Lacrimal drainage surgery in a patient with dry eyes.

The dry-eyed patient has both inadequate surface wetting, and a severe inability to clear the ocular surface of extrinsic debris, lid-margin bacteria (and their toxins), and the intrinsic inflammatory mediators secreted from the inflamed conjunctival surface. Tear evaporation compounds the problem of impaired production, this leading to significant concentration of inflammatory mediators on the abnormal ocular surface - this concentration being even greater where tear drainage is impaired. Nasolacrimal duct obstruction is, moreover, associated with a backwash of toxic debris from the lacrimal sac and, in the patient with dry eye, this backwash exacerbates an already compromised ocular surface. Surgery to re-establish tear drainage and eliminate the reservoir within the lacrimal sac may, therefore, improve the ocular status of patients with dry eye: many patients will benefit from external dacryocystorhinostomy, this being combined with retrograde canaliculostomy where there is proximal canalicular blockage. Secondary placement of a canalicular bypass tube may be required where these procedures have failed and tear drainage is needed. Where there is no risk of ocular surface toxicity due to complete stasis of the tear lake, the canaliculi can be ablated with thermal coagulation or canalicular excision. Rarely required as a primary procedure, dacryocystectomy may be used where dacryocystitis occurs in the presence of long-established canalicular occlusion.