Search Results

Abstract

PURPOSE: To evaluate the reliability and comparability of a Scheimpflug-based tomographer relative to a Placido-based topographer and specular microscopy in healthy eyes.
METHODS: This cross-sectional study included 40 patients (80 eyes). Each eye underwent randomized imaging with a Scheimpflug-based tomographer, a Placido-based topographer, and Tomey EM-4000 specular microscopy. Three acquisitions per device were obtained. For interdevice comparisons, the best-quality scan per eye/device was selected, whereas all three scans were used for intradevice repeatability analyses. Unreliable scans were repeated (up to five attempts) and excluded if acceptable quality was not achieved, resulting in variable denominators. Between-device comparisons were performed using generalized estimating equations with participant-level clustering and robust standard errors and were supplemented by Bland–Altman analysis.
RESULTS: The effective sample size varied by parameter (independent summaries: 59–67 eyes; paired comparisons: 48–51 eyes). In paired-eye analyses, the Scheimpflug-based tomographer measured slightly higher keratometry values than the Placido-based topographer (K1: 43.95 vs. 43.78 D, p=0.003; K2: 44.91 vs 44.73 D, p=0.002), more negative Q-values (p=0.001), smaller photopic pupil diameter (p<0.001), and shorter kappa distance (p<0.001). Mean absolute differences were 0.32 D for K1 and 0.30 D for K2, with high dispersion for angular metrics (kappa angle coefficient of variation: 195%).
CONCLUSIONS: The Scheimpflug-based tomographer provides reproducible corneal measurements in healthy eyes. However, systematic differences relative to the Placido-based topographer—particularly for keratometry, asphericity, and pupil and kappa metrics—suggest limited interchangeability. Consistent device use is recommended when these parameters inform clinical decision-making.

Keywords: Scheimpflug tomography; Placido topography; Specular microscopy; keratometry; Corneal imaging; Refractive surgical procedures; Lenses, intraocular

Abstract

PURPOSE: To quantitatively assess changes in central corneal sensitivity after phacoemulsification and to characterize recovery patterns up to 90 days using standardized esthesiometry.
METHODS: This prospective observational study included 44 patients (88 eyes) undergoing uncomplicated phacoemulsification with intraocular lens implantation. Central corneal sensitivity was measured using a Cochet-Bonnet^® esthesiometer preoperatively and at 30 and 90 days postoperatively. Repeated-measures data were analyzed using Friedman and Wilcoxon signed-rank tests (p<0.05). Inter-eye differences were assessed with a paired Wilcoxon test. Individual changes from baseline (Δ30, Δ90) were calculated, and 90-day recovery was categorized according to thresholds aligned with the 5-mm device resolution. Spearman correlation was used to explore associations between age and Δ90.
RESULTS: Corneal sensitivity decreased after surgery. In right eyes, mean sensitivity declined from 41.14 ± 7.77 mm at baseline to 36.82 ± 9.03 mm at 30 days and partially recovered to 38.64 ± 7.73 mm at 90 days. In left eyes, sensitivity decreased from 44.11 ± 6.29 mm to 37.39 ± 9.05 mm at 30 days and recovered to 41.82 ± 7.63 mm at 90 days. Left eyes showed higher sensitivity than right eyes at baseline (p=0.023) and at 90 days (p=0.018). At 90 days, complete or near-complete recovery (within ± 5 mm of baseline) occurred in 73.2% of right eyes and 78.0% of left eyes, while improvement above baseline (≥ +5 mm) occurred in 7.3% and 4.9%, respectively. Age showed weak, nonsignificant correlations with Δ90 (p=−0.14 to −0.19; p>0.2).
CONCLUSION: Phacoemulsification with a 2.75-mm clear corneal incision leads to a temporary reduction in central corneal sensitivity, with partial recovery by 90 days. Recovery patterns vary among individuals, highlighting the value of postoperative sensitivity monitoring to identify atypical trajectories and guide ocular surface care during visual rehabilitation.

Keywords: Phacoemulsification; Cornea/innervation; Ophthalmic nerve/physiology; Optometry/instrumentation; Diagnostic techniques, ophthalmological; Neural regeneration; Visual rehabilitation.