Evaluation of cytologic specimens obtained during experimental vitreous biopsy

Vitreous specimens can be useful for diagnosis of intraocular infection, inflammation, and neoplasms. Concern has been raised that obtaining vitreous specimens through a guillotine cutter might result in suboptimal cytologic changes. To determine if aspiration yields better cytologic information than vitrectomy, the authors performed experimental vitreous biopsies on rabbit eyes with vitritis to compare specimens taken by aspiration or vitrectomy with cutting rates of 100, 300, 600 per minute. The specimens were processed by cytospin preparations and stained with Papanicolaou and May-Grünwald-Giemsa stain. There was no difference in the adequacy of the specimens. Cell loss or damage to cell morphologic features when obtaining specimens through aspiration or vitrectomy at different cutting rates could not be differentiated by a blinded cytologic evaluation. A theoretical model of shear stress on cells passing through a guillotine cutter was also developed. The experimental and theoretical data show that vitrectomy with a cutting rate as fast as 600 per minute yields an adequate specimens with a sufficient number of well preserved cells to make definite cytologic interpretations, and that vitreous aspiration is not necessary.