Enhanced Tomographic Assessment to Detect Corneal Ectasia Based on Artificial Intelligence.

PURPOSE: To improve the detection of corneal ectasia susceptibility using tomographic data. DESIGN: Multicenter case-control study. METHODS: Data from patients from 5 different clinics from South America, the United States, and Europe were evaluated. Artificial intelligence (AI) models were generated using Pentacam HR (Oculus, Wetzlar, Germany) parameters to discriminate the preoperative data of 3 groups: stable laser-assisted in situ keratomileusis (LASIK) cases (2980 patients with minimum follow-up of 7 years), ectasia susceptibility (71 eyes of 45 patients that developed post-LASIK ectasia [PLE]), and clinical keratoconus (KC; 182 patients). Model accuracy was independently tested in a different set of stable LASIK cases (298 patients with minimum follow-up of 4 years) and in 188 unoperated patients with very asymmetric ectasia (VAE); these patients presented normal topography (VAE-NT) in 1 eye and clinically diagnosed ectasia in the other (VAE-E). Accuracy was evaluated with ROC curves. RESULTS: The random forest (RF) provided highest accuracy among AI models in this sample with 100% sensitivity for clinical ectasia (KC+VAE-E; cutoff 0.52), being named Pentacam Random Forest Index (PRFI). Considering all cases, the PRFI had an area under the curve (AUC) of 0.992 (94.2% sensitivity, 98.8% specificity; cutoff 0.216), being statistically higher than the Belin/Ambrósio deviation (BAD-D; AUC = 0.960, 87.3% sensitivity, 97.5% specificity; P = .006, DeLong's test). The optimized cutoff of 0.125 provided sensitivity of 85.2% for VAE-NT and 80% for PLE, with 96.6% specificity. CONCLUSION: The PRFI enhances ectasia diagnosis. Further integrations with corneal biomechanical parameters and with the corneal impact from laser vision correction are needed for assessing ectasia risk.

Non-penetrating femtosecond laser intrastromal astigmatic keratotomy in patients with mixed astigmatism after previous refractive surgery.

PURPOSE: To report the outcomes of the correction of mixed astigmatism with non-penetrating femtosecond laser intrastromal astigmatic keratotomy in patients with previous refractive surgery. METHODS: One hundred twelve eyes that had low mixed astigmatism after excimer laser surgery, refractive lens exchange, or phakic intraocular lens implantation underwent intrastromal astigmatic keratotomy using paired symmetrical non-penetrating intrastromal arcuate keratotomies created 60 µm from the surface to 80% depth at 7 mm diameter. Outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), subjective refraction, and keratometry. A coupling ratio was calculated to assess the change in spherical equivalent. Average follow-up was 7.6 ± 2.9 months. Patients were divided into two groups: no excimer laser corneal ablation and previous excimer laser surgery. Preoperative and postoperative data were compared between groups and analyses were performed on the whole group of eyes. RESULTS: Overall, the mean UDVA improved significantly from 0.18 ± 0.14 to 0.02 ± 0.12 logMAR (6/9 to ≈6/6 Snellen) (P < .01). The mean absolute subjective cylinder decreased significantly from 1.20 ± 0.47 diopters (D) preoperatively to 0.55 ± 0.40 D postoperatively (P < .01). Subjective sphere decreased significantly from +0.61 ± 0.33 to +0.17 ± 0.36 D (P < 0.01). The mean CDVA was -0.03 ± 0.08 logMAR (≈ 6/6 Snellen) preoperatively and -0.05 ± 0.09 logMAR (≈ 6/5 Snellen) postoperatively (P = .06). The coupling ratio was 0.92 ± 0.45. There was no statistically significant difference in the preoperative and postoperative sphere, cylinder, UDVA, CDVA, and coupling ratio between groups. No surgical complications occurred. CONCLUSIONS: Femtosecond laser intrastromal astigmatic keratotomy was effective at reducing refractive error in patients where other surgical options were exhausted. Predictability and efficacy could be improved with nomogram refinement.

Early flap displacement after LASIK.

PURPOSE: To evaluate the risks of flap displacement after LASIK. DESIGN: Retrospective case series. PARTICIPANTS: We included 41 845 consecutive adults who underwent LASIK surgery at Optical Express in the United Kingdom, including 81 238 eyes, of which 14 555 were hyperopic and 66 681 myopic or mixed astigmatic. We treated 57 241 eyes with the IntraLase FS-60 femtosecond laser and 23 997 with the Moria S.A. ONE Use-Plus automated microkeratome. METHODS: We calculated the incidence of all flap displacements in the study population during an observational time period of ≥12 months after surgery. Independent variables were entered into logistic regression models to identify risk factors. Postoperative outcomes were assessed. MAIN OUTCOME MEASURES: The incidence and odds ratios (OR) of flap displacement in the study population and in categories of refractive error and flap surgery technique. RESULTS: The incidence of flap displacements was 10 in 81 238 LASIK procedures (0.012%), including 8 hyperopic eyes (0.055%) and 2 myopic eyes (0.003%). All flap displacements occurred within 48 hours of surgery and none were preceded by ocular trauma. They were classified as "early flap displacements" (EFD). The incidence of EFD after microkeratome surgery was 0.033% (n = 8), and after femtosecond laser it was 0.003% (n = 2). In hyperopic eyes having microkeratome surgery, the incidence was 0.179% (n = 7). In a logistic regression model, the strongest predictor of EFD after LASIK was hyperopia, recording an OR of 19.29 (P<0.001). The OR of developing an EFD after microkeratomy was 10.53 times higher than after femtosecond laser (P<0.005). In hyperopes, the OR of an EFD was 18.87 times higher after microkeratomy than after femtosecond treatment. Four of 10 displaced flaps needed secondary surgery, and 1 eye lost 2 lines of best-corrected visual acuity. CONCLUSIONS: The incidence of flap displacements during a 12-month period after LASIK was extremely low (0.012%). Although the small number of displacements with the femtosecond laser limits conclusions, the risk of EFD was higher after microkeratome surgery than femtosecond laser.

Why preoperative acuity predicts postoperative acuity in wavefront-guided LASIK.

PURPOSE: To critically evaluate the following clinical wisdom regarding custom (wavefront-guided) laser in situ keratomileusis (LASIK) that subjects with better-than-average best-corrected visual acuity (BCVA) before surgery have a greater risk of losing BCVA postoperatively than do subjects with worse-than-average BCVA before surgery. METHODS: High contrast BCVA was measured once before and 3 months after custom LASIK in one eye of 79 subjects. Preoperative spherical equivalent refractive error ranged between -1.00 and -10.38 D. The sample was divided into one of two subsamples: eyes that had better-than-average preoperative BCVA (<-0.11 logMAR) and eyes that had average or worse-than-average preoperative BCVA (≥-0.11 logMAR). Controls were implemented for retinal magnification and for the statistical phenomenon of regression to the mean of the preoperative acuity measurement. RESULTS: On average, for the entire sample, moving the correction from the spectacle plane to the corneal plane increased letter acuity 4.7% (1 letter, 0.02 logMAR). For each subsample, the percentage regression to the mean was 57.24%. After correcting for magnification effects and regression to the mean, eyes with better-than-average preoperative acuity had a small but significant gain in acuity (∼1 letter, p = 0.040) that was nearly identical to the gain for eyes with worse-than-average preoperative acuity (∼1.5 letters, p = 0.002). CONCLUSIONS: Custom LASIK produced a statistically significant gain in visual acuity after correction for magnification effects. Dividing the sample into two subsamples based on preoperative acuity confirmed the common clinical observation that eyes with better-than-average acuity tend to remain the same or lose acuity, whereas eyes with worse-than-average acuity tend to gain acuity. However, when only one acuity measurement is taken at a single time point and the sample is subsampled nonrandomly, this clinical observation is due to a statistical artifact (regression to the mean) and is not attributable to the surgery.

Comparison of night driving performance after wavefront-guided and conventional LASIK for moderate myopia.

PURPOSE: To compare preoperative and postoperative changes in simulated night driving performance after wavefront-guided (wLASIK) and conventional LASIK (cLASIK) for the treatment of moderate myopia. DESIGN: Retrospective, comparative study. PARTICIPANTS: All eyes of subjects with a preoperative manifest spherical equivalent (MSE) between -4.50 and -6.00 who underwent night driving simulator (NDS) testing from 2 clinical trials were entered into the study. This comprised 38 cLASIK patients (62 eyes; mean -5.46 diopters [D] MSE) and 21 wLASIK patients (36 eyes, mean -5.20 D MSE). METHODS: Patients' records were reviewed from 2 LASIK clinical trials that had similar enrollment criteria. One trial treated patients with conventional LASIK using a bladed microkeratome (cLASIK) and the other treated with a wavefront-guided profile using a femtosecond laser (wLASIK). In both trials, patients with moderate myopia were asked to participate in NDS testing. MAIN OUTCOME MEASURES: The detection and identification distances of road hazards were measured with and without a glare source before and 6 months after LASIK. Each eye was tested independently in best-corrected trial frames by a masked operator. RESULTS: In every category, there was a mean reduction in the preoperative to postoperative NDS performance after cLASIK (mean change, -21.3 to -27.9 ft, -6.5 to -8.5 m; 95% confidence interval [CI], -12.0 to -41.3 ft, -3.7 to -12.6 m); there was a corresponding mean improvement after wLASIK (mean change +15.0 to +29.1 ft, +4.6 to +8.9 m; 95% CI, +8.3 to +41.5 ft, +2.5 to +12.6 m). Significant differences between cLASIK and wLASIK NDS performance was observed in every category (P<0.;01, Tukey's honest significant difference for unequal numbers). A clinical relevant loss of NDS performance (>0.5 seconds) was observed in 32% to 38% of cLASIK eyes for all tasks, whereas only 0% to 3% of eyes had this loss after wLASIK. Between 2% and 7% of cLASIK eyes and 11% and 31% of eyes had a significant postoperative improvement in NDS performance in every task. CONCLUSIONS: Wavefront-guided LASIK to correct myopia combined with a femtosecond laser flap significantly improved mean night driving visual performance and was significantly better than cLASIK using a mechanical keratome.