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Woman complains of gradual decrease in vision

Issue: June 10, 2014

ByJennifer Renz, MD

ByJay S. Duker, MD

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A 65-year-old woman complained of gradually decreasing vision over the last several years. She had been diagnosed with neovascular age-related macular degeneration and had received intravitreal ranibizumab every 5 to 6 weeks for the last 3 years bilaterally.

Her ocular history included a retinal tear in the left eye treated with laser retinopexy a year ago, bilateral posterior vitreous detachments, mild cataracts in both eyes and ocular hypertension. Her medical history was significant for breast cancer treated with a lumpectomy and radiation, as well as hypothyroidism. Her family history was noncontributory, and she was on latanoprost in both eyes, AREDS vitamins, anastrazole and levothyroxine. She had allergies to Flexeril (cyclobenzaprine), penicillin and sulfa, and her family history was negative.

Examination

The patient’s vision was 20/40 in both eyes, pupils were round and reactive to light without an afferent pupillary defect, and IOPs were normal in both eyes. The anterior segment exam was notable for mild cataracts. Dilated examination revealed multiple soft drusen in the macula of both eyes with turbid, yellowish subretinal material (Figure 1).

Optical coherence tomography demonstrated prominent drusen as well as fluid in the subretinal space (Figure 2). The retinal pigment epithelium (RPE) appeared intact, and there was no clear choroidal neovascular membrane visible. No sub-RPE or intraretinal fluid was apparent. On fluorescein angiography, the drusen appeared hyperfluorescent early and were far more numerous than on fundus exam. There was central pooling but no leakage, and there was some blockage (Figure 3). On fundus autofluorescence, many more drusen than initially evident clinically were again noted, represented by fine hypofluorescent lesions noted throughout the retina, with hyperfluorescence of the central subretinal material (Figure 4).

Figure 1. Fundus photographs showing bilateral macular drusen. Note lack of hemorrhage and scarring.

Images: Renz J, Duker JS

Figure 2. OCT demonstrating prominent drusen and apparent subretinal fluid.

Figure 3. Fluorescein angiography: Hyperfluorescent staining of drusen, pooling subfoveally but no leakage. Drusen more diffuse than seen on color fundus photos.

Figure 4. Fundus autofluorescence: Diffuse speckled hyperautofluorescence noted to a greater extent than seen with color photos. Such hyperautofluorescence is typical for pseudovitelliform lesions.

What is your diagnosis?

Drusen and pseudovitelliform lesion

There are multiple clinical entities that manifest either drusen or a vitelliform lesion; however, the differential diagnosis of drusen combined with a pseudovitelliform lesion is limited primarily to AMD, pattern dystrophy and basal laminar or cuticular drusen.

The density of bilateral drusen revealed on fluorescein angiography and fundus autofluorescence, the mild decrease in vision despite subretinal fluid, the relatively young age and lack of response to anti-VEGF intravitreal injections make typical wet AMD unlikely. Pattern dystrophy may have a variable presentation with drusen, retinal flecks or vitelliform macular lesions, but the prominent diffuse drusen in a “stars in the sky” pattern seen on autofluorescence and angiography in this patient is typically pathognomonic for basal laminar drusen.

Discussion

Basal laminar or cuticular drusen are small, innumerable, uniform, round yellow drusen that are more easily visualized with fluorescein angiography, particularly in the early AV phase, and autofluorescence than with biomicroscopy. The condition was first described by Gass in 1985, with the appearance of the drusen memorably described on angiography as having a “stars in the sky” or “Milky Way” pattern. Initially the drusen were thought to be distinct from those of AMD and represent nodular thickening of the basement membrane of the RPE. However, electron microscopy and immunohistochemistry by Russell et al in 2000 proved these drusen to be indistinguishable from those associated with AMD both in composition and location, in what Müller described in 1856 as the “cuticular layer” between the basal lamina of the RPE and Bruch’s membrane. For this reason, cuticular drusen may be a more accurate description than basal laminar drusen.

Basal laminar drusen are considered by some to be part of a spectrum including adult vitelliform degeneration, pattern dystrophy and AMD. Usually the prognosis is more benign than in AMD. Rarely, poor visual outcomes are associated with choroidal neovascularization and geographic atrophy. There is most likely a genetic association because the onset is typically earlier and bilateral and may be observed in asymptomatic family members. There have also been studies linking the phenotype to specific genetic mutations, such as the complement factor H gene. Although the etiology is not well understood, this association with a complement cascade mutation suggests involvement of this pathway. Current cigarette smoking and family history are also risk factors.

As in our patient, there can be an associated pseudovitelliform macular detachment, the appearance of which may simulate choroidal neovascularization. A pseudovitelliform detachment usually results in a mild to moderate drop in vision and spontaneously resolves in about half of all cases. Treatment of a pseudovitelliform lesion with photodynamic therapy has been shown to worsen vision. Treatment with laser, PDT or anti-VEGF is typically indicated only if choroidal neovascularization develops, which occurs in 4% to 21% of patients. There is no current treatment for geographic atrophy, which occurs in up to 11% of patients with basal laminar drusen.

Figure 5. OCT demonstrating resolution of subretinal fluid 1 year later.

Because there was no evidence of choroidal neovascularization and there had not been any response to intravitreal anti-VEGF therapy in our patient, her injections were stopped. One year later, the subretinal fluid had resolved on OCT (Figure 5), and her vision was 20/20 in both eyes.