[Study on Corneal-Scleral Morphology guided by Pentacam corneal-scleral profile analysis module for scleral lens fitting in low to moderate myopia].

Objective: To investigate the anterior segment parameters and morphological characteristics of corneoscleral topography in patients with simple refractive errors, so as to provide a basis for the design and fitting of scleral lenses. Methods: This was a cross-sectional study. A total of 41 adult patients (82 eyes) with low to moderate myopia who visited the Contact Lens Clinic of the Eye Hospital Affiliated to Nanjing Medical University from August to September 2023 were enrolled, including 28 females and 13 males, with an age of (26.20±5.44) years. All patients underwent routine ophthalmic examinations. In addition, the Corneal-Scleral Profile (CSP) Analysis Module of the Pentacam anterior segment analysis system was used to obtain sagittal plane images and corneoscleral topographic maps within a diameter of 18.0 mm in the anterior ocular segment. Data such as sagittal height (SH), corneal angle (CA), and scleral angle (SA) at chord lengths (CL) of 10.0, 12.8, 13.5, 15.0, 16.0, and 17.0 mm were collected respectively. After adjusting for the non-independence of binocular data using Generalized Estimating Equations, univariate linear regression analysis was performed to explore the quantitative relationship between chord length and mean sagittal height. Results: There were no statistically significant differences in corneoscleral sagittal height between the right and left eyes at different chord lengths and orientations (all P>0.05). At the chord length of 10.0 mm, the superior sagittal height was the highest in both eyes [right eye: (1 818.00±12.13) μm, left eye: (1 815.41±14.23) μm], and the temporal sagittal height was the lowest [right eye: (1 724.68±9.72) μm, left eye: (1 717.12±10.82) μm]. For chord lengths of 12.8 mm and above, the inferior sagittal height was the highest and the nasal sagittal height was the lowest; moreover, the nasal sagittal height was smaller than the temporal one, and the superior sagittal height was smaller than the inferior one (P<0.05). At all chord lengths, the nasal corneoscleral angle of both eyes was smaller than the temporal one (P<0.05). At chord lengths of 10.0, 12.8, 13.5, 15.0, 16.0, and 17.0 mm, the proportions of eyes with corneoscleral sagittal height difference>150 μm between orthogonal meridians were 2.44% (2/82), 18.29% (15/82), 26.83% (22/82), 75.61% (62/82), 87.80% (72/82), and 92.68% (76/82), respectively. Taking the mean sagittal height as the dependent variable (y) and chord length as the independent variable (x), the univariate linear regression equations after adjusting for relevant factors were: right eye: y=-2 663.71+434.86x (adjusted R²=0.99), left eye: y=-2 516.56+422.82x (adjusted R²=0.99) (both P<0.001). Conclusions: The corneoscleral morphology of low to moderate myopic eyes presents non-rotational symmetry, which is characterized by a flatter nasal sclera than the temporal side, significant differences in sagittal height between the superior and inferior regions, and increasing sagittal height difference with longer chord length. There is a strong linear correlation between chord length and mean sagittal height. These morphological characteristics can provide a basis for the design and fitting of scleral lenses.