Comparative Study Between Wide and Narrow Fenstrum Endoscopic DCR

The lacrimal sac and the nasolacrimal duct are contiguous structures . The part of the sac superior to the medial canthal tendon (MCT) is called the fundus, with its vertical length being 3-5 mm . The body of the sac, inferior to the MCT, is about 10 mm in length. The lacrimal sac fossa comprises of the anterior frontal process of the maxillary bone and the posterior lacrimal bone .

Lacrimal clearance relies on several factors, such as gravity, capillary attraction forces, evaporation, absorption by the conjunctival surface and the lacrimal "pump" which relies on the action of the orbicularis oculi muscle, particularly its deeper part (Horner's muscle). During the eye closing, the Horner's muscle contracts and the temporal four-fifths part of the canaliculus is pressed and closed, the nasal one-fifth part is pulled posteriorly and opens with shortening of the canalicular length. Therefore, the lacrimal fluid is effectively transported from temporal to nasal sides, finally reaching the lacrimal sac cavity. During the eye opening, as the Horner's muscle relaxes, the temporal four-fifths part of the canaliculus is expanded and the nasal one-fifth part is pressed and closed. The upper part of the lacrimal sac is directly affected by the Horner's muscle movement. During eye closing the sac expands temporally, during the eye opening the sac shrinks with an additional help of its elasticity.

The clinical evaluation of the lacrimal drainage system was originally outlined by Lester Jones. Evaluation was in the form of a dye disappearance test followed by a Jones I and Jones II test. The dye disappearance test (DDT) is useful for assessing the presence or absence of adequate lacrimal outflow, especially in unilateral cases. Using a drop of sterile 2% fluorescein solution or a moistened fluorescein strip, the examiner instills fluorescein into the conjunctival fornices of each eye and then observes the tear film.

Endoscopic DCR is a widely accepted treatment option for epiphora and dacryocystitis. endoscopic DCR has been widely performed as it has several advantages over external DCR including the absence of face scarring and better visualization via endoscopy. The purpose of DCR is to create a bypass, a rhinostoma, between the lacrimal sac and the nasal cavity.

Obstruction site in the lacrimal system is one of the characteristics contributing to a poor prognosis. False localization of the lacrimal sac and inadequate removal of the medial wall of the sac are the most common causes of failure . A systematic review showed that there was a trend towards improved outcomes and reduced granulation without increased complication rates in groups where nasal mucosal and lacrimal flaps were preserved. A study reviewing 100 failed DCR patients showed that inadequate osteotomy, incomplete sac marsupialization, and cicatricial closure of the ostium were the most common causes of failure.