Researchers from the School of Optometry and the Department of Ophthalmology at Indiana University have developed new technology, based on the principles of adaptive optics, to detect the earliest warning signs of diabetic retinopathy. Previously, these microscopic changes were not detectable using standard diagnostic techniques.
The research, entitled In vivo adaptive optics microvascular imaging in diabetic patients without clinically severe diabetic retinopathy, was published in the March 1, 2014 issue of Biomedical Optics Express. Published by the Optical Society of America, Biomedical Optics Express provides peer-reviewed papers on technology development, biomedical studies, and clinical applications.
[Editor’s note: “In vivo” refers to processes taking place in a living human or other organism; “in vitro” refers to processes taking place in a test tube or culture dish, typically in a laboratory.]
The authors are Stephen A. Burns, Ann E. Elsner, Toco Y. Chui, Dean A. VanNasdale, Jr., Christopher A. Clark, Thomas J. Gast, Victor E. Malinovsky, and Anh-Danh T. Phan, who represent the following institutions: School of Optometry, Indiana University; and Department of Ophthalmology, Indiana University School of Medicine.
What is Retinopathy?
Retinopathy is a general term that describes damage to the retina, which is the thin, light-sensitive tissue that lines the inside surface of the eye. Nerve cells in the retina convert incoming light into electrical impulses, which are carried by the optic nerve to the brain. Retinopathy occurs when there is damage to the small blood vessels that nourish tissue and nerve cells in the retina.
Retinopathy is a frequent complication of diabetes and uncontrolled high blood pressure, and is a leading cause of blindness and low vision among adults in the United States.
“Proliferative” is a general term that means to grow or increase at a rapid rate by producing new tissue or cells. When the term “proliferative” is used in relation to diabetic retinopathy, it describes the growth, or proliferation, of abnormal new blood vessels in the retina. “Non-proliferative” indicates that this process is not yet occurring. Proliferative diabetic retinopathy affects approximately 1 in 20 individuals with the disease.
Diabetic retinopathy usually has no early warning signs. It can be detected only through a comprehensive eye examination that looks for early signs of the disease, including leaking blood vessels; macular edema or swelling; pale, fatty deposits on the retina; damaged nerve tissue; and any changes to the retinal blood vessels.
About the Research
From New technique detects microscopic diabetes-related eye damage in Phys.org News:
… important early-warning signs were invisible to existing diagnostic techniques, requiring new technology based on adaptive optics. Stephen Burns, professor and associate dean at the IU School of Optometry, designed and built an instrument that used small mirrors with tiny moveable segments to reflect light into the eye to overcome the optical imperfections of each person’s eye.
The instrument designed by Burns takes advantage of adaptive optics to obtain a sharp image, and also minimized optical errors throughout the instrument. Using this approach, the tiny capillaries in the eye appear quite large on a computer screen.
“We had not expected to see such striking changes to the retinas at such early stages,” said Ann Elsner, professor and associate dean in the Indiana University (IU) School of Optometry and lead author of the study.
“We set out to study the early signs, in volunteer research subjects whose eyes were not thought to have very advanced disease. There was damage spread widely across the retina, including changes to blood vessels that were not thought to occur until the more advanced disease states.”
“It is shocking to see that there can be large areas of retina with insufficient blood circulation,” [Burns] said. “The consequence for individual patients is that some have far more advanced damage to their retinas than others with the same duration of diabetes.”
Because these changes had not been observable in prior studies, it is not known whether improved control of blood sugar or a change in medications might stop or even reverse the damage. Further research can help determine who has the most severe damage and whether the changes can be reversed.
More about the Study from Biomedical Optics Express
Excerpted from In vivo adaptive optics microvascular imaging in diabetic patients without clinically severe diabetic retinopathy, available online as an open-source article:
A series of seven diabetic subjects were imaged. Prior to imaging, these subjects were graded by a retinal specialist ophthalmologist as having mild to moderate nonproliferative diabetic retinopathy (NDPR). Six of the seven subjects were type 1 diabetics; the last was type 2. Results were compared to control subjects.
Retinal microvascular [i.e., very small blood vessel, such as capillaries] changes and … [retinal] image changes were evident for all diabetic subjects in all [adaptive optics image] types.
This type of [adaptive optics imaging] applied to the realm of clinical research opens the possibility of improving our understanding of the development of those diabetic retinal changes affecting vision of individuals. In diabetic retinas, there is an inter-related set of microvascular changes that develop over time.
Improved understanding is needed to determine both the patterns of capillary [i.e., the smallest blood vessels] changes which occur over time in different patients and to test whether the changes seen with the [adaptive optics imaging] correspond to the clinical classification and whether they are better [predictors] of the eventual clinical outcome.
In summary, using [adaptive optics imaging] has allowed us to visualize capillary abnormalities in subjects with mild and moderate NPDR, indicating that pre-neovascular processes are already occurring in some individuals. These observed changes could contribute to the variability in response to treatment in diabetic patients.
Thus, these microvascular changes … could hold the key for improved clinical classification of diabetic patients, better understanding of the mechanisms of diabetic retinopathy, and development of more effective therapies through better patient monitoring of pharmacological intervention using this technology.
VisionAware will provide updates of this important diabetes and diabetic retinopathy research as they become available.