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combined with topographic guided photorefractive kera- tectomy, intracorneal ring segments, phakic IOLs, and as a last resort, corneal trans- plantation, while also includ- ing surgical techniques, clinical outcomes, and possi- ble complications. For example, complica- tions for intracorneal ring segments, although rare, in- clude microbial keratitis, im- plant extrusion, corneal thinning in the area over the segment, and reduced corneal sensation. "The formation of white, fine deposits is frequent in- side the tunnels around the segments," the researchers 56 EW REFRACTIVE SURGERY 56 May 2011 by Faith A. Hayden EyeWorld Staff Writer PRK no better than LASIK for dry eye patients 6<0326,$723,&6 &DWDUDFWDQG(QGRWKHOLXPHVFUV(X&RUQHD6\PSRVLXP )HPWRVHFRQG&DWDUDFW6XUJHU\ 5HIUDFWLYH$GMXVWPHQWVDIWHU2FXODU6XUJHU\ 'HFLVLRQPDNLQJLQ3UHVE\RSLD $SKDNLDDQG$QWHULRU6HJPHQW5HFRQVWUXFWLRQ SUHOLPLQDU\SURJUDPPHRQOLQHDW ZZZHVFUVRUJ 6(37(0%(5 5(('0(66( 9,(11$ $8675,$ (8523($162&,(7<2)&$7$5$&7 5()5$&7,9(685*(216 wrote. "The incidence and density of the deposits increases with the thickness of the segment and the implantation time. Among the vi- sual symptoms reported by the pa- tients are diplopia, halos, difficulty in night vision, vision fluctuation, and photophobia." For phakic IOLs, the researchers go over how to implant a Collamer Lens (STAAR Surgical, Monrovia, Calif.), calling it an "attractive alter- native for correcting myopic and astigmatic defects in patients with a stable keratoconus." The greatest impact, though, will come from collagen crosslink- ing, stated the researchers. "Collagen crosslinking probably shows great promise and based on current data will have the greatest impact in hopefully reducing or delaying pro- gression of keratoconus, allowing patients to tolerate spectacles and contact lenses," they wrote. "The traditional approach to keratoconus is done, which is fortu- nate for this group of patients," said Dr. Daya. "This condition is not un- common. In the U.K., the preva- lence is about 1 in 2,000. For a fairly common disease, we have a lot more options available. It used to be mis- erable for these patients, but we can do a lot more for them now." EW Editors' note: The physicians inter- viewed have no financial interests re- lated to their comments. Contact information Daya: sdaya@centreforsight.com Guell: guell@imo.es The surgical continued from page 55 Source: Edward E. Manche, M.D. A patient's pre- and post-collagen crosslinking topog- raphy. Doctors now have a variety of options for treating ectasia, including crosslinking, intracorneal rings, and phakic IOLS Source: A. John Kanellopoulos, M.D. Both procedures cause mild discomfort P RK and LASIK are equals in the refractive surgery world for dry eye patients, reported Edward E. Manche, M.D., Stanford University School of Medicine. In a small, randomized, prospective study, 34 subjects had one eye treated with wavefront-guided LASIK and the other treated with wave- front-guided PRK, for a total of 68 eyes, to compare the post-op signs and symptoms of dry eye, dry eye severity, foreign body sensation, and vision fluctuations in myopic pa- tients. "It's conventional wisdom to suggest that PRK creates less dryness than LASIK in patients undergoing refractive surgery," Dr. Manche said. "It makes sense physiologically. You can argue that with LASIK, you're severing corneal nerve fibers further in the periphery and going deeper because you're creating this flap, so you may have a more profound den- ervation in the early stages. With PRK you're doing a laser ablation centrally and you're not catching those larger diameter nerves periph- erally." But Dr. Manche discovered that the conventional wisdom, at least in this case, was wrong. He found no differences in overall dry eye symp- toms, with both groups having a mild increase in symptoms of for- eign body sensation in the early post-op period. As 1 month turned into 3, and 3 into 6, and 6 into 12, dry eye symptoms gradually de- creased and eventually ended back at baseline. Dr. Manche acknowledged that there is "probably some literature to support" the PRK for dry eye patient thought process because the argu- ment makes sense on a physiological level. "There is some literature that shows that corneal nerve sensation is greatly reduced, at least early on in LASIK compared with PRK. I think that's where this came from," he said. The single most common side effect of LASIK and PRK is still in- creased dryness of the eye, and pa- tients should be made aware of that fact. Thirty to 40% of patients will have dryness in the first several months, and it will gradually get better in the vast majority of people. However, about 5% of patients will have persistent long-term dryness of varying degrees, he said. The only difference Dr. Manche found between the two refractive methods was in increased visual fluctuation in PRK patients, but that is no reason not to use it. "LASIK has the advantage of rapid visual recovery," he said. "PRK takes longer and the visual fluctua- tion is because there are still epithe- lium irregularities at 1 month. That's why I think we don't see as many PRKs done as LASIK procedures, be- cause people want fast recovery." "Although not in this particular study, we've shown that the out- comes of uncorrected visual acuity, best corrected visual acuity, low con- trast, and patient satisfaction are identical in PRK and LASIK," he said. "The clinical outcomes are the same." EW Editors' note: Dr. Manche has no finan- cial interests related to his comments. Contact information Manche: eemanche@yahoo.com

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