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      Intraocular Pressure, Axial Length, and Refractive Changes after Phacoemulsification and Trabeculectomy for Open-Angle Glaucoma

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          Abstract

          Purpose

          To compare changes in intraocular pressure (IOP), axial eye length (AEL), and refractive outcome in primary open-angle glaucoma patients undergoing cataract surgery and trabeculectomy in dependence of the sequence of surgeries.

          Materials and Methods

          We retrospectively analysed 48 eyes. The changes in refraction, intraocular pressure, and axial eye length were analysed after surgery. In group A (21 subjects), phacoemulsification was performed before trabeculectomy, and in group B (27 subjects), trabeculectomy was performed before phacoemulsification with a minimum time span between interventions of 6 months.

          Results

          The reduction in IOP and the decrease in AEL after trabeculectomy were significant after 6 and 12 months postsurgery ( p < 0.001 each). The decrease in AEL was 0.42 ± 0.11% at 6 months after surgery and 0.40 ± 0.13% after 12 months from surgery; this decrease in AEL was comparable between the groups. The refractive outcome was significantly different between the groups (group A: 0.35 ± 0.75 dpt, group B: −0.05 ± 0.36 dpt, p = 0.018); in group A, trabeculectomy caused a hyperopic shift of 0.34 ± 0.44 dpt ( p = 0.002) at 12 months postsurgery.

          Conclusion

          IOP reduction after trabeculectomy causes AEL shortening. The effect on refractive outcome depends on the sequence of surgeries. Better refractive outcome is achieved if phacoemulsification is performed after trabeculectomy.

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          Most cited references30

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          Calculation of intraocular lens power: a review.

          This review describes the principles and practices involved in the calculation of intraocular lens (IOL) power. The theories behind formulas for calculating IOL power are described, using regression and optical methods employing 'thin lens' and 'thick lens' models, as well as exact ray-tracing methods. Numerical examples are included to illustrate the points made. The paper emphasizes the importance of establishing an accurate estimation of corneal power as well as an accurate technique for the measurement of axial length and accurate methods of predicting postoperative anterior chamber depth (ACD). It is concluded that current improvements in diagnostic and surgical technology, combined with the latest generation IOL power formulas, make the calculation and selection of appropriate IOL power among the most effective tools in refractive surgery today.
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            Prediction of the effective postoperative (intraocular lens) anterior chamber depth.

            To investigate methods to predict the effective postoperative anterior chamber depth (ACD) based on a large patient sample. University Eye Clinic, Aarhus Kommunehospital, Aarhus, Denmark. Based on 6698 consecutive cataract operations with recorded postoperative refractive results, the postoperative effective ACD was calculated in each case and studied by multiple linear regression for covariance with a number of preoperatively defined variables including the axial length by ultrasonography, preoperative ACD, lens thickness, corneal radius by keratometry, subjective refraction, patient age, and corneal white-to-white diameter, the latter of which was available in a subgroup of 900 cases. The postoperative effective ACD was significantly correlated with 6 preoperative variables (in decreasing order): axial length, preoperative ACD, keratometry reading, lens thickness, refraction, and patient age (R = 0.49, P < .000001). Age showed the weakest correlation (P = .02) and could be omitted with no significant decrease in the total correlation coefficient. Using the 5 most significant variables, the ACD could be predicted according to a regression formula with an accuracy of 82.1% of the predictions within 0.5 mm. When this ACD algorithm was used in retrospect in the intraocular lens (IOL) power calculation, the refractive prediction error decreased by 10% from the error associated with a previously published 4-variable algorithm and decreased 28% from the error using no individual ACD method other than the average ACD (P < .00001). The postoperative ACD was significantly correlated with and hence predictable by a 5-variable regression method incorporating the preoperative axial length, ACD, keratometry reading, lens thickness, and refraction as the most significant variables. The statistical relationship can be used to create a new ACD prediction algorithm to incorporate in a modern "thick lens" IOL power calculation formula with significant improvement in the accuracy of the refractive predictions as a result.
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              Translating ocular biomechanics into clinical practice: current state and future prospects.

              Biomechanics is the study of the relationship between forces and function in living organisms and is thought to play a critical role in a significant number of ophthalmic disorders. This is not surprising, as the eye is a pressure vessel that requires a delicate balance of forces to maintain its homeostasis. Over the past few decades, basic science research in ophthalmology mostly confirmed that ocular biomechanics could explain in part the mechanisms involved in almost all major ophthalmic disorders such as optic nerve head neuropathies, angle closure, ametropia, presbyopia, cataract, corneal pathologies, retinal detachment and macular degeneration. Translational biomechanics in ophthalmology, however, is still in its infancy. It is believed that its use could make significant advances in diagnosis and treatment. Several translational biomechanics strategies are already emerging, such as corneal stiffening for the treatment of keratoconus, and more are likely to follow. This review aims to cultivate the idea that biomechanics plays a major role in ophthalmology and that the clinical translation, lead by collaborative teams of clinicians and biomedical engineers, will benefit our patients. Specifically, recent advances and future prospects in corneal, iris, trabecular meshwork, crystalline lens, scleral and lamina cribrosa biomechanics are discussed.
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                Author and article information

                Journal
                J Ophthalmol
                J Ophthalmol
                JOPH
                Journal of Ophthalmology
                Hindawi
                2090-004X
                2090-0058
                2017
                4 June 2017
                : 2017
                : 1203269
                Affiliations
                1Carol Davila University of Medicine and Pharmacy, Dionisie Lupu 37 Street, 020021 Bucharest, Romania
                2Emergency University Hospital, Department of Ophthalmology, Splaiul Independentei 169, 050098 Bucharest, Romania
                3Department of Clinical Pharmacology, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
                4Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
                5Singapore Eye Research Institute, The Academia, 20 College Road Discovery Tower Level 6, Singapore 169856
                6Lee Kong Chian School of Medicine, Nanyang Technological University, Novena Campus, 11 Mandalay Road, Singapore 308232
                7Ophthalmological Emergency Hospital, Alexandru Lahovari 1 Square, Bucharest, Romania
                Author notes
                *Raluca Claudia Iancu: ralucavasile2002@ 123456yahoo.com

                Academic Editor: Antonio Queiros

                Author information
                http://orcid.org/0000-0001-6933-8219
                http://orcid.org/0000-0002-7462-0929
                Article
                10.1155/2017/1203269
                5474260
                a4552ba2-0d1f-474f-a42b-5aad5f826982
                Copyright © 2017 Alina Popa-Cherecheanu et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 9 March 2017
                : 30 April 2017
                Categories
                Research Article

                Ophthalmology & Optometry
                Ophthalmology & Optometry

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