Intraocular lens power calculation after corneal refractive surgery

Department of Ophthalmology, Wilmer Ophthalmologic Institute, Johns Hopkins School of Medicine, Baltimore, Maryland 21287, USA.
Current opinion in ophthalmology (Impact Factor: 2.5). 08/2008; 19(4):357-62. DOI: 10.1097/ICU.0b013e3282fec43e
Source: PubMed


Corneal refractive procedures have become increasingly popular over the past decade, allowing patients to have excellent uncorrected visual acuity and spectacle independence. As these individuals mature, many will eventually undergo cataract surgery. With the advances in modern cataract surgery and lens implant technology, particularly presbyopic intraocular lens implants, patients and physicians have greater expectations regarding visual outcomes and independence from glasses after cataract surgery. Therefore, it is important to understand methods to accurately determine intraocular lens power calculation after keratorefractive procedures to avoid refractive surprises and patient dissatisfaction.
In this review article, we provide an overview of intraocular lens power determination after corneal refractive surgery, highlighting sources of errors and potential methods to improve the accuracy of the lens power estimation.
Newer methods to address errors in intraocular lens power calculations after keratorefractive surgery represent a paradigm shift from the previous gold standard of the clinical history method. Understanding the advantages and limitations of the various methods may be beneficial in obtaining more accurate estimations of the intraocular lens power after corneal refractive surgery, resulting in improved visual outcomes.

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    ABSTRACT: Cataract surgery is a technique described since recorded history, yet it has greatly evolved only in the latter half of the past century. The development of the intraocular lens and phacoemulsification as a technique for cataract removal could be considered as the two most significant strides that have been made in this surgical field. This review takes a comprehensive look at all aspects of cataract surgery, starting from patient selection through the process of consent, anaesthesia, biometry, lens power calculation, refractive targeting, phacoemulsification, choice of intraocular lens and management of complications, such as posterior capsular opacification, as well as future developments. As the most common ophthalmic surgery and with the expanding range of intraocular lens options, optometrists have an important and growing role in managing patients with cataract.
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    ABSTRACT: To review recent contributions addressing the challenge of intraocular lens (IOL) calculation in patients undergoing cataract extraction following corneal refractive surgery. Although several articles have provided excellent summaries of IOL selection in patients wherein prerefractive surgery data are available, numerous authors have recently described approaches to attempt more accurate IOL power calculations for patients who present with no reliable clinical information regarding their refractive history. Additionally, results have been reported using the Scheimpflug camera system to measure corneal power in an attempt to resolve the most important potential source of error for IOL determination in these patients. IOL selection in patients undergoing cataract surgery after corneal refractive surgery continues to be a challenging and complex issue despite numerous strategies and formulas described in the literature. Current focus seems to be directed toward approaches that do not require preoperative refractive surgery information. Due to the relative dearth of comparative clinical outcomes data, the optimal solution to this ongoing clinical problem has yet to be determined. Until such data are available, many cataract surgeons compare the results of multiple formulas to assist them in IOL selection for these patients.
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    ABSTRACT: To assess the accuracy of Pentacam Scheimpflug camera for corneal power measurement in eyes with previous photorefractive keratectomy for myopia. In this comparative interventional case series, 35 eyes of 35 patients who had myopic photorefractive keratectomy were studied. Corneal power was measured by conventional topography and Pentacam Scheimpflug camera, and equivalent keratometry readings (EKR) in different central corneal rings (0.5 to 4.5 mm), true net power and simulated keratometry (K) measurements as well as those obtained using Shammas no-history, Koch-Maloney and Haigis methods were compared with clinical history method. All corneal power measurements except for the topography simulated K and true net power values were statistically similar to the clinical history values. Simulated keratometry and 4.5-mm EKR values were more closely correlated with clinical history method. Shammas formula, Pentacam simulated K and 3-, 4- and 4.5-mm EKR provided a 95% confidence interval within +/-0.50 D of the mean clinical history method value, among these, the width of the 95% limits of agreement (LoA) was narrower for Shammas and Pentacam simulated K and 4.5-mm EKR values; however, considerably large 95% LoA were found between each of these values and those obtained with the clinical history method. Estimated preoperative keratometry was statistically similar to the preoperative measurement; however, estimated refractive change was different from actual value. The Pentacam 4.5-mm EKR and simulated keratometry may be used as an alternative to clinical history method to predict corneal power when pre-keratorefractive surgery data are unavailable; however, wide LoA should be considered in the calculations.
    Clinical and Experimental Ophthalmology 05/2010; 38(4):341-5. DOI:10.1111/j.1442-9071.2010.02286.x · 2.35 Impact Factor
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