Observation and study on uncorrected distance visual acuity and ocular adjustment function before and after excimer laser photorefractive keratectomy / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To analyze the changes of uncorrected distance visual acuity(UCDVA)and ocular accommodation before and after excimer laser photorefractive keratectomy(PRK).METHODS: A retrospective study. There were 120 patients(240 eyes)who underwent PRK surgery in our center from December 2017 to December 2019 divided into two groups according to the diopter of spherical equivalent(SE): 70 cases with SE≤-6.00D in the mild to moderate myopia group and 50 cases with -6.00D<SE≤-9.00D in the high myopia group which were observed and analyzed. The UCDVA(LogMAR), monocular accommodative amplitude(AMP), negative relative accommodation(NRA), positive relative accommodation(PRA)and monocular accommodative flipper(AF)were measured before and after operation at 1wk, 1 and 3mo. RESULTS: In the group of low-moderate myopia and high-myopia group, the UCDVA at 1wk, 1 and 3 mo after operation was significantly increased compared with those before operation(all P<0.01). The increase of UCDVA of low to moderate myopia group was better than that in the high myopia group at 3mo after operation(P<0.05). Monocular AMP in the both groups firstly decreased and increased afterwards, and there was a significant decrease than that before operation at 1wk and 1mo after operation(P<0.01). AMP reached and was better than that before operation at 3mo after operation(P<0.01). The increase of low to moderate myopia group was both higher and faster than that of high myopia group. Compared with PRA before operation, the patients of low to moderate myopia group decreased at 1wk after operation(P<0.01), postoperative levels at 1mo recovered to preoperative level(P>0.05)and postoperative at 3mo was superior to preoperative operation(P<0.05); High myopia group did not change significantly at 1wk and 1mo after operation compared with preoperative operation(P>0.05), and increased at 3mo after operation compared with preoperative level(P<0.01). For low to moderate myopia group, there was no significant difference in preoperative and postoperative NRA, and at 1wk after operation, NRA of high myopia group temporarily increased compared with preoperative operation(P<0.01). At 1mo after operation, it returned to the preoperative level(P>0.05), and significantly increased at 3mo after operation compared with preoperative operation(P<0.01). Monocular AF for both groups significantly decreased at 1wk after operation compared with preoperative operation, recovered at 1mo after operation and was significantly better at 3mo after operation(all P<0.01); The low-to-moderate group increased more than the high-myopia group.CONCLUSION: PRK has a good correction effect for myopia below -9.00D, and people in low to moderate myopia have a better postoperative UCDVA correction effect than those in high myopia. The eye accommodation will be abnormal in a short period after operation. The recovery and improvement time of accommodative function in low-moderate myopia group are shorter than that in high myopia group, but both groups can recover and improve at 3mo after operation compared with the preoperative levels.

Contrast to wavefront optimized and wavefront guided excimer laser photorefractive keratectomy / 中华实验眼科杂志

Conventional excimer laser keratectomy have been proved to achieve better visual function,but the traditional therapy of corneal spherical cutting line generally flat profile will make the cornea more oblate shape and the contours of the cornea and lcad to spherical aberration.The alteration of non.spherical nature cause the increase of corneal spherical aberration,which further affects the night vision and contrast sensitivity and other visual quality.Wavefront optimization based on total number of adjustments are to retain the previous visual aberrations of eyes and optimize the non-spherical nature of cornea to create a ideal model based on individual adjustments.Ocular wavefront-guided measurement and ablation in exeimer laser keratectomy can achieve better visual outcome.In this paper,wavefront guided and wavefront optimized treatment outcome for the spherical aberration correction are reviewed.

The Effects of a New Eyeball Fixation Device on the Ablation Surface Profile in Photore fractive Kertectomy

The surgical outcome of excimer laser photorefractive keratectomy(PRK) depends on the accuracy of ablation and the smoothness of the surface ablated. The purpose of this study was to investigate the clinical usefulness of a new eyeball fixation device(EK fixation device). First, the PRK was done on the cornea of New Zealand white rabbit (-8 D, 5.5 mm). The surface with the device was smoother compared to that without. Second, The PRK (-4 D, 6 mm)was done on the surface of the contact lens over the cornea of human volunteers. The ablation surface with the device was smoother than that without(0.20+/-0.04 micrometer vs. 0.34 +/-0.14 micrometer, p=0.028). The epithelial healing experiment in New Zealand white rabbit after myopic PRK (-8 D, 5.5 mm)showed more rapid wound healing in the fixation group (66.49+/-0.03 micrometer/hr vs 47.93+/-1.80 micrometer/hr, p=0.0001). In conclusion, the EK fixation device during the PRK procedures creates a smoother ablation surface and enhances corneal epithelial healing, thus may be a useful clinical device.

Effect of Topical 10% Citrate on Corneal Haze after Excimer Laser Photore fractive Keratectomy in Rabbit

It has been known that 10% citrate solution decreases the infiltration of inflammatory cells in severe alkali-burned rabbit eye. The solution was administered topically and its effects on corneal haze and inflammatory cell infiltration were evaluated. Excimer laser photorefractive keratectomy (PRK) was performed on 10 rabbits (20eyes). The solution was administered on the right eye (treated group)and BSS solution on the left eye (control group) of each rabbit immediately before PRK and 6 times after PRK for 24 hours. After 24 hours, 5 rabbits were sacrificed and infiltrating inflammatory cell counting, malondialdehyde (MDA) immunohistochemical staining and quantitative measurement of MDA were done. Corneal haze and other complications were examined at 2, 4 and 8 weeks after PRK with slit-lamp biomicroscope. There was significant decrease of infiltrating inflammatory cells (p=0.047) and cornea haze at 4 weeks after PRK (p=0.015) in treated group. MDA immunohistochemical staining disclosed that tissue damage occurred primarily on the superficial stroma and partially healed epithelium of the ablated cornea. MDA level decreased in 10% citrate treated group compared to control group but the difference was not statistically significant (p=0.21). These data suggest that topical administration of 10% citrate may decrease corneal haze by decreasing infiltration of inflammatory cells after PRK.

Fluorophotometric Detection of Oxygen Free Radicals in the Cornea and Lens after Excimer Laser Photore fractive Keratecto my in Rabbit

This study was performed to detect the oxidative stress in the cornea and lens in vivo by fluorophotometer after excimer laser photorefractive keratectomy(PRK). Twenty New Zealand white rabbits(20 eyes)were divided into two groups, control group(10 eyes)and PRK group(10 eyes). Rabbits of PRK group underwent PRK(8 diopters)and 2', 7'-dichlorofluorescein diacetate(DCFH-DA)was applied on the central cornea 6 hours after PRK in both groups. Fluorophotometric readings of the cornea and lens were measured 15 minutes(F15)and 30 minutes(F30)after DCFH-DA application in both groups. The cornea and lens was observed with slit lamp biomicroscope for 8 weeks. F15 and F30 of the cornea in PRK group(3.83+/-1.22 ng/ml, 5.12+/-1.57 ng/ml)were significantly higher than those in control group(2.61+/-0.59 ng/ml Eq, 3.26+/-0.76 ng/ml Eq)(p=0.01, p=0.005). F15 and F30 of the lens in PRK group(409.7+/-157.2 ng/ml, 594.9+/-242.2 ng/ml Eq)were significantly higher than those in control group(74.1+/-48.3 ng/ml Eq, 310.1+/-249.8 ng/ml Eq)(p=0.0004, p=0.01). No lens opacity developed and F15 and F30 of the cornea did not correlate with corneal haze determined at postoperative 8 weeks. In this study, we demonstrated increased oxygen free radicals in the cornea and lens after PRK by fluorophotometer in vivo and this method can be used as a useful tool to investigate the possible damage induced by oxygen free radicals in the cornea and lens after excimer laser corneal ablation.

Evaluation of excimer laser photorefractive keratectomy for treatment of myopia and myopic astigmatism / 眼科新进展

Objective To evaluate the efficacy and accuracy of photorefractive keratectomy(PRK) for myopia and myopic astigmatism.Methods SVS APEX PLUS excimer laser with a wave length of 193nm(Summit Technology Inc.Waltham,Mass,USA) was applied.Three hundred and sixteen myopic eyes of 168 patients were treated with PRK from Suptember 1996 to October 1997,and 260 eyes(84%) of 150 patients were followed-up for more than three month,including male 68(116 eyes,40.1%) and female 82(144 eyes,59.9%).The preoperative spherical equivalent refractive errors ranged from -1.25D to -10.00D(mean -4.67D± 1.63D),and astigmatism ranged from 0 to -2.00D(mean -0.33D±0.45D). The patients were divided into two groups according to the refraction:group A(from -1.25D to -5.90D) and group B(from -6.00D to -10.00D).The number of eyes in the two groups were 220 and 40,respectively.Results In group A,After 10 days,68.9% had the uncorrected visual acuity(UCVA) equal to or one line better or lower than the preoperative best corrected visual acuity(BCVA).After 1 ,3,6 and 12 months,90%,96%,95% and 94% had the UCVA equal to or one line better or lower than the preoperative BCVA,respectively.In group B,after 10 days,1,3,6 and 12 months,UCVA equal to or one line better or lower than the preoperative BCVA occurred in 35.9%,83.0%,87.0%,86.0% and 84.0% of the patients respectively. Most of the haze showed 0.5～1 grades except 3 eyes with the haze of 2 grade at 3 or 6 months and it changed to l and 0.5 grade respectively at one year.after 10 days and 1,3,6,12 months postoperatively,the corneal haze was noted in 32.9%,84.8%,62.8%,9.0%and 2.8% of the treated eyes respectively.Conclusion We found that the 193nm excimer laser PRK is a predictable,safe,stable,and effective refractive surgery for correcting myopia up to-10.00D in Chinese patients,and the effect is better in myopia lower than -6.00D.

CLINICAL ANALYSIS OF EXCIMER LASER PHOTOREFRACTIVE KERATECTOMY FOR TREATMENT OF MYOPIA AND MYOPIC ASTIGMATISM / 药物分析学报

To evaluate the efficacy and accuracy of photorefractive keratectomy (PRK) for myopia and myopic astigmatism .SVS APEX excimer laser with a wave length of 193 nm(Sumit Technology Inc. Waltham, Mass, USA) was applied. 316 myopic eyes of 168 patients were treated with PRK between September, 1996 and October, 1997, and 260 eyes (84%) of 150 patients were followed for more than three months, including male 68(116 eyes, 40.1%) and female 82(144 eyes, 59.9%). The preoperative spherical equivalent refractive errors ranged from -1.25D to -10.00 (mean -4.67±1.63D), and astigmatism ranged from 0 to -2.00D (means -0.33±0.45D). We divided the patients into two groups according to the referaction: group A (from -1.25D to -5.90D) and group B(from -6.00 to -10.00D). The number of eyes in the two groups were 220 and 40 respectively. In group A, on the 10th day, 68.9% has the uncorrected visual acuity (UCVA) equal to or one line better or lower than the preoperative best corrected visual acuity (BCVA). In 1,3,6 and 12 months, 90%, 96%, 95% and 94% had the UCVA equal to or one line better or lower than the preoperative BCVA respectively. In group B, on the 10 th day, in 1,3,6 and 12 months, UCVA equal to or one line better or lower than the preoperative BCVA occurred in 35.9%, 83%, 87%, 86%, and 84% of the cases respectively. Most of the haze showed 0.5～1 grades except 3 eyes with the haze of 2 grade in 3 or 6 months and it changed to 1 and 0.5 grade respectively within one year. In 10 days and 1,3,6,12 months postoperatively, the corneal haze was noted in 32.9%, 84.8%, 62.8%,9.0% and 2.8% of the treated eyes respectively. We found that 193 nm excimer laser PRK was a predictable, safe, stable, and effective refractive surgery for correcting myopia up to -10.00D in Chinese patients, and the effect was better in myopia lower than -6.00D.

Outcome of Excimer Laser Photorefractive Keratectomy Associated with Schirmer Test

To evaluate the clinical results of excimer laser photorefractive keratectomy(PRK)in dry eyes,the surgical outcomes &complications were studied in 68 eyes of 34 patients who had received PRK from June,1996 to December, 1997 at Department of Ophthalmology,Chonnam National University Hospital.The patients were divided into two groups according to the preoperative Schirmer test value(Group A :Schirmer test value 10 mm).In Group A,uncorrected visual acuity(UCVA)of better than 20/40 was 38(90.5%)eyes at 3 months and 39 (92.8%)of 42 eyes at last follow up.In Group B,UCVA of better than 20/40 was 23(88.5%)eyes at 3 months and 25 (96.2%)of 26 eyes at last follow up.Thirty six(85.7%)eyes and 23(88.5%)eyes achieved within +/-1 diopter of spherical equivalent at 3 months and thirty two(76%)eyes and 20(77%) eyes achieved within +/-1 diopter of spherical equivalent at last follow up in Group A &Group B respectively.The mean epithelial healing time was 3.38 +/-0.76 days in Group A and 3.23 +/-0.60 days in Group B. In conclusion,there is no statistically significant differences in postoperative results after excimer laser PRK between the two groups. Postoperatively tear deficiency symptoms such as foreign body sensation or feeling of dryness was more common symptoms in relative tear deficiency patients. Further long term follow up study should be done to identify the any other differences of two groups.

Accuracy of Intraocular Lens Power in Cataract Patients Underwent Excimer Laser PRK

We retrospectively evaluated postoperative refraction of four patients(five eyes)who received intraocular lens implantation after excimer laser photorefractive keratectomy (PRK).The mean age of the patients was 44.8 years and 3 patients were female and 1 patient was male.The mean interval between PRK and cataract operation was 20.2 months (1 to 45 months)and the mean follow-up time after cataract operation was 16.2 months(2~43months).Phacoemulsification and PMMA-PCL(6.0~6.5 mm)implantation were made in all cases.SRK-II formula,the most popular empirical formula was used in first 3 cases(group I),but Idem-lens formula,a primitive theoretical formula was used in another 2 cases (group II)after occurrence postoperative refraction errors in group I .In group I and II,the mean postoperative refraction error was +3.00 diopters and +0.50 diopters and uncorrected visual acuity at postoperative 2 months was 20/60 and 20/24 respectively.The mean of calculated IOL-power was -3.75 diopter in group I and -0.625 diopter in group II.From these results,the empirical formula is definitely unsuitable for the calculation of IOL power in the cataract operation following excimer laser PRK. Moreover,although a primitive one,Idem-lens theory could be temporally useful for the IOL-power calculation in such cases.In conclusion,new formula is required for the cataract operation following excimer laser PRK.

A Case of Stevens-Johnson Syndrome after Acetazolamide Use

Erythema multiforme is an episodic, self-limited, mucocutaneous, inflammatory disorder and the disease manifests as severe form is called Stevens-Johnson syndrome. It is most commonly precipitated by herpes simplex infection or drugs and the pathogenesis of the mucocutaneous lesion is thought to be related to immune complexes, cell-mediated immunity, or both. We experienced a case of Stevens-Johnson syndrome in 23-year-old female who had systemic bullous kin lesion and diffue mucopurulent conjunctivitis after use of oral acetazolamide for control of steroid-induced increased intraocular pressure after excimer laser photorefractive keratectomy, which has not been reported in Korea. So, we report this case with a review of the literature.

Two Successful Cases of PJ Rigid Gas Permealble Contact Lens after Myopic Excimer Laser Photorefractive Keratectomy

To improve visual acuity of patients with myopic regression and corneal haze after myopic excimer laser photorefractive keratectomy(PRK), rigid gas permeable(RGP) lens have been recommended. however, spherical RGP lenses cause problems in some cases. We experienced two patients who had some problems with a spherical RGP lens after PRK, but recovered with PJ lens(Park and Joo type RGP lsens) with two base curves of optical zone depending on native patient's keratometric readings. We examined weekly and a corneal topography monthly. Some problems like superficial punctate erosion and corneal molding by spherical RGP lens were disappeared and central corneas regained their original figures and became to be spherical with the more desirable curvature 3 months after PJ lens fitting. Additionally, there was no complication. With these results, we suggest that PJ lens, newly designed RGP lens, can be a choice of RGP lens to improve a corrected visual acuity without complication in case of the patients performed myopic refractive surgery like PRK.

Overcorrection, Undercorrection and Astigmatic Change after Excimer Laser Photorefractive Keratectomy of Myopia

We have studied the overcorrection, undercorrection, astigmatic change and its incidence on time sequence after the excimer laser photorefractive keratectomy, and its relation with the degree of preoperative myopia, sex, and age. The study has been done with 429 eyes which we could assess for 6 months or more after excimer laser photorefractive keratectomy of myopia from July 1993 to march 1997. Overcorrection of more than -1D was common during the early postoperative periods and then gradually decreased with time. Overcorrection has been seen in 261 eyes(60.84%) after 1 month, but only 33 eyes(13.47%) after 1 year, and 13 eyes(11.02%) after 2 years. Undercorrection has been seen in 2 eyes(0.47%) after 1 month, but 25 eyes(10.20%) after 1 year, and 20 eyes(16.95%) after 2 years. Surgically induced astigmatism increased to 0.54+/-0.84D after 10 days and then decreased 0.19+/-0.75D after 12 months. Also, surgical induced astigmatism developed 1.13+/-1.10D in 247 eyes (57.58%) after 1 month, but decreased 0.89+/-0.45D in 107 eyes(43.67%) after 12 months. The occurrence of overcorrection and undercorrection was related to the severity of preoperative myopia(p0.05). The amount of postoperative astigmatism was related to preoperative astigmatism(p0.05).

Effect of Excimer Laser Photorefractive Keratectomy on Density and Morphology of Corneal Endothelial Cells

We investigated the effect of excimer laser photorefractive keratectomy (PRK) on corneal endothelium in both contact lens wearer and non-wearer. Myopes (-3.0D~-9.5D) who underwent excimer laser PRK at Seoul National University Hospital from March to September 1996 were enrolled in this study. Six patients of 9 eyes had no history of contact lens wearing or discontinued wearing contact lens at least 1 year preoperatively (contact lens non-wearers) and 10 patients of 17 eyes wore their contact lenses until 4 weeks before surgery (contact lens wearers). The cnetral corneal endothelial cell density and morphology were evaluated by specular microscopy before and 1week, 3 and 6 months after surgery. In contact lens non-wearer group, no significant postoperative change was observed. But in contact lens wearer group, significnat increase of density and significant decrease fo pleopmorphism index were noted at postoperative 3 and 6 months, respectively. These results suggest that excimer laser PRK does not affect central corneal endothelium and the discontinuation of wearing contact lens may induce postoperative change of corneal endothelim.

A Study of Central Islands after Excimer Laser phootorefractive Keratectomy

We analyzed computed corneal topography(EH-270,visioptics, Inc., USA) after excimer laser photorefractive keratectomy(PRK, Omnimed, Summit Technology, Inc., USA) to determine the prevalence f central islands, the factors having an influence on their occurrence, and the corneal ablation patterns. PRK was performed with single zone on 314 consecutive myopias(-1.0D~-11.25D) on which topographic analysis was done at least 3 months after surgery. Corneal ablation patterns were classified as uniform, keyhole, semicircular, and central island. Age, sex, amount of attempted correction, preoperative corneal thickness, and ablation zone(5.0mm vs 6.0mm) were studied whether they can affect on the prevalence of central islands. Topographic results showed a uniform ablation patterns in 213 eyes(67.7%), a keyhole ablation in 54 eyes(17.3%),a semicircular ablation in 18 eyes(5.7%), and a central islands in 29 eyes(9.3%). There was no association between prevalence of centralisland and age, sex, amount of attempted correction, or preoperative corneal thickness(P>0.05). Only one of 81 eye(1.0%) with smaller ablation diameter(5.0mm) presented central islands showing the highly statistical significance(P<0.005) while 28 of the 233 eyes(12%) with larger ablation diameter(6.0mm) presented central islands. In conclusion, we think that the ablation diameter is a risk factor in the prevalence of central island, and the further studies for the etiology of central island, which are based on the optical zone should be needed.

Effect of Excimer Laser Photorefractive Keratectomy on the Induction of Astigmatism in Rabbits

Twenty eight rabbit eyes which underwent astigmatic photorefractive keratectomy with excimer laser were analyzed to evaluate the effect of excimer laser photorefractive keratectomy on high astigmatic refractive error. Non-astigmatic eyes were divided into 4 groups according to their operative technique for inducing astigmatism(Group I: 50micrometer ablation with no astigmatism, Group II: 3.00 diopter with the rule astigmatism, Group III: 6.00 diopter with the rule astigmatism, Group IV: 9.00 diopter with the rule astigmatism). During the follow-up period, changes of astigmatism were examed with corneal topography, The results were as follows; 1. Two months after surgery, the mean achieved astigmatisms were 0.23(Group I), 1.78(Group II), 2.63(Group III) 2.65 diopters(Group IV), respectively. 2. Mean astigmatic induction rates of the group II,III and IV were 59.4%, 48.3% and 29.48%, respectively, Astigmatic induction rate of group II, in which the attempted astigmatism was -3.00 diopters, was highest(P<0.05) 3. Highly achieved astigmatism at postoperative 7 days regressed in all groups except group I(P<0.05). The regression was most significantly progressed in group IV, but the regression pattern did not reveal any statistically significant difference between the groups(P<0.05) 4. In SEM study, the rabbit cornea samples showed the different irregularities. Deeper ablation group tissues exhibited a much rougher surface appearance than shallow ablation group tissues. In this study, it was concluded that the achieved astigmatism and induction rate of astigmatism were statistically significant correlation(P<0.05), but the induction rate was smaller compared to the attempted astigmatism, and increased tendency for regression.

Complications after Excimer Laser Photorefractive Keratectomy in High Myopia

To evaluate the results and complications of excimer laser photorefractive keratectomy(PRK) in high myopia, 39-months follow-up study after PRK on 179 eyes with high myopia(more than -0.6 diopter) was performed prospectively. And comparative analysis in complications of excimer laser PRK between high myopia and low and moderate myopia(less than -5.9 diopter) was done. In case of high myopia, overcorrection was developed in 63 eyes(35.39%) and undercorrection was developed in 17 eyes(9.55%) 6 months after PRK. At 10 days, induced astigmatism appeared in 122 eyes(68.16%), but it wasdecreased with the lapse of time. Twenty three eyes(12.99%) lost 2 lines of best-spectacle-corrected visual acuity 1 year after surgery, but part of the eyes regained gradually baseline visual acuity. Clinically significant corneal haze was developed in 80 eyes(44.69%) during follow-up period. Excimer laser PRK in high myopia compared with low and moderate myopia induced significantly high occurrence in overcorrection, undercorrection, refractive astigmatism, loss of best-corrected visual acuity, and corneal haze(P<0.05).

Method of Preventing Central Island after Excimer Laser Photorefractive Keratectomy for Myopia

In order to prevent the development of central island after excimer laser photorefractive keratectomy(PRK), 547 eyes which had undergone PRK were studied to evaluate the incidence, width and height of central island retrospectively. Based on this result, PRK was performed on 63 eyes under conventional protocol(software version 3.20, VISX Twenty/twenty Inc, Santa Clara, CA) and then additional laser ablation with a correction amount of 2.5D and adiameter of 3mm was performed whether the incidence has been decreased and additional complications have occurred. As a result of conventional protocol, central island had occurred in 121 eyes out of 547(22.1%) and the width was 2.94+/-0.22mm and the height was 2.64+/-0.89D. In case of 63 eyes which underwent additional laser ablation, central island occurred in 4 eyes (6.34%) and overcorrection occurred only in 3 eyes(4.76%) at one month after PRK. From the standpoint of the above results, we reached the conclusion that the additional ablation for 2.5D by a 3mm in diameter after PRK under conventional protocol is effective. By using this method, we could reduce the incidence of central island without the aid of the upgraded version that contains the anti-central island program.

Mechanical Method Versus Laser Method for the Corneal Epithelium Ablation in Excimer Laser Photorefractive Keratectomy

Both mechanical ablation and laser ablation have been introduced for removal of the corneal epithelium in excimer laser photorefractive keratectomy(PRK). We analyzed the differences of the clinical outcome between mechanical ablation and laser ablation on 256 consecutive eyes followed up more than 6 months after PRK from August 1991 to June 1993. During the follow up period. pre- and post- operative visual acuity, refractive errors, corneal clarity, epithelial healing time, post-operative pain, and central island were compared between two groups. Anova and X2 test were used for statistical analysis. The uncorrected visual acuity at 6 months after operation was 0.81 in group A and 0.75 in group B(p<.05). The degree of corneal haziness was more severe in group B than group A at 6 months after operation(p<.05). Mean refractive errors and keratometer readings were not statistically signigicant between two groups. Average epithelial healing times after operation were 3.18 days in group A and 2.73 days in group B(p<.001). The incidence ot central island was lower in group B than in group A(p<.001). Post-operative pain was less severe in group B than in group A. This results suggest that mechanical ablation seems to achieved better visual acuity and less complication than laser ablation for removal of the corneal epithelium in PRK.

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(

The Comparison between 5.0mm and 6.0mm Ablation Diameter in Surgical Result of Excimer Laser Photorefractive Keratectomy

We analyzed the results of 5.0mm and 6.0mm ablation diameter in excimer laser photorefractive keratectomy using the same excimer laser (Aesculap-Meditec, MEL 60, Germany) In 5.0mm ablation diameter group, forty one eyes of thirty five patients were operated from March 1994 to February 1995 and in 6.0mm ablation diameter group, thirty eyes of twenty three patients were operated from July 1995 to December 1995. All were followed for at least 6 months and analyzed by retrospective method. Refractive change, naked visual acuity, corneal haze and night vision difficulties were measured at 1, 3, and 6 months postoperatively. In eyes treated with 6.0mm ablation diameter, the initial hyperopic shift was reduced with significant differences at 1 and 3 months (p.05). The subjective symptoms of night vision difficulty were significantly lower in the 6.0mm treatment group at 1 and 3 months (p=0. 0067, p=0.02). In conclusion, treatment with 6.0mm ablation diameter made less initial hyperopic shift and reduction of side effects in comparison with 5.0mm ablation diameter.