June 2020
Volume 61, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2020
To compare the refractive outcomes after cataract surgery using conventional keratometry (K) with Barrett Universal II formula and total keratometry (TK) with Barrett TK Universal II formula for intraocular lens power calculation
Author Affiliations & Notes
  • Pragya Saini
    ICARE Postgraduate Institute of Ophthalmology, Noida, India
  • Saurabh Choudhry
    ICARE Postgraduate Institute of Ophthalmology, Noida, India
  • Meetu Rajput
    ICARE Postgraduate Institute of Ophthalmology, Noida, India
  • Sagnik Sen
    Vitreo-retina, Aravind Eye Hospital, India
  • Footnotes
    Commercial Relationships   Pragya Saini, None; Saurabh Choudhry, None; Meetu Rajput, None; Sagnik Sen, None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 609. doi:
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      Pragya Saini, Saurabh Choudhry, Meetu Rajput, Sagnik Sen; To compare the refractive outcomes after cataract surgery using conventional keratometry (K) with Barrett Universal II formula and total keratometry (TK) with Barrett TK Universal II formula for intraocular lens power calculation. Invest. Ophthalmol. Vis. Sci. 2020;61(7):609.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : TK is calculated using values of anterior and posterior corneal curvature, corneal thickness and thick lens formula. The application of TK for regular use in intraocular lens (IOL) power calculation needs exploration and validation.

Methods : 155 eyes of 126 patients undergoing uneventful cataract surgery were prospectively evaluated in this study using swept-source biometry (IOLMaster 700). Data recorded were K, TK, anterior chamber depth, white-to-white, lens thickness and axial length. Emmetropic IOL powers were calculated using K and TK in Barrett Universal II and TK Universal II formulas respectively and IOL selected by surgeon's preference. Absolute prediction error (APE) of spherical equivalent (SE), defined as difference between postoperative refractive error and the target refraction predicted by the two Barrett formulas, was calculated based on TK and K at 1-month follow-up. Percentage of eyes within +- 0.25, +- 0.50 and +- 1.00 D of target refraction were calculated.

Results : Mean difference between K (40.74 +- 11.4 D) and TK (40.78 +- 11.51 D) was 0.04D, and both formulas showed significant correlation (r = 0.992). APE measured by both formulas showed signfiicant correlation (r = 0.846) (Fig 1A). Mean APE in SE was higher for Barrett TK compared to K, with a mean APE difference (TK-K) of 0.09 +- 0.21 D (95% CI: -0.42 – 1.1 D). Proportion of eyes within +- 0.25D of target refraction was higher in Barrett K group (47.7%), while that within +- 0.50 and +- 1.00 D was higher in Barrett TK group (38.7% and 23.2% respectively) (Fig 2A). Bland-Altman plot analysis and box-plot of differences showed that APE values were higher for Barrett TK in mid-range of corresponding Barrett K APE values (Fig 1B, 2B). Fig 1C shows trend towards higher keratometry values with Barrett TK and Fig 1D shows higher APE in SE in mid-range of keratometry with Barrett TK. Cylinder values measured by both Barrett TK and K showed good agreement.

Conclusions : Both conventional K and TK may be equally good for IOL power calculation, however TK may give rise to slightly higher keratometry values resulting in higher absolute prediction errors in spherical equivalent postoperatively. It does not seem prudent to immediately shift completely to TK from using conventional K.

This is a 2020 ARVO Annual Meeting abstract.

 

 

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