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LASIK study: good results shown for hyperopic patients with prior refractive surgery
Preoperative keratometry, however, is one of the key factors, according to the study’s author.
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MINNEAPOLIS — There is good news for patients undergoing laser in situ keratomileusis (LASIK) for the correction of hyperopia and hyperopic astigmatism following previous myopic refractive surgery.
“These patients are responding very well to hyperopic LASIK — better than I would have anticipated,” said Richard L. Lindstrom, MD, who used the SmoothScan (Visx Inc., Santa Clara, Calif.) excimer laser system in a group of 30 eyes with either consecutive or progressive hyperopia (average age 47). Nearly 40% of patients had a best corrected visual acuity (BCVA) of at least 20/20 at 3 months and 90% were at least 20/40. “We had a stable result within a few days. There was no large overshoot,” Dr. Lindstrom reported.
The previous refractive operation for most of these patients was either radial keratotomy (RK) or LASIK, and many have astigmatism. At 1 year, about 85% of eyes were within ±1 D of desired correction. “These eyes are looking more stable than our naturally occurring hyperopes,” with standard deviation in the ±0.8 D to 1 D range, Dr. Lindstrom said.
Stability a non-issue
---The previous refractive operation for most of these patients was either radial keratotomy (RK) or LASIK, and many have astigmatism.
“I was concerned that we might see less stability in this group,” according to Dr. Lindstrom, who spoke at the European Society of Cataract and Refractive Surgeons meeting in Vienna. Particularly in the RK patients, “1-day results were almost the same as 12 months.” The photorefractive keratectomy (PRK) and LASIK eyes “had a little bit of regression, but it was significantly less than in the naturally occurring hyperopic patients. The 6- and 12-month data points are almost identical.”
Dr. Lindstrom is reassured by the fact that at 1 year, “we don’t have any loss of BCVA. But we did have some loss of BCVA of a line or two all the way out to 6 months. Fortunately, this seemed to improve with time.”
On the other hand, one eye developed an epithelial ingrowth. “I don’t know if hyperopic treatment is more prone to epithelial ingrowth because it is very rare for us to see that in our myopes of late, or if it is because we simply have a relatively small series of eyes, whereby just one patient shows up as a meaningful percent,” he said.
In any event, Dr. Lindstrom believes that a stable result is achieved at 12 months. “If you program 1 D into the SmoothScan, you get a lower effect — about 0.67 D,” he said. “And if you program the laser for a naturally occurring hyperope, you end up with 0.89 D.” However, for a patient who has had previous refractive surgery, 1 D creates more effect: 1.06 D.
Corneal shape
---Dr. Lindstrom states that he does not know if hyperopic treatment is more prone to epithelial ingrowth because it is very rare for him to see that in myopes of late.
Dr. Lindstrom said that “one of the key factors in the nomogram is the preoperative keratometry. So if you start with a very flat cornea, you’re going to achieve a different result than if you start with a steeper cornea. Clearly, the consecutive hyperope has a much different corneal shape than does the naturally occurring hyperope. In fact, it influences the results a lot more than I would have anticipated in advance.”
Still, he said, “it is somewhat age-dependent.” Nonetheless, “if you simply put the same reading in for all the different hyperopes and all the different classes, I think you’ll have much less desirable results.” In essence, Dr. Lindstrom added, “the nomograms are going to be important in LASIK, just like they are in other forms of refractive surgery.”
Dr. Lindstrom related the pleasure he derives from helping his hyperopic patients. “A decade after performing RK, I have the same patients coming in,” he said. “I bring them into the laser room and ask them if they can read their watch, but none of them can. However, after performing hyperopic LASIK, patients sit up and can immediately read their watch. It’s the same patients who smiled 10 years ago after RK, when they could read the clock at the end of the room.”
| Seven beam scanning |
| Visx Star S2 SmoothScan |
For Your Information:
- Richard L. Lindstrom, MD, can be reached at Minnesota Eye Associates, Park Avenue Medical Office Building, 710 E. 24th St., Ste. 106, Minneapolis, MN 55404; (612) 813-3600; fax (612) 813-3660; e-mail: rlindstrom@isrsonline.isrs.org. Dr. Lindstrom is a consultant for Visx and Bausch & Lomb.