Contact Lens SpectrumThe Shape Shifters

Understanding the impact of corneoscleral shape on scleral lens fitting.

The article looks into the complexities of corneoscleral shape (CSS) and its implications for scleral lens fitting. It emphasizes the importance of understanding the anatomical intricacies of the eye, including the cornea, corneoscleral junction, and sclera, to achieve a successful lens fit. Advanced imaging techniques and recent research findings are discussed to guide physicians in the lens fitting process.

Key Points:

• The cornea, bulbar conjunctiva, and sclera are the primary anatomical structures influencing the surface shape of the eye.
• Advanced imaging techniques like AS-OCT have revolutionized the ability to measure and assess the cornea.
• The corneoscleral junction (CSJ) is tangential, not curved, affecting scleral lens design.
• Scleral shape varies significantly, with the temporal scleral surface being steeper than nasally.
• A classification system by the Scleral Shape Study Group categorizes scleral shapes into four groups, aiding in lens design.

Additional Points:

• Corneal diameter and toricity are crucial considerations for scleral lens fitting.
• Scleral toricity averages 100 to 200 microns at a 15mm chord and increases with increasing chord values.
• The bulbar conjunctiva acts as a cushion for the scleral lens landing zone.
• Scleral shape can change after treatments like corneal crosslinking.

Conclusion:

• Understanding the nuances of corneoscleral topography is crucial for optimal scleral lens fitting. Advanced imaging techniques and a classification system for scleral shapes offer valuable tools for physicians. Customized lens designs, considering both corneal and scleral toricity, are often necessary for successful outcomes.

“Scleral toricity can be predicted for eyes with astigmatism that have limbal-to-limbal toricity, as toricity in these cases extends beyond the cornea to the scleral surface. Keratoconic eyes can have predicted scleral steepness in the same semi-meridian in the case of peripheral ectasia, and consequently will be best fit with a quadrant-specific or free-form lens design.”
– Gregory W. Denaeyer, OD

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