Posters

Interchangeability of swept source anterior segment optical coherence tomography (SS-AS-OCT) corneal astigmatism values

Poster Details

First Author: V.Liarakos GREECE

Co Author(s):    C. Mitrou   M. Arvanitis   M. Douvali   C. Chronopoulou   A. Maniateas  

Abstract Details

Purpose:

To evaluate corneal astigmatism measurements using swept-source anterior segment optical coherence tomography (SS-AS-OCT) and compare them with Placido topography, Scheimpflug imaging and automated keratometry.

Setting:

Eye Day Clinic, private clinic, Athens, Greece.

Methods:

In this prospective cross-sectional study, corneal topography measurements were performed using SS-AS-OCT (Casia SS-1000, Tomey), Placido topography (Wavelight – Allegro Topolyzer Vario, Alcon), Scheimpflug imaging (Wavelight Oculyzer II, Alcon) and automated keratometry (KR-8900, Topcon). All measurements were performed successively, on the same day, by the same experienced technician. Fifty-six healthy normal corneas, without prior ocular surgery or ocular comorbidities, were evaluated. Absolute values of corneal astigmatism/cylinder, described as the difference between the flattest and steepest meridians regardless of the axis, were recorded. Paired t-test, regression analysis and Bland-Altman plots were used to evaluate agreement between different devices.

Results:

Average cylinder measurements with the SS-AS-OCT were 0.92±0.55D (“real” cylinder), 1.00±0.59D (“keratometric” cylinder) and 1.11±0.66D (“anterior” cylinder). Average astigmatism measurements were 0.95±0.56D (Placido topography), 0.98±0.56D (Scheimpflug topography) and 0.86±0.53D (automated topography). Very strong correlation was observed between all devices (p<0.001; Pearson’s correlation). “Real” cylinder was almost identical with Placido astigmatism measurements (p=0.243) and “Keratometric” cylinder was almost identical with Scheimpflug astigmatism measurements (p=0.285) and similar to Placido (p=0.051). Placido and Scheimpflug astigmatism measurements were also similar (p=0.156). Bland-Altman plots showed good agreement. The rest of the measurements differed significantly from each other (p>0.05).

Conclusions:

“Keratometric” astigmatism values provided by the SS-AS-OCT may be considered interchangeable with Scheimpflug astigmatism measurements and “Real” astigmatism values provided by the SS-AS-OCT may be considered interchangeable with Placido astigmatism measurements. The rest of the measurements, although strongly correlated, cannot be considered interchangeable. FINANCIAL DISCLOUSRE: NONE