Analysis of Internal Limiting Membranes of Secondary Macular Hole and Idiopatic Macular Hole by Time–of–Flight Secondary Ion Mass Spectrometer

Abstract

Abstract: : Purpose: To examine the substances in the internal limiting membranes (ILMs) of secondary macular hole and idiopatic macular hole with a Time–of–Flight Secondary Ion Mass spectrometer (TOF–SIMS), and to think about pathogenesis of the secondary macular hole. Methods: The ILMs were excised at viteous surgery from 1 patient with secondary macular hole, whose eye had history of epiretinal membrane formation and accepted vitrectomy, membrane peeling and photocoagulation for a iatrogenic tear near the macula 7 years ago, and from 4 patients with idiopatic macular hole. The eye of secondary macular hole had no cellophane maculopathy by the observation of ophthalmoscope and biomicroscope at the excision of ILM. The specimens were stored in liquid nitrogen. For TOF–SIMS examination the specimens were dried, and Zn, Cu, vitamins A and E, and fatty acids (palmitic acid, oleic acid and stearic acid), which are considered to exist in retinal pigment epithelial (RPE) cells, were measured with a TOF–SIMS. The number of specimens examined was 1 in the secondary macular hole and 4 in the idiopatic macular hole , and during the analysis, the large specimens were measured 2 or 3 times at different sites. A total of 3 sites in the secondary macular hole specimen and that of 9 sites in the all 4 idiopatic macular hole specimens were measured. Then the average ratio of each substance count / total substance count was calculated. Results: The average ratio of Zn ion count to the total count of spattered ions was significantly larger in the ILM of the secondary macular hole than in the ILM of idiopatic macular hole. The average ratio of vitamin E ion count to the total count of spattered ions was also significantly larger in the ILM of the secondary macular hole than in the ILM of idiopatic macular hole. The average ratios of oleic acid and stearic acid ion counts to the total count of spattered ions were also significantly larger in the ILM of the secondary macular hole than in the ILM of idiopatic macular hole. Conclusions: Results suggest that more RPE components exist in the ILM of the secondary macular hole than in the ILM of idiopatic macular hole, and that it is possible that the iatrogenic tear–derived RPEcells, although no apparent epiretinal membrane could be seen, induced the formation of macular hole.

Keywords: macular holes • pathology: human • pathology techniques