Corneal copper deposition secondary to a variant of multiple myeloma: 30-year catamnesis.

tion of retinal fibers leads to myopia or myopia leads to myelination of retinal fibers. Alternatively, myopia and retinal myelination may be associated with other factors. Schmidt et al proposed that myelinated fibers could blur retinal images and induce visual deprivation. Such deprivation at a critical stage of ocular development could lead to axial elongation, akin to structural changes seen in eyes with a unilateral congenital cataract or severe ptosis. However, scotomas in myelinated retinas are generally smaller than predicted by the extent of myelination, suggesting that light penetrates to the photoreceptor layer despite the myelin interference. Furthermore, many cases of myelinated fibers do not show visual deficits or have significant myopia. It is also possible that the increased axial length of the eye predisposes to retinal myelination. If the process of lamina cribrosa development is prolonged, as could occur in axial myopia, myelination could continue down the optic nerve and into the retina. Although this theory has some merit, it cannot explain lesions discontinuous with the optic nerve head or myelination of eyes without increased axial lengths. It is likely that our patients were genetically predisposed to be hyperopic. During ocular development one eye became myelinated as a cause of, or resulting in, disruption of the preprogrammed growth pattern of that eye. The resultant axial elongation led to 10 D of anisometropia in the first case and more than 2 D in the second case. As a consequence, these patients developed amblyopia in their more ametropic eyes. Myelination did not cause organic loss of vision from macular dysfunction as reported in some of the patients of Hittner and Antoszyk. The question as to whether myelination causes myopia or vice versa is left unresolved, but our cases do suggest that anisometropia can be a more powerful influence on the relative visual acuity of each patient’s eyes than the presence of retinal myelin. Lempert has proposed smaller optic disc size as an organic as opposed to functional reason for decreased vision in hyperopic anisometropia. Although the optic discs of our patients appeared normal in each eye, we cannot exclude this as an alternative explanation for their decreased visual acuity. With an estimated amblyopia prevalence of 2% to 3%, much of which is anisometropic amblyopia, and a 0.9% prevalence of unilateral nerve fiber layer myelination, one would expect that the combination of these findings would be seen more frequently. We do not know why there have been no previous published reports about this finding, but do believe that these cases are unique in the literature on myelinated retinal nerve fibers.