This article is more than 5 years old. Information may no longer be current.
Small study in Cleveland finds LASIK effectively reduces high myopia
CLEVELAND--Laser in situ keratomileusis (LASIK) was found to be a safe, effective procedure with good predictability and visual outcome in a recent study of 30 patients followed by three comanaging ODs in the Cleveland area.
All preoperative and postoperative care was provided by Jeffrey J. Augustine, OD; Robert Bevington, OD; David Gale, OD; and Karen B. Murray, OD. The initial surgery was performed by Jeffrey J. Machat, MD, chief surgeon, TLC The Laser Center, Windsor, Canada.
Of the 30 subjects evaluated (13 males and 17 females), two were optometrists. The mean preoperative spherical equivalent was -8 D with a range of -4.62 D to -13.87 D. The average preoperative cylinder was -2.20 with a range between -0.25 DC and -3.25 DC.
Mean follow-up postoperative care was three months, at which time a mean spherical equivalent was equal to -.75 D, with a range of +1 D to -4 D. Subsequent enhancements are pending on three patients. The average postoperative cylinder was -.44 DC with a range of -.25 DC to -1.75 DC.
Postoperatively, 83.3% of patients had an uncorrected visual acuity of 20/40 or better, 37.5% had a visual acuity of 20/25 or better, and myopia was reduced in 100% of patients.
Old procedure revised
LASIK combines a 30-year-old, established lamellar keratectomy with the precision of photoablating excimer laser. LASIK is considered especially effective in cases of high myopia and astigmatism, where other refractive surgical procedures fall short or are accompanied by longer visual rehabilitation.
The surgeon creates a corneal cap with a hinge using the automated microkeratome. The microkeratome travels approximately 80% of the way across the cornea at 160 microns in depth, creating a 9 mm cap attached by a hinge. This provides for a smooth stromal bed for ablation. After myopic photoabalation, the interface is cleaned and dried and the final step is to reposition the corneal lamellar flap. The corneal epithelium is preserved to provide a dramatic and rapid visual recovery and Bowman's layer is preserved to provide long-term corneal integrity.
Postoperatively, the patient is placed on Tobradex (tobramycin 0.3% and dexamethasone 0.1%, Alcon), one drop four times daily for one week, Voltaren (diclofenac sodium 0.1%, CIBA), one drop four times daily for two days and told to wear an eye shield during sleep for one week.
Follow-up care
The patient is examined on day one for evaluation of visual acuity and slit lamp examination to assess the corneal healing and to detect any non-pre-existing unintentional lesions.
Subjectively, the patients generally have little pain, but do complain of a mild foreign body sensation. Subconjunctival hemorrhages are common due to the microkeratome suction apparatus.
When examining the cornea, the cap edge needs to be evaluated for edge lift. The slit lamp beam should be set with optics and illumination parallel, with swinging slit apparatus at 45 degrees and the patient's head turned 45 degrees to properly assess the interface and stromal edema.
At week three, the cap and hinge should be examined, and any epithelial nests, lint or debris on the interface should be documented. Day one evaluations should also be repeated.
Serious complications are rare
Potential LASIK complications include ocular perforation. If the 160 micron plate is not inserted into the microkeratome properly, perforation can occur during cap formation as the microkeratome immediately cuts at 900 microns. In perforation cases, the surgeon will abort the case, repair the cornea and lens, which usually pops out of the eye since the intraocular pressure is at 65 mm Hg. Risk of blindness, overall, is about 1:1 million chances. Other less serious complications are epithelial interface nests which appear as gray haze growing under the cap edge, partial or total disc detachment and stromal haze.
At this early stage, LASIK appears to effectively reduce moderate to high myopia and expands the range of surgical correctable ametropia beyond that of incisional keratotomy and surface ablation excimer alone. Serious complications can occur but are rare.
A better understanding of fluid dynamics, wound healing and a refinement in instrumentation will clearly allow for more reproducibility and precision. It is also imperative that the comanaging optometrist have formal didactic and clinical training on all refractive surgery modalities and an understanding of refractive surgical corneal healing management.