SMILE after DALK to reduce residual refraction: two-year results.

PURPOSE: To determine the two-year results of small incision lenticule extraction (SMILE) for correcting post-keratoplasty myopia and myopic astigmatism. METHODS: In this case-series study, 10 eyes of 10 patients with a 6- to 10-year history of successful deep lamellar keratoplasty (DALK) underwent SMILE using the VisuMax laser platform. Ophthalmologic examinations and visual acuity and refraction measurement were taken pre- and 1, 3, 6, 12, and 24 months postoperatively. The Pentacam and Sirius imaging were done in the first and last follow-up sessions. RESULTS: The mean age of the patients was 39.60 ± 7.86 years. Six subjects were male. Two years after SMILE, the mean improvement in UDVA and CDVA was 3.60 ± 1.84 (P < 0.001) and 1.60 ± 2.91 (P = 0.231) LogMAR, respectively. The mean decrease in spherical equivalent, spherical error, and cylinder power was 1.92 ± 1.96 diopter (D) (P = 0.013), 0.70 ± 3.05D (P = 0.213), and 2.42 ± 2.91D (P = 0.024), respectively. The vector mean target-induced astigmatism, surgical-induced astigmatism, and difference vector were 1.30D@44˚, 1.11D@24˚, and 0.86D@73˚, respectively. Two years after SMILE, vertical coma, horizontal coma, and spherical aberration increased by 0.44 ± 0.51, 0.23 ± 0.32, and 0.02 ± 0.16 µm, respectively, (all P > 0.05) while trefoil reduced by 0.29 ± 0.75 µm (P = 0.428). CONCLUSION: SMILE can be an effective procedure for reducing refraction and astigmatism after DALK in patients with moderate myopia and moderate to severe astigmatism and improves the visual acuity in these patients. Axis rotation during surgery may result in under-correction of astigmatism. Refinement of SMILE treatment nomogram for post-DALK cases seems necessary.

Early diagnosis of subclinical keratoconus by wavefront parameters using Scheimpflug, Placido and Hartmann-Shack based devices.

PURPOSE: To compare the accuracy of three devices (Pentacam, Sirius and OPD-Scan III) to differentiate subclinical keratoconus from normal corneas by wavefront parameters. METHODS: Two hundred and seventeen patients were enrolled in three groups [68 normal, 79 subclinical keratoconus (SKCN) and 70 KCN eyes] in this prospective diagnostic test study. Wavefront indices were evaluated between the groups using Pentacam, Sirius and OPD-Scan III. The accuracy of the parameters was determined by measuring the area under the receiver operating characteristic curve (AUC) for each group. RESULTS: Front Baiocchi-Calossi-Versaci (BCV) index with Sirius (sensitivity = 87.7%, specificity = 83%, AUC = 0.887), front Vertical Coma (Z3-1) with Pentacam (sensitivity = 75%, specificity = 100%, AUC = 0.857) and Corneal Z3-1 with OPD-Scan III (sensitivity = 100%, specificity = 78.6%, AUC = 0.857) had the highest AUC values for the diagnosis of subclinical KCN. In the KCN group, the highest AUC values were obtained for front higher-order aberration (HOA), front/back Z3-1 and front Secondary Vertical Coma (Z5-1) with Pentacam (sensitivity = 100%, specificity = 100%, AUC = 1.00 for all three), front root mean square values per unit area (RMS/A), HOA, Residual HOA, BCV, RMS Trefoil and RMS Coma with Sirius (sensitivity = 100%, specificity = 100%, AUC = 1.00 for all) and Corneal HOA, RMS total Coma and Z3-1 with OPD-Scan III (sensitivity = 100%, specificity = 93%, AUC = 0.96 for all three). CONCLUSION: Corneal wavefront indices generated from different devices have acceptable validity for differentiating normal cornea from the early form of KCN, and this can be very useful for preoperative screening before refractive surgery. The front BCV with Sirius was the most accurate parameter for diagnosis of SKCN followed by Z3-1 with Pentacam and OPD-Scan III.

Ray Tracing versus Thin-Lens Formulas for IOL Power Calculation Using Swept-Source Optical Coherence Tomography Biometry.

Purpose: To evaluate the ray tracing method's accuracy employing Okulix ray tracing software and thin-lens formulas to calculate intraocular lens (IOL) power using a swept-source optical coherence tomography (SS-OCT) biometer (OA2000). Methods: A total of 188 eyes from 180 patients were included in this study. An OA-2000 optical biometer was used to collect biometric data. The predicted postoperative refraction based on thin-lens formulas including SRK/T, Hoffer Q, Holladay 1, and Haigis formulas and the ray tracing method utilizing the OKULIX software was determined for each patient. To compare the accuracy of approaches, the prediction error and the absolute prediction error were determined. Results: The mean axial length (AL) was 23.66 mm (range: 19-35). In subgroup analysis based on AL, in all ranges of ALs the ray tracing method had the lowest mean absolute error (0.56), the lowest standard deviation (SD; 0.55), and the greatest proportion of patients within 1 diopter of predicted refraction (87.43%) and the lowest absolute prediction error compared to the other formulas (except to SRK/T) in the AL range between 22 and 24 mm (all P < 0.05). In addition, the OKULIX and Haigis formulas had the least variance (variability) in the prediction error in different ranges of AL. Conclusion: The ray tracing method had the lowest mean absolute error, the lowest standard deviation, and the greatest proportion of patients within 1 diopter of predicted refraction. So, the OKULIX software in combination with SS-OCT biometry (OA2000) performed on par with the third-generation and Haigis formulas, notwithstanding the potential for increased accuracy in the normal range and more consistent results in different ranges of AL.

Diurnal Variations in Intraocular Pressure, Central Corneal Thickness, and Macular and Retinal Nerve Fiber Layer Thickness in Diabetics and Normal Individuals.

PURPOSE: To evaluate diurnal variations in intraocular pressure (IOP), central corneal thickness (CCT), and macular and retinal nerve fiber layer (RNFL) thickness in diabetic patients and normal individuals. METHODS: This study included 11 diabetic patients with macular edema and 11 healthy individuals. IOP, CCT, and macular and RNFL thickness were measured every 3 hours on a single day between 9 AM and 6 PM. Diurnal variations in IOP, CCT, total macular volume (TMV), central macular thickness (CMT), average macular thickness (AMT), and RNFL thickness were measured. RESULTS: None of the parameters showed a significant absolute or relative change over the course of the day. However, the following non-significant changes were observed. In the control group, all parameters demonstrated the highest values at 9 AM. The lowest IOP, TMV and AMT occurred at 12 PM; lowest CCT and RNFL at 6 PM; and the lowest CMT at 3 PM. Diabetic subjects had the highest values of RNFL, CMT and TMV at 9 AM, and that for IOP, CCT and AMT at 6 PM. The lowest RNFL and CMT values occurred at 6 PM; lowest IOP at 12 PM; and the lowest CCT, TMV and AMT were observed at 3 PM. In the diabetic group, TMV, CMT, AMT and CCT were significantly higher and RNFL was significantly lower than the control group at all time points (all P- values < 0.05). CONCLUSION: While there were slight decreases in IOP, RNFL thickness and CMT during the day, these changes were not significant between 9 AM and 6 PM and probably do not affect the interpretation of measurements.

Bilateral Keratoconus and Corneal Hydrops Associated with Eye Rubbing in a 7-year-old Girl.

PURPOSE: To report a young child with bilateral keratoconus in the context of vernal keratoconjunctivitis (VKC) who developed bilateral corneal hydrops associated with eye rubbing, and to discuss the pathogenesis and review the pertinent literature. CASE REPORT: A seven-year-old girl with VKC and asymmetric keratoconus developed corneal hydrops due to habitual eye rubbing. Corneal edema subsided within 16 weeks in her right eye and 9 weeks in the left eye with subsequent corneal scarring. CONCLUSION: Continuous mechanical trauma, such as eye rubbing, plays a significant role in the pathogenesis of keratoconus and subsequent hydrops even in childhood.

Intraretinal foreign bodies: surgical techniques and outcomes.

PURPOSE: To report the clinical features of eyes with intraretinal foreign bodies (IRFBs) and to evaluate the results of surgical management in these eyes. METHODS: Hospital records of 34 eyes of 33 patients with IRFBs were reviewed. All eyes underwent pars plana vitrectomy to remove the foreign bodies using intraocular forceps or by magnetic extraction. RESULTS: All patients were male with mean age of 28±12.3 years and were followed for a mean period of 24.5±2.3 months. The IRFBs were ferromagnetic in 29 (85.3%) cases and were removed using an external magnet in 13 eyes (38.4%) or intraocular forceps in 21 eyes (61.6%). Laser photocoagulation was performed around the IRFB prior to surgery in 7 (20.6%) eyes. Macular pucker and scars developed in 8 (23.5%) eyes and retinal breaks posterior to the sclerotomy were formed in 12 eyes (35.3%) postoperatively. Final visual acuity was 20/40 or better in 12 (35.3%) eyes and 20/200 or better in 23 (67.7%) eyes. Final visual acuity of 20/200 or better had no significant relationship with the site, size, or type of the IRFB or with the interval from trauma to surgery. CONCLUSION: Despite the complexity of surgical management of IRFBs, anatomic and visual outcomes of vitreoretinal surgery in these cases are generally good. The appropriate route of removal may be determined by the type, size, and site of the IRFB. Removal of magnetic IRFBs using external magnets versus intraocular forceps seems to entail comparable results.