P 169 Comparison of various masking agents for phototherapeutic keratectomy: An experimental in vitro study

Purpose: To discriminate the potential role of corneal shape-factors versus opacily li~ctm’s Ibr lhc linal viwd outcome (II‘ I’ IK using comc:~I topography. Methods : PTK were performed witn a Summit Excimed 200 UV C for the treatment of various comeal conditions in 135 patients including Recurrent Epithelial Erosions (n=41). Band Keratopathy (n=35), Epidemic Kerato-Conjunctivitis (n=l I), S&man’s degeneration (n=9), Anterior Stromal Dystrophies (Granular n=lS Reis-Biicklers n=O), and Lcukoma (n=lS). Cornea1 topography was assessed preoperatively and Iw, 2~. Im, 3m, 6 months and I year postoperatively using both CAS-1 (ES) and TMSI (TM) systems. Results : Best corrected visual acuity remained stable in 39.5% ofpatients, and improved in 51.4% (with a gain of2, 3 and 4+ lines for 1 I% 14%, 26% respectively). Spherical equivalent shifted from +0.25*4.75 preoperatively to +I .96i3.18 at 3 IllmlIIls. -1-2.46 b4.96 ;I1 6 Ilwllllls :md 12.47 I4 RX ill I1IlC year. A~~nlysis 01‘ cwnc~d powx di:tributiou ~cvc;ilcd a 11011 signilicanl comeal flattening from preoperative vnlues (ES 44.0*3.81), ‘TM 43.49+3.28D) to 6 months values (ES 42.49*2.360, ‘I’M, 42.24zt2.230). and I year values (ES 41.79*2.68D, I’M 42.4743.77). Analysis of TMSI regularity and asymetry indexes indicated a non signiticant postopcmtivc improvcmcnt of SRI (2.82h2.22 to 1.65+1.05) and SAI (1.46*1.67 to 1.14*1.53)atoneyear. Conclusion: These results suggest that quantitative comeal topogaphy analysis correlate well to visual improvement following PIX COMPARISON OF VARIOUS MASKING AGENTS FOR PHOTOTHERAPEUTIC KERATECTOMY: AN EXPERIMENTAL IN VITRO STUDY IM.Assoulioe, l,*hl.Muller-Stfinwaehs, kkHarts~ann, ‘G.Renard, ‘Y.Pouliquen lCHU H;tel-Dicu de Paris ( France), *U. Kiiln (Germany), 311. llosp Cbarili. llcrlio (Germa~~y). Purpose: ‘To investigate tl1e ability of compounds with various specific gmvily, viscosity and contact angle to enhance uxcimcr law phototherapeutic ablation (PTK) of irregular surlkes. Mctbods: PMMA contact lenses were used to model the convex spherical surface of the cornea. A repeat. standardized. square shaped (I 00x I OOx5Op) surface dcfcc1 pattcm was uc31cd. SU~SC~IIICIII pl1otwblaliot1 of this irrcynlnr surface (200, 500 and 700 pulses in a triplicate design), was performed using 4 masking agents, including Balanced Salt Solution (BSS), Sodium Hyaluronatc (IlaNa), liquid perfluorodccalin (DKL) or a molded 0.6% ~garose Gel (AGG). Scanning electron micrographs were obtained under standardized conditions (45”, 200x) and processed by image analysis. Results: Photoablation of the lens without a masking agent did not significantly affect tl1e shape or size of the microexcwations. At 200 pulses, BSS provided the most effective smoothing enhancement action, Ieducing the dcfcct volume indcs from 512.9118.2 kp3 (conl~l) to l3f.l.5+6.4 kp3 (p<O.OOOl). AGG. Nalla, and DKL were less effective (167.1134.1, 231.6i26.8, and 297.1428.9 kp3 respectively, p<O.OOl). At 700 pulses. NaHa produced an almost flat surface devoid of distinct defects, such as tl1ose persisting with BSS (6.2+4.1 kp3) or DKI. (122.1*21.6 kp3). Conclusion: These results suggest that BSS and HaNa may be the most appropriate masking agents for low and high dose I’TK respectively.