Changes in tear flow and tear film stability after photorefractive keratectomy.

PURPOSE: To investigate the changes in tear flow and tear film stability after photorefractive keratectomy (PRK) for myopia. MATERIAL AND METHOD: One eye of 32 patients underwent unilateral PRK procedure for the correction of myopia ranging from -1.50 to -6.00 diopters (D) (mean -3.65 +/- 1.55 D). Schirmer test values and break-up time (BUT) scores were measured 6 weeks after the PRK procedure. Unoperated, contralateral eyes were used as control eyes for each patient. The Schirmer test scores and BUT values were statistically analyzed using independent t test. RESULTS: The mean Schirmer test value was 14.45 +/- 7.79 mm in the operated eyes. It was 28.83 +/- 5.89 in the control eyes. The decrease in Schirmer test value was statistically significant (t = 8.28, p = 0.0001). The mean BUT scores were 13.19 +/- 5.09 s in the operated eyes and 27.83 +/- 9.31 s in the control eyes. The decrease was statistically significant (t = 7.86, p = 0.0001). CONCLUSION: PRK causes a decrease in tear flow and tear film stability that is probably caused by decreased corneal sensation after PRK.     

Nerve growth factor concentration and implications in photorefractive keratectomy vs 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). DESIGN: Prospective, nonrandomized comparative clinical trial. METHODS: 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, tear film breakup time (BUT) and Schirmer values were measured before and 1 day, 1 week, 1 month, 3 months, and 6 months after surgery. RESULTS: The postoperative mean tear NGF/total tear protein (NGF/tP) ratio increased in both PRK and LASIK patients compared with preoperative levels (P < .0001). At 1 week and 1 month postoperatively, the NGF/tP ratio was higher in PRK than in LASIK subjects (P < .0001). Before 6 months postoperatively, the mean corneal sensation after LASIK in the ablated zone was lower than the preoperative sensation (P < .0001), but this was not the case in PRK subjects. Mean BUT and Schirmer values were significantly lower in LASIK-treated eyes compared with PRK-treated eyes up to 6 months postoperatively (P < .0001). The early postoperative tear NGF/tP ratio correlated with the postoperative 6-month value of corneal sensation, BUT, and Schirmer values. CONCLUSIONS: The difference in the postoperative corneal sensation and ocular surface dryness between PRK-treated and LASIK-treated eyes might be related to the difference in the early postoperative levels of NGF, which is a potent nerve growth stimulator.     

准分子激光屈光性角膜术对泪膜稳定性的影响

目的：研究准分子激光屈光性角膜术（ＰＲＫ与ＬＡＳＩＫ）前后泪膜的变化。方法：选择８７ 眼近视眼患者分两组进行ＰＲＫ和ＬＡＳＩＫ术,分别观察患眼术前和术后３ 天、１０ 天、１ 月、３ 月及６ 月（ＬＡＳＩＫ组未查） 的主观感觉、上皮缺损情况、泪膜形态、非侵犯性泪膜破裂时间（ＮＩＢＵＴ） 和侵犯性泪膜破裂时间（ＢＵＴ） ,并对结果作统计学分析。结果：①ＰＲＫ 组有１８ 眼感觉较术前干燥,ＬＡＳＩＫ 组无一例出现症状,两组相比有显著性差异（ Ｐ＜ ０ ．０１） 。②术后３ 天、１０ 天ＰＲＫ组术后上皮缺损者明显多于ＬＡＳＩＫ组,两组相比有显著性差异（ Ｐ＜０．０１） 。③两组各眼术前、术后的泪膜形态均无改变。④ＰＲＫ组ＢＵＴ术后３ 天、１０ 天、１ 月较术前明显缩短,有显著性差异（Ｐ＜０．０１）;ＬＡＳＩＫ 组术前、术后各期相比均无显著性差异（ Ｐ＞ ０．０５）。结论：ＰＲＫ可影响泪膜的稳定性,但随着角膜的愈合而逐渐恢复,ＬＡＳＩＫ由于保留了角膜上皮的完整性而不影响其稳定性。角膜上皮层结构的改变是引起泪膜稳定性下降的主要原因。     

Decreased tear secretion after laser in situ keratomileusis for high myopia

PURPOSE: To investigate the changes in tear secretion and tear film stability after excimer laser in situ keratomileusis (LASIK) for high myopia. METHODS: One eye of 28 patients underwent unilateral LASIK for the correction of myopia with spherical equivalent refractions ranging from -6.37 to -18.25 D (mean, -11.98 +/- 3.45 D). Schirmer tear test values without anesthesia at 5 minutes and tear break-up time values were measured 4 weeks after LASIK. Unoperated contralateral eyes were used as a control for each patient. The Schirmer tear test and tear break-up time values were analyzed statistically using the independent t-test. RESULTS: The mean Schirmer tear test value was 16.17 +/- 2.50 mm in the operated eyes and 21.07 +/- 7.03 mm in the unoperated (control) eyes of the same patients (P = .001). The mean tear break-up time value was 21.0 +/- 3.55 seconds in the operated eyes and 21.27 +/- 6.79 seconds in the control eyes (P = .85). CONCLUSION: Tear secretion decreased following LASIK probably due to decrease in corneal sensitivity, but tear film stability appeared unaltered.     

Tear secretion following spherical and astigmatic excimer laser photorefractive keratectomy

PURPOSE: To evaluate the effect of spherical and astigmatic excimer laser photorefractive keratectomy (PRK and PARK, respectively) on tear secretion. SETTING: The Vlemma Eye Center, Athens, Greece. METHODS: Forty-eight eyes of 48 patients had PRK (28 eyes) or PARK (20 eyes) for the correction of myopia and combined myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent was -3.96 diopters (D) +/- 1.00 (SD) in the PRK eyes (range -2.00 to -6.50 D) and -3.45 +/- 0.50 D in the PARK eyes (range -1.75 to -6.00 D). Attempted correction aimed at emmetropia. Schirmer I and II and tear film breakup time (BUT) tests were performed preoperatively and 1, 3, and 6 months postoperatively. All tests were correlated to the amount of attempted correction. RESULTS: In the PRK group, the preoperative mean values were Schirmer I, 16.20 mm; Schirmer II, 12.73 mm; and BUT, 16.46 sec. At 1 month, they were 12.23 mm, 8.46 mm, and 13.33 sec, respectively; at 3 months, 13.86 mm, 10.64 mm, and 14.42 sec, respectively; at 6 months, 14.32 mm, 11.32 mm, and 15.36 sec, respectively. In the PARK group, the mean Schirmer I, II, and BUT values were preoperatively 18.52 mm, 14.86 mm, and 17.42 sec, respectively; at 1 month, 14.5 mm, 10.4 mm, and 14.36 sec, respectively; at 3 months, 15.36 mm, 11.81 mm, and 14.72 sec, respectively; and at 6 months, 16.5 mm, 12.15 mm, 16.5 sec, respectively. No correlation to the amount of attempted correction was found. Fellow-eye tests were not affected at any interval. CONCLUSIONS: In the first 6 months after PRK and PARK, tear secretion test values decreased.     

Tear secretion following excimer laser in situ keratomileusis

PURPOSE: To evaluate the effect of laser in situ keratomileusis (LASIK) on tear secretion. METHODS: A non-consecutive series of 42 eyes of 42 patients had LASIK for the correction of myopia and myopic astigmatism. The fellow eye served as a control. The mean preoperative spherical equivalent refraction was -5.25 +/- 1.00 D (range, -1.75 to -11.00 D). Attempted correction aimed at emmetropia. Schirmer I and II, and tear break-up time (BUT) tests were performed preoperatively and at 1, 3, and 6 months postoperatively. All tests were correlated to the amount of the attempted correction. RESULTS: Preoperatively, mean values were Schirmer I: 16.2 mm, Schirmer II: 11.6 mm, and BUT: 16.3 sec. One month after LASIK, mean values were Schirmer I: 12.8 mm, Schirmer II: 9.2 mm, and BUT: 13.3 sec. At 3 months, mean values were Schirmer I: 15.76 mm, Schirmer II: 11.3 mm, and BUT: 14.15 sec. At 6 months, mean values were Schirmer I: 15.96 mm, Schirmer II: 11.66 mm, and BUT: 16.3 sec. No correlation to the amount of attempted correction was found. Fellow eye tests were not affected at any interval. CONCLUSIONS: Tear secretion following LASIK was decreased during 3 months after surgery and was normalized by 6 months.     

Corneal barrier function, tear film stability, and corneal sensation after photorefractive keratectomy and laser in situ keratomileusis

PURPOSE: To compare corneal sensation, corneal barrier function, tear secretion, and tear film stability after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). DESIGN: Prospective, nonrandomized clinical trial. METHODS: In a prospective study, 28 eyes of 15 patients underwent PRK and 115 eyes of 59 patients underwent LASIK to correct myopia. Corneal sensation, corneal epithelial barrier function, tear secretion, and tear film stability were examined preoperatively and 1 week and 1, 3, 6, and 12 months postsurgery. RESULTS: Both PRK and LASIK significantly compromised corneal sensation, increased epithelial barrier function, reduced tear secretion, and deteriorated tear film stability (P < .05, Wilcoxon signed-rank test). Deterioration of corneal sensation was significantly greater after LASIK than after PRK by 3 months postoperatively (P < .05, Wilcoxon rank sum test). Increases in corneal epithelial permeability were more prolonged after LASIK than after PRK. A significant intergroup difference in permeability was observed 1 month after surgery (P < .01). Tear breakup time was significantly shorter in the LASIK group than in the PRK group up to 3 months after surgery (P < .045). CONCLUSIONS: LASIK induces greater and more prolonged damage to corneal sensation, corneal barrier function, and tear film stability than PRK.     

Effect of laser in situ keratomileusis on tear stability

OBJECTIVE: Patients frequently experience dry eye symptoms after laser in situ keratomileusis (LASIK). The mechanisms that lead to these changes are not well understood. The purpose of this study was to investigate the effect of LASIK on tear function. DESIGN: Prospective, comparative, nonrandomized interventional trial. PARTICIPANTS: Fifty-eight consecutive patients (96 eyes) who underwent myopic LASIK treatment. METHODS: The prospective study involved 58 consecutive patients (96 eyes) who underwent sequential or bilateral LASIK for the correction of myopia. Dry eye symptoms, standardized Schirmer test values, basal tear secretion test, and tear break-up time were measured before surgery and 1 day, 1 week, and 1 month after surgery. MAIN OUTCOME MEASURES: Schirmer test value, basal tear secretion value, and tear break-up time. RESULTS: Before surgery, 15.6% of patients (15/96) had dry eye symptoms. After surgery, 94.8% of patients (91/96), 85.4% of patients (82/96), and 59.4% of patients (57/96) experienced dry eye symptoms at 1 day, 1 week, and 1 month, respectively. Schirmer test value (13.32 +/- 10. 67 mm) increased at 1 day (14.48 +/- 10.57 mm; P = 0.25) and subsequently decreased at 1 week (11.18 +/- 9.81 mm; P = 0.05) and at 1 month (10.83 +/- 10.02 mm; P = 0.03). Basal tear secretion test value (8.49 +/- 8.48 mm) decreased at 1 day (6.80 +/- 6.48 mm; P = 0.05), at 1 week (5.97 +/- 6.88 mm; P = 0.005), and at 1 month (5.89 +/- 6.24 mm; P = 0.007). Tear break-up time (5.32 +/- 2.35 seconds) decreased 1 day (4.14 +/- 1.90 seconds; P < 0.001) and 1 week (4.49 +/- 1.70 seconds; P = 0.004) after surgery and recovered by 1 month after surgery (5.09 +/- 3.03 seconds; P = 0.52). Poor preoperative tear functions with a Schirmer test value less than 10 mm was a significant risk factor (72% vs. 46%; relative risk, 1.58 [1.10-2.26]) for experiencing dry eye symptoms at 1 month after surgery. CONCLUSIONS: Dry eye symptoms are common after myopic LASIK surgery. Laser in situ keratomileusis significantly altered the tear break-up time, Schirmer test values, and basal tear secretion. Patients with preexisting tear flow abnormality as demonstrated by Schirmer test values less than 10 mm are especially at risk of experiencing dry eye symptoms.     

高海拔地区激光原位角膜磨镶术后泪膜的变化

目的探讨高海拔地区LASIK术后泪液的变化。方法对240眼LASIK术后4周泪液分泌量及泪膜破裂时间（BUT）进行测定。结果平均泪液分泌量≥10mm者14眼,占5．83％;平均泪液分泌量5～9mm者140眼,占58．34％;平均泪液分泌量〈5mm者86眼,占35．83％。BUT为15～35S者5例（10眼）,占4．17％,BUT为15—10s者6例（12眼）,占5．00％,BUT〈10s者109例（218眼）。占90．83％。结论高海拔地区LASIK术后对泪膜有一定程度的不良影响。发生机制与多种因素有关,术后适当的治疗,可减轻患者的眼部不适。     

Autologous serum eye drops for dry eye after LASIK

PURPOSE: To evaluate the efficacy of autologous serum eye drops for dry eye after LASIK in a prospective, randomized study. METHODS: Fifty-four eyes of 27 male patients who underwent LASIK were divided into two groups; patients who used autologous serum eye drops and those who used artificial tears postoperatively. Schirmer test with anesthesia, tear break-up time (BUT), and rose bengal and fluorescein staining for the ocular surface were prospectively compared between the groups. All values were also compared before and after surgery (at 1 week [except for Schirmer test], 1 month, 3 months, and 6 months) in each group. RESULTS: Tear BUT was greater in the autologous serum eye drops group than in the artificial tears group at 6 months postoperatively. Rose bengal score was lower in patients using autologous serum eye drops than in patients using artificial tears at 1 month and 3 months postoperatively. No significant difference was noted between patients using autologous serum eye drops and patients using artificial tears in the value of Schirmer test with anesthesia and fluorescein scores. In the autologous serum eye drops group, tear BUT was increased at 3 months after LASIK, rose bengal score was lower at 1 month and 3 months, and fluorescein score was lower at 1 month after LASIK compared to preoperative values, respectively. In the artificial tears group, all values (Schirmer test, tear BUT, rose bengal score, and fluorescein score) showed no differences between before and after LASIK. No differences were noted in the subjective scores for dryness between the autologous serum eye drops and artificial tears groups. CONCLUSIONS: The autologous serum eye drops group showed prolongation of the tear BUT and a reduction in rose bengal staining score.     

飞秒激光角膜屈光手术后的泪膜变化

【摘要】 目的 分析飞秒激光制瓣准分子激光原位角膜磨镶术（LASIK）后泪液分泌、泪膜变化及 与干眼的关系。设计 回顾性病例系列。 研究对象 2011年3月-6月在宁波市眼科医院施行飞秒激光 LASIK手术的120例（235眼）近视患者。方法  用Intralse飞秒激光制作蒂位于上方的角膜瓣后行 常规LASIK术。术后次日开始予左氧氟沙星滴眼液每日4次滴眼,1周后停药,0.1%艾氟龙（FML）滴 眼液,第一周每日4次,以后每周逐减一次,至1个月停药。对手术患者分别用角膜荧光素染色检查 、泪膜破裂时间（BUT）、泪液分泌试验来测定患者术前,术后10天,1、3、6个月的泪膜变化情况 。主要指标 角膜荧光素染色、BUT、泪液分泌值。结果 BUT值：术前（15.00±2.56）s,术后10天 ,1、3、6个月分别为（8.51±3.22）s,（11.40±2.71）s,（14.29±3.46）s,（14.84±3.01 ）s。 泪液分泌试验：术前（16.23±3.48）mm,术后10天,1、3、6个月分别为（9.86±3.13）mm ,（13.46±2.72）mm,（15.18±3.02）mm,（16.11±2.84）mm。此二种测试结果,术后10天,1 、3个月分别与术前比较,差异均有统计学意义（P均＜0.05）,术后6个月与术前比较,差异无统 计学意义（P=0.22）。结论 飞秒激光制瓣准分子激光原位角膜磨镶术,术后早期可致泪膜稳定性 下降,泪液分泌减少,术后3个月开始泪液分泌功能和泪膜稳定性逐渐恢复,术后6个月泪膜情况已 趋稳定。（眼科, 2012, 21: 387-389）     

Investigation of tear film change after recovery from acute conjunctivitis

PURPOSE: To study the changes of tear film after recovery from acute conjunctivitis. METHODS: This study involved 73 eyes of 56 consecutive patients who complained of dry eye after recovery from acute conjunctivitis at the Zhongshan Ophthalmic Center. Excluded were other factors that could affect the stability of the tear film. Tear film breakup time (BUT), Schirmer 1 test (S1T), tear meniscus height (TMH), and fluorescein staining (FL) were performed on both recovered and healthy eyes. The scores were measured at 3, 7, 14, 21, and 30 days after recovery. RESULTS: Compared with the results of the healthy eyes, most scores of BUT, S1T, TMH, and FL were all abnormal until day 30 after recovery from acute conjunctivitis. BUT decreased at 3, 7, 14, and 21 days (P < 0.05). S1T decreased at 3, 7, and 21 days (P < 0.05). TMH values became less than normal at 3, 7, and 14 days (P < 0.05). FL increased significantly at 7, 14, and 21 days (P < 0.05). At 30 days after recovery, all of the test scores returned to normal (P > 0.05). CONCLUSIONS: During acute conjunctivitis, inflammation and topical therapeutic agents can alter the tear film secretion, resulting in dry eye for nearly 1 month in recovered eyes. To minimize the effect of topical agents to the tear film, individualized treatment instead of frequent instillation of topical agents is recommended for acute conjunctivitis.     

Comparison of corneal sensitivity and tear function following Epi-LASIK or laser in situ keratomileusis for myopia

PURPOSE: To compare the effect of Epi-LASIK or Laser In Situ Keratomileusis (LASIK) on corneal sensitivity and tear function. DESIGN: Prospective, non-randomized comparative clinical trial. METHODS: Seventy-nine eyes (Group A) underwent Epi-LASIK and 61 eyes underwent LASIK (Group B) for the treatment of myopia. Matching parameters between the groups were age and attempted correction. Corneal sensitivity, tear break-up time (BUT), and Schirmer test II were evaluated before and at one, three, and six months after the procedure. RESULTS: Corneal sensitivity and BUT were decreased at one month in Group A (P < .001) to be restored by the third month (P = .71 and P = .58, respectively). In Group B, corneal sensitivity and BUT were reduced postoperatively (P < .001). There was a significant difference in corneal sensitivity between the two groups at all postoperative intervals. Schirmer test II was not significantly decreased postoperatively in Group A. In Group B, it was decreased at one and three months and restored by the sixth month. CONCLUSION: Epi-LASIK-treated eyes had faster rehabilitation of corneal sensitivity and tear function than LASIK-treated eyes.     

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。     

甾体和非甾体类消炎药对LASIK术后泪膜及角膜知觉的影响

目的探讨甾体类和非甾体类消炎药对准分子激光原位角膜磨镶术(LASIK)后泪膜及角膜知觉的影响。方法将54例(100只眼)接受LASIK治疗的近视患者随机分为2组,术后分别给予0．3％妥布霉素 0． 1％地塞米松滴眼液及0．3％妥布霉素 0．1％普拉洛芬滴眼液。术后1、2、4周对随访患者进行Schirmer试验、泪膜破裂时间(BUT)、中央角膜知觉检查和主观干眼症状调查。结果术后各时间段两组患者的Schirmer值、主观干眼症状评分差异无显著性意义。术后1、2周两组BUT值和中央角膜知觉的差异有统计学意义,而术后4周差异无显著性。结论 LASIK术后早期,应用NSAIDs的患者泪膜更不稳定,角膜知觉的恢复较甾体类消炎药组缓慢。 NSAIDs对泪膜稳定性及中央角膜知觉的影响大于甾体类消炎药。     

慢性肾功能衰竭患者泪液分泌及泪膜稳定性的研究

目的:探讨慢性肾功能衰竭(chronic renal failure,CRF)患者泪液分泌及泪膜稳定性的变化。方法:对48例96眼慢性肾衰患者眼及48例96眼正常人眼进行比较研究,观察指标包括Schirmer试验、泪膜破裂时间(BUT)和角膜荧光素染色情况。结果:CRF组Schirmer试验结果为10.17±2.19mm,泪膜破裂时间(BUT)为8.11±2.08s,均低于对照组,差异有统计学意义(t=-11.103,P<0.01;t=-10.807,P<0.01)。角膜荧光素染色阳性率12.5%(12/96),高于对照组,差异有统计学意义(χ2=7.705,P<0.01)。结论:慢性肾功能衰竭患者泪液分泌减少,泪膜稳定性较差,易患干眼症。     

超声乳化白内障吸除术后泪膜和泪液分泌变化的Meta分析

目的:探讨超声乳化白内障吸除术对泪膜及泪液分泌变化的影响。方法:检索PubMed,Web of knowledge、中华期刊网和中国生物医学文献数据库,辅以Google网络检索和手工检索,筛选得到6篇2000-01/2009-08发表的关于超声乳化白内障吸除术对泪膜和泪液分泌变化影响的研究,以手术前与术后3mo泪膜破裂时间(break-up time,BUT)和基础泪液分泌试验(SchirmerⅠtest,SⅠt)均数差值(relativedifference,RD)为效应指标,应用随机效应模型对入选文献的数据资料进行Meta分析。结果:术后3mo时BUT仍低于手术前水平,差异有统计学意义[RD的加权平均估计值为1.34,95%可信区间为(0.40,2.30),P=0.01]。术后3mo时SⅠt值略低于手术前水平,但差异无统计学意义[RD的加权平均估计值为0.80,95%可信区间为(-0.14,1.75),P=0.10]。结论:术后3mo时,超声乳化白内障吸除术后泪膜稳定性仍降低,但基础泪液分泌量已基本恢复至术前水平。     

Effect of preoperative tear function on early functional visual acuity after laser in situ keratomileusis

PURPOSE: To assess the effect of preoperative tear function on early changes in functional visual acuity (FVA) after laser in situ keratomileusis (LASIK). SETTING: Minamiaoyama Eye Clinic, Tokyo, Japan. METHODS: This prospective single-center study assessed the effect of preoperative and postoperative tear functions on FVA in 30 eyes of 15 patients who had LASIK. Functional visual acuity was defined as the binocular recognition acuity measured by the FVA tester (Wellsystem) during a 10-second, blink-free period. All patients had a Schirmer test with anesthesia and tear-film breakup time (BUT) measurements preoperatively and 1 day and 1 week after LASIK. Corneal topography and Landolt visual acuity and FVA measurements were performed before surgery and 1 day and 1 week after LASIK. Eyes with a Schirmer test reading less than 5.0 mm and a BUT less than 5 seconds were grouped as definite dry eye (DDE). Eyes with a normal Schirmer test score but a shortened BUT were grouped as probable dry eye (PDE). RESULTS: In all patients, the best uncorrected Landolt visual acuity was 20/20 or better at the postoperative examination times. In the DDE group, the mean preoperative FVA declined from 1.2 to 0.75 +/- 0.16 (SD) at 1 day and increased to 1.2 at 1 week. No change in FVA was observed postoperatively in the PDE group. CONCLUSION: Laser in situ keratomileusis patients with low basal tearing and full uncorrected distance Landolt acuity may experience a transient decrease in FVA that returns to baseline within 1 week.     

准分子激光角膜原位磨镶术后泪膜变化及与角膜知觉关系的研究

目的 :探讨准分子激光角膜原位磨镶术 (laserinsitukeratomileusis ,LASIK )后泪液 ,泪膜变化及其与角膜知觉的关系 ,研究LASIK术后发生眼干现象的原因。方法 :对 5 0名近视眼患者实施双眼LASIK手术 ,分别测定其术前 ,术后一周 ,二周和四周的泪液分泌值 ,泪膜稳定性和角膜知觉值 ,其中泪液分泌值用Schirmerl实验测定 ,泪膜稳定性是通过用英国产KEELER泪膜镜测定非侵入性泪膜破裂时间(NIBUT)来评价 ,角膜知觉用美国产CochetBonnet角膜知觉计来测定。结果 :1 NIBUT值 (单位 :秒 ) :术前为 2 6 2 0± 15 12 ,术后一周为 18 5 6± 15 2 4,术后二周为 18 90± 11 64 ,术后四周为2 4 10± 14 2 4,术后各组分别与术前的NIBUT值进行配对t检验 ,差异均有显著性意义 (P <0 0 5 )。 2 角膜知觉 (单位 :mm) :术前为 5 5 60± 8 18,术后一周为 2 4 78± 19 82 ,术后二周为 3 4 0 2± 19 2 8,术后四周为 5 3 3 0± 10 3 8,术后各组分别与术前的角膜知觉值进行配对t检验 ,术后一周、二周组与术前的差异均有显著性意义 (P <0 0 5 ) ,术后四周与术前的差异无显著性意义 (P >0 0 5 )。 3 Schirmerl值 (单位 :mm ) :术前为 2 0 92± 10 80 ,术后一周为 17 83± 10 64 ,术后二周为 2 0 0 6±11 42 ,术后四周     

Effect of tear film break-up on higher order aberrations of the anterior cornea in normal, dry, and post-LASIK eyes

PURPOSE: To evaluate the effects of tear film breakup on higher order aberrations of the anterior cornea in normal, dry, and post-LASIK eyes. METHODS: In a prospective study, 120 eyes (120 subjects) comprised three groups: post-LASIK eyes, dry eyes, and normal eyes. Tear film break-up time (BUT) was measured by fluorescein dye under slit-lamp microscopy. Corneal topographies were measured by videokeratography immediately after the following times: post-blink, 1/2 BUT, BUT, and after normal saline application. VOL-Pro software processed topographies to obtain and analyze higher order aberrations (3rd through 6th orders over 6 mm) of the anterior comeal surface. RESULTS: The measurement time scale was set by the BUT: significantly less for dry eyes (8.3 +/- 3.4 seconds) than post-LASIK eyes (11.3 +/- 5.1 seconds) or normal eyes (10.3 +/- 5.6 seconds). Normal and dry eye subjects showed a pattern of significant increase of aberrations from post-blink through BUT and decrease of aberrations after saline addition in coma, trefoil, and 3rd through 6th order aberrations. Post-LASIK eyes exhibited no significant difference between phases. CONCLUSIONS: Disruption of the tear film increases anterior corneal higher order aberrations in normal eyes and more rapidly in dry eyes. The increase in aberrations caused by conventional LASIK is greater than that of tear film-related effects.