Screening subclinical keratoconus with Placido-based corneal indices
Purpose: To assess in a sample of normal, keratoconic and keratoconus suspect eyes the performance of a set of new topographic indices computed directly from the digitized images of the Placido rings. Methods: This comparative study comprised a total of 124 eyes of 106 patients from the opht...
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| Format: | info:eu-repo/semantics/article |
| Language: | English |
| Published: |
2018
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| Online Access: | http://hdl.handle.net/10835/5671 http://dx.doi.org/10.1097/OPX.0b013e3182843f2a |
| Summary: | Purpose:
To assess in a sample of normal, keratoconic and keratoconus suspect eyes the
performance of a set of new topographic indices computed directly from the digitized
images of the Placido rings.
Methods:
This comparative study comprised a total of 124 eyes of 106 patients from the
ophthalmic clinics Vissum Alicante and Vissum Almería (Spain), in three groups:
control group (50 eyes), keratoconus group (50 eyes) and keratoconus suspect group (24
eyes). In all cases, a comprehensive examination was performed including the corneal
topography with a Placido-based CSO topography system. Clinical outcomes were
compared among groups, along with the discriminating performance of the proposed
irregularity indices.
Results:
Significant differences at level 0.05 were found on the values of the indices among
groups by means of Mann-Witney-Wilcoxon non-parametric test and Fisher’s exact test.
Additional statistical methods, such as receiver operating characteristic analysis and K-
fold cross-validation, confirmed the capability of the indices to discriminate between the
three groups.
Conclusions:
Direct analysis of the digitized images of the Placido mires projected on the cornea is a
valid and effective tool for detection of corneal irregularities. Although based only on
the data from the anterior surface of the cornea, the new indices performed well even
when applied to the keratoconus suspect eyes. They have the advantage of simplicity of
calculation combined with high sensitivity in corneal irregularity detection, and thus can
be used as supplementary criteria for diagnosing and grading keratoconus that can be
added to the current keratometric classifications.
Keywords: Corneal irregularities; subclinical keratoconus; irregularity index;
diagnosis; corneal topography; Placido disks |
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