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Characterization and diagnostic value of the vector parameters ocular residual astigmatism and topography disparity in keratoconus

Poster Details

First Author: D.Pinero SPAIN

Co Author(s):    R. Soto-Negro   A. Artola   R. Pérez-Cambrodí   P. Ruiz-Fortes     

Abstract Details



Purpose:

To characterize the distribution of the vector parameters ocular residual astigmatism (ORA) and topography disparity (TD) in a sample of keratoconus eyes as well as to evaluate the diagnostic value of these parameters to discriminate between keratoconus and healthy cornea.

Setting:

Department of Ophthalmology (Oftalmar), Medimar International Hospital, Spain

Methods:

A total of 45 eyes of 27 patients with ages ranging between 17 and 73 years (mean age: 37.8±11.9 years) and with the diagnosis of keratoconus according to different topographic, pachymetric, biomicroscopic and refractive findings were included. The ORA and TD vectors were obtained by means of the Alpins vector method and their distribution in our keratoconus sample was evaluated. Likewise, the correlation between ORA and posterior corneal astigmatism was studied. Finally, the sensitivity and specificity (ROC curve analysis) of ORA and TD for the detection of keratoconus was also analyzed by considering a sample of healthy eyes including 101 eyes of 101 patients with ages ranging between 15 and 64 years.

Results:

Mean magnitude of the ORA vector was 3.23±2.38 D, with an axis predominantly against-the-rule (ATR) (with-the-rule 8 eyes, ATR 29 eyes and oblique 8 eyes). A poor but statistically significant correlation was found between the magnitude of ORA and posterior corneal astigmatism (r=0.31, p=0.04). Linear regression analysis showed that there was a linear relationship between both variables, although the predictability was poor (R2: 0.10). Mean magnitude of TD was 9.29±8.18 D, ranging from 0.32 to 30.28 D. Differences in ORA and TD between healthy and keratoconus groups were statistically significant (p<0.01). The ROC curve analysis showed a great diagnostic ability for both vector parameters, ORA (cutoff point: 1.15 D, sensitivity 88%, specificity 81%) and TD (cutoff point: 1.62 D, sensitivity 93%, specificity 90%).

Conclusions:

The magnitude of vector parameters ORA and TD are significantly increased in keratoconus eyes and are useful for the detection of this condition. Future studies should evaluate the potential diagnostic value of these parameters for the detection of keratoconus suspects. FINANCIAL INTEREST: NONE

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