Keratorefractive surgery practice in a tertiary eye care center in central India / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To study the patient characteristics and keratorefractive surgery(KRS)practice in central India.METHOD: The retrospective study was conducted on 410 patients who underwent KRS from June 2017 to April 2022 at a tertiary eye care center in central India. Demographic data of the patients presenting for the spectacle free vision like age, sex, residence in the form of urban or rural area, refractive error, cause for spectacle-free vision, best-corrected visual acuity, types of procedure, postoperative follow-up and complications were recorded.RESULTS: Among the 410 patients who presented for spectacle-free vision, 324 patients were considered for KRS(79.0%), and 200 patients(61.7%)underwent the laser-assisted in situ keratomileusis(LASIK)procedure, whereas 124 patients(38.3%)underwent the photorefractive keratectomy(PRK)procedure. The final study group comprised 179 female and 145 male. The mean age of the patients was(25±3.5)years. A majority of patients were from urban areas(n=250, 77.2%). The mean preoperative manifest refraction in the right and left eyes was -4.5±2.1 and -4.9±2.0, respectively. The mean surgical time in the LASIK patient was(15±2)min and(17±3)min for both eyes in PRK. None of the patients exhibited epithelial ingrowth, flap healing complications, or infection, and none of them required enhancement. Suboptimal corneal thickness(n=28, 32.6%)was the most common reason for rejection. At the end of the 1-year follow up, 3 patients who underwent the LASIK procedure exhibited regression(-0.5 D±1 D), with a refractive error correction of -6.75 D, -8.5 D, and -7.0 D, respectively.CONCLUSION: LASIK is the predominant procedure for the correction of refractive error in the central Indian population. Although the number of PRK procedures was small, both LASIK and PRK exhibited excellent visual outcome. Myopic regression should be considered when choosing LASIK for high myopia.

Comparison of 10-year Clinical Results between Laser in situ Keratomileusis and Surface Ablation for Moderate to High Myopia

PURPOSE: To compare the long-term prognosis of laser in situ keratomileusis (LASIK) and surface ablation in moderate to high myopia. METHODS: A retrospective study including 87 eyes of 44 myopic patients treated with LASIK or surface ablation from 1995 to 2005 was performed. Follow-up visits were performed at 3 months, 1 year, 5 years, and 8 years. All treated eyes were divided into 2 groups according to preoperative spherical equivalent (SE)- moderate myopia (<-6.0 diopters [D]) and high myopia (≥-6.0 D). The main outcome measures were postoperative uncorrected visual acuity (UCVA), best corrected visual acuity, SE, mean keratometry, safety index, efficacy index, predictability, and complications. RESULTS: Mean SE was -7.05 ± 2.49 D in the LASIK group and -5.25 ± 1.23 D in the surface ablation group. The 10-year SE was -1.78 ± 1.22 D in the LASIK group and -1.35 ± 1.09 D in the surface ablation group, and there was no statistical difference between the 2 groups. At 10 years postoperatively, UCVA was log MAR 0.155 ± 0.161 in the LASIK group and log MAR 0.095 ± 0.140 in the surface ablation group. There were no significant differences in postoperative mean SE, safety index, efficacy index, or complications between the LASIK and surface ablation group at 10 years. CONCLUSIONS: This 10-year follow-up study shows that LASIK and surface ablation for moderate to high myopia have no statistical differences in mean SE, safety index, efficacy index, or complications.

Influences of Cylindrical Correction Amount of PRK on Accuracy of Geometric Corneal Center-Adjusted Ablation Centration

PURPOSE: To evaluate the effect of the amount of cylindrical correction on the accuracy of geometric corneal center-adjusted ablation centration selected by the surgeon in advanced surface ablation-photorefractive keratectomy (ASA-PRK). METHODS: Ninety-five myopic eyes of 62 patients who underwent ASA-PRK were divided into three groups based on the amount of myopic cylindrical correction: Group 1 or =-0.50 D and or =-1.00 D, 28 eyes. The distances and distribution of the ablation centers from the entrance pupil center were analyzed by corneal topography at one month after ASA-PRK. Risk factors for decentration (>0.3 mm) were determined from patient-related factors such as gender, age, laterality, central corneal thickness, and order of procedure and surgery-related factors such as amount of spherical correction, ablation depth, vertical scale bar percentage, and learning effect of surgeon. RESULTS: Mean decentration was 0.26 +/- 0.15 mm (0.04 to 0.83 mm). There was no statistically significant difference in the amount of decentration among the three groups (p = 0.879). Superior-nasal displacement (53.7%) of the ablation center most frequently occurred after ASA-PRK. The amount of decentration among the three groups was not dependent on either patient-related or surgery-related factors. CONCLUSIONS: ASA-PRK using the surgeon-selected ablation center with adjustment toward the geometric corneal center was found to be highly accurate in ablation centration and did not influence the amount of ablation decentration regardless of the amount of myopic cylindrical correction.

Comparative Analysis of the Tear Protein Expression After Photorefractive Keratectomy Using Two-Dimensional Electrophoresis

PURPOSE:To investigate the change in the tear protein composition of patients who underwent refractive surgery. METHODS: Tear samples were collected before photorefrative keratectomy (PRK), on the first, the second, and the third postoperative day, and then a month after the operation from 40 eyes of 20 patients. These tear samples were analyzed using two-dimensional gel electrophoresis (2-DE). Matrix-associated laser desorption/ionization time of flight (MALDI-TOF) was employed for the identification of expressed proteins. Control tear samples were collected from 40 eyes of 20 healthy volunteers who had no history of ocular surgery or pathology. RESULTS: On the first postoperative day, lipocalin-1 precursor, lipocalin-1, and lysozyme were up-regulated. On the second postoperative day, serum albumin precursor and serum albumin were up-regulated. The tears collected on the third postoperative day and after 1 month had similar protein expression levels to the control group. Lipocalin 1 precursor and lysozyme were up-regulated and down-regulated after reftactive surgery, respectively. However, each protein had a different molecular weight and isopotential point. CONCLUSIONS: The tear protein composition changed uniquely in the early postoperative period, and proteins with different isopotential points were detected after PRK. We hypothesized that the healing process might influence the expression of the tear proteins.

Nerve Growth Factor Concentration and Implications in Photorefractive Keratectomy Versus Laser in Situ Keratomileusis

PURPOSE: To determine whether tear nerve growth factor (NGF) concentration correlates with corneal sensation and ocular surface dryness after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). METHODS: A prospective, non-randomized comparative clinical trial. Seventy eyes of 35 patients and 76 eyes of 38 patients underwent PRK and LASIK procedures to correct myopia and myopic astigmatism, respectively. Total tear protein level, tear NGF concentration, corneal sensation, tear film break-up time (BUT) and Schirmer values were measured before and 1 day, 1 week, 1 month, 3 months, and 6 months after the surgery. RESULTS: The postoperative mean tear NGF/total tear protein ratio (NGF/tP) increased in both PRK and LASIK patients compared to their preoperative levels (p<0.0001). At 1 week and 1 month postoperatively, the NGF/tP ratio was higher in PRK than in LASIK subjects (p<0.0001). Up to 6 months postoperatively, the mean corneal sensation after LASIK in the ablated zone was lower than the preoperative sensation (p<0.0001), whereas this was not the case in PRK subjects. Mean BUT and Schirmer values were significantly lower in LASIK-treated eyes compared to PRK-treated eyes up to 6 months postoperatively (p<0.0001). The early postoperative tear NGF/tP ratio correlated with the postoperative 6 month corneal sensation, BUT and Schirmer values. CONCLUSIONS: The difference in postoperative corneal sensation and ocular surface dryness between PRK- and LASIK-treated eyes was related to the difference in the early postoperative levels of NGF/tP, which implies NGF might influence corneal nerve regeneration after these two surgeries.

The Effect of PRK and LASIK for the Correction of Postkeratoplasty Astigmatism

PURPOSE: To evaluate the effect of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) procedure on eyes with high astigmatism after penetrating keratoplasty. METHODS: Thirteen eyes of 12 patients who had PRK (6 eyes) or LASIK (7 eyes) after penetrating keratoplasty were retrospectively reviewed. All patients had a stable postkeratoplasty astigmatism over 4.0D for a minimum of 6 months after all sutures were removed. We followed up patients in early phase (1~3 months) and late phase (6~12 months). RESULTS: Mean preoperative astigmatism in PRK patients was 7.96 +/- 2.63D and in LASIK patients 8.27 +/- 2.96D. Astigmatic magnitude decreased 54% in early phase, and 34% in late phase in PRK group. It decreased 58% in early phase, and 55% in late phase in LASIK group. The reduction of astigmatism and postoperative regression were not stastically significant between two groups. Postoperative uncorrected visual acuity improved 67% in PRK group and 86% in LASIK group above 2 Snellen chart lines. Postoperative corneal haze developed in 3 eyes of PRK group. CONCLUSIONS: PRK and LASIK resulted in improved uncorrected visual acuity and refraction in postkeratoplsty eyes with high astigmatism. But both procedures showed cylinderical undercorrection and postoperative regression in refraction. Mild corneal haze was common after PRK procedure.

Comparison of Pain between Ethanol-assisted Mechanical and Conventional Debridement of Corneal Epithelium in PRK

PURPOSE: To evaluate the effect on postoperative pain of the application of 20% ethanol before debridement of the corneal epithelium METHODS: During photorefractive keratectomy (PRK), performed on 44 eyes of 22 patients with mild to moderate myopia, 20% ethanol was applied on the eyes for 30 seconds just before debridement of the corneal epithelium. Meanwhile, conventional debridement of the epithelium was done on the fellow eyes. Patients were asked to evaluate their subjective postoperative pain after 3 hours, 1 day and 3 days. We measured epithelial healing time by the time of bandage contact lens removal. We also measured visual acuity and manifested refraction at 1 month after surgery. RESULTS: Significantly less postoperative pain was reported at 3 hours and 1 day after surgery in the eyes with ethanol applied. However, postoperative pain did not differ between the two groups at 3 days after surgery, nor did uncorrected visual acuity, manifested refraction at 1 month after surgery, or epithelial healing time. CONCLUSIONS: Application of 20% ethanol as pre-treatment in debridement of the corneal epithelium is beneficial in reducing postoperative pain in PRK.

Comparison of Wavefront Guided Customized Ablation vs. Conventional Ablation

PURPOSE: To compare the visual outcome and satisfaction rate after the wavefront guided ablation with the conventional ablation in laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) patients. METHODS: We performed a prospective study that included 182 eyes of 91 patients who were treated with LASIK (60 eyes) or PRK (122 eyes) using MEL 70 excimer laser system (Carl-Zeiss Meditec, Germany). We applied wavefront guided ablation on the right eye of each patient. The conventional ablation (control group) was performed on the left eye of the same patient. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), spherical equivalent refraction, high order aberrations and contrast sensitivity were evaluated preoperatively and after surgery. Satisfaction rate was evaluated after surgery. RESULTS: We found statistically insignificant improvement of BCVA in wavefront guided ablation group. There were no statistically significant differences in contrast sensitivity between wavefront guided ablation and conventional ablation. In LASIK group, we found statistically significant differences of high order aberrations; RMS HO (High order)(p<0.05) and in PRK group; Z (3, -1), Z (3, 3), Z (4, 0), Z (4, 2), RMS HO (p<0.05). There were no statistically significant differences between wavefront guided ablation and conventional ablation in patient's satisfaction. CONCLUSIONS: High order aberrations of wavefront guided ablation were less increased than of conventional ablation. These results indicate the potential role of the wavefront guided ablation in the field of refractive surgery.

Nitric Oxide-Mediated Neurotoxicity after Excimer Laser Photorefractive Keratectomy

The aim of this study was to evaluate neurotoxicity of Nitric oxide(NO) on cornea after excimer laser photorefractive keratectomy(PRK). PRK was performed on rabbit eyes. According to the time table, tear samples were collected with microcapillary tubes and corneal sensitivity was measured with a Cochet-Bonnet esthesiometer. No generation in the tear fluid was analyzed. To demonstrate NO Synthase(NOS), immunohistochemical localization was performed on frozen sections from rat eyeball tissue. Western blot analysis was used for detection of peroxynitrite, powerful oxidant of NO. NO generation was increased and reached to a maximum value(0.69+/-0.22micrometer/microgram) after 96 hours of PRK, as compared with in normal subjects(Mean: 0.30+/-0.08micrometer/microgram) and was not increased in the treated group with topical application of Ng-nitro-L-arginine methyl ester(L-NAME), a competitive inhibitor of constitutive NOS(cNOS) and inducible NOS(iNOS). Corneal sensitivity decreased below pretreatment levers after three postoperative days, but it was not observed in the L-NAME applied group. We have confirmed that a very strong iNOS and BNOS immunoreactivity was present in corneal keratocytes. Western blot analysis identifed the bands of nitrotyro-sine-proteins suggesting in vivo peroxynitrite toxicity. Our results suggested that NO generated from the enzyme after PRK decreased corneal sensitivity by damaging corneal sensory nerve through the NO and iths oxidant peroxitrite. Therefore topical application of a NOS inhibitor may be effective in maintaining corneal sensitivity.

The Use of Ascorbic Acid after Excimer Laser Photo refractive Keratectomy in Rabbits

Polymorphonuclear leukocytes(PMNs) infiltrate to the wound site within a few hours after excimer laser photorefractive keratectomy(PRK). Oxygen free radicals produced by the PMNs may be injurious to the surrounding corneal tissues and also acts as an inflammatory mediator that deepen tissue damage. In this study we examined that the application of ascorbic acid would decrease corneal haze following excimer laser PRK. Excimer laser PRK was done in 9 rabbits (18 eyes). Ascorbic acid was injected subconjunctivally in one eye and BSS was injected in the opposite eye. The corneal epithelium re-surfaced by 2.6 +/- 0.5 days in the ascorbic acid treated group and by 2.7 +/- 0.7 days in the ESS injected group. Corneal hazes examined in postop 2wk, 4 wk, 6 wk, and 8 wk were 1.6 +/- 0.5, 1.4 +/- 0.5, 0.7 +/- 0.3, 0.5 +/- 0.2 in the ascorbic acid treated group and 2.1 +/- 0.6, 1.7 +/- 0.5, 1.1 +/- 0.3, 0.9 +/- 0.2 in the BSS injected group, respectively. These data suggest that ascorbic acid would decrease corneal haze after excimer laser PRK without significant complications.