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.

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.

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.

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.

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.

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.

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.