by Dr. Bernhard Noelle, Chr.-Albrechts-Universität Kiel
To better understand the problems in the eye caused by systemic vasculitides (ocular vasculitis), it is important to know the anatomy of the eye's blood vessels. A model of the eye reveals that its structure is composed of three principal layers. The middle layer, the so-called "tunica vasculosa" is the vascular layer between the retina (the inner layer) and sclera (the stabilizing outer layer). The middle layer consists of the choroid, the ciliary body, and the iris. Numerous choroidal vessels supply the retinal pigment epithelium and the photoreceptors; the latter residing on the outer retinal layers and, having a high metabolic rate, are totally dependent on the choroidal vessels. The inner retinal layers, on the other hand, are supplied by their own blood vessels. Other important structures in the eye are avascular; these include the cornea, anterior chamber, lens, and vitreous body. Though lacking blood vessels, they can be susceptible to systemic vasculitides, as will be shown later on.
Vision itself is actually created in the brain. Images sensed in the eyes are converted to nerve impulses in a quick, albeit complicated, biophysical transformation. These impulses are carried along the optic nerves to the visual cortex, which makes up approximately one third of the cerebral cortex, and it is here that visual images are analyzed and processed. It is clear, therefore, that there could be many more places responsible for disturbances in vision than just the eyes.
This is generally the case with systemic vasculitides, where visual disturbances can be attributed to "central processing errors.".
In an example I will show how in the course of determining someone's field of vision, who had just become aware of growing "dark patches", that his field of vision had deteriorated in a matter of only a few weeks.
Since the narrowing of one's field of vision often takes place too slowly to notice , it is necessary to clinically measure the actual field of vision. Most of the eye's structures can be viewed directly with special optical equipment, the most important of which is the "Slit Lamp". This tool provides a biomicroscopic examination of the eyeball, thus revealing the structures' many fine details under high magnification. In this manner numerous blood vessels can be observed directly. This examination utilizes a strong light source and requires the temporary dilating of the pupils, which can be uncomfortable for the patients.
Inflammation in and around the eyes can be localized in the areas of the conjunctiva and episclera (vessels in the sclera). Episcleritis ("red-eye") often occurs with little or no pain and is caused by reddening of the episcleral vessels.
Episcleritis is often indicative of activity of the underlying illness in patients with systemic vasculitis. Scleritis (inflammation of the sclera) indicates a severe inflammation of the deeper portions of the sclera in addition to an episcleral inflammation. This inflammation is always associated with severe pain and can lead to other problems. [scleral staphyloma or thinning of the sclera].
Another manifestation of vasculitis is marginal keratitis. A curtain like, slight dimming of the outer cornea is visible, which is clearly distinguished from the central, clear cornea. This whitish dimming stems from protein deposition in the upper corneal layers. Marginal keratitis is quite common in patients with Wegener's Granulomatosis.
Ocular vasculitis can also manifest itself in the form of iritis, or inflammation of the iris. However, this occurs only rarely in systemic vasculitides. Another example is retinal vasculitis. When this inflammation of the retina develops, it is often isolated to a single vessel, but it can also be segmental or diffuse. Segmental retinal vasculitis is spot like and is a common characteristic of sarcoidosis. A total occlusion of a retinal vessel is often occurs following an outbreak of fulminating Behçet's Disease. In patients with panarteritis nodosa minute changes in the retinal vessels can be observed. In many cases this illness develops small aneurysms on the vessels
Because of the reduced blood supply and the resulting oxygen deficiency it can be necessary to have laser treatments. By placing multiple, spot cauterizations on the retina, this can reduce the dependency of oxygen-saturated blood in these areas, thus improving perfusion in the noncauterized area. Another example of retinal vasculitis can be found in periphlebitis (inflammation of the veins), which is characterized by a whitish covering of the retinal veins. This condition is not uncommon following an influenza infection. Included in the "portfolio" of retinal vasculitis one might also find ischemic optic neuropathy in patients with temporal arteritis. In this situation, insufficient perfusion to the large retinal arteries and/or the blood vessels of the optic nerves leads to an acute ischemia of the head of the optic nerves, which is indicated by a whitish dimming, swelling, and bleeding near the head of the optic disc.
Ocular vasculitis can also manifest itself in the form of choroidal vasculitis. This finding is, however, quite rare, possibly because the choroid has so many vessels, thus allowing for the possibility of collateral supply. We were able to examine a female patient with systemic lupus erythematosus. She presented with normal retinal vessel status in a fluorescein angiogram, but with a strong fluorescein leakage in the area of the retina underneath and close to the fovea (the area of highest visual acuity). Depending on the duration and scope of the changes the vision loss with this vasculitis can be large or insignificant.
In a normal ocular fundus one can see the so-called vital head of the optic nerve. The optic disc is round and clearly outlined in the retina and appears with a small, whitish central clearing (physiologic papillary excavation - normal ). Systemic vasculitides can cause partial or total fading of the optic nerves. If all of the optic nerve's fibers die out, then atrophy of the nerve will be evident, which can develop in a vasculitis or in orbital granulomas in Wegener's Granulomatosis. Granulomas on both sides of the eye socket can push the normal contents of the eye socket forward resulting in exopthalmos (protrusion of the eye, protopsis) and a swelling of the eyelid. This frightening symptom is observed increasingly less due to better and earlier diagnoses of systemic vasculitides.
Another problem in systemic vasculitides can originate in the areas of the nasal cavity and paranasal sinuses. Patients with Wegener's Granulomatosis and saddle-nose often present with an occlusion in the tear ducts. Granulomatosis-related changes in the nose area can lead to scarring and crusting, which can interfere with normal tear drainage.
Systemic vasculitides in the area of the eyes and cause numerous medical problems. These symptoms are not necessarily noticed by the patients themselves. Vasculitis patients are therefore advised to seek the care of an ophthalmologist.