Comparision of Clinical Results of Excimer Laser Correction of Myopia and Compound Myopic Astigmatism Using VISX 20/20B isionKeyTM / 영남의대학술지

PURPOSE: To compare the efficacy, predictability, stability and safety of excimer laser photorefracive keratectomy(PRK) for mypia and photoastigmatic refractive keratectomy(PARK) for compound myopic astigmatism. METHODS: Two-hundred-three eyes(118 eyes or =-7D spherical equivalent) received excimer laser correction for compound myopic astigmatism and 152 eyes(116 eyes or =-7D) for simple myopia. A VISX 20/20B VisionKeyTM excimer laser was used to perform either PARK or PRK. Visual acuity with and without correction, refraction, IOP, corneal haze, and topography were evaluated at 1, 3, 6, and 12 months postoperatively. All patients were followed up for more than 12 months. RESULTS: Postoperative refraction were generally stable after 3 months without significant early overcorrection. At 12 months, 110(94.8%) eyes that underwent PRK and 104(88.1%) eyes that underwent PARK achieved UCVA of 20/30 or better in the group who had lower than -7D correction. For eyes treated with -7D or more, these figures were 31(86.1%) eyes after PRK and 57(67.1%) eyes after PARK. The incidence of within 1D of plano refraction at 1 year follow-up were 97.4% after PRK and 93.2% after PARK in group who had lower than -7D correction. For eyes treated with -7D or more, there figures were 80.6% after PRK and 70.6% after PARK. CONCLUSIONS: Myopia with or without astigmatism was successfully treated in most of the eyes using PRK or PARK with VISX 20/20B VisionKeyTM excimer laser. The predictability and stability of the postoperative refraction during the first 12 months seem to be quite reliable. Futher improvement of excimer laser system and software should increase the clinical outcomes and safety of refractive procedures.

Clinical Result of Excimer Laser Photoastigmatic Refractive Keratectomy Using VISX 20/20 B VisionKeyTM with Version 4.01 Software

Photoastigmatic refractive keratectomy (PARK) using VISX 20/20 B excimer laser with version 4.01 software was performed in 205 consecutive eyes of compound myopic astigmatism to assess the efficacy, predictability, and safety of excimer laser treatment of compound myopic astigmatism between September 1994 and June 1996. The mean preoperative manifest spherical equivalent refraction was -6.95+/-2.52D (range -1.13 to -15D) and the mean preoperative manifest cylindrical refraction was -1.25+/-0.76D (range -0.5 to -4.50D). The patients were followed from 6 months to 1 year (mean 9.19 months). At 1 year, 82(75.2%) of all 109 eyes receiving PARK were within 1D of plano refraction, and 88(80.7%) of all 109 eyes achieved uncorrected visual acuity of 20/30 or better. Postoperative refractions were stable after 3 months without significant early overcorrection. Mean postoperative astigmatism was -0.29+/-0.40D at 6 months and -0.24+/-0.42D at 12 months. Overall improvement of astigmatism was 75% at 6 months and 82% at 12 months by vector analysis using Alpins` method. In conclusion, PARK using VISX 20/20 B VisionKeyTM excimer laser with version 4.01 software appears to be effective in the treatment of compound myopic astigmatism with a relatively high degree of accuracy and safety. The predictability and stability of the postoperative refraction during the first 12 months seem to be quite reliable.

Delayed Corneal Epithelial Wound Healing after Excimer laser Photorefractive Keratectomy

The purpose of this study was to evaluate the occurrence of delayed epithelial healing(DEH) and the factors associated with it after excimer laser photorefractive keratectomy(PRK) and to assess whether there are any difference in the clinical outcomes between the eyes of DEH group and normal epithelial healing(NEH) group. This retrospective study was done in 554 consecutive eyes which had eximer laser PRK(VISX 20/20B WisionKey system with central island removal program) by one surgeon(S.B.L) between September 1994 and April 1997 at Yeungnam University Medical Center. Mean reepithelializion time of all 554 eyes was 3.1+/-1.3 days. Delayed epithelial healing beyond postoperative 5 and 7 days after exicimer laser PRK were noted in 30 eyes(5.4%) and 8 eyes(1.4%) of all 554 eyes, respectively. Mean reepithelialization time of DEH group was 7.1 days(range 5~12 days). Occurrence of DEH after excimer laser PRK was not depending on sex, age, laterality, amount of attempted correction(-6D or -6D), type of procedure(PRK vs. PARK), use of Maclof, the order of operation(type eye vs. second eye) or the type of soft ware(version 3.20 vs. 4.01)(All: p>0.05). At 6 months after surgery, 16 eyes(64%) of total 25 eyes of DEH group achieved UCVA of 0.7 or better, and 14 eyes(56%) were within +/-1D of emmetropia. In the NEH group. 349 eyes(84.7%) were UCVA of 0.7 or better, and 365 eyes(88.4%) were within +/-1D of emmetropa. There was statistically significant decrease in the clinical outcome of DEH group being compared with NEH group(p<0.05) In conclusion, prompt management for complete epithelial wound healing should be done in the cases of delayed epithelial healing after excimer laser PRK because it can cause the decrease in clinical outcome. Further studies assessing the effects of numerous topical medications, preservatives and software on epithelial healing after exicimer laser PRK would be performed.