In Vivo Intraocular Lens Thickness Measurement and Power Estimation Using Optical Coherence Tomography
Purpose: To estimate the power of an implanted intraocular lens (IOL) by measuring IOL thickness using anterior segment optical coherence tomography (AS-OCT) and to assess the repeatability of measurements.
Methods: Ninety-seven eyes were studied one month after uneventful phacoemulsification within the bag Acrysof SA60AT IOL implantation (range +11 to +35). All eyes had postoperative refraction of ±0.5 D of target refraction. AS-OCT was used to measure the central thickness of the IOL. Correlation between labelled IOL power and central IOL thickness as well as the measure of repeatability, for example, intraclass correlation coefficient (ICC), were evaluated. IOL thicknesses were also calculated using a formula and compared with AS-OCT-derived measurements.
Results: IOL thickness correlated significantly with labelled IOL power (R2 = 0.985, P < 0.001). The regression equation (IOL Power = [0.04 × IOL thickness in micron] – 7.56) indicates 25 microns of central IOL thickness change per 1D power change. Over the studied range, IOL power could be estimated with a precision of 0.85 ± 0.02 D (95% confidence interval: 0.83–0.94D). ICC for repeated measurements was 0.999. There was a significant correlation between calculated and measured (AS-OCT) IOL thickness (R2 = 0.984, P < 0.001).
Conclusion: Central IOL thickness measurements with the AS-OCT are highly repeatable and closely correlated with the labelled IOL power, which can predict the IOL power with ±0.85 D from the actual power. This method can be helpful in cases of postoperative IOL surprise.
Anterior Segment Optical Coherence Tomography, AS-OCT, Intraocular Lens, IOL, IOL Thickness
1. Olsen T. Calculation of intraocular lens power: A review. Acta Ophthalmol Scand 2007;85:472–485.
2. Steeples LR, Hingorani M, Flanagan D, Kelly SP. Wrong intraocular lens events-what lessons have we learned? A review of incidents reported to the National Reporting and Learning System: 2010–2014 versus 2003–2010. Eye 2016;30:1049–1055.
3. Kohnen S. Postoperative refractive error resulting from incorrectly labeled intraocular lens power. J Cataract Refract Surg 2000;26:777–778.
4. Antičić M, Ardjomand N, Sarny S, Schweighofer J, El- Shabrawi Y. Numbers sometimes lie- Refractive surprise following IOL mislabeling by the manufacturer. Eye 2019;33:868–870.
5. Ravi K, Senthil S, Pesala V. Refractive surprise following implantation of correct powered intraocular lens—A real surprise! Int Ophthalmol 2012;32:603–605.
6. Ang M, Baskaran M, Werkmeister RM, Chua J, Schmidl D, Aranha Dos Santos V, et al. Anterior segment optical coherence tomography. Prog Retin Eye Res 2018;66:132– 156.
7. Tan GS, He M, Zhao W, Sakata LM, Li J, Nongpiur ME, et al. Determinants of lens vault and association with narrow angles in patients from Singapore. Am J Ophthalmol 2012;154:39–46.
8. Turner SJ, Lee EJ, Hu V, Hollick EJ. Scheimpflug imaging to determine intraocular lens power in vivo. J Cataract Refract Surg 2007;33:1041–1044.
9. Naeser K, Naeser EV. Calculation of the thickness of an intraocular lens. J Cataract Refract Surg 1993;19:40–42.
10. McReynolds WU, Snider NL. The quick, simple measurement of intraocular lens power and lens resolution at surgery. J Am Intraocul Implant Soc 1978;4:15–17.
11. Barkana Y, Gerber Y, Elbaz U, Schwartz S, Ken-Dror G, Avni I, et al. Central corneal thickness measurement with the Pentacam Scheimpflug system, optical low-coherence reflectometry pachymeter, and ultrasound pachymetry. J Cataract Refract Surg 2005;31:1729–1735.
12. Kanellopoulos AJ, Asimellis G. Comparison of highresolution Scheimpflug and high-frequency ultrasound biomicroscopy to anterior-segment OCT corneal thickness measurements. Clin Ophthalmol 2013;7:2239–2247.
13. Leung CK, Li H, Weinreb RN, Liu J, Cheung CY, Lai RY, et al. Anterior chamber angle measurement with anterior segment optical coherence tomography: A comparison between slit lamp OCT and Visante OCT. Invest Ophthalmol Vis Sci 2008;49:3469–3474.