Determining appropriate cylinder correction with soft toric lenses

Area of Science:

• Ophthalmology
• Optometry
• Contact Lens Technology

Background:

• Current practice for fitting soft toric contact lenses often involves reducing the prescribed cylinder power.
• This reduction is frequently based on the hypothesis that a tear lens forms, compensating for the reduced power.

Purpose of the Study:

• To investigate the existence of a tear lens under soft toric lenses of varying thicknesses.
• To determine if cylinder power reduction is necessary when fitting soft toric lenses.

Main Methods:

• Soft toric lenses with thicknesses ranging from 0.06 mm to 0.14 mm were utilized.
• The presence or absence of a tear lens beneath these lenses was assessed.

Main Results:

• A tear lens could not be demonstrated under thin or standard thickness Hydron soft toric lenses.
• The study failed to provide evidence supporting the tear lens hypothesis in this context.

Conclusions:

• The absence of a tear lens suggests that reducing cylinder power may not be necessary for soft toric lens fitting.
• It may be appropriate to prescribe the same cylinder power for soft toric lenses as used in spectacle correction.