Peripheral retina is the area in the retina that is not occupied by the macula. It is responsible for peripheral (side) and night vision.
The retina is divided into two parts; the central and the peripheral retina. The macula and fovea form the central retina. They occupy a tiny section and are responsible for the central, sharp vision. The peripheral retina holds about 95% of the retina. It provides peripheral vision.
The retina consists of photoreceptor cells (rods and cones) which absorb light and relay those signals to the brain through the optic nerve. The macula and fovea have the highest concentration of the cones. Rods are concentrated on the periphery of the retina and provide peripheral vision. There are approximately 120 million rods and 6 million cones.
Peripheral retina provides side vision. It enables individuals to see something out of the corner of the eye. However, peripheral vision cannot be used for driving, recognition and reading.
Associated symptoms & disorders
Some of the diseases affecting the peripheral retina or retina include:
- Eales disease affects the peripheral retina in young men, leading to inflammation, blocked retinal blood vessels, recurrent vitreal and retinal hemorrhage and abnormal growth of new blood vessels. It may lead to blurred vision.
- Diabetic retinopathy causes bleeding or fluid leakage in the retina leading to distorted vision. In the most advanced stages, new abnormal blood vessels grow in numbers on the retina’s surface. This action results in scarring and the loss of cells in the retina.
- Retinopathy of prematurity (ROP) occurs in a premature baby when unwanted blood vessels grow on its retina. The growths can lead to significant vision loss or blindness.
- Proliferative vitreoretinopathy (PVR) or complex retinal detachment occurs when retinal scar tissue forms. The tissue forms possibly due to a retinal detachment. It can lead to loss of peripheral vision.
- Usher syndrome is a genetic condition that causes loss of hearing and an eye disorder called retinitis pigmentosa (RP). RP is a group of eye problems affecting the retina. It alters how the retina responds to light leading to difficulties in vision.
- Shingles refers to a painful rash with open blisters caused by the herpes zoster virus. The virus can lie dormant for years but be activated due to advancing age or a weakened immune system.
- Marfan syndrome is hereditary and affects the body’s connective tissue. This tissue is responsible for holding all the parts of the body together. It also controls how the body grows. Individuals with Marfan syndrome suffer from myopia, astigmatism and ectopia lentis (dislocated lens).
- African River Blindness refers to an eye condition after an infection by the Onchocerca volvulus parasite. Before the onset of the disease, there may be itching and bumps on the skin.
- Photokeratitis occurs when the eye is exposed to ultraviolet rays. The rays may come from the sun or be man-made. The disease affects the cornea, conjunctiva and the eyelids.
- High blood pressure can damage the eye's arteries leading to a retinal artery occlusion (RAO), also called a stroke of the eye. There are two types of RAO; Branch retinal artery occlusion (BRAO) and central retinal artery occlusion (CRAO).
- Other conditions affecting the retina include a retinal tear, retinal detachment, ocular melanoma, retinoblastoma, etc.
Diagnosis of associated disorders
Because there are different diseases of the retina involved, the eye care professional may conduct various tests to diagnose a particular disease. These tests may include:
- A comprehensive eye examination which includes taking down a complete medical history. Patients are required to read from an eye chart to determine visual acuity.
- Indirect ophthalmoscope, a medical instrument the professional uses to examine the interior of the eye.
- Dynamic B-scan ultrasound where sound waves are used to create an image of the back of the eye during ocular movements.
- Fundus autofluorescence which enables images to be taken by a particular camera. Any damage to the retina will be revealed.
- Imaging tests such as magnetic resonance imaging and optical coherence tomography to reveal the inside of the retina.
- A slit-lamp examination in which the eye is dilated to enable the professional to see the inside of the eye using high magnification.
- Fluorescein angiography where a yellow dye is injected into a vein, usually on the arm. The professional will take pictures as the dye makes its way through the blood vessels.
Treatment of associated disorders
Some diseases such as ROP may disappear without treatment. The eye doctor will monitor the baby closely. Persistent ROP, however, is treated by an eye injection.
Doctors have not yet discovered a cure for Usher syndrome and retinitis pigmentosa. To manage the conditions, patients use low-vision devices and techniques to assist with vision. Taking vitamins, including vitamin A palmitate, can help with the symptoms.
Vascular endothelial growth factor (VEGF) causes the growth of abnormal blood vessels below the retina. To treat diseases associated with the retina such as diabetic retinopathy, Anti-VEGF drugs are used.
Antiretroviral therapy, Ganciclovir and other antiviral medications can treat conditions emanating from a weakened immune system.
Some conditions like Eales disease are treated through laser panretinal photocoagulation surgery. Vitrectomy (the surgical removal of the vitreous gel) is used to treat diabetic retinopathy and ROP.
Cancer treating therapies like chemotherapy, radiation, laser, cryotherapy, thermotherapy and enucleation (removal of the eyeball) can treat retinoblastoma.
To relieve Shingles patients of pain, rash, swellings and so on, specific eye drops may be used to fight infection and moisten the eye. Other medications can aid in reducing redness, pain and treat the virus. Placing a cool, moist compress over the eye can provide relief. The use of artificial tears, a cold compress, antibiotic eye drops and pain relievers can help with photokeratitis.
Anti-parasitic drugs can reduce the numbers of parasites in the body for African River Blindness.
Wearing sunglasses can assist with protection against ultraviolet rays for people with Stargardt disease. Further, special types of glasses and dilating eye drops can treat eye problems associated with Marfan syndrome.