IOWA RETINA CONSULTANTS
Basics of the Eye
Basic Eye Anatomy
The retina is a delicate sheet of tissue that lines the back of the eye. The macula is the central part of the retina and is responsible for sharp reading vision. The vitreous is a transparent gel that fills the space in front of the retina. These and other ocular structures are shown in the diagram below. The macula is not labeled but sits directly above the optic nerve in this picture. The "fovea centralis", as labeled below, also known as the fovea, is located in the center of the macula:
The retina functions much like film in a camera. It transforms light into electrical energy that it transmits to the brain. In the brain, these impulses are interpreted as visual images. The images below illustrate the similarities between the eye and a camera:
The photograph below shows the central portion of the retina, including the optic nerve (the yellowish circle on the right), some of the retinal blood vessels, and the macula (the central retina, between the blood vessels that arc above and below it. The fovea, in the very center of the macula, is the dark spot in the center of the photograph:
Diagnostic Tests
Fluorescein angiography allows us to visualize the retina in much greater detail. Fluorescein dye is injected into a vein in the arm, followed by a series of photographs of the eye. Fluorescein is very safe, even for dialysis patients. It is not the same dye used to study heart or kidneys. Inform the doctor, nurse or photographer if you have a known sensitivity to fluorescein or if you are pregnant. The dye will cause discoloration of your skin and urine for a few hours. Our digital angiography system allows us to review the results and discuss them with you immediately after the test is completed. Below is an image from a normal fluorescein angiogram. The circular structure to the left is the optic nerve, the retinal blood vessels are highlighted in white, and the dark area in the center is the fovea (the very center of the macula). The dark vertical line is a pointer that is used to guide the patient's eye during the angiogram:
We use ultrasound to visualize structures inside the eye that cannot be seen directly due to cataract (a cloudy lens) or bleeding in the eye. Below is an example of an ultrasound study performed on a normal eye:
We use optical coherence tomography (OCT) scanning to obtain microscopic cross-sectional views of the retina, aiding in diagnosis of certain diseases. You can think of OCT as a "sliver" of the central macula that is being viewed from the side. Below is an example of an OCT study performed on a normal eye. The labels indicate some of the layers of the retina, of which there are about ten in all:
All test results will be thoroughly explained to you and your family during your visit and are routinely sent along with our full report to your doctor.
Methods of Treatment
Disorders of retinal blood vessels, macular degeneration and diabetic retina problems, among other retinal diseases, may be treated in the office with laser (a beam of light that is focused on the retina with a lens) or injections of medication into the eye.
Tears in the retina may be repaired with laser or cryotherapy which involves placing a small freezing probe against the eye.
Retinal detachments can sometimes be repaired in the office using cryotherapy and injection of gas into the vitreous, known as pneumatic retinopexy. Surgery in an operating room, such as scleral buckling or vitrectomy, may be necessary for some retinal detachments and some other diseases. We will carefully review the options for treatment with you and your family as necessary.
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