What is the main disadvantage associated with aspheric GP lenses?

What is the main disadvantage associated with aspheric GP lenses?

• A. Decreased comfort
• B. Increased spherical aberrations
• C. Decreased tear exchange
• D. Decreased centration

Answer: (C)

Aspheric GP lenses are designed to reduce spherical aberration by gradually changing curvature from center to edge, which improves optical quality and helps the lens sit more stably on the cornea. That stability often means less movement and less tear flow under the lens, leading to a relatively stagnant under-lens tear film. Reduced tear exchange can limit the renewal of the tear film and clearance of debris under the lens, even though the lens material itself is highly oxygen permeable. So, the main drawback tied to this design is decreased tear exchange. Comfort is not necessarily diminished (and can be improved with a smoother edge), spherical aberrations are reduced (not increased), and centration is generally good with a proper fit.

Aspheric GP lenses are designed to reduce spherical aberration by gradually changing curvature from center to edge, which improves optical quality and helps the lens sit more stably on the cornea. That stability often means less movement and less tear flow under the lens, leading to a relatively stagnant under-lens tear film. Reduced tear exchange can limit the renewal of the tear film and clearance of debris under the lens, even though the lens material itself is highly oxygen permeable. So, the main drawback tied to this design is decreased tear exchange. Comfort is not necessarily diminished (and can be improved with a smoother edge), spherical aberrations are reduced (not increased), and centration is generally good with a proper fit.