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Contact Lens – Topography Exam Review 2024/2025
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Contact Lens – Topography Exam Review 2024/2025 1 / 21 Zones of the Cornea for Topography: Names, Location...
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Contact Lens – Topography Exam Review 2024/2025 Zones of the Cornea for Topography: Names, Loca - tion Corneal Cap: Where is it located? What is the as - sumed shape and why? What is the average curva - ture? 1. Corneal Cap - Central 4mm diameter 2. Paracentral Zone - 4-8mm zone 3. Peripheral Zone - 8-11mm zone 4. Limbal Zone - 0.55mm wide Central 4mm diameter Assumed to be spherical for clinical purposes be - cause the power does not decrease more than 1D (Flattens <1D) Average Curvature - 7.9mm = 42.75D Spherically Increased in gradual flat- Corneal Eccentricity: How is the cornea shaped cen- trally? What is the trend of its shape as it moves to - ward the periphery? What types of corneal eccentric - ity exist? tening toward the periph - ery Types 1. Prolate = 0 to 1 2. Oblate = Less than 0 What is the average corneal eccentricity? Topography: What is it? Corneal Topography: What does it measure? What does it describe? 0.55 - Prolate Distribution of parts or fea- tures on the surface of an organ Distribution of tissue across the cornea Describes: - High points - Low points - Rate of change of curva - ture - Optical Regularity vs Ir - regularity Topography: What was the first development of this? How did it work? Hand Held Keratoscope: How was it used? Placido Disc Images: Nor- mal, Astigmatism, Kerato - conus In corneal topography, the closer the rings are to - gether (space between the rings smaller), the . Corneal Topography Im- ages: Normal vs Irregular vs Highly Irregular Placido disc Image from disc reflected off the tear film - air inter - fere - Cornea worked like a mir- ror Similar to Placido disc but used with the slit lamp Greater the rate of change in curvature Normal = Left Irregular = Right Highly Irregular = BottomThe benefits of buying summaries with Stuvia:
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