Understanding the Retina: AMD and Exploratory Science

December 1st, 2017 by Dr. Chad Andrews

In medicine, innovative treatments don’t emerge out of thin air; they are the result of a series of advancements in our understanding of how genes, molecules, and cells interact.

The human eye is no stranger to this rule. In fact, there is still much we don’t understand about the genetic and cellular foundations of sight. But with contributions from Dr. Sarah McFarlane’s pathfinding research, scientists now have a clearer picture of how the retina functions, how its various cells interact, and how vision emerges out of these complex relations—as a result, new treatments are one step closer to impacting the lives of those living with vision loss.

You may have heard of photoreceptors, the light-sensing cells that are responsible for converting light into information that can be interpreted by our brains. Without photoreceptors, sight is impossible, and since many degenerative retinal diseases result in the gradual decay of these cells, there are many projects underway that seek to halt the death of photoreceptors, or to restore photoreceptors that have been lost.

Dr. McFarlane and her team recognize the importance of the eye’s light-sensing cells, but they also recognize the crucial role that the surrounding tissues and cells play in their maintenance. We don’t know enough about these cells, in particular the retinal pigment epithelial (RPE) cells that reside in a thin layer below the sheets of precious photoreceptors. RPE cells nourish and sustain the sheets of photoreceptors above them, which can’t do their complex work without sustenance and support. If the layer of cone and rod photoreceptors are the eye’s plant life, turning energy from the sun into oxygen, the RPE layer is the eye’s soil, fueling the plants and making photosynthesis possible.

Age-related macular degeneration (AMD) is one disease that entails the degeneration of the RPE cells, cascading in later stages into the loss of photoreceptors and eventually sight. A hurdle for current AMD research involves understanding how the RPE cells move; in particular, how we can transplant new RPE cells into damaged eyes while also ensuring that they reach the appropriate site of damage. To do this, we need to know more about how RPE cells migrate and interact with the rest of the eye.

A series of photoreceptor and RPE cross sections. The photoreceptors are the elongated shapes standing vertically at the top; the nourishing RPE cell layer is comprised of the grayish cells just below. The cross section on the far right shows damage to the RPE layer from AMD in the form of blood vessel swelling and seepage, which is beginning to move upward and affect the photoreceptors. A series of photoreceptor and RPE cross sections. The photoreceptors are the elongated shapes standing vertically at the top; the nourishing RPE cell layer is comprised of the grayish cells just below. The cross section on the far right shows damage to the RPE layer from AMD in the form of blood vessel swelling and seepage, which is beginning to move upward and affect the photoreceptors.

This is the crucial insight of Dr. McFarlane’s work: we need to develop our knowledge of RPE cells in healthy eyes before we can successfully transplant them into damaged ones. That’s the gap in current understanding.

Dr. McFarlane and her team made enormous strides in this area in 2017, and as a result we now have a better understanding of RPE migration and are closing the gap on safe and effective transplant therapies. These insights—as well as the therapies that will eventually emerge from them—will change the lives of individuals living with AMD and similar diseases.

But not without continued support from donors. There’s still work that needs to be done, still gaps in our understanding that need to be filled: your support can take Dr. McFarlane’s work to the finish line.