For a patient with Refraction: -2.00 -1.00 x 180, Ks: 43.50/44.50 @090, BCR: 43.50, what is the expected tear layer?

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Multiple Choice

For a patient with Refraction: -2.00 -1.00 x 180, Ks: 43.50/44.50 @090, BCR: 43.50, what is the expected tear layer?

Explanation:
Tear layer power under a gas-permeable lens comes from the difference between the corneal curvature (Ks) and the lens’s back central radius (BCR). If the back curve matches the cornea in a given meridian, the tear lens in that meridian has zero power (Plano). In this case, the flat meridian of the cornea is 43.50 D, and the lens back curve is also 43.50 D. That means the tear layer has 0 D of refractive power in that meridian, i.e., Plano. The other choices imply a nonzero tear power or no tear film, which isn’t indicated by the given Ks and BCR data.

Tear layer power under a gas-permeable lens comes from the difference between the corneal curvature (Ks) and the lens’s back central radius (BCR). If the back curve matches the cornea in a given meridian, the tear lens in that meridian has zero power (Plano).

In this case, the flat meridian of the cornea is 43.50 D, and the lens back curve is also 43.50 D. That means the tear layer has 0 D of refractive power in that meridian, i.e., Plano. The other choices imply a nonzero tear power or no tear film, which isn’t indicated by the given Ks and BCR data.

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