Tests for retinal diseases and uveitis
Special tests for retinal diseases and uveitis
Fundus photography:
Fundus photography permits documentation of the structures of the eye. This documentation may be important to compare with other investigations such as fluorescein angiography as well as for follow up. Fundus photography of the optic disc is important in the management of glaucoma.
Fundus fluorescein angiography (FFA):
This is an important test to evaluate a variety of retinal disease such as diabetic retinopathy. This is one of the commonest tests performed for retinal diseases. The test involves injecting a dye called sodium fluorescein into the blood stream and taking photographs of the retina using special filters. The test is important to stage the disease as well as to guide treatment with laser photocoagulation. Present generation digital cameras permit manipulation of the pictures and for instant viewing without need for development of the film etc.
Indocyanine angiography ( ICG):
Indocyanine angiography is similar to the fluorescein angiography but involves injection of a different dye called Indocyanine green. The test utilizes a special infrared sensitive camera to capture the images digitally. Very often indocyanine and fluorescein angiography are combined in a given patient to give maximum information. Indocyanine angiography gives more information regarding the choroidal vessels compared to fluorescein angiography that gives more information regarding the retinal blood vessels.
Electroretinography and Electrooculography:
These two tests are done to evaluate the function of the retina. Light is projected onto the retina and electrical potentials that occur normally in the eye are recorded using special electrodes placed near and on the eye. Certain retinal degenerative diseases are diagnosed only on testing with electroretinography. Specialized computer soft ware is needed to analyze the data.
Low vision aid testing:
There are certain diseases that may lead to permanent partial loss of vision. These patients can be sometimes helped to some extent by using special aids called low vision aids. There are a variety of these available and most of them are fine tuned for a specific function. Most of them have been made to enable reading fine print. It is important that the patient should be motivated to use them. They are used at a closer range than normal working distance and hence one needs to get used to the same. Computers and closed circuit television are also useful as low vision aids. One has to test different varieties before choosing what is appropriate for them.
Ultrasonography:
Ultrasonography is test that permits the evaluation of the back of the eye in case of opaque media. In a normal eye one is able to see the back of the eye using instruments such as indirect ophthalmoscope. In conditions of disease and injury the cornea, the lens or the vitreous cavity can become opaque and prevent this visualization. In these circumstances, ultrasound can be used to scan the eye and get useful information about the tissues lying behind the opaque media. This information is needed not only for proper diagnosis but also to plan the surgery where indicated.
