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Savage DE, Pantanelli SM. An update on intraocular lens power calculations in eyes with previous laser refractive surgery. Curr Opin Ophthalmol 2024; 35:34-43. [PMID: 37820078 DOI: 10.1097/icu.0000000000001004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
PURPOSE OF REVIEW There is an ever-growing body of research regarding intraocular lens (IOL) power calculations following photorefractive keratectomy (PRK), laser-assisted in-situ keratomileusis (LASIK), and small-incision lenticule extraction (SMILE). This review intends to summarize recent data and offer updated recommendations. RECENT FINDINGS Postmyopic LASIK/PRK eyes have the best refractive outcomes when multiple methods are averaged, or when Barrett True-K is used. Posthyperopic LASIK/PRK eyes also seem to do best when Barrett True-K is used, but with more variable results. With both aforementioned methods, using measured total corneal power incrementally improves results. For post-SMILE eyes, the first nontheoretical data favors raytracing. SUMMARY Refractive outcomes after cataract surgery in eyes with prior laser refractive surgery are less accurate and more variable compared to virgin eyes. Surgeons may simplify their approach to IOL power calculations in postmyopic and posthyperopic LASIK/PRK by using Barrett True-K, and employing measured total corneal power when available. For post-SMILE eyes, ray tracing seems to work well, but lack of accessibility may hamper its adoption.
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Affiliation(s)
- Daniel E Savage
- Department of Ophthalmology, David and Ilene Flaum Eye Institute
- Center for Visual Science, University of Rochester, Rochester, New York
| | - Seth M Pantanelli
- Department of Ophthalmology, Penn State College of Medicine, Hershey, Pennsylvania, USA
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Wang Z, Song Y, Yang W, Li D, Chen W, Zhao Q, Liu Q, Zhai C. Comparing Standard Keratometry and Total Keratometry Before and After Myopic Corneal Refractive Surgery With a Swept-Source OCT Biometer. Front Med (Lausanne) 2022; 9:928027. [PMID: 35903314 PMCID: PMC9318577 DOI: 10.3389/fmed.2022.928027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 06/13/2022] [Indexed: 11/29/2022] Open
Abstract
Background More recently, the swept-source OCT biometer-IOLMaster 700 has provided direct total corneal power measurement, named total keratometry. This study aims to evaluate whether standard keratometry (SK) and total keratometry (TK) with IOLMaster 700 can accurately reflect the corneal power changes induced by myopic corneal refractive surgery. Methods In this study, the biometric data measured with the swept-source OCT biometer—IOLMaster 700 before and 3 months after the myopic corneal refractive surgery were recorded. The changes of biological parameters, including SK, posterior keratometry (PK), and TK, and the difference between SK and TK were compared. In addition, the changes of SK and TK induced by the surgery were compared with the changes of spherical equivalent at the corneal plane (ΔSEco). Results A total of 74 eyes (74 patients) were included. The changes of SK, PK, TK, axial length, anterior chamber depth, and lens thickness after refractive surgery were all statistically significant (all p < 0.01), while the change of white-to-white was not (p = 0.075). The difference between SK and TK was −0.03 ± 0.10D before the corneal refractive surgery and increased to −0.78 ± 0.26D after surgery. The changes of SK and the changes of TK induced by the surgery had a good correlation with the changes of SEco (r = 0.97). ΔSK was significantly smaller than ΔSEco, with a difference of −0.65 ± 0.54D (p < 0.01). However, the difference between ΔTK and ΔSEco (0.10 ± 0.50D) was not statistically significant (p = 0.08). Conclusions Using SK to reflect the changes induced by the myopic corneal refractive surgery may lead to underestimation, while TK could generate a more accurate result. The new parameter, TK, provided by the IOLMaster 700, appeared to provide an accurate, objective measure of corneal power that closely tracked the refractive change in corneal refractive surgery.
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Wang L, Koch D. Intraocular lens power calculations in eyes with previous corneal refractive surgery: Challenges, approaches, and outcomes. Taiwan J Ophthalmol 2022; 12:22-31. [PMID: 35399961 PMCID: PMC8988985 DOI: 10.4103/tjo.tjo_38_21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2021] [Accepted: 09/10/2021] [Indexed: 11/04/2022] Open
Abstract
In eyes with previous corneal refractive surgery, difficulties in accurately determining corneal refractive power and in predicting the effective lens position create challenges in intraocular lens (IOL) power calculations. There are three categories of methods proposed based on the use of historical data acquired prior to the corneal refractive surgery. The American Society of Cataract and Refractive Surgery postrefractive IOL calculator incorporates many commonly used methods. Accuracy of refractive prediction errors within ± 0.5 D is achieved in 0% to 85% of eyes with previous myopic LASIK/photorefractive keratectomy (PRK), 38.1% to 71.9% of eyes with prior hyperopic LASIK/PRK, and 29% to 87.5% of eyes with previous radial keratotomy. IOLs with negative spherical aberration (SA) may reduce the positive corneal SA induced by myopic correction, and IOLs with zero SA best match corneal SA in eyes with prior hyperopic correction. Toric, extended-depth-of-focus, and multifocal IOLs may provide excellent outcomes in selected cases that meet certain corneal topographic criteria. Further advances are needed to improve the accuracy of IOL power calculation in eyes with previous corneal refractive surgery.
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Wang L, Koch DD. Intraocular Lens Power Calculations in Eyes with Previous Corneal Refractive Surgery. Ophthalmology 2021; 128:e121-e131. [DOI: 10.1016/j.ophtha.2020.06.054] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 06/10/2020] [Accepted: 06/24/2020] [Indexed: 12/12/2022] Open
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Intraocular Lens power calculation after laser refractive surgery: A Meta-Analysis. Sci Rep 2020; 10:2645. [PMID: 32060303 PMCID: PMC7021678 DOI: 10.1038/s41598-020-59487-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 01/23/2020] [Indexed: 01/11/2023] Open
Abstract
There are an increasing number of people who have had refractive surgery now developing cataract. To compare the accuracy of different intraocular lens (IOL) power calculation formulas after laser refractive surgery (photorefractive keratectomy or laser in situ keratomileusis), a comprehensive literature search of PubMed and EMBASE was conducted to identify comparative cohort studies and case series comparing different formulas: Haigis-L, Shammas-PL, SRK/T, Holladay 1 and Hoffer Q. Seven cohort studies and three observational studies including 260 eyes were identified. There were significant differences when Hoffer Q formula compared with SRK/T, Holladay 1. Holladay 1 formula produced less prediction error than SRK/T formula in double-K method. Hoffer Q formula performed best among SRK/T and Holladay 1 formulas in total and single-K method. In eyes with previous data, it is recommended to choose double-K formula except SRK/T formula. In eyes with no previous data, Haigis-L formula is recommended if available, if the fourth formula is unavailable, single-k Hoffer Q is a good choice.
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Kim SJ, Cho HK, Park YM, Han YS, Park JM. Corneal topography and angle parameters after laser iridotomy combined with iridoplasty assessed by dual Scheimpflug analyzer. Int Ophthalmol 2019; 40:447-457. [PMID: 31720953 DOI: 10.1007/s10792-019-01205-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/22/2019] [Indexed: 12/19/2022]
Abstract
PURPOSE To investigate the changes in corneal topography including parameters such as corneal curvature and corneal aberrations, along with anterior chamber angle (ACA) after laser iridotomy (LI) combined with peripheral iridoplasty (PI) using dual Scheimpflug analyzer. METHODS In this prospective observational study, dual Scheimpflug analyzer images were acquired before and 1 week after LI plus PI. Corneal curvature of both axial and instantaneous maps from anterior and posterior surface, respectively, and total corneal power (TCP) were acquired. These corneal parameters from three zones (central, middle, and peripheral) and total corneal wavefront aberration, trefoil, and coma were obtained. The ACA from four quadrants, anterior chamber depth (ACD), anterior chamber volume (ACV), and intraocular pressure (IOP) were also inspected. RESULTS ACD increased significantly from 2.15 ± 0.25 to 2.18 ± 0.24 mm (P = 0.002). ACV and ACA from all four quadrants increased significantly after the laser treatment (all P < 0.05). IOP decreased significantly from 16.9 ± 3.1 to 14.7 ± 2.9 mmHg following LI plus PI (P = 0.000). No significant changes were detected in corneal axial and instantaneous curvature from three zones on the anterior and posterior corneal surface after LI plus PI (all P > 0.05). The TCP, total corneal wavefront aberration, trefoil, and coma also revealed no significant changes after the laser procedure (all P > 0.05). CONCLUSIONS Treatment with LI combined with PI did not affect the corneal topographic parameters from both anterior and posterior surfaces. However, LI plus PI improved ACA parameters significantly and effectively.
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Affiliation(s)
- Su Jin Kim
- Department of Ophthalmology, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Republic of Korea
| | - Hyun-Kyung Cho
- Department of Ophthalmology, Gyeongsang National University Changwon Hospital, Gyeongsang National University, School of Medicine, 11 Samjeongja-ro, Seongsan-gu, Changwon, Gyeongsangnam-do, 51472, Republic of Korea. .,Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju, Republic of Korea.
| | - Young Min Park
- Department of Ophthalmology, Gyeongsang National University Changwon Hospital, Gyeongsang National University, School of Medicine, 11 Samjeongja-ro, Seongsan-gu, Changwon, Gyeongsangnam-do, 51472, Republic of Korea
| | - Yong Seop Han
- Department of Ophthalmology, Gyeongsang National University Changwon Hospital, Gyeongsang National University, School of Medicine, 11 Samjeongja-ro, Seongsan-gu, Changwon, Gyeongsangnam-do, 51472, Republic of Korea
| | - Jong Moon Park
- Department of Ophthalmology, Gyeongsang National University Hospital, Gyeongsang National University, School of Medicine, Jinju, Republic of Korea.,Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju, Republic of Korea
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Wu Y, Liu S, Liao R. Prediction accuracy of intraocular lens power calculation methods after laser refractive surgery. BMC Ophthalmol 2017; 17:44. [PMID: 28390411 PMCID: PMC5385019 DOI: 10.1186/s12886-017-0439-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 04/05/2017] [Indexed: 11/14/2022] Open
Abstract
Background This study aimed to evaluate the prediction accuracy of postoperative refractions using partial coherence interferometry (IOL-Master) and applanation ultrasound (AL-3000) assisted with corneal topography (TMS-4) in eyes that had undergone myopic laser-assisted in situ keratomileusis (LASIK). Methods Haigis-L formula, Koch–Maloney method using Haigis formula, Shammas clinically derived K-value (simulated keratometric value) correction (Shammas c.d.) using Haigis formula, and Shammas post-LASIK (Shammas-PL) formula were used in eyes with myopic LASIK. Constants were derived from the optimized constants in 133 virgin eyes. Refractive outcomes were determined by streak retinoscopy and subjective manifest refraction. Methods and formulas were evaluated by mean error (ME), standard deviation (SD), range of error, mean absolute error (MAE), median absolute error, 95% confidence interval of MAE, and percentage of eyes within ±0.5 diopter (D), ±1.0 D, and ±1.5 D of prediction. Results SDs of the Haigis-L, Koch-Maloney method using the Haigis formula, Shammas c.d. using the Haigis formula, and the Shammas-PL formula using IOL-Master were 0.721, 0.695, 0.695, and 0.698; and those using AL-3000 assisted with TMS-4 were 0.782, 0.741, 0.743, and 0.778, respectively. Conclusions No-history methods that corrected corneal power with measurements using IOL-Master were promising in myopic post-LASIK eyes, but still a gap in prediction accuracy exists between virgin eyes and post-LASIK eyes. Electronic supplementary material The online version of this article (doi:10.1186/s12886-017-0439-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yubo Wu
- Department of Ophthalmology, The First Affiliated Hospital of Anhui Medical University, No. 218 Jixi Road, Hefei, Anhui, 230022, China
| | - Songyu Liu
- Department of Ultrasound, The First Affiliated Hospital of Anhui Medical University, No. 218 Jixi Road, Hefei, Anhui, 230022, China
| | - Rongfeng Liao
- Department of Ophthalmology, The First Affiliated Hospital of Anhui Medical University, No. 218 Jixi Road, Hefei, Anhui, 230022, China.
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Myopic Laser Corneal Refractive Surgery Reduces Interdevice Agreement in the Measurement of Anterior Corneal Curvature. Eye Contact Lens 2017; 44 Suppl 1:S151-S157. [PMID: 28346277 DOI: 10.1097/icl.0000000000000364] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To investigate interdevice differences and agreement in the measurement of anterior corneal curvature obtained by different technologies after laser corneal refractive surgery. METHODS The prospective study comprised 109 eyes of 109 consecutive patients who had undergone laser-assisted in situ keratomileusis (LASIK). Preoperative and postoperative corneal parameters were measured by Scheimpflug imaging (Pentacam), Placido-slit-scanning (Orbscan) and auto-keratometry (IOLMaster). Preoperative and postoperative anterior corneal curvatures (K readings) were compared between devices. Interdevice agreement was evaluated by Bland-Altman analysis. RESULTS Preoperatively, the difference of K reading for Pentacam-IOLMaster (0.04±0.20 D) was not statistically significant (P=0.059). The differences between Pentacam-Orbscan and Orbscan-IOLMaster were 0.20±0.34 D (P<0.001) and -0.17±0.29 D (P<0.001), respectively. After surgery, no difference was found for Pentacam-Orbscan (-0.05±0.38, P=0.136). The differences between Pentacam-IOLMaster and Orbscan-IOLMaster were 0.13±0.29 D (P<0.001) and 0.19±0.34 D (P<0.001). Preoperative interdevice agreement (95% limit of agreement [LOA]) between Pentacam and Orbscan, Pentacam and IOLMaster, and Orbscan and IOLMaster were 1.31 D, 0.79 D and 1.14 D, respectively. The 95% LOAs decreased to 1.47 D, 1.14 D, and 1.34 D after refractive surgery. CONCLUSION Corneal refractive surgery changed the preoperative and postoperative interdevice differences in corneal curvature measurements and reduced interdevice agreement, indicating that the devices are not interchangeable.
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Fouad M, El Din Farahat H, Said Ahmed K, Gad Marey H. Intraocular lens master optical biometry versus conventional ultrasound biometry in intraocular lens power calculations in highly myopic eyes. ACTA ACUST UNITED AC 2017. [DOI: 10.4103/1110-2098.215434] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Corneal topographic alterations after selective laser trabeculoplasty. Int Ophthalmol 2016; 37:905-910. [PMID: 27628588 DOI: 10.1007/s10792-016-0348-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 09/06/2016] [Indexed: 12/19/2022]
Abstract
PURPOSE To investigate the presence of corneal alterations in the long term among patients with primary open-angle glaucoma (POAG) after a single session of selective laser trabeculoplasty (SLT) treatment. MATERIALS AND METHODS The files of the POAG patients who had been treated with SLT were evaluated retrospectively. The Pretreatment Scheimpflug corneal topographic (SCT) findings were then compared with the post-treatment findings. RESULTS The files of 33 patients were eligible. The changes in central corneal thickness, thinnest point of cornea, and posterior corneal asphericity at 5 and 8 mm were statistically significant (p = 0.03, 0.01, 0.02, and 0.04 respectively). On the other hand, the simulated K, anterior 3 mm K, anterior 5 mm K, posterior 3 mm K, posterior 5 mm K, anterior asphericity at 3 mm, posterior asphericity at 3 mm, and Zernike values did not change significantly following the treatment (p = 0.19, 0.08, 0.1, 0.3, 0.2, 0.75, 0.09, and 0.3 respectively). CONCLUSION SLT can slightly alter pretreatment SCT findings in 3-6 months. Clinicians should wait for at least 6 months after SLT before performing any subsequent surgeries that depend on corneal parameters.
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Alio JL, Abdelghany AA, Abdou AA, Maldonado MJ. Cataract surgery on the previous corneal refractive surgery patient. Surv Ophthalmol 2016; 61:769-777. [PMID: 27423631 DOI: 10.1016/j.survophthal.2016.07.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 07/05/2016] [Accepted: 07/07/2016] [Indexed: 11/26/2022]
Abstract
Cataract surgery in cases with previous corneal refractive surgery may be a major challenge for the ophthalmologist. The refractive outcome of the case deserves special attention in the preoperative planning process, which should be tailored for the type of prior refractive procedure: incisional, ablative under a flap, or on the corneal surface. Avoiding refractive surprise after cataract surgery in these cases is principally dependent on the accuracy of the intraocular lens calculation, together with the selection of the appropriate biometric formula for each case. Modern techniques for cataract surgery help surgeons to move toward the goal of cataract surgery as a refractive procedure free from refractive error. We give practical guidelines for the cataract surgeon in the management of these challenging cases.
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Affiliation(s)
- Jorge L Alio
- Vissum Corporación, Alicante, Spain; Division of Ophthalmology, Universidad Miguel Hernández, Alicante, Spain.
| | - Ahmed A Abdelghany
- Ophthalmology Department, Faculty of Medicine, Minia University, Minia, Egypt
| | - Ahmed A Abdou
- Ophthalmology Department, AUH, Assiut University, Assiut, Egypt
| | - M J Maldonado
- IOBA-Eye Institute, Valladolid, Spain; Division of Ophthalmology, University of Valladolid, Valladolid, Spain
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Evaluation of Equivalent Keratometry Readings Obtained by Pentacam HR (High Resolution). PLoS One 2016; 11:e0150121. [PMID: 26950834 PMCID: PMC4780706 DOI: 10.1371/journal.pone.0150121] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 02/09/2016] [Indexed: 11/20/2022] Open
Abstract
Purpose To assess the repeatability of Equivalent Keratometry Readings (EKRs) obtained by the Pentacam HR (high resolution) in untreated and post-LASIK eyes, and to compare them with the keratometry (K) values obtained by other algorithms. Methods In this prospective study, 100 untreated eyes and 71 post-LASIK eyes were included. In the untreated group, each eye received 3 consecutive scans using the Pentacam HR, and EKR values in all central corneal zone, the true net power (Knet) and the simulated K (SimK) were obtained for each scan. In the post-LASIK group, each eye received subjective refraction and 3 consecutive scans with the Pentacam HR preoperatively. During the 3-month post-surgery exam, the same examinations and the use of an IOLMaster were conducted for each eye. The EKRs in all zone, the Knet, the mean K (Km) by IOLMaster and the K values by clinical history method (KCHM) were obtained. The repeatability of the EKRs was assessed by the within-subject standard deviation (Sw), 2.77Sw, coefficient of variation (CVw) and intraclass correlation coefficient (ICC). The bonferroni corrected multiple comparisons were performed to analyze the differences among the EKRs and K values calculated by other algorithms within the 2 groups. The 95% limits of agreement (LoA) were calculated. Results The EKR values in all central corneal zone were repeatable in both the untreated group (Sw≦0.19 D, 2.77Sw≦0.52 D, CVw≦1%, ICC≧0.978) and the post-LASIK group (Sw≦0.22 D, 2.77Sw≦0.62 D, CVw≦1%, ICC≧0.980). In the untreated group, the EKR in 4mm zone was close to SimK (P = 1.000), and the 95% LoA was (-0.13 to 0.15 D). The difference between Knet and SimK was -1.30±0.13 D (95% LoA -1.55 to -1.55 D, P<0.001). In the post-LASIK group, all the EKRs were significantly higher than KCHM (all P<0.001). The differences between the EKR in 4mm zone and KCHM, the EKR in 7mm zone and KCHM, Knet and KCHM, Km and KCHM, SimK and Knet were 0.64±0.50 D (95% LoA, -0.33 to 1.62 D), 1.77±0.88 D (95% LoA, 0.04 to 3.51 D), -0.98±0.48 D (95% LoA, -1.92 to -0.04 D), 0.64±0.53 D (95% LoA, -0.40 to 1.68 D), and 1.73±0.20 D (95% LoA, 1.33 to 2.13 D), respectively. Conclusions The EKRs obtained by the Pentacam HR were repeatable in both untreated eyes and post-LASIK eyes. Compared to the total corneal power obtained by the clinical history method, the EKR values generally overestimated the total corneal power in post-LASIK eyes. So, further calibrations for the EKR values should be conducted, before they were used for the total corneal power assessment in post-LASIK eyes.
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New algorithm for intraocular lens power calculations after myopic laser in situ keratomileusis based on rotating Scheimpflug camera data. J Cataract Refract Surg 2015; 41:339-47. [DOI: 10.1016/j.jcrs.2014.05.040] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Revised: 05/08/2014] [Accepted: 05/09/2014] [Indexed: 11/19/2022]
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New approach for correction of error associated with keratometric estimation of corneal power in keratoconus. Cornea 2014; 33:960-7. [PMID: 25090162 DOI: 10.1097/ico.0000000000000190] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE The aim of this study was to obtain the exact value of the keratometric index (nkexact) and to clinically validate a variable keratometric index (nkadj) that minimizes this error. METHODS The nkexact value was determined by obtaining differences (ΔPc) between keratometric corneal power (Pk) and Gaussian corneal power ((Equation is included in full-text article.)) equal to 0. The nkexact was defined as the value associated with an equivalent difference in the magnitude of ΔPc for extreme values of posterior corneal radius (r2c) for each anterior corneal radius value (r1c). This nkadj was considered for the calculation of the adjusted corneal power (Pkadj). Values of r1c ∈ (4.2, 8.5) mm and r2c ∈ (3.1, 8.2) mm were considered. Differences of True Net Power with (Equation is included in full-text article.), Pkadj, and Pk(1.3375) were calculated in a clinical sample of 44 eyes with keratoconus. RESULTS nkexact ranged from 1.3153 to 1.3396 and nkadj from 1.3190 to 1.3339 depending on the eye model analyzed. All the nkadj values adjusted perfectly to 8 linear algorithms. Differences between Pkadj and (Equation is included in full-text article.)did not exceed ±0.7 D (Diopter). Clinically, nk = 1.3375 was not valid in any case. Pkadj and True Net Power and Pk(1.3375) and Pkadj were statistically different (P < 0.01), whereas no differences were found between (Equation is included in full-text article.)and Pkadj (P > 0.01). CONCLUSIONS The use of a single value of nk for the calculation of the total corneal power in keratoconus has been shown to be imprecise, leading to inaccuracies in the detection and classification of this corneal condition. Furthermore, our study shows the relevance of corneal thickness in corneal power calculations in keratoconus.
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Ianchulev T, Hoffer KJ, Yoo SH, Chang DF, Breen M, Padrick T, Tran DB. Intraoperative Refractive Biometry for Predicting Intraocular Lens Power Calculation after Prior Myopic Refractive Surgery. Ophthalmology 2014; 121:56-60. [DOI: 10.1016/j.ophtha.2013.08.041] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2013] [Revised: 08/15/2013] [Accepted: 08/28/2013] [Indexed: 11/29/2022] Open
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Xu K, Hao Y, Qi H. Intraocular lens power calculations using a Scheimpflug camera to measure corneal power. Biotech Histochem 2013; 89:348-54. [DOI: 10.3109/10520295.2013.867532] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Algorithm for Correcting the Keratometric Error in the Estimation of the Corneal Power in Eyes With Previous Myopic Laser Refractive Surgery. Cornea 2013; 32:1454-9. [DOI: 10.1097/ico.0b013e31829e1eb5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Jin H, Auffarth GU, Guo H, Zhao P. Corneal power estimation for intraocular lens power calculation after corneal laser refractive surgery in Chinese eyes. J Cataract Refract Surg 2012; 38:1749-57. [PMID: 22925179 DOI: 10.1016/j.jcrs.2012.06.048] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 06/04/2012] [Accepted: 06/05/2012] [Indexed: 11/29/2022]
Affiliation(s)
- Haiying Jin
- Department of Ophthalmology, Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine, Shanghai, China
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Abstract
PURPOSE OF REVIEW Obtaining precise postoperative target refraction is of utmost importance in today's modern cataract and refractive surgery. Given the growing number of patients undergoing premium intraocular lens (IOL) implantations, patient expectation continues to rise. In order to meet heightened patient expectations, it is crucial to pay utmost attention to patient selection, accurate keratometry and biometry readings, as well as to the application of correct IOL power formula with optimized lens constants. This article reviews recent advances in the field of clinical biometry and IOL power calculations. RECENT FINDINGS Recently developed low-coherence reflectometry optical biometry is comparable to older ultrasonic biometric and keratometric techniques. In addition, the new IOLMaster software upgrade has improved reproducibility and enhanced signal acquisition. Further, the modern lens power formulas currently determine the effective lens position and the shape of the intraocular lens power prediction curve more accurately. SUMMARY In order to reach target refraction, precise biometric measurements are imperative. Understanding the strengths and limitations of the currently available biometry devices allows prevention of high variability and inaccuracy, ultimately determining the refractive outcomes.
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Comparison of anterior segment measurements by 3 Scheimpflug tomographers and 1 Placido corneal topographer. J Cataract Refract Surg 2012; 37:1679-85. [PMID: 21855765 DOI: 10.1016/j.jcrs.2011.03.055] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Revised: 02/28/2011] [Accepted: 03/08/2011] [Indexed: 11/22/2022]
Abstract
PURPOSE To compare the anterior segment measurements provided by 3 Scheimpflug tomographers and a Placido corneal topographer. SETTING Private clinical ophthalmology practice. DESIGN Evaluation of diagnostic test or technology. METHODS In a sample of 25 consecutive patients having either refractive or cataract surgery, the anterior eye segment was analyzed by means of a rotating Scheimpflug camera (Pentacam), 2 devices with a Scheimpflug camera combined with a Placido disk (Sirius and TMS-5), and a Placido disk corneal topographer (Keratron). Measurement results were compared using analysis of variance. Agreement was assessed using Bland-Altman plots. RESULTS The mean simulated keratometry (K) was different between the 4 instruments (P<.0001), with Keratron providing the highest value (44.43 diopters [D] ± 1.28 [SD]). The Pentacam and Sirius provided the lowest values (44.05 ± 1.21 D and 44.05 ± 1.27 D, respectively), without statistical difference (posttest). The mean posterior corneal power and minimum corneal thickness were statistically different between the 3 Scheimpflug cameras (P<.0001 and P=.0210, respectively); 95% limits of agreement, however, were narrow for posterior corneal power and large for corneal thickness. The only 2 devices measuring the distance between the corneal endothelium and the anterior lens surface showed a statistically but not clinically significant difference (2.90 ± 0.48 mm and 2.94 ± 0.47 mm, respectively). There were no statistically significant differences in anterior corneal asphericity between the 4 instruments. CONCLUSION Although the measurements of some parameters by different instruments were similar, caution is warranted before using them interchangeably.
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Savini G, Carbonelli M, Barboni P, Hoffer KJ. Repeatability of automatic measurements performed by a dual Scheimpflug analyzer in unoperated and post-refractive surgery eyes. J Cataract Refract Surg 2011; 37:302-9. [DOI: 10.1016/j.jcrs.2010.07.039] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Revised: 07/30/2010] [Accepted: 07/30/2010] [Indexed: 11/29/2022]
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Jin H, Limberger IJ, Ehmer A, Guo H, Auffarth GU. Impact of axis misalignment of toric intraocular lenses on refractive outcomes after cataract surgery. J Cataract Refract Surg 2010; 36:2061-72. [DOI: 10.1016/j.jcrs.2010.06.066] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2010] [Revised: 06/23/2010] [Accepted: 06/24/2010] [Indexed: 11/15/2022]
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