OTHER REFRACTIVE SURGICAL PROCEDURES
Dr. Espinosa's candid remarks about them.
INTACS (INTRASTROMAL CORNEAL RING SEGMENTS -ICRS)
The Intacs (also known as intrastromal corneal ring segments, ICRS or ICR) were approved on April 9, 1999 by the Food and Drug Administration (FDA) for use in the United States. Two 150° thin strips of plastic 1.5 mm wide made of polymethyl-methacrylate (PMMA) are inserted into the stroma of the cornea (below the epithelium and Bowman's membrane) at approximately 2/3rds depth in the form of a circle. There are six thicknesses ranging from 0.25 to 0.50 mm depending on the amount of nearsightedness. Night vision has been reported as being slightly better with the Intacs than with LASIK but the Intacs may produce more glare than LASIK. Studies have shown that 80% of persons having this procedure attain 20/20 visual acuity or better. The procedure is reversible.
The amount of nearsightedness that the Intacs can correct is up to -4.50 to -5.00 diopters. Astigmatism and farsightedness cannot be corrected by the Intacs. The ring is easily visible with the naked eye.
FDA tests are currently being conducted with Intacs on hyperopic patients as well. The range of correction will be from +1.00 to +3.50.
Intacs are also being used, off label, for keratoconus which are proving to be significantly effective. More information will be coming out in the future on this treatment modality for keratoconus.
Opinion: The Intacs are limited to a select number of myopes only - those between the range of -1.00 to -5.00 (approximately). The fact that this procedure is reversible in most - but not all - cases is very appealing to my patients.
All refractive surgical candidates must be thoroughly educated about the risks and benefits of LASIK or other contemplated refractive surgical procedures prior to undergoing any procedure. My patients have to convince me that they fully understand the risks and benefits of their planned surgery before referral. This way I feel confident that they are going to be happy with their results.
LASEK is very similar to PRK. A flap is created, not by cutting the cornea as in LASIK, but by applying a 20% alcohol solution to the cornea loosening the epithelial layer allowing the surgeon to gently move the epithelium to one side. This allows the surgeon to then use the excimer laser to correct higher refractive errors because of the added corneal thickness made available by this technique. After the laser is applied, the surgeon then gently moves the epithelial layer back over the cornea for faster healing than PRK. Similar to PRK, a soft contact lens is placed over the eye for 2-3 days.
This procedure is less painful than PRK with faster healing. While LASEK is not for everybody, it is certainly a refractive surgical modality that is highly effective, especially with larger refractive errors. I do recommend this procedure.
For very high refractive errors that are beyond the range of LASIK, a Clear Lens Extraction can be used because it's the same thing as performing cataract surgery except that it is performed on a clear lens rather than a cataractous lens.
When one has a cataract, the crystalline lens becomes cloudy reducing vision. The crystalline lens is then removed and replaced with an intraocular lens (IOL) with the calculated correct power allowing the eye to see again.
Several million cataract procedures with an IOL implant have been performed over the years. Thousands of these procedures are performed every year. In fact, cataract surgery is the most common surgical procedure of ALL surgical procedures in the United States. Therefore, if it is such a common and safe procedure to perform, I have little hesitation in recommending this procedure for patients with very high nearsightedness or farsightedness.
Astigmatism can be corrected as explained for the ICL below.
PHAKIC INTRAOCULAR CONTACT LENS IMPLANTS (ICL) (see diagram above)
The Staar lens is made from a polymer/porcine- collagen based biocompatible material. It consists of a plate-haptic design with a central convex/concave optical zone. This design is consistent with Staar Surgical Company's existing technology for cataract surgery modified to minimize the IOL's contact with the crystalline lens.
This lens is inserted into the eye in a manner similar to cataract surgery. It is inserted through a very small incision (3 mm) and is placed between the anterior surface of the crystalline lens and the posterior surface of the iris. Possible side effects include corneal edema, iritis and pigment deposits.
This lens is similar to the Staar Lens. It is a four-point, angle-fixed anterior chamber IOL designed by Georges Baikoff, M.D. It has been shown safe and accurate up to 26 D. of myopia.
Verisyse (The Artisan Lens)
The Verisyse lens (formerly the Artisan Lens) is also referred to as the "Claw Lens" because the lens is designed in such a manner as to "hook" onto the midperiphery of the anterior iris with or without sutures. It's an iris-fixated lens with a 5 mm optic zone. Some surgeons prefer the Verisyse Lens over the Staar lens because it is located further away from the anterior surface of the crystalline lens thereby reducing the probabilities of the two lenses touching. A small peripheral iridotomy is often needed with this type of lens.
All advantages and disadvantages discussed for the Staar lens are also applicable to the Verisyse Lens except that there are no reports of correlation with the Verisyse Lens and postoperative cataracts. The Verisyse Lens was approved by the FDA in September 2004.
It has become common now to perform standard LASIK after the CLE/ICL procedure in order to correct for astigmatism and other residual refractive errors.
Opinion: The phakic intraocular contact lenses described above are very useful to persons with very high refractive errors. The incidence of secondary cataracts as a result of the Verisyse (Artisan) lens is reported to be much less than with the Staar lens. Therefore, I would prefer the Verisyse (Artisan) lens over the Staar lens at this point in time.
The holmium yag laser uses infrared light which causes tissue to constrict as it heals. Multiple spots are placed in the peripheral cornea causing the corneal tissue to constrict. This causes the cornea to become steeper centrally to compensate for the farsightedness. LTK has been approved by the FDA. This laser is known as the Sunrise Hyperion LTK.
Opinion: The holmium laser is a "hot" laser which burns tissue. It reshapes the cornea by causing the tissue to constrict producing collateral tissue damage due to the heat. Because of this, the results are not as predictable as with the excimer laser which is a "cold" laser. The effects with the holmium laser tend to lessen over time which means the farsightedness may return.
RADIO FREQUENCY KERATOPLASTY (also known as Conductive Keratoplasty - CK)
Refractec's ViewPoint CK system for conductive keratoplasty uses high frequency radio waves to reshape the cornea and is used to correct hyperopia, astigmatism and presbyopia and was approved by the FDA in April 2002.
The procedure appears similar to LTK mentioned above except that LTK utilizes the holmium laser to create the collagen shrinkage required. The CK proponents claim that their techniques produce no collateral damage, as with the holmium laser, because "...CK uses the natural electrical conductive characteristics of the corneal tissue to deliver energy. Usually less than 1 mJ of energy is delivered only to areas the surgeon has selected for shrinkage with a handheld probe and disposable 90- mm penetrating tip, which is inserted about 450 mm into the stromal bed." (Primary Care Optometry News, March 1999, p. 33) "Thermal spots are placed in a ring of applications around the periphery of the cornea to create at least two intrastromal corneal bands at 6 mm. and 7 mm. If a third ring is required to correct hyperopia, it is created at 8 mm. Each ring, which consists of eight spots, induces a retraction in corneal collagen cells at the sites of application. Up to three rings have been successfully used in clinical trials in Latin America to treat up to 3 D of hyperopia." (ibid, p. 34). Refractec Inc., the company developing this technology, is located in Irvine, California.
Opinion: The RFK procedure appears to have the technical superiority over the LTK procedure in that the amount of collateral tissue damage is less with RFK. RFK, however, is more surgeon-dependent than LTK.
This procedure is currently under investigation in Tijuana, Mexico by Chayet and Assil. Six polymethylmethacrylate (PMMA) segments varying in length from 1.5 to 2 mm can be inserted into the corneal stroma in order to cause a steepening of the cornea to correct for farsightedness from +1.00 to +5.00 diopters. I do not recommend this procedure to my patients at the present time especially since hyperopic LASIK has been approved by the FDA in the United States to correct for hyperopia in this range.
Attempts are being made to remove stromal tissue without lifting a flap as in the LASIK procedure. Different lasers are being tested to see if this is possible with reliable predictability. If the results are good, recovery would be even faster than with the LASIK procedure.
PRESBYOPIC REFRACTIVE SURGERIES - A brief summary (Dr. Espinosa does NOT endorse any of the following procedures.)
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