RETINA

The retina is a light-sensitive layer of tissue that lines the inside of the eye and sends visual messages through the optic nerve to the brain. There are several diseases that affect the retina, including:

Diabetic Retinopathy – it is caused by changes in the blood vessels in the retina from diabetes. Blood vessels may swell and leak fluid causing swelling and other problems. All people with diabetes are at risk for this disease, which is why everyone with diabetes should have a dilated eye exam every year. Good control of blood sugar levels can slow the onset and progression of this eye disease.

Age related macular degeneration – it causes damage to the macula, a small spot near the center of the retina and the part of the eye needed for sharp, central vision, which allows the ability to see objects that are straight ahead. By itself it does not lead to complete blindness, but it can cause the loss of central vision.

Macular hole – it is a small break in the macula of the retina. The size of the hole and its location determines how much vision will be affected. Some macular holes can seal themselves and require no treatment but surgery is necessary in many cases to help improve vision.

Epiretinal membrane (also known as Macular pucker) – it is scar tissue that forms on the macula caused by tugging on the retina from shrinking vitreous. As a part of the aging process, the vitreous separates from the retina; it can cause microscopic damage to the retina. As the retina heals, the resulting scar tissue can cause an epiretinal membrane.

Retinal detachment – it is when the retina is lifted or pulled from its normal position. A tear or break in the retina can allow fluid to get under the retina and separate it from the pigmented cell layer that nourishes the retina. Retinal diseases such as inflammatory disorders and trauma to the eye can cause a detachment. Traction from scar tissue can also cause the retina to become detached but this type is less common.

Vitreous

Most of the eye’s interior is filled with vitreous, a gel-like substance that helps the eye maintain a round shape. It is made up of 99% water and the remaining 1% is made up of collagen and hyaluronic acid, giving it a gelatinous consistency and optical clarity.

  • Vitreous detachment – There are millions of fine fibers intertwined within the vitreous that are attached to the surface of the retina. As we age, the vitreous slowly shrinks, and these fine fibers pull on the retina’s surface. Usually the fibers break, allowing the vitreous to separate and shrink away from the retina. This is a vitreous detachment. In most cases it is not sight threatening and requires no treatment.
  • Floaters – As the vitreous shrinks it becomes somewhat stringy and the strands can cast shadows on the retina that can be noticed as floaters. They may appear as little cobwebs, thread-like strands, squiggly lines, or specs that float in and out of the field of vision. Floaters can become more apparent when looking at something bright, such as white paper or the blue sky. Most people have floaters and learn to ignore them. However, a sudden increase in dark or black floaters, possibly accompanied by light flashes or peripheral (side) vision loss, could indicate a more serious problem. In this situation a dilated eye exam is recommended to ensure that treatment is not required.
  • Vitreous hemorrhage – The mechanisms of vitreous hemorrhage fall into three main categories: abnormal vessels that are prone to bleeding, normal vessels that rupture under stress, or extension of blood from an adjacent source.
  • Abnormal blood vessels are typically the result of abnormal blood vessel growth due to ischemia (inadequate supply of blood caused by partial or total blockage) in diseases such as diabetic retinopathy and retinal vein occlusion to name a couple. These newly formed vessels lack tight junctions which predispose them to spontaneous bleeding.
  • Normal vessels can rupture when sufficient mechanical force overcomes its structural integrity. This can occur from a vitreous detachment, trauma, or other rare conditions.
  • Blood from an adjacent source such as retinal macroaneurysm, tumors, and choroidal neovascularization. All can extend through the internal limiting membrane into the vitreous.

The symptoms of vitreous hemorrhage are varied but usually include painless floaters and/or visual loss that can range from mild to severe. Early or mild hemorrhage may be described as floaters, cobwebs, haze, shadows, or a red hue. More significant hemorrhages limit visual acuity, visual fields, or can cause scotomas.

Specialized tests such as ultrasonography can be used to check for the presence of a retinal detachment. Surgery and/or laser treatment can be performed to treat a retinal detachment or tears when indicated. Provided the retina is attached, observation is required and limitation of activities and elevation of the head may help the blood to settle inferiorly.