November 6, 2015

Part 1 – The Blood Supply

Philosophers have long believed that the eyes are the windows to the soul, but at eyeDOCS we are interested in the practical information that the examination of the inner eye can provide.

The retina, which is the tissue lining the inside of the eye, is home to tens of millions of nerve cells. Because these cells use very large amounts of energy, they need a dense network of blood vessels to provide nutrients and remove waste. The appearance of these blood vessels can give clues about the health of the blood supply in other parts of the body.

For centuries, anatomists and physicians have looked through the transparent window (the cornea) at the front of the eye to view the retinal blood vessels and optic nerves. Equally important is recording the appearance of these structures so that we can watch for future changes.

During my time in optometry school, we were taught to view the internal anatomy of each of our patient’s eyes and record our findings by making diagrams with pencil and paper. Considering that the blood vessels are as unique and complex as the swirls of our fingerprints, one can imagine how daunting this was. Thankfully we have alternatives now. When retinal cameras first appeared, they utilized Polaroid film and a special lens to focus into the eye.

As digital cameras and their associated software have evolved we now have the ability to not only capture images, but to do so at different angles and magnifications. These images can be processed to give a wealth of information about the health of the blood vessels and they can be saved for future comparison.

ri1

Example: This is the inside of my right eye. The red squiggly lines are the blood vessels. Changes in their direction, colour, size, or shape can indicate problems with my bodys blood supply. The big yellow circle is the optic nerve (more on that during a future post).

Since the cost of collecting, processing, examining, and storing these images is not covered by OHIP, we are often asked if retinal imaging is really necessary. The truth is that we won’t know the answer to that question until years after your current visit. Only by collecting the images can we verify the health of the eyes during the appointment. These baseline images will also prove useful in the future, if we suspect there may be anatomical changes in the eye.

Consider the example of Mrs. S. She is a long term patient who is being treated for a disease called temporal arteritis. Sufferers of this condition have an immune system that can attack the blood vessels in the head. Damage to these vessels can cause strokes, blindness, or even death. Although her rheumatologist believed that Mrs. S had her condition under control with medication, our retinal imaging suggested otherwise.

ri2

In the image above, we see the beginnings of what is known as a Branch Retinal Vein Occlusion. There are hemorrhages in the retina that suggest blood and fluid are becoming trapped in the retina. Although Mrs. S was able to see 20/20 at our appointment, failure to detect this condition and to treat the underlying cause could lead to profound vision loss or worse. With our retinal image, it was much easier to find this anomaly and inform her other physicians. Her retina will be rechecked with this technology over the coming weeks and months to ensure that she recovers successfully.

Below are more common examples of systemic health problems that can be diagnosed and monitored through retinal examination and imaging.

ri3

This is a patient with Diabetic Retinopathy. Note the scattered dark red spots representing leaking blood vessels and hemorrhages. Diabetes is the most common cause of blindness among working aged adults in the developed world. Early diagnosis of Diabetic Retinopathy is crucial for improving the patient care. Image courtesy of OPTOS.

ri4

Here is an example of a cholesterol plaque in a peripheral blood vessel. Because these blood vessels are connected to the carotid artery, such plaques can indicate an elevated risk of stroke. Image courtesy of OPTOS.

ri5

Another common diagnosis: hypertensive retinopathy. High blood pressure can cause damage in various ways. In this image, white cloudy smudges result from a lack of oxygen reaching the retinal tissue. Image courtesy of OPTOS.

In short, retinal imaging is an invaluable tool for the optometrist evaluating the health of your blood supply. In the next post we will examine the optic nerves and central nervous system through retinal imaging.

Shawn-Charland-200x300

About the Author
Dr. Shawn Charland

Dr. Shawn Charland graduated from the University of Waterloo, School of Optometry in 1999. He has been practicing optometry since and joined the eyeDOCS team in 2006 and became a partner in 2007. For more information about Dr. Charland and his specialized interests relating to optometry, click here.