Laser Subepithelial Keratomileusis Research Articles

Morphological Changes of Corneal Keratocytes following Surface Ablation Laser Surgery: An Observational Study from the United Kingdom

Introduction: Laser Subepithelial Keratomileusis (LASEK) is a type of surface ablation laser surgery that offers a solution to patients for correcting their ametropia. In rare instances, LASEK has been associated with complications such as the development of postoperative haze, infection, and poor visual outcomes. Imaging features detected within the patient’s cornea using In-Vivo Confocal Microscopy (IVCM) have aided in identifying the cellular basis of complications like these. Aim: To observe and describe the morphological changes seen on IVCM in patients following LASEK surgery. Materials and Methods: This observational study aimed to assess the quantity and morphology of anterior and posterior keratocytes in adults aged 18 years and older. Five participants (9 eyes) who presented for follow-up appointments following LASEK surgery at Manchester Royal Eye Hospital (MREH), United Kingdom, from July to December 2018 were recruited for the study. The cell counts of the anterior and posterior keratocytes were calculated using the Heidelberg Eye Explorer software. The images were analysed with the Image J program (National Institutes of Health, Bethesda, USA). Nerve fibers were assessed using the ACCMetrics program (University of Manchester, UK). The t-test was used to establish the statistical association between variables. Results: Morphological changes, such as zones of hyperreflectivity beneath the epithelium, were observed in all the recruited participants. Immune cells and sub-basal nerve abnormalities were detected in several participants. The number of keratocytes in the anterior stroma of all the participants was found to be much lower compared to that of the control. Only participant number 3 had a greater number of keratocytes in the anterior stromal layer (454 and 514 cells/mm2 ) compared to the other participants, who had a cell count ranging between 156 to 262 cells/mm2. Conclusion: It is evident that visible changes are noted both quantitatively and morphologically in both the anterior and posterior keratocytes postoperatively. More research is required with larger controlled studies to investigate the IVCM imaging biomarkers and morphological features that represent the wound healing process and the factors influencing visual outcomes, ensuring that postoperative complications can be minimised.

Comparison of Higher-Order Aberrations after LASEK between Two Different Laser Platforms for Low-to-Moderate Myopia

ABSTRACT Purpose To compare the differences in higher-order aberrations (HOAs) after laser subepithelial keratomileusis (LASEK) between two different laser platforms. Methods One hundred and seven eyes of 107 patients were included in this study. Fifty-six eyes underwent LASEK with the Triple-A profile (an ablation profile of the MEL 90 excimer laser) and 51 eyes underwent LASEK with the aspheric (Aberration Smart Ablation [ASA]) profile. Uncorrected distance visual acuity, corrected distance visual acuity (CDVA), corneal topography, and ocular aberrations were measured before and 6 months postoperatively. Results In the ASA group, the values of horizontal trefoil, vertical coma, horizontal coma, spherical aberrations, and total HOAs increased significantly after surgery (all P < 0.05). There were no significant differences in the vertical trefoil between the preoperative and 6-month postoperative periods. In the Triple-A group, there were no differences in vertical trefoil and horizontal trefoil values between the preoperative and 6-month postoperative periods. Compared with the preoperative values, vertical coma, horizontal coma, spherical aberrations, and total HOAs were significantly increased at 6 months after surgery (all P < 0.05). Compared to the Triple-A group, higher horizontal trefoil and horizontal coma were introduced in the ASA group at 6 months postoperatively. Conclusion The Triple-A ablation profile of the MEL 90 excimer laser at a 500-Hz pulse rate was an efficient method to correct myopia, especially for mild-to-moderate myopia, compared with the aspheric ablation model, fewer horizontal trefoil and horizontal coma were induced at 6 months after LASEK. Abbreviations HOAs, Higher-Order Aberrations; LASEK, laser subepithelial keratomileusis; ASA, Aberration Smart Ablation; UDVA, uncorrected distance visual acuity; CDVA, corrected distance visual acuity.

Clinical study on topography-guided laser ablation combined with accelerated corneal collagen cross-linking for early keratoconus

Objective: To study the safety and efficacy of topography-guided customized excimer laser subepithelial ablation combined with accelerated collagen cross-linking technique in treatment of early keratoconus. Methods: Ninteen patients(20 eyes) (13 males 14 eyes, and 6 females 6 eyes), aged 12 to 44 years (24.7±8.0) were diagnosed as keratoconus by three-dimensional corneal topography and tomography, clinical history and examinations, and classified as KC1~KC3. Based on the classical excimer laser subepithelial keratomileusis (LASEK) method, topography guided laser ablation was performed with an excimer laser system (WaveLight EX500). After laser ablation, the corneal stromal bed was immersed with 0.1% riboflavin for 10 minutes, and then was irradiated by ultraviolet light (Avedro KXL) at 30 mW/cm(2) for 4 minutes. All the patients were followed up for more than 12 months. The uncorrected visual acuity (UCVA), diopter, best corrected visual acuity (BSCVA), corneal topography, central corneal endothelial cell density (ECD), hexagonal cell percentage (HEX), coefficient of variation (CV) and other indicators were observed. For normal distribution variables, Dunnett-t test was used before and after operation, and Wilcoxon test was used for variables with abnormal distribution. And the complications were recorded. Results: There was no loss of BSCVA at 12 months postoperatively, 20% of the eyes had no change of BSCVA, and 15% of the eyes gained 1 line of BSCVA, 15% of the eyes gained 2 lines of BSCVA, 50% of the eyes gained 3 lines and more of BSCVA. There was no significant difference in UCVA, BSCVA, manifest refractive spherical equivalent (MRSE) and the cylinder at 3 months postoperatively (P>0.05). The BSCVA were significantly improved at 6 and 12 months postoperatively compared with those before operation (t=3.095, 3.079, <0.05). Although there was no significant difference in UCVA and MRSE, the cylinder was significantly reduced at 6 and 12 months postoperatively (t=-2.890, -2.435, P<0.05). Apex curvature (Kapex) and mean pupil power (MPP) within 4.5mm of central cornea decreased significantly (Z=-2.903, P<0.01; Z=-2.667, P<0.01). Even though the thinnest corneal thickness decreased from pre-operational (461.9±31.1) μm to post-operational (416.6±27.0) μm (Z=-3.059, P<0.01), the cornea became regular with keratometric asymmetry index of anterior corneal surface decreased (Z=-2.667, P<0.01). The corneal optical quality parameters were improved. There was no significant difference in ECD, HEX and CV at 12 months postoperatively (P>0.05). Twelve months after operation, grade 0, 0.5, 1 and 2 haze were seen on 20%, 55%, 20% and 5% corneas respectively. Conclusions: The topography guided excimer laser ablation combined with accelerated corneal collagen cross linking is safe and effective in treatment of early stage keratoconus. It can significantly improve corneal regularity while preventing keratoconus progression, so as to improve the best corrected visual acuity postoperatively. (Chin J Ophthalmol, 2019, 55: 904-910).

Influence of different types of corneal laser refractive surgeries on corneal hysteresis and corneal resistance factor in myopic eyes

Background Refractive surgery has propelled itself forward to become widely performed surgical procedure nowadays.After the surgery, corneal biomechanics decreases lead to keratoconus and corneal ectasia.Doctors pay more attention to biomechanics changes after refractive surgeries. Objective This clinical study was to investigate the influence of different laser refractive surgeries on corneal biomechanics. Methods A prospective nonrandomized and controlled clinical study was designed.One hundred and sixty-four eyes of 82 patients with moderate myopia were enrolled.The patients were divided into sub-Bowman keratomileusis（SBK) group (60 eyes of 30 patients), laser in situ keratomileusis（LASIK) group (54 eyes of 27 patients) and laser subepithelial keratomileusis (LASEK) group（50 eyes of 25 patients), with the matched demography among the three groups.Corneal hysteresis (CH) and corneal resistance factor (CRF) were detected by ocular response analyzer (ORA) before and 1 week, 5 months after refractive surgery.The correlations between stromal ablation depth and postoperative changing values of CH or CRF were analyzed. Results Significant differences were found in CH and CRF at different time points in the three groups (Ftime=41.90, P=0.00; Ftime=49.65, P=0.00), and the CH and CRF values were significantly lower 1 week and 5 months after surgery than those before surgery (all at P=0.00). However, no significant difference of CH or CRF was seen at all time points among the three groups (Fgroup=2.17, P=0.08; Fgroup=2.67, P=0.07). No correlation was found between corneal ablation depth and CH in 1 week and 5 months after surgery (both at R2=0.000), however, weaker correlations were seen between corneal ablation depth and CRF 1 week and 5 months after surgery (Y=3.253+ 0.010X, R2=0.007; Y=1.073+ 0.021 X, R2= 0.004). Conclusions SBK, LASIK and LASEK lead to the change of corneal biomechanics by altering CH and CRF, they play the same influence on cornea.CRF appears to be an useful indicator in evaluating corneal biomechanical changes after laser refractive surgery. Key words: Cornea/physiology; Myopia/surgery; Elastic tissue; Biomechanics; Keratomileusis, laser in situ; Keratomileusis, laser subepithelial; Keratomileusis, sub-Bowman

The Unevenness and Non-orthogonal State of Distribution of Corneal Thickness and the Influence on Correction of Myopic Astigmatism by LASEK

To observe and calculate the unevenness and the non-orthogonal state of distribution of corneal thickness and the relationshipbetween them using Pentacam and to investigate the influence of unevenness and the non-orthogonal state on correction of myopic astigmatism by laser subepithelial keratomileusis (LASEK). 230 eyes with myopic astigmatism treated with LASEK were divided into two groups: 114 eyes as the low astigmatism group (-0.25 to -0.75 DC) and 116 eyes as the midrange-high astigmatism group (-1.00 to -4.50 DC). With the help of the diagram of keratoconus evaluation program of the Pentacam, the D 3.0 and D 6.5 were calculated for the index of distribution of unevenness of the corneal thickness, and the absolute value of the angle between the maximum and minimum progression-index orientation (M 90) for the index of non-orthogonal states. The correction of myopic astigmatism by LASEK was based on standard vector analysis and power vector analysis. The follow-up period was for 3months. The preoperative M 90 was 22.14°±20.87°, D 6.5 was 58.66±21.32μm, and D 3.0 was 16.11±4.28μm for the 230 eyes that were tested. The D 6.5 of low astigmatism group (55.62±20.81)μm was significantly lower than that of midrange-high astigmatism group (61.65±21.48)μm (P<0.05). Of the 230 eyes, the M 90 was positively correlated with D 6.5 (r=0.37, P<0.001), and D 6.5 was positively correlated with D 3.0 (r=0.56, P<0.001). 3months postoperatively, the absolute error vector (|EV|) of low astigmatism group (0.46±0.34) was significantly lower than that of midrange-high astigmatism group (0.53±0.29) (P<0.01). The error of magnitude of low astigmatism group (-0.10±0.31) was significantly lower than that of midrange-high astigmatism group (0.08±0.41) (P<0.001). The absolute error of angle (|EA|)of low astigmatism group (26.10±27.24) was significantly higher than that of midrange-high astigmatism group (9.99±17.32) (P<0.001). The correction ratio of low astigmatism group (1.45±1.21) was significantly higher than that of midrange-high astigmatism group (0.94±0.33) (P<0.01). The error ratio (ER) of low astigmatism group (1.34±1.40) was significantly higher than that of midrange-high astigmatism group (0.42±0.27) (P<0.001). In low astigmatism group, M 90 was positively correlated with |EV| (r=0.30, P<0.001). In midrange-high astigmatism group, M 90 was positively correlated with ER (r=0.31, P<0.001) and D 6.5 was positively correlated with |EV| and B, respectively (r=0.34, 0.33, P<0.001). The relationship between unevenness and non-orthogonal state of distribution of corneal thickness could influence the correction of astigmatism by LASEK. Therefore, more attention should be paid to the correction of midrange-high astigmatism group by excimer surgery.

Higher order aberrations of the corneal surface after laser subepithelial keratomileusis.

PurposeTo evaluate the changes of higher order aberrations (HOAs) before and after laser subepithelial keratomileusis (LASEK) and to analyze the influence of tear film instability on HOAs of the corneal surface after LASEK.MethodsIn this cross-sectional study, 31 patients who underwent LASEK were divided into dry eye (16 patients, 32 eyes) and non-dry eye groups (15 patients, 30 eyes). Uncorrected distance visual acuity, spherical equivalent refraction, ablation depth, tear film parameters and Ocular Surface Disease Index (OSDI) questionnaire scores were evaluated in both groups. Total HOA root mean square (RMS), third-order coma, third-order trefoil and fourth-order spherical aberration (SA) of the corneal surface immediately and at 10 seconds after blinking were measured before and after surgery.ResultsThe total HOA RMS, coma, trefoil and SA significantly increased after LASEK compared with preoperative values in both groups. In the dry eye group, total HOA RMS, coma and trefoil significantly increased except for SA at 10 seconds after blinking compared with those measured immediately after blinking. In addition, the changes of total HOA RMS, coma and trefoil were negatively correlated with tear film break-up time (R = -0.420, -0.473 and -0.439, respectively), but positively correlated with OSDI score (R = 0.433, 0.499 and 0.532, respectively). In the non-dry eye group, there were no significant differences between HOAs measured at 10 seconds after blinking and those measured immediately after blinking.ConclusionsThe HOAs including coma, trefoil and SA significantly increased after LASEK. The tear film instability in the dry eye can be associated with more deterioration of the optical quality after LASEK, due to more significant increase of total HOA RMS, coma and trefoil.

Comparison of LASIK Mode Ablation and PRK Mode Ablation in LASEK Using MEL-80 Excimer Laser

Purpose: We compared laser assisted in situ keratomileusis (LASIK) mode and photorefractive keratectomy (PRK) mode ablation methods in laser subepithelial keratomileusis (LASEK) surgery using the MEL-80 excimer laser. Methods: All patients were followed up for a minimum of 1 year. The PRK mode group consisted of 46 eyes of 23 patients and the LASIK mode group consisted of 97 eyes of 56 patients. The central corneal thickness (CCT), ablation thickness, manifest refractive error and uncorrected visual acuity were compared preoperatively, 1 month and 1 year postoperatively. Spherical equivalent (SE) of cycloplegic refraction at postoperative 1 month and the uncorrected visual acuity (UCVA) ratios of 1.0 or better at postoperative 1 year were compared between the two groups to evaluate clinical efficacy. Results: The SE of refractive error, CCT and target corneal ablation thickness of the two groups were not significantly different preoperatively. The PRK mode group obtained an actual ablation mean thickness of 82.8% of the target and the LASIK mode group obtained an actual ablation mean thickness of 94.1% of the target at postoperative 1 month. In each group, a statistically significant difference was observed between the actual corneal ablation thickness and target corneal ablation thickness. In the PRK mode group, the mean SE of postoperative 1 month cycloplegic refraction was +0.24 ± 0.47 D and in the LASIK mode group, +0.87 ± 0.54 D, indicating a statistically significant difference between the two groups. One year postoperatively, the UCVA ratios of 1.0 or better were 83% in the PRK mode group and 96% in the LASIK mode group, showing a statistically significant difference between the two groups. However, SE of manifest refractive error and CCT in the two groups were not statistically different at postoperative 1 year. Conclusions: The LASIK mode ablation method showed better results than the PRK mode ablation method in postoperative UCVA prognosis after LASEK surgery using the MEL-80 excimer laser. J Korean Ophthalmol Soc 2014;55(11):1625-1630

Corneal topograph-guided laser subepithelial keratomileusis (LASEK) corrects decentered ablation after laser in situ.

Corneal topograph-guided laser subepithelial keratomileusis (LASEK) can effectively correct decentered ablation occurring post laser in situ keratomileusis (LASIK) and to enhance our understanding and diagnosis of decentered ablation following LASIK. Previous studies in the relevant literature are reviewed, and a case report is provided. A patient with high myopia undergoing LASIK in both eyes presented with distorted vision in the left eye, which interfered with the vision in the right eye and caused blurred vision in both eyes. The patient was unable to see objects with both eyes. After receiving corneal topography-guided LASEK, the signs of distorted vision in the left eye and bilateral blurred vision were significantly alleviated, and the patient could see objects with both eyes simultaneously. Clinical ophthalmologists should be aware of the occurrence of decentered ablation after LASIK. Corneal topography-guided LASEK is an efficacious tool for correcting decentered ablation.

Clinical observation of LASEK combined with MMC in the treatment of high myopia

Objective To observe the efficacy and complication of laser subepithelial keratom ileusis (LASEK) combined with mitomycin C (MMC) in treatment of high myopia.Methods 118 cases ( 236 eyes) diagnosed as high myopia were treated by LASEK combined with MMC.The changes of vision,refractive regression,postoperation pain and haze were observed.Results 7-days after operation,all patients' post-operation relief.6-months after operation,the quantity of vision reached or exceeded BCVA were 228 cases ( 96.61％ ),average refraction wsa ( + 0.54 ± 0.24 ) D,the incidence of haze was 4.66％.Conclusion Is safe the LASEK combined with MMC in treatment of high myopia,effective,low incidence of haze. Key words: Myopia; LASEK ; MMC

Reasearch progress in posterior corneal surface anterior protrusion after the excimer laser corneal refractive surgery

With the mature of techniques and development of equipments in excimer laser corneal refractive surgery,the postoperative complications are decreasing gradually.As the center of cornea become thin after laser in situ keratomileusis (LASIK) and laser subepithelial keratomileusis ( LASEK ),the strength of cornea and the intraocular pressure relatively step down,which can cause cornea anterior protrusion more or less.Because the posterior surface which is not directly affected by surgical process and healing process,so it is usually used to evaluate the protrusion of cornea.As the application of.ophthalmic anterior segment imaging and analysis system,we can get more message of cornea posterior surface.The manifestation,principle and precautionary measures of corneal posterior surface anterior protrusion after the excimer laser corneal refractive surgery were reviewed. Key words: Excimer laser; Myopia; Posterior corneal surface; Anterior protrusion

Satisfaction Level of Physicians Who Have Undergone Corneal Refractive Surgery

PurposeTo evaluate the levels of satisfaction among physicians who have undergone corneal refractive surgery.MethodsThis study included 212 eyes of 107 consecutive patients who underwent laser in situ keratomileusis or laser sub-epithelial keratomileusis surgery. Patients were divided into two groups: one group of physicians and one group of other healthcare workers (HCWs). The physicians' group was also subdivided into two different groups: surgeons or doctors using microscopes and medical physicians. The main outcome measures were scale scores obtained by using the Visual Function Index-14 questionnaires; uncorrected distance visual acuity (UDVA), residual spherical equivalent (SE), optical zone diameter, and residual corneal thickness were also compared between the groups.ResultsNo significant differences in preoperative parameters, with the exception of the ratio of types of refractive surgery, were noted between the physicians and the HCWs group. Additionally, no differences between the groups were noted in the postoperative UDVA, residual SE, optical zone diameter, residual corneal thickness, and level of satisfaction. When comparing the two subgroups of physicians, the differences in satisfaction rates were not statistically significant, even in terms of the performance of delicate manual work.ConclusionsNo statistically significant differences in the clinical outcomes and satisfaction scores were detected after surgery between the physicians and HCWs groups, nor were any significant differences detected between the surgeons and medical physicians groups. Corneal refractive surgery can conceivably be recommended even for physicians who perform intensive near vision-dependent activities and delicate operations.

Long-term effect of LASEK for the treatment of low to moderate myopia with thin cornea

Objective To evaluate the long term effect and safety of laser subepithelial keratomileusis( LASEK)for the treatment of low to moderate myopia with thin cornea( central corneal thickness ＜ 500 μm) Methods To analyze patients with low to moderate myopia in 5 -7 years after LASEK,and compare the refraction,visual acuity,contrast sensitivity,glare contrast sensitivity,corneal endothelium and corneal topography between pateints with thin cornea and normal thickness cornea.Results Thin cornea group had 27 cases (52 eyes).Normal thickness cornea group had 31 cases (62 eyes).No keratoconus had been observed during the follow-up period in the two groups.The corrected visual acuity of both groups were ≥1.0 ;In the thin cornea group,49 eyes' uncorrected visued acuity were ≥ 1.0,and 3 eyes were ＜ 1.0.In the normal cornea group,58 eyes' uncorreeted visued acuity were ≥ 1.0,and 4 eyes were ＜ 1.0 (x2 ＝ 0.0228,P ＞ 0.05).In the thin cornea group,49 eyes had 0 degree of cornea Haze,and 3 eyes had 0.5 degrees of cornea Haze.On the other hand,in the normal thickness cornea group,60 eyes had 0 degree of cornea Haze,and 2 eyes had 0.5 degrees of cornea Haze(x2 =0.4416,P ＞ 0.05 ).The shapes of the corneal endothelium of bothgroups were quite consistent and appear to be hexagonal,and the cell edge was neat.The average endothelial cell density:(2330±294)/mm2 in the thin cornea group,and (2413 ±320)/mm2 in the normal corneal thickness group; The average endothelial cell area:(420 ± 78 )μm2 in the thin cornea group,and (447 ± 92 ) μm2 ( t =1.6875,P ＞ 0.05 ) in the normal thickness cornea group.The contrast sensitivity of two groups with or without glare condition had significant difference for every spatial frequencies (P ＞ 0.05 ).Conclusion LASEK for the treatment of low to moderate myopia with thin cornea is tested to be safe,stable and with no keratoconus. Key words: Laser subepithelial keratomileusis; Corneal thickness; Keratoconus

A clinical observation of applying mitomycin C in LASEK surgery to prevent the formation of subepithelial corneal haze in patients with high myopia

Objective To observe the applying of mitomycin C in LASEK surgery to prevent the formation of subepithelial corneal haze in patients with high myopia.Methods Sixty patients ( 120 eyes) with high myopia were randomly performed LASEK on one eye,and they were performed 0.02％ mitomycin C treatment during LASEK on the other eye separately.Regular follow-up of 6 month was done to observe the haze formation.Results In the LASEK group,the rate of the haze of grade 0.5 was 58.33％,48.33％,40.00％ in 1 month,3 months and 6 months,that of grade 1 was 13.33％,8.33％,5.00％,that of grade 2 was 0,1.67％,1.67％,that of grade 3 and 4 was 0.In the LASEK + MMC group,the rate of the haze of grade 0.5 was 36.67％,26.67％,13.33％ in 1 mouths,3 months and 6 months respectively,that of grade 1 was 1.67％,1.67％,3.33％,that of grade 2,3 and 4 was 0.There was significant difference (P＜0.05) in the haze between the two groups.Conclusion The occurrence of the haze in the LASEK + MMCgroup is milder than that in the LASEK group. Key words: Laser subepithelial keratomileusis; Mitomycin C ; Haze

The complications of laser subepithelial keratomileusis for unusual myopic eyes

Objecive To analyze the complications of laser subepithelial keratomileusis(LASEK) for unusual myopic eyes,and to investigate the causes and discuss the prevention of these complications.Methods The unusual myopic eye was characterized as small globe,blepharophimesis,deep socket of eyeball or thin cornea.LASEK was done to correct high and medium myopia(-5.00 D～-13.00D) on 611 eyes in 312 cases.They were followed up for a period of 12 months.The epithelium,haze,visual acuity and complications were observed. Results Intraoperative incompletely corneal epithelial flap occurred in 72 eyes(11.7%),delayed postoperative corneal epithelial healing in 21 eye(3.4%),corneal infecion in 1 eye(0.15%).Six months after operation,corneal haze was 0.5 degree in 56 eyes(9.1%),degree 1 in 14 eyes(2.3%)and over 2 degree in 2 eyes(0.3%).Postoperative steroid high intraocular pressure occurred in 7 eyes(1.1%).Twelve months after operation,there was refractive regression>1.00D in 51 eyes (8.3%),the increase in astigmatism>1.00D in 19 eyes(3.1%),the best corrected visual acuity decreased 1 line in 9 eyes(1.4%).Conclusion LASEK is a safe and effective method for correcting unusual myopic eyes.Yet attention should be paid on the complications during and after operation.With the improvement in operative technique and reasonable drug and with the cooperation of the patients after operation,those complications can be decreased. Key words: laser subepithelial keratomileusis; unusual myopic eyes; cornea; complication

Second operation after laser in situ keratomileusis

To compare clinical results between the laser in situ keratomileusis (LASIK) surgery and the laser subepithelial keratomileusis (LASEK) surgery as the second operation after an unsuccessful LASIK surgery. Thirty one patients (62 eyes) with refractive regression or under-correction after LASIK operation received the second surgery. Thirty eyes received LASIK surgery (group A) and 32 eyes received LASEK surgery (group B). The follow-up period was one year. The main parameters included visual acuity, refraction, corneal curvature, and the total value of high-aberration. The difference in visual acuity in one week postoperation between both group was statistically significant (t = 5.21, P < 0.01), the acuity of LASEK group (0.57 ± 0.11) was obviously lower LASIK group (0.79 ± 0.21). There is no difference in acuity between both group in 1 month and 1 year postop. The difference in uncorrected visual acuity, average spherical equivalent refractive degree, average corneal curvature, and the total value of high-aberration between both group 1 year after operation was statistically not significant. Uncorrected visual acuity (A group 0.84 ± 0.15, B group 0.82 ± 0.11, t = 0.60), average spherical equivalent refractive degree (A group -0.34 ± 1.15, B group -0.32 ± 1.13, t = -0.07), average corneal curvature (A group 37.87 ± 1.95, B group 38.47 ± 2.15, t = -1.15), the total value of high-aberration (A group 0.45 ± 0.11, B group 0.48 ± 0.13, t = -0.98). One patient developed epithelium ingrowth after LASIK surgery. One patient suffered from 2+ haze after LASEK surgery. Both LASIK and LASEK surgery can obtain satisfactory therapeutic results after an unsuccessful LASIK surgery.

Analysis of the Reasons for not Undergoing LASEK

Objective To explore the specific reasons why patients did not undergo LASEK (Laser Subepithelial Keratomileusis) after they hsad got preoperative examinations. Methods The reasons why 78 cases of patients with preoperative examination as well as pre-operative's talks did not undergo LASEK were analyzed. Results Of these 78 cases were 16 patients with corneal refractive power of high (20.51%); 2 cases of keratoconus (2.56%); Best-corrected visual acuity<0.5 in 22 eyes of 13 cases (16.67%); 12 patients (15.38%) had some apprehension zbout the surgery; 10 patients (12.82%) suffered from ocular fundus diseases and the corneal thickness of 8 patients (10.26%) was insufficient; 7 patients (8.97%) had high intraocular pressure; 6 cases (7.69%) full of fear of pain and 4 cases (5.13%) had instable degree of visual acuity. Conclusion LASEK is a selective operation. The need for strict preoperative examination and communication with patients is necessary and the indications for surgery and contraindications must be stirctly mastered. Key words: Laser Subepithelial Keratomileusis (LASEK); Myopia; Indications

Ring Keratitis Associated With Topical Abuse of a Dilute Anesthetic After Refractive Surgery

Anesthetic toxic keratitis is rare and presents as a ring keratitis, which is often misdiagnosed as Acanthamoeba keratitis. Here, we report an unusual case of toxic keratitis caused by topical abuse of a dilute anesthetic. A 26-year-old woman presented with bilateral corneal edema, ring infiltrates, pigmented keratic precipitate, Descemets membrane folding, and strong anterior chamber reactions 2 weeks after laser subepithelial keratomileusis surgery. Tracing back her medical history, topical dilute 0.1% proparacaine was prescribed and frequently used for 1 month. Toxic keratitis was suspected. After discontinuation of the topical anesthetic and initiation of treatment with topical 20% autologous serum, complete corneal epithelialization was achieved within 1 week. Corneal infiltrates and anterior chamber reaction gradually subsided. Vision improved from finger counting to 20/20 in the right eye and 20/25 in the left eye, but confocal microscopy showed decreased corneal endothelial cells. Topical abuse of a dilute topical anesthetic can cause severe toxic keratitis and endothelial cell loss. The physician must be aware of the signs of topical anesthetic abuse and should not prescribe even a dilute anesthetic for long-term use. Autologous serum can help in the recovery of toxic keratitis.

Epithelial-flap abnormality of LASEK

目的 分析准分子激光上皮瓣下角膜磨镶术(LASEK)的角膜上皮瓣异常的类型、产生原因、预防及处理方法.方法 观察行LASEK的161例(320眼)近视术中术后的角膜上皮瓣异常情况,分析其原因,并观察术后视力、角膜刺激症状及上皮下雾状浑浊.结果 21眼术中出现上皮瓣异常,包括上皮瓣不完整、瓣撕离破碎、瓣游离.10眼术后出现上皮瓣异常,包括瓣皱褶、接触镜脱落、上皮瓣脱落及局部上皮延迟愈合.结论 LASEK是一种安全有效的屈光手术,但完好的角膜上皮瓣是LASEK优越性的基础.熟练掌握手术技巧,保持术中术后上皮瓣的完整,预防及正确处理各种上皮瓣异常,是LASEK成功的关键所在。

Bioptics mit Multifokallinsen und Lasek

Good functional results with multifocal lenses need exact postoperative emmetropia. Therefore, it seems reasonable to perform additional refractive surgery to correct minimal spherical or cylindrical postoperative ametropia (bioptics). But concerns could arise about additional photoptic phenomena or loss of contrast. The literature contains only a few reports about bioptics after multifocal lens implantation. In eight eyes of seven patients, laser subepithelial keratomileusis (Lasek) was done after multifocal lens implantation. Pre-Lasek and 6 months postoperatively, we performed the following examinations in addition to visual acuity: contrast sensitivity (Pelli-Robson charts), low-contrast visual acuity (Humphrey AR 570), glare visual acuity (Humphrey AR 570), and night-driving ability (Mesoptometer II, Oculus). Preoperative contrast sensitivity was 1.2-1.65; postoperatively it was 1.35-1.65. Low-contrast visual acuity measured 50-70% preoperatively and 57-70% postoperatively. Glare visual acuity measured 12.5-50% preoperatively and 28.5-57% postoperatively. Mesoptometer measurements did not change after Lasek; they revealed night-driving ability under strict criteria for four patients. Bioptics as a combination of multifocal lens implantation and Lasek does not cause a functional decline in low-contrast or glare visual acuity, but it minimizes postoperative ametropia. It seems superior to exclusive multifocal lens implantation.

Corneal Opacity Caused by LASEK with Improper High-concentrated Mitomycin-C

Purpose: To report a case of corneal opacity with postoperative changes of topographic features and visual acuity after laser subepithelial keratomileusis (LASEK) treated with an improper concentration of mitomycin-C. Case summary: A 25-year-old female patient who experienced corneal opacity after LASEK treated with mitomycin-C was evaluated for changes in corneal opacity by photography, central corneal power by Orb scan Ⅱz, and best corrected visual acuity (BCVA) over the period of 1 year. The corneal epithelial defect was completely healed 2 weeks after the LASEK operation. Subepithelial and stromal opacity decreased over time, but her cornea did not return to normal. BCVA was 20/25 in the right eye and 20/20 in the left eye at postoperative 1 year, but stromal opacity remained. Conclusions: An improper concentration of mitomycin-C during LASEK could result in corneal opacity. Long time is needed to recover visual acuity and a normal corneal structure.