Dataset Information

A new, pachymetry-based approach for diagnostic cutoffs for normal, suspect and keratoconic cornea.

ABSTRACT:

Purpose

To analyze whether an association exists between keratometric and pachymetric changes in the cornea, and whether it can be used to create pachymetric cutoff criteria secondary to keratometric criteria.

Methods

In this cross-sectional study, 1000 candidates presenting to the refractive surgery services of a tertiary care hospital underwent bilateral Orbscan IIz (Bausch and Lomb) assessment along with other ophthalmic evaluation.

Results

Stepwise regression analysis-based models showed that simulated keratometry (simK) astigmatism was significantly predicted by the minimum corneal thickness (MCT) and difference between central and MCT (?CT), mean SimK by the MCT and ?CT, and maximum keratometry in the central 10-mm zone by the MCT and ?CT (P<0.001). The mean MCT values were 542.5 ± 39.6, 539.9 ± 39.2, 524.2 ± 49.5, and 449.3 ± 73.7 ?m for flatter normal (<44 D), steeper normal (? 44 D), keratoconus suspect and keratoconic eyes, respectively (P<0.001). The mean differences between central corneal thickness and MCT (?CT) were 12.2 ± 7.1 ?m, 12.4 ± 7.4 ?m, 14.4 ± 8.9 ?m and 23.2 ± 10.1 ?m for the flatter normal, steeper normal, keratoconus suspect, and keratoconic eyes, respectively (P<0.001). Mean and 2SD cutoff were used to suggest that a cornea having MCT< 461 ?m or ?CT>27 ?m has only a 2.5% chance of being normal and not a keratoconus suspect or worse.

Conclusion

Pachymetric diagnostic cutoffs can be used as adjuncts to the existing topographic criteria to screen keratoconus suspect and keratoconic eyes.

SUBMITTER: Prakash G

PROVIDER: S-EPMC3351046 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Publications

A new, pachymetry-based approach for diagnostic cutoffs for normal, suspect and keratoconic cornea.

Prakash G G Agarwal A A Mazhari A I AI Kumar G G Desai P P Kumar D A DA Jacob S S Agarwal A A

Eye (London, England) 20120127 5

<h4>Purpose</h4>To analyze whether an association exists between keratometric and pachymetric changes in the cornea, and whether it can be used to create pachymetric cutoff criteria secondary to keratometric criteria.<h4>Methods</h4>In this cross-sectional study, 1000 candidates presenting to the refractive surgery services of a tertiary care hospital underwent bilateral Orbscan IIz (Bausch and Lomb) assessment along with other ophthalmic evaluation.<h4>Results</h4>Stepwise regression analysis-b ...[more]

PMID: 22281864

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Project description:BACKGROUND:Presently, for patients presenting with suspected Normal Pressure Hydrocephalus (NPH) who undergo temporary drainage of cerebrospinal fluid (CSF) there is no defined model to differentiate chance improvement form clinical significance change at the individual patient level. To address this lack of information we computed standard regression based clinical change models for the 10 Meter Walk Test, Timed Up & Go, Dual Timed Up & Go, 6-Minute Walk Test, Mini-Balance Evaluation Systems Test, Montreal Cognitive Assessment, and Symbol Digit Modalities using data from patients with suspected NPH that underwent temporary drainage of CSF. These clinically significant change modes can classify clinically significant improvement following temporary drainage of CSF at the individual patient level. This allows for physicians to differentiate a clinically significant improvement in symptoms from chance improvement. METHODS:Data was collected from 323 patients, over the age of 60, with suspected NPH that underwent temporary drainage of CSF with corresponding gait and cognitive testing. McSweeney Standardized Regression Based Clinical Change Models were computed for standard gait and cognitive measures: Timed Up & Go, Dual Timed Up & Go, 10 Meter Walk Test, MiniBESTest, 6-Minute Walk Test, Montreal Cognitive Assessment, and Symbol Digit Modalities Test. To assess the discriminate validity of the measures we used correlations, Chi2, and regression analyses. RESULTS:The clinical change models explained 69-91.8% of the variability in post-drain performance (p?<? 0.001). As patient scores became more impaired, the percent change required for improvement to be clinically significant increased for all measures. We found that the measures were not discriminate, the Timed Up & Go was highly related to the 10 Meter Walk Test (r?=?0.85, R2?=?0.769-0.738, p?<? 0.001), MiniBESTest (r?=?-?0.67, R2?=?0.589-0.734, p?<? 0.001), and 6?Minute Walk Test (r?=?-?0.77, R2?=?0.71-0.734, p?<? 0.001). CONCLUSION:Standardized Regression Based Clinically Significant Change Models allow for physicians to use an evidence-based approach to differentiate clinically significant change from chance improvement at the individual patient level. The Timed Up & Go was shown to be predictive of detailed measures of gait velocity, balance, and endurance.

Project description:ObjectiveTo map the corneal epithelial thickness with Fourier-domain optical coherence tomography (OCT) and to develop epithelial thickness-based variables for keratoconus detection.DesignCross-sectional observational study.ParticipantsOne hundred forty-five eyes from 76 normal subjects and 35 keratoconic eyes from 22 patients.MethodsA 26,000-Hz Fourier-domain OCT system with 5-μm axial resolution was used. The cornea was imaged with a Pachymetry + Cpwr scan pattern (6-mm scan diameter, 8 radials, 1024 axial-scans each, repeated 5 times) centered on the pupil. Three scans were obtained at a single visit in a prospective study. A computer algorithm was developed to map the corneal epithelial thickness automatically. Zonal epithelial thicknesses and 5 diagnostic variables, including minimum, superior-inferior (S-I), minimum-maximum (MIN-MAX), map standard deviation (MSD), and pattern standard deviation (PSD), were calculated. Repeatability of the measurements was assessed by the pooled standard deviation. The area under the receiver operating characteristic curve (AUC) was used to evaluate diagnostic accuracy.Main outcome measuresDescriptive statistics, repeatability, and AUC of the zonal epithelial thickness and diagnostic variables.ResultsThe central, superior, and inferior epithelial thickness averages were 52.3 ± 3.6 μm, 49.6 ± 3.5 μm, and 51.2 ± 3.4 μm in normal eyes and 51.9 ± 5.3 μm, 51.2 ± 4.2 μm, and 49.1 ± 4.3 μm in keratoconic eyes. Compared with normal eyes, keratoconic eyes had significantly lower inferior (P = 0.03) and minimum (P<0.0001) corneal epithelial thickness, greater S-I (P = 0.013), more negative MIN-MAX (P<0.0001), greater MSD (P<0.0001), and larger PSD (P<0.0001). The repeatability of the zonal average, minimum, S-I, and MIN-MAX epithelial thickness variables were between 0.7 and 1.9 μm. The repeatability of MSD was better than 0.4 μm. The repeatability of PSD was 0.02 or better. Among all epithelial thickness-based variables investigated, PSD provided the best diagnostic power (AUC = 1.00). Using an PSD cutoff value of 0.057 alone gave 100% specificity and 100% sensitivity.ConclusionsHigh-resolution Fourier-domain OCT mapped corneal epithelial thickness with good repeatability in both normal and keratoconic eyes. Keratoconus was characterized by apical epithelial thinning. The resulting deviation from the normal epithelial pattern could be detected with very high accuracy using the PSD variable.Financial disclosure(s)Proprietary or commercial disclosure may be found after the references.

Dataset Information

A new, pachymetry-based approach for diagnostic cutoffs for normal, suspect and keratoconic cornea.

Purpose

Methods

Results

Conclusion

Publications

A new, pachymetry-based approach for diagnostic cutoffs for normal, suspect and keratoconic cornea.

Similar Datasets

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