Retinal Conditions

The retina is a nerve tissue located in the back of the eye that senses light and sends images to the brain. In the center of the retina is the macula, which provides central vision, allowing for the perception of fine detail.

The retina consists of several layers of interconnected neurons. Those that are directly sensitive to light are the photoreceptor cells, of which there are two types: rods and cones. Rods are in the outer regions of the retina and allow you to see in dim light and provide black-and-white vision (gray-scale). Cones reside primarily in the central portion of the retina and will enable you to perceive fine visual detail and color.

The images you see begin with the passing of light through the cornea and lens and onto the retina. This light striking the retina initiates chemical and electrical events that trigger nerve impulses. These impulses are sent through the optic nerve, a bundle of nerves that connects the eye to the visual centers of the brain. Of course, this all happens so fast that you are entirely unaware of it. All you know is what you experience as seeing. It’s all quite impressive!

Floaters are deposits of various sizes, shapes, consistencies, refractive indices, and motilities within the eye’s vitreous humour, which is usually transparent, as these objects exist within the eye itself and are not optical illusions. The standard type of floater, which is present in most people’s eyes, is due to degenerative changes of the vitreous humour.

Flashes, or photopsia, refer to the perception of flashes of light. Vitreous shrinkage causes a pull in vitreoretinal attachments, irritating the retina and causing it to discharge electrical impulses. The brain interprets these impulses as flashes of light.

Read more about flashes and floaters.

This is a medical emergency that, without prompt treatment, can result in permanent vision loss.

The retina can become separated from the layer underneath, at the back of the eye. Retinal diseases and trauma can cause detachment, or can happen spontaneously as a regular part of aging. Symptoms include flashes of light, an increase in the number of floaters, and worsening of the outer part of the visual field. This can be described as a curtain that covers part of the field of vision. In a minimal number of cases, both eyes are affected.

Read more about retinal detachment.

Branch retinal vein occlusion (BRVO) is a common retinal vascular disease of the elderly. It is caused by the occlusion of one of the branches of the central retinal vein. Waste produced by the retina is removed via the blood through the veins. When these blood vessels become occluded (blocked), fluids can build up, causing vision loss. Patients with BRVO typically experience a sudden onset of blurred vision or a central visual field defect.

Diabetic retinopathy, also known as diabetic eye disease, is a medical condition in which damage occurs to the retina due to diabetes and is a leading cause of blindness. High blood sugar levels can cause damage to blood vessels in the retina. The longer a person has diabetes, the higher his or her chances of developing diabetic retinopathy.

Read more about diabetic retinopathy.

Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a common eye condition and a leading cause of vision loss among people age 50 and older. AMD causes damage to the macula, a small spot near the center of the retina, which is the part of the eye responsible for sharp, central vision, allowing us to see objects that are straight ahead. Early on, there are often no symptoms. Over time, there may be a gradual worsening of vision that affects one or both eyes. While it does not result in complete blindness, loss of central vision can make it difficult to recognize faces, drive, read, or perform other daily activities.

Read more about macular degeneration.