Fixation of Ocular Tissues

I find that in ideal circumstances, it is best to fix the intact globe in 3% buffered glutaraldehyde for 12 hours, followed by 10% formalin for at least 24 hours, both at room temperature. Use of formalin alone tends to discolor the specimen, but, more importantly, it may cause artifactual retinal detachment in the intact eye during fixation. However, use of glutaraldehyde also has disadvantages (e.g., if immunohis-tochemistry is required), and this step can be omitted without major detrimental effect.

Do not inject fixative into the eye without thought of the consequences, as this can cause serious displacement of intraocular tissues. However, injection of 0.5 ml of 3% glutaraldehyde into the vitreous may be justified if

• there is likely to be a delayed autopsy (to prevent autolysis)

• the vitreous is essentially normal or is of little interest

• there is a particular interest in the pathology of the retina or macula

• only the posterior half of the eye is to be removed (see The Posterior Part of the Eye Only).

For larger specimens, such as the whole orbital contents with the globe, I advise fixation in 10% formalin. I find that orientation and pinning to a cork board before fixation (floating upside down) prevents distortion of the orbital anatomy. Specimens with the eye surrounded by bony orbit can be fixed intact before further dissection or partially dissected to aid fixation of the orbital contents (possibly changing the buffered formalin for optimal effect).

Eyes from patients with known or suspected spongiform encephalopathies (or high-risk cases) must be fixed using the formalin-formic acid or formalin/hypo-chlorite procedure20'21 before subsequent treatment for histology.

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