Carbon dioxide laser treatment of the conjunctiva and the cornea

Carbon dioxide (CO2) laser treatment was applied to the cornea and conjunctiva of 16 eyes from eight young pigs at power levels of 2.5 to 20.0 W, an exposure time of 0.1 seconds and different numbers of overlapping burns. Four animals were euthanatized at 30 minutes, one at 36 hours and three from 18 to 21 days after the treatment. Nitrous oxide (N2O) cryotherapy also was applied in a double freeze-thaw fashion to three of the eyes to compare the effects of the CO2 laser and cryotherapy at each of the time intervals. Epithelial destruction was achieved with CO2 laser power levels of 5.0 W and one or more superimposed burns. At 5.0 W, Bowman's membrane was destroyed while the conjunctival substantia propria protected the underlying sclera. The anterior chamber reaction was minimal and appeared to be less intense than with cryotherapy after 36 hours. At high energy levels (20.0 W), corneal and scleral perforation occurred. Furthermore, we have treated five human patients with the CO2 laser for bulbar conjunctival epithelial proliferative disorders. Minimal scarring occurred and local control of the disease was obtained in four patients. The CO2 laser may offer advantages over other modalities of treatment for bulbar conjunctival epithelial disorders. Its use is not recommended for lesions of the cornea and forniceal or palpebral conjunctiva.