To assess differences in corneal higher-order aberrations (i.e., HOAs) between six different types of irregular corneas (i.e, keratoconus (KC), keratoglobus (KG), pellucid marginal degeneration (PMD), laser-assisted in situ keratomileusis (LASIK), penetrating keratoplasty (PK), and intrastromal corneal ring segments (ICRS)). Corneal aberration data from the 3^rd and 4^th order together with secondary vertical and horizontal coma, and secondary spherical aberration were retrospectively retrieved from a corneal tomographer and compared between irregular cornea types and for 3-, 5-, and 7-mm pupil diameters. Significant differences were observed in vertical coma, oblique trefoil, secondary oblique astigmatism, primary spherical, and secondary spherical between irregular cornea types across all three pupil sizes (all p≤0.025). Vertical coma consistently exhibited the greatest magnitude of HOA across all irregular cornea types and pupil diameters. For the larger pupil diameters (5 and 7 mm), the 3rd order aberrations (mainly coma-like), the 4th order aberrations (mainly spherical-like), and total HOA RMS were significantly lower in the LASIK group compared to all other irregular cornea types (all p≤0.003). Additionally, at pupil sizes of 5 and 7 mm, the 3rd, 4th, coma-like, spherical-like, and total HOA RMS were significantly lower in KC compared to the ICRS and PK groups (all p≤0.01). Furthermore, the 4th, spherical-like, and total HOA RMS were significantly lower in KC compared to KG at pupil diameters of 3 and 7 mm, 5 and 7 mm, and 7 mm, respectively (all p≤0.03). Vertical coma was the most elevated HOA across all irregular cornea types and pupil diameters. Corneal aberrations were lower in LASIK and KC, and higher in KG and PK.

Background/Objectives: The objective of this study was to examine the trend of treatment zone (TZ) decentration over 12 months of orthokeratology (OK) wear using two Corneal Refractive Therapy (CRT) lens designs: standard (STD) and dual axis (DA). Methods: A prospective, randomized, longitudinal study was conducted at the Optometry Clinic of the Complutense University of Madrid. Subjects were randomly fitted with an STD design or DA design in one of the eyes. Refraction, uncorrected visual acuity (VA), and corneal topography were performed at baseline and after 1 night, 1 week, and 1, 3, 6, and 12 months of lens wear. Subjects requiring lens parameter adjustments or replacements after 3 months were excluded. Decentration was measured by subtracting pre-OK from post-OK tangential curvature maps at each visit, with decentration distance and corneal optical TZ being measured using MATLAB. Correlations between decentration and visual acuity (VA) were also analyzed. Results: A total of 30 healthy children (17 females and 13 males) with a mean age of 12.83 ± 2.42 years (range: 8–17 years) completed all the visits. No statistically significant differences (p > 0.05) were found between lens designs in horizontal, vertical, nor total decentration through the visits. However, for the STD design, horizontal and total decentration increased significantly at the last visit (p < 0.05). For the DA design, no significant differences were found over time (p > 0.05). No correlation was found between decentration and VA. Conclusions: Total decentration in both lens designs was similar throughout one year of follow-up. The standard design tended to decenter horizontally during the last 6 months, while the dual-axis design maintained consistent decentration throughout the year.

Background/Objectives: To examine the trend of treatment zone (TZ) decentration over 12 months of Orthokeratology (OK) wear using two corneal refractive therapy (CRT) lens designs: standard (STD) and dual axis (DA). Methods: A prospective, randomized, longitudinal study was conducted at the Optometry Clinic of the Complutense University of Madrid. Subjects were fitted with STD or DA designs in one of the eyes, randomly. Refraction, uncorrected visual acuity (VA) and corneal topography were performed at baseline, 1-night, 1-week, 1-, 3-, 6- and 12-month of lens wear. Subjects requiring lens parameter adjustments or replacements after 3 months were excluded. Decentration was measured by subtracting pre-OK from post-OK tangential curvature maps at each visit, with decentration distance and corneal optical TZ measured using MATLAB. Correlations between decentration and visual acuity (VA) were also analyzed. Results: Thirty healthy children completed all the visits (17 female and 13 male) with a mean age of 12.83±2.42 years (range: 8–17 years). No statistically significant differences (p>0.05) were found either in the horizontal, vertical nor total decentration through the visits between lens designs. However, for STD design horizontal and total decentration increased significantly at the last visit (p0.05). No correlation was found between decentration and VA. Conclusions: Total decentration in both lens designs was similar throughout one year of follow-up. The standard design tended to decenter horizontally during the last 6 months, while the dual-axis design maintained consistent decentration throughout the year.

Background/Objectives: High accommodative lag and relative peripheral hyperopic defocus during near work have been proposed as potential contributors to myopia progression. Orthokeratology (OK) reshapes the cornea to provide central correction while inducing peripheral myopic defocus. This prospective 12-month study aimed to evaluate longitudinal changes in peripheral refraction, accommodative lag, and axial length (AL) in myopic children treated with OK. Methods: Children aged 7 to 17 years with low-to-moderate myopia were fitted with spherical (CRT™ STD) or toric (CRT™ DA) OK lenses and followed for 12 months. Horizontal peripheral refraction (vector M, J0, J45) up to ±30°, accommodative lag and non-cycloplegic AL were measured. Results: Forty-seven participants completed the study. Mean AL increased from 24.76 ± 0.87 mm at baseline to 24.86 ±0.85 mm at 12 months (p < 0.001). OK induced a stable, symmetrical redistribution of relative peripheral myopic defocus across visits. The toric design showed more consistent significant variations in the J0 astigmatic component across eccentricities. No significant correlations were found between AL elongation and changes in peripheral refraction (p = 0.194) or accommodative lag (p > 0.05) in the overall sample. However, subjects in the lag variation group showed significant AL increases (p < 0.05), while those in the no lag variation group did not (p > 0.05). Conclusions: OK consistently induces a stable pattern of peripheral myopic defocus. While peripheral defocus and accommodative lag do not linearly correlate with global axial growth, accommodative behavior may be associated with individual differences in axial growth. Biometry remains important for monitoring treatment outcomes.