Partial or total obstruction of blood flow in the eye can cause visual loss.  Its severity and duration depend on the site and degree of obstruction.  Retinal arteries, veins and capillaries, cause different visual symptoms when obstructed.  Venous obstruction is the most common.

Either the central outflow channel (central vein) or one of its branches may be blocked by a thrombus (clot).  The onset of symptoms may be insidious with loss of vision developing over several weeks, or more precipitous, over a few days.  The degree of blurring is related to the severity, duration, and location of vessel blockage. In addition to the routine eye examination which checks for vision and eye pressure, plus evaluation for cataracts and anatomic changes in the retina, special studies permit a much more precise evaluation of the changes occurring in the retina. Special diagnostic studies of the retina may help to identify the severity of obstruction, degree of visual loss, and possible contributing factors. This knowledge often gives helpful insight into possible treatment and/or indications for visual prognosis. Initially, observation of the obstruction is appropriate.  Laser treatment is resorted to only if poor vision persists and a treatable cause is identified in a branch obstruction or if glaucoma occurs as a consequence of a severe central vein obstruction. 

Arterial obstruction

Arterial obstruction creates a very different set of symptoms.  Abrupt onset of visual loss occurs, with the patient often being able to identify the moment of the obstruction.  The extent of the visual field loss depends on the branch of the retinal artery that is involved.  A patient with a suspected arterial occlusion should first have a general eye examination with a dilated pupil, in order to establish the diagnosis.  Until recently, remedies proposed to relieve an arterial occlusion have failed.  However, a new treatment was described, that was followed by a complete cure.  The possibility of treatment extends for no more than 4 hours after the occurrence of the arterial obstruction.  The patient should immediately be given a dose of neuroprotector medication, such as minocycline.  His pupil should be dilated and globe massage should be undertaken for an extended period, until the blood clot breaks up and is carried further upstream.  This treatment was said to be followed by a complete recovery.

Venous obstruction

Special Studies

In both venous and arterial obstruction, data from the Laser Doppler Flowmeter, invented and developed by Gilbert Feke, Ph.D., who is one of our research scientiest, give the world’s most accurate retinal blood flow information. This helps determine the severity of the blockage initially and permits to follow the clinical progress of its recovery or worsening. This allows earlier and more cogent plans for specific treatments should they be indicated.

Another group of studies determines the level of function of the retina by recording the micro electrical activity of the retinal cells. A lack of oxygen and other cell nutrients may stimulate the development of abnormal blood vessels in the eye that can lead to a blinding rapidly progressing glaucoma. Demonstration of this increased risk can be shown by abnormalities in the electroretinogram. If present, they warn the ophthalmologist to monitor the eye more closely. This minimizes the risk of glaucoma developing beyond the point where laser treatment and special eye drops can halt its progression.

Awareness of systemic medical problems often helps identify abnormalities related to retinal circulatory problems. In addition to hypertension and diabetes, the ophthalmologists at SRA Foundation also try to detect other systemic problems. The Laser Doppler has identified blood sludging problems. In one recent instance, the patient probably would have been blinded, stroked out, or dead if her treatment had not been drastically altered after the Laser Doppler identified her as having a markedly reduced retinal blood flow. Other blood flow studies had failed to give an indication of circulatory problems in the brain.

Once a retinal vascular obstruction has been diagnosed, your eye doctor should perform a thorough evaluation of the retinal status by routine and unique testing techniques. He should also be willing to monitor what may be a prolonged clinical course. Laser treatment may prove unnecessary since it often destroys part of the retina that are still functional.