Intraocular Lens

The first clinical application of intraocular lens (IOL) goes back to 1949 when Dr. Harold Ridley successfully implanted a PMMA IOL into an eye on 29 November 1949. This innovation is a big step forward for cataract surgery. With development of the IOL material and biocompatibility, more and more IOL types have been used in clinical ophthalmology. This book is the fruit of worldwide cooperation between clinical teams. In this book we discuss the IOL materials and design, aberration and astigmatism correction with IOL, entopic phenomenon of IOL, myopia and phakic IOL, and secondary IOL techniques. We believe that this content provides the readers with a comprehensive knowledge of the latest developments of IOL

Risk factors of regression and undercorrection in photorefractive keratectomy: A case-control study

�AIM: To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK) in myopia or myopic astigmatism. �METHODS: A case-control study was designed in which eyes with an indication for re-treatment (RT) were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity (UDVA) of 20/30 or worse and a stable refraction for more than 3mo. Additional considerations included optical quality symptoms and significant higher order aberrations (HOAs). Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving (TS) ablation profile of Technolas 217z100 excimer laser (Bausch & Lomb, Rochester, NY, USA). Mitomycin C had been used in all of the primary procedures. �RESULTS: We had 70 case eyes and 158 control eyes, and they were comparable in terms of age, sex and follow-up time (P values:0.58, 1.00 and 0.89, respectively). Pre-operative spherical equivalent of more than -5.00 diopter (D), intended optical zone (OZ) diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with RT indications (all P values -5.00 D), smaller OZ (<6.00 mm) and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression. © 2015 International Journal of Ophthalmology (c/o Editorial Office). All Rights Reserved

Vision Correction and Eye Surgery

This book focuses on the current approaches in the medical and surgical treatment of the most diffuse and important ocular diseases. It reports the latest developments in surgery (anterior segment surgery, posterior pole surgery, etc.) for various types of ocular disease, including glaucoma, corneal diseases, and vitreoretinal disease. the latest developments in the surgical field of ocular disease from the anterior segment to the posterior pole going through the main ocular disease (cataract surgery in normal and/or complicated conditions, glaucoma, corneal diseases, and vitreoretinal disease), with the latest developments in the treatment of ocular disease that enable improved surgical outcomes and fewer complications

Safety and efficacy of intraocular lenses in cataract and refractive surgery

There is a global rise in the number of people with high myopia. These patients rely heavily on glasses or contact lenses, and rarely qualify for laser refractive surgery. Use of an implant lens can be beneficial in these situations: placed between the cornea and patients’ lens they offer excellent refractive correction and visual acuity. Our research has shown that as a foreign body, they can be associated with increased ageing of the cornea and patients’ lens, with safety varying amongst lens types. Lenses that use the irido-corneal angle for support have short-term safety concerns for the cornea, whereas iris-fixated lenses can be used safely after modification of the implantation criteria and follow-up schedule. The second part of the thesis focuses on middle-aged patients: their lens loses accommodative power as they age, resulting in the need for reading glasses. This thesis shows that spectacle independence can be obtained in these patients by implanting a multifocal lens during cataract surgery. Implantation of trifocal lenses or a combination of two types of bifocal lenses both result in spectacle independence. However, in some cases this may be associated with side-effects like photopsia and loss of contrast

Visionary Ophthalmics: Confluence of Computer Vision and Deep Learning for Ophthalmology

Ophthalmology is a medical field ripe with opportunities for meaningful application of computer vision algorithms. The field utilizes data from multiple disparate imaging techniques, ranging from conventional cameras to tomography, comprising a diverse set of computer vision challenges. Computer vision has a rich history of techniques that can adequately meet many of these challenges. However, the field has undergone something of a revolution in recent times as deep learning techniques have sprung into the forefront following advances in GPU hardware. This development raises important questions regarding how to best leverage insights from both modern deep learning approaches and more classical computer vision approaches for a given problem. In this dissertation, we tackle challenging computer vision problems in ophthalmology using methods all across this spectrum. Perhaps our most significant work is a highly successful iris registration algorithm for use in laser eye surgery. This algorithm relies on matching features extracted from the structure tensor and a Gabor wavelet – a classically driven approach that does not utilize modern machine learning. However, drawing on insight from the deep learning revolution, we demonstrate successful application of backpropagation to optimize the registration significantly faster than the alternative of relying on finite differences. Towards the other end of the spectrum, we also present a novel framework for improving RANSAC segmentation algorithms by utilizing a convolutional neural network (CNN) trained on a RANSAC-based loss function. Finally, we apply state-of-the-art deep learning methods to solve the problem of pathological fluid detection in optical coherence tomography images of the human retina, using a novel retina-specific data augmentation technique to greatly expand the data set. Altogether, our work demonstrates benefits of applying a holistic view of computer vision, which leverages deep learning and associated insights without neglecting techniques and insights from the previous era

Prospective comparison of two excimer laser platforms in treatment of high astigmatism with laser in situ keratomileusis [Prospektivna usporedba dvije laserske platforme u tretiranju visokog astigmatizma laser in situ keratomijeluzom]

PURPOSE: Comparison of Wavelight Allegretto Eye-Q and Schwind Amaris 750S excimer laser groups after performed LASIK procedure regarding functional parameters – uncorrected (UDVA) and corrected distant visual acuity (CDVA), residual refractive error, astigmatism outcomes by means of vector analysis and high order aberrations in patients with high astigmatism (more than 2 diopters (D)). ----- METHODS: 135 patients with myopic astigmatism (246 eyes) and 102 patients with mixed astigmatism (172 eyes) underwent LASIK correction (some of the patients had only one eye operated – the eye that met the criteria for the study, while the other eye had no diopter at all) and were divided in 4 groups: 1 – myopic astigmatism corrected with Allegretto, 2 – myopic astigmatism corrected with Amaris, 3 – mixed astigmatism corrected with Allegretto and 4 – mixed astigmatism corrected with Amaris. Data were analysed to determine significance of change in spherical correction, astigmatism, UDVA, CDVA, high order aberrations, and also vector analysis by Thibos (J0 and J45) and Alpins method was performed. ----- RESULTS: Visual acuity improvement for group 1 was statistically significant (p=0.017); for group 2, 3 and 4 was not statistically significant (p=0.06, p=0.406, p=0.115). None of the eyes lost any lines of CDVA. Regarding refractive results, for all groups there was almost complete elimination of spherical and cylindrical refractive error. High-order aberrations results for groups 1 and 2 showed no significant change between preoperative and postoperative high-order aberrations, while in groups 3 and 4 spherical aberrations changed. Vector analysis by Thibos showed statistically significant difference between J0 preop and J0 postop for both platforms (p<0.001). There was statistically significant difference for J45 postoperatively between the platforms (p=0.012). Correlation between ΔJ0 and preop J0 values (groups 1 and 2) showed that the difference between these two correlation coefficients was significant (z=−3.086, p=0.002). There was statistically significant difference in preoperative mean values for J0 (p<0.001) between the groups 3 and 4. There was a statistically significant difference between J0 preop and J0 postop for both platforms (p<0.001). Correlation between ΔJ0 and preop J0, and between ΔJ45 and preop J45 for groups 3 and 4 showed that difference between these two correlation coefficients was significant (z=−3.533, p=0.0004; z=−2.886, p=0.004). Vector analysis by Alpins showed that negative SIA power (y1) was significantly correlated with negative TIA power (x1) and sine of the TIA axis (x2) as follows: [a] i, y1=0.829X1–0.403X2–0.325 (F=87.76, R=0.804, P<0.001, N=127); ii, y1=0.891X1–0.037X2-0.192 (F=240.06, R=0.901, P<0.001, N=119) and [b] i, y1=1.063X1+0.233X2+0.411 (F=990.99, R=0.881, P<0.001, N=61); ii, y1=1.029X1– 0.115X2+0.322 (F=270.12, R=0.908, P<0.001, N=111). The sine of negative SIA axis (y2) was significantly correlated with negative TIA power (x1) and TIA axis (x2) as follows: [A] I, y2=0.951x2–0.007x1+0.008 (F=446.58, r=0.950, p<0.001, n=127); II, y2=0.856x2+0.007x 1+0.105 (F=277.18, r=0.912, p<0.001, n=119) and [B] I, y2=0.953x2 +0.009x1+0.075 (F=362.6, r=0.963, p<0.001, n=61); II, y2=0.977x2–0.004x1+0.002 (F=2910.9, r=0.990, p<0.001, n=111). ----- CONCLUSIONS: Both lasers showed effective in terms of UDVA, CDVA, spherical correction, and preservation of high-order aberrations. However, Amaris was more effective in cylinder correction. There was no genuine difference post-operatively between groups treated on two different laser platforms according to the vector analyses by Thibos. By using Alpins method, we revealed that both platforms were similar in tending to undercorrect astigmatism; axis rotational errors were apparent, although overall the two platforms differed in terms of direction; and the predicted angle between the SIA and TIA tended to increase when the astigmatic correction was against-the-rule