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McNeely RN, McGinnity K, Stewart S, Pazo EE, Moutari S, Moore JE. A Multi Comparison of 8 Different Intraocular Lens Biometry Formulae, Including a Machine Learning Thin Lens Formula (MM) and an Inbuilt Anterior Segment Optical Coherence Tomography Ray Tracing Formula. Vision (Basel) 2024; 8:49. [PMID: 39311317 PMCID: PMC11417848 DOI: 10.3390/vision8030049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2024] [Revised: 08/23/2024] [Accepted: 08/26/2024] [Indexed: 09/26/2024] Open
Abstract
A comparison of the accuracy of intraocular lens (IOL) power calculation formulae, including SRK/T, HofferQ, Holladay 1, Haigis, MM, Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO), and AS-OCT ray tracing, was performed. One hundred eyes implanted with either the Rayone EMV RAO200E (Rayner Intraocular Lenses Limited, Worthing, UK) or the Artis Symbiose (Cristalens Industrie, Lannion, France) IOL were included. Biometry was obtained using IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany) and MS-39 AS-OCT (CSO, Firenze, Italy). Mean (MAE) and median (MedAE) absolute errors and percentage of eyes within ±0.25D, ±0.50D, ±0.75D, and ±1.00D of the target were compared, with ±0.75D considered a key metric. The highest percentage within ±0.75D was found with MM (96%) followed by the Haigis (94%) for the enhanced monofocal IOL. SRK/T (94%) had the highest percentage within ±0.75D, followed by Holladay 1, MM, BUII, and ray tracing (all 90%) for the multifocal IOL. No statistically significant difference in MAE was found with both IOLs. EVO showed the lowest MAE for the enhanced monofocal and ray tracing for the multifocal IOL. EVO and ray tracing showed the lowest MedAE for the two respective IOLs. A similar performance with high accuracy across formulae was found. MM and ray tracing appear to have similar accuracy to the well-established formulae and displayed a high percentage of eyes within ±0.75D.
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Affiliation(s)
| | - Katherine McGinnity
- Department of Ophthalmology, Belfast Health and Social Care Trust, Belfast BT12 6BA, UK
| | | | - Emmanuel Eric Pazo
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
| | - Salissou Moutari
- Mathematical Sciences Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK;
| | - Jonathan E. Moore
- Cathedral Eye Clinic, Belfast BT1 2LS, UK
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin 300384, China
- College of Health and Life Sciences, Aston University, Birmingham B4 7ET, UK
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Lischke R, Wiltfang R, Bechmann M, Kreutzer TC, Priglinger SG, Dirisamer M, Luft N. Intraocular lens power calculation using total keratometry and ray tracing in eyes with previous small incision lenticule extraction - A case series. Am J Ophthalmol Case Rep 2024; 34:102037. [PMID: 38487335 PMCID: PMC10937105 DOI: 10.1016/j.ajoc.2024.102037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 01/24/2024] [Accepted: 02/28/2024] [Indexed: 03/17/2024] Open
Abstract
Purpose To assess the IOL power calculation accuracy in post-SMILE eyes using ray tracing and a range of total keratometry based IOL calculation formulae. Observations Ray tracing showed excellent predictability in IOL power calculation after SMILE and its accuracy was clinically comparable with the Barrett TK Universal II and Haigis TK formula. Conclusions and importance Incorporating posterior corneal curvature measurements into IOL power calculation after SMILE seems prudent. The ray tracing method as well as selected TK-based formulae yielded excellent accuracy and should be favored in post-SMILE eyes.
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Affiliation(s)
- Roman Lischke
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany
- Department of Ophthalmology and Optometry, Medical University of Innsbruck, Austria
| | - Rainer Wiltfang
- SMILE Eyes Clinic, Munich, Germany
- SMILE Eyes Clinic, Trier, Germany
| | - Martin Bechmann
- SMILE Eyes Clinic, Munich, Germany
- SMILE Eyes Clinic, Trier, Germany
| | | | - Siegfried G. Priglinger
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany
- SMILE Eyes Clinic, Austria
| | - M. Dirisamer
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany
- SMILE Eyes Clinic, Austria
| | - Nikolaus Luft
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany
- SMILE Eyes Clinic, Austria
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Wei Y, Liu Y, Li H, Song H. Theoretical Accuracy of the Raytracing Method for Intraocular Calculation of Lens Power in Myopic Eyes after Small Incision Extraction of the Lenticule. Klin Monbl Augenheilkd 2024; 241:221-229. [PMID: 37722612 PMCID: PMC10898958 DOI: 10.1055/a-2177-4998] [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: 09/20/2023]
Abstract
AIM To evaluate the accuracy of the raytracing method for the calculation of intraocular lens (IOL) power in myopic eyes after small incision extraction of the lenticule (SMILE). METHODS Retrospective study. All patients undergoing surgery for myopic SMILE between May 1, 2020, and December 31, 2020, with Scheimpflug tomography optical biometry were eligible for inclusion. Manifest refraction was performed before and 6 months after refractive surgery. One eye from each patient was included in the final analysis. A theoretical model was invited to predict the accuracy of multiple methods of lens power calculation by comparing the IOL-induced refractive error at the corneal plane (IOL-Dif) and the SMILE-induced change of spherical equivalent (SMILE-Dif) before and after SMILE surgery. The prediction error (PE) was calculated as the difference between SMILE-Dif-IOL-Dif. IOL power calculations were performed using raytracing (Olsen Raytracing, Pentacam AXL, software version 1.22r05, Wetzlar, Germany) and other formulae with historical data (Barrett True-K, Double-K SRK/T, Masket, Modified Masket) and without historical data (Barrett True-K no history, Haigis-L, Hill Potvin Shammas PM, Shammas-PL) for the same IOL power and model. In addition, subgroup analysis was performed in different anterior chamber depths, axial lengths, back-to-front corneal radius ratio, keratometry, lens thickness, and preoperative spherical equivalents. RESULTS A total of 70 eyes of 70 patients were analyzed. The raytracing method had the smallest mean absolute PE (0.26 ± 0.24 D) and median absolute PE (0.16 D), and also had the largest percentage of eyes within a PE of ± 0.25 D (64.3%), ± 0.50 D (81.4%), ± 0.75 D (95.7%), and ± 1.00 D (100.0%). The raytracing method was significantly better than Double-K SRK/T, Haigis, Haigis-L, and Shammas-PL formulae in postoperative refraction prediction (all p < 0.001), but not better than the following formulae: Barrett True-K (p = 0.314), Barrett True-K no history (p = 0.163), Masket (p = 1.0), Modified Masket (p = 0.806), and Hill Potvin Shammas PM (p = 0.286). Subgroup analysis showed that refractive outcomes exhibited no statistically significant differences in the raytracing method (all p < 0.05). CONCLUSION Raytracing was the most accurate method in predicting target refraction and had a good consistency in calculating IOL power for myopic eyes after SMILE.
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Affiliation(s)
- Yinjuan Wei
- Department of Cataract, Tianjin Eye Hospital, Tianjin, China
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
| | - Yianzhu Liu
- Department of Cataract, Tianjin Eye Hospital, Tianjin, China
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin, China
| | - Hongyu Li
- Department of Ophthalmology, Chinese PLA General Hospital, Beijing, China
| | - Hui Song
- Department of Cataract, Tianjin Medical University Eye Hospital, Tianjin, China
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Savini G, Hoffer KJ, Kohnen T. IOL power formula classifications. J Cataract Refract Surg 2024; 50:105-107. [PMID: 38259130 DOI: 10.1097/j.jcrs.0000000000001378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Affiliation(s)
- Giacomo Savini
- From the IRCCS Bietti Foundation, Rome, Italy (Savini); St. Mary's Eye Center, Santa Monica, California (Hoffer); Stein Eye Institute, Los Angeles, California (Hoffer); Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany (Kohnen)
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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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Henderson BA, Aramberri J, Vann R, Abulafia A, Ainslie-Garcia M, Berdahl J, Ferko N, Gundersen KG, Goto S, Gupta P, Multack S, Persaud E, Raoof D, Savini G, Shammas HJ, Wang L, Wang WZ. The Current Burden and Future Solutions for Preoperative Cataract-Refractive Evaluation Diagnostic Devices: A Modified Delphi Study. Clin Ophthalmol 2023; 17:2109-2124. [PMID: 37521152 PMCID: PMC10378607 DOI: 10.2147/opth.s412847] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 07/11/2023] [Indexed: 08/01/2023] Open
Abstract
Purpose To obtain consensus on the key areas of burden associated with existing devices and to understand the requirements for a comprehensive next-generation diagnostic device to be able to solve current challenges and provide more accurate prediction of intraocular lens (IOL) power and presbyopia correction IOL success. Patients and Methods Thirteen expert refractive cataract surgeons including three steering committee (SC) members constituted the voting panel. Three rounds of voting included a Round 1 structured electronic questionnaire, Round 2 virtual face-to-face meeting, and Round 3 electronic questionnaire to obtain consensus on topics related to current limitations and future solutions for preoperative cataract-refractive diagnostic devices. Results Forty statements reached consensus including current limitations (n = 17) and potential solutions (n = 23) associated with preoperative diagnostic devices. Consistent with existing evidence, the panel reported unmet needs in measurement accuracy and validation, IOL power prediction, workflow, training, and surgical planning. A device that facilitates more accurate corneal measurement, effective IOL power prediction formulas for atypical eyes, simplified staff training, and improved decision-making process for surgeons regarding IOL selection is expected to help alleviate current burdens. Conclusion Using a modified Delphi process, consensus was achieved on key unmet needs of existing preoperative diagnostic devices and requirements for a comprehensive next-generation device to provide better objective and subjective outcomes for surgeons, technicians, and patients.
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Affiliation(s)
- Bonnie An Henderson
- Department of Ophthalmology, Tufts University School of Medicine, Boston, MA, USA
| | | | - Robin Vann
- Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA
| | - Adi Abulafia
- Department of Ophthalmology, Shaare Zedek Medical Center, Hadassah Faculty of Medicine, the Hebrew University, Jerusalem, Israel
| | | | | | | | | | - So Goto
- Herbert Wertheim School Optometry and Vision Science, University of California, Berkeley, CA, USA
- Department of Ophthalmology, National Hospital Organization, Tokyo Medical Center, Meguro-ku, Tokyo, Japan
| | - Preeya Gupta
- Triangle Eye Consultants, Raleigh, NC, USA
- Department of Ophthalmology, Tulane University, New Orleans, LA, USA
| | - Samuel Multack
- Laser and Cataract Institute, Frankfort, IL, USA
- Advocate South Suburban Hospital, Hazel Crest, IL, USA
- Advocate Trinity Hospital, Chicago, IL, USA
| | | | - Duna Raoof
- NVISION Eye Center, Newport Beach, CA, USA
| | | | - H John Shammas
- Department of Ophthalmology, University of Southern California, Los Angeles, CA, USA
| | - Li Wang
- Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, TX, USA
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IOL Power Calculations and Cataract Surgery in Eyes with Previous Small Incision Lenticule Extraction. J Clin Med 2022; 11:jcm11154418. [PMID: 35956035 PMCID: PMC9369542 DOI: 10.3390/jcm11154418] [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: 05/21/2022] [Revised: 06/30/2022] [Accepted: 07/27/2022] [Indexed: 02/01/2023] Open
Abstract
Small incision lenticule extraction (SMILE), with over 5 million procedures globally performed, will challenge ophthalmologists in the foreseeable future with accurate intraocular lens power calculations in an ageing population. After more than one decade since the introduction of SMILE, only one case report of cataract surgery with IOL implantation after SMILE is present in the peer-reviewed literature. Hence, the scope of the present multicenter study was to compare the IOL power calculation accuracy in post-SMILE eyes between ray tracing and a range of empirically optimized formulae available in the ASCRS post-keratorefractive surgery IOL power online calculator. In our study of 11 post-SMILE eyes undergoing cataract surgery, ray tracing showed the smallest mean absolute error (0.40 D) and yielded the largest percentage of eyes within ±0.50/±1.00 D (82/91%). The next best conventional formula was the Potvin–Hill formula with a mean absolute error of 0.66 D and an ±0.50/±1.00 D accuracy of 45 and 73%, respectively. Analyzing this first cohort of post-SMILE eyes undergoing cataract surgery and IOL implantation, ray tracing showed superior predictability in IOL power calculation over empirically optimized IOL power calculation formulae that were originally intended for use after Excimer-based keratorefractive procedures.
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Lanza M, Ruggiero A, Ha J, Simonelli F, Kane JX. Accuracy of Formulas for Intraocular Lens Power Calculation After Myopic Refractive Surgery. J Refract Surg 2022; 38:443-449. [PMID: 35858195 DOI: 10.3928/1081597x-20220602-01] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To assess the accuracy of the following intraocular lens (IOL) power formulas: Barrett True-K No History (BTKNH), Emmetropia Verifying Optical 2.0 Post Myopic LASIK/PRK (EVO 2.0), Haigis-L, American Society of Cataract and Refractive Surgery (ASCRS) average, and Shammas, designed for patients who have undergone previous myopic refractive surgery, independent of preexisting clinical history and corneal tomographic measurements. METHODS Data from 302 eyes of 302 patients who previously underwent myopic refractive surgery and had cataract surgery done by a single surgeon with only one IOL type inserted were included. The predicted refraction was calculated for each of the formulas and compared with the actual refractive outcome to give the prediction error. Subgroup analysis based on the axial length and mean keratometry was performed. RESULTS On the basis of mean absolute prediction error (MAE), the formulas were ranked as follows: Haigis-L (0.61 diopters [D]), ASCRS average (0.63 D), BTKNH (0.67 D), EVO 2.0 (0.68 D), and Shammas (0.69 D). The Haigis-L had a statistically significant lower MAE compared with all formulas (P < .05) except the ASCRS average. Hyperopic mean prediction errors were seen in all formulas for axial lengths of greater than 30 mm or mean keratometry values of 35.00 diopters or less. CONCLUSIONS The Haigis-L and the ASCRS average formulas provided the most accurate results in the overall population evaluated in this study. Moreover, according to data observed, it is important to be careful handling very long eyes and very flat corneas because hyperopic refractions could be more common. [J Refract Surg. 2022;38(7):443-449.].
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IOL power calculation with ray tracing based on anterior segment OCT and adjusted axial length after myopic excimer laser surgery. J Cataract Refract Surg 2022; 48:947-953. [PMID: 35121684 DOI: 10.1097/j.jcrs.0000000000000902] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 01/27/2022] [Indexed: 11/27/2022]
Abstract
PURPOSE To report the results of intraocular lens (IOL) power calculation by ray-tracing in eyes with previous myopic excimer laser surgery. SETTING G.B. Bietti Foundation I.R.C.C.S., Rome, Italy. DESIGN Retrospective interventional case series. METHODS A series of consecutive patients undergoing phacoemulsification and IOL implantation after myopic excimer laser was investigated. IOL power was calculated using ray-tracing software available on the anterior segment optical coherence tomographer MS-39 (CSO, Italy). Axial length (AL) was measured by optical biometry and 4 values were investigated: 1) that from the printout, 2) the modified Wang/Koch formula, 3) the polynomial equation for the Holladay 1 and 4) for the Holladay 2 formula. The mean prediction error (PE), median absolute error (MedAE), percentage of eyes with a PE within ±0.50 diopters (D) were reported. RESULTS We enrolled 39 eyes. Entering the original AL into ray-tracing led to a mean hyperopic PE (+0.56 ±0.54 D), whereas with the Wang/Koch formula a mean myopic PE (-0.41 ±0.53D) was obtained. The Holladay 1 and 2 polynomial equations lead to the lowest PEs (-0.10 ±0.49 and +0.08 ±0.49 D respectively), lowest MedAE (0.37 and 0.25 D) and highest percentages of eyes with a PE within ±0.50 D (71.79 and 76.92%). Calculations based on the Holladay 2 polynomial equation showed a statistically significant difference compared to other methods used (including Barrett-True K formula), with the only exception of the Holladay 1 polynomial equation. CONCLUSIONS IOL power can be accurately calculated by ray-tracing with adjusted AL according to the Holladay 2 polynomial equation.
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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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Fernández-Rosés J, Lamarca J, Piñero DP, Barraquer RI. Intraocular lens power calculation in virgin eyes: Accuracy of the Barrett Universal II formula and a Ray tracing software. Eur J Ophthalmol 2021; 32:2954-2960. [PMID: 34854773 DOI: 10.1177/11206721211065552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PURPOSE To compare the accuracy of Sirius ray tracing software with the Barrett Universal II formula for intraocular lens power prediction in virgin eyes. METHODS Retrospective case series including 86 eyes that have undergone uneventful cataract surgery with SN60WF implantation. The median absolute error, mean prediction error, variance, and the percentage of eyes within ± 0.25 D, ± 0.50 D, ± 0.75 D, and ± 1.00 D of the prediction error in refraction were calculated. The correlation of prediction error with different baseline parameters was investigated. RESULTS No differences were found between the median absolute error of the Barrett Universal II formula (0.226 D) and the ray tracing software with different intraocular lens centerings; apex (0.331 D), limbus (0.345 D), and pupil (0.342 D) (p = 0.084). The variance, from lowest to highest, was the Barrett Universal II (0.144 D2), ray tracing-limbus (0.285 D2), ray tracing-pupil (0.285 D2), and ray tracing-apex (0.287 D2) (p = 0.027). The Barrett Universal II formula showed a higher percentage of eyes within ± 0.25 D (56.98%), ± 0.50 D (82.56%), and ± 0.75 D (93.02%) compared to ray tracing software (p < 0.01). A significant correlation between the prediction error of the Barrett Universal II formula and corneal diameter (r = 0.322, p = 0.002) and pupil diameter (r = 0.230, p = 0.033) was found. Also, a positive correlation between the prediction error of Sirius ray tracing and axial length (p < 0.001) and pupil diameter (p = 0.01) was found. CONCLUSION There is a trend of the Barrett Universal II formula to be more accurate than Sirius ray tracing software for intraocular lens power calculation in virgin eyes. This should be confirmed in future prospective comparative studies.
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Affiliation(s)
- Joaquim Fernández-Rosés
- 16360Centro de Oftalmología Barraquer, Barcelona, Spain.,Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - José Lamarca
- 16360Centro de Oftalmología Barraquer, Barcelona, Spain.,Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain.,16760Universitat Internacional de Catalunya, Barcelona, Spain
| | - David P Piñero
- Department of Optics, Pharmacology and Anatomy, 16718University of Alicante, Alicante, Spain
| | - Rafael I Barraquer
- 16360Centro de Oftalmología Barraquer, Barcelona, Spain.,Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain.,16760Universitat Internacional de Catalunya, Barcelona, Spain
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de Rojas Silva MV, Tobío Ruibal A, Suanzes Hernández J. Corneal power measurements by ray tracing in eyes after small incision lenticule extraction for myopia with a combined Scheimpflug Camera-Placido disk topographer. Int Ophthalmol 2021; 42:921-931. [PMID: 34799784 DOI: 10.1007/s10792-021-02073-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 09/22/2021] [Accepted: 09/24/2021] [Indexed: 11/24/2022]
Abstract
PURPOSE To evaluate the accuracy of the measurements of corneal power obtained by ray tracing with a combined Scheimpflug camera-Placido disk corneal topographer (Sirius) in eyes after small incision lenticule extraction for myopia (SMILE). METHODS Retrospective cases study includes 50 eyes of 50 patients who underwent myopic SMILE. Mean value of simulated keratometry (Kpost), mean pupil power (MPP) (ray tracing, diameter of the entrance pupil range 3-6 mm), anterior and posterior corneal radius, and corneal thickness were obtained with Sirius topographer preoperatively and three months postoperatively, as well as cycloplegic refraction. True net power, equivalent keratometry readings, and Haigis equivalent power formula were calculated, and these measurements, MPP and Kpost, were compared with the corneal power calculated with the clinical history method (CHM). RESULTS Corneal power measurements obtained with all methods were significantly different from CHM (P < 0.001), except the value of MPP obtained at 5.5 mm (P = 0.927). A good direct correlation was found between CHM and all measurements. The distribution of differences as compared with the CHM showed that the lowest difference corresponded to the value of MMP at 5.5 mm (- 0.002 ± 0.6). The Bland-Altman plots for the MPP at 5.5 mm showed 95% limits of agreement between - 1.1787 D and 1.1741 D. CONCLUSIONS MPP obtained by ray tracing within a diameter of entrance pupil of 5.5 mm could predict corrected corneal power derived from the CHM in eyes following SMILE surgery.
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Affiliation(s)
- Mª Victoria de Rojas Silva
- Victoria de Rojas Instituto Oftalmológico, Policlínica Assistens, A Coruña, Spain. .,Department of Ophthalmology, Complexo Hospitalario Universitario, A Coruña, Spain.
| | - Adrián Tobío Ruibal
- Victoria de Rojas Instituto Oftalmológico, Policlínica Assistens, A Coruña, Spain
| | - Jorge Suanzes Hernández
- Research Support Unit, Complexo Hospitalario Universitario, A Coruña, Spain.,Institute of Biomedical Research (INIBIC), A Coruña, Spain
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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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Predictability of intraocular lens power calculation after small-incision lenticule extraction for myopia. J Cataract Refract Surg 2021; 47:304-310. [PMID: 32932366 DOI: 10.1097/j.jcrs.0000000000000405] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 08/03/2020] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate and compare the predictability of intraocular lens (IOL) power calculation after small-incision lenticule extraction (SMILE) for myopia and myopic astigmatism. SETTING Department of Ophthalmology, Philipps University of Marburg, Marburg, Germany. DESIGN Retrospective comparative case series. METHODS Preoperative evaluation included optical biometry using IOLMaster 500 and corneal tomography using Pentacam HR. The corneal tomography measurements were repeated at 3 months postoperatively. The change of spherical equivalent due to SMILE was calculated by the manifest refraction at corneal plane (SMILE-Dif). A theoretical model, involving the virtual implantation of the same IOL before and after SMILE, was used, and the IOL power calculations were performed using ray tracing (OKULIX, version 9.06) and third- (Hoffer Q, Holladay 1, and SRK/T) and fourth-generation (Haigis-L and Haigis) formulas. The difference between the IOL-induced refractive error at corneal plane before and after SMILE (IOL-Dif) was compared with SMILE-Dif. The prediction error (PE) was calculated as the difference between SMILE-Dif-IOL-Dif. RESULTS The study included 204 eyes that underwent SMILE. The PE with ray tracing was -0.06 ± 0.40 diopter (D); Haigis-L, -0.39 ± 0.62 D; Haigis, 0.70 ± 0.48 D; Hoffer Q, 0.84 ± 0.47 D; Holladay 1, 1.21 ± 0.51 D; and SRK/T, 1.46 ± 0.54 D. The PE with ray tracing was significantly smaller compared with that of all formulas (P ≤ .001). The PE variance with ray tracing was σ2 = 0.159, being significantly more homogenous compared with that of all formulas (P ≤ .011, F ≥ 6.549). Ray tracing resulted in an absolute PE of 0.5 D or lesser in 81.9% of the cases, followed by Haigis-L (53.4%), Haigis (35.3%), Hoffer Q (25.5%), Holladay 1 (6.4%), and SRK/T (2.9%) formulas. CONCLUSIONS Ray tracing was the most accurate approach for IOL power calculation after myopic SMILE.
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Zhang J, Shao J, Zheng L, Shen Y, Zhao X. Comparative clinical accuracy analysis of the newly developed ZZ IOL and four existing IOL formulas for post-corneal refractive surgery eyes. BMC Ophthalmol 2021; 21:231. [PMID: 34034681 PMCID: PMC8146991 DOI: 10.1186/s12886-021-01991-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Accepted: 05/10/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Intraocular lens (IOL) calculation using traditional formulas for post-corneal refractive surgery eyes can yield inaccurate results. This study aimed to compare the clinical accuracy of the newly developed Zhang & Zheng (ZZ) formula with previously reported IOL formulas. STUDY DESIGN Retrospective study. METHODS Post-corneal refractive surgery eyes were assessed for IOL power using the ZZ, Haigis-L, Shammas, Barrett True-K (no history), and ray tracing (C.S.O Sirius) IOL formulas, and their accuracy was compared. No pre-refractive surgery information was used in the calculations. RESULTS This study included 38 eyes in 26 patients. ZZ IOL yielded a lower arithmetic IOL prediction error (PE) compared with ray tracing (P = 0.04), whereas the other formulas had values like that of ZZ IOL (P > 0.05). The arithmetic IOL PE for the ZZ IOL formula was not significantly different from zero (P = 0.96). ZZ IOL yielded a lower absolute IOL PE compared with Shammas (P < 0.01), Haigis-L (P = 0.02), Barrett true K (P = 0.03), and ray tracing (P < 0.01). The variance of the mean arithmetic IOL PE for ZZ IOL was significantly smaller than those of Shammas (P < 0.01), Haigis-L (P = 0.03), Barrett True K (P = 0.02), and ray tracing (P < 0.01). The percentages of eyes within ± 0.5 D of the target refraction with the ZZ IOL, Shammas, Haigis-L, Barrett True-K, and ray-tracing formulas were 86.8 %, 45.5 %, 66.7 %, 73.7 %, and 50.0 %, respectively (P < 0.05 for Shammas and ray tracing vs. ZZ IOL). CONCLUSIONS The ZZ IOL formula might offer superior outcomes for IOL power calculation for post-corneal refractive surgery eyes without prior refractive data.
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Affiliation(s)
- Jun Zhang
- Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, China
| | - Jie Shao
- Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, China
| | - Li Zheng
- Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, China
| | - Ye Shen
- Ophthalmology, the First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
| | - Xia Zhao
- Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, China
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Langer J, Shajari M, Kreutzer T, Priglinger S, Mayer WJ, Mackert MJ. Predictability of Refractive Outcome of a Small-Aperture Intraocular Lens in Eyes With Irregular Corneal Astigmatism. J Refract Surg 2021; 37:312-317. [PMID: 34044696 DOI: 10.3928/1081597x-20210222-03] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare different new-generation biometric formulas and ray-tracing for small-aperture intraocular lens (IOL) (IC-8; Acufocus, Inc) implantation in patients undergoing cataract and refractive lens exchange surgery with highly irregular corneas. METHODS This monocenter study included 17 eyes of 17 patients with highly irregular corneas of different genesis. Biometric and topographic corneal data were assessed using the IOLMaster 700 (Carl Zeiss Meditec) and Pentacam (Oculus Optkigeräte GmbH). Prediction and absolute error were compared after 3 months based on manifest refraction. Furthermore, change of total corneal refractive power in different corneal pathologies was also evaluated. For IOL power calculation, three fourth-generation IOL formulas were compared (Haigis, SRK-T, and Barrett Universal II). The dataset was then checked against ray-tracing and analyzed to improve prediction error in these highly irregular corneas. RESULTS All patients showed an improvement in visual acuity postoperatively with a mean spherical equivalent of -1.22 ± 0.49 diopters (D). Overall comparison of the three formulas showed the Haigis formula to be superior in terms of the smallest deviation of predictive and absolute error. IOL calculations with ray-tracing were possible in all eyes, but showed inaccurate results with keratometric values of 48.00 D and greater. CONCLUSIONS The IC-8 IOL is well suited for patients with lens exchange in highly irregular corneas. The Haigis formula seemed to be the most accurate in the patient group. Ray-tracing confirmed the results of biometric formulas up to a keratometric value of 48.00 D and should be compared with standard biometric formulas to address corneal irregularities and to minimize refractive surprises after surgery. A comparison with ray-tracing in eyes with a keratometric value of greater than 48.00 D should not be considered due to the inaccurate results. [J Refract Surg. 2021;37(5):312-317.].
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Lwowski C, Van Keer K, Adas M, Schwarz L, Hinzelmann L, Pawlowicz K, Kohnen T. Ray-tracing Calculation Using Scheimpflug Tomography of Diffractive Extended Depth of Focus IOLs Following Myopic LASIK. J Refract Surg 2021; 37:231-239. [PMID: 34038658 DOI: 10.3928/1081597x-20210114-02] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate a ray-tracing formula for intraocular lens (IOL) calculation of diffractive extended depth of focus IOLs after myopic laser in situ keratomileusis (LASIK) compared to formulas from an established online calculator. METHODS This retrospective, consecutive case series included patients after cataract surgery with implantation of an extended depth of focus (EDOF) IOL (AT LARA, Carl Zeiss Meditec; Symfony, Johnson & Johnson) and a history of myopic LASIK. Preoperative assessments included biometry (IOLMaster; Carl Zeiss Meditec) and corneal tomography, including true net power (TNP) (Pentacam; Oculus Optikgeräte GmbH). To evaluate the measurements, the simulated keratometry values (SimK) were compared to the TNP. Regarding IOL calculation, the mean prediction error, mean and median absolute prediction error (MAE and MedAE), and number of eyes within ±0.50, ±1.00, and ±2.00 diopters (D) from the Haigis-L, Shammas, and Barrett True K No History formulas to the Potvin-Hill and Haigis with TNP (Pentacam) formulas were compared. RESULTS Thirty-six eyes matched the inclusion criteria with a mean spherical equivalent of -6.26 ± 3.25 diopters (D) preoperatively and -0.79 ± 0.75 D postoperatively. The mean difference from SimK and TNP was significantly different from zero (P < .001; -1.24 ± 0.81 D). The best performing formulas by MedAE were the Potvin-Hill and Barrett True K No History (0.39 ± 0.78 and 0.64 ± 1.00 D). The formula with the most eyes within ±0.50 D was the Potvin-Hill (64%), followed by the Barrett True K No History (44%). For MAE and percentage of eyes within ±0.50 D, the Potvin-Hill formula was significantly better than the Haigis-L, Shammas, and Haigis-TNP formulas (P < .05). CONCLUSIONS Calculation of IOLs in patients who had LASIK remains less predicable than calculations for virgin eyes. Using ray-tracing to calculate diffractive EDOF IOLs after myopic LASIK, the Potvin-Hill formula outperformed established formulas in terms of the percentage within target refraction and the MAE. [J Refract Surg. 2021;37(4):231-239.].
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Pantanelli SM, Lin CC, Al-Mohtaseb Z, Rose-Nussbaumer JR, Santhiago MR, Steigleman WA, Schallhorn JM. Intraocular Lens Power Calculation in Eyes with Previous Excimer Laser Surgery for Myopia: A Report by the American Academy of Ophthalmology. Ophthalmology 2021; 128:781-792. [PMID: 33500124 DOI: 10.1016/j.ophtha.2020.10.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 10/27/2020] [Accepted: 10/28/2020] [Indexed: 02/07/2023] Open
Abstract
PURPOSE To review the literature to evaluate the outcomes of intraocular lens (IOL) power calculation in eyes with a history of myopic LASIK or photorefractive keratectomy (PRK). METHODS Literature searches were conducted in the PubMed database in January 2020. Separate searches relevant to cataract surgery outcomes and corneal refractive surgery returned 1169 and 162 relevant citations, respectively, and the full text of 24 was reviewed. Eleven studies met the inclusion criteria for this assessment; all were assigned a level III rating of evidence by the panel methodologist. RESULTS When automated keratometry was used with a theoretical formula designed for eyes without previous laser vision correction, the mean prediction error (MPE) was universally positive (hyperopic), the mean absolute errors (MAEs) and median absolute errors (MedAEs) were relatively high (0.72-1.9 diopters [D] and 0.65-1.73 D, respectively), and a low (8%-40%) proportion of eyes were within 0.5 D of target spherical equivalent (SE). Formulas developed specifically for this population requiring both prerefractive surgery keratometry and manifest refraction (i.e., clinical history, corneal bypass, and Feiz-Mannis) produced a proportion of eyes within 0.5 D of target SE between 26% and 44%. Formulas requiring only preoperative keratometry or no history at all had lower MAEs (0.42-0.94 D) and MedAEs (0.30-0.81 D) and higher (30%-68%) proportions within 0.5 D of target SE. Strategies that averaged several methods yielded the lowest reported MedAEs (0.31-0.35 D) and highest (66%-68%) proportions within 0.5 D of target SE. Even after using the best-known methods, refractive outcomes were less accurate in eyes that had previous excimer laser surgery for myopia compared with those that did not have it. CONCLUSIONS Calculation methods requiring both prerefractive surgery keratometry and manifest refraction are no longer considered the gold standard. Refractive outcomes of cataract surgery in eyes that had previous excimer laser surgery are less accurate than in eyes that did not. Patients should be advised of this refractive limitation when considering cataract surgery in the setting of previous corneal refractive surgery. Conclusions are limited by the small sample sizes and retrospective nature of nearly all existing literature in this domain.
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Affiliation(s)
| | - Charles C Lin
- Byers Eye Institute, Stanford University, Palo Alto, California
| | | | - Jennifer R Rose-Nussbaumer
- Division of Research Kaiser Permanente Northern California and Francis I Proctor Foundation University of California, San Francisco, California
| | | | | | - Julie M Schallhorn
- Francis I. Proctor Foundation and Department of Ophthalmology, University of California, San Francisco, California
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Yu S, Lu CZ, Zhao Y, Song H. Evaluation of a New IOL Power Calculator in Cataract Patients with Normal and Long Axial Lengths. Semin Ophthalmol 2021; 35:370-376. [PMID: 33459110 DOI: 10.1080/08820538.2020.1871033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Purposes: To evaluate the accuracy of Ophtha Top and consistency between Ophtha Top and IOLMaster 500 in intraocular lens refractive power calculation among cataract patients with normal and long axial lengths. Methods: This study included cataract patients scheduled for phacoemulsification and IOL implantation surgery. The IOL power was calculated using Ophtha Top and IOLMaster 500 (integrated with SRK/T, Hoffer Q, Holladay 1 formula). The accuracy of IOL power calculation between Ophtha Top and IOLMaster 500 was compared. Bland-Altman plots were also used to assess agreement between Ophtha Top and IOLMaster 500. Results: Ninety-four patients (94 eyes) were included. The mean values of the arithmetic and absolute prediction errors of Ophtha Top were -0.22 ± 0.62 D and 0.52 ± 0.40 D for whole sample. Absolute refractive error showed no significant difference between Ophtha Top and IOLMaster 500 using 3 traditional formulas in eyes with normal and long axial lengths. In normal eyes, mean and medium absolute error of Ophtha Top was 0.49D and 0.48D, which were comparable to that of IOLMaster 500 (Hoffer Q:0.47D; 0.40D & Holladay 1: 0.48D; 0.37D). Similar trend was found in long eyes (Ophtha Top:0.58 D & IOLMaster using SRK/T:0.53D). Conclusions: Ophtha Top based on real ray-tracing method could provide predictable outcomes in all eyes, which was comparable to outcomes from IOLMaster 500 using SRK/T, Hoffer Q, Hollday 1 formula. Ophtha Top would be a promising alternative choice for IOL power calculation.
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Affiliation(s)
- Shasha Yu
- Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology, Tianjin Medical University, Nankai University Eye Hospital , Tianjin, China
| | - Cheng Zhe Lu
- Cataract Department, Tianjin Key Laboratory of Ophthalmology and Visual Science , Tianjin, China
| | - Yun Zhao
- Tianjin Eye Hospital, Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Institute, Clinical College of Ophthalmology, Tianjin Medical University, Nankai University Eye Hospital , Tianjin, China
| | - Hui Song
- Cataract Department, Clinical College of Ophthalmology, Tianjin Medical University , Tianjin, China
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Li QM, Wang F, Wu ZM, Liu Z, Zhan C, Chen BH, Sima J, Stieger K, Li SW. Trifocal diffractive intraocular lens implantation in patients after previous corneal refractive laser surgery for myopia. BMC Ophthalmol 2020; 20:293. [PMID: 32680481 PMCID: PMC7367255 DOI: 10.1186/s12886-020-01556-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 07/06/2020] [Indexed: 01/07/2023] Open
Abstract
Background With the difficulties in IOL power calculation and the potential side effects occurring postoperatively, multifocal IOL implantation after previous corneal refractive surgery are rarely reported especially for the trifocal IOL. Herein we report the clinical observation of trifocal IOL implantation in patients with previous myopia excimer laser correction. In this study, a multi-formula average method was performed for the IOLs power calculation to improve the accuracy. Visual and refractive outcomes were analyzed, and the subjective quality of patients’ life was evaluated by questionnaires survey. Methods This retrospective case series included patients with previous myopia excimer laser correction who underwent femtosecond laser assisted phacoemulsification and trifocal IOL (AT LISA tri 839 MP) implantation. Follow-up was done at 1-day, 1-month and 3-month to assess the visual outcomes. Outcome measures were uncorrected distance, intermediate and near visual acuity (UDVA, UIVA, UNVA), manifest refraction, defocus curve, and subjective quality of vision. Results Twenty-one Eyes from sixteen patients (14 eyes with previous laser in situ keratomileusis and 7 eyes with previous photorefractive keratectomy) were included. Mean postoperative spherical equivalent (SE) at 3-month was − 0.56 D ± 0.49 SD, wherein, 10 eyes (47.6%) were within ±0.50 D of the desired emmetropia and 19 eyes (90.5%) were within ±1.0 D. Mean monocular UDVA, UIVA and UNVA (logMAR) at last visit were 0.02 ± 0.07, 0.10 ± 0.10, and 0.15 ± 0.11 respectively. Three patients (19%) reported halos and glare in postoperative 3 months, two of them needed to use spectacles to improve the intermediate visual acuity. Fifteen patients (94%) reported a satisfaction score of ≥3.5 out of 4.0, without any difficulty in daily activity. Thirteen patients (81%) did not need spectacles at all distances, while the other 3 patients (19%) used spectacles for near-distance related visual activity. Mean composite score of the VF-14 questionnaire was 95.00 ± 7.29 out of 100. Conclusions Trifocal IOL implantation after myopia excimer laser correction could restore good distance, intermediate visual acuity and acceptable near visual acuity, and provide accurate refractive outcomes as well as high spectacles independence rate.
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Affiliation(s)
- Qiu-Mei Li
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China
| | - Feng Wang
- Department of Ophthalmology, Aier School of Ophthalmology, Central South University, Changsha, 410083, China.,Department of Ophthalmology, Justus-Liebig-University, 35385, Giessen, Germany
| | - Zhe-Ming Wu
- Guangzhou Aier Eye Hospital, Guangzhou, 510260, China
| | - Zhen Liu
- Chongqing Aier Eye Hospital, Chongqing, 400020, China
| | - Chuan Zhan
- Wanzhou Aier Eye Hospital, Chongqing, 404000, China
| | | | - Jing Sima
- Shenzhen Aier Eye Hospital, Shenzhen, 518005, China
| | - Knut Stieger
- Department of Ophthalmology, Justus-Liebig-University, 35385, Giessen, Germany.
| | - Shao-Wei Li
- Beijing Aier-Intech Eye Hospital, Beijing, 100021, China. .,Department of Ophthalmology, Aier School of Ophthalmology, Central South University, Changsha, 410083, China.
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Wang XZ, Cui R, Song XD, Yun B, Qian J, Ding N. Comparison of the accuracy of intraocular lens power calculation formulas for eyes after corneal refractive surgery. ANNALS OF TRANSLATIONAL MEDICINE 2020; 8:871. [PMID: 32793715 DOI: 10.21037/atm-20-4624] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background In cataract surgery, calculating intraocular lens (IOL) power in patients who have previously received corneal refractive surgery on the same eye presents a clinical challenge. This study aims to compare the accuracy of the Haigis-L, Barrett True-K, and Shammas-PL formulas in predicting the IOL power in eyes following corneal refractive surgery. Methods This study analyzed 32 eyes belonging to 28 patients who underwent cataract surgery and IOL implantation after previously undergoing myopic corneal refractive surgery. The IOL power was calculated using the Haigis-L, Barrett True-K, and Shammas-PL formulas, and the accuracy of the three formulas was compared. Results The Haigis-L, Barrett True-K, and Shammas-PL formulas had a mean arithmetic IOL prediction error of -0.65, -0.39, and -0.46, respectively. The mean numerical errors of the three formulas were significantly different from zero (P<0.001). The smallest median absolute refraction prediction error (median =0.40) belonged to the Barrett True-K formula, which was significantly smaller than that of the Haigis-L formula (median =0.57, P<0.05) but similar to that of the Shammas-PL formula (median =0.49, P>0.05). There was no significant difference in the percentage of eyes within either ±0.50 D or ±1.00 D of the predicted refraction error across the three formulas. Conclusions The Barrett True-K formula can predict IOL power in eyes that have previously undergone myopic corneal refractive surgery better than the Haigis-L formula.
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Affiliation(s)
- Xiao-Zhen Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Rui Cui
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Xu-Dong Song
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Bo Yun
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Jin Qian
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
| | - Ning Ding
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing, China
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Luft N, Siedlecki J, Schworm B, Kreutzer TC, Mayer WJ, Priglinger SG, Dirisamer M. Intraocular Lens Power Calculation after Small Incision Lenticule Extraction. Sci Rep 2020; 10:5982. [PMID: 32249851 PMCID: PMC7136233 DOI: 10.1038/s41598-020-63118-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Accepted: 03/14/2020] [Indexed: 11/09/2022] Open
Abstract
With more than 1.5 million Small Incision Lenticule Extraction (SMILE) procedures having already been performed worldwide in an ageing population, intraocular lens (IOL) power calculation in post-SMILE eyes will inevitably become a common challenge for ophthalmologists. Since no refractive outcomes of cataract surgery following SMILE have been published, there is a lack of empirical data for optimizing IOL power calculation. Using the ray tracing as the standard of reference - a purely physical method that obviates the need for any empirical optimization - we analyzed the agreement of various IOL power calculation formulas derived from the American Society of Cataract and Refractive Surgeons (ASCRS) post-keratorefractive surgery online calculator. In our study of 88 post-SMILE eyes, the Masket formula showed the smallest mean prediction error [-0.36 ± 0.32 diopters (D)] and median absolute error (0.33D) and yielded the largest percentage of eyes within ±0.50D (70%) in reference to ray tracing. Non-inferior refractive prediction errors and ±0.50D accuracies were achieved by the Barrett True K, Barrett True K No History and the Potvin-Hill formula. Use of these formulas in conjunction with ray tracing is recommended until sufficient data for empirical optimization of IOL power calculation after SMILE is available.
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Affiliation(s)
- Nikolaus Luft
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany. .,SMILE Eyes Clinic, Linz, Austria.
| | - Jakob Siedlecki
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany.,SMILE Eyes Clinic, Linz, Austria
| | - Benedikt Schworm
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany.,SMILE Eyes Clinic, Linz, Austria
| | - Thomas C Kreutzer
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany
| | - Wolfgang J Mayer
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany
| | - Siegfried G Priglinger
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany.,SMILE Eyes Clinic, Linz, Austria
| | - Martin Dirisamer
- University Eye Hospital, Ludwig-Maximilians-University, Munich, Germany.,SMILE Eyes Clinic, Linz, Austria
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Hirnschall N, Buehren T, Trost M, Findl O. Pilot evaluation of refractive prediction errors associated with a new method for ray-tracing–based intraocular lens power calculation. J Cataract Refract Surg 2019; 45:738-744. [DOI: 10.1016/j.jcrs.2019.01.023] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 12/29/2018] [Accepted: 01/16/2019] [Indexed: 10/27/2022]
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Abstract
PURPOSE OF REVIEW To provide a consolidated update regarding preoperative evaluation for cataract surgery. RECENT FINDINGS Visual acuity alone is a poor gauge of cataract disability. Modalities such as wave front aberrometry, lens densitometry, and light-scatter assessments can quantify optical aspects of cataract and may prove clinically useful in surgical evaluation. Advances in biometry are driving improvements in refractive outcomes, which in turn have increased patient expectations. Future advances in biometry technology may include three-dimensional imaging of the cornea and lens. Screening for ocular comorbidities has become increasingly important, particularly to guide lens selection. Risk stratification systems can help guide surgical decisions and may decrease intraoperative complication rate. A comprehensive medical history and physical is currently mandated for all Medicare patients undergoing cataract surgery but may be of limited utility for low-risk patients. SUMMARY Rising patient expectations and a growing number of surgical choices have expanded the cataract preoperative evaluation. A systematic and comprehensive examination which includes identifying any ocular comorbidity is essential for surgical planning and counseling on visual prognosis. New technologies will continue to inform, but not replace, sound clinical judgment.
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Intraocular lens power calculation using a Placido disk–Scheimpflug tomographer in eyes that had previous myopic corneal excimer laser surgery. J Cataract Refract Surg 2018; 44:935-941. [DOI: 10.1016/j.jcrs.2018.05.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 04/03/2018] [Accepted: 05/07/2018] [Indexed: 01/04/2023]
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Savini G, Hoffer KJ. Intraocular lens power calculation in eyes with previous corneal refractive surgery. EYE AND VISION 2018; 5:18. [PMID: 30038922 PMCID: PMC6053834 DOI: 10.1186/s40662-018-0110-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/25/2018] [Accepted: 06/22/2018] [Indexed: 01/14/2023]
Abstract
Background This review aims to explain the reasons why intraocular lens (IOL) power calculation is challenging in eyes with previous corneal refractive surgery and what solutions are currently available to obtain more accurate results. Review After IOL implantation in eyes with previous LASIK, PRK or RK, a refractive surprise can occur because i) the altered ratio between the anterior and posterior corneal surface makes the keratometric index invalid; ii) the corneal curvature radius is measured out of the optical zone; and iii) the effective lens position is erroneously predicted if such a prediction is based on the post-refractive surgery corneal curvature. Different methods are currently available to obtain the best refractive outcomes in these eyes, even when the perioperative data (i.e. preoperative corneal power and surgically induced refractive change) are not known. In this review, we describe the most accurate methods based on our clinical studies. Conclusions IOL power calculation after myopic corneal refractive surgery can be calculated with a variety of methods that lead to relatively accurate outcomes, with 60 to 70% of eyes showing a prediction error within 0.50 diopters.
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Affiliation(s)
| | - Kenneth J Hoffer
- 2Stein Eye Institute, University of California, Los Angeles, CA USA.,St. Mary's Eye Center, Santa Monica, CA USA
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Savini G, Schiano-Lomoriello D, Hoffer KJ. Repeatability of automatic measurements by a new anterior segment optical coherence tomographer combined with Placido topography and agreement with 2 Scheimpflug cameras. J Cataract Refract Surg 2018; 44:471-478. [DOI: 10.1016/j.jcrs.2018.02.015] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2017] [Revised: 02/03/2018] [Accepted: 02/05/2018] [Indexed: 11/17/2022]
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Abulafia A, Hill WE, Wang L, Reitblat O, Koch DD. Intraocular Lens Power Calculation in Eyes After Laser In Situ Keratomileusis or Photorefractive Keratectomy for Myopia. Asia Pac J Ophthalmol (Phila) 2017; 6:332-338. [PMID: 28780776 DOI: 10.22608/apo.2017187] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 07/25/2017] [Indexed: 11/08/2022] Open
Abstract
Intraocular power calculation is challenging for patients who have previously undergone corneal refractive surgery. The sources of prediction errors for these eyes are well known; however, the numerous formulas and methods available for calculating intraocular lens power in these cases are eloquent testimony to the absence of a definitive solution. This review discusses some of the available methods for improving the accuracy for predicting the refractive outcome for these patients. It focuses mainly on the methods available on the American Society of Cataract and Refractive Surgery (ASCRS) online calculator and provides some practical guidelines for cataract surgeons who encounter these challenging cases.
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Affiliation(s)
- Adi Abulafia
- Shaare Zedek Medical Centre, Jerusalem, Israel
- Hebrew University of Jerusalem, Jersusalem, Israel
| | | | - Li Wang
- Cullen Eye Institute, Baylor College of Medicine, Houston, Texas
| | - Olga Reitblat
- Shaare Zedek Medical Centre, Jerusalem, Israel
- Hebrew University of Jerusalem, Jersusalem, Israel
| | - Douglas D Koch
- Cullen Eye Institute, Baylor College of Medicine, Houston, Texas
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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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Koprowski R, Lanza M, Irregolare C. Corneal power evaluation after myopic corneal refractive surgery using artificial neural networks. Biomed Eng Online 2016; 15:121. [PMID: 27846894 PMCID: PMC5111354 DOI: 10.1186/s12938-016-0243-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Accepted: 11/09/2016] [Indexed: 11/30/2022] Open
Abstract
Background Efficacy and high availability of surgery techniques for refractive defect correction increase the number of patients who undergo to this type of surgery. Regardless of that, with increasing age, more and more patients must undergo cataract surgery. Accurate evaluation of corneal power is an extremely important element affecting the precision of intraocular lens (IOL) power calculation and errors in this procedure could affect quality of life of patients and satisfaction with the service provided. The available device able to measure corneal power have been tested to be not reliable after myopic refractive surgery. Methods Artificial neural networks with error backpropagation and one hidden layer were proposed for corneal power prediction. The article analysed the features acquired from the Pentacam HR tomograph, which was necessary to measure the corneal power. Additionally, several billion iterations of artificial neural networks were conducted for several hundred simulations of different network configurations and different features derived from the Pentacam HR. The analysis was performed on a PC with Intel® Xeon® X5680 3.33 GHz CPU in Matlab® Version 7.11.0.584 (R2010b) with Signal Processing Toolbox Version 7.1 (R2010b), Neural Network Toolbox 7.0 (R2010b) and Statistics Toolbox (R2010b). Results and conclusions A total corneal power prediction error was obtained for 172 patients (113 patients forming the training set and 59 patients in the test set) with an average age of 32 ± 9.4 years, including 67% of men. The error was at an average level of 0.16 ± 0.14 diopters and its maximum value did not exceed 0.75 dioptres. The Pentacam parameters (measurement results) providing the above result are tangential anterial/posterior. The corneal net power and equivalent k-reading power. The analysis time for a single patient (a single eye) did not exceed 0.1 s, whereas the time of network training was about 3 s for 1000 iterations (the number of neurons in the hidden layer was 400).
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Affiliation(s)
- Robert Koprowski
- Department of Biomedical Computer Systems, Faculty of Computer Science and Materials Science, Institute of Computer Science, University of Silesia, ul. Będzińska 39, 41-200, Sosnowiec, Poland.
| | - Michele Lanza
- Dipartimento Multidisciplinare di Scienze Mediche, Chirurgiche e Odontoiatriche, Seconda Università di Napoli, Naples, Italy.,Centro Grandi Apparecchiature, Seconda Università di Napoli, Naples, Italy
| | - Carlo Irregolare
- Centro Grandi Apparecchiature, Seconda Università di Napoli, Naples, Italy
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Accuracy of the Barrett True-K formula for intraocular lens power prediction after laser in situ keratomileusis or photorefractive keratectomy for myopia. J Cataract Refract Surg 2016; 42:363-9. [DOI: 10.1016/j.jcrs.2015.11.039] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 11/09/2015] [Accepted: 11/22/2015] [Indexed: 11/17/2022]
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Chen X, Yuan F, Wu L. Metaanalysis of intraocular lens power calculation after laser refractive surgery in myopic eyes. J Cataract Refract Surg 2016; 42:163-70. [DOI: 10.1016/j.jcrs.2015.12.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 08/06/2015] [Accepted: 08/11/2015] [Indexed: 10/22/2022]
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Savini G, Hoffer KJ, Barboni P. Influence of corneal asphericity on the refractive outcome of intraocular lens implantation in cataract surgery. J Cataract Refract Surg 2015; 41:785-9. [PMID: 25840302 DOI: 10.1016/j.jcrs.2014.07.035] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 07/16/2014] [Accepted: 07/17/2014] [Indexed: 10/23/2022]
Abstract
PURPOSE To evaluate the possible influence of anterior corneal surface asphericity on the refractive outcomes in eyes having intraocular lens (IOL) implantation after cataract surgery. SETTING Fondazione G.B. Bietti IRCCS, Rome, Italy. DESIGN Retrospective comparative case series. METHODS Intraocular lens power was calculated using the Haigis, Hoffer Q, Holladay 1, and SRK/T formulas. Asphericity (Q-value) was measured at 8.0 mm with a Placido-disk corneal topographer (Keratron), a rotating Scheimpflug camera (Pentacam), and a rotating Scheimpflug camera combined with Placido-disk corneal topography (Sirius). The relationship between the error in refraction prediction (ie, difference between expected refraction and refraction measured 1 month after surgery) and the Q-value was assessed by linear regression. RESULTS The same IOL model (Acrysof SA60AT) was implanted in 115 eyes of 115 consecutive patients. Regression analysis showed a statistically significant relationship between the error in refraction prediction and the Q-value with all formulas and all devices. In all cases, a more negative Q-value (prolate cornea) was associated with a myopic outcome, whereas a more positive Q-value (oblate cornea) was associated with a hyperopic outcome. The highest coefficient of determination was detected between the Hoffer Q formula and the Placido-disk corneal topographer (R(2) = 0.2630), for which the error in refraction prediction (y) was related to the Q-value (x) according to the formula y = -0.2641 + 1.4589 × x. CONCLUSION Corneal asphericity influences the refractive outcomes of IOL implantation and should be taken into consideration when using third-generation IOL power formulas. FINANCIAL DISCLOSURE Dr. Hoffer receives book royalties from Slack, Inc., Thorofare, New Jersey, and formula royalties from all manufacturers using the Hoffer Q formula. No other author has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Giacomo Savini
- From the Fondazione G.B. Bietti IRCCS (Savini), Rome, Studio Oculistico d'Azeglio (Barboni), Bologna, and the Scientific Institute San Raffaele (Barboni), Milan, Italy; the Stein Eye Institute (Hoffer), University of California, and St. Mary's Eye Center (Hoffer), Santa Monica, California, USA.
| | - Kenneth J Hoffer
- From the Fondazione G.B. Bietti IRCCS (Savini), Rome, Studio Oculistico d'Azeglio (Barboni), Bologna, and the Scientific Institute San Raffaele (Barboni), Milan, Italy; the Stein Eye Institute (Hoffer), University of California, and St. Mary's Eye Center (Hoffer), Santa Monica, California, USA
| | - Piero Barboni
- From the Fondazione G.B. Bietti IRCCS (Savini), Rome, Studio Oculistico d'Azeglio (Barboni), Bologna, and the Scientific Institute San Raffaele (Barboni), Milan, Italy; the Stein Eye Institute (Hoffer), University of California, and St. Mary's Eye Center (Hoffer), Santa Monica, California, USA
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Intraocular lens power calculation after myopic excimer laser surgery: Selecting the best method using available clinical data. J Cataract Refract Surg 2015; 41:1880-8. [DOI: 10.1016/j.jcrs.2015.10.026] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 01/05/2015] [Accepted: 01/13/2015] [Indexed: 11/24/2022]
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Intraocular lens power calculation following laser refractive surgery. EYE AND VISION 2015; 2:7. [PMID: 26605363 PMCID: PMC4655459 DOI: 10.1186/s40662-015-0017-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Accepted: 03/11/2015] [Indexed: 11/10/2022]
Abstract
Refractive outcomes following cataract surgery in patients that have previously undergone laser refractive surgery have traditionally been underwhelming. This is related to several key issues including the preoperative assessment (keratometry) and intraocular lens power calculations. Peer-reviewed literature is overwhelmed by the influx of methodology to manipulate the corneal or intraocular lens (IOL) powers following refractive surgery. This would suggest that the optimal derivative formula has yet been introduced. This review discusses the problems facing surgeons approaching IOL calculations in these post-refractive laser patients, the existing formulae and programs to address these concerns. Prior published outcomes will be reviewed.
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Gyldenkerne A, Ivarsen A, Hjortdal JØ. Assessing the corneal power change after refractive surgery using Scheimpflug imaging. Ophthalmic Physiol Opt 2015; 35:299-307. [PMID: 25703372 DOI: 10.1111/opo.12202] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 01/05/2015] [Indexed: 11/29/2022]
Abstract
PURPOSE To investigate whether the Pentacam HR could accurately predict the surgically induced refractive change in patients operated with small-incision lenticule extraction (SMILE) for myopia or femto-second laser in situ keratomileusis (FS-LASIK) for myopia or hyperopic astigmatism. METHODS Data from three groups consisting of (1) 410 myopic eyes of 410 patients operated with SMILE, (2) 111 myopic eyes of 111 patients operated with FS-LASIK, and (3) 40 eyes of 40 patients with hyperopic astigmatism operated with FS-LASIK were retrospectively analysed. The change in manifest refraction due to surgery was compared with the objectively measured change in corneal power by the Pentacam HR in three different ways: Sagittal Power (calculated as for placido topographers), True Net Power (calculated by a Gaussian optics formula), and Total Corneal Refractive Power (calculated by ray tracing). Multiple linear regression analysis was performed to investigate which parameters influenced the Pentacam HR's prediction of the change in subjective refraction due to surgery. RESULTS The Total Corneal Refractive Power Apex, Zone calculation in a diameter of 4.0 mm effectively predicted the surgically induced refractive change for all three patient groups. The spherical equivalent was predicted with an error of 0.08 ± 0.41 D for the SMILE eyes, 0.05 ± 0.61 D for the myopic eyes operated with FS-LASIK, and -0.15 ± 0.49 D for the hyperopic astigmatic eyes treated with FS-LASIK. Regression showed that preoperative refractive error had a significant impact on the prediction error of the Pentacam HR. CONCLUSIONS Ray tracing calculations based on Scheimpflug imaging accurately assessed the change in manifest refraction due to corneal laser surgery.
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Affiliation(s)
- Anders Gyldenkerne
- Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark
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