Measurements of Anterior and Posterior Corneal Curvatures with OCT and Scheimpflug Biometers in Patients with Low Total Corneal Astigmatism

Background: Posterior keratometry measurements are evolving features of the optical biometers. The differences between devices have bigger impact for the low astigmatism values. The majority of adults present the corneal astigmatism below 1.5 D. Objectives: To compare the total corneal astigmatism measured with two different technologies in cataract patients with corneal astigmatism below 1.5 D. Material and Methods: Three automated exams were performed on each of the two devices: swept-source optical coherence tomography (SS-OCT) and Scheimpflug biometers. The anterior and total corneal astigmatism and power were analysed. Statistical comparisons were performed for within-subject standard deviation, repeatability, Bland–Altman and vector analysis. Results: Twenty-nine eyes of twenty-seven patients were included. The limits of agreement between anterior and total corneal astigmatism were narrower for the SS-OCT than for the Scheimpflug biometer (−0.16 to 0.29 D and −0.40 to 0.39 D, respectively). The >0.5 D difference between SS-OCT and Scheimpflug total astigmatism was noticed in 5 (17%) of cases. The difference between mean total keratometric power for both devices was statistically significant (0.2 D, p p = 0.007). Conclusions: For the corneal astigmatism <1.5 D, the difference between anterior and total corneal astigmatism measured with SS-OCT was clinically not significant. The mean anterior and total keratometry values obtained with Scheimpflug and SS-OCT biometers are not interchangeable

The corneo-scleral junction assessed with optical coherence tomography

Purpose To evaluate corneo-scleral junction (CSJ) using anterior segment optical coherence tomography (AS-OCT) and describe the pattern of cornea and sclera interfusion based on tissue reflectivity. Methods This prospective observational study enrolled candidates for vision correction. Eyes with previous ocular surgery or irregular corneas were excluded. Temporal and nasal CSJ width and reflectivity patterns were assessed with AS-OCT horizontal scans. Correlations between manual and automated variables and multivariate linear regression analyses with age and spherical equivalent were performed. Results 101 right eyes were analysed. Temporal CSJ was wider (median 1.62; 1.13 to 2.22 mm) compared to the nasal side (median 1.18; 0.73 to 1.80 mm) (pConclusions The temporal CSJ was wider and had regular (V or U-shaped) reflectivity patterns, while nasal CSJ was narrower and more irregular. The CSJ width was independent of age and refractive error and could not be predicted from other parameters. The HVID measurement accuracy may benefit from CSJ analysis based on AS-OCT

The corneo-scleral junction assessed with optical coherence tomography.

PurposeTo evaluate corneo-scleral junction (CSJ) using anterior segment optical coherence tomography (AS-OCT) and describe the pattern of cornea and sclera interfusion based on tissue reflectivity.MethodsThis prospective observational study enrolled candidates for vision correction. Eyes with previous ocular surgery or irregular corneas were excluded. Temporal and nasal CSJ width and reflectivity patterns were assessed with AS-OCT horizontal scans. Correlations between manual and automated variables and multivariate linear regression analyses with age and spherical equivalent were performed.Results101 right eyes were analysed. Temporal CSJ was wider (median 1.62; 1.13 to 2.22 mm) compared to the nasal side (median 1.18; 0.73 to 1.80 mm) (pConclusionsThe temporal CSJ was wider and had regular (V or U-shaped) reflectivity patterns, while nasal CSJ was narrower and more irregular. The CSJ width was independent of age and refractive error and could not be predicted from other parameters. The HVID measurement accuracy may benefit from CSJ analysis based on AS-OCT

Multivariable linear regression analysis of the relationship between age and spherical equivalent refractive error to aqueous depth, angle opening distance and trabecular space area at temporal and nasal side of horizontal AS-OCT scan.

Multivariable linear regression analysis of the relationship between age and spherical equivalent refractive error to aqueous depth, angle opening distance and trabecular space area at temporal and nasal side of horizontal AS-OCT scan.</p

The assessment of corneo-scleral junction width.

The horizontal AS-OCT scan of the right eye with callipers set to measure the corneo-scleral junction width (red lines) as a distance between last optically clear corneal section and first optically opaque scleral section. Determination of posterior limbal border was supported with the optical shadowing of iris from the scleral tissue (white arrows). Dashed lines perpendicular to the iris, with a starting point at the last visible iris pigment epithelium, point at the first fully opaque scleral section.</p

Box-plots of horizontal visible iris diameter (HVID) in eyes with different temporal corneo-scleral junction shape: V, U, Y and irregular (<i>P</i> = .021, Kruskal-Wallis test).

Box-plots of horizontal visible iris diameter (HVID) in eyes with different temporal corneo-scleral junction shape: V, U, Y and irregular (P = .021, Kruskal-Wallis test).</p

Data.

(XLSX)</p

The shape of corneo-scleral junction.

Examples of different tomographic reflectivity patterns of corneo-scleral junction at the horizontal corneal meridian: V-, U- and Y-shaped transition (temporal side); irregular transition (nasal side).</p

Descriptive statistics of analysed ocular anterior segment variables: Mean, standard deviation (SD), median, minimum (Min), maximum (Max), interquartile range (IR) and coefficient of variation (CV).

Descriptive statistics of analysed ocular anterior segment variables: Mean, standard deviation (SD), median, minimum (Min), maximum (Max), interquartile range (IR) and coefficient of variation (CV).</p