For a 5D myope wearing -5D contact lenses, what is the distal point?

For a 5D myope wearing -5D contact lenses, what is the distal point?

• A. Infinity
• B. Near point
• C. Far point
• D. Proximal point

Answer: (A)

Distal point, or far point, is the location along the optical axis where light from a very distant object would have to originate to form a sharp image on the retina. For a myopic eye, that point lies in front of the eye at a finite distance, equal to 1 divided by the myopic power in meters. Here, the eye is -5 diopters, so without correction the far point is about 0.2 meters in front of the eye. Applying a correcting lens of the same magnitude but opposite sign (a -5D contact lens) neutralizes the myopia for distant objects, making the eye effectively emmetropic for far targets. That shifts the far point to infinity, so the distal point is at infinity. Near point and proximal point describe other aspects of focusing or accommodation and do not define the distal point in this corrected scenario.

Distal point, or far point, is the location along the optical axis where light from a very distant object would have to originate to form a sharp image on the retina. For a myopic eye, that point lies in front of the eye at a finite distance, equal to 1 divided by the myopic power in meters. Here, the eye is -5 diopters, so without correction the far point is about 0.2 meters in front of the eye. Applying a correcting lens of the same magnitude but opposite sign (a -5D contact lens) neutralizes the myopia for distant objects, making the eye effectively emmetropic for far targets. That shifts the far point to infinity, so the distal point is at infinity. Near point and proximal point describe other aspects of focusing or accommodation and do not define the distal point in this corrected scenario.