Intraocular lens power calculation after radial keratotomy: Estimating the refractive corneal power

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Abstract

Purpose: To evaluate the most accurate method for corneal power determination in patients with previous radial keratotomy (RK). Setting: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. Methods: A retrospective review of data for 16 eyes of 14 patients with a history of RK and subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation was performed. Outcome measures included axial length, postoperative topography, type and power of IOL implanted, and postoperative spherical equivalent (SE) refraction at 3 to 6 months. Average central corneal power (ACCP) was defined as the average of the mean powers of the central Placido rings. For each eye, simulated K-readings and different values of ACCP computed corresponding to different central corneal diameters were used in each case, along with the implanted IOL power, to back-calculate the SE refraction (Ref) via the double-K adjusted Holladay 1 IOL formula. The predicted refractive error was hence computed as (Ref - SE), both in algebraic and absolute values. Results: The ACCP over the central 3.0 mm (ACCP3mm) yielded the lowest absolute predicted refractive error (0.25 ± 0.38 diopters [D]), which was statistically lower than the error for ACCP1mm (P<.001) and for the simulated K-value (P = .033). It also resulted in 87.5% of eyes being within ±0.50 D and 100% within ±1.00 D of the actual postoperative refraction. Conclusions: Corneal refractive power after RK was best described by averaging the topographic data of the central 3.0 mm area. Applying this method, together with a double-K IOL formula, achieved excellent IOL power predictability.

Original languageEnglish (US)
Pages (from-to)1045-1050
Number of pages6
JournalJournal of Cataract and Refractive Surgery
Volume33
Issue number6
DOIs
StatePublished - Jun 2007

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Radial Keratotomy
Intraocular Lenses
Refractive Errors
Birefringence
Intraocular Lens Implantation
Phacoemulsification
Reading
Outcome Assessment (Health Care)

ASJC Scopus subject areas

  • Ophthalmology

Cite this

@article{b27f082b9c554ca4b911d280b4200564,
title = "Intraocular lens power calculation after radial keratotomy: Estimating the refractive corneal power",
abstract = "Purpose: To evaluate the most accurate method for corneal power determination in patients with previous radial keratotomy (RK). Setting: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. Methods: A retrospective review of data for 16 eyes of 14 patients with a history of RK and subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation was performed. Outcome measures included axial length, postoperative topography, type and power of IOL implanted, and postoperative spherical equivalent (SE) refraction at 3 to 6 months. Average central corneal power (ACCP) was defined as the average of the mean powers of the central Placido rings. For each eye, simulated K-readings and different values of ACCP computed corresponding to different central corneal diameters were used in each case, along with the implanted IOL power, to back-calculate the SE refraction (Ref) via the double-K adjusted Holladay 1 IOL formula. The predicted refractive error was hence computed as (Ref - SE), both in algebraic and absolute values. Results: The ACCP over the central 3.0 mm (ACCP3mm) yielded the lowest absolute predicted refractive error (0.25 ± 0.38 diopters [D]), which was statistically lower than the error for ACCP1mm (P<.001) and for the simulated K-value (P = .033). It also resulted in 87.5{\%} of eyes being within ±0.50 D and 100{\%} within ±1.00 D of the actual postoperative refraction. Conclusions: Corneal refractive power after RK was best described by averaging the topographic data of the central 3.0 mm area. Applying this method, together with a double-K IOL formula, achieved excellent IOL power predictability.",
author = "Awwad, {Shady T.} and Surendar Dwarakanathan and Bowman, {Robert W} and Cavanagh, {Harrison D} and Steven Verity and Venkateswara Mootha and McCulley, {James P}",
year = "2007",
month = "6",
doi = "10.1016/j.jcrs.2007.03.018",
language = "English (US)",
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TY - JOUR

T1 - Intraocular lens power calculation after radial keratotomy

T2 - Estimating the refractive corneal power

AU - Awwad, Shady T.

AU - Dwarakanathan, Surendar

AU - Bowman, Robert W

AU - Cavanagh, Harrison D

AU - Verity, Steven

AU - Mootha, Venkateswara

AU - McCulley, James P

PY - 2007/6

Y1 - 2007/6

N2 - Purpose: To evaluate the most accurate method for corneal power determination in patients with previous radial keratotomy (RK). Setting: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. Methods: A retrospective review of data for 16 eyes of 14 patients with a history of RK and subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation was performed. Outcome measures included axial length, postoperative topography, type and power of IOL implanted, and postoperative spherical equivalent (SE) refraction at 3 to 6 months. Average central corneal power (ACCP) was defined as the average of the mean powers of the central Placido rings. For each eye, simulated K-readings and different values of ACCP computed corresponding to different central corneal diameters were used in each case, along with the implanted IOL power, to back-calculate the SE refraction (Ref) via the double-K adjusted Holladay 1 IOL formula. The predicted refractive error was hence computed as (Ref - SE), both in algebraic and absolute values. Results: The ACCP over the central 3.0 mm (ACCP3mm) yielded the lowest absolute predicted refractive error (0.25 ± 0.38 diopters [D]), which was statistically lower than the error for ACCP1mm (P<.001) and for the simulated K-value (P = .033). It also resulted in 87.5% of eyes being within ±0.50 D and 100% within ±1.00 D of the actual postoperative refraction. Conclusions: Corneal refractive power after RK was best described by averaging the topographic data of the central 3.0 mm area. Applying this method, together with a double-K IOL formula, achieved excellent IOL power predictability.

AB - Purpose: To evaluate the most accurate method for corneal power determination in patients with previous radial keratotomy (RK). Setting: University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. Methods: A retrospective review of data for 16 eyes of 14 patients with a history of RK and subsequent phacoemulsification and posterior chamber intraocular lens (IOL) implantation was performed. Outcome measures included axial length, postoperative topography, type and power of IOL implanted, and postoperative spherical equivalent (SE) refraction at 3 to 6 months. Average central corneal power (ACCP) was defined as the average of the mean powers of the central Placido rings. For each eye, simulated K-readings and different values of ACCP computed corresponding to different central corneal diameters were used in each case, along with the implanted IOL power, to back-calculate the SE refraction (Ref) via the double-K adjusted Holladay 1 IOL formula. The predicted refractive error was hence computed as (Ref - SE), both in algebraic and absolute values. Results: The ACCP over the central 3.0 mm (ACCP3mm) yielded the lowest absolute predicted refractive error (0.25 ± 0.38 diopters [D]), which was statistically lower than the error for ACCP1mm (P<.001) and for the simulated K-value (P = .033). It also resulted in 87.5% of eyes being within ±0.50 D and 100% within ±1.00 D of the actual postoperative refraction. Conclusions: Corneal refractive power after RK was best described by averaging the topographic data of the central 3.0 mm area. Applying this method, together with a double-K IOL formula, achieved excellent IOL power predictability.

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