Astigmatism is a fairly common structural disorder of the eye. It occurs when the outer lens, the cornea, changes from its natural spherical shape to be more elliptical; like the shape of a rugby ball. This causes light entering the eye to be refracted unevenly and split into two points of focus – instead of a single clear image on the retina at the back of the eye.
This article on laser eye surgery for astigmatism is written by Jackie Griffiths, a freelance journalist who writes health, medical, biological, and pharmaceutical articles for national and international journals, newsletters and web sites.
What is astigmatism?
If you suffer from astigmatism you will have difficulty seeing objects both close-up and far away, and if left unresolved it can cause squinting and headaches. Wearing spectacles or contact lenses can mask the problem, enabling both eyes to focus correctly. However, they don’t actually cure the astigmatism, and in some cases can actually make it worse.
Special contact lenses worn overnight can temporarily fix astigmatism, or for a permanent result there are various surgical options, including laser eye surgery. Although slightly more complex than treating myopia (short-sightedness) or hyperopia (long-sightedness), laser eye surgery is still highly effective for cases of astigmatism.
LASIK (Laser Assisted In Situ Keratomileusis)
LASIK is the most popular form of laser eye surgery because it can correct a wide range of vision disorders, and has the shortest and most comfortable period of recovery. The procedure takes less than 30 minutes, and you can return home almost immediately after surgery (there is no need for a hospital stay).
The first UK LASIK procedure was performed in 1995, and ever since then there have been dramatic improvements in laser speeds, incision techniques, and computer-guided technology. The LASIK process involves the application of anaesthetic drops into your eye, fitting a lid speculum to gently hold the eyelids open, and attaching a tiny ring to the eyeball to restrict movement. You will not be able to feel most of this because of the numbing anaesthetic drops.
With a precision blade, known as a microkeratome, the surgeon makes a very small incision (between 3-9mm) in the top layers of the cornea (known as the epithelium). This area is then folded and temporarily removed enabling access to the middle corneal layers (the stroma).
The surgeon then activates the computer-guided ultraviolet laser which sends fleeting pulses of light into your eye. This is how it reshapes the cornea with ultimate precision; flattening it for cases of myopia or steepening it for hyperopia. In the case of astigmatism, the laser smoothes the cornea into a more regular shape. It is likely that you will have more than one of these conditions – and with laser eye surgery they can all be treated together.
Once the laser has done its work (which usually takes around 30 seconds), the cornea flap is replaced and covered with a protective contact lens to reduce irritation. The recovery period lasts for 1-2 days while the epithelium heals and you will need to apply antibiotic eye drops to resist infection. Over the next four weeks, the eyes will heal fully and your vision will stabilise.
If you are suffering from astigmatism, there are other treatments to consider that do not involve lasers.
CK (Conductive Keratoplasty) is ideal for people who are over 40 and have hyperopia, astigmatism, or presbyopia (long-sightedness due to ageing). The latter is untreatable with LASIK surgery because presbyopia affects the inner lens of the eye and not the cornea. CK uses the heat from radiofrequency waves to shrink collagen fibres, which steepens the cornea.
AK (Astigmatic Keratoplasty) reduces the extent of astigmatism by restoring the cornea back to its original spherical shape. During AK, tiny incisions are made in the cornea, which naturally alter its curvature. Best suited to people who have mild astigmatism, it’s also sometimes needed after traditional LASIK or PRK laser eye surgery. However, its use has declined a great deal since LASIK proved successful at correcting astigmatisms.
Orthokeratoplasty uses special rigid gas permeable (RGP) contact lenses to reshape the cornea while you sleep. After taking a ‘digital map’ of your eye, a tailored set of contact lenses will be made for you to wear for a minimum period of time each day. The exact schedule will depend on the severity of your case. When you remove the lenses, your vision will be temporarily corrected. Ortho-K is ideal for people with mild astigmatism or myopia, and youngsters whose eyes have not yet finished growing.