Tip of the Month
Publishing date: June 2008
Tip Editors: Ann Hoste, John Salmon and John Thygesen
Tip reviewer: Roger Hitchings
The Science behind the Tip
The Science behind the Tip Manual nasolacrimal occlusion after eye drop instillation is often taught to glaucoma patients because of the belief that to do so will enhance the intraocular pressure (IOP) lowering effect and reduce systemic absorption of glaucoma medications. By impeding lacrimal drainage the contact time of the topical medication with the ocular surface will be prolonged and so ocular absorption and drug efficiency improved. A greater IOP lowering effect has been shown to occur when punctal plugs were placed in the inferior puncta(1,2) or when pressing on the medial canthus for 5 minutes with a fingertip(3-5).
However, from clinical evidence and from the lacrimal literature we know that tear drainage is dependent upon the blinking mechanism(3,6). During each blink the pretarsal orbicularis muscle contracts and tears are propelled through the canaliculi into the lacrimal sac. Avoiding orbicularis action will thus reduce lacrimal drainage. Teaching your patient to simply close both eyes and keep the eyelids still for 3 to 5 minutes, should have a similar effect as manual occlusion of the canaliculi(5).
Contributor: Veva De Groot, Antwerp
Co-editors: John Thygesen and Ann Hoste
Peer reviewers: Roger Hitchings and Anders Heijl
1. Huang TC and Lee DA. Punctal occlusion and topical medications for glaucoma. Am J Ophthalmol. 1989;107:151-5.
2. Aritürk N, Oge I, Erkan D, et al. The effects of nasolacrimal canal blockage on topical medications for glaucoma. Acta Ophthalmol Scand. 1996;74:411-3.
3. Jones LT. The lacrimal secretory system and its treatment. Am J Ophthalmol. 1966;62:47-52.
4. Kass MA, Meltzer DW, Gordon M, et al. Compliance with topical Pilocarpine treatment. Am J Ophtalmol. 1986;101:515-23.
5. Zimmerman TJ, Kooner KS, Kandarakis AS et al. Improving the therapeutic index of topically applied ocular drugs. Arch Ophthalmol. 1984;102:551-3.
6. Sahlin S and Chen E. Gravity, blink rate, and lacrimal drainage capacity. Am J Ophthalmol. 1997;124:758- 64.