Which combination of factors is commonly considered to determine sagittal depth?

Which combination of factors is commonly considered to determine sagittal depth?

• A. Base curve, diameter, Ks, HVID
• B. Base curve and diameter only
• C. Ks and HVID only
• D. Diameter, Ks, and HVID only

Answer: (A)

Sagittal depth describes how much the back surface of a soft contact lens sits above the corneal surface from center to periphery, so predicting it relies on both lens shape and eye size. The base curve sets the lens’s central curvature, largely determining how much the lens vaults over the cornea at the center. The diameter affects how far the lens extends toward the edge, increasing or decreasing sag toward the periphery and influencing edge alignment. The Ks value shows how steep or flat the cornea is, guiding how tight or loose the central vault should be to sit properly on the eye. The horizontal visible iris diameter (HVID) reflects the overall horizontal size of the visible anterior eye, informing how much coverage the lens must provide to sit comfortably without edge lift. Taken together, these four factors give a comprehensive sense of how a lens will sit on the eye and what sagittal depth is appropriate. Failing to consider any one of them can lead to misjudging how much sag the lens will have, since each component contributes to the final fit.

Sagittal depth describes how much the back surface of a soft contact lens sits above the corneal surface from center to periphery, so predicting it relies on both lens shape and eye size. The base curve sets the lens’s central curvature, largely determining how much the lens vaults over the cornea at the center. The diameter affects how far the lens extends toward the edge, increasing or decreasing sag toward the periphery and influencing edge alignment. The Ks value shows how steep or flat the cornea is, guiding how tight or loose the central vault should be to sit properly on the eye. The horizontal visible iris diameter (HVID) reflects the overall horizontal size of the visible anterior eye, informing how much coverage the lens must provide to sit comfortably without edge lift. Taken together, these four factors give a comprehensive sense of how a lens will sit on the eye and what sagittal depth is appropriate. Failing to consider any one of them can lead to misjudging how much sag the lens will have, since each component contributes to the final fit.