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Yokogawa T, Mori Y, Torii H, Goto S, Hasegawa Y, Kojima T, Kamiya K, Shiba T, Miyata K. Accuracy of intraocular lens power formulas in eyes with keratoconus: Multi-center study in Japan. Graefes Arch Clin Exp Ophthalmol 2024; 262:1839-1845. [PMID: 38217766 DOI: 10.1007/s00417-024-06371-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Revised: 12/30/2023] [Accepted: 01/04/2024] [Indexed: 01/15/2024] Open
Abstract
PURPOSE To assess the accuracy of intraocular lens (IOL) power formulas, namely, SRK/T, Haigis, Barrett Universal II, Barrett True-K for keratoconus, Kane formula, and Kane formula for keratoconus, for cataract with keratoconus in Japanese eyes. SETTING Five surgical sites in Japan. DESIGN A retrospective case series. METHODS Eyes with keratoconus undergoing cataract surgery were included. Postoperative refraction was compared with the prediction by the formulas. Visual acuity, manifest spherical equivalent, prediction error (PE), and mean absolute errors (MAEs) were determined 1 month postoperatively. The PE within 0.50 diopter (D), 1.00 D, and 2.00 D were compared between IOL formulas. Subgroup analysis based on the steepest keratometry (stage 1, ≤ 48 D; stage 2, > 48 D and ≤ 53 D; and stage 3, > 53 D) was performed. The relationship between PE and preoperative biometric data were assessed. RESULTS Fifty eyes were included. The MAE of the Barrett True-K for keratoconus, Kane keratoconus, and Kane formulas were significantly lower than that of Haigis. A statistically significant difference in the prediction accuracy within ± 0.50 D was found between Kane keratoconus and Haigis. The prediction accuracy of the Barrett True-K for keratoconus, SRK/T, and Kane within ± 1.00 D was statistically significant compared with that of Haigis. In stage 3, the Barrett True-K for keratoconus had a significantly lower MAE than SRK/T and Haigis. CONCLUSION Keratoconus-specific formulas were more accurate than existing formulas in Japanese eyes. The Barrett True-K formula for keratoconus had higher prediction accuracy in severe keratoconus.
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Affiliation(s)
- Tomohiro Yokogawa
- Miyata Eye Hospital, Kurahara 6-3, Miyakonojo, Miyazaki, 885-0051, Japan.
| | - Yosai Mori
- Miyata Eye Hospital, Kurahara 6-3, Miyakonojo, Miyazaki, 885-0051, Japan
| | - Hidemasa Torii
- Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582, Japan
| | - So Goto
- Department of Ophthalmology, Osaka University Graduate School of Medicine, Room E7, Yamadaoka 2-2, Suita, Osaka, 565-0871, Japan
- Department of Ophthalmology, Tokyo Medical Center, National Hospital Organization, 2-5-1 Higashigaoka, Meguro-Ku, Tokyo, 152-8902, Japan
- Herbert Wertheim School Optometry and Vision Science, University of California, Berkeley, CA, 94720-2020, USA
| | - Yumi Hasegawa
- Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, 2-1-1 Amakubo, Tsukuba, Ibaraki, 305-8076, Japan
| | - Takashi Kojima
- Nagoya Eye Clinic, 24-14 Namiyose, Atsuta-Ku, Nagoya, Aichi, 456-0003, Japan
| | - Kazutaka Kamiya
- Department of Ophthalmology, Kitasato University, 1-15-1 Kitasato, Minami-Ku, Sagamihara, Kanagawa, 252-0373, Japan
| | - Takuya Shiba
- Roppongi Shiba Eye Clinic, Minato-Ku, Tokyo, Japan
| | - Kazunori Miyata
- Miyata Eye Hospital, Kurahara 6-3, Miyakonojo, Miyazaki, 885-0051, Japan
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Coutinho CP, Schiano-Lomoriello D, Mazzotta C, Ferrise M, Hoffer KJ, Ribeiro FJ, Dias JM, Savini G. Differences Between Simulated Keratometry and Total Corneal Power in Eyes With Keratoconus and a Formula to Improve IOL Power Calculation Results. J Refract Surg 2024; 40:e253-e259. [PMID: 38593262 DOI: 10.3928/1081597x-20240311-06] [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: 04/11/2024]
Abstract
PURPOSE To compare simulated keratometry (SimK) and total corneal power (TCP) in keratoconic eyes, to determine whether the differences are systematic and predictable and to evaluate an adjusted TCP-based formula for intraocular lens (IOL) power calculation. METHODS In a consecutive series of keratoconic eyes, measurements of SimK, TCP, posterior keratometry, and anterior and posterior corneal asphericities (Q-values) were retrospectively collected. The difference between SimK and TCP was linearly correlated to the biometric parameters. In a separate sample of keratoconic eyes that had undergone cataract surgery, IOL power was calculated with the Barrett Universal II, Hoffer QST, Holladay 1, Kane, and SRK/T formulas using the SimK and an adjusted TCP power. The respective prediction errors were calculated. RESULTS A total of 382 keratoconic eyes (271 patients) were enrolled. An increasing overestimation of SimK by TCP was detected from stage I to III, with a significant correlation between the SimK and TCP difference and SimK in the whole sample (P < .0001, r2 = 0.1322). Approximately 7% of cases presented an underestimation of SimK by TCP. IOL power calculation with the adjusted TCP improved outcomes, achieving a maximum of 80% of eyes with a prediction error within ±0.50 diopters with the Hoffer QST, Holladay 1, and Kane formulas. CONCLUSIONS Overall, SimK overestimated TCP. Such a difference could not be predicted by any variable. The proposed TCP-adjustment formula (TCPadj = TCP + 0.56 diopters) in keratoconic eyes for IOL power calculation might be valuable for improving refractive outcomes. [J Refract Surg. 2024;40(4):e253-e259.].
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Camellin U, Ninotta I, Latino G, Alibrandi A, Aragona P, Roszkowska AM. Prediction of total corneal power in keratoconus using anterior surface data. Clin Exp Optom 2024; 107:274-280. [PMID: 37271161 DOI: 10.1080/08164622.2023.2215382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Revised: 05/09/2023] [Accepted: 05/12/2023] [Indexed: 06/06/2023] Open
Abstract
CLINICAL RELEVANCE Keratoconus results in an increase in anterior and posterior curvatures and a reduction in corneal thickness. Anterior corneal ectasia is partially compensated by remodelling the corneal epithelium. Therefore, there is an alteration in the relationship between corneal surfaces and variation in corneal power. The variation in corneal power is one of the sources that induces errors in IOL power calculation. BACKGROUND This study aimed to assess a method for predicting total corneal power in keratoconus using several anterior surface parameters at 3 mm and 4 mm. METHODS Tomographic data obtained using Pentacam (Oculus, Germany) were analysed from 280 eyes of 140 patients with keratoconus using anterior and posterior keratometry, anterior Q-value at 8 mm, central corneal thickness, Kmax location and value, and true net power at 4 mm (TNP). Calculated total corneal power (TCPc) at 3 mm was obtained using the Gauss formula. Predicted total corneal power at 3 mm (TCPp3) and 4 mm (TCPp4) was obtained from univariate (TCPp3u and TCPp4u) and multivariate linear regression formulae (TCPp3m and TCPp4m). SimK, anterior Q-value, vertical location, and Kmax value were used in the multivariate formulae. Mean absolute error (MAE) and median absolute error (MedAE) were also calculated. Absolute frequencies within dioptric ranges of all formulas divided for keratoconus grading were evaluated. RESULTS TCPc and TNP exhibited a good correlation (R2 = 0.58, p < 0.05) with a higher dispersion above 50 D of corneal power. Highly significant correlations were observed between TCPp3u and TCPc (R2 = 0.978, p < 0.05) and TCPp3m and TCPc (R2 = 0.989, p < 0.05). Lower but significant correlations were observed between TCPp4u and TNP (R2 = 0.692, p < 0.05) and between TCPp4m and TNP (R2 = 0.887, p < 0.05). The best results for TCP prediction at 3 and 4 mm were obtained with TCPp3m and TCPp4m as follows: MAE of TCPp3m was 0.24 ± 0.20 (SD) D with MedAE of 0.20 D, while MAE of TCPp4m was 0.96 ± 0.77 D with MedAE of 0.80 D. The 3 mm multivariate regression formula results in higher absolute frequencies of prediction errors in the total eyes within 0.5 D (93%) than the univariate formula (81%). At 4mm, the multivariate regression formula has a lower percentage within 0.5 D (32%) than the univariate formula (41%), but the percentage of the multivariate formula is higher within 1 D (63%) than the univariate formula (56%). CONCLUSION All formulas show a decrease in accuracy with increasing grades of keratoconus. Multivariate linear regression formulae using only anterior surface data can predict TCP with good approximation in eyes with keratoconus in cases where posterior surface parameters are unavailable. The vertical location of Kmax and the anterior asphericity could play a relevant role in the prediction of total corneal power in keratoconus.
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Affiliation(s)
- Umberto Camellin
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
| | - Ivan Ninotta
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
| | - Gianluigi Latino
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
| | | | - Pasquale Aragona
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
| | - Anna M Roszkowska
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
- Department of Ophthalmology, Andrzej Frycz Modrzewski Krakow University, Kraków, Poland
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D'Oria F, Bagaglia SA, Alio Del Barrio JL, Alessio G, Alio JL, Mazzotta C. Refractive surgical correction and treatment of keratoconus. Surv Ophthalmol 2024; 69:122-139. [PMID: 37774800 DOI: 10.1016/j.survophthal.2023.09.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 09/21/2023] [Accepted: 09/25/2023] [Indexed: 10/01/2023]
Abstract
Keratoconus is an ectatic corneal disorder that causes severe vision loss. Surgical options allow us to correct, partially or totally, the induced refractive error. Intracorneal ring segments (ICRS) implantation represents a minimally invasive surgical option that improves visual acuity, with a high success rate and a low overall complication rate. Corneal allogenic ICRS consists of ring segments derived from allogenic eye bank-processed donor corneas. Selective topography-guided transepithelial photorefractive or phototherapeutic keratectomy combined with CXL is another way in selected cases to improve spectacles corrected distance visual acuity. The microphotoablative remodeling of the central corneal profile is generally planned by optimizing the optical zones and minimizing tissue consumption. Phakic intraocular lens (PIOL) implant is considered in patients with stable disease and acceptable anatomical requirements. The two types of pIOLs, depending on their implantation inside the eye, are anterior chamber-pIOLs, which fixate to the anterior surface of the iris by using a polymethomethacrolate claw at the two haptics, and posterior chamber-pIOLs. In patients with both cataracts and keratoconus, the correct IOL power is difficult to obtain due to the irregular corneal shape and K values. Toric IOL is recommended, but carefully judging the topography and the possible need of subsequent keratoplasties.
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Affiliation(s)
- Francesco D'Oria
- Section of Ophthalmology, Department of Basic Medical Science, Neuroscience and Sense Organs, University of Bari, Bari, Italy.
| | - Simone A Bagaglia
- Departmental Ophthalmology Unit, Sant' Andrea Hospital, USL Toscana Sud-Est, Massa Marittima, Italy
| | - Jorge L Alio Del Barrio
- Vissum Miranza, Alicante, Spain; Division of Ophthalmology, Universidad Miguel Hernández, Alicante, Spain
| | - Giovanni Alessio
- Section of Ophthalmology, Department of Basic Medical Science, Neuroscience and Sense Organs, University of Bari, Bari, Italy
| | - Jorge L Alio
- Vissum Miranza, Alicante, Spain; Division of Ophthalmology, Universidad Miguel Hernández, Alicante, Spain.
| | - Cosimo Mazzotta
- Departmental Ophthalmology Unit, AUSL Toscana Sud Est, Campostaggia, Siena, Italy; Department of Medicine, Surgery and Neurosciences, Postgraduate Ophthalmology School, Siena University, Siena, Italy; Siena Crosslinking Center, Siena, Italy
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Singh C, Joshi VP. Cataract surgery in Keratoconus revisited - An update on preoperative and intraoperative considerations and postoperative outcomes. Semin Ophthalmol 2023; 38:57-64. [PMID: 35996343 DOI: 10.1080/08820538.2022.2112702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
PURPOSE This review aims to evaluate and simplify the recent literature on preoperative surgical planning, intraoperative considerations, postoperative surprises, and their management in patients with keratoconus undergoing cataract surgery. METHODS A review of the literature was done to analyze all the pertinent articles on Keratoconus and cataract surgery. RESULTS The surgical planning of cataracts in eyes with keratoconus needs a multifaceted approach. Preoperatively, techniques such as cross-linking or the use of intra-corneal rings help stabilize the progression. Unreliable biometric measurements are a significant problem in keratoconus patients, especially in an advanced stage of the disease. It is better to consider actual K readings if the K value is less than 55D but for a K value, more than 55D using standard K values will prevent postoperative refractive surprises. For calculation of K values, an elevation-based device like pentacam gives better repeatability in mild to moderate cases whereas for advanced keratoconus none of the keratometers is reliable. Recently, the Kane keratoconus formula performed better in all stages of disease whereas previous studies showed good results with SRK/T formula is a mild and moderate disease. Monofocal intraocular lenses are a better choice in these patients. Toric lenses can be used in mild and stable keratoconus. Intraoperatively, the use of a customized RGP lens can overcome the challenge of image distortion and loss of visual perspective. Despite taking necessary measures, postoperative refractive surprise can occur and can be managed with IOL exchange or Secondary IOLs. CONCLUSION There is a spectrum of challenges in managing cataracts in keratoconus which makes thorough preoperative planning important for good surgical outcomes. Despite the measures, there might be post-operative surprises and the patients need to be informed regarding the same.
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Affiliation(s)
- Charul Singh
- Academy of Eye Care Education, L V Prasad Eye Institute, Hyderabad, India.,The Cornea Institute, L V Prasad Eye Institute, Hyderabad, India
| | - Vineet P Joshi
- The Cornea Institute, L V Prasad Eye Institute, Hyderabad, India.,Centre for Innovation, L V Prasad Eye Institute, Hyderabad, India
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Yahalomi T, Achiron A, Hecht I, Arnon R, Levinger E, Pikkel J, Tuuminen R. Refractive Outcomes of Non-Toric and Toric Intraocular Lenses in Mild, Moderate and Advanced Keratoconus: A Systematic Review and Meta-Analysis. J Clin Med 2022; 11:jcm11092456. [PMID: 35566583 PMCID: PMC9101494 DOI: 10.3390/jcm11092456] [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: 02/15/2022] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 12/04/2022] Open
Abstract
Background: To perform a systematic review and meta-analysis of the refractive outcomes of non-toric and toric intraocular lenses (IOLs) in keratoconus (KC) using different IOL power calculation formulas. Methods: A systematic search was conducted to identify studies that report on refractive outcomes of different IOL power calculation formulas in KC patients undergoing cataract surgery. Inclusion criteria were primary posterior chamber non-toric and toric monofocal intraocular lens implantation, data on the degree of KC, explicit mention of the formula used for each stage of KC, and the number of eyes in each category. We calculated and compared the absolute and mean prediction errors, percentage of eyes within 0.5 D and 1 D from target, and the weighted absolute prediction errors of IOL formulas, all were given for KC degrees I–III. Results: The bibliographic search yielded 582 studies published between 1996 and 2020, 14 of which (in total 456 eyes) met the criteria: three studies on non-toric IOL (98 eyes), eight studies on toric IOLs (98 eyes) and three studies of unknown separation between non-toric and toric IOLs (260 eyes). The lowest absolute prediction error (APE) for mild, moderate, and advanced KC was seen with Kane’s IOL power formula with keratoconus adjustment. The APE for the top five IOL power formulas ranged 0.49–0.73 diopters (D) for mild (83–94%) of eyes within 1 D from the target), 1.08–1.21 D for moderate (51–57% within 1 D), and 1.44–2.86 D for advanced KC (12–48% within 1 D). Conclusions: Cataract surgery in eyes with mild-to-moderate KC generally achieves satisfactory postoperative refractive results. In patients with advanced KC, a minority of the eyes achieved spherical equivalent refraction within 1 D from the target. The Kane’s formula with keratoconus adjustment showed the best results in all KC stages.
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Affiliation(s)
- Tal Yahalomi
- Department of Ophthalmology, Samson Assuta Ashdod Hospital, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 7747629, Israel; (T.Y.); (R.A.); (J.P.)
| | - Asaf Achiron
- Department of Ophthalmology, Tel-Aviv Sourasky Medical Center, Tel-Aviv 6423906, Israel; (A.A.); (E.L.)
- Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel;
| | - Idan Hecht
- Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel;
- Department of Ophthalmology, Shamir Medical, Zerifin 7033001, Israel
| | - Roee Arnon
- Department of Ophthalmology, Samson Assuta Ashdod Hospital, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 7747629, Israel; (T.Y.); (R.A.); (J.P.)
| | - Eliya Levinger
- Department of Ophthalmology, Tel-Aviv Sourasky Medical Center, Tel-Aviv 6423906, Israel; (A.A.); (E.L.)
- Sackler Faculty of Medicine, Tel-Aviv University, Tel-Aviv 6997801, Israel;
| | - Joseph Pikkel
- Department of Ophthalmology, Samson Assuta Ashdod Hospital, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 7747629, Israel; (T.Y.); (R.A.); (J.P.)
| | - Raimo Tuuminen
- Department of Ophthalmology, Kymenlaakso Central Hospital, 48210 Kotka, Finland
- Helsinki Retina Research Group, Faculty of Medicine, University of Helsinki, 00014 Helsinki, Finland
- Correspondence: ; Tel.: +358-50-411-3870; Fax: +358-9-2411-227
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Camps VJ, Riad RRF, Caravaca-Arens E, Labib FE, Mateo V, Caballero MT, Piñero DP. Comparison of Four Intraocular Power Calculation Formulas in Keratoconus Eyes. Open Ophthalmol J 2021. [DOI: 10.2174/1874364102115010096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Introduction:
This study aimed to evaluate the differences in Intraocular Lens (IOL) power in keratoconus (KC) eyes between calculations obtained clinically with the most commonly used formulas in healthy eyes (SRK T, Holladay 1, Hoffer Q and Haigis) as well as to define predictive factors for such differences.
Methods:
This retrospective study comprised 43 keratoconus eyes of 22 patients with no previous ocular surgery. IOL powers were calculated with SRK T, Holladay 1, Hoffer Q, and Haigis formulas, considering the Effective Lens Position (ELP) of each formula and the desired refraction of 0 D (Rdes=0 D).
Results:
All differences between formulas were statistically significant and clinically relevant. Haigis formula always provided higher values compared to the rest of the formulas, with the highest differences observed when comparing Haigis with Hoffer (0.84 D) and Hoffer Q (1.17 D) formulas. The lowest difference was obtained for the comparison between SRK-T and Holladay 1 formulas (0.22 D). Differences of the Haigis formula compared to the rest were higher as the magnitude of the IOL power calculated decreased, becoming the patient more myopic. Increased differences between Haigis and Hoffer formulas were observed in eyes with deep anterior chambers, steeper anterior and posterior corneal surfaces, and high axial lengths.
Conclusion:
The most comparable results in IOL power in keratoconus are provided by the Holladay 1 and SRK T formulas, whereas the Haigis formula provides the most discrepant outcome. The consideration of the curvature of the second corneal surface in IOL power calculations in keratoconus may decrease the variability between calculation methods. However, other factors as anterior chamber depth or axial length are also relevant.
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David C, Kallel S, Trinh L, Goemaere I, Borderie V, Bouheraoua N. [Intracorneal ring segments in keratoconus management]. J Fr Ophtalmol 2021; 44:882-898. [PMID: 33895029 DOI: 10.1016/j.jfo.2020.10.021] [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: 04/19/2020] [Revised: 09/30/2020] [Accepted: 10/02/2020] [Indexed: 11/25/2022]
Abstract
Intracorneal ring segments (ICRS), used in the management of keratoconus since the 2000s, have enjoyed significant technological development. Various types of ICRS exist, whose arc length, thickness, and diameter can be chosen according to the desired effect on the spherical equivalent, keratometry and asphericity. Individualized implantation strategies, based on each patient's topographic and tomographic pattern, are constantly evolving. The surgical procedure is standardized, and complications remain very rare. Combined procedures (corneal collagen cross-linking and refractive photokeratectomy±topo-guided, phakic and pseudophakic intraocular lenses) are increasingly used and require a good knowledge of the effect of ICRS alone on the keratoconic cornea. The objective of this review is to summarize clinical practices used in the visual rehabilitation of keratoconic patients using the ICRS+- combined procedures.
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Affiliation(s)
- C David
- INSERM-DGOS CIC 1423, CHNO des Quinze-Vingts, IHU ForeSight, 28, rue de Charenton, 75012 Paris, France
| | - S Kallel
- INSERM-DGOS CIC 1423, CHNO des Quinze-Vingts, IHU ForeSight, 28, rue de Charenton, 75012 Paris, France
| | - L Trinh
- INSERM-DGOS CIC 1423, CHNO des Quinze-Vingts, IHU ForeSight, 28, rue de Charenton, 75012 Paris, France
| | - I Goemaere
- INSERM-DGOS CIC 1423, CHNO des Quinze-Vingts, IHU ForeSight, 28, rue de Charenton, 75012 Paris, France
| | - V Borderie
- INSERM-DGOS CIC 1423, CHNO des Quinze-Vingts, IHU ForeSight, 28, rue de Charenton, 75012 Paris, France; Inserm, CNRS, Sorbonne université, institut de la Vision, 17, rue Moreau, 75012 Paris, France
| | - N Bouheraoua
- INSERM-DGOS CIC 1423, CHNO des Quinze-Vingts, IHU ForeSight, 28, rue de Charenton, 75012 Paris, France; Inserm, CNRS, Sorbonne université, institut de la Vision, 17, rue Moreau, 75012 Paris, France.
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Kim J, Whang WJ, Kim HS. Analysis of total corneal astigmatism with a rotating Scheimpflug camera in keratoconus. BMC Ophthalmol 2020; 20:475. [PMID: 33272234 PMCID: PMC7713345 DOI: 10.1186/s12886-020-01747-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 11/25/2020] [Indexed: 12/01/2022] Open
Abstract
Background To analyze mean corneal powers and astigmatisms on anterior, posterior, and total cornea in patients with keratoconus as calculated according to various keratometric measurements using a Scheimpflug camera. Methods We examined the left eyes of 64 patients (41 males and 23 females; mean age 29.94 ± 6.63 years) with keratoconus. We measured simulated K (Sim-K), posterior K, true net power (TNP) and four types of total corneal refractive powers (TCRP). We then used the obtained values to analyze mean K, and corneal astigmatism. TCRP were measured at 2.0 ~ 5.0 mm. Results Mean corneal powers from Sim K, posterior K, and TNP were 49.12 ± 3.99, − 7.39 ± 0.79, and 47.78 ± 4.09 diopters, respectively. For TCRP centered on the pupil, mean K tended to decrease with measurement area (all p < 0.01). While, both mean K and astigmatism measured using TCRP centered on the apex decreased with measurement area (all p < 0.001). TCRP centered on the apex were greater than those centered on the pupil for mean K values calculated using TCRP (all p < 0.001). The proportion of WTR was greatest on the anterior and total cornea. As the measurement area moved to the periphery, the proportion of WTR increased. Conclusions Mean corneal powers and astigmatisms on total cornea with keratoconus change depending on calculation methods and measurement areas.
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Affiliation(s)
- Jinho Kim
- Department of Ophthalmology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea
| | - Woong-Joo Whang
- Department of Ophthalmology, Yeouido St. Mary's Hospital, College of Medicine, The Catholic University of Korea Korea, Seoul, South Korea.
| | - Hyun-Seung Kim
- Department of Ophthalmology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea
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Pirhadi S, Maghooli K, Jadidi K. An innovative approach for determining the customized refractive index of ectatic corneas in cataractous patients. Sci Rep 2020; 10:16681. [PMID: 33028843 PMCID: PMC7542460 DOI: 10.1038/s41598-020-73492-4] [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: 08/17/2019] [Accepted: 09/16/2020] [Indexed: 11/24/2022] Open
Abstract
The aim of this study is to determine the customized refractive index of ectatic corneas and also propose a method for determining the corneal and IOL power in these eyes. Seven eyes with moderate and severe corneal ectatic disorders, which had been under cataract surgery, were included. At least three months after cataract surgery, axial length, cornea, IOL thickness and the distance between IOL from cornea, and aberrometry were measured. All the measured points of the posterior and anterior parts of the cornea converted to points cloud and surface by using the MATLAB and Solidworks software. The implanted IOLs were designed by Zemax software. The ray tracing analysis was performed on the customized eye models, and the corneal refractive index was determined by minimizing the difference between the measured aberrations from the device and resulted aberrations from the simulation. Then, by the use of preoperative corneal images, corneal power was calculated by considering the anterior and posterior parts of the cornea and refractive index of 1.376 and the customized corneal refractive index in different regions and finally it was entered into the IOL power calculation formulas. The corneal power in the 4 mm region and the Barrett formula resulted the prediction error of six eyes within ± 1 diopter. It seems that using the total corneal power along with the Barrett formula can prevent postoperative hyperopic shift, especially in eyes with advanced ectatic disorders.
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Affiliation(s)
- Shiva Pirhadi
- Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Keivan Maghooli
- Department of Biomedical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran.
| | - Khosrow Jadidi
- Vision Health Research Center, Semnan University of Medical Sciences, Semnan, Iran
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Gonzalez-Lubcke E, Kahuam-Lopez N, Navas A, Ramirez-Miranda A, Graue-Hernandez EO. Comment on: Accuracy of Intraocular Lens Formulas in Eyes With Keratoconus. Am J Ophthalmol 2020; 218:354-355. [PMID: 32646542 DOI: 10.1016/j.ajo.2020.04.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Accepted: 04/14/2020] [Indexed: 10/23/2022]
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Abstract
The purpose was to review and document the methods used to calculate the power of the intraocular lens (IOL) to be implanted in cataract surgery in the specific scenario of eyes with keratoconus. This review included all scientific articles published in English that focused on the parameters and formulas used to calculate the power of the IOL to be implanted in eyes with keratoconus undergoing cataract surgery. There are few publications that show in detail how IOL power is calculated in these particular cases. If the keratometric value used was based on the standard refractive index (1.3375), it resulted in a postoperative refractive error with a tendency to hyperopia. The SRK/T formula yielded the best outcomes. The greater the severity of keratoconus the greater was the deviation of the postoperative refractive status from the target outcome.
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Savini G, Abbate R, Hoffer KJ, Mularoni A, Imburgia A, Avoni L, D’Eliseo D, Schiano-Lomoriello D. Intraocular lens power calculation in eyes with keratoconus. J Cataract Refract Surg 2019; 45:576-581. [DOI: 10.1016/j.jcrs.2018.11.029] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Revised: 11/16/2018] [Accepted: 11/22/2018] [Indexed: 11/25/2022]
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Comparison of Simulated Keratometry and Total Refractive Power for Keratoconus According to the Stage of Amsler-Krumeich Classification. Sci Rep 2018; 8:12436. [PMID: 30127375 PMCID: PMC6102270 DOI: 10.1038/s41598-018-31008-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 08/01/2018] [Indexed: 11/21/2022] Open
Abstract
This study was aimed to assess the simulated keratometry (Sim K) and the total corneal refractive power (TCRP) in eyes with keratoconus with respect to the Amsler-Krumeich classification. We enrolled 100 eyes of 100 keratoconic patients and 25 age-matched normal eyes. The Sim K and TCRP were measured with a rotating Scheimpflug system (Pentacam HR, Oculus). The differences between Sim K and TCRP in the keratoconus group were significantly larger than those in the control group (p < 0.001). The differences between Sim K and TCRP became larger in the progressive stages of the disease (p = 0.191 for stage 1, p = 0.008 for stage 2, p < 0.001 for stage 3, p < 0.001 for stage 4). We found a significant correlation of Sim K with the differences between Sim K and TCRP in keratoconic patients (r = 0.497, p < 0.001). The differences between Sim K and TCRP for keratoconus were significantly larger than those for normal eyes, and the differences between Sim K and TCRP tended to become larger in the progressive stages of the disease. It is suggested that the Sim K readings overestimate the TCRP, especially in advanced keratoconus, and that this discrepancy is a possible source of a hyperopic refractive error after cataract surgery.
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Piñero DP, Caballero MT, Nicolás-Albujer JM, de Fez D, Camps VJ. A New Approach for the Calculation of Total Corneal Astigmatism Considering the Magnitude and Orientation of Posterior Corneal Astigmatism and Thickness. Cornea 2018. [PMID: 29538100 DOI: 10.1097/ico.0000000000001577] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate a new method of calculation of total corneal astigmatism based on Gaussian optics and the power design of a spherocylindrical lens (C) in the healthy eye and to compare it with keratometric (K) and power vector (PV) methods. METHODS A total of 92 healthy eyes of 92 patients (age, 17-65 years) were enrolled. Corneal astigmatism was calculated in all cases using K, PV, and our new approach C that considers the contribution of corneal thickness. An evaluation of the interchangeability of our new approach with the other 2 methods was performed using Bland-Altman analysis. RESULTS Statistically significant differences between methods were found in the magnitude of astigmatism (P < 0.001), with the highest values provided by K. These differences in the magnitude of astigmatism were clinically relevant when K and C were compared [limits of agreement (LoA), -0.40 to 0.62 D), but not for the comparison between PV and C (LoA, -0.03 to 0.01 D). Differences in the axis of astigmatism between methods did not reach statistical significance (P = 0.408). However, they were clinically relevant when comparing K and C (LoA, -5.48 to 15.68 degrees) but not for the comparison between PV and C (LoA, -1.68 to 1.42 degrees). CONCLUSIONS The use of our new approach for the calculation of total corneal astigmatism provides astigmatic results comparable to the PV method, which suggests that the effect of pachymetry on total corneal astigmatism is minimal in healthy eyes.
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Affiliation(s)
- David P Piñero
- Group of Optics and Visual Perception, Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain.,Department of Ophthalmology (OFTALMAR), Vithas Medimar International Hospital, Alicante, Spain
| | - María T Caballero
- Group of Optics and Visual Perception, Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - Juan M Nicolás-Albujer
- Group of Optics and Visual Perception, Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - Dolores de Fez
- Group of Optics and Visual Perception, Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - Vicent J Camps
- Group of Optics and Visual Perception, Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
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Choi Y, Eom Y, Song JS, Kim HM. Comparison of Anterior, Posterior, and Total Corneal Astigmatism Measured Using a Single Scheimpflug Camera in Healthy and Keratoconus Eyes. KOREAN JOURNAL OF OPHTHALMOLOGY 2018; 32:163-171. [PMID: 29770640 PMCID: PMC5990638 DOI: 10.3341/kjo.2017.0075] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 10/15/2017] [Indexed: 11/23/2022] Open
Abstract
Purpose To compare the effect of posterior corneal astigmatism on the estimation of total corneal astigmatism using anterior corneal measurements (simulated keratometry [K]) between eyes with keratoconus and healthy eyes. Methods Thirty-three eyes of 33 patients with keratoconus of grade I or II and 33 eyes of 33 age- and sex-matched healthy control subjects were enrolled. Anterior, posterior, and total corneal cylinder powers and flat meridians measured by a single Scheimpflug camera were analyzed. The difference in corneal astigmatism between the simulated K and total cornea was evaluated. Results The mean anterior, posterior, and total corneal cylinder powers of the keratoconus group (4.37 ± 1.73, 0.95 ± 0.39, and 4.36 ± 1.74 cylinder diopters [CD], respectively) were significantly greater than those of the control group (1.10 ± 0.68, 0.39 ± 0.18, and 0.97 ± 0.63 CD, respectively). The cylinder power difference between the simulated K and total cornea was positively correlated with the posterior corneal cylinder power and negatively correlated with the absolute flat meridian difference between the simulated K and total cornea in both groups. The mean magnitude of the vector difference between the astigmatism of the simulated K and total cornea of the keratoconus group (0.67 ± 0.67 CD) was significantly larger than that of the control group (0.28 ± 0.12 CD). Conclusions Eyes with keratoconus had greater estimation errors of total corneal astigmatism based on anterior corneal measurement than did healthy eyes. Posterior corneal surface measurement should be more emphasized to determine the total corneal astigmatism in eyes with keratoconus.
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Affiliation(s)
- Young Choi
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea
| | - Youngsub Eom
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea.
| | - Jong Suk Song
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea
| | - Hyo Myung Kim
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Korea
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Algorithm for Correcting the Keratometric Error in the Estimation of the Corneal Power in Keratoconus Eyes after Accelerated Corneal Collagen Crosslinking. J Ophthalmol 2017; 2017:8529489. [PMID: 29201459 PMCID: PMC5672131 DOI: 10.1155/2017/8529489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2017] [Accepted: 09/19/2017] [Indexed: 11/30/2022] Open
Abstract
Purpose To analyze the errors associated to corneal power calculation using the keratometric approach in keratoconus eyes after accelerated corneal collagen crosslinking (CXL) surgery and to obtain a model for the estimation of an adjusted corneal refractive index (nkadj) minimizing such errors. Methods Potential differences (ΔPc) among keratometric (Pk) and Gaussian corneal power (PcGauss) were simulated. Three algorithms based on the use of nkadj for the estimation of an adjusted keratometric corneal power (Pkadj) were developed. The agreement between Pk(1.3375) (keratometric power using the keratometric index of 1.3375), PcGauss, and Pkadj was evaluated. The validity of the algorithm developed was investigated in 21 keratoconus eyes undergoing accelerated CXL. Results Pk(1.3375) overestimated corneal power between 0.3 and 3.2 D in theoretical simulations and between 0.8 and 2.9 D in the clinical study (ΔPc). Three linear equations were defined for nkadj to be used for different ranges of r1c. In the clinical study, differences between Pkadj and PcGauss did not exceed ±0.8 D nk = 1.3375. No statistically significant differences were found between Pkadj and PcGauss (p > 0.05) and Pk(1.3375) and Pkadj (p < 0.001). Conclusions The use of the keratometric approach in keratoconus eyes after accelerated CXL can lead to significant clinical errors. These errors can be minimized with an adjusted keratometric approach.
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Camps VJ, Piñero DP, Caravaca E, De Fez D. Preliminary validation of an optimized algorithm for intraocular lens power calculation in keratoconus. Indian J Ophthalmol 2017; 65:690-699. [PMID: 28820154 PMCID: PMC5598179 DOI: 10.4103/ijo.ijo_274_16] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Purpose: This study aimed to evaluate the theoretical influence on intraocular lens power (PIOL) calculation of the use of keratometric approach for corneal power (Pc) calculation in keratoconus and to develop and validate an algorithm preliminarily to minimize this influence. Methods: Pc was calculated theoretically with the classical keratometric approach, the Gaussian equation, and the keratometric approach using a variable keratometric index (nkadj) dependent on r1c(Pkadj). Differences in PIOL calculations (ΔPIOL) using keratometric and Gaussian Pc values were evaluated. Preliminary clinical validation of a PIOL algorithm using Pkadj was performed in 13 keratoconus eyes. Results: PIOL underestimation was present if Pc was overestimated, and vice versa. Theoretical PIOL overestimation up to −5.6 D and −6.2 D using Le Grand and Gullstrand eye models was found for a keratometric index of 1.3375. If nkadj was used, maximal Δ PIOL was ±1.1 D, with most of the values ≤±0.6 D. Clinically, PIOL under- and over-estimations ranged from −1.1 to − 0.4 D. No statistically significant differences were found between PIOL obtained with Pkadj and Gaussian equation (P > 0.05). Conclusion: The use of the keratometric Pc for PIOL calculations in keratoconus can lead to significant errors that may be minimized using a Pkadj approach.
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Affiliation(s)
- Vicente J Camps
- Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - David P Piñero
- Department of Optics, Pharmacology and Anatomy, University of Alicante; Department of Ophthalmology (Oftalmar), Vithas Medimar International Hospital, Alicante, Spain
| | - Esteban Caravaca
- Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
| | - Dolores De Fez
- Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
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Labiris G, Sideroudi H, Angelonias D, Georgantzoglou K, Kozobolis VP. Impact of corneal cross-linking combined with photorefractive keratectomy on blurring strength. Clin Ophthalmol 2016; 10:571-6. [PMID: 27099464 PMCID: PMC4824379 DOI: 10.2147/opth.s100770] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Purpose The aim of this study was to evaluate the impact of corneal cross-linking combined with photorefractive keratectomy (PRK) on blurring strength. Methods A total of 63 patients with keratoconus were recruited for this study, and two study groups were formed according to the therapeutic intervention: corneal collagen cross-linking (CxL) group (33 patients) received corneal cross-linking according to the Dresden protocol, while the rest additionally received topography-guided photorefractive keratectomy (tCxL). The impact of surgical procedure on blurring strength was assessed by power vector analysis. Potential association between blurring strength and vision-specific quality of life was assessed using the National Eye Institute Visual Function Questionnaire (NEI-VFQ) 25 instrument. Results Blurring strength presented excellent correlation with NEI-VFQ scores both preoperatively and postoperatively (all P<0.01). Both groups demonstrated nonsignificant changes in best-corrected visual acuity; however, only the tCxL group had significant reduction in blurring strength (13.48+10.86 [preoperative], 4.26+7.99 [postoperative], P=0.042). Conclusion Only the combined treatment (tCxL) resulted in significant reduction in blurring strength. Moreover, the excellent correlation of blurring strength with NEI-VFQ scores indicates its reliability as an index of self-reported quality of life in keratoconus, since it seems to address the nonsignificant changes in best-corrected visual acuity following CxL treatments that are conceived as subjective improvement by the patient.
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Affiliation(s)
- Georgios Labiris
- Department of Ophthalmology, University Hospital of Alexandroupolis, Alexandroupolis, Greece; Eye Institute of Thrace, Alexandroupolis, Greece
| | | | | | | | - Vassilios P Kozobolis
- Department of Ophthalmology, University Hospital of Alexandroupolis, Alexandroupolis, Greece; Eye Institute of Thrace, Alexandroupolis, Greece
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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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Eom Y, Kang SY, Kim HM, Song JS. The effect of posterior corneal flat meridian and astigmatism amount on the total corneal astigmatism estimated from anterior corneal measurements. Graefes Arch Clin Exp Ophthalmol 2014; 252:1769-77. [PMID: 25038911 DOI: 10.1007/s00417-014-2737-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 06/16/2014] [Accepted: 06/24/2014] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND To evaluate the effects of posterior corneal astigmatism and the absolute flat meridian difference between anterior and posterior corneal surfaces (AMDAnt-Post) on the estimation of total corneal astigmatism using anterior corneal measurements (simulated keratometry [K]). METHODS Ninety-nine eyes of 99 healthy participants were enrolled. Anterior, posterior, and total mean corneal power, cylinder power, flat meridian, and vector components J0, and J45 measured by a dual Scheimpflug camera were analyzed. The correlation between the posterior corneal cylinder power, AMDAnt-Post, and the difference in the cylinder power between simulated K and total cornea (cylinder power differenceSimK-Tot) were evaluated. RESULTS The cylinder power differenceSimK-Tot was positively correlated with the posterior corneal cylinder power (rho = 0.704 and P < 0.001) and negatively correlated with AMDAnt-Post (rho = -0.717 and P < 0.001). In the multivariate linear regression analysis, anterior corneal J0 was strongly associated with the posterior corneal cylinder power and the AMDAnt-Post. When corneal J0 had a positive value, the cylinder power of simulated K tended to be larger than the total corneal cylinder power. In comparison, the opposite trend was presented in eyes with negative anterior corneal J0. When anterior corneal J0 was larger than 1.0 or smaller than -0.9, the errors from estimating the total corneal cylinder power using anterior corneal measurements tended to be larger than 0.25 D. CONCLUSION Posterior corneal astigmatism should be considered for more accurate corneal astigmatism predictions, especially in eyes with anterior corneal astigmatism greater than 2.0 D of with-the-rule astigmatism or greater than 1.8 D of against-the-rule astigmatism.
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Affiliation(s)
- Youngsub Eom
- Department of Ophthalmology, Korea University College of Medicine, Seoul, South Korea
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