Scleral Shape and Its Correlations With Corneal Astigmatism

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Optometry

Background:

• Astigmatism is a common refractive error affecting vision.
• The precise anatomical basis of astigmatism, particularly the role of the sclera, remains incompletely understood.
• Previous studies have primarily focused on corneal topography in astigmatism.

Purpose of the Study:

• To investigate the correlation between scleral shape and the presence and degree of corneal astigmatism.
• To determine if scleral topography contributes to or is influenced by astigmatism.
• To differentiate the contributions of corneal and scleral shape to astigmatism.

Main Methods:

• Acquired three-dimensional (3D) corneoscleral maps from 44 eyes of 22 participants (11 astigmatic, 11 nonastigmatic) using a corneoscleral topographer.
• Segmented 3D maps into concentric annuli to analyze radial elevation differences.
• Fitted elevation data to sinusoidal functions to extract decentration and astigmatic components for comparison between groups.

Main Results:

• A significant correlation was observed between corneal and scleral asymmetry in astigmatic eyes.
• Corneal and scleral asymmetry were found to be independent in nonastigmatic eyes.
• While the decentration term showed no significant difference between groups, the astigmatic component was statistically significant in astigmatic eyes.

Conclusions:

• Corneal and scleral shapes are interconnected in individuals with astigmatism.
• These findings indicate that astigmatism may be a characteristic of the entire ocular globe, not solely the cornea.
• This suggests a potential need to consider the sclera in future models and treatments for astigmatism.