eye DISEASE

Ancillary (additional) studies performed in our office are frequently necessary
1) to document the condition,
2) helpful for future comparisons to determine changes or progression,
3) to clarify the diagnosis,
4) to aid in determining treatment and
5) to assess the effect of treatment.

Visual fields (VF)--this test involves a patient, a computerized instrument (like a large globe split in half) and a technician. The alert patient, with chin on a chin-rest, looks steadily at small target light in the center of the globe, while the technician presents small lights of different size in the periphery (side vision). The patient, without deviating his sight from the target light, presses a button as soon as he/she sees the light in the peripheral vision. The value of visual field testing is to document possible defects due to retinal problems (tumors, vascular, degenerative), optic nerve damage (glaucoma, inflammation, demyelination, ischemia), and disease conditions in the brain (tumors, strokes etc).

Photography of ocular lesions is particularly helpful in documenting different lesions. It helps in various ways: allowing comparison at follow-up visits for potentially changing lesions --nevus, tumors, diabetic retinopathy, hemorrhages from vein occlusions, retinal swelling from arterial occlusion, optic nerve changes (edema, hemorrhages, glaucomatous cupping), retinal damage from trauma, etc.) Photography is also helpful in educating the patient as to his/her condition. The eye is the only part of the body (conjunctiva and retina) where blood vessels can be seen clearly, photographed and studied as they undergo change in various diseases.

Fundus fluorescein angiography (FFA) is a study of the retina and its blood vessels. It is possible because of sophisticated photographic developments and the discovery that fluorescein, a biologic dye, is a) safe and b) can be made to 'glow' in blood vessels if stimulated with a blue light, thus providing information about the 'health' of the circulation in the retina. It is performed as follows:
1) retina photographs are taken
2) 3 - 5 cc of fluorescein is injected in a vein in the arm
3) through a blue filter serial photographs are taken primarily of the eye
involved but also of the fellow eye either because it also is or may be
affected or for comparison with 'a normal'.
4) the film is developed, studied, and a report is made for the patient and, if
applicable, the referring doctor.
5) recommendation for treatment options are based on the test results and
incorporated in the report.
The side effects of fluorescein are a) a yellowing of the skin and urine for approximately 24 hours after injection, b) a +/- 5% mild allergic reaction (rash or nausea, very rarely accompanied by vomiting), especially in patients allergic to shellfish. Fluorescein angiography is of great value in patients with retinal conditions affecting the circulation and consequently the vision (diabetic retinopathy, vascular occlusions, macular degeneration, and tumors).

Indocyanine green angiography (ICG) employs a technique similar to fluorescein angiography, but utilizing a different biologic dye. It is much less commonly used than fluorescein. Its primary usefulness is in assessing vascular lesions in the choroid (the structure composed mostly of different sized blood vessels lying between the retina inside and the sclera outside), in particular abnormal vessels under the macula, when such lesions cannot be visualized by fluorescein angiography, because of overlying retinal hemorrhages, scarring, or other causes. In such cases it is helpful in directing appropriate treatment (different wavelength of laser, radiation, etc.).

Ultrasonography utilizes sound waves which penetrate opaque ocular tissue in the front part of the eye (corneal scar, cataract, vitreous hemorrhage) and help determine the condition of the more posterior ocular structures and the need for any treatment--surgical or medical. B-scan ultrasound provides a picture analogous to a 'slice' of the eyeball at various depths in differing slants. A-scan ultrasound is performed to determine the length of the eyeball. It is an important test before cataract surgery, because the power of the intraocular lens is dependent upon it.

Optical Coherence Tomography (OCT) is a test that provides extremely important information about a variety of retinal conditions. It allows a microscopic assessment of the retina-- the thickness of the retina secondary to leakage (edema), the thinness due to ischemia (insufficient circulation), the effect of treatment (whether laser, steroids or other modalities). The different retinal layers-- pigment epithelium layer,
the rods and cones layer, the inner layers of the retina and outer layer of the vitreous are all clearly displayed down to microns. Whereas photography provides an overall appearance of retinal/macular conditions (a panoramic map), and angiography supplies information about blood vessels primarily, OCT documents the effect of the underlying conditions on the retinal structures as well as the efficacy of treatment.

Electroretinography (ERG) provides information as to overall retinal function and a more specialized ERG (foveal ERG) is of value in assessing the macula. It is particularly important in degenerative conditions of the retina (retinitis pigmentosa, juvenile macular degeneration, toxic retinopathies associated with drugs such as Plaquenil, Chloroquine, Mellaril and related compounds, and others. A related test, electro-oculogram (OCG) is performed to in cases of another specific, macular degeneration, Best's Disease. ERGs and EOGs, though of great usefulness in diagnosis and extremely important for prognosis, are not widely available and for proper testing and interpretation, patients must be referred. The best center is the ERG Service at the Massachusetts Eye and Ear Infirmary.