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Reverse-geometry gas-permeable lens design for pellucid marginal degeneration
Jill Liu1, Norman E Leach, Jan P G Bergmanson
1Texas Eye Research and Technology Center, College of Optometry, University of Houston, Houston, TX 77204-2020, USA. jliu@optometry.uh.edu
Eye & Contact Lens
|May 17, 2005
Summary
A reverse-geometry gas-permeable lens successfully treated pellucid marginal degeneration (PMD), improving vision and fit. This specialized lens design offers an effective solution for PMD patients.
Area of Science:
- Ophthalmology
- Corneal disease
- Optometry
Background:
- Pellucid marginal degeneration (PMD) is a rare, progressive corneal ectasia.
- It causes inferior peripheral corneal thinning and irregular astigmatism, leading to visual distortion.
- Early diagnosis and effective management are crucial for preserving visual function.
Observation:
- A 38-year-old male patient presented with reduced visual acuity due to corneal distortion.
- Slitlamp examination revealed inferior peripheral corneal thinning, consistent with PMD.
- Corneal topography using Orbscan II confirmed the diagnosis by showing peripheral steepening and thinning.
Findings:
- The patient was fitted with a Reverse Aspheric Ortho Focus (RAOF) gas-permeable lens.
- Orbscan II topography revealed significant peripheral steepening and astigmatism.
- The RAOF lens provided excellent centration, fit, and comfort, achieving 20/20 visual acuity.
Implications:
- Orbscan II is vital for diagnosing early PMD, especially when clinical signs are subtle.
- Corneal thickness and posterior float measurements from Orbscan II aid differential diagnosis.
- Reverse-geometry gas-permeable lenses offer superior fit and visual outcomes for PMD patients compared to conventional designs.