LASIK术后角膜知觉的变化及干眼的发生

目的：探讨准分子激光原位角膜磨镶术（LASIK）后角膜知觉的变化及其对干眼的影响与切削深度的关系。 方法：观察上方蒂做瓣的LASIK手术30例（60眼），观察指标包括患者术中切削深度及术前，术后1wk，lmo，3mo的角膜中央知觉、基础泪液分泌量、泪膜破裂时间（BUT）、角膜荧光素钠染色评分、干眼主觉症状评分。 结果：术后1wk，1mo角膜知觉敏感度与术前相比差异均非常显著（P〈0．01），术后3mo平与术前相比差异无统计学意义（P〉0．05）；术后1wk患者的主觉症状与术前相比无显著差异（P=0．079〉0．05），术后mo时差异显著（P=0．025〈0．05），术后3mo时差异极其显著（P=0．001〈0．01）；患者术后泪流量在术后1wk：1mo时明显低于术前（P〈0．01），直至术后3mo仍未恢复至术前水平（P〈0．01）；术后1wk，1mo，3mo泪膜破裂时间缩短，术后3mo时与术前相比差异显著（P〈0．01）；角膜荧光素钠染色评分方面，术后1mo时角膜上皮损伤最明显，术后3㈤时与术前仍有显著差异（P〈0．01）直线回归与相关分析结果，说明在两者之间存在直线相关的关系r=0．798，P〈0．01。 结论：LASIK术后角膜中央知觉明显下降并随时间延续而逐渐恢复，3mo时与术前无统计学差异；但是干眼的相关指标并未随之恢复至术前水平；术后角膜知觉的下降与术中切削深度间存在正相关。     

角膜基质切削深度对超薄瓣LASIK术后中央角膜知觉的影响

目的探讨角膜基质切削深度对超薄瓣准分子激光原位角膜磨镶术（LASIK）术后中央角膜知觉的影响。方法回顾分析2011年6月至12月在我院眼科中心行超薄瓣LASIK手术的84例（168只眼）患者,按角膜基质切削深度（ADCS）进行分组;1组〈50μm,2组50～80μm,3组〉80μm。分别测量术前、术后1个月、3个月中央角膜知觉值,并对测量数据进行统计分析。结果术后1个月各组角膜知觉值均有不同程度的下降,各组间的差异有明显统计学意义。角膜切削深的组3与组1和组2相比,中央角膜知觉下降明显。术后3个月时中央角膜知觉有不同程度的恢复,但是三组间仍有明显的统计学差异,组3的中央角膜知觉值仍低于组1和组2,需要更长时间的恢复。结论角膜基质切削深度与中央角膜知觉的下降有显著关系,基质切削越深,中央角膜知觉下降越明显。     

角膜瓣蒂的位置对LASIK术后早期角膜知觉的影响

目的　探讨角膜瓣蒂的不同位置对LASIK手术后角膜知觉的影响。方法　对 3 1名双眼屈光参差 <1 0D ,术前双眼角膜中央知觉相同的近视眼患者行LASIK手术 ,其中左眼角膜瓣蒂的位置在上方 ,右眼角膜瓣蒂的位置在鼻侧。应用CohetBonnet角膜知觉计分别测定术前、术后一周、二周和四周各眼的角膜中央的角膜知觉。结果　将术后一周、二周时左右眼的角膜知觉阈值进行配对t检验 ,其差异有显著性意义 (P <0 0 5 )。将术后四周左右眼的角膜知觉阈值进行配对t检验 ,其差异无显著性意义 (P >0 0 5 )。结论　角膜瓣蒂的位置不同对LASIK术后早期角膜知觉的影响也不同 ,在术后一周和二周时角膜瓣蒂的位置在上方的角膜知觉低于角膜瓣蒂的位置在鼻侧的角膜知觉 ,在术后四周时 ,随着角膜知觉的恢复双眼的角膜知觉已无显著性差异。     

LASIK角膜瓣蒂部位置不同对术后角膜知觉的影响

目的比较角膜瓣的蒂部位于颞侧和上方的LASIK治疗近视对角膜知觉影响差异。方法随机性、前瞻性、单盲研究。本研究包含100例(200只眼)近视患者,所有病例的双眼屈光度相近、术前矫正视力≥1.0且可完全矫正。随机将患者一眼的角膜瓣蒂部置于上方,另一眼置于颞侧,然后进行常规LASIK手术。分别在术前、术后1天、1周、1、3、6个月和12个月时,使用Cochet-Bonnet角膜知觉计检查中央角膜知觉,对数据进行统计学分析。结果颞侧蒂组和上方蒂组的中央角膜知觉在LASIK术后各个时间点均比术前水平有不同程度的下降,颞侧蒂组角膜知觉在1个月时恢复到术前水平,上方蒂组则需要到术后3个月时才达到术前水平。颞侧蒂组和上方蒂组两组间的中央角膜知觉在LASIK术前没有显著差异；在术后1天、1周及1个月时差异有显著意义(P＜0.05)；在术后3、6个月和12个月时,两组间没有显著差异。结论颞侧蒂组与上方蒂组的中央角膜知觉在LASIK术后早期均显著下降,而颞侧蒂组的中央角膜知觉敏感度损失较小、恢复较早。     

飞秒激光LASIK术后早期不同部位角膜敏感性变化研究

目的 评估飞秒激光LASIK术后早期角膜中央和周边区敏感性的恢复情况.方法 观察飞秒激光LASIK手术的患者40例(71只眼),分别在术前、术后1周、1月、3月使用Cohet-Bonnet角膜知觉计检查角膜中央、上方、下方、鼻侧和颞侧五个部位的敏感性,统计方法采用Kruskal Wallis H秩和检验和Mann-Whitney检验,以P＜0.05表示有统计学意义.结果 飞秒激光LASIK手术后早期,在五个测量部位,术后1周、1月、3月角膜敏感性均低于术前,差异具有统计学意义(P＜0.05).术后1周、1月、3月各个时间段,角膜上方敏感性均高于其他部位,差异具有统计学意义(P＜0.05).术后3个月,中央区角膜敏感性小于其他部位,差异具有统计学意义(P＜0.05).中央角膜敏感性与角膜中央切削深度、中央角膜厚度、术前等效球镜度无相关性(r=0.005;-0.105;0.03,P=0.97;0.38; 0.80).结论 飞秒激光LASIK术后早期角膜敏感性明显下降,角膜瓣蒂所在位置的敏感性较其他位置下降程度低,中央区角膜敏感性的恢复慢于其他位置,角膜中央敏感性与中央切削深度、角膜中央厚度、术前等效球镜度无相关.     

虹膜定位引导的 SBK和超薄瓣 LASlK 治疗超高度近视的疗效

目的：比较分析虹膜定位引导的前弹力层下准分子激光角膜磨镶术( SBK)和虹膜定位引导的超薄瓣准分子激光原位角膜磨镶术( LASIK)治疗超高度近视的疗效。
　　方法：超高度近视患者行虹膜定位引导的SBK治疗的患者32例64眼,行虹膜定位引导的超薄瓣LASIK治疗的患者42例84眼,年龄22~35岁,术前等效球镜屈光度-9.00~-11.00D,随访6mo观察两术式的治疗效果。观察指标包括裸眼视力( UCVA)、屈光状态、裂隙灯检查、残余角膜基质床厚度、角膜地形图、角膜厚度、角膜瓣厚度并发症。
　　结果：术后随访6mo,UCVA≥1.0者SBK组为93.8%,超薄瓣LASIK组为92.9%,两术式相比较差异无统计学意义;残余屈光度在±0.50 D以内者SBK组为89.1%,超薄瓣LASIK组为84.5%,两术式相比较差异无统计学意义;SBK组角膜后表面 Diff 值为0.046±0.012μm,超薄瓣LASIK组为0.056±0.015μm,两术式相比较差异无统计学意义;术后 SBK 组角膜中央残余基质厚度为328.6±14.7μm,超薄瓣LASIK组为301.2±21.6μm,两组相比较差异有显著性( t=3.127, P=0.001);SBK 组、超薄瓣LASIK组患者泪膜破裂时间( BUT )分别为11.38±4.02 s和17.81±4.89s,两组相比较差异无统计学意义。术后两组患者均无严重并发症。
　　结论：虹膜定位引导的SBK和超薄瓣LASIK治疗超高度近视具有良好的效果,与LASIK相比SBK制作角膜瓣的预测性更好,可以降低医源性圆锥角膜发生的概率;术后干眼症状轻、恢复更快,对于超高度近视患者来说是一种经济有效的手术治疗方式。     

LASIK手术前后角膜知觉敏感度变化

目的探讨 LASIK 手术对角膜知觉敏感度的影响.方法采用法国 Luneau 公司生产的角膜知觉敏感度测量计对 52 例 104 眼LASTK 手术患者观察术前、术后 1 周、术后 1 个月、3个月、6个月的中央角膜知觉敏感度的变化情况.结果 LASIK 术后 3 个月内角膜知觉敏感度明显下降,随术后时间的延长,角膜知觉敏感度渐恢复.结论 LASIK 手术后可引起角膜知觉敏感度的下降,至术后 6 个月时可恢复接近术前水平.     

虹膜定位引导的SBK和超薄瓣LASIK治疗超高度近视的疗效

目的：比较分析虹膜定位引导的前弹力层下准分子激光角膜磨镶术(SBK)和虹膜定位引导的超薄瓣准分子激光原位角膜磨镶术(LASIK)治疗超高度近视的疗效。

方法：超高度近视患者行虹膜定位引导的SBK治疗的患者32例64眼,行虹膜定位引导的超薄瓣LASIK治疗的患者42例84眼,年龄22～35岁,术前等效球镜屈光度-9.00～-11.00D,随访6mo观察两术式的治疗效果。观察指标包括裸眼视力(UCVA)、屈光状态、裂隙灯检查、残余角膜基质床厚度、角膜地形图、角膜厚度、角膜瓣厚度并发症。

结果：术后随访6mo,UCVA≥1.0者SBK组为93.8%,超薄瓣LASIK组为92.9%,两术式相比较差异无统计学意义; 残余屈光度在±0.50D以内者SBK组为89.1%,超薄瓣LASIK组为84.5%,两术式相比较差异无统计学意义; SBK组角膜后表面Diff值为0.046±0.012μm,超薄瓣LASIK组为0.056±0.015μm,两术式相比较差异无统计学意义; 术后SBK组角膜中央残余基质厚度为328.6±14.7μm,超薄瓣LASIK组为301.2±21.6μm,两组相比较差异有显著性(t=3.127,P=0.001); SBK组、超薄瓣LASIK组患者泪膜破裂时间(BUT)分别为11.38±4.02s和17.81±4.89s,两组相比较差异无统计学意义。术后两组患者均无严重并发症。

结论：虹膜定位引导的SBK和超薄瓣LASIK治疗超高度近视具有良好的效果,与LASIK相比SBK制作角膜瓣的预测性更好,可以降低医源性圆锥角膜发生的概率; 术后干眼症状轻、恢复更快,对于超高度近视患者来说是一种经济有效的手术治疗方式。     

Epi-LASIK术后角膜中央知觉及泪膜稳定性的临床观察

目的:观察微型角膜刀准分子激光上皮瓣下角膜磨镶术(epipolis laser in situ keratomileusis,Epi-LASIK)术后角膜中央知觉和泪膜稳定性的变化。方法:选择92例184眼近视患者行Epi-LASIK手术,其中低中度近视组48例96眼,高度近视组44例88眼。观察术眼术前及术后1,3,6mo的角膜中央知觉、泪膜破裂时间(break-up time,BUT)、泪液分泌量(SchirmerⅠ实验),并对结果进行统计学分析。结果:两组术后角膜中央知觉及泪膜稳定性均有不同程度的下降。低中度近视组术后1mo角膜中央知觉及BUT与术前比有显著性差异(P<0.05),术后3mo时角膜中央知觉及BUT已恢复。高度近视组术后1,3mo角膜中央知觉及BUT与术前比有显著性差异(P<0.05),术后6mo时角膜中央知觉及BUT已基本恢复。高度近视组角膜中央知觉和泪膜稳定性减退更明显,恢复时间更长。两组术后泪液分泌量(SchirmerⅠ实验)分别与术前相比无显著性差异。结论:Epi-LASIK术影响角膜中央知觉和泪膜的稳定性。高度近视对角膜中央知觉和泪膜稳定性的影响比中低度近视大而且持续时间长,但最终可随着角膜的愈合而恢复。     

飞秒激光制瓣LASIK术后角膜内皮细胞的观察

目的：：观察飞秒激光制瓣 LASIK 术后角膜内皮细胞的形态。方法：随机选取2013-05/09接受飞秒激光制瓣LASIK手术的近视患者45例88眼,术前、术后1 mo和术后1 a时,使用非接触式角膜内皮细胞仪测量患者角膜中央区单位面积内的角膜内皮细胞形态,测量指标包括角膜内皮细胞数目、角膜内皮细胞密度、六边形细胞百分比、角膜内皮细胞平均面积、角膜内皮细胞面积标准差和细胞面积变异系数等,对测量结果进行统计学分析。结果：所有患者手术顺利,随访期内未见并发症发生;术后1mo时患者角膜内皮细胞密度为2815.34±297.07个/mm2,较术前减少2.64%(t=4.60,P=0.00),术后1mo和术后1a的角膜内皮细胞密度差异无统计学意义(P>0.05);术后1 mo 时患者角膜内皮细胞面积标准差为118.47±31.58μm2,较术前显著增加(t=-3.87,P=0.03),而术后1 mo和术后1 a角膜内皮细胞面积标准差测量值差异无统计学意义(P>0.05);角膜内皮细胞数目、六边形细胞百分比、角膜内皮细胞平均面积和细胞面积变异系数等指标在手术前后各时间点的测量值差异均无统计学意义(P>0.05)。结论：飞秒激光制瓣LASIK术后早期角膜内皮细胞密度较术前轻度下降,但角膜内皮细胞功能未受到显著影响,随访期内未发生进行性角膜内皮细胞丢失。     

Cyclosporine 0.05% ophthalmic preparation to aid recovery from loss of corneal sensitivity after LASIK

PURPOSE: To determine whether cyclosporine (0.05%) can safely and effectively accelerate corneal nerve regeneration after LASIK, thereby facilitating faster recovery of corneal sensitivity. METHODS: This prospective, randomized, single-center clinical study comprised 44 eyes of 22 patients scheduled to undergo bilateral LASIK. One eye was randomly assigned to receive cyclosporine drops twice daily for 3 months in addition to standard postoperative LASIK medication. Corneal sensitivity was measured using the Cochet-Bonnet esthesiometer in four areas outside and five areas inside the LASIK flap preoperatively and at 1 day, 1 week, 1 month, and 3 months postoperatively. Safety parameters of best spectacle-corrected visual acuity and the incidence of adverse events were also collected. RESULTS: For all four points outside the LASIK flap, normal corneal sensitivity was maintained throughout the study. In addition, no significant difference was found between the cyclosporine-treated eyes and the control eyes at these points. All points within the LASIK flap except the point closest to the hinge demonstrated profound corneal hypoesthesia at 1 day, 1 week, and 1 month postoperatively with no differences noted between the control and cyclosporine-treated eyes. These same points had statistically significantly greater corneal sensitivity in the cyclosporine group relative to the control group (P< or =.011) at 3 months postoperatively. CONCLUSIONS: Cyclosporine was shown to significantly improve corneal sensitivity at 3 months after LASIK, which suggests that topical cyclosporine promotes enhanced corneal nerve regeneration.     

Subbasal nerve fiber regeneration after LASIK and LASEK assessed by noncontact esthesiometry and in vivo confocal microscopy: prospective study

PURPOSE: To evaluate recovery of the corneal subbasal nerve plexus and corneal sensitivity after myopic laser in situ keratomileusis (LASIK) and laser-assisted subepithelial keratectomy (LASEK). SETTING: Manchester Centre for Vision, Royal Eye Hospital, Manchester, United Kingdom. METHODS: Thirty LASEK patients and 20 LASIK patients had slit-scanning confocal microscopy and noncontact corneal esthesiometry preoperatively and 1, 3, and 6 months after surgery. Images of the subbasal nerve plexus were analyzed using customized software to evaluate nerve regeneration. RESULTS: Central corneal sensitivity decreased significantly 1 month after LASEK and LASIK and returned to normal levels after 3 months. Corneal subbasal nerve fiber density, nerve branch density, nerve fiber length, and nerve fiber width decreased significantly 1 month after LASIK and had not returned to the preoperative levels by 6 months. Nerve fiber tortuosity decreased significantly 1 month after LASEK and returned to the preoperative levels 3 months after surgery. There were no significant differences in nerve fiber tortuosity before and after LASIK. Neither corneal sensitivity nor nerve fiber morphology was different between the 2 groups at any postoperative visit. CONCLUSIONS: Corneal sensitivity and subbasal nerve morphology were adversely affected by LASEK and LASIK. Corneal sensitivity recovered 3 months after the procedure, but subbasal nerves were still abnormal after 6 months. Despite the different forms of surgical trauma to corneal nerves with LASIK and LASEK, there was no apparent difference in the time course of recovery of corneal structure and function.     

Corneal sensation after laser in situ keratomileusis

PURPOSE: To report the time course for the return of corneal sensation following laser in situ keratomileusis (LASIK). SETTING: University-based retractive surgery practice. METHODS: Twenty-eight eyes of 18 patients having LASIK were evaluated. Preoperative and postoperative corneal sensation at the nasal flap hinge, at the central cornea, and within the temporal flap edge were measured before and after LASIK for a 3 week period using the Cochet-Bonnet esthesiometer (Luneau). RESULTS: Corneal sensation initially decreased in all 3 positions of the flap measured after LASIK; the greatest decrease was in the central cornea. Near preoperative corneal sensation returned by 3 weeks. The degree of sensation loss did not appear to correlate with the ablation depth. CONCLUSION: Corneal sensation is significantly decreased for approximately 2 to 3 weeks after LASIK, centrally greater than nasally at the flap hinge or temporally within the flap edge, but it generally returns to near the preoperative level by 3 weeks postoperatively.     

The effect of hinge position and depth plate on the rate of recovery of corneal sensation following LASIK

PURPOSE: To evaluate and compare the effect of hinge position and flap thickness on recovery rate of corneal sensation after (LASIK). DESIGN: Prospective, randomized clinical study. METHODS: Forty eyes of 40 patients underwent LASIK to correct myopia ranging from -1.00 to -2.50 diopters. Corneal sensitivity was measured preoperatively and each month after surgery until recovery to preoperative level. The nasal-hinged ACS microkeratome (NH) with depth plates of 130 and 160 microm and the superior-hinged Hansatome microkeratome (SH) with depth plates of 160 and 180 microm were used for corneal flap creation. The eyes were divided into four groups according to the hinge position and depth plate (DP): group 1, NH and 130 microm DP; group 2, NH and 160 microm DP; group 3, SH and 160 microm DP; group 4, SH and 180 microm DP. RESULTS: Corneal sensitivity returned to preoperative level after 3.7 (+/- 0.4), 4.4 (+/- 0.6), 5.4 (+/- 0.8), and 5.8 (+/- 0.9) months, respectively, in groups 1, 2, 3, and 4. Statistically significant differences were found between groups 1 and 2, but not between groups 3 and 4. Corneal sensitivity gradually returned to preoperative levels in all groups. Sensitivity of the hinge area was higher than other areas at every time point. CONCLUSIONS: The results suggest that after LASIK, hinge position and flap thickness seem to be important factors in the rate of return of corneal sensitivity. A thin flap with a nasally placed hinge is associated with the most rapid recovery of corneal sensitivity.     

Change in corneal sensitivity following laser in situ keratomileusis

PURPOSE: To evaluate the change in corneal sensitivity following laser in situ keratomileusis (LASIK). SETTING: Department of Ophthalmology, Maryknoll Hospital, Pusan, Korea. METHODS: The corneal sensitivity in 40 eyes (32 patients) was measured before and 1 and 2 weeks and 1, 3, and 6 months after LASIK. Sensitivity measurements were made with an esthesiometer at central, temporal, inferior, nasal, and superior points on the corneal flap. The eyes were grouped by ablation depth: Group 1, corneal ablation depth less than 100 microns; Group 2, corneal ablation depth more than 100 microns. RESULTS: Corneal sensitivity did not recover to the preoperative level by 6 months after LASIK. Except at the hinge of the corneal flap, the pattern of sensitivity recovery was similar among the various points. Recovery was more rapid at the hinge than at other areas (P < .05). There was a trend toward a greater reduction in corneal sensitivity in Group 2, the group with deeper ablations, than in Group 1. CONCLUSION: The results suggest that lamellar cutting of the cornea during LASIK impairs corneal sensitivity and that the depth of the corneal ablation affects the extent of corneal sensitivity loss and recovery.     

薄瓣LASIK术后中央角膜厚度的变化分析

目的:探讨薄瓣LASIK术后6mo内中央角膜厚度(central corneal thickness,CCT)及屈光度的变化规律.方法:使用非接触式角膜内皮细胞计追踪观察158例302眼近视眼行LASIK手术患者术前及术后1d;1wk;1,3,6mo时CCT的变化,同时记录患者的年龄,预计激光角膜切削值、术中手术光区的大小,术后预计屈光度以及实际屈光度的改变等.结果:术前平均CCT为531.6±24.3μm.术后第1d平均CCT迅速下降,术后1wk平均CCT继续下降,1mo后角膜厚度开始增厚.术前和术后第1d CCT差值与预计激光角膜切削值呈强相关性(r＝0.916,P<0.01).术后6mo和术后1d时CCT的差值,即6mo内CCT的增厚值与患者年龄、术眼屈光度和术中手术光区均呈显著负相关性(r＝ -0.180,P＝0.026;r＝-0.187,P<0.01;r＝-0.171,P＝0 137).术后6mo时,实测平均等效球镜与术前预期值接近(术前等效球镜预期值平均为0.34±0.30D).所有病例随访6mo,无1例发生屈光回退,6mo时裸眼视力均≥0.8,平均视力为1.3±0.2.结论:薄瓣LASIK术后CCT和屈光状态的稳定大约需要6mo时间.术后6mo内CCT增厚值与术前患者年龄、屈光度及术中手术光区大小均呈显著负相关性.术后6mo时实测平均等效球镜值与术前预期值接近.薄瓣LASIK手术治疗近视眼具有良好的预测性和稳定性.     

Corneal sensitivity after photorefractive keratectomy and laser in situ keratomileusis for low myopia.

PURPOSE: To evaluate and compare the recovery of postoperative corneal sensitivity after laser in situ keratomileusis and photorefractive keratectomy for the correction of low myopia. METHODS: In a prospective study, 17 consecutive eyes (17 patients) underwent laser in situ keratomileusis to correct myopia ranging from -3.25 to -6.75 diopters, and another 18 consecutive eyes (18 patients) underwent photorefractive keratectomy to correct myopia from -3.12 to -7.00 diopters. Corneal sensitivity was tested preoperatively and 1 week and 1, 3, and 6 months postoperatively using the Cochet-Bonnet esthesiometer. Corneal sensitivity was tested at the center of the cornea, and in four additional central points 2 mm from the corneal center (nasal, inferior, temporal, and superior). RESULTS: Corneal sensitivity after laser in situ keratomileusis was reduced at the ablated zone during the first 3 months after surgery (Wilcoxon rank sum test, P < .05), and only after 6 months it returned to its preoperative values. However, corneal sensitivity recovered its preoperative values 1 month after photorefractive keratectomy (Wilcoxon rank sum test, P > .05), except for the central corneal point, where 3 months were required. Comparing both groups, corneal sensitivity was more depressed after laser in situ keratomileusis than after photorefractive keratectomy during the first 3 months (Mann-Whitney test, P < .05), except for the nasal central point, although no differences were found between both groups at 6 months (P > .05). CONCLUSIONS: In the correction of low myopia, corneal sensitivity at the ablated zone was more depressed after laser in situ keratomileusis than after photorefractive keratectomy during the first 3 months after surgery. Only after 6 months were corneal sensitivity values similar in both groups.     

Recovery of corneal sensation after myopic correction by laser in situ keratomileusis with a nasal or superior hinge

PURPOSE: To measure corneal sensitivity after laser in situ keratomileusis (LASIK) to determine the time required for recovery of this parameter. SETTING: Ohshima Hospital of Ophthalmology, Fukuoka, Japan. METHODS: Corneal sensation was measured with a Cochet-Bonnet-type esthesiometer in 75 patients before and 1, 3, 6, and 12 months after correction of myopia by photorefractive keratectomy (n = 21) or LASIK (n = 54). RESULTS: Photorefractive keratectomy did not affect corneal sensation. In the LASIK group, a large and significant decrease in corneal sensitivity was apparent at 1 month (P<.05). Although corneal sensitivity appeared to have recovered slightly at 3 months, it remained significantly decreased (P<.05). By 6 or 12 months, the corneal sensitivity in LASIK patients was not statistically different from the preoperative values in the study patients. A significantly greater decrease in corneal sensitivity was apparent in the LASIK patients with a nasal hinge than in those with a superior hinge (F = 7.54, P<.01). Corneal sensitivity was in the normal range in 31.5% of LASIK patients at 3 months and in 57.4% and 82.1% at 6 and 12 months, respectively. CONCLUSION: Recovery of corneal sensation had begun 3 months after LASIK and appeared complete after 12 months.     

Corneal sensation after myopic and hyperopic LASIK: clinical and confocal microscopic study

AIM: To assess the long term (1 year) effect of myopic and hyperopic LASIK on corneal sensation and innervation. METHODS: 83 eyes of 43 patients having LASIK were evaluated. According to the preoperative spherical equivalent, the eyes were divided into three groups: group 1, myopia from -0.75 to -6.00 D; group 2, myopia from -6.25 to -11.50 D; and group 3, hyperopia from 1.25 to 5.00 D. Corneal sensation was measured and in vivo confocal microscopy (IVCM) was done at the central cornea before, and at 1 month, 3 months, 6 months, and 1 year after LASIK. RESULTS: The mean corneal sensation in group 1 was greater than in groups 2 and 3 at all postoperative measurements. The difference between group 1 on one hand and groups 2 and 3 on the other hand was statistically significant at 1 month and 3 months after LASIK and was not statistically significant afterwards. IVCM study of 27 eyes revealed that the number and length of nerve fibre bundles in the sub-basal region decreased after LASIK and was significantly lower at all times after surgery despite the return of corneal sensation to preoperative level. CONCLUSION: After LASIK, central corneal sensitivity is decreased for as long as 6 months or more. The results suggest that lamellar cutting of the cornea during LASIK impairs corneal sensitivity and is related to the ablation depth. The diameter of ablation too may contribute to this drop in sensitivity. The return of corneal sensations does not directly correlate with the regeneration of nerve fibres as determined by confocal imaging. Sensations return to normal values before complete restoration of normal innervation if this indeed ever occurs.