自然光暴露对PRK法单眼远视离焦幼年恒河猴角膜组织的影响

目的：探讨自然光暴露对单眼远视离焦幼年恒河猴正常和准分子激光角膜切削术(PRK)损伤后角膜组织潜在的光损伤作用。

方法：选取12只2月龄恒河猴,行右眼PRK,矫正度数为-4.0D,制作单眼远视离焦近视动物模型。幼猴体质量和性别均衡配对后分为两组：人工照明组(AL组,n=6)和自然光组(NL组,n=6)。两组幼猴饲养于同一人工照明条件室内饲养环境,NL组幼猴每天9：00～11：00和15：00～17：00于室外随单笼接受自然光照射。PRK术后裂隙灯检查比较两组PRK眼角膜愈合及haze形成情况; PRK术后50d,每组各取4只幼猴双眼泪液,采用蛋白质芯片法检测泪液11种细胞因子含量。PRK术后180d取角膜组织,分别行病理组织学检查组织结构变化; 免疫组织化学法检测TGF-β1和α-SMA表达; TUNEL法检测细胞凋亡以及采用羟胺法和硫代巴比妥酸法分别测定角膜上皮细胞SOD和MDA含量。

结果：PRK术后NL组PRK眼出现一过性haze,术后40d两组haze分级评估有差异(P=0.015)。PRK术后50d,两组PRK眼泪液EGF和TGF-β1含量均有差异(P=0.045、0.038),两组间对侧眼均无差异(P>0.05); 且AL组、NL组组内泪液TGF-β1水平有差异(P=0.003、0.036)。术后180d,两组双眼角膜组织形态学一致; 角膜组织内各层偶见细胞凋亡染色,且无明显TGF-β1和α-SMA表达; 两组PRK眼和对侧眼角膜上皮细胞SOD活力和MDA含量均无差异(P>0.05)。

结论：自然光照射量可加剧幼猴PRK术后角膜组织修复反应,但远期未对角膜组织造成不可逆病理组织学改变,对正常的幼猴角膜组织无明显光损伤作用。     

氧化剂对准分子激光兔角膜切削术后细胞凋亡的影响

目的探讨氧自由基对准分子激光屈光性角膜切削术（PRK）后凋亡机制介导的角膜创伤愈合反应的作用，以及局部应用抗氧化剂维生素C（Vit C）、维生素E（Vit E）对术后角膜的影响。方法将28只兔分成3组，其中4只为正常对照；其余24只实验兔分成2组，每组12只，行双眼-5．0 DPRK。一组术后左眼每日结膜下注射VitC 0．1g，右眼为对照；另一组术后左眼每日结膜下注射VitE 25mg，右眼为对照。于术后1、3、7、14d测定角膜组织超氧化物歧酶（SOD）、丙二醛（MDA）及谷胱甘肽过氧化物酶（GPx）的变化，同时术后定期制作病理切片，检测角膜基质细胞数量，采用脱氧核苷酸末端转移酶介导的缺口末端标记法（TUNEL）检测角膜细胞凋亡，光镜观察凋亡细胞形态，定量统计比较凋亡水平差别。结果（1）PRK术后1、3d角膜SOD、GPx活性小于对照组（P〈0．05），MDA的水平高于对照组（P〈0．05）。局部应用抗氧化剂组其角膜SOD、GPx活性高于单纯激光组（P〈0．05），MDA水平低于单纯激光组（P〈0．05）。（2）角膜基质细胞凋亡在1～14d均与正常对照组有差别（P〈0．01），在应用抗氧化剂组角膜基质细胞凋亡较单纯激光组减少（P〈0．05）。（3）术后角膜基质细胞数增加，应用抗氧化剂组角膜基质细胞增生较单纯激光组减少（P〈0．05）。结论准分子激光屈光性角膜切削术后早期，角膜存在着脂质过氧化形式介导的自由基性的组织损伤破坏，促进角膜细胞的凋亡；局部应用抗氧化剂VitC、VitE能早期减轻PRK术后炎性反应，降低角膜过氧化损伤，阻止术后细胞凋亡，减轻角膜基质反应性过度增生，降低术后屈光回退和haze形成。     

LASEK、PRK和LASIK治疗中低度近视的比较

目的对比分析准分子激光上皮下角膜磨镶术(LASEK)、碰光性角膜切削术(PRK)、激光原位角膜磨镶术(LASIK)治疗中低度近视临床疗效。方法LASEK组58例(112眼)随访3-9月,PRK、LASIK组各120眼随访1a以上,观察分析术后疼痛症状,裸眼视力及角膜混浊情况。结果术后1d出现疼痛症状:LASEK组:81眼(72.3％),PRK组120 眼(100.0％),LASIK组13眼(10.8％);术后3d裸眼视力≥0.8:LASEK组24眼(21.4％),PRK组27眼(22.5％),LASIK组113 眼(94.2％);术后3月存在角膜Haze:LASEK组31眼(27.6％)、PRK组94眼(78.3％),LASIK组0眼。结论LASEK后疼痛症状、角膜Haze明显减轻,疗效优于PRK;LASEK与LASIK相比没有角膜瓣相关并发症,早期视力恢复较慢。     

藏红花提取液对慢性高眼压兔视网膜SOD和MDA的影响

目的:探讨实验性慢性高眼压兔视网膜SOD和MDA含量的变化及藏红花提取液的保护作用。方法:新西兰家兔24只,随机分为正常对照组、高眼压组、治疗I组和治疗II组,每组6只12眼。高眼压组和2个治疗组兔的眼前房内注射3g/L复方卡波姆溶液0.2mL,造成慢性高眼压模型。治疗I,II组兔每日经耳缘静脉推注藏红花提取液,20mg和80mg原药/kg。在7,14d后处死各组半数动物,检测视网膜SOD,MDA含量,并进行组间比较分析。结果:造模7d后高眼压组、治疗I组和II组家兔视网膜组织中的SOD值均明显低于对照组,有显著统计学差异(P<0.05);但治疗I,II组的SOD值均明显高于高眼压组,且治疗II组高于治疗I组(P<0.05)。在14d时,高眼压组与2个治疗组的SOD值均已接近对照组水平,差异无显著性(P>0.05)。造模后7d,高眼压组视网膜组织中的MDA含量明显高于对照组,有显著统计学差异(P<0.01)。治疗I组、II组的MDA含量均低于高眼压组(P<0.01),但仍明显高于对照组(P<0.01)。造模后14d,高眼压组、治疗I组和II组的MDA水平均进一步升高,但与对照组相比仍略高(P<0.01)。结论:藏红花提取液在高眼压早期能有效提高慢性高眼压下视网膜中SOD活性,降低MDA含量。     

低分子肝素下调房水bFGF含量抑制晶状体囊外摘除术后前房炎症

目的:观察房水中碱性成纤维细胞生长因子(basic fi-bro blast growth factor,bFGF)含量的变化,探讨低分子肝素(low molecular weight heparin,LMWH)抑制晶状体摘除术后前房炎症的机制。方法:家兔84只随机分为对照组和实验组,每组42只,行单眼透明晶状体囊外摘除术。实验组手术结束时用浓度为50kU/L的LMWH进行前房灌注。分别于术后1,3,6,15,30,45,60d每组各取6只家兔,裂隙灯显微镜下对角膜水肿、房水混浊及前房纤维蛋白渗出的程度进行观察和分级,然后处死动物,抽取房水用Elisa法测定bFGF的含量。另选6只健康家兔测定前房bFGF含量作为基线值。结果:术后1～6d,实验组角膜水肿、房水混浊及前房纤维蛋白渗出的程度明显轻于对照组(P<0.01),15d后两组比较无差异。术后实验组和对照组房水bFGF含量同时升高,实验组1d达峰值,而对照组6d达峰值;达峰值后两组bFGF含量均缓慢下降。术后1～30d对照组bFGF含量明显高于实验组(P<0.05),45d后两组比较无显著性差异。结论:应用浓度为50kU/L的LMWH前房灌注能显著降低兔眼晶状体囊外摘除术后前房炎症反应,其机制可能与房水中bFGF含量下调有关。     

准分子激光表层切削手术前后裸眼远视力及眼调节功能的变化

目的：观察分析准分子激光屈光性角膜切削术(PRK)手术前后裸眼远视力(UCDVA)及眼调节功能的变化。

方法：选择2017-12/2019-12在我中心行PRK手术病例120例240眼进行回顾性研究,按等效球镜(SE)分为低中度近视组(SE≤-6.00D)70例及高度近视组(-6.00D结果：低中度近视组及高度近视组PRK术后1wk,1、3mo的UCDVA较术前明显提高(均P<0.01)。术后3mo低中度近视组UCDVA的提高幅度优于高度近视组(P<0.05)。单眼的AMP,两组患者术后都呈现先下降后上升的趋势,术后1wk,1mo较术前明显下降(均P<0.01),到术后3mo均达到并优于术前水平(均P<0.01),低中度近视组较高度近视组提高的幅度大、提升的速度快。低中度近视组患者术后1wk PRA较术前下降(P<0.01),术后1mo恢复至术前水平(P>0.05),术后3mo优于术前(P<0.05); 高度近视组术后1wk,1mo与术前相比无明显变化(均P>0.05),至术后3mo也优于术前水平(P<0.01)。低中度近视组术前术后NRA变化均无差异,高度近视组与术前相比术后1wk NRA有短暂的增加(P<0.01),术后1mo恢复至术前水平(P>0.05),术后3mo较术前明显增加(P<0.01)。两组患者术后1wk单眼AF与术前相比均明显下降,术后1mo恢复并优于术前,术后3mo提升的更加明显(均P<0.01); 低中度近视组较高度近视组提升的幅度更大。

结论：PRK对于-9.00D以下的近视的矫正效果好,低中度近视较高度近视组术后UCDVA矫正更佳。术后短期内眼调节功能会出现异常,低中度近视组各调节参数恢复和改善的时间较高度近视组快,但在术后3mo时均可恢复或优于术前水平。     

LASEK与PRK术后兔角膜组织病理学观察

目的通过观察准分子激光上皮下角膜磨镶术(LASEK)与准分子激光角膜切削术(PRK)术后动物角膜组织形态的改变比较角膜创面愈合情况,为探讨LASEK与PRK手术后角膜创面的愈合机制以及术后常见并发症的发生原因及其防治提供实验依据。方法52只新西兰白兔随机分为8组,每只兔右眼行LASEK,左眼行PRK。术后1、7 d及1、3、4、5、6个月观察Haze情况;处死动物取角膜行HE染色,比较术后每一时相点角膜上皮及角膜基质的愈合情况。结果LASEK组与PRK组的术后组织形态学比较发现:LASEK术后角膜上皮细胞的形态改变、增厚程度及恢复正常的时间、胶原纤维排列的紊乱情况均轻于PRK组,存在明显的统计学意义(P<0.05)。结论LASEK上皮瓣在手术后角膜创面的愈合中有重要作用。     

去瓣型Epi-LASIK和PRK对兔角膜病理影响的对比研究

目的 对比研究去瓣型准分子激光上皮下角膜磨镶术(epi-polis laser in-situ keratomileusis,Epi-LASIK)和准分子激光屈光性角膜切削术(photorefractive keratectomy,PRK)时兔角膜病理的影响.方法 新西兰白兔34只,随机取其中32只兔的右眼行去瓣型Epi-LASIK(A组),左眼行PRK(B组),另外2只兔(4只未手术眼)为正常对照组(C组).术后4 h、1 d、3 d、5 d、7 d、14 d、1个月、3个月取角膜标本,HE染色观察角膜前基质细胞的数量变化,免疫细胞化学染色观察角膜中央区Ki-67、α-SMA阳性细胞数量及角膜切削缘区PCNA阳性细胞数量,同时透射电镜观察角膜超微结构的变化.结果 正常角膜前基质细胞数量为每400倍光镜(88.00±5.38)个;术后各时间点B组前基质细胞数量均较A组少,差异均有显著统计学意义(均为P<0.01).正常角膜上皮细胞基底层PCNA阳性细胞数量为每400倍光镜(15.94±3.02)个;术后1 d、3 d、5 d、7 d、14 d A组PC-NA阳性细胞数量均较B组少,差异均有统计学意义(均为P<0.05或0.01).正常角膜基质层几乎不表达Ki-67;术后4 h、1 d、3 d、5 d、7 d、14 d A组Ki-67阳性细胞教均较B组少,差异均有显著统计学意义(均为P<0.01).正常角膜几乎不表达α-SMA;术后5 d、7 d、14 d、1个月、3个月A组α-SMA阳性细胞数均较B组少,差异均有显著统计学意义(均为P<0.01).透射电镜检查显示,术后7 d之内A组细胞之间结合更紧密,3个月时基质内胶原纤维排列较整齐.结论 去瓣型Epi-LASIK比PRK有着更轻的角膜上皮损伤反应,更少的角膜上皮细胞和角膜基质细胞增殖反应以及更低的向肌成纤维母细胞转化潜能,所以角膜上皮下雾状混浊(haze)发生的可能性更低.     

不同撕囊直径下行囊袋内超声乳化对角膜和血-房水屏障的影响

目的：初步探讨不同撕囊直径下行囊袋内超声乳化对角膜和血-房水屏障的影响。

方法：选取2016-05-01/2017-04-31在潍坊眼科医院行飞秒激光辅助超声乳化手术的白内障患者(78例100眼)。术前按照撕囊直径分为试验组36例50眼,术中撕囊直径4.7mm; 对照组42例50眼,术中撕囊直径6.0mm。观察并分析两组患者术中平均超声能量和有效超声时间,术前和术后1d,1wk,2mo的最佳矫正视力、中央角膜厚度、房水闪辉细胞,术后2mo的角膜内皮细胞计数变化。

结果：两组患者术前最佳矫正视力、晶状体核硬度分级、中央角膜厚度、术中平均超声能量及有效超声时间均无统计学差异(P>0.05)。两组术后各时间点的最佳矫正视力比较,差异没有统计学意义(P>0.05)。以各时间点中央角膜厚度与术前中央角膜厚度差值作为各时间点中央角膜厚度变化值,结果显示,术后1d,1wk试验组患者的中央角膜厚度变化小于对照组,差异有统计学意义(P<0.05); 术后2mo中央角膜厚度变化比较,差异无统计学意义(P>0.05)。术后1d,1wk试验组患者的房水闪辉细胞数低于对照组; 至术后2mo,两组间差异无统计学意义(P>0.05)。术后2mo试验组角膜内皮细胞丢失率明显低于对照组,差异有统计学意义(P<0.05)。

结论：小直径撕囊行囊袋内超声乳化能够减少术中超声乳化能量对角膜的损伤,同时减少对血-房水屏障的破坏,患者术后恢复更快。     

兔Epi-LASIK术后早期角膜创伤愈合反应的研究

目的 通过比较Epi-LASlK、PRK两种术式,探讨上皮瓣保留对早期角膜创伤愈合反应的影响.方法建立兔上皮瓣下角膜磨镶术(Epi-LASIK)、PRK模型,检测术后角膜基质炎性细胞数量、角膜基质细胞数量、白细胞介素1(IL-1β)、转化生长因子(TGF-β2)的表达来探讨角膜创伤愈合反应.结果 Epi-LASIK术后1 d、3 d角膜基质炎性细胞数量明显比PRK少,差异有统计学意义(P<0.05);Epi-LASIK术后1 d、3 d角膜基质细胞数量与正常对照比较差异无统计学意义(P>0.05);Epi-LASIK、PRK角膜上皮层TGF-β2、IL-1β表达差异均无统计学意义(P>0.05);Epi-LASIK术后1d、3 d角膜基质TGF-β2、IL-1β表达明显比PRK弱,差异有统计学意义(P<0.05).结论 Epi-LASIK由于上皮瓣的物理屏障作用,减轻了Epi-LASIK术后早期角膜创伤的过度反应,有利于其正常修复.     

The effect of excimer laser keratectomy on corneal glutathione peroxidase activities and aqueous humor selenium levels in rabbits

BACKGROUND: The formation of free oxygen radicals has been demonstrated in the corneal tissue after 193 nm laser irradiation. Cornea has several defense mechanisms that protect against oxidative damage. One of them, glutathione peroxidase (GPx), catalyzes the destruction of hydrogen peroxide and lipid hydroperoxide. Selenium is a trace element which is incorporated into the selenoenzyme GPx. In the present study, the effect of excimer laser keratectomy on corneal GPx activities and aqueous humor selenium concentrations in rabbits was evaluated. METHODS: Animals were divided into five groups, and all groups were compared: controls (group 1), after epithelial scraping (group 2), transepithelial photorefractive keratectomy(PRK; group 3), superficial traditional PRK (50 microm; group 4) and deep traditional PRK (100 microm; group 5). Corneal GPx activities were measured by a modification of the coupled assay procedure. Aqueous humor selenium concentrations were determined using hydride generation atomic absorption spectrometry. RESULTS: Corneal GPx activities were significantly lower only in group 5 ( P<0.05), and the selenium concentration in the aqueous humor did not change in any group. CONCLUSION: Deep corneal photoablation inhibits GPx enzyme activities in the cornea. Therefore, antioxidants may be useful in reducing free radical-mediated complications after excimer laser corneal photoablation.     

准分子激光屈光性角膜切削术后兔角膜基质细胞凋亡及其防治的研究

目的：探讨准分子激光屈光性角膜切削术（photorefractive keratectomy,PRK）后凋亡机制介导的角膜创伤愈合反应对屈光度数回退和角膜雾状混浊（haze）的影响,以及局部应用锌制剂的药物效果。方法：对90只新西兰白兔行双眼PRK,将左眼作为实验眼,手术前、后分别给予A组0．1％地塞米松眼液、B组0．5％硫酸锌眼液和C组0．04％丝裂霉素眼液滴眼;右眼作为对照眼。术后定期裂隙灯下观察haze的程度,测量角膜的厚度,进行光镜和透射电镜观察,采用脱氧三磷酸尿苷缺口末端标记法行凋亡细胞检测,并进行对比性分析。结果：（1）PRK术后角膜前基质细胞出现凋亡,实验眼B组凋亡细胞最少（P＜0．01）。（2）术后角膜厚度增加,前基质细胞增多,实验眼haze和增生程度眼B组凋亡细胞最少（P＜0．01）。（3）术后角膜上皮增生,实验眼B组角膜上皮厚度最小（P＜0．01）。结论：PRK术后屈光度数回退和haze的形成是凋亡机制介导的角膜创伤愈合过程,锌制剂可阻止角膜前基质细胞凋亡,最大限度减轻反应性过度增生,有望成为临床防治haze形成和屈光度数回退的理想药物。     

Pain after epithelial removal by ethanol-assisted mechanical versus transepithelial excimer laser debridement

PURPOSE: To compare subjective pain responses between two techniques of epithelial removal prior to photorefractive keratectomy (PRK) treatment: ethanol-soaked pledget with mechanical debridement of the epithelium versus excimer laser transepithelial ablation. METHODS: Nine patients underwent bilateral PRK. Each had the epithelium in one eye debrided by placing a pledget soaked in 20% ethanol on the cornea for 2 minutes followed by gentle scraping with a blade. The epithelium in the other eye was removed by transepithelial phototherapeutic keratectomy (PTK) treatment. For each eye, PRK was initiated immediately after removal of the epithelium. On postoperative day one, each patient was asked to rate the level of pain suffered over the last 24 hours on a scale of 0 (minimal) to 10 (maximal). Data were analyzed in a masked fashion. RESULTS: Postoperative day one average pain level in the ethanol-assisted mechanically debrided eyes was 3.0 +/- 2.5 and in the transepithelial PTK eyes was 6.8 +/- 1.8. The difference was statistically significant by Student's t-test (P < .01). All epithelial defects healed within 3 days with no clinically significant difference in healing time between the two techniques. CONCLUSION: In preparation for PRK, ethanol-assisted mechanical debridement of the epithelium caused significantly less postoperative pain than epithelial removal using the excimer laser.     

Concomitant effect of topical ubiquinone Q10 and vitamin E to prevent keratocyte apoptosis after excimer laser photoablation in rabbits

PURPOSE: To investigate in vivo whether ubiquinone Q10 together with vitamin E protects rabbit corneas from keratocyte apoptosis after excimer laser irradiation. METHODS: Photorefractive keratectomy (PRK) was performed in both eyes of three New Zealand white rabbits. During 3 days before surgery, each right eye received four-times-daily instillation of an eye-drop solution containing ubiquinone Q10 0.20% and vitamin E 0.04%; each left eye was treated with a solution that did not contain ubiquinone or vitamin E. The central cornea was analyzed after surgery using the in situ end labelling (ISEL) technique of nicked DNA to detect DNA fragmentation. To determine the number of ISEL positive nuclei, an average of 70 random microscopic fields (five for each de-epithelialized tissue section) of 138,000 mu2 were examined in the right and left cornea samples at 250X by two different observers. RESULTS: Light microscopic examination of the sections from corneas treated before PRK showed that cells committed to apoptosis by PRK were about 50% compared to those of untreated controls. CONCLUSION: Treatment of rabbit eyes before PRK with ubiquinone Q10 lowered the number of apoptotic events.     

Corneal forward shift after excimer laser keratorefractive surgery

The excimer laser keratorefractive surgery inevitably compromises structural integrity of the cornea by the surgical tissue subtraction and loss of integrity of Bowman’s membrane. Forward shift of the cornea is commonly seen after both photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Antero-posterior movement of the cornea is evaluated by measuring the posterior corneal elevation with the scanning-slit corneal topography (Orbscan). Eyes with thinner cornea, higher intraocular pressure, and higher myopia requiring greater laser ablation were more predisposed to forward shift of the cornea. After PRK, there was a trend toward progressive forward shift of the cornea, but the progression stabilized 6 months after surgery. Because progressive thinning and expansion of the cornea were not observed during the one-year observation period after PRK, the forward shift of the cornea does not represent true ectasia. Forward shift of both corneal surfaces would add to the tendency toward myopic regression after excimer laser surgery.     

Corneal forward shift after excimer laser keratorefractive surgery

The excimer laser keratorefractive surgery inevitably compromises structural integrity of the cornea by the surgical tissue subtraction and loss of integrity of Bowman's membrane. Forward shift of the cornea is commonly seen after both photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Antero-posterior movement of the cornea is evaluated by measuring the posterior corneal elevation with the scanning-slit corneal topography (Orbscan). Eyes with thinner cornea, higher intraocular pressure, and higher myopia requiring greater laser ablation were more predisposed to forward shift of the cornea. After PRK, there was a trend toward progressive forward shift of the cornea, but the progression stabilized 6 months after surgery. Because progressive thinning and expansion of the cornea were not observed during the one-year observation period after PRK, the forward shift of the cornea does not represent true ectasia. Forward shift of both corneal surfaces would add to the tendency toward myopic regression after excimer laser surgery.     

PRK and LASIK--their potential risk of cataractogenesis: lipid peroxidation changes in the aqueous humor and crystalline lens of rabbits

PURPOSE: There are insufficient data on the possible cataractogenic side effects of excimer laser corneal surgery. Higher malondialdehyde (MDA) levels could indicate oxidative events related to the cataractogenic process. We therefore examined MDA levels after refractive laser surgery. METHODS: Six white Russian rabbits received laser in situ keratomileusis (LASIK) (Schwind keratome) in the right eye and a 250-microm-deep microkeratome cut (Schwind microkeratome) in the left eye. Six others underwent photorefractive keratectomy (PRK) in the right eye; the left eye remained untreated. The 180 mJ/cm2 fluence applied at a rate of 10 Hz with an optical zone diameter of 5 mm in all rabbits (438 pulses) resulted in an estimated central photoablation depth of 116 microm. Two weeks later, lenses and aqueous were taken immediately after death. MDA was detected in aqueous and homogenate of lenses after reacting with thiobarbituric acid (TBA). MDA bound to TBA (MDA-TBA) was specifically analyzed by high-performance liquid chromatography (HPLC) (excitation, 525 nm; emission, 551 nm) using phosphate-buffered methanol as eluent. RESULTS: No significant laser-induced MDA alteration was found in either the aqueous or the lens. The microkeratome group, however, had two to three times higher MDA levels in the lenses than the control group (p = 0.12) or the PRK (p = 0.03) group. CONCLUSION: Elevation of MDA in the lens of the microkeratome group indicates that LASIK, but not PRK, may be a risk factor in cataractogenesis. The increased MDA levels in the LASIK group are probably caused by the microkeratome incision rather than the secondary radiation of the excimer laser. Postoperative inflammation may explain the surprising results.     

A confocal microscopic and histological study on rabbit corneas after photorefractive keratectomy for hyperopia

PURPOSE: To evaluate changes in corneas after PRK (photorefractive keratectomy) for hyperopia. MATERIALS AND METHODS: Six rabbits were given PRK treatments for + 6.0 D of hyperopia. We observed these corneas by confocal microscopy at 3 days, 1 week, 2 weeks, 1 month, and 3 months after PRK, and examined them histologically. RESULTS: In the ablated area, proliferative changes in the subepithelial layer had already appeared three days after the operation. These changes progressed for one month, but had decreased at three months after operation. In confocal microscopy, the proliferative change in the subepithelial layer was observed as bright, highly refractive tissue interspersed with small spaces void of cells, and was especially evident at the wound edges of the peripheral side. The center of the cornea was slightly damaged by the excimer laser but proliferative changes were not observed there. CONCLUSION: The results of this study revealed that the damage to the center of the cornea caused by PRK for hyperopia was not very severe. But it is important to evaluate further the efficacy and safety of PRK for hyperopia.     

Increase of free oxygen radicals in aqueous humour induced by selective Nd:YAG laser trabeculoplasty in the rabbit

PURPOSE: To investigate the impact of selective Nd:YAG laser trabeculoplasty on free oxygen radicals and antioxidant enzymes of the aqueous humour in the rabbit. METHODS: One eye of 18 rabbits was subjected to 360 degrees selective laser trabeculoplasty (LT) with a frequency-doubled Nd:YAG laser (532 nm). The anterior chamber aqueous humour was aspirated 3, 12 hours and 1, 3, 7, 10 days after treatment. Lipid peroxide (LPO) and glutathione S transferase (GST) levels and superoxide dismutase (SOD) activities of aqueous humour were measured. RESULTS: Concentrations of LPO in the aqueous humour of the treated eyes were significantly higher than the untreated eyes until the 7th day. Aqueous SOD activity significantly decreased 3 hours after LT and remained low until day 7. Aqueous GST levels were significantly decreased between 12 hours and 7 days after the LT. CONCLUSIONS: Selective LT was followed by an immediate increase in the aqueous humour LPO concentration and decreases of SOD and GST in the rabbit, probably due to photovaporization and photodisruption caused by the frequency-doubled Nd:YAG laser. The increased aqueous LPO levels suggest that free oxygen radicals are formed in the pigmented trabecular meshwork during LT, and may be responsible for the inflammatory complications of this procedure.