Scheimpflug imaging can obtain anterior scleral measurements that are both repeatable and reproducible in eyes with keratoconus, using a commercially-available module to assess the corneoscleral map, according to research published in Eye & Contact Lens. These measurements may have implications for specialty contact lens fitting, the report suggests.
Researchers enrolled 54 participants, including individuals with keratoconus (n=30; median age, 24 years) and control group participants (n=24; median age, 26 years), in a prospective, observational study. The team measured mean sagittal height, sagittal height astigmatism, and mean bulbar slope in 12 and 16 mm chord lengths for each study participant using the corneoscleral mapping module of the Scheimpflug imaging system.
The investigators assessed reproducibility using coefficients of variation (CoV), intraclass correlation coefficient (ICC), coefficient of repeatability (CoR1), and coefficient of reproducibility (CoR2).
Overall, mean sagittal height measurements demonstrated high repeatability and reproducibility in eyes both with and without keratoconus (CoV, ≤0.96%; ICC ≥0.97 for both). The 12 mm chord length demonstrated better repeatability and reproducibility precision compared with the 16 mm chord (CoRs, ≤43.52 vs ≥48.25 mm). Eyes with keratoconus showed poorer repeatability and reproducibility at both chord lengths compared with eyes in the control group.
The mean bulbar slope measurement also showed high repeatability and reproducibility among both cohorts (CoVs ≤3.65%; CoRs ≤2.64 for both). The sagittal height astigmatism measurement for eyes in the control group showed higher repeatability and reproducibility compared with eyes with keratoconus (CoVs, ≤29.95% vs ≥32.67%).
“The [mean bulbar slope] of chord lengths from 12 mm to 16 mm, including peripheral corneal, limbal, and anterior scleral angles, has been shown to affect scleral contact lenses and soft contact lenses fitting and design,” according to the researchers.
Study limitations include the exclusion of participants with small palpebral fissures, a single center design, and a relatively small sample size.
Yang Z, Wang M, Li Z, et al. Repeatability and reproducibility of corneoscleral topography measured with Scheimpflug imaging in keratoconus and control eyes. Eye Contact Lens. Published online March 29, 2023. doi:10.1097/ICL.0000000000000983