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A punctal plug, also known as tear duct plug or lacrimal plug, is a small medical device that is inserted into the tear duct (puncta) of an eye to block the duct. This prevents the drainage of liquid from the eye. They are used to treat dry eye. Artificial tears are usually still required after punctal plug insertion. [1]
A punctal plug may be inserted into the tear duct by an optometrist or ophthalmologist, decreasing the removal of natural tears from the affected eye. [8] The use of contact lenses may help prevent the abrasion during blinking lifting off the surface layer and uses thin lenses that are gas permeable to minimise reduced oxygenation.
VESA Enhanced Video Connector and VESA Plug and Display (a.k.a. M1-DA) both used this connector with slightly different pin assignments. These schemes combined VGA or digital video, audio, FireWire, and USB signals into a single connector. Deprecated. Made obsolete by DFP and later DVI. HDI-45: Apple proprietary.
OTG adds a fifth pin to the standard USB connector, called the ID-pin; the micro-A plug has the ID pin grounded, while the ID in the micro-B plug is floating. A device with a micro-A plug inserted becomes an OTG A-device, and a device with a micro-B plug inserted becomes a B-device. The type of plug inserted is detected by the state of the pin ID.
Tears are produced by the lacrimal gland, situated just outside the eye. Blinking the eyelids distributes the tears to keep the eyes moist, clean and lubricated. Excess tears are drained via the punctum through the tiny channels called canaliculi located on the inner side of the eyes into the tear sac, from there to the tear duct, the nose and finally down the throat.
The dimensions of modular connectors are such that a narrower plug can be inserted into a wider jack that has more positions than the plug, leaving the jack's outermost contacts unconnected. The height of the plug's insertion area is 0.260 inches (6.60 mm) and the contacts are 0.040 inches (1.02 mm) apart (contact pitch), so the width is ...
Involutional stenosis is probably the most common cause of nasolacrimal duct obstruction in older people. It affects women twice as frequently as men. Although the inciting event in this process is unknown, clinicopathologic study suggests that compression of the lumen of the nasolacrimal duct is caused by inflammatory infiltrates and edema.
Distribution of rods and cones along a line passing through the fovea and the blind spot of a human eye [1]. A blind spot, scotoma, is an obscuration of the visual field.A particular blind spot known as the physiological blind spot, "blind point", or punctum caecum in medical literature, is the place in the visual field that corresponds to the lack of light-detecting photoreceptor cells on the ...