:
- The hospital the patient chooses
- Location of the selected hospital
- Tests and diagnostic procedures
- Surgeon’s fee
- Cost of surgery
- Cost of follow-up
- Cost of medications