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Mission and Challenges for Vision Research
MISSION
To demonstrate its commitment to the support of research related to blinding eye diseases and visual disorders, Congress established the National Eye Institute (NEI) in 1968 by passing Public Law 90-489. This law amended the Public Health Service Act, stating that the purpose or mission of the newly created Institute was to:
. . . conduct and support research, training, health information dissemination, and other programs with respect to blinding eye diseases, visual disorders, mechanisms of visual function, preservation of sight, and the special health problems and requirements of the blind.
Inherent in the NEI's mission is the investigation of normal tissue and normal visual processes, so that a more complete understanding may be gained of the abnormal processes that lead to diseases of the eye and disorders of vision. These investigations are conducted in hundreds of extramural laboratories and clinics throughout the United States and in the NEI's own intramural facilities in Bethesda, Maryland.
Health information dissemination activities were added to the mission of the NEI in 1985, and funding for the National Eye Health Education Program (NEHEP) was included in the appropriations bill in Fiscal Year 1988. This allowed the NEI to expand its activities related to the prevention of blindness through public and professional education programs and through the encouragement of regular eye examinations. The NEHEP has already provided valuable information to patients and health professionals alike on diabetic eye disease and glaucoma, two significant causes of adult blindness in this country.
CHALLENGES FOR VISION RESEARCH
In the United States, an estimated 80 million Americans have potentially blinding eye diseases, and 1.1 million people are legally blind. Approximately 12 million people have some degree of visual impairment that cannot be corrected by glasses, and more than 100 million people need corrective lenses to see properly. In 1981, the economic impact of visual disorders and disabilities was approximately $14.1 billion per year. By 1995, this figure was estimated to have risen to more than $38.4 billion—$22.3 billion in direct costs and another $16.1 billion in indirect costs each year.
While progress in understanding and treating many diseases of the eye and disorders of vision has been enormous over the last two decades, the means to prevent or successfully treat some of the most devastating eye diseases still eludes researchers. Yet, powerful new technological tools afford unique opportunities to discover the causes of these diseases and prevent the development of disease or its sight-threatening consequences. These are not only our greatest opportunities, but also our greatest challenges.
Within this report, the most pressing challenges—posed as research needs and opportunities—are specified within the context of the NEI's programmatic structure and special interest areas. Objectives are set out that summarize these challenges, and research strategies are defined for accomplishing these objectives. The following sections are not all-inclusive summaries of the research conducted within each of these programs and interest areas. They simply highlight a few of the ongoing research activities designed to meet current needs and opportunities.
Retinal Diseases. The retina is the thin, transparent, light-sensitive neural tissue that lines the inside of the back of the eye. The retina originates from central nervous system tissue during embryonic development. This tissue contains photoreceptor cells (both rods and cones) and neurons that convert the light images entering the eye into electrical signals that are transmitted to the brain. The choroid is the underlying layer of blood vessels that nourishes the retina. Diseases and disorders of the retina and the choroid account for most of the blindness and visual disability in the United States; the most important include age-related macular degeneration (AMD), diabetic retinopathy, retinitis pigmentosa (RP), retinal detachment, uveitis, and retinal tumors (choroidal melanoma and retinoblastoma).
To meet the challenges of prevention and treatment posed by these blinding diseases and disorders, the NEI supports studies on the development, molecular and cell biology, molecular genetics, and metabolism of the photoreceptor cells and their dependence on the underlying retinal pigment epithelium; the mechanism of the retina's response to light and the initial processing of information that is transmitted to the visual centers of the brain; the pathogenesis of diabetic retinopathy; the fundamental causes of and etiologic factors responsible for uveitis; the molecular genetic mechanisms responsible for producing retinoblastoma and ocular melanoma; the identification of the genes and pathogenic mechanisms causing RP, AMD, and related disorders; and the cellular and molecular events that accompany retinal detachment.
Corneal Diseases. The cornea is the transparent tissue at the front of the eye that plays an important role in refracting or bending light to focus visual images sharply on the retina. The normal cornea has no blood vessels and is nourished by the fluids that bathe it. Because the cornea is the most exposed surface of the eye, it is especially vulnerable to damage from injury or infection. The leading causes of corneal blindness are herpes and other infections, corneal opacification, and inherited and degenerative diseases.
The NEI supports laboratory, preventative, and therapeutic studies to meet the challenges posed by corneal diseases on a wide range of research topics, including: the regulation of genes that express proteins unique to corneal tissue; the details of the macromolecular and supramolecular assembly of extracellular corneal matrices; the characterization of cytokines and cell surface receptors that interact with corneal cells, pathogens, and blood-borne cells; the mechanisms that maintain corneal hydration and transparency; the physiologic basis for immune privilege in the cornea; corneal wound healing; the biomechanics of the cornea; the cellular and molecular mechanisms by which corneal transplants are rejected; and the role of specific viral genes in the establishment, maintenance, and reactivation of corneal herpetic infections.
Lens and Cataract. A cataract is an opacity of the eye's normally clear lens that interferes with vision. Cataract may develop at any time during life, although it is most often associated with advancing age. In addition to aging, cataract may be a consequence of diabetes and other metabolic disorders, trauma, exposure to ionizing radiation, or it may be inherited or congenital in nature. Worldwide, 50 percent of all blindness is due to cataract. Cataract treatment in this country is one of the most successful of all surgical procedures. Each year an estimated $3.4 billion is spent on this procedure through the Medicare program alone. At this time, surgery to remove the opaque lens is the only effective way of treating cataract, and an estimated 1.4 million procedures are performed each year.
The NEI supports research that will ultimately lead to improved treatment or the means to prevent cataract. These include studies of the development and aging of the normal lens of the eye; the identification, at the cellular and molecular level, of those components that maintain the transparency and proper shape of the lens; the control of lens cell division and differentiation; the delineation of the structural and regulatory sequences of crystallin and noncrystallin lens genes; and the impact of continual oxidative insult on the lens.
Glaucoma. Glaucoma is a group of disorders that share a distinct type of optic nerve damage that can lead to blindness. This damage causes death of the retinal ganglion cells that comprise the optic nerve. Glaucoma is often associated with increased pressure within the eye caused by a buildup of aqueous humor, the fluid produced by the ciliary body that nourishes the cornea and lens. Although researchers once thought that glaucoma resulted solely from increased pressure, they now know that the elevation in the pressure within the eye is only one of the risk factors for the disease. Although glaucoma is primarily a disease of the aging, it may occur at any age or at birth. It can occur as a primary disorder or it can be secondary to other ocular or systemic conditions. Glaucoma is a major health problem and the number one cause of blindness in African-Americans. Approximately 3 million Americans have glaucoma; at least half of all those who have glaucoma are unaware of their condition; and as many as 120,000 are now blind from the disease. Blindness from glaucoma is estimated to impose significant costs on the U.S. Government in Social Security benefits, lost tax revenues, and healthcare expenditures.
To meet the challenges in improving treatment for or preventing visual loss from glaucoma, the NEI supports clinical trials that assess the role of medical and surgical therapy in the treatment of the disease. The NEI also supports studies on the gene expression and regulation of the extracellular matrix proteins of the trabecular meshwork; identification and characterization of genes that are involved in the development of glaucoma; the basic mechanisms that control aqueous humor dynamics; the design of better pharmacologic agents to modulate aqueous humor secretion and outflow; and the pathological processes that lead to glaucomatous neuropathy.
Strabismus, Amblyopia, and Visual Processing. Research in this program encompasses a broad range of clinical and laboratory studies concerned with the structure and function of the neural pathways from the retina to the brain, the central processing of visual information, visual perception, the control of ocular muscles, and refraction. A large number of congenital, developmental, and degenerative abnormalities affect the visual sensorimotor system, but three disorders are of primary concern: (1) strabismus or the misalignment of the eyes; (2) amblyopia, or lazy eye, in which one eye has reduced vision due to misalignment or unequal refraction; and (3) refractive errors, especially myopia (nearsightedness) and hyperopia (farsightedness). These are frequent causes of visual impairment in children that may persist throughout life. Strabismus occurs in 3 percent to 4 percent of the U.S. population, and amblyopia in 2 percent to 4 percent. Refractive errors—myopia (nearsightedness), hyperopia (farsightedness), and presbyopia (difficulty focusing on near objects with advancing age)—occur in an estimated 60 percent of the population, who need some form of corrective lenses.
The NEI supports a broad range of laboratory, therapeutic, and preventative studies that are concerned with the development and function of the neural pathways from the eye to the brain; the central processing of visual information; visual perception; optical properties of the eye; oculomotor function; functioning of the pupil; and control of the ocular muscles. Additional emphasis is on research on optic neuropathies, eye movement disorders, and the development of myopia.
Visual Impairment and Its Rehabilitation. Each of the formal programs encompasses research on diseases and disorders that can produce blindness and on a broad range of lesser degrees of visual impairment that may also be disabling. Some individuals require simple optical or mechanical aids to perform daily functions adequately, while others may need more specialized devices. Although not one of the five formal disease-oriented programs at the NEI, this area of research in the NEI strategic plan is a measure of its importance as a means of ameliorating the effects of blindness and impaired vision. The leading causes of visual impairment are diseases that are common among the elderly, such as AMD, cataract, glaucoma, diabetic retinopathy, and optic nerve atrophy. As noted earlier, an estimated 1.1 million people in this country are legally blind, and approximately 12 million have some degree of uncorrected visual impairment.
The NEI supports research to understand the origins of visual impairment and assist in the rehabilitation of those who have such disabilities. To meet the research challenges in this field, the NEI supports projects aimed at improving the methods of specifying, measuring, and categorizing loss of visual function; devising strategies to help visually impaired people maximize the use of their residual vision; systematically evaluating new and existing visual aids; developing an adequate epidemiological base to understand the causes of blindness, partial loss of sight, and visual anomalies; and studying the optical, electronic, and other rehabilitative needs of people with visual impairments.
Health Services Research. Because health care is important to all Americans—as taxpayers and as patients—the NEI and the NAEC felt compelled to devote a section specifically to this vital topic. As defined by the NEI, the field of health services research includes a broad range of diverse issues, such as increasing patient access to and utilization of visioncare services, improving the delivery of vision services by eyecare professionals, and measuring the visual health of patients receiving eyecare services. The challenges in this area include increasing public awareness of the personal and societal costs of visual impairment and ensuring that visioncare services are allocated to those most in need.
The sections that follow are the reports from each of the seven panels described earlier. These reports:
- Provide greater detail in each area of research.
- Identify the goals and objectives on which the research will be focused over the coming 5 years.
- Identify the needs and opportunities that give rise to these goals and objectives.
- Specify the strategies that will be used to accomplish them.
We at the NEI fully recognize the many challenges that lie ahead as we attempt to accomplish our mission. We believe that this strategic plan charts a course for continued progress in vision research in the new millennium.
