By David F. Chang MD
What is a medical laser?
Lasers use energy from an invisible microscopic beam of light to treat tissues in the body in a very precise manner. The earliest medical uses of lasers were for the eye. Ophthalmic lasers are therefore precision “instruments” which can be used to treat different parts of the eye in a variety of ways. Eye treatments continue to be the most common application for medical lasers today.
The microscopic light beam of a laser must be able to reach the target organ. Since light cannot pass through skin, an incision is necessary to treat an internal organ, such as the liver, with the laser. The eye, however, is unique because the transparent cornea in the front acts as a window. Since light sources (such as a laser beam) can be aimed through this window, no incision is needed in order to reach areas inside the eyeball with the laser. Lacking an incision, eye laser treatments are not considered true “surgery”. There is no potential for infection or wound complications, and no need for reduced physical activities.
For many eye conditions, the laser can substitute for the need for surgery. Examples would include the treatment of 1) glaucoma inadequately controlled by medication, 2) clouding of the support capsule that may follow cataract surgery, 3) certain eye tumors, and 4) numerous retinal conditions, such as tears, diabetic complications, and abnormalities of the circulation. Each of these various eye conditions is treated with different types of lasers and in a different way. The prognosis and the patient¹s experience will therefore differ, depending on what part of the eye, and what condition is being treated.
Why is a laser treatment sometimes needed after successful cataract surgery?
A cataract is the clouding of the natural human lens. The human lens is suspended inside the eye and encased by a delicate, cellophane-like wrapper called the “capsule”. With modern cataract surgery, it is possible to make a large hole in the front of the capsule, and extract the cloudy lens while preserving the rest of this delicate capsule. The remaining capsule, which is like a clear, transparent sac, is then used to fixate the implant in the same original location of the natural lens.
Since there is a surgical opening in the front of the capsular sac, the back of the capsule (behind the artificial lens) is the only portion that we actually look through. This is called the “posterior capsule”. Although the cataract cannot recur, cells can adhere to the posterior capsule, and like layers of dust accumulating on a window, result in a clouding that appears months to years following the original surgery. This will slowly cause a progressive reduction of vision. Despite the potential for future clouding, there are other important advantages in having the posterior capsular remain intact for the first few months after cataract surgery.
To see through a wall, we construct a window. The rest of the wall continues to support the ceiling. Likewise, it is not necessary to remove the clouded capsule in order to restore clear vision. Instead, a small hole or “window” is made in the center of the posterior capsule to allow for a clear view. This permanent hole is about one-eighth inch in diameter, and will not close later. The rest of the capsule remains intact to support the implant as securely as before.
Historically, a special knife would be inserted through a surgical incision to create this opening. Since 1984, however, the need for this surgery has been replaced by the YAG laser. Rather than a metal blade, the painless “instrument” used is this specially focused beam of laser light. Since light can be focused through a transparent window, such as the cornea, an incision is not needed.
Does everyone need the YAG laser procedure after cataract surgery?
One of the main objectives of cataract surgery is the preservation of the lens capsule. Like a healing response, the tendency for the capsule to later cloud varies with the individual. Many patients will never develop this clouding. However, because it is an individual eye reaction, there is no way to totally prevent its occurrence. It is more likely to develop in younger patients and following certain types of cataracts. It is not a complication and it is not considered a serious problem since it can be corrected without surgery. Once the hole is created by the laser, it will remain open. The laser procedure will not have to be repeated again.
What is the laser treatment like?
The YAG laser procedure will be performed at the Peninsula Eye Surgery Center, located one mile from our office. You should prepare for your laser treatment just as you would for an eye examination. There is no need to change clothing, and there are no restrictions on diet, exercise, reading, or TV following the treatment. Your regular medications, such as pills or eyedrops, should be taken at the normal times.
You will be seated at an eye microscope similar to that used for a routine eye exam. The microscope is used to steady your head, and to focus and administer the laser treatment. A special focusing lens will be placed on the eye to control eye movements and to prevent the lids from closing. Anesthetic drops are used to numb the eye. Because the amount of laser energy is so small, there is no effect on the other eye or other parts of the body. There is no pain involved. There is a clicking sensation as the laser is administered. The series of multiple clicks represents the many tiny applications used to create the opening in the cloudy capsule. Since the capsule is naturally on stretch, each microscopic knick will result in a progressively larger opening until the optimal size is attained.
Following the treatment, there may be temporary blurring for a few minutes. The eye may be slightly irritated later in the day. Pain is uncommon, and a bandage is not necessary. Improvement in the vision may be noted later on that same day, or by the next day. The laser treatment does not change the eyeglass prescription. However, since the vision was sub-optimal upon the pre-laser eye exam, a follow-up visit may be arranged to recheck the vision and the glasses prescription.
Are there risks to the YAG laser procedure?
This procedure is indicated if a hazy capsule has caused a permanent, and significantly bothersome blur. The risks are fortunately minimal. Changes in the eye fluid pressure and in the retina can occur independently as a result of age. In predisposed eyes, these changes could rarely be precipitated by a laser procedure. Such changes would usually be treatable. Most important of all, use of the YAG laser avoids other risks specific to actual surgery (e.g. bleeding or infection).
Small temporary floaters may appear immediately following the laser treatment. These are microscopic particles from the capsule, and will eventually float away. They are separate from the permanent floaters in the vitreous gel that most patients develop as a function of age.