In extreme contact lens fitting, which combination is typically preferred?

In extreme contact lens fitting, which combination is typically preferred?

• A. Large HVID and Steep Ks
• B. Large HVID and Flat Ks
• C. Large HVID and Small Ks
• D. Small HVID and Flat Ks

Answer: (C)

The main idea is that extreme lens fits are controlled by two practical factors: how wide the lens needs to span the eye and how steep or flat the corneal curvature is to match with a stable, centered vault. A large horizontal visible iris diameter means the eye is wide, so you typically need a larger-diameter lens to cover the iris properly and sit on the sclera without edge lift or decentration. At the same time, a small Ks indicates a flatter cornea, which is easier to pair with a flatter lens surface. Using a flatter corneal curvature helps the lens achieve comfortable, stable alignment when you opt for a large diameter, because the peripheral shape can sit more evenly on the scleral surface and maintain a consistent tear reservoir. Put together, a large-diameter lens on a flatter cornea tends to fit well in extreme cases, offering reliable centration, vault, and comfort.

The main idea is that extreme lens fits are controlled by two practical factors: how wide the lens needs to span the eye and how steep or flat the corneal curvature is to match with a stable, centered vault. A large horizontal visible iris diameter means the eye is wide, so you typically need a larger-diameter lens to cover the iris properly and sit on the sclera without edge lift or decentration. At the same time, a small Ks indicates a flatter cornea, which is easier to pair with a flatter lens surface. Using a flatter corneal curvature helps the lens achieve comfortable, stable alignment when you opt for a large diameter, because the peripheral shape can sit more evenly on the scleral surface and maintain a consistent tear reservoir. Put together, a large-diameter lens on a flatter cornea tends to fit well in extreme cases, offering reliable centration, vault, and comfort.