Figure 5-3.  Linear regression plot of number of lines of predicted improvement using laser interferometer (slope = 0.40, intercept = 2.96) and observed improvement after ciclosporin therapy (R = 0.53). Outer dotted lines represent 95% confidence limits. (From Palestine AG, Alter GJ, Chan CC, et al. Laser interferometry and visual prognosis in uveitis. Ophthalmology 1985; 92: 1567–9.)

three-line or better improvement in vision compared with the standard measurement of visual acuity (Fig. 5-3). In contrast, only 52% of the patients in whom laser interferometry showed less than a three-line improvement later showed improvement with ciclosporin therapy. There was a moderate correlation between the predicted number of lines of improvement with the laser interferometer and the number of lines actually improved with therapy (R = 0.59, p < 0.001). We therefore perform a laser interferometry visual acuity determination on all patients with uveitis having poor vision. If the laser interferometry acuity is better than the visual acuity measured on an ETDRS chart, we expect to see an improvement in visual acuity with therapy even in patients with cystoid macular edema.

Fluorescein angiography

Fluorescein angiography is an invaluable aid in evaluating the numerous changes in uveitic eyes. The alterations seen are variable and frequently require the observer to evaluate the angiogram for some time before a satisfactory interpretation is made. Some of the more frequently noted ocular changes that are highlighted with fluorescein angiography are listed in Box 5-3. Corresponding stereo photographs may be helpful in establishing the level at which the pathologic condition in the eye is occurring.

Macular edema is one of the major causes of reduced vision in many types of intraocular inflammatory disease. The cause of this is not absolutely known. We assume, logically, that it is due to a swelling of the retinal layers, which disrupts the intimate association of the retinal elements that results in crisp vision or distorts the alignment of the photoreceptors. However, we know that patients with angiographic evidence of mild or moderate macular edema can have good visual acuity. Further, we have been most struck

Ancillary ophthalmic tests

Box 5-3  Major fluorescein angiographic findings

in uveitis

Cystoid macular edema

Subretinal neovascular membranes

Disc leakage

Late staining of retinal vessels

Neovascularization of retinal vessels

Retinal vascular capillary dropout and reorganization

Retinal pigment epithelium perturbations

that patients can have an improvement of vision after therapeutic intervention, yet the fluorescein angiogram shows no change in the leakage of fluorescein. Because late leakage seen on angiography is not strongly correlated with a drop in vision, we explored other possible alterations that might be evaluated with fluorescein angiography. We hypothesized that retinal thickening and not the leakage of fluorescein into the retina was one of the major causes of the decrease in vision. We measured the amount of retinal thickening with the use of standard angiographic photos taken early in the angiogram (Fig. 5-4).39 We noted a strong correlation between retinal thickening and the visual acuity of these eyes (Figs 5-5 and 5-6). The amount of dye leakage in the late phase of the angiogram did not, however, correlate well with visual acuity. More recently, the OCT has been used to assess macular edema in patients with uveitis. Nevertheless, useful information about the vascular morphology and the presence of vasculitis can best be assessed by fluorescein angiography.

In reading the angiogram, it is important to look at the early frames to best visualize the microvasculature surrounding the fovea. To best enhance the stereo effect, we have found it useful to use a ‘map reader’. If one wishes to compare sequential fluorescein angiograms, the photos must be taken with the Allan separator always set at the same value. Differences in the separator settings can induce an artificial increase or decrease in the height of lesions noted when the photos are viewed with the stereo viewer.

Many inflammatory eye diseases are thought to be associated with abnormalities in choroidal blood flow. Unfortunately, the excitation and fluorescence of fluorescein dye are absorbed and scattered by the retinal pigment. In addition, fluorescein dye rapidly leaks from the fenestrated vessels of the choriocapillaris, leading to a diffuse background choroidal fluorescence. Both of these factors combine to obscure a detailed analysis of the choroidal blood flow with fluorescein angiography.

Indocyanine green

Indocyanine green (ICG) is a water-soluble tricarbocyanine dye that was first used to measure cardiac output.40 Unlike fluorescein, ICG is almost completely bound to plasma proteins and does not leak from normal retinal or choroidal vessels. Importantly, the pigment of the retinal pigment epithelium and neurosensory retina does not significantly block the choroidal fluorescence when ICG dye is illuminated with infrared light. ICG fluorescence is also more easily detected through hemorrhage. As a result, ICG angiography, which is recorded on either infrared photography or video angio­ graphy, is a useful tool for demonstrating abnormalities of

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