J Korean Ophthalmol Soc.  2010 May;51(5):651-657.

The Evaluation of Enhanced Ectasia Display Mode in Screening for Keratoconus

• Lee YJ
• Kim SW

Abstract

PURPOSE
To estimate the utility of the enhanced ectasia display mode of Pentacam in discriminating keratoconus and keratoconus suspect from normal cornea.
METHODS
Corneal topography was measured using the Pentacam in keratoconus, keratoconus suspect and a normal control group. A best-fit sphere (BFS) and an enhanced best-fit sphere (EBFS) were used as reference surfaces for corneal elevation measurements, and measured values from both the anterior and posterior surfaces were compared among the three groups. Receiver operating characteristic (ROC) curves were used to identify the optimal posterior corneal elevation cutoff points for maximal sensitivity and specificity in discriminating keratoconus and keratoconus suspect from the normal control group.
RESULTS
Mean anterior and posterior corneal elevation were statistically higher in keratoconus than in keratoconus suspect and normal corneas. The optimal cutoff point of posterior elevation was 23 micrometer for the keratoconus group, and this value was associated with a sensitivity and a specificity of 96.7% and 98.6%, respectively for keratoconus. The optimal cutoff point of enhanced posterior elevation was 43 micrometer for the keratoconus group, and this value was associated with a sensitivity and a specificity of 96.7% and 95.5%, respectively.
CONCLUSIONS
The enhanced ectasia display mode showed similar diagnostic power to that of the conventional elevation map, and the former could be more useful in a clinical setting due to the pronounced visualization of corneal elevation.

Keyword

Enhanced ectasia display; Keratoconus; Pentacam

MeSH Terms

Cornea
Corneal Topography
Dilatation, Pathologic
Keratoconus
Mass Screening
ROC Curve
Sensitivity and Specificity

Figure

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  Figure 1. Schematic comparing how removal of the exclusion zone will affect the Best-fit sphere. The elevation difference between using a standard best-fit sphere and the enhanced best-fit sphere will be significant for a conical cornea, while the difference is minimal in a normal cornea.

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  Figure 2. Receiver operator characteristic (ROC) curves for keratoconus versus keratoconus suspect or normal corneas (Left). ROC curves for keratoconus suspect versus normal corneas (Right). MPE=maximal posterior elevation on the thinnest point.

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  Figure 3. Enhanced ectasia display with elevation data presented in normal group. There is little change in relative elevation, or the appearance of the elevation map when comparing the best-fit sphere to the enhanced best-fit sphere. Corneal surface dose not show much change from the baseline to the exclusion elevation map (the map is all green).

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  Figure 4. Enhanced ectasia display with elevation data presented in keratoconus group. There is significant change in relative elevation, and the appearance of the elevation map when comparing the best-fit sphere to the enhanced best-fit sphere. Corneal posterior surface show much change from the baseline to the exclusion elevation map (central area of red).

Reference

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