The Pot of Gold at the End of the Rainbow

Have you ever been told that there’s a pot of gold at the end of a rainbow?  You may be skeptical, but it is absolutely true.  You see, rainbows don’t exist in the natural world.  Instead, they exist as an image created within our eyes, thanks to a wonderful and delicate structure called the retina.   It is the retina that is responsible for all the colorful splendor of our visual world, a treasure indeed worth its weight in gold.  A closer look at the retina reveals one of the most remarkable structures in our body.

Form Meets Function

To understand how the retina creates the colors of the rainbow, we have to look at the intricacies of its design.  The retina is a thin structure that lines the inside surface of the eye, similar to the rubber lining on the inside of a basketball.  The retina has a surface area of a silver dollar, and packed within that space are 150 million cells called photoreceptors.  It is upon this sheet of photoreceptors that the light from our world is projected.  Together, these retina cells interpret light of different colors, shapes, and movement, converting them into nerve impulses.  These nerve impulses are then sent to the brain, where higher-level processing turns the images into meaningful information.

How Important is the Retina?

When it comes to quality of vision, the retina is like the Supreme Court… it makes the final decision.  That is why the human body is designed to deliver more blood flow to the retina than any other part of the body, proportional to its weight.  It is also why the retina is completely protected from an immune response, lest the damaging effects of inflammation disrupt the very tiny and fragile components of vision.  Even the structures surrounding the retina, such as the eye socket, eyelids, and eye wall, are specifically designed to protect the retina from injury.  Our bodies have devoted tremendous resources to ensure that our retina functions properly.

 

A Window to the Soul

Despite its privileged status in the body, the retina can still be affected by a wide range of illnesses.  Some of these diseases are specific to the retina, such as age-related macular degeneration and retinal detachment.  Interestingly, the retina can also be damaged by conditions that affect the entire body, such as diabetes or high blood pressure.  In fact, examination of the retina frequently reveals undiagnosed bodily illness.  It is not uncommon for the eye doctor to be the first to catch cancer, a stroke, or an infection before the patient has other symptoms.

 

Caring For Your Retina

Since the retina is so important to vision, it is critical that we take steps to protect it.  As with other organ systems, control of blood sugar, blood pressure, and cholesterol are critical to long-term retinal health.   Stopping smoking and wearing Sunglasses with UV protection are also very important.    Additionally, extensive research has gone into vitamin supplementation for retinal health.  At this time, vitamins are only proven to benefit patients with age-related macular degeneration.  However, there are several formulations of vitamins on the market today that have theoretical benefits to retinal longevity in the healthy consumer.  These supplements typically contain anti-oxidants and nutrients such as lutein, zeaxanthin, and omega-3 fatty acids.  Similarly, a balanced, low-fat diet with plenty of green, leafy vegetables should adequately provide the necessary retinal nutrients, without the need for supplements.

 

New Treatments for Vision Loss in Diabetes

 

“You should have your eyes checked every year,” is a familiar refrain for the 26 million diabetics living in the United States.   The recommendation for annual dilated eye examinations is so well ingrained in the psyche of diabetic patients that it might as well be printed on the front of their glucose monitors.  What isn’t so well appreciated by diabetics, however, is that a revolution in the management of diabetic vision loss is quietly taking place, promising to disrupt a traditional model that has existed for decades.  Thanks to new diagnostic technology and therapeutics, this revolution has changed the conversation in diabetes from that of slowing vision loss to maximizing vision gain.

Although there are many reasons for vision loss in diabetes, by far the most common cause is diabetic retinopathy, characterized by progressive damage to the retina and its blood supply due to elevated blood glucose.  Almost all diabetics develop diabetic retinopathy, a fact which makes it the largest cause of blindness among working age adults.  Although frequently symptomatic, patients with diabetic retinopathy may accumulate retinal damage for years without noticing a change in their vision.

The traditional approach to diabetic retinopathy began in the 1970s and 80s with the completion of two national clinical trials: the Diabetic Retinopathy Study (DRS) and the Early Treatment of Diabetic Retinopathy Study (ETDRS).  These studies demonstrated the value of using laser light to selectively burn the retina in order to slow the progression of vision loss.  Since that time, millions of diabetics have benefitted from these laser therapies.  However, even with therapy, these patients continue to lose vision.

One explanation for this continued vision loss was the difficulty in diagnosing diabetic retinopathy.  Ophthalmologists have traditionally relied on retinal examination and photography for diagnosis, both of which lack the resolution to adequately measure microscopic changes taking place in the retina.  However, thanks to the recent development of an imaging technology called Optical Coherence Tomography (OCT), doctors have been able to visualize the sequence of diabetic retinal changes at a nearly cellular level.   This OCT imaging allows eye care providers to catch vision threatening retinopathy in earlier stages and monitor it more effectively than ever before.

 

Doctors have also updated their therapeutic armamentarium for dealing with diabetic retinopathy.  Traditional laser treatment causes irreversible burns of the retina, permanently decreasing vision in the area of the burn.  Newer therapies, however, are not destructive to the retina.  One such therapy involves the injection of medications into the eye that reduce retinal swelling and improve central vision.  One such medication, ranubizumab (Lucentis©), is FDA approved specifically for this purpose.  In FDA trials, this drug was shown to improve vision by greater than two lines on the eye chart in patients with swelling of their retina due to diabetic retinopathy.  Other medications, when used off-label, are thought to have similar effects on the retina as well.

Another novel, non-destructive therapy for diabetic retinopathy is MicroPulseTM laser, which uses shortened durations of treatment to stimulate the retina rather than burn it.  Early studies of this technology have demonstrated absence of retinal damage following laser treatment, although improvement in vision has yet to be proven in large clinical trials.

There is a revolution happening in the management of diabetic eye disease.  Thanks to recent advances in technology and treatment, the sobering verdict of diabetic retinopathy has changed.  No longer are patients confined to the certainty of vision loss, but instead have the possibility of better vision today and for years to come.

 

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