Cataract Surgery Considerations for Diabetic Patients.

PURPOSE OF REVIEW: Given the epidemiology and demographic trends of diabetes mellitus and cataracts, ophthalmologists are likely to encounter patients with both comorbidities at an increasing frequency. Patients with diabetes represent a higher risk population than healthy patients for cataract surgery. In this review, we discuss key risks and risk-mitigation practices when performing cataract surgery on these patients. RECENT FINDINGS: Patients with diabetes continue to represent a high-risk surgical population: Nagar et al. suggest a dose-dependent relationship may exist between number of intravitreal injections and likelihood of posterior capsular rupture. However, novel treatments are improving outcomes for patients with diabetes. Several studies have reported intracameral phenylephrine/ketorolac may reduce the incidence of post-operative cystoid macular edema while others have discussed the efficacy of pre-treatment and post-treatment with intravitreal bevacizumab on improving cataract surgery outcomes in patients with diabetic retinopathy. Pre-operatively, ophthalmologists should perform an enhanced evaluation, consider timing and lens selection decisions, and complete any appropriate pre-operative treatment. Peri-operatively, surgeons should be aware of pupillary dilation adjustments, combination surgery options, and potential complications. Post-operatively, clinicians should address pseudophakic cystoid macular edema, diabetic macular edema, diabetic retinopathy, and posterior capsular opacification.

Effectiveness of multifocal and monofocal intraocular lenses for cataract surgery and lens replacement: a systematic review and meta-analysis.

PURPOSE: Multifocal intraocular lenses (IOLs) offer the possibility of spectacle-free vision following cataract surgery compared to standard IOLs. Existing systematic reviews have generally concluded that multifocal IOLs result in better uncorrected near vision and greater spectacle independence, but more unwanted visual phenomena such as glare and halos, compared to monofocal IOLs. However, the certainty of evidence has been low for most outcomes, and pooled analyses have grouped together technologically obsolete lenses with newer lenses, potentially obscuring differences in performance across different lens types. METHODS: We performed a systematic review searching for RCTs of a multifocal IOL to a standard IOL or monovision that reported spectacle independence, visual acuity, or quality of life. Databases were searched from 1/1/2006-4/30/2017. Existing reviews were used to identify older studies. Title/abstract screening and data extraction were done in duplicate. Where possible, random effects meta-analysis was performed to synthesize results. In addition to comparing multifocal IOLs as a group to monofocal IOLs, we also compared newer diffractive lenses to obsolete or refractive lenses. RESULTS: Twenty-five eligible studies were identified. There was no difference in pooled estimates of corrected or uncorrected distance vision between multifocal and standard IOLs. Compared to monofocal IOLs, multifocal IOLs had statistically significantly better pooled results for the outcome of near vision (10 studies, 1025 patients, mean difference in logMAR of -0.26 (95% CI -0.37, -0.15)); spectacle dependence (12 studies, 1237 patients, relative risk of 0.27 (95% CI 0.20, 0.38)) and borderline significantly better quality of vision (6 studies, 596 patients, standardized mean difference of -0.54, (95% CI -1.12, 0.04)). Compared to monofocal IOLs, multifocal IOLs had statistically significantly worse pooled results for the outcomes of glare (9 studies, 847 patients, risk ratio of 1.36 (95% CI 1.15, 1.61) and halos (7 studies, 754 patients, risk ratio of 3.14 (95% CI 1.63, 6.08). Newer multifocal lenses had statistically significantly better outcomes than older diffractive lenses or refractive lenses, when compared to monofocal IOLs, in near vision, quality of vision, and risk of halos. CONCLUSIONS: Multifocal IOLs compared to standard IOLs or monovision result in better uncorrected near vision and a higher proportion of patients who achieve spectacle independence, but greater risk of unwanted visual phenomena. Newer diffractive lenses may be better than refractive lenses in near vision and quality of vision outcomes, with less risk of halos than older diffractive lenses and refractive lenses. (PROSPERO registration CRD42017069949).

Repeatability of central corneal thickness measurements of donor corneas in preservation chamber using Fourier-domain anterior segment optical coherence tomography.

To evaluate the repeatability of central corneal thickness (CCT) measurements in donor corneas using optical coherence tomography (OCT, RTVue-Optovue, Inc., Fremont, CA). Consecutive corneas were measured by a single observer using the RTVue. All corneas were preserved in the Transend chamber and Life4 °C media (Numedis, Inc., Isanti, MN/USA) and stored at 4 °C. The repeatability was evaluated using a pooled within-subject standard deviation (SD), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). To investigate inter-observer repeatability, a second observer independently measured the CCT for each image scan. CCT was measured in 32 eyes from 18 donors. Measurements were independently repeated by a second observer. The corneas had a mean CCT of 490.99 µm ± 65.95 (381-642) as measured by Observer 1. For observer 1, the SD value for the CCT was 2.94 µm, the CoV value was 0.597%, and the ICC value was 0.998 (95% CI 0.996, 0.999). For observer 2, the SD value was 5.91 µm, the CoV value was 1.21%, and the ICC value was 0.992 (95% CI 0.985, 0.996). The Kappa statistic 21.88% with a p value < 0.001. The Bland-Altman plot shows that the average CCT measurements between the two observers were within 20 µm of each other. The CCT measurements of donor corneas in the preservation chamber using Fourier domain OCT is highly repeatable.

Outcomes of femtosecond laser-assisted cataract surgery performed by surgeons-in-training.

PURPOSE: To compare intraoperative factors and post-operative outcomes of femtosecond laser-assisted cataract surgery (FLACS) and manual cataract surgery performed by resident surgeons. METHODS: All cases of FLACS performed by resident surgeons during the 2013-2014 academic year were compared to a control group of manual cataract surgery cases with regards to pre-operative patient data, operative complications, cumulative dissipated energy (CDE), postoperative corrected distance visual acuity (CDVA), refractive prediction error (RPE), and corneal edema. RESULTS: There were no significant preoperative differences in the FLACS (n = 57) and manual (n = 68) groups. Operative complication rates were similar in cases with sufficient data and follow-up with a higher rate of posterior capsule tear in the manual group. CDE (percent-seconds) was lower in the FLACS group (FLACS: 14.5 ± 7.5; manual: 21.6 ± 11.5; p < 0.01). CDVA (LogMAR) was comparable at 1 month postoperatively (FLACS: 0.004 ± 0.08; manual: 0.024 ± 0.11; p = 0.24) and 1 year postoperatively (FLACS: 0.013 ± 0.06; manual: 0.032 ± 0.09; p = 0.37). No difference in RPE was found at 1 month postoperatively (FLACS: 0.38 ± 0.24 D; manual: 0.41 ± 0.49 D; p = 0.66) and 1 year postoperatively (FLACS: 0.49 ± 0.63 D; manual: 0.34 ± 0.26 D; p = 0.31). CONCLUSIONS: Femtosecond laser-assisted cataract surgery is safe and effective compared to manual cataract surgery when performed by resident surgeons. Both 1-month and 1-year outcomes show no difference in refractive predictive error in FLACS compared to manual cataract surgery in surgeons in training.

Intraocular lens alignment methods.

PURPOSE OF REVIEW: This article reviews current concepts in intraocular lens alignment strategies to maximize intraocular lens (IOL) positioning. RECENT FINDINGS: A variety of strategies has been developed to maximize toric IOL position, including preoperative calculators to determine the appropriate IOL power and orientation, intraoperative alignment devices, and postoperative software to determine if IOL rotation would be beneficial for refractive outcomes. SUMMARY: The combination of using multiple toric IOL calculators and intraoperative alignment devices has improved toric IOL outcomes. The relationship of the posterior corneal power and its effect on outcomes remains to be fully elucidated. Postoperative IOL rotation may be necessary even when the IOL is aligned as planned because of surgically induced astigmatism.

Current and future applications of corneal cross-linking.

PURPOSE OF REVIEW: To review current concepts and future directions of corneal cross-linking (CXL) as a treatment for keratoconus, ectasia after refractive surgery and infectious keratitis. RECENT FINDINGS: Several important laboratory and clinical studies have established the safety and success of corneal cross-linking for the treatment of keratoconus and other corneal ectasias. Recently, additional studies have analyzed new directions and controversies in corneal cross-linking, exploring new indications, comparing new techniques and analyzing results of new protocols. SUMMARY: The results of bench and clinical research are providing the foundation to allow for protocol modifications of the standard cross-linking protocols and expansion of cross-linking concepts for techniques such as accelerated cross-linking, epithelium-sparing protocols and measurement of progression and success.

Comparison of Keratoconus Specific to Standard IOL Formulas in Patients With Keratoconus Undergoing Cataract Surgery.

PURPOSE: To assess the performance of multiple intraocular lens (IOL) formulas in eyes with keratoconus. METHODS: Eyes with stable keratoconus scheduled for cataract surgery with biometry measurements on the Lenstar LS900 (Haag-Streit) were included. Prediction errors were calculated using 11 different formulas, including two with keratoconus modifiers. Primary outcomes compared standard deviations, mean and median numerical errors, and percentage of eyes within diopter (D) ranges across all eyes with subgroup analysis according to anterior keratometric values. RESULTS: Sixty-eight eyes from 44 patients were identified. In eyes with keratometric values less than 50.00 D, prediction error standard deviations ranged from 0.680 to 0.857 D. Percentages of eyes within ±0.50 D of target ranged from 57.89% to 73.68% with no statistical differences among formulas. In eyes with a keratometric value of more than 50.00 D, prediction error standard deviations ranged from 1.849 to 2.349 D and were not statistically different with heteroscedastic analysis; percentages of eyes within ±0.50 D of target ranged from 0% to 18.18% with no statistical differences among formulas. Only keratoconus-specific formulas (Barrett-KC and Kane-KC) and the Wang-Koch axial length adjustment version of SRK/T resulted in median numerical errors not significantly different than 0, regardless of keratometric values. CONCLUSIONS: In keratoconic eyes, IOL formulas are less accurate than in normal eyes and result in hyperopic refractive outcomes that increase with steeper keratometric values. Using keratoconus-specific formulas and the Wang-Koch axial length adjustment version of SRK/T for axial lengths of 25.2 mm or greater improved IOL power prediction accuracy compared to other formulas. [J Refract Surg. 2023;39(4):242-248.].

Comparative postoperative topography pattern recognition analysis using axial vs tangential curvature maps.

PURPOSE: To determine prediction accuracy of patient refractive surgery status by novice reviewers based on topography pattern analysis using axial or tangential anterior curvature maps. SETTING: Four U.S. academic centers. DESIGN: Prospective case-control study. METHODS: Image evaluation was performed by novice reviewers (n = 52) at 4 academic institutions. Participants were shown 60 total images from 30 eyes presenting for cataract surgery evaluation with known refractive surgery status, including 12 eyes imaged with Placido-based topography and 18 eyes imaged with Scheimpflug-based tomography. There were 12 eyes with myopic ablations, 12 eyes with hyperopic ablations, and 6 eyes with no previous refractive surgery performed. Each eye was shown in both axial and tangential curvature from either device, reviewed as a single image at a time, and masked to the map type (axial vs tangential). RESULTS: For the 52 novice reviewers included, accuracy of pattern identification was 82.9% (517 of 624) for tangential vs 55.0% (343 of 624) for axial maps for eyes with myopic ablation (P < .00001), 90.9% (567 of 624) for tangential vs 58.3% (364 of 624) for axial maps for eyes with hyperopic ablation (P < .00001), and 15.4% (48 of 312) for tangential vs 62.8% (196 of 312) for axial maps for eyes with no ablation (P < .00001). There were no significant differences between Placido and Scheimpflug devices and no significant differences across groups based on year of training. CONCLUSIONS: Tangential curvature maps yielded significantly better pattern recognition accuracy compared with axial maps after myopic and hyperopic corneal refractive surgery ablations for novice reviewers. Using tangential curvature maps, especially for challenging cases, should benefit post-LASIK intraocular lens (IOL) calculator selection and, thereby, improve IOL power calculation accuracy.

Comparative Functional Outcomes After Corneal Crosslinking Using Standard, Accelerated, and Accelerated With Higher Total Fluence Protocols.

PURPOSE: To compare the relative 12-month corneal crosslinking (CXL) functional outcomes using standard protocol and accelerated protocols in patients with progressive keratoconus. METHODS: CXL was performed using 3 epithelium-off protocols: standard [3 mW/cm for 30 minutes, 5.4 J/cm (S3/30-CXL)], accelerated with equivalent total irradiance [9 mW/cm for 10 minutes, 5.4 J/cm (A9/10-CXL)], and accelerated with increased total irradiance [30 mW/cm for 4 minutes, 7.2 J/cm (A30/4-CXL)]. Efficacy measurements were evaluated 12 months after treatment with Scheimpflug imaging (Pentacam HR) and included change in maximum keratometry (K Max), corrected distance visual acuity (CDVA), other keratometric variables, pachymetry, keratoconus indices, astigmatism, asphericity, manifest refraction, and higher order aberrations. RESULTS: Ninety-three eyes (67 patients) were evaluated: 35 eyes (26 patients) with S3/30-CXL, 29 eyes (19 patients) with A9/10-CXL, and 29 eyes (22 patients) with A30/4-CXL. Mean [INCREMENT]K Max was -1.53 ± 2.1 diopter (D) for S3/30-CXL, -0.71 ± 1.3 D for A9/10-CXL, and -0.70 ± 2.3 D for A30/4-CXL (P = 0.37). Mean [INCREMENT]CDVA(logMAR) was -0.18 ± 0.2 for S3/30-CXL, -0.13 ± 0.2 for A9/10-CXL, and -0.18 ± 0.2 for A30/4-CXL (P = 0.79). [INCREMENT]K Mean (r = -0.29 to -0.46), anterior asphericity (r = -0.34 to -0.40), and central keratoconus index (r = -0.18 to -0.38) best correlated with [INCREMENT]CDVA. S3/30-CXL had greater changes in index of surface variance, index of vertical asymmetry, keratoconus index, and regularization index compared to A9/10-CXL and A30/4-CXL. There were no other differences between protocols. CONCLUSIONS: All 3 protocols showed improvements in K Max, CDVA, and other variables, with similar functional outcomes for each despite greater change in keratoconus indices after S3/30-CXL. Correlations between change in measured variables and CDVA were poor overall; however, K Mean, central keratoconus index, and anterior asphericity were better correlated with CDVA than K Max.

Distinguishing Highly Asymmetric Keratoconus Eyes Using Dual Scheimpflug/Placido Analysis.

PURPOSE: To identify the best metrics or combination of metrics that provide the highest predictive power between normal eyes and the clinically unaffected eye of patients with highly asymmetric keratoconus using data from a Dual Scheimpflug/Placido device. DESIGN: Retrospective case-control study. METHODS: Combined Dual Scheimpflug/Placido imaging was obtained from the Galilei G4 device (Ziemer Ophthalmic Systems AG, Port, Switzerland) in 31 clinically unaffected eyes with highly asymmetric keratoconus and 178 eyes from 178 patients with bilaterally normal corneal examinations that underwent uneventful LASIK with at least 1 year follow-up. Receiver operating characteristic (ROC) curves were generated to determine area under the curve (AUC), sensitivity, and specificity for 87 metrics, and logistic regression modeling was used to determine optimal variable combinations. RESULTS: No individual metric achieved an AUC greater than 0.79. A combined model consisting of 9 metrics yielded an AUC of 0.96, with 90.3% sensitivity and 92.6% specificity. Among those 9 metrics included, 5 related to corneal pachymetry: Opposite Sector Index and Anterior Height BFS Z from the anterior surface, Asphericity and Asymmetry Index, Posterior Height BFS Z, and Posterior Height BFS X from the posterior surface. The strongest variable in the model was the thinnest point location on the horizontal (x) axis. CONCLUSION: While individual metrics performed poorly, using a combination of metrics from the combined Dual Scheimpflug/Placido device provided a useful model for differentiating normal corneas from the clinically normal eyes of patients with highly asymmetric keratoconus. Pachymetry values were the most impactful metrics.

Comparing Change in Anterior Curvature After Corneal Cross-linking Using Scanning-slit and Scheimpflug Technology.

PURPOSE: To evaluate the correlation between anterior axial curvature difference maps following corneal cross-linking (CXL) for progressive keratoconus obtained from Scheimpflug-based tomography and Placido-based topography. DESIGN: Between-devices reliability analysis of randomized clinical trial data. METHODS: Corneal imaging was collected at a single-center institution preoperatively and at 3, 6, and 12 months postoperatively using Scheimpflug-based tomography (Pentacam; Oculus Inc, Lynnwood, Washington, USA) and scanning-slit, Placido-based topography (Orbscan II; Bausch & Lomb, Rochester, New York, USA) in patients with progressive keratoconus receiving standard protocol CXL (3 mW/cm2 for 30 minutes). Regularization index (RI), absolute maximum keratometry (K Max), and change in K Max (ΔK Max) were compared between the 2 devices at each time point. RESULTS: Fifty-one eyes from 36 patients were evaluated at all time points. Values were significantly different at all time points (56.01 ± 5.3 diopters [D] Scheimpflug vs 55.04 ± 5.1 D scanning-slit preoperatively [P = .003]; 54.58 ± 5.3 D Scheimpflug vs 53.12 ± 4.9 D scanning-slit at 12 months [P < .0001]) but strongly correlated between devices (r = 0.90-0.93) at all time points. The devices were not significantly different at any time point for either ΔK Max or RI but were poorly correlated at all time points (r = 0.41-0.53 for ΔK Max, r = 0.29-0.48 for RI). At 12 months, 95% limits of agreement were 7.51 D for absolute K Max, 8.61 D for ΔK Max, and 19.86 D for RI. CONCLUSIONS: Measurements using Scheimpflug and scanning-slit Placido-based technology are correlated but not interchangeable. Both devices appear reasonable for separately monitoring the cornea's response to CXL; however, caution should be used when comparing results obtained with one measuring technology to the other.

Phacoemulsification of the rock-hard dense nuclear cataract: Options and recommendations.

We describe the essential steps in the successful phacoemulsification of the rock-hard, dense cataract. Appropriate and directed preoperative history, physical examination, and diagnostics allow the surgeon to select the best incision, anesthesia, and intended surgical technique for a given dense nuclear challenge. Hard nucleus-specific approaches for hydrodissection, pupil management, and zonular protection then allow the surgeon to approach the rock-hard nucleus with maximum safety. Dense nuclear dismantling options are then discussed in detail along with fluidic and power modulation considerations. Various specific phacoemusification machine settings for rock-hard cataracts from the authors representing several different phaco systems are then presented. The combination of these steps and considerations allow a more successful dense cataract removal and potential restoration of vision for patients. This paper represents the collective experience and advice of the Challenging and Complex Cataract Surgery Subcommittee.

Preoperative Prediction of the Optimal Toric Intraocular Lens Alignment Meridian.

PURPOSE: To determine whether any of three keratometry devices is superior to the others in predicting the ideal toric intraocular lens (IOL) alignment meridian. METHODS: A retrospective review was performed to identify patients who underwent cataract phacoemulsification with toric IOL implantation from November 2014 to November 2016 at a single academic institution. For each patient, corneal measurements were performed with an optical low-coherence reflectometer/autokeratometer (OLCR), a dual Scheimpflug/Placido analyzer, and a color light-emitting diode (LED) topographer. Postoperatively, the ideal toric IOL alignment meridian that would have resulted in the least amount of residual astigmatism was determined using the online Berdhal & Hardten Toric Results Analyzer (BHTRA). To determine the prediction error, this ideal alignment meridian was compared to the corneal meridian with the highest refractive power, as provided by the three devices. RESULTS: Fifty-six eyes of 56 patients were included in the study. The mean absolute errors in the toric IOL alignment meridians of the color LED topographer, dual Scheimpflug/Placido analyzer, and OLCR were 5.2° ± 5.2°, 7.6° ± 5.7°, and 5.4° ± 5.1°, respectively. There was no significant difference in the ability of each device to predict the ideal alignment meridian as determined by the BHTRA. CONCLUSIONS: The color LED topographer, dual Scheimpflug/Placido analyzer, and OLCR may all be used to preoperatively determine the best alignment meridian for toric IOL placement. Surgeons should use their best judgment in determining which device to use in preoperative planning for individual patients. [J Refract Surg. 2018;34(8):515-520.].

Indications and outcomes of resident-performed cataract surgery requiring return to the operating room.

PURPOSE: To identify the clinical and operative factors predicting reoperation within 30 days of resident-performed cataract surgery and correlate them with 1-year visual outcomes. SETTING: Michael E. DeBakey Veterans Affairs Medical Center, Houston, Texas, USA. DESIGN: Retrospective cohort study. METHODS: The study assessed patients who had resident-performed cataract surgery between 2005 and 2013 and required return to the operating room for a second surgery on the same eye within 30 days. Preoperative and intraoperative risk factors were assessed. Outcome measures included corrected distance visual acuity (CDVA) at 1 year. RESULTS: A review of 6644 resident-performed cataract surgeries showed that 54 eyes (0.85%) of 54 patients required a return to the operating room within 30 days. The reoperation rate was higher in the first half of the academic year (1.18%) than in the second half (0.55%) (P = .004). The mean CDVA 1 year postoperatively was 20/40, with a loss of lines of vision in 4 eyes. The mean operative time was 59.23 minutes ± 35.05 (SD). A longer intraoperative time was predictive of a worse visual outcome (P < .01). CONCLUSIONS: Despite the need for reoperation within 30 days, most patients achieved improved visual acuity. The reoperation rate was significantly lower in the second half of the academic year. Increased operation times correlated with worse visual acuity independent of other variables.

Accuracy of toric intraocular lens axis alignment using a 3-dimensional computer-guided visualization system.

PURPOSE: To evaluate the accuracy of toric intraocular lens (IOL) alignment in femtosecond laser-assisted cataract surgery using the Truevision 3-dimensional (3-D) computer-guided visualization system compared with a manual marking method. SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. DESIGN: Retrospective comparative case series. METHODS: Preoperatively, all patients had corneal topography measurements with a color light-emitting diode topographer. The 3-D system used the anterior keratometry values to create an optimized plan for the toric IOL alignment. Intrastromal marks were created by the femtosecond laser at the intended toric meridian, guided by manual ink marks placed at the 3 o'clock and 9 o'clock limbus with the patient sitting upright. Intraoperatively, the 3-D system was used to align the IOL and measure the angular position of the femtosecond marks relative to the IOL meridian. Three weeks postoperatively, the manifest refraction, corrected distance visual acuity, and toric IOL alignment were recorded. RESULTS: The mean 3-D imaging error was -0.58 degrees ± 3.90 (SD) (range -9 to 5 degrees), and the mean manual ink error was -0.27 ± 3.65 degrees (range -8 to 5 degrees); neither was statistically significantly different from zero (P = .28 and P = .76, respectively). The mean absolute errors were 2.96 ± 2.54 degrees and 2.88 ± 2.18 degrees, respectively. CONCLUSION: The 3-D computer-guided system and manual marking combined with femtosecond laser marks were similar in accuracy for toric alignment. FINANCIAL DISCLOSURES: Dr. Wang received research support from Ziemer USA, Inc. Dr. Weikert is a consultant to Ziemer USA, Inc. Dr. Koch is a consultant to Alcon Laboratories, Inc., and Abbott Medical Optics, Inc., and received research support from Ziemer USA, Inc., i-Optics Corp, and Truevision Systems. None of the other authors has a financial or proprietary interest in any material or method mentioned.

Corneal cross-linking.

Since its inception in the late 1990s, corneal cross-linking has grown from an interesting concept to a primary treatment for corneal ectatic disease worldwide. Using a combination of ultraviolet-A light and a chromophore (vitamin B2, riboflavin), the cornea can be stiffened, usually with a single application, and progressive thinning diseases such as keratoconus arrested. Despite being in clinical use for many years, some of the underlying processes, such as the role of oxygen and the optimal treatment times, are still being worked out. More than a treatment technique, corneal cross-links represent a physiological principle of connective tissue, which may explain the enormous versatility of the method. We highlight the history of corneal cross-linking, the scientific underpinnings of current techniques, evolving clinical treatment parameters, and the use of cross-linking in combination with refractive surgery and for the treatment of infectious keratitis.

Repeatability of posterior and total corneal curvature measurements with a dual Scheimpflug-Placido tomographer.

PURPOSE: To evaluate the repeatability of the Galilei G4 dual Scheimpflug analyzer in measuring simulated keratometric, total, and posterior corneal curvature in normal and post-refractive surgery eyes. SETTING: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA. DESIGN: Prospective evaluation of diagnostic technology. METHODS: A single observer performed 3 consecutive measurements in 1 eye of each subject. The following were evaluated in both eyes and in eyes that had previous myopic excimer-laser surgery: (1) simulated keratometric corneal power and astigmatism, (2) total corneal power and astigmatism, and (3) posterior corneal power and astigmatism. Repeatability was assessed by calculating the within-subject standard deviation (Sw), coefficient of variation (CoV), and intra-class correlation coefficient (ICC). RESULTS: The study evaluated 41 normal eyes and 36 post-refractive surgery eyes. In normal eyes, the Sw was 0.08 diopters (D), 0.10 D, and 0.03 D for simulated keratometric, total, and posterior corneal power, respectively. The CoV ranged from 0.16% to 0.40%, and the ICC was 0.992 or more (P < .001) for all corneal powers. In post-refractive surgery eyes, the Sw was 0.09 D, 0.09 D, and 0.02 D for simulated keratometric, total, and posterior corneal power, respectively. The CoV ranged from 0.19% to 0.32%, and the ICC was 0.990 or more (P < .001) for all corneal powers. For posterior corneal astigmatism, the ICC was 0.814 and 0.886 for normal and post-refractive surgery eyes, respectively. CONCLUSIONS: In normal corneas and corneas that had undergone myopic excimer laser ablation, the dual Scheimpflug analyzer showed high intra-observer repeatability for simulated keratometric, total, and posterior corneal power measurements and moderate repeatability for posterior corneal astigmatism. FINANCIAL DISCLOSURE: Drs. Koch, Weikert, and Wang received research support from Ziemer USA, Inc. No other author has a financial or proprietary interest in any material or method mentioned.

Corneal scarring from laser in situ keratomileusis after epikeratoplasty: clinical and histopathologic analysis.

A 47-year-old woman required penetrating keratoplasty in the right eye after developing delayed visually significant corneal scarring bilaterally after laser in situ keratomileusis (LASIK) in 1997 following epikeratoplasty in 1987. Spectral domain ocular coherence tomography of the left cornea showed a 100 µm lenticule with a LASIK flap posterior to the host Bowman layer at 250 µm. Histopathology and electron microscopy of the right corneal button showed a 120 µm lenticule with a LASIK flap within the lenticule at 100 µm. Clinically significant scarring was present within the LASIK flap interface, within the lenticule stroma, and within the area of the underlying host Bowman layer. There were keratocytes at the junction between the LASIK flap and lenticule stromal bed. Although epikeratoplasty is no longer practiced, post-epikeratoplasty patients may present for refractive surgical options and LASIK carries significant risks for corneal scarring in these individuals, especially when using flap-creating devices that may create thin LASIK flaps.