Potential Role of Computerized Visual Field Testing for the Appraisal and Follow-up of Birdshot Chorioretinopathy

Birdshot chorioretinopathy (BC) is a chronic intraocular inflammatory disease of unknown etiology, characterized by multiple deep-retinal creamy lesions scattered throughout the fundus up to the equator. Other features include vitreitis, vasculitis, cystoid macular edema, and optic disc swelling.¹ Evolution can be quite variable from case to case.^1,2 Therapeutic intervention usually consists of the concurrent administration of 2 immunosuppressive drugs, in most cases cyclosporine and corticosteroids.^1,2 Because of the severity and multiplicity of the side effects, the decision to treat depends on disease severity. The factors routinely used to evaluate disease severity are the clinical evaluation of inflammation, visual acuity, fluorescein angiography, and subjective visual disturbance. A factor that seems to have been neglected so far is visual field testing. The case reported herein indicates that computerized visual field testing seems to be an additional useful factor in the assessment of the severity of BC and in monitoring response to therapy.

A 43-year-old white man was examined for the first time for flickering and floaters in his right eye. Best-corrected visual acuity was 20/20 OU for near and far. Anterior chamber inflammation in the right eye was discovered subclinically, amounting to 5.2 photons per millisecond measured by laser flare photometry. There was a slight vitreitis in both eyes, and on fundus examination scattered punched-out creamy lesions were seen in both eyes compatible with BC, a diagnosis confirmed by the presence of the HLA-A29 antigen. Fluorescein angiographic findings showed all the classic signs of BC, such as papillitis, diffuse vasculitis, massive fluorescein impregnation of the retina, and a pseudodelay in retinal arteriovenous circulation time.³ Results of indocyanine green angiography (ICG) was also typical for BC, showing scattered dark dots at the intermediate and late angiographic phases, fuzzy choroidal vessels at the intermediate angiographic phase, and late zonal hyperfluorescence (Figure 1, A and C).⁴

The patient was not treated for 2½ years thereafter because his condition remained relatively stable. After 2 years, the patient complained of a decrease in visual performance despite having a visual acuity of 20/20 OU. Computerized visual fields (Octopus, program G1, Interzeag, Zurich, Switzerland) showed elevation of the mean defect (MD) (MD OD, 9.4 dB; MD OS, 5.1 dB) and of the loss variance (LV) (LV OD, 54 dB; LV OS, 23.5 dB) in both eyes, but more so in the right eye. Six months later, flickering in the right eye increased markedly, visual acuity decreased to 20/25 OD for far and 20/30 for near, and the visual field deteriorated further in both eyes (MD OD, 9.5 dB; MD OS, 6.1 dB; LV OD, 55 dB; and LV OS, 33.2 dB) (Figure 2, E). Laser flare photometry increased to 15.1 photons per millisecond OD and 5.1 photons per millisecond OS. Because of increased symptoms, decreased visual acuity, and marked disturbance of the visual fields, we initiated treatment consisting of oral prednisone, 1 mg/kg, and cyclosporine, 5 mg/kg. Five weeks after introduction of therapy, flickering in the right eye disappeared, visual acuity improved from 20/25 to 20/20 for far and from 20/30 to 20/25 for near, laser flare photometry diminished from 15.1 to 7.2 photons per millisecond, and indocyanine green angiographic signs improved (Figure 2, B and D) and remained stable thereafter. Visual fields improved bilaterally (MD OD, 9.5-3.5 dB; MD OS, 6.1-2.9 dB; LV OD, 55-16.5 dB; LV OS, 33.2-9.3 dB). Two and a half months later, the more severely affected right eye remained stable (visual acuity, 20/20; laser flare photometry, 7.2 photons per millisecond; visual field parameters: MD, 2.6 dB; and LV, 12.2 dB). On the left side, however, far vision decreased to 20/50 due to central serous chorioretinopathy (CSC) that had a typical angiographic aspect on both fluorescein and ICG angiography. Accordingly, the visual field worsened slightly in the left eye because of the scotoma related to CSC with a stable MD (2.7 dB) and a slight increase in LV (10.5 dB) (Figure 2, E). As CSC was attributed to the corticosteroid therapy, the use of corticosteroids was rapidly decreased and acetazolamide, 500 mg twice daily, was introduced. Cyclosporine also had to be discontinued because of intolerable side effects (systemic hypertension and an increase of >30% in the serum creatinine level). After discontinuation of corticosteroid therapy, visual acuity again improved to 20/30 OS. Evidence of CSC by fluorescein angiography was no longer seen, but persistent staining with ICG remained. The fact that computerized visual fields continued to improve despite decreasing visual acuity in the left eye indicated that the visual acuity drop was due not to the primary disease process, but to secondary CSC. Six months after discontinuation of therapy, MD again increased from 2.6 to 3.9 dB (OD) and from 2.7 to 4.8 dB (OS) (not shown on graph).

Visual field testing has been neglected so far in the appraisal of BC. This case shows that visual field alterations can indeed be very extensive while central visual acuity is preserved. It also seems as if the visual field deteriorates before other factors and is more sensitive for follow-up. The striking feature here was not only the pronounced deterioration of visual fields, but also their marked improvement during treatment. The involved physiopathological mechanism has to be investigated. From the pattern of visual field alteration it is impossible to say whether the involvement is retinal rather than at the level of the optic disc. Diffuse and massive retinal impregnation by fluorescein and electrophysiological findings point toward a retinal pathology.^3,5 Systematic computerized visual field testing in BC is probably warranted and will enable us to gather more data to evaluate its value as a follow-up factor. Another striking feature in this case was the occurrence of CSC, which was most likely due to the corticosteroid therapy.⁶

Corresponding author: Carl P. Herbort, MD, PhD, La Source Eye Center, 2 Avenue des Bergières, CH-1004 Lausanne, Switzerland.