Could Glaucoma Actually Be “Diabetes of the Brain”? A New Hypothesis Says Maybe

photograph of retina with glaucoma

A group of medical researchers from India is proposing the radical new hypothesis that glaucoma may indeed be diabetes of the brain.

The research, entitled Glaucoma – Diabetes of the brain: A radical hypothesis about its nature and pathogenesis [i.e., the mechanisms that cause it], has been published in the May 2014 issue of Medical Hypotheses. Published by Elsevier Inc., Medical Hypotheses is a forum for ideas in medicine and related biomedical sciences, publishing “interesting and important theoretical papers that foster the diversity and debate upon which the scientific process thrives.”

The authors are Muneeb A. Faiq; Rima Dada; Daman Saluja; and Tanuj Dada, who represent the following institutions: All India Institute of Medical Sciences, Delhi India; and the University of Delhi, India.

[Editor’s note: In science, a hypothesis is an idea or explanation that is then tested through structured study and experimentation. It is more than a guess, but less than a well-established theory. A scientific hypothesis that survives experimental testing then becomes a scientific theory.]

What Is Glaucoma?

The term “glaucoma” describes a group of eye diseases that can lead to blindness by damaging the optic nerve. It is one of the leading causes of vision loss and blindness.

The human eye continuously produces a fluid, called the aqueous, that must drain from the eye to maintain healthy eye pressure.

In primary open-angle glaucoma, the most common type of glaucoma, the eye’s drainage canals become blocked, and the fluid accumulation causes pressure to build within the eye. This pressure can cause damage to the optic nerve, which transmits information from the eye to the brain.

Normal-tension glaucoma, also called low-tension glaucoma, is a type of glaucoma in which individuals with the disease experience optic nerve damage and subsequent vision loss, despite having normal intraocular pressure (IOP).

Most eye care professionals define the range of normal IOP as between 10 and 21 mm Hg [i.e., millimeters of mercury, which is a pressure measurement]. Most persons with glaucoma have an IOP measurement of greater than 21 mm Hg; persons with normal-tension glaucoma, however, have an IOP measurement within the normal range.

About Diabetes

Diabetes is a metabolic disorder characterized by a high level of glucose in the bloodstream, also called hyperglycemia. Glucose is the principal circulating sugar in the blood and provides energy to all cells in the body.

These cells cannot use glucose, however, without the help of insulin. Insulin is a hormone produced by the pancreas that converts sugar and starch from food into the energy needed to fuel everyday activities. Diabetes occurs when (1) the pancreas does not make or release enough insulin, (2) the body’s cells are resistant to insulin, or (3) both conditions are present. Diabetes is a condition that is treatable but not curable.

Type 1 diabetes (formerly called juvenile-onset, Type I, or insulin dependent) has the following characteristics:

  • It usually occurs before age 30 and affects 5%-10% of individuals with diabetes.
  • It occurs when the body produces little to no insulin (insulin deficiency).
  • Glucose continues to rise in the bloodstream because it cannot enter the body’s cells
  • The body’s immune system destroys its own insulin-producing cells in the pancreas, for reasons that are not yet clear to researchers. Possible reasons include genetic factors, viruses, or a defect in the body’s autoimmune system.
  • Insulin shots are required to sustain life.

Type 2 diabetes (formerly called adult-onset, Type II, or non-insulin dependent) has the following characteristics:

  • It usually occurs after age 30 and affects 90%-95% of individuals with diabetes.
  • It occurs if (1) the pancreas does not produce enough insulin (insulin deficiency), (2) the body’s cells are not able to use insulin correctly and efficiently (insulin resistance), or (3) both conditions are present.
  • Glucose continues to rise in the bloodstream because sufficient levels of insulin are not available to open the cells and allow glucose to enter.
  • It can be managed initially with weight loss, physical activity, and effective meal planning; when the disease progresses, however, oral medication or insulin may also be required.

Glaucoma, Diabetes, and the Brain

From Is glaucoma, in fact, diabetes of the brain?, via Mideast Clinics Directory:

The investigators explore glaucoma and related neurodegenerative [i.e., the degeneration of nervous system tissue] diseases from many perspectives and come up with a … concept of glaucoma being “diabetes of the brain.” On the basis of the striking similarities in genetic, biochemical, and molecular aspects, they have come to recognize that glaucoma is, in fact, a form of brain-specific diabetes.

The authors … explain it in terms of many arguments, including, but not limited to, streptozotocin effects [i.e., a naturally occurring chemical that is toxic to the insulin-producing cells of the pancreas] on the brain, and eye pressure lowering by antidiabetics.

Their study is likely to make a radical shift in the existing paradigm in the understanding of glaucoma (and other neurodegenerative disorders like Alzheimer’s disease). This finding might establish glaucoma as one more diabetes type and may possibly give birth to new concepts in glaucoma therapy, management, and treatment.

More about the Study from Medical Hypotheses

From the article abstract:

Glaucoma is the leading cause of irreversible blindness characterized by … loss of retinal ganglion cells. Its risk increases with progressing age and elevated intraocular pressure. Studies have established that glaucoma is a neurodegenerative disorder in which the damage involves many brain tissues from the retina to the lateral geniculate nucleus [i.e., the vision center of the brain].

Despite much research, the complete pathomechanism [i.e., how a disease progresses] of glaucoma is not known and there is no treatment available except modification of intraocular pressure pharmacologically and/or surgically.

Our hypothesis postulates that glaucoma may possibly be the diabetes of the brain.

Based on the remarkable similarities between glaucoma and diabetes, we propose glaucoma also to be a type of diabetes. Glaucoma and diabetes share many aspects from various molecular mechanisms to involvement of insulin and possible use of antidiabetics in glaucoma therapy.

Additionally, Alzheimer’s disease has already been proposed to be diabetes type-3. We show that Alzheimer’s disease is cerebral glaucoma and diabetes at the same time which … again leads to our hypothesis that glaucoma is diabetes of the brain.

Our proposition may lead to appreciation of certain important facets of glaucoma which have previously not been given due consideration. It also may lead to an alternative classification of diabetes as pancreatic and brain diabetes, thereby widening the vision arena of the understanding of both these disorders.

VisionAware will provide updates of this intriguing research as they become available.