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Subclinical optic neuropathy in Fabry disease

Background: Fabry disease is a rare X-linked lysosomal storage disorder, caused by the deficiency of α-galactosidase A. Ophthalmic features comprise a cornea verticillata, conjunctival aneurysms, tortuous conjunctival and/or retinal vessels, and anterior and posterior subcapsular cataracts. The issue of a possible subclinical optic neuropathy in Fabry disease has been raised recently. In this pilot study, we looked for signs of optic neuropathy in our cohort of Fabry patients. Methods: Thirty-one Fabry patients (15 male, 16 female, mean age 34 years) underwent an ophthalmological investigation consisting of assessment of best corrected visual acuity, slit lamp investigation, testing of pupillary reaction, funduscopy, applanation tonometry, and automated perimetry (Humphrey 30-2). Twenty-nine patients received enzyme replacement therapy with agalsidase alpha (Replagal). Results: Twenty-five of thirty-one patients showed the typical cornea verticillata, tortuous vessels were seen in 17. Two patients exhibited the pathognomonic posterior subcapsular spoke-like (‘Fabry’) cataract. Intraocular pressure (IOP) was ≤ 20 mm Hg in all patients (mean IOP, range 10–20 mm Hg), and all had normal appearing discs on direct funduscopy. Ten out of 31 patients revealed pathological visual fields exhibiting relative central scotomas in automated 30° static perimetry. Conclusions: In the absence of any other plausible explanation responsible for the field defects detected, we found subclinical optic neuropathy in 10/31 patients suffering from Fabry disease. This figure is in line with a previous report and raises the question whether perimetry should become a part of the ophthalmological examination in Fabry patients. Remarkably, our patients did not complain about any visual impairment. Further investigations are needed to more precisely define this complication of Fabry disease.