Long-term outcomes of photorefractive keratectomy and laser-assisted subepithelial keratectomy in children

PURPOSE: To assess the long-term refractive, visual acuity, binocular vision, and quality-of-life outcomes of photorefractive keratectomy (PRK) and laser-assisted subepithelial keratectomy (LASEK) in children. SETTING: Non-hospital surgical facility with follow-up in a hospital clinical setting. METHODS: In this retrospective review, 56 eyes of 39 patients had PRK or LASEK under general anesthesia. Patients were examined preoperatively and postoperatively at 2 and 6 months and 1 year and then annually for a minimum of 3.5 years. Recorded variables included demographics, refractive error, best corrected visual acuity (BCVA), stereopsis, corneal haze, and quality of life. RESULTS: The mean age at surgery was 6.5 years (range 1.0 to 17.4 years). At the final postoperative examination (mean 5.15 years), the mean spherical equivalent was -1.73 diopters (D) in all patients, -3.20 D in PRK patients, and -1.37 D in LASEK patients. Refraction and corneal clarity were stable over the long term in all eyes. In 28 eyes that were measurable preoperatively, visual acuity improved by a mean of 1.6 lines (range 0 to 7 lines). Seven patients (18%) had measurable stereopsis before surgery and 19 (49%), after PRK or LASEK. No patient had reduced BCVA or loss of binocular fusion postoperatively. On a quality-of-life questionnaire, no family recorded negative opinions of the procedure or negative social or functional outcomes postoperatively. CONCLUSION: Photorefractive keratectomy and LASEK were effective and stable surgical alternative treatments in children with refractive errors who were unable to tolerate or who failed conventional methods of treatment.     

Early bacterial keratitis after laser-assisted subepithelial keratectomy

We report a case of bacterial keratitis that occurred after laser-assisted subepithelial keratectomy. The patient presented with a decrease in visual acuity and pain 2 days after the procedure. Culture was positive for Staphylococcus haemolyticus. The infiltrate slowly resolved with topical antibiotics, and the best corrected visual acuity improved to 20/20. Although bacterial keratitis occurs rarely after refractive surgery, patients should be informed of the potential risk for visual loss caused by this infection.     

Topical anesthesia-induced keratopathy after laser-assisted subepithelial keratectomy

A 42-year-old woman had uneventful bilateral laser-assisted subepithelial keratectomy (LASEK) to correct myopia. She experienced intense pain in the first postoperative week and obtained topical oxybuprocaine for pain relief. Subsequently, she developed bilateral persistent corneal epithelial defects, epithelial edema, and bullae that failed to heal with bandage contact lens and topical lubricants. Over the next 4 months, there was progressive corneal stromal thinning and descemetocele formation in 1 eye, requiring application of cyanoacrylate glue, and stromal edema and scarring in the other eye, which resulted in a visual acuity of counting fingers. Investigations did not reveal associated infection or an underlying immunological disorder; however, the patient admitted to excessive use of topical anesthetic eyedrops in the post-LASEK period. She subsequently had penetrating keratoplasty and lens extraction with IOL implantation in the right eye. The left eye healed with central corneal scarring. This case illustrates that serious sight-threatening complications may occur after LASEK due to abuse of topical anesthetic agents.     

Mycobacterium chelonae keratitis after laser-assisted subepithelial keratectomy

A 24-year-old man with myopic astigmatism had uncomplicated laser-assisted subepithelial keratectomy (LASEK) in October 2004. Approximately 4 weeks later, a foreign-body sensation and redness developed in the left eye. A paracentral anterior stromal infiltrate was observed, and Gram stain on the day of presentation showed branching filamentous gram-positive rods. Cultures subsequently grew Mycobacterium chelonae. Topical tobramycin 15 mg/mL, azithromycin 2 mg/mL, amikacin 25 mg/mL, and cefazolin 50 mg/mL were initiated based on Gram stain results. We believe this is the first documented case of M chelonae keratitis after LASEK.     

Treatment of dense subepithelial corneal haze after laser-assisted subepithelial keratectomy

We report a case of dense and visually significant corneal haze after laser-assisted subepithelial keratectomy (LASEK). Visually significant corneal haze after LASEK can be successfully treated with manual debridement and intraoperative mitomycin-C.     

Recovery of corneal sensitivity after laser-assisted subepithelial keratectomy

PURPOSE: To evaluate the recovery of corneal sensitivity after laser-assisted subepithelial keratectomy (LASEK) for myopia. SETTING: Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China. METHODS: In this prospective interventional case series, central corneal sensitivity (CCS) was measured using a Cochet-Bonnet esthesiometer (Luneau Ophthalmologie) in 85 eyes of 50 patients before and 2 weeks, 1 month, 3 months, and 6 months after LASEK for the treatment of myopia. For analysis, the eyes were divided into 2 groups-the low-moderate myopia group (spherical equivalent [SE] -1.0 to -6.0 diopters [D]) and the high myopia group (SE -6.0 to -16.0 D)-and the correlation between ablation depth and CCS was evaluated. RESULTS: In both groups, a significant decrease in CCS was present at 2 weeks and 1 month. In the low-moderate myopia group, the CCS recovered to preoperative values at 3 months. In the high myopia group, recovery of CCS was slower and preoperative values were reached only at the 6-month follow-up. Measured CCS was significantly correlated with the ablation depth used at the 3-month and 6-month examinations (r = -0.262 and r = -0.264, respectively; P<.05). CONCLUSION: Recovery of corneal sensitivity began 1 month after LASEK and was completed by 3 months in eyes treated for low-moderate myopia and at 6 months in eyes with high myopia. The depth of ablation during surgery affected the recovery of corneal sensitivity.     

微型角膜刀法与乙醇浸润法准分子激光角膜上皮瓣下磨镶术对角膜基质细胞影响的实验研究

目的探讨微型角膜刀法准分子激光角膜上皮瓣下磨镶术（Epi-LASIK）与乙醇浸润法准分子激光角膜上皮瓣下磨镶术（LASEK）对角膜基质细胞的影响研究。方法50只新西兰大白兔随机编号,其中48只（96只眼）随机一只眼行Epi-LASIK,另一只眼行LASEK,余2只（4只眼）未进行手术,作为对照组。采用核苷酸末端转移酶介导的dUTP缺口标记（TUNEL）法观察角膜基质细胞的凋亡情况、Ki-67和d平滑肌肌动蛋白（α-SMA）的免疫组化和免疫印迹法测定角膜组织d-SMA蛋白来观察角膜基质细胞的增殖与向肌成纤维母细胞转化情况,进行计数与半定量分析,对haze形成影响进行分析。结果Epi-LASIK与LASEK术后角膜基质中均有较多的TUNEL阳性细胞出现,在术后24h达最高峰,LASEK术后1周内细胞凋亡情况较Epi-LASIK明显（t=3．63、7．80、4．34、2．95,均P〈0．01）。术后1周基质Ki-67阳性细胞表达增高,72h时达高峰,两组在1周内差异有统计学意义（t=3．81、5．85、5．09、5．59,均P〈0．01）。α-SMA阳性细胞在术后1周明显出现,3个月时仍有较高表达,在术后1个月时阳性细胞数达高峰,α-SMA蛋白表达量的情况与α-SMA阳性细胞数变化一致,均提示LASEK术后增高的情况较Epi-LASIK差异有统计学意义（t=2．97、7．19、6．73,均P〈0．01）。结论Epi-LASIK较LASEK有着更少的角膜基质细胞凋亡、更弱的增殖以及向肌成纤维母细胞的转化,提示Epi-LASIK较LASEK有着更轻的haze反应几率。     

Corneal keratocyte deficits after photorefractive keratectomy and laser in situ keratomileusis

PURPOSE: To measure changes in keratocyte density up to five years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). DESIGN: Prospective, nonrandomized clinical trial. METHODS: Eighteen eyes of 12 patients received PRK to correct a mean refractive error of -3.73 +/- 1.30 diopters, and 17 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 diopters. Corneas were examined by using confocal microscopy before and six months, one year, two years, three years, and five years after the procedures. Keratocyte densities were determined in five stromal layers in PRK patients and in six stromal layers in LASIK patients. Differences between preoperative and postoperative cell densities were compared by using paired t tests with Bonferroni correction for five comparisons. RESULTS: After PRK, keratocyte density in the anterior stroma decreased by 40%, 42%, 45%, and 47% at six months, two years, three years, and five years, respectively (P < .001). At five years, keratocyte density decreased by 20% to 24% in the posterior stroma (P < .05). After LASIK, keratocyte density in the stromal flap decreased by 22% at six months (P < .02) and 37% at five years (P < .001). Keratocyte density in the anterior retroablation zone decreased by 18% (P < .001) at one year and 42% (P < .001) at five years. At five years, keratocyte density decreased by 19% to 22% (P < .05) in the posterior stroma. CONCLUSIONS: Keratocyte density decreases for at least five years in the anterior stroma after PRK and in the stromal flap and the retroablation zone after LASIK.     

PRK术后角膜上皮下雾状混浊的相关因素分析

为探讨准分子激光角膜切削术（ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｋｅｒａｔｅｃｔｏｍｙ，ＰＲＫ）后角膜上皮下雾状混浊（ｈａｚｅ）的原因及影响因素，对ＰＲＫ后６个月时屈光度在－１．００～－１８．５０Ｄ的３１６例（６１５只眼）近视眼的ｈａｚｅ相关因素进行观察和比较。结果：ＰＲＫ后６个月时ｈａｚｅ发生率为４４．７％，１级或以上ｈａｚｅ为１３．３％。ｈａｚｅ的发生率及密度随屈光度增高而增加（Ｐ＜０．０００１），也随切削深度的增加而增加（Ｐ＜０．０００１），术前非接触眼压超过１８ｍｍＨｇ者，ｈａｚｅ的发生率和密度增加（Ｐ＜０．００５），男性较易发生ｈａｚｅ（Ｐ＝０．０００１），与年龄呈负相关（Ｐ＜０．０５）。而角膜厚度、术前戴用接触镜及散光对ｈａｚｅ的影响不显著。结论：高度近视（＞－６．０Ｄ）和过深的切削（＞８０μｍ）是引起ｈａｚｅ的主要原因。术前眼压偏高、年龄偏低对ｈａｚｅ也有明显影响。对ＰＲＫ治疗高度近视应持审     

Apical nodular subepithelial corneal scar after retreatment in hyperopic photorefractive keratectomy

PURPOSE: To report a complication, apical nodular subepithelial corneal scar, that can occur after hyperopic photorefractive keratectomy (PRK) retreatment. SETTING: Istanbul University Eye Research Center, Istanbul, Turkey. METHODS: Twelve eyes of 6 patients with apical nodular subepithelial corneal scar were retrospectively studied. Mean age of the 5 men and 1 woman was 30.2 years +/- 5.4 (SD). All eyes had hyperopic PRK retreatment for regression 9.5 +/- 1.44 months after primary hyperopic PRK. Mean spherical equivalent refraction of the residual hyperopia before retreatment was +4.67 +/- 0.81 diopters (D). All patients had a corneal haze grade of less than 1+. Hyperopic PRK retreatment was performed with a 193 nm excimer laser (Chiron Technolas Keracor 116). RESULTS: Apical nodular subepithelial corneal scars developed within the first month of hyperopic PRK retreatment and progressed until the third month in 12 eyes of 6 patients. The lesion was round and symmetrical in both eyes, smaller than 2.0 mm, and centrally located. During the mean 40.66 +/- 2.46 month follow-up, the lesion did not change in size or density. Mean spherical equivalent refraction after retreatment was 2.88 +/- 0.88 D (range +1.50 to +4.00 D) at 1 month and +4.36 +/- 1.83 D at last follow-up. Refraction was unmeasurable in 3 eyes. Five eyes lost 1 line of best spectacle-corrected visual acuity and 7 eyes, 2 or more lines. The surface regularity indexes were higher than 2.00 in all the eyes. CONCLUSION: Hyperopic PRK retreatment may cause the sight-threatening complication of apical nodular subepithelial corneal scar. This complication behaves unlike corneal haze and does not resolve spontaneously over time.     

Effects of topical vitamin E on keratocyte apoptosis after traditional photorefractive keratectomy

PURPOSE: To evaluate the keratocyte apoptosis and effects of topical vitamin E on keratocyte apoptosis after photorefractive surgery. METHODS: Rabbits were divided into 7 groups, and all groups were compared with controls after epithelial scraping, epithelial scrape and photorefractive keratectomy (PRK) (traditional PRK), transepithelial PRK, production of a corneal flap with microkeratome and laser-assisted in situ keratomileusis (LASIK). The effects of topical Vitamin E treatment were investigated in the traditional PRK group. The terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick-end labelling assay (to detect DNA fragmentation in situ) and light microscopy have been used to detect apoptosis in rabbit cornea. RESULTS: Transepithelial PRK induced minimal keratocyte apoptosis, less than in all other refractive surgical procedures. The greatest amount of keratocyte apoptosis was observed after traditional PRK (p = 0.001), therefore we tested the effects of topical vitamin E in this group. The number of apoptotic keratocytes significantly reduced after vitamin E therapy (p < 0.005). CONCLUSION: Keratocytes undergo apoptosis after refractive surgery in response to mechanical epithelial removal, preparing of corneal flap and excimer laser stromal photoablation. The topical application of vitamin E immediately after surgery can prevent keratocyte apoptosis, and this result suggests that free radicals may be partly responsible for keratocyte apoptosis after excimer laser keratectomy.     

Comparison of stromal remodeling and keratocyte response after corneal incision and photorefractive keratectomy

PURPOSE: We investigated the keratocyte response and stromal remodeling after corneal incision and photorefractive keratectomy to understand the histophysiological and immunohistochemical differences between these two types of surgery. METHODS: Corneal incision or photorefractive keratectomy was performed in rabbits or rats. Then we chronologically observed the histological changes and the changes in the localization of extracellular matrix proteins. RESULTS: In both types of surgery, the keratocyte population at the damaged stroma became sparse, and the cells began undergoing apoptosis immediately after the surgical procedure. Subsequently, activated keratocytes migrated into the acellular zone, and the cells formed multiple layers at the resurfaced subepithelial regions. We observed deposition of amorphous substances between keratocytes that had migrated, and stromal remodeling appeared to start. Three months after surgery, the corneal structure had recovered to a near-normal condition at the corneal incision. After photorefractive keratectomy, however, extracellular matrix proteins were strongly immunoreactive at the subepithelial regions. CONCLUSIONS: These results suggest that the stromal wound-healing processes are similar after corneal incision and photorefractive keratectomy. A corneal incision may induce a transient keratocyte response during stromal remodeling, but photorefractive keratectomy may induce a sustained keratocyte response.     

准分子激光原位角膜磨镶术与准分子激光角膜上皮瓣下磨镶术后角膜知觉恢复的研究

目的 比较准分子激光原位角膜磨镶术（LASIK）和准分子激光角膜上皮瓣下磨镶术（LASEK）后角膜知觉的恢复情况。方法 本研究观察在我院行LASIK或LASEK近视矫正的患者59例（59只眼）,包括低、中度近视行LASEK者20只眼,高度近视行LASEK者30只眼,以及低、中度近视行LASIK者9只眼。分别在术前、术后2周、1、3、6个月时测量角膜中央知觉,并和切削深度进行相关性检验。结果 LASIK和LASEK术后角膜知觉均下降,但LASIK术后下降更明显。在各观察时间点,LASEK术后的角膜知觉均好于LASIK术后2周、1个月和3个月时差异均有统计学意义（P〈0．01）,6个月时P=0．031。低、中度近视LASIK术后6个月时角膜知觉仍未恢复（P=0．023）;而LASEK术后3个月时角膜知觉已恢复（P〉0．05）。高度近视LASEK术后6个月时角膜知觉基本恢复（P〉0．05）。LASEK术后1、3及6个月的角膜知觉和切削深度有相关性（r=0．419,0．433,0．413;P〈0．05）,其余观察时间点两者无相关性。LASIK术后各时间点的角膜知觉和切削深度无相关性（P〉0．05）。结论 LASEK术后角膜知觉的恢复较LASIK术后快,LASEK术后角膜知觉的恢复和切削深度有关。