Ординатура / Офтальмология / Английские материалы / Jaypee Gold Standard Mini Atlas Series CORNEALTOPOGRAPHY_Agarwal, Jacob_2009
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MINI ATLAS SERIES: CORNEAL TOPOGRAPHY
of the highest point on the anterior as |
be indicative of early keratoconus |
Infero-temporal displacement |
posterior elevation profile can |
FIGURE 4.10: |
well as the |
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CHAPTER 4: CORNEAL ECTASIA POST-LASIK: THE ORBSCAN ADVANTAGE
of > 2.0 D in the 5 |
all, but should not |
of >1.5 D in the 3 mm central zone and |
us. This sign is probably the weakest of |
FIGURE 4.11: An irregularity |
mm central zone should alert be ignored |
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MINI ATLAS SERIES: CORNEAL TOPOGRAPHY
FIGURE 4.12: Normal band scale: no pop-ups: cornea within normal band
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CHAPTER 4: CORNEAL ECTASIA POST-LASIK: THE ORBSCAN ADVANTAGE
and one |
undergo |
pachymetry map |
corneas ability to |
one in the |
about this |
FIGURE 4.13: Normal band scale with two pop-ups: |
in the posterior elevation map: there is great concern lamellar refractive surgery |
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MINI ATLAS SERIES: CORNEAL TOPOGRAPHY
FIGURE 4.14: Normal band scale with three pop-ups: definitely a no-go situation
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CHAPTER 4: CORNEAL ECTASIA POST-LASIK: THE ORBSCAN ADVANTAGE
LASIK candidates towards safe and effective outcomes. With newer technology integration using wavefront guidance (Zywave-B and L) we can detect higher order aberrations in the form of Coma and increased RMS values (Gulani A.C: Wavefront principles: Simplified and Applied. Instructional course. ESCRS, Paris, Sept 2004) aiding earlier detection of keratoconus and other potential ectatic corneal conditions. Pellucid marginal degeneration is mostly the cause of corneal topographic changes when correlated with higher levels of trefoil. Keratoconus will induce most likely higher levels of coma.
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5
ORBSCANA CORNEAL MAPPINGI ININ REFRACTIVEI
SURGERY
• Francisco Sánchez León
MINI ATLAS SERIES: CORNEAL TOPOGRAPHY
Today corneal topography plays several critical roles in different refractive surgery decisions. Conventional axial and tangential topography maps are not enough to demonstrate a healthy cornea and we cannot decide either if Lasik surgery, any type of surface laser refractive procedure or intracorneal rings for early keratoconus are suitable procedures indicated for any case based only on surface topographic evaluation.
Maw,1 mentioned that he served as consultant of six cases of postoperative Lasik ectasia ocurred in low to moderate myopia, unfortunately none of the eyes he examined had undergone a preoperative evaluation with Orbscan, so he was unable to analize the posterior elevation or the displacement of either the posterior float or corneal thinning. This is unfare for a Lasik patient, in the times when technologies are capable of such analysis.
Bausch and Lomb’s Orbscan® IIz (Fig. 5.1) is a fully integrated multidimensional diagnostic system that elevates diagnostics beyond mere topography. Unlike current topography systems which scan the surface of the eye at standard points, the Orbscan II acquires over 9000 data points in 1.5 seconds to meticulously map the entire corneal surface (11 mm), and analyze elevation and curvature measurements on both the anterior and posterior surfaces of the cornea.
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CHAPTER 5: ORBSCAN CORNEAL MAPPING IN REFRACTIVE SURGERY
FIGURE 5.1: Zyoptix dual work station. Integrates Orbscan ZII and Zywave aberrometer
The Orbscan® system (Bausch and Lomb, Rochester, NY) uses the principle of projection. Forty scanning slit beams (20 from the left and 20 from the right with up to
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