If a GP lens is fitted steeper than the K, what tear layer sign is formed?

• A. Plus tear layer
• B. Minus tear layer
• C. Zero tear layer
• D. Uncertain tear layer

Answer: (A)

The tear layer sign reflects the optical effect of the tear film between the GP lens and the cornea, which depends on how the lens curvature compares to the corneal curvature. When the GP lens is steeper than the cornea, the tear film must bulge more to fill the gap, creating a tear layer with positive optical power. That means the tear layer is a plus tear layer, indicating a positive dioptric contribution from the tear film. If the lens were flatter than the cornea, you’d get a minus tear layer, and if the curvatures matched, the tear layer would be essentially zero. So, the tear layer sign formed in this situation is a plus tear layer.