Pathophysiology of aniridia-associated keratopathy: Developmental aspects and unanswered questions

Aniridia, a rare congenital disease, is often characterized by a progressive, pronounced limbal insufficiency and ocular surface pathology termed aniridia-associated keratopathy (AAK). Due to the characteristics of AAK and its bilateral nature, clinical management is challenging and complicated by the multiple coexisting ocular and systemic morbidities in aniridia. Although it is primarily assumed that AAK originates from a congenital limbal stem cell deficiency, in recent years AAK and its pathogenesis has been questioned in the light of new evidence and a refined understanding of ocular development and the biology of limbal stem cells (LSCs) and their niche. Here, by consolidating and comparing the latest clinical and preclinical evidence, we discuss key unanswered questions regarding ocular developmental aspects crucial to AAK. We also highlight hypotheses on the potential role of LSCs and the ocular surface microenvironment in AAK. The insights thus gained lead to a greater appreciation for the role of developmental and cellular processes in the emergence of AAK. They also highlight areas for future research to enable a deeper understanding of aniridia, and thereby the potential to develop new treatments for this rare but blinding ocular surface disease

Unobtrusive and pervasive video-based eye-gaze tracking

Eye-gaze tracking has long been considered a desktop technology that finds its use inside the traditional office setting, where the operating conditions may be controlled. Nonetheless, recent advancements in mobile technology and a growing interest in capturing natural human behaviour have motivated an emerging interest in tracking eye movements within unconstrained real-life conditions, referred to as pervasive eye-gaze tracking. This critical review focuses on emerging passive and unobtrusive video-based eye-gaze tracking methods in recent literature, with the aim to identify different research avenues that are being followed in response to the challenges of pervasive eye-gaze tracking. Different eye-gaze tracking approaches are discussed in order to bring out their strengths and weaknesses, and to identify any limitations, within the context of pervasive eye-gaze tracking, that have yet to be considered by the computer vision community.peer-reviewe

Endothelial keratoplasty combined with scleral fixation intraocular lens

describe, for the first time, the surgical management of two aphakic patients with corneal decompensation treated with concomitant ultrathin-Descemet stripping automated endothelial keratoplasty (UT-DSAEK) and implantation of two different scleral-fixated (SF) intraocular lenses (IOLs), namely sutureless SF (SSF) Carlevale IOL (Soleko, Italy; Figure 1) or Morcher Type 90L IOL (Morcher GmbH, Germany; Figure 2). Both IOLs are hydrophilic acrylic. The Carlevale IOL is 13.2 mm long with a 6.5 mm optic plate, foldable and injectable through a 2.2 mm corneal tunnel. A T-shaped harpoon protrudes off the closed haptics and is designed to be externalized underneath a partial thickness scleral flap (Figure 1). The Morcher Type 90L IOL is 15 mm long with a 6.5 mm optic plate. The two C-loop haptics have an eyelet for the passage of the sutures for the scleral fixatio

Minimally Invasive Glaucoma Surgery

This book covers all aspects of minimally invasive glaucoma surgery (MIGS) and provides detailed information on each MIGS device, including its mechanism of action; patient selection; implantation techniques; post-operative management; and a review of the existing literature. Step-by-step descriptions are provided for the surgical technique used in implanting each MIGS device, accompanied by clear photographs of each surgical stage. Other areas covered include intra-operative gonioscopy (with tips on optimising the view of the anterior chamber angle) and the management of the intra-operative and post-operative complications. Essential information on the anatomy and physiology of the different aqueous outflow pathways is also included. A separate chapter addresses the introduction of MIGS globally, including the consideration of different reimbursement environments and the different types of glaucoma, e.g. angle closure glaucoma. This book will assist both glaucoma surgeons and general ophthalmologists in overcoming the learning curve involved in performed MIGS, by providing valuable and practical clinical pearl

Keratoprostheses for corneal blindness: a review of contemporary devices

According to the World Health Organization, globally 4.9 million are blind due to corneal pathology. Corneal transplantation is successful and curative of the blindness for a majority of these cases. However, it is less successful in a number of diseases that produce corneal neovascularization, dry ocular surface and recurrent inflammation, or infections. A keratoprosthesis or KPro is the only alternative to restore vision when corneal graft is a doomed failure. Although a number of KPros have been proposed, only two devices, Boston type-1 KPro and osteo-odonto-KPro, have came to the fore. The former is totally synthetic and the latter is semi-biological in constitution. These two KPros have different surgical techniques and indications. Keratoprosthetic surgery is complex and should only be undertaken in specialized centers, where expertise, multidisciplinary teams, and resources are available. In this article, we briefly discuss some of the prominent historical KPros and contemporary devices

Optimizations and applications in head-mounted video-based eye tracking

Video-based eye tracking techniques have become increasingly attractive in many research fields, such as visual perception and human-computer interface design. The technique primarily relies on the positional difference between the center of the eye\u27s pupil and the first-surface reflection at the cornea, the corneal reflection (CR). This difference vector is mapped to determine an observer\u27s point of regard (POR). In current head-mounted video-based eye trackers, the systems are limited in several aspects, such as inadequate measurement range and misdetection of eye features (pupil and CR). This research first proposes a new `structured illumination\u27 configuration, using multiple IREDs to illuminate the eye, to ensure that eye positions can still be tracked even during extreme eye movements (up to ±45° horizontally and ±25° vertically). Then eye features are detected by a two-stage processing approach. First, potential CRs and the pupil are isolated based on statistical information in an eye image. Second, genuine CRs are distinguished by a novel CR location prediction technique based on the well-correlated relationship between the offset of the pupil and that of the CR. The optical relationship of the pupil and CR offsets derived in this thesis can be applied to two typical illumination configurations - collimated and near-source ones- in the video-based eye tracking system. The relationships from the optical derivation and that from an experimental measurement match well. Two application studies, smooth pursuit dynamics in controlled static (laboratory) and unconstrained vibrating (car) environments were conducted. In the first study, the extended stimuli (color photographs subtending 2° and 17°, respectively) were found to enhance smooth pursuit movements induced by realistic images, and the eye velocity for tracking a small dot (subtending \u3c0.1°) was saturated at about 64 deg/sec while the saturation velocity occurred at higher velocities for the extended images. The difference in gain due to target size was significant between dot and the two extended stimuli, while no statistical difference existed between the two extended stimuli. In the second study, twovisual stimuli same as in the first study were used. The visual performance was impaired dramatically due to the whole body motion in the car, even in the tracking of a slowly moving target (2 deg/sec); the eye was found not able to perform a pursuit task as smooth as in the static environment though the unconstrained head motion in the unstable condition was supposed to enhance the visual performance

Minimally Invasive Glaucoma Surgery

This open access book covers all aspects of minimally invasive glaucoma surgery (MIGS) and provides detailed information on each MIGS device, including its mechanism of action; patient selection; implantation techniques; post-operative management; and a review of the existing literature. Step-by-step descriptions are provided for the surgical technique used in implanting each MIGS device, accompanied by clear photographs of each surgical stage. Other areas covered include intra-operative gonioscopy (with tips on optimising the view of the anterior chamber angle) and the management of the intra-operative and post-operative complications. Essential information on the anatomy and physiology of the different aqueous outflow pathways is also included. A separate chapter addresses the introduction of MIGS globally, including the consideration of different reimbursement environments and the different types of glaucoma, e.g. angle closure glaucoma. This book will assist both glaucoma surgeons and general ophthalmologists in overcoming the learning curve involved in performed MIGS, by providing valuable and practical clinical pearl

Techniques for Ocular Biometric Recognition Under Non-ideal Conditions

The use of the ocular region as a biometric cue has gained considerable traction due to recent advances in automated iris recognition. However, a multitude of factors can negatively impact ocular recognition performance under unconstrained conditions (e.g., non-uniform illumination, occlusions, motion blur, image resolution, etc.). This dissertation develops techniques to perform iris and ocular recognition under challenging conditions. The first contribution is an image-level fusion scheme to improve iris recognition performance in low-resolution videos. Information fusion is facilitated by the use of Principal Components Transform (PCT), thereby requiring modest computational efforts. The proposed approach provides improved recognition accuracy when low-resolution iris images are compared against high-resolution iris images. The second contribution is a study demonstrating the effectiveness of the ocular region in improving face recognition under plastic surgery. A score-level fusion approach that combines information from the face and ocular regions is proposed. The proposed approach, unlike other previous methods in this application, is not learning-based, and has modest computational requirements while resulting in better recognition performance. The third contribution is a study on matching ocular regions extracted from RGB face images against that of near-infrared iris images. Face and iris images are typically acquired using sensors operating in visible and near-infrared wavelengths of light, respectively. To this end, a sparse representation approach which generates a joint dictionary from corresponding pairs of face and iris images is designed. The proposed joint dictionary approach is observed to outperform classical ocular recognition techniques. In summary, the techniques presented in this dissertation can be used to improve iris and ocular recognition in practical, unconstrained environments

Malpositioned and dislocated intraocular lenses : management, complications and surgical repositioning

Cataract surgery (exchange of the non-transparent crystalline lens with an IOL) is the most frequent surgery in Sweden, accounting for more than 130000 surgeries per year. Therefore, complications associated with cataract surgery affect a significant number of patients. One of the complications is IOL dislocation, meaning that the IOL is not located at the central part of the optical zone, which often causes visual impairment. The overall aim of this thesis was to deepen knowledge about dislocated IOLs, especially surgery of out-of-the-bag and in-the-bag dislocated IOLs and management of uveitis-glaucoma-hyphema (UGH) syndrome. Study I had a retrospective case-control design with a total of 32 patients, and included out-of-the-bag dislocated IOL. The aim was to evaluate the efficacy and safety of 3-piece IOL suturing to the iris. The case group (n=14; Iris group) underwent dislocated out-of-the-bag 3-piece IOL suturing to the iris. The control group (n=18; Exchange group) underwent IOL exchange with a new IOL sutured to the sclera. The groups were followed in the median of 13.5 (interquartile range (IQR) 10–20) and 12.5 (IQR 10–14) months, respectively. Best corrected visual acuity (BCVA) improved significantly in each group with no significant difference in either final BCVA or final intraocular pressure (IOP) between the groups. Complication frequency was similar in the groups. Surgically induced corneal astigmatism (SIA) and number of postoperative visits were significantly lower in the Iris group. Study II, a prospective randomized clinical trial with a cross-sectional part, included in-the-bag dislocated IOL. A total of 177 patients were analyzed in this study. The aim was to evaluate three-dimensional (3-D) IOL position, refractive change, and IOL-induced astigmatism (IIA), also importance of capsular fibrosis on postoperative IOL position after IOL suturing to the sclera (2.5 mm behind the limbus) using 2 surgical methods: Ab Externo Scleral Suture Loop Fixation (Group A) and a modification, Embracing the Continuous Curvilinear Capsulorhexis (CCC), a technique created by L.A. (Group B). Additionally, the study evaluated the usefulness of swept-source anterior segment optical coherence tomography (SS–AS-OCT) for measuring 3-D IOL position. A total of 117 patients (117 eyes) with in-the-bag dislocated IOL were randomized into Group A (n=61) or Group B (n=56). The control group consisted of patients with ordinary pseudophakia (n=60). The median IOL tilt did not significantly differ between Group A (7.8°, IQR 5.9°–12.0°) and Group B (8.3°, IQR 6.4°–10.8°) but each group was significantly different from the ordinary pseudophakia (5.4°, IQR 3.9°–7.1°) by the mean of 3.75° (CI (confidence interval) 2.54°–4.95°). The direction of IOL tilt was inferotemporal in 87%–87.5% of patients in each of the three groups, and a mirror symmetry was observed between the left and right eyes. IOL surgery resulted in significant myopic shift. In eyes without capsular fibrosis, the median IOL tilt was 15.5° (IQR 7.8°–21.7°) in Group A (n=7) and 7.0° (IQR 6.6°–11.4°) in Group B (n=5) although without a statistically significant difference. IIA was 0.075 D for each degree of IOL tilt, which was statistically significant. Five patients (three in Group A and two in Group B, of which one IOL was dislocated by intraocular gas) were re-operated after their one-month follow-up visit. IOL position could be measured with SS–AS-OCT in all cases if the IOL could be seen in the pupil. It was also possible to measure and quantify the capsular bag thickness. Study III focused on UGH syndrome, and had a retrospective case-control design with a cross-sectional part and a descriptive part. A total of 213 patients were included. The study comprised both out-of-the-bag and in-the-bag dislocations as well as other types of IOL malpositions; however, all causing UGH syndrome. The study aimed to evaluate the effect of UGH treatment, a need for IOP-lowering treatment, clinical manifestation (including iris-IOL contact signs) and usage of blood thinners (anticoagulants and antiaggregants), also, which examination–clinical, AS-OCT, or ultrasound biomicroscopy (UBM)–was the most effective tool to diagnose UGH syndrome. Three groups of patients were compared: UGH syndrome (n=71), dislocated IOL without UGH (n=71) and uncomplicated pseudophakia (n=71). Surgical treatment was effective in approximately 77% of cases. IOP and BCVA improved significantly in the operated patients but not in the non-operated patients. In total, 51% of all patients (57% of operated patients) needed IOP-lowering therapy after UGH resolution, and IOP≥22 mmHg at the first (1st) hemorrhage was the only significant predictor identified for this. Pseudophacodonesis (IOL-donesis) was seen in 22.5% of patients at the beginning of UGH syndrome, and was significantly more frequent than in the Pseudophakic group. Transilluminating iris defects (TID) in the UGH group were not more frequent than in the Dislocated group at the beginning of UGH. However, the shape of TIDs differed significantly: haptic or optic edge formed TIDs were seen more frequently in the UGH group. Patients with UGH syndrome did not use blood thinners more frequently than patients in Dislocated group, except Warfarin (Waran®). Examination on a slit-lamp, AS-OCT, and UBM showed iris-IOL contact in 97%, 19%, and 21% of patients, respectively. Conclusions: Suturing out-of-the-bag dislocated 3-piece IOL to the iris is a safe and effective surgical treatment with less SIA and fewer postoperative visits to an ophthalmologist than IOL exchange. Suturing in-the-bag dislocated IOL to the sclera results in good IOL position with both surgical methods, although the position differs from the normal pseudophakia by approximately 3.75° which has little clinical significance as IOL-tilt induced astigmatism is low. However, IOL suturing to the sclera induces myopic shift in cases when the IOL is sutured 2.5 mm behind the limbus. A new study with more patients without capsular fibrosis would show whether IOL position is better with the modified method than with the traditional one in this subgroup. SS–AS-OCT is useful for 3-D IOL position quantification after IOL repositioning. Surgical treatment does not guarantee resolution of UGH syndrome, though BCVA results are better than with conservative treatment. IOL-donesis is a risk factor for UGH syndrome. The impact of Warfarin (Waran®) on UGH development should be investigated further, although other blood thinners probably do not increase the risk for UGH syndrome. TIDs are not specific to UGH syndrome unless they are formed like the haptic or optic edge. Every second patient may need IOP-lowering therapy; IOP≥22 mmHg at the first hemorrhage predicts the need for IOP-lowering treatment in a long run (after UGH resolution). Follow up time should be long after UGH resolution. Clinical examination was more useful for detecting iris-IOL contact than AS-OCT or UBM in study III