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LASIK improves functional results of PKP
PKP is successful in most cases, but functional results can be disappointing, leaving patients with highly impairing ametropias.
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ROME – LASIK can effectively improve the functional success of penetrating keratoplasty (PKP) by correcting the postop spherical and cylindrical ametropias that often hinder the functional success of the operation.
“LASIK has a much higher rate of success than other types of surgical correction, which so far have been very unsatisfactory,” said Thomas Neuhann, MD, speaking here at Rome 2001
Prof. Neuhann pointed out that PKP achieves surgical and anatomical success in most cases, but functional results are often disappointing, when patients are affected with visually disturbing ametropias.
“We must admit that a functionally unusable surgical success is close to failure. What’s the point of having a clear graft if you can’t see well at all?” he said.
Successful cases
Regarding the current options for the correction of functionally impairing ametropias after keratoplasty, Prof. Neuhann said that astigmatic keratectomy is highly unpredictable in keratoplasty and lensectomy with custom toric IOL implantation is very invasive.
“You don’t want to make everyone lose their lens just to be able to use their otherwise good corneas,” he said.
LASIK is much safer and more effective, according to his results on 33 eyes that have now completed a 12-month follow-up.
“I operated on keratoplasty patients who had spherical and cylindrical ametropias not tolerably correctable with spectacles or contact lenses. They had a minimum postoperative course of 24 months after keratoplasty and were required to have stable topography for at least 2 months,” he said.
Mean sphere was –1.75+2.9 D, and mean cylinder was –5+2.2 D.
“We used a two-step approach,” he explained. “We dissected the flap with a Hansatome 4 weeks in advance to rule out refractive changes caused by the flap itself. After 4 weeks, we lifted the flap and performed the ablation with a Keracor 4217.”
High predictability
Predictability of the technique is very high, Prof. Neuhann said. Spherical predictability (figure 1) was 51% within +0.5 D of target, 94% within +1 D of target and 100% within +2 D of target.
“These results, considering what we are dealing with, are very good. Cylinder correction (figure 2) was obviously a little less good, but we still had almost 40% of the eyes within +0.5 D of target, 51% within +1 D and 76% within +2 D. All of them were at least 3 D within target,” he said.
The sphere was shown to be relatively stable (figure 3).
“It takes some time to stabilize, and after 12 months we can see a very small shift of about –0.5 D away from target. The cylinder also stabilizes after a certain period (figure 4), and the good thing is that in time it gradually approaches target. After 6 months, or at least after 12 months, it is relatively stable in the range of –1.5 and –1.1 D of target,” he said.
Safe and effective
Safety was also proved to be very high (figure 5). After 12 months, 100% of patients had lost no lines or were within one line of preop best corrected visual acuity (BCVA), and 90% had achieved these results at shorter time periods.
Efficacy had very high standards (figure 6). Comparing postop uncorrected visual acuity with preop BCVA, 87% of eyes were within one line.
“We cannot expect from this application of the technique the same results that we obtain with regular LASIK. Stabilization takes longer, and the success threshold is much lower, because the target is lower. However, I find the results extremely encouraging,” Prof. Neuhann said.
“So far, we have been able to correct up to 9 D of astigmatism, which is a remarkable achievement, I think. You can get much better results with cross-cylinder ablation than with simple-cylinder ablation. Improvement and a perfect alignment of the axis can certainly be obtained, which is especially important with high cylinders.”
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For Your Information:
- Thomas Neuhann, MD, can be reached at Helene-Weber-Allee 19, D-80637 Munich, Germany; (49) 89-159040; fax: (49) 89-15940555; e-mail: ThomasNeuhann@compuserve.com.
- Rome 2001, the Rome Symposium on Cataract, Glaucoma and Refractive Surgery, was co-sponsored by Ocular Surgery News Europe/Asia-Pacific Edition, The Italian Association of Cataract and Refractive Surgery and the International Society of Refractive Surgery. For information on future meetings, contact Meeting Registration at (856) 848-1000.