We’ve all had that one friend who seems to have gotten rid of their spectacles overnight. This has worked out great for their appearance, confidence and in some cases, opened up new professional avenues for them, be it a career in the armed forces, sports, travel or even as an actor/model. All this, even as their vision improves without those specs. Yeah, we all realise this is due to an advanced eye operation-but have you ever wondered more about the same?
Besides, what if I told you that there is more than one type of eye surgery involved to surgically remodel the cornea, or for purposes of lens implantation or lens replacement? Yes, the most common method involves lasers to reshape the curvature of the cornea, but more on that later, dear reader.
Right now, let’s first understand the basics.
Refractive errors: a quick introduction
By all means open up your school physics textbook to read up on the definition of refraction. It is likely to tell you that Refraction is a physical phenomenon related to waves (light waves / radio waves) that occur at any surface due to change in medium. It is most commonly observed in case of light, when it passes through one medium to another. Light rays are known to change speed and consequently their path, which process is known as Refraction. The change in direction or path of light depends upon the nature / density of the medium which is known as refractive Index of that material.
And this is exactly how we see. Refraction occurs when light rays pass through our cornea, then the aqueous and crystalline lens and the vitreous before finally converging onto the Retina.
But sometimes, there is a Refractive error- which essentially results in a problem with focussing of the light rays accurately onto the Retina. This is due to the shape of the eye. This can result in various conditions including Myopia (Near-Sightedness), Hyperopia (Far-Sightedness), Astigmatism (Irregular vision). Similarly, Presbyopia occurs as we age; you see, the lens becomes harder or less elastic, thus making it more difficult for an eye to focus on closer objects.
Hence, the need to correct it.
Refractive Surgery: Rationale and reasoning.
The question arises: why go through the tedium and expense of an operation when one can easily wear glasses and get on with their lives? For the fashion-conscious amongst us, contact lenses are an option. Plus, they come in exciting colours too!
Well, anyone who has used glasses or contact lenses for a definitive period of time will tell you how cumbersome and inconvenient they are. Glasses can break. They can also slow down an active sports/travel-loving lifestyle. Not to forget their limited aesthetic appeal-they can adversely impact a person’s self-image. As for contact lenses, they need a lot more care than glasses and have risks associated with them. For starters, you have to clean and store them the right way and stay away from conditions of extreme heat. Serious eye infections are in store for you if you don’t clean them well or fail to wash your hands before handling them. Corneal ulcers, eye infections and even blindness are conditions associated with incorrect use of contact lenses. Considering we all lead such high-pressured lives already, who needs this added worry, dear readers? Corrective surgery can do away with all the risks and cons and dramatically change your life for the better. Plus, considering all the advances in the last three decades, you have the highest chances of achieving perfect vision post the surgery.
Never fear, Refractive Surgery is here!
There are many types of Refractive Surgeries available, most of them are related to reshaping the corneas, so that light passing through it can be focused perfectly on the Retina. The other main type of surgery focuses on surgically replacing the lens or adding another lens inside the eye.
Here’s a quick look at the various types of Refractive Surgeries.
LASIK (laser in-situ keratomileusis): This is the most widely-favoured surgery nowadays that reshapes the underlying corneal tissue to focus light into the eye and reach the Retina. It is the perfect choice for those with nearsightedness, farsightedness, or astigmatism. LASIK stands out for the methodology it employs. Eye surgeons create a flap of the outside layer of the cornea to access the underlying tissue. This procedure requires precision, and advancements in computer imaging technology allow LASIK specialists to create detailed corneal images and guide the treatment.
PRK (photorefractive keratectomy): PRK is a procedure that uses a laser to reshape the cornea. Unlike LASIK, PRK only reshapes the surface of the cornea. It’s ideal for mild to moderate nearsightedness, farsightedness, or astigmatism. PRK can also work with computer imaging technology. Initially it was believed that PRK was ideal for people in contact sports or in the army or police who are likely to get struck in the eye. But even with standard LASIK, the risk of eyeball rupture is still very low, and it is also a better option for myopia.
LASEK (laser epithelial keratomileusis) This procedure is a slight variation of PRK. The doctor will create a flap where epithelial cells are loosened by applying an alcohol solution. Then, a laser reshapes the cornea, and the flap is set and secured with a soft contact lens so that it can heal around the correction. LASEK treats nearsightedness, farsightedness, and astigmatism.
ALK (Automated Lamellar Keratoplasty) ALK can help people with severe nearsightedness and few levels of farsightedness, although LASIK has almost fully replaced ALK as a method of correction. For this procedure, an eye specialist creates a flap in the cornea to access the underlying tissue. No laser is used, and instead, the doctor makes an incision in the sub-layer of the cornea to reshape and correct vision.
RLE (Refractive Lens Exchange) RLE is a procedure for correcting refractive errors, especially between the age of 45-50. The doctor makes a small incision to remove the natural lens of the eye on the edge of the cornea. The lens is replaced with a silicone or plastic lens. This procedure is also known as CLE (clear lens extraction) or RLR (refractive lens replacement) and can be used to correct severe farsightedness or nearsightedness. It is also used to correct thin corneas, dry eyes, and other minor eye problems. Additional procedures may be needed to correct astigmatism.
EpiLasik This is very similar to PRK. The ophthalmic surgeon separates a thin layer of the cornea and then reshapes it. The layer may either be removed or replaced. The doctor finishes the procedure by applying a soft contact lens to protect the area until it can fully heal.
PRELEX (presbyopic lens exchange) If the eye’s lens loses its flexibility, the condition is referred to as presbyopia. Patients with presbyopia have difficulty focusing on close objects. PRELEX is a procedure where the eye doctor implants a multifocal lens to improve flexibility and restore focus.
Phakic Intraocular Lens Implants: Some patients who are too nearsighted for both PRK and LASIK, need Phakic Intraocular Lens Implants. For this procedure, the doctor inserts an implant through a very small incision at the edge of the cornea that attaches to the iris behind the pupil. The eye’s natural lens is left in placeIt may also be an alternative to LASIK for older adults.
Small-incision lenticule extraction (SMILE). This reshapes the cornea by using a laser to make a lens-shaped bit of tissue (lenticule) below the cornea surface. Once the lenticule has been used to reshape the cornea, it is removed through a very small incision.
Bioptics. Bioptics combines one or more techniques, such as intraocular lenses and LASIK, to treat nearsightedness or farsightedness.
AK (Astigmatic Keratonomy): AK is a surgery that corrects an astigmatism without the use of a laser. People with astigmatism have corneas that are shaped like a football, and this surgery corrects that by making one or two incisions at the steepest part of the cornea. After the incisions are made, the cornea relaxes and takes a more rounded shape. AK can be performed alone or with other laser eye surgeries.
Clinical evaluation of patients can determine the type of Refractive Surgery suitable for that patient. Advanced options like Contura are also available nowadays. In our next blog we are going to take a look at the most popular Refractive Surgery – LASIK with a success rate of 92 to 98 per cent.
(Assorted reports, medical websites and KK’s archives.)
