Which factor has the greatest impact on sagittal depth?

Which factor has the greatest impact on sagittal depth?

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

Answer: (A)

Sagittal depth is the vertical clearance the lens must maintain above the cornea, essentially how high the posterior lens surface sits over the eye. The biggest driver of that height is how large the eye is, because a larger eye means a larger corneal diameter and more arc length for the lens to accommodate. The horizontal visible iris diameter provides a practical proxy for corneal diameter; a bigger HVID indicates a larger eye and thus a greater sagittal depth is needed to vault the cornea and create the proper tear reservoir. Keratometry (Ks) tells you how steep or flat the cornea is and will influence the required central curvature, but it doesn’t change the overall sagittal height as much as the eye’s size does. The base curve governs the lens’s central curvature and can adjust sag to some degree, but again, the eye’s size has the more substantial impact on sagittal depth. So, the factor most strongly shaping sagittal depth is the eye size measurement reflected by HVID.

Sagittal depth is the vertical clearance the lens must maintain above the cornea, essentially how high the posterior lens surface sits over the eye. The biggest driver of that height is how large the eye is, because a larger eye means a larger corneal diameter and more arc length for the lens to accommodate. The horizontal visible iris diameter provides a practical proxy for corneal diameter; a bigger HVID indicates a larger eye and thus a greater sagittal depth is needed to vault the cornea and create the proper tear reservoir.

Keratometry (Ks) tells you how steep or flat the cornea is and will influence the required central curvature, but it doesn’t change the overall sagittal height as much as the eye’s size does. The base curve governs the lens’s central curvature and can adjust sag to some degree, but again, the eye’s size has the more substantial impact on sagittal depth. So, the factor most strongly shaping sagittal depth is the eye size measurement reflected by HVID.