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Why Close the Upper Puncta First? |
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– For many years we have advocated treating (closing) lower puncta first during punctual occlusion. In 1995 it became evident that the upper puncta should be treated first (supported by Doane, reported in the AAO in 1980). Treatment is determined by first placing dissolvable Collagen Plugs (Lacrimal Efficiency Test) into all four puncta.
After patients respond favorably to testing with dissolvable Collagen Plugs, the net question is whether to close the upper or lower puncta first with non-dissolvable plugs (Herrick Lacrimal Plugs). Traditionally, we have closed the lower puncta first because we believed “the lower puncta drained 60% or more of tears away from the eye”. It seemed logical to occlude the lower puncta first to get the maximum effect. However…
- Constant (basal) tears are produced mainly in the upper lids (Glands of Krause and Wolfring).
- Gravity helps tears to move down to the lid margin to form the tear meniscus. This wall of tears then coats the eye during each blink.
- Surface tension caused by the tear’s lipid layer helps coat the eye’s surface between blinks (not the tear meniscus).
– On the upper lid, the lid layer covering the surface of the tear meniscus functions like a tube, conducting tears across the lid’s margin, over to the punctum, where they prematurely drain away from the eye. This Krehbiel flow occurs during and between blinks. At the slit lamp, while the eyelids are held open and still, it is possible to observe flowing along the tear meniscus over to the punctum.
Negative pressure is created within the canaliculus during the blink mechanism, which draws tears away from the upper tear meniscus into the puncta before the eyelids can distribute them across the eye’s surface. Since the lacrimal excretory system is felt to be overly vigorous (10-15x), this vacuum can remove a majority of the volume of the tear meniscus.
Even when the central portion of the eye is well lubricated the medial parts of the eye may become dry because the upper punctum is interposed between most of the tear glands and the medial aspect of the eye’s surface. Chronic irritation and inflammation in dry parts of the eye may bring about the formation of medial pinguecula or pterygium. Also, the lateral parts of the eye may become dry because the vacuuming of the meniscus causes a medial shift of the tear volume across the upper lid, resulting in decreased lubrication and drying laterally.
They eye may respond to the localized dryness by lateral pinguecula formation or a lateral conjuctival inflammation reaction (so called episcleritis). When this lateral redness rapidly clears with lacrimal occlusion, it is then obvious that it is an exaggerated reaction of the body to localize Dry Eye Syndrome.
– The upper canaliculus should be occluded first to both increase the tear volume, and to develop a uniform distribution of tears on the Ocular Surface. Secondary watering of the eyes or epiphora will also be at a lower incidence when the upper lids are treated first.
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