Abstract: BACKGROUND: Amniotic membrane transplantation has been used to treat chemical burns of the eyes at various stages. It promotes corneal epithelialization, reduces inflammation, and restores the integrity of the ocular surface, preventing thawing of the ocular tissue.
OBJECTIVE: To analyze the efficacy of amniotic membrane transplantation in ocular alkali chemical burns in the acute phase (7 days after injury) and in the repair phase (8-21 days) and to compare the effects of amniotic membrane transplantation in ocular alkali chemical burns with different degrees, in order to explore the optimal timing and mechanism of amniotic membrane transplantation for ocular alkali chemical burns.
METHODS: A retrospective analysis was performed in 47 cases (59 eyes) undergoing amniotic membrane transplantation for ocular alkali chemical burns in the General Hospital of Northern Theater Command, China from November 2015 to December 2021. There were 26 patients (35 eyes), 0.5 hours-7 days (including 7 days) after injury, in acute phase group and 21 patients (24 eyes), 8-21 days after injury, in repair period group. Of the 59 eyes, 39 eyes were grade II-III (moderate burns) and 20 eyes were grade IV-VI (severe burns). Patients from both groups underwent amniotic membrane transplantation the next day after admission. The corneal epithelial defect healing rate, vision, corneal clarity, degree of ocular surface inflammation, degree of corneal vascularization, and symblepharon were observed and recorded at preoperative and postoperative 3 weeks, 1 month, 2 months, and 3 months in the two groups. Statistical analyses were then performed.
RESULTS AND CONCLUSION: The acute phase group was superior to the repair period group in terms of average epithelial defect area, corneal epithelialization rate, average complete epithelial healing time, best corrected visual acuity at 3 months after operation, postoperative corneal transparency grading, incidence of symblepharon, degree of corneal vascularization, and success rate after operation (P < 0.05). By the end of the follow-up, the success rate of amniotic membrane transplantation was significantly higher in the moderate burn group than the severe burn group (P < 0.05). Most of the patients with failed amniotic membrane transplantation (65.2%) suffered from severe ocular alkali chemical burns, accompanied by a large area of limbal ischemia. The ocular surface could not be stabilized after repeated amniotic membrane transplantation, corneal conjunctivization appeared with central corneal neovascular infiltration and severe symblepharon, and visual acuity was reduced to manual. To conclude, the acute phase is the optimal timing to apply amniotic membrane transplantation for ocular alkali chemical burns. For patients with severe corneal epithelium defects who suffer from severe ocular alkali chemical burns, amniotic membrane transplantation needs to be performed multiple times in the early stage, thereby supporting wound repair. For patients with severe ocular alkali chemical burns who still have persistent epithelial defect after a series of amniotic membrane transplantation and have a tendency to dissolve the cornea and conjunctiva, amniotic membrane transplantation should be terminated, and permanent blepharoplasty or conjunctival flap masking should be used. After stabilization, second-phase ocular surface reconstruction should be conducted.

Key words: amniotic membrane transplantation, ocular alkali chemical burn, ocular surface rebuilding, acute stage, repair stage