Which factor has the greatest impact on sagittal depth?

Which factor has the greatest impact on sagittal depth?

• A. HVID
• B. Base curve
• C. Diameter
• D. Ks

Answer: (A)

Sagittal depth is essentially how tall the lens sits above the ocular surface when it’s on the eye. The biggest influence on that height is how wide the lens must be, because a larger lens covers more of the sclera and creates a taller arc across the eye. That width is driven by the eye’s size, which we estimate with HVID (horizontal visible iris diameter). So, a larger HVID pushes you toward a larger lens diameter, which in turn raises the sagittal depth more than any other adjustment. The back-curvature of the lens (base curve) mainly changes how closely the lens hugs the cornea and how the edge lifts, but those effects are smaller compared with changing the lens diameter. Similarly, the corneal curvature (Ks) influences the fit but doesn’t alter sagittal depth as dramatically as the diameter-driven change does. In short, since HVID determines the necessary lens diameter—and diameter largely governs sagittal height—HVID has the greatest impact on sagittal depth.

Sagittal depth is essentially how tall the lens sits above the ocular surface when it’s on the eye. The biggest influence on that height is how wide the lens must be, because a larger lens covers more of the sclera and creates a taller arc across the eye. That width is driven by the eye’s size, which we estimate with HVID (horizontal visible iris diameter). So, a larger HVID pushes you toward a larger lens diameter, which in turn raises the sagittal depth more than any other adjustment.

The back-curvature of the lens (base curve) mainly changes how closely the lens hugs the cornea and how the edge lifts, but those effects are smaller compared with changing the lens diameter. Similarly, the corneal curvature (Ks) influences the fit but doesn’t alter sagittal depth as dramatically as the diameter-driven change does. In short, since HVID determines the necessary lens diameter—and diameter largely governs sagittal height—HVID has the greatest impact on sagittal depth.