The most commonly performed surgical procedure in the United States is cataract surgery. This operation usually involves an incision into the eye through which the opacified lens (cataract) is removed followed by the insertion of a plastic intraocular lens (IOL) in the same space which the cataract previously occupied.
The surgery is very successful resulting in a significant improvement in vision for most people within 2-4 weeks. However, a significant percentage of patients do not obtain clear vision or gradually start to lose their vision over a period of months. The most common cause of this process is an opacification of the posterior capsule.
The cataract is removed from the eye by 'shelling it out' in which a small, circular incision (anterior capsulotomy) is made through the front surface (anterior capusle) of the cataract and the cataract is removed mechanically through this opening. This leaves an intact back surface (posterior capsule) which is left in place to prevent any forward movement of the vitreous jelly which fills the eye behind the posterior capsule.
Although studies have shown some variation, it is believed that more than 1/3 of eyes which have had cataract surgery will eventually develop a clouding of this posterior capsule, usually due to a slow but relentless growth of epithelial cells remaining from the removed cataract. The consequence of this steady opacification is a reduction in visual acuity much like that seen when one tries to look through a 'steamed window'.
Until the early 1980's correction of this problem was performed surgically with the ophthalmologist cutting an opening with a very thin knife in the capsule. However, since then the same result has been obtained with the Nd-YAG laser which creates a small opening in the posterior capsule with a short series of bursts of laser energy.
The procedure is done as an outpatient and normally lasts only 3-5 minutes. A drop of topical anesthetic is placed on the operative eye. The patient is positioned at the slit lamp microscope attached to the Nd-YAG laser unit. Sometimes, a handheld focusing lens is placed on the cornea by the ophthalmologist. The laser beam is focused on the posterior capsule and activated by a foot pedal to make an opening in the capsule with anywhere from 1-50 applications of laser energy of approximately 1.0 millijoule of power.
The patient is free to leave immediately after the procedure and often notices an immediate improvement in vision. The only drawbacks to the operation are a slight increase in the chance of a retinal detachment and damage to the intraocular lens which is very, very close to the posterior capsule. Overall, the procedure of Nd-YAG laser posterior capsulotomy is very effective is restoring or creating clear vision.
People with myopia (nearsightedness) have long relied on glasses and contact lenses to obtain clear vision. In the early 1980s the surgical procedure of radial keratotomy (RK) introduced an alternative. Unfortunately, many persons have avoided this surgery because of the complications, i.e., unpredictability, fluctuating vision, glare, halos, loss of structural integrity of the eye, and the invasive nature of the surgery itself.
In October of 1995 the Food and Drug Administration approved the excimer laser manufactured by Summit Technology Inc.for the purpose of correcting nearsightedness. Persons with stable myopia ranging from -1.5 diopters to -7.0 diopters with astigmatism of 1.50 or less are now eligible to receive this extraordinarily effective treatment. The procedure of Photorefractive Keratectomy (PRK), reshapes the human cornea by application of laser energy to its front surface, producing a flattening effect. Approval was based on clinical trials of more than 1600 eyes followed for three years. Additional consideration was given to studies from Canada and Europe, where the procedure has been performed since 1987.
The most current results reported on PRK in the United States have utilized a 6.0 mm central treatment zone. The multicenter studies involved 398 eyes in 300 patients. The mean attempted correction was -4.23 D with range of -1.50 D to -7.80 D. Twelve months after the procedure, 98.8% of eyes treated had 20/40 or better uncorrected visual acuity; 80.5% of eyes saw 20/20 or better. Vision was stable (as opposed to RK.) The only adverse effects were minimal symptoms of halos and glare in 2.4% of eyes and a loss of best corrected visual acuity of two lines in 1.2% of eyes. (Note: it is likely that these minimal adverse effects will disappear when the 18 month point is reached.)
Both approvals were hailed by the American Society of Cataract and Refractive Surgery which offers state-of-the-art physician instruction and ongoing research and evaluation of PRK and other evolving refractive surgical corrective techniques. The American Academy of Ophthalmology has now certified the procedure as being safe and effective.
A related procedure is LASIK (laser assisted in keratomileusis) which involves treatment of the central cornea underneath a hinged flap of corneal tissue. It is extremely effective for persons with myopia greater than -6.0 diopters as it allows for a much more rapid return of vision and involves significantly less pain than PRK.
Other refractive surgery techniques now being investigated include the following:
It is expected by many ophthalmologists that the use of laser energy to treat nearsightedness, astigmatism, and possibly farsightedness will rapidly replace radial keratotomy (RK), a surgical procedure which utilizes a series of surgical incisions in the front of the eye. Radial Keratotomy has been used to correct nearsightedness in the United States for the last ten years. It has been the focus of a nationwide, multicenter study, Prospective Evaluation of Radial Keratotomy (PERK study) which demonstrated its effectiveness but also noted a disturbing progression of the surgical effect in a significant number of patients. Additionally, the predictability of outcome of the surgical procedure is much less exact than the eximer laser.
Other locations with useful information on this procedure are:
Dr. Dave believes that patients seeking a solution other than glasses or contact lenses will greatly prefer PRK for treatment of their nearsightedness rather than the surgical treatment of RK which has demonstrated its effectiveness, but also its potential for multiple problems. He feels that radial keratotomy will be abandoned by the end of 1996 and replaced by the evolving techniques of PRK and LASIK.
( Glaucoma )
Surgery to control glaucoma (elevated pressure inside the eye which left untreated may seriously damage vision) is usually unnecessary because of the success of nonsurgical, medical treatment. The usual sequence of thereapy for mild to moderate glaucoma is eye drops > pills > argon laser trabeculoplasty, although laser therapy is being utilized earlier and earlier in the course of treatment.
Argon laser trabeculoplasty (ALT) consists of the delivery of short bursts of laser energy to the fluid drainage area of the eye, located internally where the colored part of the eye (iris) meets the clear, curved, domeshaped front surface of the eye (cornea.) This area is know as 'the angle' and is appears microscopically as a sponge-like ring of tissue through which the fluid (aqueous humor) exits the eye, eventually draining into the veins which carry this fluid and blood away from the eye.
Originally, it was felt that applications of the laser energy would 'blast' larger holes in the spongy tissue of the angle, thereby 'opening up the drain.' Surprisingly, it is now believed that the laser energy shrinks the fibers of the spongy tissue of the angle, which then causes the adjacent 'holes' or spaces within the tissue to enlarge, permitting a more rapid flow of fluid through the area and reducing the pressure inside the eye. ALT is usually performed in an ophthalmologist's office or an outpatient surgery center. One eye is treated at at time. Eyedrops are instilled a short time before the procedure in order to prevent inadvertent elevations of eye (intraocular) pressure and to prevent pain or discomfort during and after the treatment. The patient is then seated at a slit lamp, which is the same eye examination equipment that all eye professionals have in their private offices to examine the eye. A small, handheld lens (goniolens) is gently placed on the front surface of the eye and held in place during the procedure by the treating physician.
A small aiming laser is then directed toward the areas to be treated; then, the ophthalmologist depresses a foot pedal which delivers a small burst of laser energy to the designated area. This sequence is then repeated as the aimining laser is moved in a circular fashion around the eye. (Dr. Dave's treatment settings usually are: 1.0 joule, 50 micron spot size, 0.1 second duration, 70-100 applications of laser energy.)
After the procedure, the patient will often resume some of the previously used eye drops; many times, a second eye drop will be prescribed for a few days. There is usually no pain or discomfort during or after the treatment.Three or more weeks after the procedure, a final assessment can be made regarding the success of the ALT. (In my experience, the frequency of totally curing the glaucoma is 60%; controlling the glaucoma is 37%; no effect is 3%.) In some cases the success of treatment lasts for only a number of years; in many cases it appears to be permanent.
This procedure is rarely used because the reason is relatively rare for its implementation. The indication for this production of a small hole in the colored part of the eye (iris) is the presence of narrow, occludable angles or the development of acute (sudden) glaucoma. The angle, as described above, must be of a certain size to allow the easy passage of aqueous humor to enter the drainage area. When it is narrowed, whether due to age, cataract, or other reasons, it can become suddenly totally closed (angle closure) with a consequent rapid elevation of intraocular pressure as there is now no way for the continuouly produced fluid to leave the eye.
The high pressure in the eye can occur in a matter of hours to days and is often associated with pain, redness of the eye, rainbow halos around lights, and blurred vision. If left untreated, the high pressure almost always results in blindness of the eye, by causing a resistance to blood flow to the optic nerve and retina.
Laser iridotomy 'opens the angle' by producing a small hole or holes, usually less than 0.5 mm, in the iris. This is accomplished with the argon or YAG laser, depending on several variables, such as the cause of the event, prior surgery on the eye, etc. It is almost always completely successful and permanent. There are virtually no side effects or complications, although the very unlikely possibilities of inflammation and creation of a cataract can occur. The actual procedure from the patient's point of view is similiar to argon laser trabeculoplasty.
Trabeculectomy is a twenty minute operation to establish a communication between the inside of the eye and the outside of the eye. It is performed in a hospital or outpatient surgery center. A small amount of local anesthetic to immobilize the eye is administered around the eye of the sedated patient. Then, the eye is held open by a small lid speculum, as the ophthalmologist makes a curved incision through the translucent skin-like covering (conjunctiva) of the white of the eye (sclera.) The surgeon then creates a partial thickness 'trapdoor' incision through the sclera with its hinge toward the clear cornea. The resulting 'flap' is then elevated and a small piece of the underlying tissue (trabeculum) is excised and removed from the eye. Then, a tiny piece of the iris is removed through this incision to prevent its occluding the newly produced drain from the inside to the outside of the eye. Several sutures which do not need to be removed are used to close the 'trapdoor' and the conjunctiva. The frequency of success of this procedure directly depends on the cause and severity of the glaucoma. The likelihood of a positive result can be increased by the application of an anti-scarring substance, such as Mitomycin or 5-Fluorouracil, at the time of the surgery. Complications can occur with the operation, but are fortunately usually treatable.
Glacuoma in blind, painful eyes is sometimes treated by destroying the ciliary processes, the strucures in the middle of the eye which produce aqueous humor. This has been done in the past with application of heat or cold; however, promising developments are taking place using direct laser cauterization of these tissues.
Valves can be implanted into eyes with severe glaucoma, although this is a major procedure performed by a relatively small number of eye surgeons.
Dr. Dave believes that argon laser trabeculoplasy (ALT) will be used much sooner in the treatment of glaucoma, as the longtime safety and present day effectiveness of ALT is now well established.
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