Anatomy of the Retina
What is the Retina?
The retina is the light-sensitive tissue lining the back of the eye. The retina’s primary job is to convert light rays into impulses that travel through the optic nerve to our brain, to interpret the images we see.
What is the Vitreous?
The vitreous occupies approximately 80% of the volume of the eye and is a clear jelly-like substance that fills the posterior portion of the eye. It is located between the lens and the retina and is also referred to as the vitreous humor.
What is the Macula?
The macula is a part of the retina in the back of the eye that ensures clear and sharp central vision.
What is RPE?
RPE or retinal pigment epithelium is a very thin cell layer that nouri
shes retinal cells. This pigmented layer of cells serves as a pass-through channel between the light-sensitive photoreceptors of the retina and a layer of blood cells, called the choroid.
Epiretinal membrane (also commonly known as Macular Pucker or Cellophane Maculopathy) (abbreviated as ERM) is a thin sheet of fibrous tissue that can form on the surface of the retina causing a visual disturbance. This wrinkling of the retina can be caused by posterior vitreous detachment, traumatic ocular injury, retinal vein occlusion, ocular inflammation, or a retinal tear/detachment.
A macular hole is a small break in the macula which results in a loss of central vision.
A retinal detachment involves the separation of the retina from the back wall of the eye, which limits nutrient supply, resulting in a retina that is no longer able to function properly. This condition is severe a
nd should be treated immediately.
Age-Related Macular Degeneration
Generally speaking, age-related macular degeneration is when the macula, the part of the eye responsible for clear central (straight-ahead) vision, deteriorates. It is the most common cause of vision loss in the United States for people 50 or older. The chance of getting the disease increases with age. Macular degeneration varies widely in severity. For some people, the disease causes only slight distortion. In the worst cases, it can lead to a complete loss of central vision, making reading or driving impossible. There are two main types of age-related macular degeneration:
- Dry AMD
- The most common form, accounting for approximately 80-90% of individuals with AMD. It is characterized by the presence of drusen, which are small yellow deposits of waste products under the retina. In advanced stages, thinning and atrophy of the retina also occur. Vision impairment from Dry AMD can range from minimal to severe loss of central vision. If diagnosed early, steps can be taken to possibly slow the progression, such as taking vitamin and mineral supplements, eating healthy, and not smoking. Patients should discuss vitamin and mineral supplement treatment options with their doctor. Research is underway to identify other viable treatments for dry macular degeneration.
- Wet AMD
- This form is less common but can cause more rapid decline in vision. With this condition, new abnormal blood vessels grow under the retina. These fragile vessels can leak fluid and blood, which damages the macula. Good treatment options do exist, but the key is an early diagnosis to limit the amount of permanent damage. Treatment is based on the location and extent of the abnormal blood vessels. Anti-VEGF medications and laser surgery are commonly used.
Diabetic retinopathy is a complication of diabetes and is a leading cause of blindness in adults. This disease causes progressive damage to retinal blood vessels which results in poor blood flow and damage to the retina. Diabetic retinopathy can damage vision through many different mechanisms. Various treatments in the form of intravitreal injections, laser surgery, and vitrectomy surgery are used for treatment.
A retinal detachment involves the separation of the retina from the back wall of the eye cutting off nutrient supply, resulting in a retina that is no longer able to function properly. This condition is severe and should be treated immediately.
PVD/Flashes and floaters
A posterior vitreous detachment (PVD) is a natural change that occurs during adulthood when the vitreous gel that fills the eye separates from the retina. Most of the time this is a benign process, but a small percentage of the time it can cause a retinal tear and subsequent retinal detachment.
Floaters occur as a result of changes to the vitreous gel that typically
occur with aging. Vitreous debris or cells move within the eye casting shadows on the retina. These shadows appear as grey or black specs and strands that dart around in the vision with eye movement. They are often most visible when looking at a light colored background. Floaters are usually benign, but new floaters can sometimes indicate a problem such as a retinal tear or inflammation and warrant a dilated eye exam. If floaters are very severe surgery can be done to remove them, but this is usually not necessary if they are not bothersome.
Flashes of light typically occur as a result of vitreous tugging on the retina as it tries to separate itself during a posterior vitreous detachment. This pulling causes patients to see flashes of light or lightening streaks as the retina is stimulated. Flashes can sometimes indicate a problem such as a retinal tear or detachment and also warrant a dilated eye exam.
Uveitis is an inflammation that occurs inside the eye. If left untreated it can create scarring inside the eye that can be damaging to the vision. There are many different causes of uveitis. It is typically treated with steroids or other immune-suppressing medications via eye drops, injections, or pills.
Retinal Vein Occlusion
An occlusion is a blockage. When a retinal vein is blocked, it cannot drain blood from the retina. The result of this is poor blood flow which causes bleeding and leakage of fluid from the blood vessels. There are two main types of retinal vein occlusions: central retinal vein occlusion (CRVO), which is the blockage of the main retinal vein, and branch retinal vein occlusion (BRVO), which is a blockage of the smaller tributary veins. Both of these can cause vision loss through various mechanisms. One of the main causes of treatable vision loss is macular edema. Macular edema is typically treated with eye drops, injectable medications, or laser surgery.
Fluorescein Angiography (sometimes abbreviated FA or IVFA)
A fluorescein angiography test is used to evaluate the blood flow of the retina and is used in many different conditions to guide treatment. First, fluorescein dye is injected into a vein in the patient’s arm. As the dye circulates through the bloodstream and eventually to the eye, a camera takes photographs of the eye every few seconds for a few minutes. The photos help identify pigmentation changes, blood circulation patterns, and abnormal blood vessels.
Optical coherence tomography (OCT)
OCT is a non-invasive imaging method that uses light waves to provide detailed, cross-sectional images of the retina in distinctive layers. This technology has revolutionized the diagnosis and treatment of retinal conditions. OCT is very commonly used to monitor response to treatment in chronic conditions such as macular degeneration and diabetic eye disease.
B-scan is an ocular ultrasound used to evaluate structures within the eye and orbit. It provides a 2-dimensional view and can be used to take measurements. It is frequently used to diagnose and follow intraocular tumors or to detect a retinal detachment when the view inside the eye is obscured by hemorrhage or severe cataracts.
Photocoagulation (Laser Surgery)
Photocoagulation uses a high-energy laser beam to create small burns in the retina. This is used to treat many different conditions. In diabetic eye disease and retinal vein occlusions, it is used to cause regression in abnormal blood vessel formation or to seal off leaky blood vessels causing macular edema. It is also used to treat retinal tears and prevent them from becoming retinal detachments or to keep sub-clinical retinal detachments from increasing in size.
An intravitreal injection is a procedure used to place medication into the vitreous cavity inside the eye. This procedure takes place in an office setting and is used to treat a variety of retinal conditions. Topical anesthetic agents are used so that the procedure itself causes minimal to no discomfort.
Cryotherapy is a freezing therapy for the eye. Using a small metal probe on the outside of the eye the retina and other structures inside the eye can be treated without having to enter the eye or create an incision. It is used to treat a variety of conditions including retinal tears, detachments, tumors, or inflammatory disorders of the eye.
In this treatment, a photosensitizing medication is injected into the bloodstream. It travels to the eye and concentrates in the walls of abnormal blood vessels within or under the retina. A cold laser light is then focused on the desired areas to be treated, which activates the drug and leads to the closing off of these abnormal vessels without damaging normal vasculature. Photodynamic therapy is used to treat central serous retinopathy, vascular tumors, and certain types of macular degeneration.
Pars Plana Vitrectomy
Pars plana vitrectomy is a surgical procedure which removes the vitreous gel from the eye. This type of surgery is commonly performed using very small incisions the size of a small needle. Microsurgical instruments can then be introduced into the back of the eye to repair many different conditions. Common conditions treated with vitrectomy are retinal detachment, vitreous hemorrhage, epiretinal membrane, vitreous floaters, macular hole, and diabetic retinopathy. It is day surgery usually performed in an outpatient setting.
A scleral buckle is a surgical procedure used to repair a retinal detachment. It is performed by placing a small flexible band around the eye to relieve tractional forces being placed on the retina. This band is covered by the surface tissue of the eye and cannot be seen. It is day surgery usually performed in an outpatient setting.