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Effects of air injection into the corneal stroma of man: an in vitro study.

BACKGROUND
Corneal stromal air injection has been described for assisting the deep dissection of the recipient corneal bed in lamellar grafting. The consistent finding of air entering the anterior chamber is considered an undesirable complication of the procedure. The route of air entry into the anterior chamber has not been investigated previously.


METHODS
The route of air passage through the cornea was studied in 10 human cadaver eyes by direct viewing of the inner corneal surface with an operating microscope and by electron microscopy.


RESULTS
Air entered the anterior chamber peripheral to Descemet's membrane in every case in the absence of pre-existing corneal pathology. The air expansion of the cornea occurred only along planes occupied by keratocytes and their cell processes and this expansion caused disruption of the keratocytes.


CONCLUSIONS
Air injection into the cornea caused bubbles to enter the anterior chamber peripheral to Schwalbe's line, through the trabecular meshwork. The air produced cleavage of the collagen lamellae along those planes occupied by keratocytes and their cell processes since this provides a path of least resistance. Disruption of the keratocytes is a direct mechanical effect. Descemet's membrane and Bowman's layer act as effective barriers to air passage in the normal cornea.