Contact Lens Fitting in a Patient with Keratoconus
A 24-year-old female with keratoconus presents for contact lens fitting. She has been diagnosed 3 years ago and has been using spectacles, but her vision is now 20/60 in the right eye and 20/40 in the left eye. She complains of glare and halos at night. Topography shows inferior steepening in both eyes, with simulated K readings of 48.00 D in the right eye and 45.00 D in the left eye. She is interested in contact lenses for better vision. She has no history of contact lens wear. She works as a graphic designer and spends long hours in front of a computer.
1. What type of contact lens would you recommend and why?
Read the worked answer
For keratoconus, rigid gas permeable (RGP) lenses are the gold standard for visual correction because they create a tear lens that neutralizes irregular astigmatism. Given her occupation with computer use, she may experience dry eye, so a high-Dk RGP lens with good wettability is preferred. Alternatively, a specialty soft lens for keratoconus (e.g., Kerasoft) could be considered, but RGPs typically provide sharper vision. The fitting should be done with topography-guided selection. The goal is to align the lens with the cone and provide a central clearance. She should be educated about adaptation, care, and the importance of regular follow-up. If she is intolerant to RGPs, a piggyback system or scleral lens could be considered. Scleral lenses are also an option, especially for comfort and for computer use, as they vault the cornea and provide a fluid reservoir. Given her long hours of computer work, a scleral lens might be more comfortable and reduce dry eye symptoms. However, scleral lenses require more expertise and cost. Therefore, recommend a trial of RGP lenses first, with the option of scleral lenses if unsuccessful. The decision should be based on her tolerance and lifestyle.
2. What are the key considerations for prescribing contact lenses for this patient, and what follow-up schedule would you recommend?
Read the worked answer
Key considerations: 1) Corneal topography to assess the cone location and curvature. 2) Lens parameters: base curve, diameter, and power based on trial fitting. 3) Evaluate lens fit with fluorescein pattern: central clearance, mid-peripheral bearing, edge lift. 4) Over-refraction to determine final power. 5) Teach proper handling and hygiene. 6) Warn about the risk of corneal abrasion, infection, and hypoxia. 7) Discuss the need for backup spectacles. Follow-up: initial check after 1 week, then 1 month, then every 6 months. At each visit, assess visual acuity, lens fit, corneal health, and compliance. She should be advised to remove lenses if she experiences pain, redness, or decreased vision. Given her computer use, recommend frequent blinking and lubricants. Also, consider the cost and her ability to afford replacements. Document all findings and provide written instructions.