Research progress of epithelial ingrowth under corneal flap after keratorefractive surgery / 国际眼科杂志(Guoji Yanke Zazhi)

@#The epithelial ingrowth under corneal flap is one of the complications after keratorefractive surgery, of which the incidence has declined dramatically with the improvement of relevant facilities and surgical techniques. However, epithelial ingrowth results from traumatic flap displacement has been describing in the literatures from time to time. If the prompt and efficient treatment cannot be taken, the severe complications of epithelial ingrowth will occur such as the alternation of refraction and cornea keratolysis. In this article, we reviewed the research progress of epithelial ingrowth after keratorefractive surgery.

Relationship between the offset of a laser-assisted flap using the WaveLight FS200 femtosecond laser and the clinical results / 中华实验眼科杂志

Objective@#To evaluate the relationship between the offset of a laser-assisted flap using the WaveLight FS200 femtosecond laser and the clinical results after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).@*Methods@#In this prospective cohort study, 125 patients who underwent FS-LASIK for myopia by WaveLight FS200 femtosecond laser from June 2017 to July 2018 at the Tungwah Ophthalmic Center were divided into two groups according to the offset of the corneal flap from the pupil center: the no-offset group (57 eyes) and the certain-offset group (68 eyes); the baseline data, including age, sex, uncorrected visual acuity(UCVA), spherical degree, and central corneal thickness were matched in the two groups.UCVA, residual astigmatism, spherical degree, corneal curvature and aberration were observed 1 week and 1 month after surgery.The study protocol was approved by the Ethics Committee of Tungwah Hospital of Sun Yat-Sen University (No.2017DHLL004). Written informed consent was obtained from each subject prior to entering the study cohort.@*Results@#UCVA, corneal curvature, spherical degree, spherical and corneal aberration between the two groups were not significantly different (all at P>0.05). One week after surgery, the residual astigmatism was ≤-0.50 D in 50 eyes (87.7%, 50/57)and >-0.50 D in 7 eyes (12.3%, 7/57) in the no-offset group; the residual astigmatism was ≤-0.50 D in 50 eyes (73.5%, 50/68) and >-0.50 D in 18 eyes (26.5%, 18/68) in the no-offset group.The residual astigmatism between the two groups 1 week after surgery was significantly different (χ2=3.902, P=0.048), and there was no significant difference in residual astigmatism 1 month after surgery (χ2=2.031, P=0.068). The trefoil of the no-offset group was statistically less than of the certain-offset group at 1 week and 1 month after surgery (0.05[0.04, 0.08]vs.0.06[0.04, 0.10]; 0.05[0.03, 0.07]vs.0.06[0.05, 0.09])(Z=-2.245, P=0.022; Z=-2.370, P=0.018). The spherical aberration and coma were not significantly different between the two groups at 1 week and 1 month after surgery (both at P>0.05).@*Conclusions@#The offset from femtosecond laser-assisted flap by WaveLight FS200 has no effect on long-term visual acuity or residual astigmatism.Some patients may have different visual experiences because of the residual astigmatism and higher order aberration during the early postoperative stage.

Comparison of refractive outcomes of femtosecond LASIK with two different flap thickness in the correction of myopia / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To compare the refractive outcomes of femtosecond LASIK with two different flap thickness in the correction of myopia.<p>METHODS: A total of 236 eyes of 118 myopic patients received LASIK with Wave-Light exeimer laser system. In the non-high myopia group, 30 people(60 eyes)used 90 micron corneal flaps, the other(60 eyes)used 110 micron corneal flaps; in the high myopia group,29 people(58 eyes)used 90 micron corneal flaps,the other(58 eyes)used 110 micron corneal flaps. Uncorrected distance visual acuity(UDVA), corrected distance visual acuity(CDVA), manifest refraction and intraocular pressure before operation, at 1mo, 3mo postoperatively were evaluated.<p>RESULTS: The percent of postoperative UDVA better than or equal to preoperative CDVA after 3mo: 57 eyes(95%). In the non-high myopia group no matter 90 micron corneal flaps or 110 micron corneal flaps. In the high myopia group, there are 53 eyes(91.4%)with 90 micron corneal flaps and 56 eyes(96.6%)with 110 micron corneal flaps(<i>P</i>=0.438); The percent of spherical equivalent refraction(SE)within ±0.50D of the target refraction change: 51 eyes(85%). In the non-high myopia group no matter 90 micron corneal flaps or 110 micron corneal flaps, 48 eyes(82.8%). In the high myopia group with 90 micron corneal flaps or 110 micron corneal flaps; The percent of change in SE within 0.50D between 1mo and 3mo postoperatively: there are 57 eyes(95%)with 90 micron corneal flaps and 55 eyes(91.7%)with 110 micron corneal flapsin the non-high myopia group(<i>P</i>=0.717). In the high myopia group, there are 44 eyes(75.9%)with 90 micron corneal flaps and 50 eyes(86.2%)with 110 micron corneal(<i>P</i>=0.464). <p>CONCLUSION: Both 90 micron corneal flaps and 110 micron corneal flaps show similar good efficacy, predictability and stability in the correction of myopia.

Numerical Simulation for the Safe Retention Value of Residual Stromal Bed Thickness in Laser-Assisted in situ Keratomileusis / 医用生物力学

Objective To study the effects of different residual stromal bed thickness (RSBT) in laser-assisted in situ keratomileusis (LASIK) surgery on geometric deformation and stress changes of the cornea under different intraocular pressures (IOP), and evaluate safety of the three retention values (250, 280, 300 μm). Methods The models of normal cornea and corneas with different RSBT after surgery were established by the finite element software ABAQUS. Appropriate loading and boundary conditions were set and then the corresponding displacement and stress were calculated. Results The apical displacement of the postoperative cornea (RSBT=250 μm) under IOP=2.66 kPa was basically the same as that of the normal cornea (RSBT=550 μm) under IOP=5.32 kPa. RSBT=280 μm was in the low risk area of keratoconus, while RSBT=250 μm was in the high-risk area. At a value between 280 μm and 300 μm of RSBT, the stress distribution was nearly consistent with that of the normal cornea. With RSBT=300 μm, the stromal layer of the cornea lost 40% of the strongest strength against tissue tension. Conclusions RSBT=250 μm is the minimum retention value for LASIK surgery. RSBT=250 μm is the high risk value. With RSBT=330-340 μm, LASIK surgery is safe enough for most patients.

Relationship between the offset of a laser-assisted flap using the WaveLight FS200 femtosecond laser and the clinical results / 中华实验眼科杂志

Objective To evaluate the relationship between the offset of a laser-assisted flap using the WaveLight FS200 femtosecond laser and the clinical results after femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK).Methods In this prospective cohort study,125 patients who underwent FS-LASIK for myopia by WaveLight FS200 femtosecond laser from June 2017 to July 2018 at the Tungwah Ophthalmic Center were divided into two groups according to the offset of the corneal flap from the pupil center:the no-offset group (57 eyes) and the certain-offset group (68 eyes);the baseline data,including age,sex,uncorrected visual acuity (UCVA),spherical degree,and central corneal thickness were matched in the two groups.UCVA,residual astigmatism,spherical degree,corneal curvature and aberration were observed 1 week and 1 month after surgery.The study protocol was approved by the Ethics Committee of Tungwah Hospital of Sun Yat-Sen University (No.2017DHLL004).Written informed consent was obtained from each subject prior to entering the study cohort.Results UCVA,corneal curvature,spherical degree,spherical and corneal aberration between the two groups were not significantly different (all at P＞0.05).One week after surgery,the residual astigmatism was ≤-0.50 D in 50 eyes (87.7％,50/57) and ＞ -0.50 D in 7 eyes (12.3％,7/57) in the no-offset group;the residual astigmatism was ≤-0.50 D in 50 eyes (73.5％,50/68) and ＞-0.50 D in 18 eyes (26.5％,18/68) in the no-offset group.The residual astigmatism between the two groups 1 week after surgery was significantly different (x2 =3.902,P =0.048),and there was no significant difference in residual astigmatism 1 month after surgery (x2 =2.031,P =0.068).The trefoil of the no-offset group was statistically less than of the certain-offset group at 1 week and 1 month after surgery (0.05 [0.04,0.08] vs.0.06[0.04,0.10];0.05[0.03,0.07] vs.0.06[0.05,0.09]) (Z=-2.245,P--0.022;Z=-2.370,P=0.018).The spherical aberration and coma were not significantly different between the two groups at 1 week and 1 month after surgery (both at P＞0.05).Conclusions The offset from femtosecond laser-assisted flap by WaveLight FS200 has no effect on long-term visual acuity or residual astigmatism.Some patients may have different visual experiences because of the residual astigmatism and higher order aberration during the early postoperative stage.

Effect of femtosecond laser and mechanical lamellar LASIK on the stability of corneal flap thickness / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To explore the effects of femtosecond laser and mechanical lamellar blade excision laser <i>in situ</i> keratomileusis(LASIK)on corneal flap thickness stability and dry eye syndrome.<p>METHODS: Retrospective analysis of 80 patients with myopia who underwent LASIK in our hospital. According to different methods of flapping, it is divided into femtosecond laser group and mechanical laminating knife group. The flap thickness of the two groups of patients at different time points(1h, 1d, 1wk, 1mo, 3mo)were measured. The differences in corneal apex 1, 2, 3mm and corneal apex flap thickness in different directions were compared. The incidence of dry eye syndrome was compared between 1 and 3mo, 1a, 2a after surgery.<p>RESULTS: The apex thickness of the corneal flap of the femtosecond laser group is 99.62±4.50μm, and the thickness of the apex of the mechanical lamellar knife group is 125.25±12.81μm.The thickness of the corneal flap at different centrifugal points of the femtosecond laser flap is relatively uniform, while the thickness of the corneal flap of the mechanical lamellar knife varies greatly. The OSDI scores of the mechanical lamellar group were higher than those of the femtosecond laser group at 1, 3, 1, and 2a postoperatively(<i>P</i><0.01). At 2a of follow-up, the incidence of dry eye in the femtosecond laser group was lower than that in the mechanical lamellar group(χ²=4.692, <i>P</i>=0.030). At 1 and 2a postoperatively, the proportion of mild dry eye in the femtosecond laser group was higher than that in the mechanical lamellar group(<i>P</i>=0.044, 0.001).<p>CONCLUSION: Compared with the mechanical lamellar scalpel, the corneal flap thickness of patients with femtosecond laser LASIK is better, more uniform and less error. And the incidence of dry eye after surgery is lower, with mild dry eyes.

Influenceofmicrokeratomeand femtosecond laser on vision and corneal flap thickness used in corneal flap making / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To study and compare the influence situation of corneal flap made by microkeratome and femtosecond laser for the vision and corneal flap thickness in patients. METHODS:Totally 120 patients(240 eyes) with myopic refractive surgery in our hospital from June 2014 to May 2015 were randomly divided into Group A (microkeratome group) with 60 cases (120 eyes) and Group B (femtosecond laser group) with 60 cases (120 eyes). Then the vision situation and corneal flap thickness indexes of two groups at different time after the treatment were compared. RESULTS:The vision situation between the two groups at different time after the treatment all had no significant differences (all P>0.05),while the corneal flap thickness related indexes of Group B at different time after the treatment were all better than those of Group A (all P<0 05). The evaluation indexes of two groups after the treatment all had significant differences (all P<0.05). CONCLUSION: The indexes of corneal flap made by femtosecond laser are better than those of microkeratome,and the influence of two methods for the vision is no obvious.

Effects of LASIK on ocular surface by femtosecond laser or mechanical microkeratome for creating corneal flap / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM:To investigate the effects of laser <i>in situ</i> keratomileusis(LASIK)on ocular surface by femtosecond laser or mechanical microkeratome for creating corneal flap, and to study the effect of different corneal flap method on ocular surface after operation. <p>METHODS: This study included 218 cases(436 eyes)myopia patients from January 2016 to January 2017 in our hospital for refractive surgery, their medical records were retrospectively analyzed. They all underwent LASIK surgery treatment and complained of different degree of dry eye postoperatively, foreign body sensation and discomfort. Mechanical microkeratome was used in 61 cases(122 eyes)of patients and they were as control group, with femtosecond laser, 157 cases(314 eyes)were set as observation group. We compared dry eye symptom scores, corneal fluorescein staining(FL)score, break-up time(BUT)and basic tear secretion test(SⅠt)between the two groups preoperatively and postoperatively 1wk, 1, and 3mo. <p>RESULTS: Before surgery, dry eye symptoms scoring of two groups had no statistically significant difference(<i>P</i>>0.05); the scores of the two groups were significantly different before and after surgery(<i>P</i><0.05); postoperatively 1wk, dry eye symptoms score of control group was greater than that of the observation group with significant difference(<i>P</i><0.05), the sores at 1 and 3mo after surgery were not different between the two groups(<i>P</i>>0.05). There was no significant differenc on the preoperative BUT between the two groups(<i>P</i>>0.05). BUT before and after surgery was significantly different of both groups(<i>P</i><0.05). BUT of control group was significantly lower than that of observation group postoperatively(<i>P</i><0.05). Before surgery, FL score of two groups had no statistically significant difference(<i>P</i>>0.05); the scores of the two groups were significantly different before and after surgery(<i>P</i><0.05); postoperatively 1wk and 1mo, FL score of control group was greater than that of the observation group with significant difference(<i>P</i><0.05), the sores at 3mo after surgery were not different between the two groups(<i>P</i>>0.05). Before surgery, SⅠt of two groups had no statistically significant difference(<i>P</i>>0.05); the scores of the two groups were significantly different before and after surgery(<i>P</i><0.05); postoperatively 1wk and 1mo, SⅠt of control group was lower than that of the observation group with significant difference(<i>P</i><0.05); SⅠt at 3mo after surgery were not different between the two groups(<i>P</i>>0.05). Two groups of patients had no serious postoperative complications occurred.<p>CONCLUSION: Compared with the mechanical microkeratome for creating corneal flap, LASIK with femtosecond laser for creating corneal flap has less effect on ocular surface and has mild symptoms of dry eye, the effect time is also shortened.

Effect of LASIK using Ziemer LDV Z6 femtosecond laser for creating corneal flaps / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To evaluate the clinical effects of femto-LASIK using new Ziemer LDV Z6 femtosecond laser machine (Z6). METHODS: Two - hundred cases ( 400 eyes ) was randomly separated into two groups: Group A included 200 eyes which corneal flaps were made by Z6, and Group B included rest of 200 eyes which corneal flaps were examined by a traditional Ziemer LDV CrystalLine femtosecond laser machine (CrystalLine). Visual acuity, slit lamp, refraction, Sim-K average, intraocular pressure (IOP), non-invasive tear break-up time (NIAvg-BUT), operation difficulty and complications were compared between two groups preoperatively and postoperatively.RESULTS:There was no significant differences between two groups in visual acuity, refraction, Sim-K average, IOP and NIAvg - BUT either preoperatively or 6mo postoperatively (P>0. 05). Although there were significant differences in operation difficulty and complications were found between two groups ( P CONCLUSION:More careful and strict requirements are needed when using the new Z6 femtosecond laser for corneal flaps.

Effect of related factors on the stability of posterior corneal surface after LASIK / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To discuss the related factors that affected the stability of posterior corneal surface after laser in situ keratomileusis ( LASIK) . METHODS:About 64 patients (64 eyes) were enrolled. The correlation among the changes in posterior corneal surface 6 month after LASIK, surgery method, corneal flap thickness ( FT ) , ablation thickness ( AT ) , postoperative residual corneal stroma thickness ( RCST ) , preoperative thinnest corneal thickness ( CT ) , flap thickness/preoperative thinnest corneal thickness ( FT/CT ) , ablation thickness/preoperative thinnest corneal thickness ( AT/CT) , postoperative residual corneal stroma thickness/preoperative thinnest corneal thickness ( RCST/CT) , anterior and posterior preoperative corneal height, the difference of the forward shift in posterior corneal surface ( diff value ) of preoperative and preoperative intraocular pressure were analyzed. RESULTS: The changes of diff value between preoperative and postoperative were related with diopter (r=0.419, P=0.014), AT (r=0.394, P=0.023), AT/CT (r=0.501, P=0.004), Diff value of preoperative (r=0.501, P=0. 004), RCST (r=-0. 385, P=0. 033) and RCST/CT (r=-0. 401, P=0. 025). The changes of height value from posterior corneal surface between preoperative and postoperative were related with diopter (r=0. 520, P=0. 002), AT (r=0.504, P=0. 003), AT/CT (r=0. 442, P=0. 013), Diff value of preoperative (r=0. 624, P=0. 000) and RCST/CT (r=-0. 394, P=0. 028). CONCLUSION: AT, RCST, AT/CT, RCST/CT and diff value of preoperative should be the key index that predicted the stability of posterior corneal surface after LASIK,the further research will give the range of safety value.

Immediately observation on post-LASIK corneal flap / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To immediately observe the complication of corneal flap after LASIK surgery. METHODS:A retrospective case series were studies. Totally 2 040 cases ( 4 080 eyes ) from January 2010 to October 2012 in our hospital were collected, the corneal flap was observed using lamp microscope after LASIK within 30min. Corneal flap dislocation, corneal flap strial and intraface debris were examined after operation, the effective treatment and controlled measure should be taken for these complications. RESULTS: Postoperative complications were corneal flap dislocation 102 eyes (2. 5%), corneal flapstriae 95 eyes (2. 33%), interface debris 105 eyes (2.57%). No failure case was seen. There had no corneal flap-related complications, which seriously impact the visual quality after the surgery. CONCLUSION: Carefully postoperative examination at the first - time is an effective way to manage some complications of post - LASIK. Thus promoting the diagnosis and treatment of post-LASIK complications.

Queratitis lamelar difusa después de un corte incompleto / Diffuse lamellar keratitis after incomplete corneal flap cut

La queratitis lamelar difusa es una inflamación estéril de la interfase lamelar que suele presentarse 24 horas después de la realización de la queratomileusis in situ asistida con láser y potencialmente puede comprometer la agudeza visual final. Se presenta un paciente de 25 años de edad con antecedentes de cirugía refractiva corneal mediante queratomileusis in situ con láser en el ojo derecho, que tuvo como complicación durante el acto quirúrgico un corte incompleto. En el posoperatorio inmediato se le diagnosticó una queratitis lamelar difusa. Se aplicó tratamiento local y se obtuvo la recuperación visual total del paciente con estabilidad del defecto refractivo. Esto permite posteriormente realizarle la corrección mediante cirugía refractiva de superficie

The diffuse lamellar keratitis is a sterile swelling of the lamellar interface which arises generally 24 hours after laser in situ keratomileusis and might affect the final visual acuity. A 25 years- old patient with history of corneal refractive surgery by laser in situ keratomileusis on his right eye was reported. He suffered from an incomplete corneal flap cut as complication during the surgical procedure, and a diffuse lamellar keratitis was detected at the immediate postsurgical visit. Total visual recovery and the refractive defect stability were attained through local treatment. This allows further correcting the defect by means of a surface refractive surgery in the future

Comparative observation of confocal microscopy between femtosecond laser LASIK and hansatome microkeratome LASIK / 中华实验眼科杂志

Background The surgery for femtosecond laser created laser in situ keratomileusis(LASIK)flaps has made great progression recent year,but the postoperative corneal wound healing and regeneration of nerve fibers after surgery are closely concerned.Objective This study was to compare and analyze the clinical outcomes between FEMTO LDV femtosecond laser flap and mechanical microkeratome Hansatome flap in LASIK.Methods A prospective case-controlled study was designed.The serial 38 myopic eyes of 38 patients were included from March through July,2010 in Henan Armed Police Force General Hospital.The patients were randomized into FEMTO LDV femtosecond laser assisted flap group(20 patients/20 eyes)and mechanical microkeratome Hansatome assisted flap group(18 patients/18 eyes)with the matched age,gender and refraction of spherical equivalent.HRT Ⅲ examinations were performed before surgery,1 week,1 month and 3 months after surgery to compare the morphological changes atthe center and margin of the flaps,and evaluate the similarities and differences of cellular morphology after surgery between the two approaches.Written informed consent was obtained from each patient prior to this medical trial.Results The best corrected visual acuity was ≥ 1.0 and the refract diopter was similar in both groups(+0.21 D±0.48 D and-0.04 D±0.54 D)1 month after LASIK.The corneal thickness was insignificant increased in the first week after LASIK,and the density of shallow stromal cells was decreased in 1 week,1 month and 3 months compared with pre-operation in the femtosecond laser assisted flap group(t =-27.99,-25.49,-28.87,P ＜ 0.01).In the Hansatome assisted flap group,significantly thickened corneal epithelium was seen in the first week after LASIK compared before LASIK(56.73 μm±2.47 μm versus 51.16 μm±1.11 μm)(t=9.29,P＜0.05),and the density of shallow stromal cells was decreased in 1 week,1 month and 3 months compared with pre-operation in the Hansatome assisted flap group(t =-17.57,-14.13,-19.63,P =0.00).The density of high reflective interface particles in cornea was lower in 1 week,1 month and 3 months after LASIK in the femtosecond laser assisted flap group than that in the Hansatome assisted flap group,showing significant differences between them(t =-13.505,-11.900,-14.084,P＜0.01).The active stromal cells were seen beneath the interface in both groups in the first week and gradually decreased after that time.Intact corneal nerve fibers were found in the femtosecond laser assisted flap group,but those in the Hansatome assisted flap group were shorter and smaller 3 months after LASIK.At 3 months after surgery,the flap margin showed stromal higher reflection and irregular secondary fibrosis in the femtosecond laser assisted flap group,and in contrast,the flap margin had the appearance of a unclearly identified fibrotic scar in the Hansatome assisted flap group.Conclusions Compared with the LASIK and Hansatome assisted flap,the LASIK with FEMTO LDV flap shows earlier nerve fiber regeneration and greater fibrotic scarring,which imply a good wound healing process in the LASIK with FEMTO LDV flap.

Meta analysis of randomized controlled clinical trial in the effect of hinge location on dry eye syndrome after LASIK / 中华实验眼科杂志

Background Dry eye syndrome is a frequent postoperative complication of laser in situ keratomileusis (LASIK).Some studies reported that the hinge location of corneal flap has influence on dry eye syndrome following LASIK,but others showed inverse views.Objective This systematic review was to evaluate and compare the effects of a superior-and nasal/temporal-hinge location on dry eye syndrome after LASIK.Methods A systematic literature retrieval was conducted in the Medline,Embase,Cochrane Library and CNKI from 1990 to 2011 according to designed searching strategy and relevant words.Published randomized-controlled clinical trial (RCT) data of the effect of superior-and nasal/temporal-hinge location on dry eye syndrome were extracted by two researchers separately.The outcome parameters,such as tear film breakup time (BUT),Schirmer Ⅰ test and corneal sensation were analyzed 1 week,3 months and 6-12 months postoperatively.The statistical analysis was performed using a RevMan 5.0 software and the quality of included literatures were graded according to the Jadad scale.Fixedeffect model was used for the inhomogeneity multiple studies (P≥0.1,homogeneity test I2 ＜50％),and random-effect model was used for the homogeneity studies.Results Ten pieces RCT papers were searched and 3 of them were rejected because of the lack of outcome data.In 7 included studies,652 eyes of 331 patients were involved in the Meta analysis,with the Jadad scores ≥ 3.BUT assessment was performed in 5 trials (530 eyes),Schirmer Ⅰ test evaluation was in 7 trials (652 eyes) and corneal sensation observation was in 4 trials (320 eyes),without significant homogeneity among the relevant literature(I2＜50％).Meta analysis revealed that BUT in the eyes with superior-hinge group was obvious shorter than that in the eyes nasal/temporal-hinge group at 1 week (WMD =-0.42,95％ CI:-0.79 to-0.06,P=0.020),but there was no signifieant difference in 3 months and 6-12 months duration postoperatively.Better corneal sensation was found at postoperative 3 months (WMD=-0.62,95％CI:-l.09 to-0.19,P=0.005) in the nasal/temporal-hinge group,but there was no difference in 1 week and 6-12 months duration postoperatively.No significant difference was seen between the two groups in Schirmer Ⅰ test during the follow-up period (P＞0.05).Conclusions LASIK with nasal/temporal-hinge corneal flap can improve the corneal sensation and relief the dry eye syndrome after LASIK to some extent.More high-quality evidence-based studies are still needed for the further clinical evaluation.

Factors Influencing Corneal Flap Thickness in Laser In Situ Keratomileusis with a Femtosecond Laser

PURPOSE: To evaluate factors responsible for the variability between intended and achieved corneal-flap thickness during femtosecond laser-assisted laser in situ keratomileusis (LASIK). METHODS: A prospective, nonrandomized, case study was performed on 35 eyes of 18 consecutive patients who underwent LASIK surgery using the 60 kHz femtosecond laser microkeratome. Eyes were assigned to three different thickness groups, with 110-, 120-, or 130-microm cut depths. Anterior segment optical coherence tomography was used to assess the morphology of 35 LASIK flaps at postoperative one week postoperatively. The flap thickness was assessed at seven measuring points across each flap. Patient age, preoperative spherical equivalent, manual keratometry, preoperative central pachymetry, and regional variability of the cornea were evaluated to determine where they influenced the achieved corneal flap thickness. RESULTS: Cuttings of all flaps were easily performed without any intraoperative complications. Flap-thickness measurements had a mean of 115.21 +/- 4.98 microm (intended thickness, 110 microm), 121.90 +/- 5.79 microm (intended, 120 microm), and 134.38 +/- 5.04 microm (intended, 130 microm), respectively. There was no significant difference between the 110-microm and 120-microm groups when compared with the 130-microm group (one-way analysis of variance test, p > 0.05). Patients' age, preoperative spherical equivalent, manual keratometry, and preoperative central pachymetry did not affect the achieved flap thickness (Pearson correlations test, p > 0.05). The reproducibility of flap thickness in the central 1.5-mm radius area was more accurate than that in the peripheral 3.0 to 4.0-mm radius area (paired samples t-test, p < 0.05). CONCLUSIONS: Femtosecond laser-assisted LASIK is likely to reproduce a reliable thickness of the corneal flap, which is independent of corneal shape factors or refractive status. Future studies should focus on variations in corneal biomechanical factors, which may also play an important role in determining flap thickness.

Effect of microkeratome suction duration on corneal flap thickness and diameter in pigs / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To determine the effect of suction duration on thickness and diameter of corneal flap created by microkeratome in porcine eyes in laser in situ kerato-mileusis (LASIK).METHODS: Sixty porcine eyes were randomly assigned to three groups according to different suction durations: group 1 (10 seconds), group 2 (20 seconds), and group 3 (30 seconds). A Moria M2 microkeratome (Moria, France) with a 160μm head was used to create a corneal flap. Corneal flap thickness was measured by automated ultrasonic pachymetry, and the flap diameter was measured by a vernier caliper.RESULTS: The flap thickness of group 1, group 2 and group 3 was 146.05±13.46μm, 157.35±18.95μm and 169.25±21.02μm, respectively. There was a statistically significant difference among three groups (P=0.001). The mean flap diameter in groups 1, 2 and 3 was 8.63±0.19mm, 8.89±0.24mm and 9.06±0.18mm, respectively. A statisti-cally significant difference was found among groups (P<0.01).CONCLUSION: In LASIK in porcine eyes, an increase in suction duration resulted in a thicker and greater flap.

Reproducibility of IntraLASIK Flap Thickness Measured with Optical Coherence Tomography

PURPOSE: To investigate the relationship among optical coherence tomography (OCT), ultrasound pachymetry, and Orbscan in central corneal thickness measurement and to evaluate the reproducibility of flap thickness using an IntraLase femtosecond laser. METHODS: Central corneal thickness was measured by OCT, ultrasound pachymetry, and Orbscan in 59 eyes of 30 patients before LASIK. After IntraLASIK, the corneal flap thickness measured using OCT was compared with the intended corneal flap thickness. RESULTS: Central corneal thickness measured by OCT was thinner than that measured by other instruments preoperatively, but there was no significant difference among these methods (p>0.01), and corneal thickness values obtained by ultrasound pachymetry and Orbscan correlated well with those obtained by OCT (r ranged from 0.804 to 0.889, p0.01). CONCLUSIONS: OCT is a relatively accurate instrument for measuring corneal thickness and can easily measure the corneal flap thickness after LASIK. Compared with the results of a previous study, the mean measured flap thickness in this study was more reproducible with the IntraLase femtosecond laser.

Contrast analysis of corneal flap thickness using Moria M290 and 110 microkeratome / 上海第二医科大学学报

Objective To analyze the corneal flap thickness in laser in situ keratomileusis(LASIK) using Moria M2 microkeratome and to identify the related factors. Methods Sixty patients with LASIK were divided into two groups: M2 90 group,using the Moria M2 90 microkeratome,n=30;M2 110 group,using the Moria M2 110 microkeratome,n=30.All were performed on both eyes with the right one treated first.Subtraction pachymetry was used to measure corneal flap thickness which was analyzed statistically with the data including age,preoperative corneal diameter,curvature,corneal thickness and refraction. Results In the 30 patients of M2 90 group,the mean corneal flap thickness of right eye and left eyes were(128.03?12.03)?m(105~156 ?m) and(123.40?12.38) ?m(92~147 ?m),respectively,and the corneal flap thickness were statistically different between the right and left eyes(P

Preoperative Factors related to Corneal Flap Thickness in LASIK using Microkeratome

PURPOSE: To identify factors that may be related to variations in corneal flap thickness in LASIK using the Moria M2 microkeratome. METHODS: The charts of patients having LASIK based on steep keratometry nomogram using Moria M2 microkeratome (head : 110 micrometer) and excimer laser (VISX STAR S2, USA) in our department of ophthalmology from March, 2003, to May 2005, were reviewed retrospectively. A total of 195 eyes were enrolled in the investigation. We analyzed relationship between corneal flap thickness and preoperative factors including central corneal thickness, steep keratometer, corneal diameter, suction ring using multiple regression analysis. RESULTS: Mean corneal flap thickness was 119.37+/-21.21 micrometer. There was a statistically significant positive correlation between flap thickness and central corneal thickness (p<0.05). No correlation was found between flap thickness and other preoperative factors including steep keratometer, corneal diameter and suction ring. CONCLUSIONS: Mean corneal flap thickness using the Moria M2 110 micrometer head was 119.37+/-21.21 micrometer, little thicker than our expectation. When surgery is performed based on steep keratometry nomogram using Moria M2 microkeratome, if intraoperative factors are excluded, there is a trend toward thicker flap thickness with thicker central corneal thickness, whereas steep keratometer, corneal diameter or suction ring have no influence on flap thickness.

The Availability and Safety of the Microkeratome in LASIK

PURPOSE: To evaluate the reproducibility of the flap thickness in LASIK using Moria M2 microkeratome and to examine the safety and the complication rate intraoperatively and postoperatively. METHODS: 92-Ninety-two consecutive eyes of 50 patients that received LASIK using the Moria M2 microkeratome were reviewed. The mean of the predictable corneal flap thickness was compared with the mean of the created corneal flap thickness, and intraoperative and postoperative complication and safety were evaluated. RESULTS: The average corneal flap thicknesses were 140+/-15.16 micrometer with 130 micrometer head and 108.01+/-16.72 micrometer with 110 micrometer head. There was no statistically significant correlation between the predictable corneal flap thickness and the created corneal flap thickness with the 130 micrometer head (p=0.001, one-sample t-test), but there was a stastistically significant correlation with the 110 micrometer head (p=0.573, one-sample t-test). CONCLUSIONS: The M2 Moria microkeratome created a desirable thickness with the 110 micrometer head, and we can expect postoperative stability of the remaining corneal thickness. The complication rate both intraoperatively and postoperatively was very low.