Advanced epithelial mapping for refractive surgery.

One of the leading challenges in refractive surgery today is the presence of underlying subclinical early-stage keratoconus (KC), which can lead to iatrogenic post laser in situ keratomileusis ectasia. Timely detection of this condition could aid the refractive surgeons in better decision-making. This includes being able to defer refractive surgery in subclinical cases as well as providing treatment for the same in the form of appropriate corneal collagen crosslinking treatments. Corneal topography is considered the gold standard for the diagnosis of corneal ectatic disorders. However, there is a likelihood that topographers are overlooking certain subclinical cases. The corneal epithelium is known to remodel, which may mask underlying stromal irregularities. Imaging and analyzing corneal epithelium and stroma independently will undoubtedly open newer avenues to supplement our understanding of postrefractive surgery outcomes and KC. This review encapsulates the various Optical coherence tomography-based epithelial mapping devices particularly RTVue (Optovue, Fremont, USA) and MS-39 (Costruzione Strumenti Oftalmici, Florence, Italy) in terms of their utility in these conditions. It will help guide the clinician on how including an epithelial mapping in clinical practice can aid in diagnosis, management, and interpretation of outcomes both for refractive surgery as well as KC.

Correction of preexisting astigmatism by penetrating arcuate keratotomy in femtosecond laser-assisted cataract surgery.

Purpose: To evaluate the astigmatism correcting effect of penetrating arcuate keratotomy (AK) done during femtosecond laser-assisted cataract surgery (FLACS). Methods: In this nonrandomized prospective study, 80 eyes of 70 patients were studied. The study included patients who underwent combined FLACS and AK, with corneal astigmatism ranging from 0.4 to 1.5 diopters (D). Femtosecond laser-assisted penetrating arcuate keratotomies were created at 8 mm optical zone at 80% depth and were centered at the limbus. Keratometric astigmatism was measured prior to and 3 months post-surgery. Vector analysis was performed using Power vector analysis method. Results: The mean preoperative keratometric astigmatism without accounting for axis was 0.85 ± 0.27 D, which reduced significantly to 0.47 ± 0.27 D at 3-month follow-up. The mean astigmatism correction attained without accounting for axis was 0.38 ± 0.32 D. The vector corrected mean preoperative astigmatism was 0.85 ± 0.27 D which reduced significantly to 0.50 ± 0.31 D postoperatively (P < 0.001, 95% CI). Vector corrected mean astigmatism correction attained was 0.35 ± 0.38 D. There were no significant intraoperative or postoperative complications. Conclusion: Preexisting astigmatism can be tackled effectively with penetrating AK during FLACS although under correction is observed with present nomograms. Further refinements may achieve better correction.

Wavefront-Guided LASIK Has Comparable Ocular and Corneal Aberrometric Outcomes but Better Visual Acuity Outcomes Than SMILE in Myopic Eyes.

PURPOSE: To compare ocular and corneal aberrometric outcomes of wavefront-guided (WFG) LASIK and small incision lenticule extraction (SMILE). METHODS: This was a prospective, interventional study where 48 eyes (24 patients) underwent SMILE (Carl Zeiss Meditec, Jena, Germany) and 58 eyes (29 patients) underwent WFG LASIK (Abbott Medical Optics, Abbott Park, IL). Visual acuity and ocular surface disease index were assessed preoperatively and 1 and 3 months postoperatively. Corneal topography and anterior aberrations were assessed with the Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) and iTrace (Tracey Technologies, Houston, TX), respectively. Ocular aberrations were also assessed with the iTrace. RESULTS: Safety and efficacy indexes of WFG LASIK (0.99 and 1.01, respectively) and SMILE (1.01 and 1.13, respectively) were comparable, although WFG LASIK was better (P < .0001). At 3 months postoperatively, all eyes in both groups achieved an uncorrected distance visual acuity of 20/20 or better. Further, 74.14% and 45.83% of the eyes in the WFG LASIK and SMILE groups, respectively, achieved uncorrected distance visual acuity of 20/16 (P = .003). The Pentacam reported an increase in root mean square of higher order aberrations (diameter of 4 mm and 6th order Zernike) and coma with a decrease in spherical aberration in both groups (P < .001). Corneal aberrations from the iTrace also did not yield any definitive differences between the treatments. However, changes in ocular aberrations were clinically insignificant at 3 months after both treatments. The ocular surface disease index increased mildly after WFG LASIK (P > .05) but was unchanged after SMILE. CONCLUSIONS: WFG LASIK and SMILE had similar aberrometric outcomes but WFG LASIK had better postoperative visual acuity. Surgeon experience, internal aberrations, small pupil size, and wound healing can enable similar outcomes in both procedures. [J Refract Surg. 2018;34(8):527-532.].

Repeatability of a Commercially Available Adaptive Optics Visual Simulator and Aberrometer in Normal and Keratoconic Eyes.

PURPOSE: To evaluate the repeatability of aberration measurement obtained by a Hartmann-Shack aberrometer combined with a visual adaptive optics simulator in normal and keratoconic eyes. METHODS: One hundred fifteen normal eyes and 92 eyes with grade I and II keratoconus, as per the Amsler-Krumeich classification, were included in the study. To evaluate the repeatability, three consecutive measurements of ocular aberrations were obtained by a single operator. Zernike analyses up to the 5th order for a pupil size of 4.5 mm were performed. Statistical analyses included the intraclass correlation coefficient (ICC) and within-subject standard deviation (SD). RESULTS: For intrasession repeatability, the ICC value for sphere and cylinder was 0.94 and 0.93 in normal eyes and 0.98 and 0.97 in keratoconic eyes, respectively. The ICC for root mean square of higher order aberrations (HOARMS) was 0.82 in normal and 0.98 in keratoconic eyes. For 3rd order aberrations (trefoil and coma), the ICC values were greater than 0.87 for normal eyes and greater than 0.92 for keratoconic eyes. The ICC for spherical aberration was 0.92 and 0.90 in normal and keratoconic eyes, respectively. CONCLUSIONS: Visual adaptive optics provided repeatable aberrometry data in both normal and keratoconic eyes. For most of the parameters, the repeatability in eyes with early keratoconus was somewhat better than that for normal eyes. The repeatability of the Zernike terms was acceptable for 3rd order (trefoil and coma) and spherical aberrations. Therefore, visual adaptive optics was a suitable tool to perform repeatable aberrometric measurements. [J Refract Surg. 2017;33(11):769-772.].

Topography-guided neutralization technique for the management of flap complication in laser in situ keratomileusis.

A 29-year-old male was referred following a flap loss after the creation of a thin, irregular flap with a visual acuity of logMAR 0.1 with -2.0 DS-2.75 DC × 175°. Corneal topography and anterior segment optical coherence tomography revealed an irregular corneal curvature and epithelial profile. Phototherapeutic keratectomy (PTK) followed by Topography - Guided Custom Ablation Treatment (TCAT), as a modification of the topographic neutralization technique protocol, was planned to regularize the corneal surface and treat the residual refractive error. Postoperatively, the patient showed a best-corrected visual acuity of logMAR 0 with a refractive error of -1 DC × 90°. Regularization of topography and epithelial thickness was seen along with a reduction in astigmatism and higher order aberrations. We report the use of PTK followed by TCAT as a novel method to treat a case of intraoperative flap loss during laser in situ keratomileusis.