Analysis of photoastigmatic keratectomy with the cross-cylinder ablation.

Aim: The aim was to evaluate the safety and efficacy of the “cross-cylinder” technique in the correction of astigmatism. Setting and Design: A prospective interventional study from a university eye department was conducted. Material and Methods: The photoastigmatic refractive keratectomy (PARK) using the “cross-cylinder” technique was performed in 102 eyes of 84 patients with at least 0.75 D of astigmatism. The study population was divided into two groups: in the first group the preoperative astigmatic power ranged from –0.75 D to –3.00 D (group 1), in the second group it ranged from –3.25 D to –6.00 D (group 2). Group 1 included 82 eyes of 67 patients (29 males and 38 females) with a mean cylinder power of –1.90 ± 0.63 D, group 2 included 20 eyes of 17 patients (13 males and 4 females) with a mean cylinder power of -4.28 ± 0.76 D. All eyes were targeted for emmetropia. The results were evaluated using Calossi's vector analysis method. Six-month postoperative outcomes are presented. Results: Six months after PARK the mean sphere for the entire cohort was +0.28 ± 0.75 D (range +2.5 to –2 D), the mean cylindrical power was +0.33 ± 0.51 D (range +2.5 to –1.25 D) and the mean spherical equivalent refraction was +0.73 ± 0.81 D (range +1.75 to –2 D). Conclusions: The cross-cylinder technique may be safely used with predictable results for the correction of astigmatism.

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.

Excimer Laser Photore fractive KeratectomyPRKfor Low and Mode rate Myopia using VIXS STAR Excimer Laser System

Excimer laser photorefractive keratectomy[PRK]for low and moderate myopia[-2D~-6D]has been performed recently as a predictable and effective method for correcting myopia. We analyzed refractive change, postoperative visual acuity, and postoperative complications of 168 eyes[104patients]for 6 months and 33 eyes among them for 1 year after excimer PRK using VISX STAR excimer laser system from February 1997 to February 1998.Among the patients male were 8 patients, and female were 96patients.The myopic range was from-2.00 diopters[D]to -6.00D with astigmatism less than 3D.Uncorrected visual acuity of 4/5 or better was achieved in 91%postoperatively ;corrected visual acuity of 4/5 or better in 97%postoperatively.Eighty-eight eyes received spherical photorefractive keratectomy[PRK]to correct myopia ;80 eyes received photoastigmatic refractive keratectomy[PARK]to correct both myopia and astigmatism.In spherical PRK group the mean spherical equivalent was -4.67 +/-1.69D preopratively, 0.11 +/-0.93D 6 months after PRK, -0.31 +/-0.80D 1 year after PRK ;in photoastigmatic refractive keratectomy[PARK]group these figures were -4 .9 4 +/-1.42D, -0.37 +/-0.81D, -0.62 +/-0.78D, respectively.In the PARK group13.8%were undercorrected but in the spherical PRK group only 5.7% were undercorrected.So we report the ndercorrection rate of PARK group was relatively higher than that of spherical PRK group, but statisticallyinsignificant[Chi-Square test, p=0.075, but Relative Risk=2.65].We evaluated the surgically induced astigmatism by using both Jaffe and Clayman's vector-corrected methods.In the spherical PRK group the mean surgically induced astigmatism[SIA]was 0.83 +/-0.49D 6 months after PRK, 0.72 +/-0.47D 1 year after PRK ;in the PARK group these figures were 1.36 +/-0.71D, 1.29 +/-0.72D, respectively.The differences between the two groups were statistically significant[unpaired T-test.p=0.001].Astigmatism greater than 0.25D was reduced in 23.86%and induced in 55.68%of eyes that received spherical PRK and astigmatism greater than 0.25D was reduced in 80%and induced in 3.75%of eyes that received PARK.There were several complications including transient punctate keratopathies[6 eyes, 3.5%], undercorrection [-1D][16 eyes, 9.5%], and overcorrection[-1D][28 eyes, 16.67%].The decrease in the best corrected visual acuity in 10 eyes[5.9%] may be the result of a grade 2 or more corneal haze[15 eyes]and central island[2 eyes].

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.

Clinical Result of Excimer Laser Park

We evaluated the effectiveness of photoastigmatic refractive Keratectomy(PARK) by excimer laser on patients with compound myopic astigmatism. Spherocylindrical PARK was performed on 181 myopic eyes with astigmatism(mean spherical equivalent : -6.61 D, range : -1.88~-14.5 D) using the visx excimer laser. The eyes were divided into three groups according to the amount of desired astigmatic correction : Group 1(-0.5~-1.0 D), Group 2(-1.25~3.0 D), and Group 3(-3.25~-5.5 D). Patients were followed up for 6 months. Uncorrected visual acuity at postoperative 6 month, was 0.80+/-0.27 in Group 1, 0.79+/-0.19 and 0.71+/-0.21bin Group 2 and 3 respectively. The mean spherical equivalent refraction was -0.24 D 6 months after PARK. Mean astigmatism was reduced from preoperative -0.85+/-0.51 D to postoperative -0.34+/-0.38 D in Group 1, from -2.08+/-0.65 D to -0.43+/-0.64 D and from -4.42+/-0.63 D to -1.23+/-1.25 D in Group 2 and 3 respectively. We also analyzed the angle of error, magnitude of error, index of success, and coefficient of afjustment by vector analysis. No significant complications were observed during the follow-up period. These results show that PARK by excimer laser was effective in correction of astigmatism. The effect of astigmatic correction in Group 2 and 3 were better than that of Group 1. Group 1 showed overcorrected tendency and Group 2 and 3 showed undercorrected tendency.

Clinical Result of Excimer Laser Park

We evaluated the effectiveness of photoastigmatic refractive Keratectomy(PARK) by excimer laser on patients with compound myopic astigmatism. Spherocylindrical PARK was performed on 181 myopic eyes with astigmatism(mean spherical equivalent : -6.61 D, range : -1.88~-14.5 D) using the visx excimer laser. The eyes were divided into three groups according to the amount of desired astigmatic correction : Group 1(-0.5~-1.0 D), Group 2(-1.25~3.0 D), and Group 3(-3.25~-5.5 D). Patients were followed up for 6 months. Uncorrected visual acuity at postoperative 6 month, was 0.80+/-0.27 in Group 1, 0.79+/-0.19 and 0.71+/-0.21bin Group 2 and 3 respectively. The mean spherical equivalent refraction was -0.24 D 6 months after PARK. Mean astigmatism was reduced from preoperative -0.85+/-0.51 D to postoperative -0.34+/-0.38 D in Group 1, from -2.08+/-0.65 D to -0.43+/-0.64 D and from -4.42+/-0.63 D to -1.23+/-1.25 D in Group 2 and 3 respectively. We also analyzed the angle of error, magnitude of error, index of success, and coefficient of afjustment by vector analysis. No significant complications were observed during the follow-up period. These results show that PARK by excimer laser was effective in correction of astigmatism. The effect of astigmatic correction in Group 2 and 3 were better than that of Group 1. Group 1 showed overcorrected tendency and Group 2 and 3 showed undercorrected tendency.