The Effects Of Complex Optical Environments On The Development Progression And Control Of Myopia

Myopia or nearsightedness is a condition in which the axial length of the eye is too long relative to its optical focal length. This condition is reaching epidemic levels worldwide, and has become a tremendous public health burden. Myopia is one of the leading causes of vision loss and high myopia significantly increases the risk of permanent blindness. Consequently, myopia cannot be considered as a benign condition and early interventions aimed at slowing down or even stopping the progression of myopia rather than merely correcting the associated optical focusing error is of great importance. The consistent evidence from animal model studies showing that imposed hyperopic defocus, if sustained, comprises an effective myopogenic stimulus, accelerating eye growth, while imposed myopic defocus slows ocular elongation, has motivated clinical studies using bifocal and progressive addition spectacles for myopia control. While these studies, reviewed in Chapter 2 of this dissertation, failed to provide convincing evidence for a clinically significant treatment effect, i.e., slowed myopia progression; smaller scale, non-randomized studies using multifocal soft contact lenses and orthokeratology lenses have shown much more promising effects in terms of slowing myopia progression. However, the mechanism(s) underlying the latter anti-myopia treatment effects are poorly understood, thereby limiting their further refinement. In addition to the aforementioned systematic review of relevant clinical evidence for optical interventions for myopia control, this dissertation described 3 other studies using chick model, representing efforts to further understand how multifocal optical environments affect normal ocular development, specifically the process of emmetropization. These manipulations have also been used as a tool to investigate the mechanism underlying the myopia controlling effect of the novel contact lens applications referred above. Chapter 2 describes a systematic review and meta-analysis performed on randomized controlled trials investigating the effects of three traditional optical interventions, bifocal and progressive addition spectacles, and rigid contact lenses, all believed to control myopia progression, based on anecdotal evidence. The overall treatment effect was estimated to be only small and clinically insignificant. A number of reasons were proposed to explain the discrepancy between the results of related animal studies and these clinical trials - strong support for optical control of myopia from the former studies and inconclusive results from the latter studies. Poor compliance to the spectacle corrections in clinical studies, inaccurate measurement of adherence to the treatments, inadequate and potentially, ambiguous classification systems for clinical myopia, and potential flaws in the optical designs are likely to have contributed to the discouraging results from the clinical trials. Chapter 3 describes the first of three studies in which the chick model was used to test the effects on ocular growth of a series of custom-designed 2-zone multifocal "spectacle" lenses. This and the two follow-up studies using this model have the following merits; they made use of standardized experimental paradigms and objective methods of measurement to track ocular changes. The first study applied the lenses in a simple experimental paradigm, in which monocular lenses were attached to the normal eyes of young chickens. The 2-zone lenses included a plano zone, either in the center or peripheral surround, with either positive or negative power (+5 or -5 D) incorporated into the other zone. The size of the central zone was also allowed to vary, to control the size of the unifocal central and peripheral retinal areas, and intermediate multifocal zone, as was the placement of the powered zone, i.e. in the center or periphery of the lenses. Single vision lenses were included as a control treatment. Two important observations from this study were that 1) peripheral optical defocus can influence both peripheral (off-axis) and central (on-axis) refractive error development and 2) the inhibitory effect on axial ocular growth of myopic defocus imposed using 2-zone lenses (positive zones) could exceed that induced by single vision lenses of the same power. These results suggested complex interactions between adjacent retinal regions, with the peripheral retina apparently able to decode optical defocus, as well as complex interactions between the eyes own optical aberrations and those of the 2-zone lenses, which introduced large amounts of spherical aberration. Chapter 4 described a closely related study in which subsets of the same 2-zone lenses were tested on eyes that had undergone surgical manipulations (sectioning of the ciliary nerve, CNX or iridectomy, ID) to investigate the influence of the pupil size of the eye as well as accommodation on the effects of the 2-zone lenses. Both were uncontrolled in the first study; yet create a dynamic optical system on which the multifocal optical environment was imposed. The ID surgery produced a fixed dilated pupil without any effect on accommodation (confirmed in another study, reported in Appendix I), while the CNX surgery produced a similarly enlarged pupil while also eliminating accommodation. This study revealed pupil size to be a critical factor in the treatment effects of 2-zone lenses, likely to reflect at least in part, its influence on the optical experience of various retinal zones (center to periphery), and also suggested a significant role of accommodation in the decoding of imposed optical defocus stimuli, in this case, complex multifocal optical stimuli. Chapter 5 described a third study which attempted to develop a clinically more relevant scenario; specifically, 2-zone lenses that incorporated two different negative powers ( -5 & -10 D) in two optical zones (center & periphery or vice versa), were tested on both normal eyes and eyes made myopic before being fitted with one of the 2-zone lenses. The latter combination was intended to simulate the ocular conditions created when concentric multifocal contact lenses, i.e. with a near addition, are prescribed to human myopes, one of the novel, myopia control treatments currently being explored. When the 2-zone lenses were fitted to normal eyes, they induced myopia, of a magnitude falling between the values expected, had single vision lenses of the same powers been used. However, on myopic eyes, the lenses had a strong myopia inhibiting effect with the already induced myopia undergoing substantial regression. This result supports the further investigation of appropriately designed concentric multifocal contact lenses for the control of myopia progression. In summary, the studies reported in this dissertation indicate complex interactions between central and peripheral retinal regions in decoding and responding to complex defocus signals as well as critical influences of pupil size and accommodation on these processes. The strong and consistent inhibitory effects on ocular growth of concentric 2-zone lenses incorporating a zone of either positive power or a near addition, 2-zone designs lend plausibility to the notion of using custom-designed novel optical treatments for the control of myopia progression.

This book is open access under a CC BY 4.0 license. This open access book discusses basic clinical concepts of myopia, prevention of progression and surgical treatments for myopia and pathological myopia. It also summarises the latest evidence and best practices for managing myopia, high myopia and its complications. Written by leading experts, the book addresses clinical diagnosis and interpretation of imaging modalities, and various complications of myopia such as glaucoma, choroidal neovascularization, retinal degeneration and cataracts. It is a valuable comprehensive resource for general and sub-specialist ophthalmologists as well as residents and ophthalmologists in training.; This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.

Pathologic Myopia is a major cause of severe vision loss worldwide. The mechanisms for vision loss include cataract, glaucoma, retinal detachment, and above all, myopic maculopathy within the posterior staphyloma. The first edition of Pathologic Myopia is one of the only current books to specifically address this disease and discusses recent developments in imaging technologies and various approaches to treatments, such as laser photocoagulation, photodynamic therapy, pharmaco-therapeutic injections in the vitreous, and surgery. This new edition is a timely update to the standard reference in the field, with new chapters on advanced refractive error correction, genetics, developing a classification system, and special surgical approaches for pathologic myopia. Complete with even more high-quality color images and informative tables, this book is written and edited by leaders in the field and is geared towards ophthalmologists, including residents and fellows in training, glaucoma and cataract specialists, and vitreoretinal macula experts.

Choroidal Disorders provides an overview on various chorioretinal disorders with a special emphasis on choroidal imaging. As our understanding of the choroid has significantly improved with the development of advanced optical coherence tomography (OCT) and its role in posterior segment diseases is gaining new significance, this book focuses on the related improvements, diagnostic capabilities, management and prognosis of various chorioretinal disorders. It covers conventional techniques, such as ultrasonography and indocyanine green angiography as well as the most advanced techniques, including enhanced depth imaging OCT, swept source OCT, and OCT angiography. Concise overview of various chorioretinal disorders, with special emphasis on choroidal imaging Written for practitioners and researchers in sensory systems (vision), ophthalmologists, and retina specialists Covers the most advanced imaging techniques in choroidal disorders, such as enhanced depth imaging OCT, swept source OCT, and OCT angiography

The ability to see deeply affects how human beings perceive and interpret the world around them. For most people, eyesight is part of everyday communication, social activities, educational and professional pursuits, the care of others, and the maintenance of personal health, independence, and mobility. Functioning eyes and vision system can reduce an adult's risk of chronic health conditions, death, falls and injuries, social isolation, depression, and other psychological problems. In children, properly maintained eye and vision health contributes to a child's social development, academic achievement, and better health across the lifespan. The public generally recognizes its reliance on sight and fears its loss, but emphasis on eye and vision health, in general, has not been integrated into daily life to the same extent as other health promotion activities, such as teeth brushing; hand washing; physical and mental exercise; and various injury prevention behaviors. A larger population health approach is needed to engage a wide range of stakeholders in coordinated efforts that can sustain the scope of behavior change. The shaping of socioeconomic environments can eventually lead to new social norms that promote eye and vision health. Making Eye Health a Population Health Imperative: Vision for Tomorrow proposes a new population-centered framework to guide action and coordination among various, and sometimes competing, stakeholders in pursuit of improved eye and vision health and health equity in the United States. Building on the momentum of previous public health efforts, this report also introduces a model for action that highlights different levels of prevention activities across a range of stakeholders and provides specific examples of how population health strategies can be translated into cohesive areas for action at federal, state, and local levels.

In this thoroughly revised and updated third edition of Contact Lens Practice, award-winning author, researcher and lecturer, Professor Nathan Efron, provides a comprehensive, evidence-based overview of the scientific foundation and clinical applications of contact lens fitting. The text has been refreshed by the inclusion of ten new authors – a mixture of scientists and clinicians, all of whom are at the cutting edge of their specialty. The chapters are highly illustrated in full colour and subject matter is presented in a clear and logical format to allow the reader to quickly hone in the desired information. Ideal for an optometrist, ophthalmologist, orthoptist, optician, student, or work in the industry, this book will serve as an essential companion and guide to current thinking and practice in the contact lens field. Highlights of this edition include a new chapter on myopia control contact lenses, as well are completely rewritten chapters, by new authors, on keratoconus, orthokeratology, soft and rigid lens measurement and history taking.

Completely revised, updated, and redesigned, this classic dictionary by Dr. Michel Millodot continues to be an essential resource for all optometrists in training and in practice, as well as residents in ophthalmology. It is also a crucial source of information for anyone involved in vision science and in the optical industry. It now includes many new entries on pathology, pharmacology, investigative techniques, visual perception, optics and contact lenses. This edition presents all of the features that have made it so successful in the past, such as succinct, understandable definitions, comprehensive tables and illustrations, clinical advice, and extensive cross-references. Uniquely blending the best features of a textbook, a dictionary, and a practical handbook, Dictionary of Optometry and Vision Science remains a cornerstone for all those providing eye care, engaged in vision science, or entering the optical industry. Now includes definitions of over 5600 terms, as well as 90 tables and 253 illustrations that enhance understanding of many of the definitions.