Effect of Mitomycin C with Different Application Methods on Rabbit Cornea after Excimer Laser Surgery

PURPOSE: We evaluated the effect of Mitomycin C (MMC) applied by different methods, on corneal healing after excimer laser phototherapeutic keratectomy (PTK) in rabbits. METHODS: PTK was performed on 34 eyes of 17 New Zealand white rabbits. The control group underwent PTK alone, while the experimental groups underwent PTK with intraoperative application of either annular or discoid filter paper soaked with 0.02% MMC for 2 minutes. At postoperative 4, 12, and 24 weeks, the degree of corneal haziness was determined using a slit lamp biomicroscope, and the proliferation of keratocytes was observed histologically. RESULTS: At 4 weeks, the degree of corneal haziness was significantly lower in both MMC-treated groups than in the PTK-alone group (P<0.001). The two MMC-treated groups also showed decreased corneal haziness at 12 and 24 weeks, although the change was not statistically significant. In addition, the MMC-treated groups showed less proliferation of keratocytes at 4 and 12 weeks. At 24 weeks, the group that received annular application of MMC showed a significant decrease of keratocytes compared with the control group(p=0.026), while the group with discoid application showed no significant difference. CONCLUSIONS: In this study, we found that the annular application of MMC after PTK not only shows similar effect on wound healing but also reduces the side effects of MMC by minimizing the application surface.

Clinical results of multizone photorefractive keratectomy for high myopia: Comparative study of two-zone and three-zone technique

In order to reduce a depth and slope of edge of ablation, the technique using 2 or 3 ablaiton zones has been applied to excimer laser photorefracitve keratectomy (PRK) for high myopic patients. In this study, excimer PRK using 2 zones (5.0mm; 100%, 6.0mm; 70%) or 3 zone (5.0mm; 100%, 5.5mm; 70%, 6.0mm; 50%) were used to each 10 patients having a range of refractive power between -8D and -9.5D randomly and divided into group 1 and group 2, respectively. corneal epithelial healing was delayed in group 2 comparaed to group 1 and the diference of that between group 1 and group 2 were statistical significant (P0.05). Uncorrected visual acuities of 20/40 or better were achieved in all patients of both groups at the last postoperrative visit (mean+/-SD, 22+/-3.4 weeks). Spherical equivalent less than 1.0 diopter was achieved in 60% of group 1 and 80% of group 2. As a complication 3 eyes (30%) in group 1 and 1 eye (10%) in group 2 lost 2 lines of best corrected visual acuity and thee was no statistically significant difference in both corneal haziness and patients' complaints between group 1 and group 2. With these results we could find a similar clinical results between excimer PRK using 2 zones and 3 zones by 6 months.

The Necessity of Topical Corticosteroid After Excimer Laser Photorefractive Keratectomy

The effect of topical steroid application on clinical results of 215 eyes(126 patients) performed with excimer laser photorefractive keratectomy (PRK) from July 1993 to July 1994 was evaluated, postopertively. The range of myopia was between -2.5 and -11.5 diopter and followed for 9 months after PRK with Summit Omnimed(TM). Topical corticosteroid or non-steroidal antiinflammatory drug (NSAID) was not applied for one month after operation in all cases. After one month, in cases of 115 eyes showing myopic regression of more than -1 diopter or stromal haziness of more than grade 1(delayed steroid group; DSG), 0.1% fluorometholone was applied 4 times daily for 4 weeks, then tapered according to the planned schedule. 46.5% (100 eyes, non-steroid group;NSG) did not show the myopic regression nor stromal haziness without treatment of fluorometholone throughout the follow-up period. Uncorrected visual acuity, spherical equivalent and corneal haziness were evaluated 1, 2, 4, 8, 12, 24, 36 week after operation. 73%(73 eyes) of NSG and 27%(30 eyes) of DSG showed a myopia less than 6.0 diopters preoperatively. The proportion of male was 36% in NSG and 50.4% in DSG. 88.1% of male high myopia(>6.0 diopters) needed 0.1% fluorometholone, while 17.6% of female moderate and mild myopia(

Evaluation of Multifactorial Factors Contributing to The Myopic Regression after PRK

The thirty four patients(60 eyes) of the same age group, sex and refractive error receiving eximer laser photorefractive keratectomy(PRK) from April 2, 1991 to May 2, 1993 were studied to evaluate the possible factors influencing the myopic regression. In this study, we didn't find any difference between regressed and nonregressed group in the individual parameters such as IOP, keratometer, corneal thickness, occupation, surgeon, hyperopic peak after PRK, and topographic analysis preoperatively and postoperatively. But, the increased tendency of myopic regression one the another eye experiencmg myopic regression on one eye showed statistically significance(P=0.005) and the same tendency was applied on the corneal haziness(P=0.012). We suggest corneal haziness is likely related to causing the myopic regression following PRK. Therefore, the surgeon should particularily try to prevent myopic regression in patients experiencing myopic regression on his one eye by minimizing coneal haziness following PRK.