Nearsightedness is more accurately known as myopia. With nearsightedness, vision is best at close range, hence the name – near objects such as text, print, and mobile phones are clear. The distance vision, however, is blurry making it difficult to watch television or a film, read subtitles, or drive a car, participate in sports and most all other outdoor activities. When someone suffers from nearsightedness, they will require corrective lenses, either glasses or contact lenses in order to see. Such glasses or lenses will allow the distance vision to become clear.
Laser eye surgery can cure nearsightedness permanently once the condition is no longer progressing, and LASIK is the preferred option. Key points for LASIK:
- The treatment of choice for myopia
- The laser takes 5-10 seconds to evaporate away a very thin layer of tissue within the cornea, flattening its overall curvature
- The whole procedure is complete in 15 minutes.
Laser vision surgery (LASIK or PRK) for nearsightedness is the treatment of choice in most cases.
Normal vision without myopia
NORMAL EYE: IMAGE FOCUSED ON RETINA
In a normal eye, light enters through the cornea, passes through the pupil (the natural opening in the iris) and continues through the lens located just behind the iris. If there is no refractive error (a glasses prescription) the cornea and lens focus light rays to converge together to make a sharp image on the retina. This light-sensitive layer converts the light into information that passes along the optic nerve emerging from the back of the eye, taking the vision data to the rear part of the brain which then processes this information for you to see the world around you.
The cause of near-sighted blur
Myopia, the medical term for near-sightedness, is most commonly caused by growth of the eyeball, with the eye becoming longer from front to back. The front focusing part of the eye (the cornea and lens) are then unable to focus the light onto the retina because it is too far back. The image is now incorrectly focused in front of the retina, with the light rays crossing and continuing to form a blurred image.
Progression of myopia – when to have treatment
MYOPIA: EYE ELONGATED WITH FOCUS IN FRONT OF RETINA
Myopia typically begins in the teenage years, and gradually progresses with worsening distance vision over the next 10-15 years. With higher levels of nearsightedness, the condition may begin before the age of 10. Some children do not realize at first that their sight is not as good as it could be. They may be able to read books and do close work without difficulty. However, seeing distant objects such as the board at school may become hard. They may think this is normal and not tell anyone. Schoolwork may suffer for a period before the condition is identified and treatment provided.
Myopia typically stabilizes in the early 20s and you no longer need regular increases in the strength of their glasses to see. That is correct time to consider laser vision correction. Most patients are ready to have laser eye correction between 25 and 30, although some may be ready earlier, depending on, e.g. when they first needed glasses.
There are three forms of treatment for myopia, although the first, laser eye surgery, is by far the most used:
- Laser eye surgery: LASIK and PRK/LASEK
- Refractive lens exchange (RLE)
- Implantable collamer lens (ICL)
LASIK is the most performed eye surgery in the world, after cataract surgery, and is most likely the procedure you will have if you are near sighted.
How does the laser correct vision?
Like other forms of refractive surgery, LASIK and PRK reshape the cornea to enable light entering the eye to be correctly focused on the retina for clear vision.
To correct myopia, the cornea needs to be flattened and made less powerful as a lens. This is achieved using an excimer laser, a cool-beam ultraviolet device that can evaporate corneal tissue without burning. Each pulse of the laser removes a depth of 0.2 microns (thousandths of a millimeter). Pulses are scattered across the cornea in a pre-determined pattern to remove enough tissue to correct the specific prescription being treated. Using the extremely fast WaveLight laser, most prescriptions can be fully treated in only 4-10 seconds.
The LASIK procedure for nearsightedness
LASIK, or “laser-assisted in situ keratomileusis,” is the most commonly performed surgery to correct myopia (nearsightedness). It can also be used for hyperopia (farsightedness) and astigmatism.
First, our surgeon uses the Ziemer femtosecond laser to create a very thin, precise circular “flap” in the cornea. An older version of LASIK used a mechanical surgical tool called a microkeratome – this is outdated and should be avoided.
The surgeon then gently folds back the hinged flap to gain access to the underlying cornea (known as the stroma) before using the WaveLight excimer laser to correct your nearsighted prescription.
After the laser has corrected the cornea, the flap is then laid back in place covering the area where the corneal tissue was removed. Then cornea is allowed to heal naturally. The skin surface will seal the edge of the flap within 4 hours.
Surgery requires only topical anesthetic drops, and no bandages or stitches are needed.
LASIK is pain-free and completed within 15 minutes for both eyes. The results are usually obvious instantly – most patients can see fairly well as soon as they sit up. The vision clears overnight and most patients can see very clearly the next day to drive, work, and carry on their regular activities.
The PRK procedure for myopia
PRK (an acronym for photo-refractive keratectomy) is a type of laser refractive surgery to correct nearsightedness. It can also be used for mild degrees of hyperopia (farsightedness) and astigmatism.
You will also see this treatment being referred to as LASEK and involves a minor difference in the handling of the surface skin layer. However, both procedures are identical in visual outcomes and pain. PRK is the most common of these two ‘surface ablation’ techniques.
PRK was the first type of laser eye surgery for vision correction and was first performed in 1988. It is the fore-runner to the most commonly performed procedure: LASIK.
PRK recovery takes a longer than recovery from LASIK eye surgery, between 3 and 5 days for most patients. During the first 2-3 days the eyes are often irritated and vision is not very clear.
PRK is still commonly performed and is used mainly when LASIK is not possible, for example a thin cornea or when the patient expresses a preference. Like LASIK excimer surgery, PRK works by reshaping the cornea allowing light entering the eye to be correctly focused on the retina for clear sight. With the WaveLight system, the excimer laser ablation is exactly the same for PRK and for LASIK.
For both PRK and LASIK, the excimer laser sculpts the stromal layer of the cornea to correct your prescription. The main difference between PRK and LASIK is that with LASIK a thin, hinged flap is created on the cornea to access the inner layers; in PRK no flap is created – just the surface skin layer is removed and the excimer laser energy is applied to the top layer of corneal collagen (the stroma).