Customized eye modeling for optical quality assessment in myopic femto-LASIK surgery.

Refractive surgery is recognized as an effective method for myopia treatment, but it can induce night vision disturbances such as glare. We present an eye modeling method for the optical quality assessment in response to the structural changes in the eyes by femto-LASIK surgery. Customized eye models were built from the measurements of 134 right eyes pre- and post-operatively. Optical performance was evaluated using spot diagrams, point spread functions (PSFs), modulation transfer functions (MTFs), and chromatic aberrations at various fields (0°-30°), different pupil diameters (2-6 mm), and initial myopias (- 1.25 to - 10.5 D). Pupil size and initial myopia are the two major factors that affect visual performance of post-operative eyes. The results of spot diagrams, PSFs, and MTFs indicated that post-operative visual performance deteriorated as the visual field and pupil size increased, and it was significantly influenced by initial myopia. Post-operative chromatic aberrations were also affected by initial myopia. As pupil size increased, the post-operative longitudinal chromatic aberrations tended to decrease slightly, while the transverse chromatic aberrations remained similar. The use of eye modeling for refractive surgery assessment could possibly provide a more personalized surgical approach, could improve the prediction accuracy of refractive surgery outcomes, and promote the invention and development of better surgical methods.

Long-Term Outcomes of Refractive Surgery Performed During the Military.

INTRODUCTION: To evaluate the long-term refractive results of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) performed by the military in a veteran population. MATERIALS AND METHODS: Three Department of Veterans Affairs (VA) hospital sites (Puget Sound, Buffalo, and Washington D.C.) obtained IRB approval for this multi-center study. Comprehensive ophthalmologic assessment including refraction and keratometry were obtained at the time of the long-term VA examination and compared to the patients' postoperative military records. RESULTS: Eighty patients (160 eyes) enrolled in this study. At the time of treatment, patients were 21-52 years of age. Long-term post-operative data was available from 4 to 17 years post-operatively. Fifteen percent of the treatment types were LASIK and 85% PRK. At the time of their military post-operative exam (range 3-14 months, mean 4 months), 82% of patients had uncorrected visual acuity (UCVA) of 20/20 or better, and their average manifest refraction was -0.08 D (SD ± 0.48 D). At the time of the long-term ophthalmological exam at the VA medical centers (range 4-11 years, mean of 8.2 years), 49% of patients had an UCVA of 20/20 or better and an average manifest refraction was -0.64 D (SD ± 0.69 D). CONCLUSION: This is the first long-term study evaluating refractive surgery outcomes up to 17 years in a military population. Our study demonstrates safety after refractive surgery in the military with less than 0.1D increase in myopia per year and strong keratometric stability. Other changes in the eye may be the likely cause for this observed mild refractive shift.

Avoidance of serious medical errors in refractive surgery using a custom preoperative checklist.

PURPOSE: To implement and measure the effect of a surgical safety checklist on the prevention of serious medical errors (never-events). SETTING: Boston Eye Group, Boston, Massachusetts, USA. DESIGN: Retrospective cohort study. METHODS: A safety checklist incorporating 28 sources of error was designed and implemented in December 2011 at the Boston Eye Group's refractive surgical center. Consecutive patients who had primary or enhancement laser vision correction (LVC) between July 2009 and February 2014 were included in this study. Before that date, a general checklist fashioned around the World Health Organization time-out procedure was used. The latter subjects were recruited as controls. The perioperative characteristics of both groups were retrospectively compared. RESULTS: The study comprised 2951 consecutive patients who had primary or enhancement LVC between July 2009 and February 2014; of these, 1417 patients (2744 eyes) had LVC after the implementation of a presurgical safety checklist. The general checklist fashioned around the World Health Organization time-out procedure was used for 1534 patients (2969 eyes). Both groups were comparable in patient age. The most common surgical procedures were laser in situ keratomileusis (78%) and laser-assisted subepithelial keratectomy with mitomycin-C (16%). Although there were 2 (0.07%) serious errors in the prechecklist cohort, none occurred following implementation of the safety checklist protocol (P = .23). The medical errors involved wrong refractive aim in 1 patient and wrong person-wrong procedure-wrong aim in another. CONCLUSIONS: Multiple potential sources of error exist in refractive surgery. The broad-scale implementation of a detailed presurgical safety checklist was helpful in minimizing and preventing serious errors (never-events) during LVC. FINANCIAL DISCLOSURE: Drs. Shapiro and Urman are members of the Institute for Safety in Office-Based Surgery, a nonprofit organization whose aims are to implement safety checklists for office-based surgery. No author has a financial or proprietary interest in any material or method mentioned.

Safety of cornea and iris in ocular surgery with 355-nm lasers.

A recent study showed that 355-nm nanosecond lasers cut cornea with similar precision to infrared femtosecond lasers. However, use of ultraviolet wavelength requires precise assessment of ocular safety to determine the range of possible ophthalmic applications. In this study, the 355-nm nanosecond laser was evaluated for corneal and iris damage in rabbit, porcine, and human donor eyes as determined by minimum visible lesion (MVL) observation, live/dead staining of the endothelium, and apoptosis assay. Single-pulse damage to the iris was evaluated on porcine eyes using live/dead staining. In live rabbits, the cumulative median effective dose (ED50) for corneal damage was 231 J/cm2, as seen by lesion observation. Appearance of endothelial damage in live/dead staining or apoptosis occurred at higher radiant exposure of 287 J/cm2. On enucleated rabbit and porcine corneas, ED50 was 87 and 52 J/cm2, respectively, by MVL, and 241 and 160 J/cm2 for endothelial damage. In human eyes, ED50 for MVL was 110 J/cm2 and endothelial damage at 453 J/cm2. Single-pulse iris damage occurred at ED 50 of 208 mJ/cm2. These values determine the energy permitted for surgical patterns and can guide development of ophthalmic laser systems. Lower damage threshold in corneas of enucleated eyes versus live rabbits is noted for future safety evaluation.

Standardization of laser in situ keratomileusis surgical technique evaluated by comparison of procedure time between 2 experienced surgeons.

PURPOSE: To evaluate the concordance of surgical step pacing between 2 experienced surgeons following a standardized surgical protocol for bilateral laser in situ keratomileusis (LASIK). SETTING: London Vision Clinic, London, United Kingdom. DESIGN: Retrospective comparative case series. METHOD: This was a video review comprising an equal number of consecutive bilateral LASIK patients for 2 surgeons following a standardized surgical protocol using the Visumax femtosecond laser and MEL 80 excimer laser. Timestamps were recorded for flap creation, flap lift, excimer laser ablation, and flap replacement. Total surgery time was defined with the endpoints of speculum insertion and removal. RESULTS: Each surgeon performed bilateral LASIK on 30 patients. The mean total surgery time was 11 minutes 17 seconds ± 1 minute 46 seconds (SD) for surgeon 1 and 12 minutes 13 seconds ± 1 minute 37 seconds for surgeon 2. The mean bilateral flap creation time was 3 minutes 5 seconds ± 24 seconds and 3 minutes 42 seconds ± 25 seconds, respectively. The mean suction time for an individual eye was 26 seconds ± 4 seconds for surgeon 1 and 23 seconds ± 1 second for surgeon 2. The difference in timing was accounted for by differences in the length of surgeon conversation with patients rather than by physical surgical steps. CONCLUSIONS: Bilateral LASIK procedure time was highly concordant within and between surgeons using a standardized surgical protocol. Use of a standardized surgical protocol can optimize the efficiency of corneal suction time as well as total surgical time while providing the expected equivalency in visual outcomes between surgeons.

Comparative study of stromal bed of LASIK flaps created with femtosecond lasers (IntraLase FS150, WaveLight FS200) and mechanical microkeratome.

BACKGROUND/AIM: To compare stromal bed smoothness in LASIK flaps created with two different femtosecond lasers (IntraLase FS150 and WaveLight FS200) and a mechanical microkeratome (MMK) (Carriazo-Pendular microkeratome). METHODS: Sixty freshly enucleated porcine eyes were used for the study. Twenty flaps were created and constitute each of the following three groups: IntraLase FS150 (IFS group), WaveLight FS200 (WFS group) and MMK (MMK group). In each of the three groups, 10 flaps were created with intended thickness of 110 µm and another 10 flaps with 130 µm. Images were assessed with light microscopy and scanning electron microscopy. Qualitative surface roughness grading of the images was performed by five masked observers and statistical comparisons of scores were made between groups. RESULTS: The results of qualitative surface roughness grading demonstrated that there was no significant difference between the two femtosecond (FS) lasers when comparing the subgroups with the same flap thickness (p>0.05 in both comparisons, Mann-Whitney U test). In addition, there was no statistically significant difference (p>0.05) in each flap maker group between different thickness subgroups. However, the scores of the FS laser subgroups were significantly better than the scores of the MMK subgroups with corresponding flap thicknesses (p<0.05, Mann-Whitney U test). CONCLUSIONS: Our study demonstrates that the IntraLase FS150 and the WaveLight FS200 had a similar performance and provided flaps with smooth surfaces. In comparison to the MMK, the studied femtosecond laser systems had a superior performance in terms of smoothness.

Visual quality of Q-value-guided LASIK in the treatment of high myopia.

PURPOSE: To compare visual performance and patient satisfaction following Q-value-guided customized laser-assisted in situ keratomileusis (LASIK) and standard LASIK in the treatment of high myopia. METHODS: A total of 116 patients with high myopia (-6.00 to -9.50D; astigmatism from -0.00 to -2.00D) were treated using Z-217 excimer laser (Bausch & Lomb). Sixty-six patients (132 eyes) receiving Q-value-guided customized LASIK were assigned into the experimental group, and 50 cases (100 eyes) receiving standard LASIK were used as normal controls. All subjects were followed up for > 6 months to monitor for night vision problems measure postoperative quality of life. RESULTS: In the experimental group, night vision acuity decreased in 3 cases (4.5%), and glare was reported in 13 patients (19%) during the 6-month follow up period. In the control group, night vision problems were noted in 9 cases (18%), and glare occurred in 21 patients (42%). These differences between the two groups were statistically significant (P<0.05). According to the postoperative questionnaire, satisfaction with visual performance and quality of life was reported in 73% of the experimental group, and 52% of the control group (P<0.05). CONCLUSION: Patients with high myopia surgically treated by Q-value-guided LASIK had better night-time visual performance and a higher degree of satisfaction compared with subjects receiving standard LASIK.

[LASIK - a new treatment or the standard]. / LASIK - Neulandbehandlung oder medizinischer Standard.

Classification of LASIK in refractive surgery and treatment by health insurance, and education by the physician. Results in clinical studies and case law in Germany 2010.

Flap thickness variation with 3 types of microkeratome heads.

PURPOSE: To determine flap thickness variation with 3 types of microkeratome heads and identify the potential factors that affect flap thickness. SETTING: Ruijin Hospital, Department of Ophthalmology, Shanghai, China. DESIGN: Comparative case series. METHODS: Laser in situ keratomileusis was performed using the Moria microkeratome with the One Use-Plus SBK, M2 90, or M2 110 head. Flap thickness was calculated by subtraction pachymetry. Age, central corneal thickness (CCT), spherical equivalent refraction, mean keratometry, and horizontal corneal diameter were recorded preoperatively. RESULTS: The study comprised 180 eyes of 90 patients; 60 eyes were treated with each head. The difference in mean flap thickness between right and left eyes was not significant in the SBK group (97.50 µm ± 11.39 [SD] versus 96.73 ± 10.45 µm; P = .44) but was significant in the M2 90 group (128.03 ± 12.03 µm versus 123.40 ± 12.38 µm; P = .0071) and the M2 110 group (140.53 ± 15.14 µm versus 135.23 ± 18.03 µm, P = .0035). The difference from the intended flap thickness (right eyes and left eyes) was 2.50 ± 11.39 µm and 3.27 ± 10.45 µm, respectively, in the SBK group; -8.03 ± 12.03 µm and -3.40 ± 12.38 µm, respectively, in the M2 90 group; and -0.53 ± 15.14 µm and 4.77 ± 18.03 µm, respectively, in the M2 110 group. Flap thickness was positively correlated with baseline CCT in each group. CONCLUSIONS: Flap thickness was positively correlated with the preoperative CCT using the Moria microkeratome. The SBK head demonstrated the most accurate flap thickness, followed by the M2 90 head and the 110 head. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Decision Assistant Wizard to standardize optimal outcomes in excimer laser refractive corneal surgery.

PURPOSE: To assess a decision tree analysis system to further optimize refractive surgery outcomes. METHODS: A 5-step decision tree, the Decision Assistant Wizard, based on previous experience with the SCHWIND AMARIS laser, was applied for selecting a customized refractive surgery treatment mode (aspheric aberration neutral, corneal wavefront-guided, or ocular wavefront-guided) to eliminate or reduce total aberration. RESULTS: Using the Decision Assistant Wizard, 6467 LASIK treatments were performed over a 30-month period; 5262 and 112 for myopic and hyperopic astigmatism, respectively, using aspheric aberration neutral (AF) profiles, 560 using corneal wavefront-guided profiles, and 533 using ocular wavefront-guided profiles. Twenty-two (0.3%) retreatments were performed overall; 18 (0.3%) and 0 (0%) after myopic and hyperopic astigmatism, respectively, using AF, 3 (0.5%) after corneal wavefront-guided profiles, and 1 (0.2%) after ocular wavefront-guided profiles. CONCLUSIONS: Decision Assistant Wizards may further optimize refractive surgical outcomes by providing the most appropriate ablation pattern based on an eye's anamnesis, diagnosis, and visual demands. The general principles may be applied to other laser systems; however, specifics will depend on manufacturers' specifications.

Measuring patient's expectation and the perception of quality in LASIK services.

BACKGROUND: LASIK is the use of excimer lasers to treat therapeutic and refractive visual disorders, ranging from superficial scars to nearsightedness (myopia), and from astigmatism to farsightedness (hyperopia). The purposes of this study are to checking the applicability and psychometric properties of the SERVQUAL on Lasik surgery population. Second, use SEM methods to investigate the loyalty, perceptions and expectations relationship on LASIK surgery. METHODS: The method with which this study was conducted was questionnaire development. A total of 463 consecutive patients, attending LASIK surgery affiliated with Chung Shan Medical University Eye Center, enrolled in this study. All participants were asked to complete revised SERVQUAL questionnaires. Student t test, correlation test, and ANOVA and factor analyses were used to identify the characters and factors of service quality. Paired t test were used to test the gap between expectation and perception scores and structural equation modeling was used to examine relationships among satisfaction components. RESULTS: The effective response rate was 97.3%. Validity was verified by several methods and internal reliability Cronbach's alpha was > 0.958. The results from patient's scores were very high with an overall score of 6.41(0.66), expectations at 6.68(0.47), and perceptions at 6.51(0.57). The gap between expectations and perceptions was significant, however, (t = 6.08). Furthermore, there were significant differences in the expectation scores among the different jobs. Also, the results showed that the higher the education of the patient, the lower their perception score (r = -0.10). The factor loading results of factor analysis showed 5 factors of the 22 items of the SERVQUAL model. The 5 factors of perception explained 72.94% of the total variance there; and on expectations it explained 77.12% of the total variance of satisfaction scores.The goodness-of-fit summary, of structure equation modeling, showed trends in concept on expectations, perceptions, and loyalty. CONCLUSION: The results of this research appear to show that the SERVQUAL instrument is a useful measurement tool in assessing and monitoring service quality in LASIK service, and enabling staff to identify where improvements are needed, from the patients' perspective. There were service quality gaps in the reliability, assurance, and empathy. This study suggested that physicians should increase their discussions with patients; which has, of course, already been proven to be an effective way to increase patient's satisfaction with medical care, regardless of the procedure received.

Accuracy of corneal flap thickness achieved by two different age MK-2000 microkeratomes.

AIMS: To investigate the accuracy of corneal flap thickness (FT) using two different age MK-2000 microkeratomes. METHODS: The prospective cohort study enroled 260 patients with refractive error. Flaps were created using two microkeratomes A and B (new and aged, respectively) with 130-mum heads in two patient groups and two times the same blade in both treated eyes of each patient. The variations in FTs were compared between two groups and between both operated eyes of each patient. The correlations were analysed between FT and CCT or keratometric power. RESULTS: In the A and B groups, the average FTs were 123.3+/-18.7 and 147.5+/-19.1 mum respectively. Difference in measurements between the actual FTs of first eye operations in the A group and intended 130 mum of FTs was not significant (P=0.462), but those of second operated eyes in the A group and both treated eyes in the B group were significant (P<0.001). Second cut achieved a thinner flap and increased the variability in FT, and an aged microkeratome achieved a thicker flap than a new microkeratome and than that claimed by the manufacturer. Positive correlations were observed between preoperative CCT and FT (P<0.05). CONCLUSIONS: The first eye operation by a new MK-2000 microkeratome achieves the accuracy of the intended FT. FTs varied between first and second cuts of each patient and between two different age MK-2000 microkeratomes. LASIK surgeons should compare FT when using an aged MK-2000 microkeratome, and frequent and periodic comparison of FT achieved by all microkeratomes may be also recommended.

Accuracy and precision of LASIK flap thickness using the IntraLase femtosecond laser in 1000 consecutive cases.

PURPOSE: To report the safety and flap thickness predictability of LASIK using the IntraLase femtosecond laser. METHOD: A retrospective analysis of 1000 consecutive LASIK cases was performed to assess the rate of intra- and postoperative complications and loss of best spectacle-corrected visual acuity (BSCVA). A subset of 260 eyes was prospectively analyzed to assess flap thickness predictability using subtraction ultrasound on the day of surgery. RESULTS: No serious intra- or postoperative complications were noted. Three (0.3%) patients had epithelial defects that required a bandage contact lens. Four (0.4%) patients had slipped caps on day 1 that required repositioning. Two (0.2%) patients developed grade I diffuse lamellar keratitis. No patient developed epithelial ingrowth >1 mm from the flap edge, transient light sensitivity, or infection. No patient lost > or = 2 lines of BSCVA at 6 months postoperatively. With an attempted flap thickness of 105 microm with the 15-KHz laser, the mean flap thickness was 116.79 +/- 10.75 microm (range: 95 to 148 microm) (n = 119). In the 30-KHz group (n = 141), the target corneal flap thickness was 115 microm, with a mean flap thickness of 114.02 +/- 9.82 microm (range: 93 to 163 microm). Overall 87.3% of eyes were within +/- 20 microm of the intended result. Ninety-eight percent of caps created with the 30-KHz laser were within +/- 20 microm compared to 74.8% in the 15-KHz group. CONCLUSIONS: LASIK surgery with the IntraLase femtosecond laser is safe and flap thickness is predictable.

Advances in technologies for laser-assisted in situ keratomileusis (LASIK) surgery.

Laser-assisted in situ keratomileusis (LASIK) has become the most widely used form of refractive surgery today. The objective of this surgical technique is to modify the anterior corneal shape by ablating tissue from the stroma by means of the excimer laser after creating a hinged corneal flap. This way, we are able to change the refractive status of the patient, providing better unaided vision. Continuous improvements in the original technique have made the surgical procedure safer, more accurate and repeatable. These progressions are due to the development of novel technologies that are the responsible for new surgical instrumentation, which makes the surgical procedure easier for the surgeon, and better excimer laser ablation algorithms, which increase the optical quality of the ablation and thus the safety of the vision correction procedure. This article aims to describe the more relevant advances in LASIK that have played an important role in the spread and popularity of this technique.

Epi-LASIK using the Amadeus II microkeratome: evaluation of cut quality using light and electron microscopy.

PURPOSE: To investigate the cut quality and surface characteristics of the epithelial flap and underlying Bowman's membrane created by the Amadeus II (AMO) microkeratome on human corneas using light and electron microscopy. SETTING: Center for Refractive Therapy, Department of Ophthalmology, Ludwig-Maximilians University, Munich, Germany. METHODS: Using a 9.0 mm type II suction ring and settings, as recommended by the manufacturer, epithelial laser in situ keratomileusis (epi-LASIK) was performed in 2 fresh human eyes of 1 donor. Ocular pathology and previous ocular surgery were ruled out. Tissues for light microscopy were examined using hematoxylin-eosin and periodic acid-Schiff reaction staining. Further tissue samples were examined using scanning electron microscopy and transmission electron microscopy. RESULTS: Light microscopy showed a thoroughly separated epithelial sheet with no evident anatomical abnormalities. Stratification of the separated epithelium layer and cell shape was conserved. The cleavage plane was located at Bowman's membrane. Scanning electron microscopy showed a consistent transition from adherent epithelium to the denuded area. Bowman's layer showed a very smooth surface without remains of basal lamina. Transmission electron microscopy examination showed interruptions of the basement membrane at high magnification. CONCLUSIONS: This in vitro study found a high cut quality using the epi-LASIK separator of the Amadeus II microkeratome. The resulting cleavage plane at Bowman's membrane was well suited for the subsequent laser ablation.