After artificial tears, punctal occlusion with plugs is one of the most common forms of treatment for chronic dry eye. The most typical usage of plugs is in the lower two puncta, but some people have plugs in all four ducts (two lower, two upper).
All plugs are not equal! There are a great many types of plugs and for any given individual some may perform better than others, or be more comfortable, or last longer. In addition, the risks of plugs will vary depending on material and where they are inserted. See below for more information.
Punctal occlusion means blocking some or all of the puncta (small openings in the corners of the eyes near the nose, through which tears drain). This is done in order to improve the lubrication of the eye surface by slowing down tear drainage in people who are aqueous deficient (have low aqueous tear production.
Punctal occlusion is one of the most frequently used techniques for treating dry eye, after artificial tear supplements. The two general approaches to punctal occlusion are punctal plugs (small plugs inserted in the puncta or canalicula) or punctal cautery (surgical sealing of the puncta).
The eyes have four drains, called puncta, through which tears (which are constantly renewed) exit. These are in the lower and upper corners of the eyelids nearest the nose.
For patients whose dry eye symptoms are caused primarily by a deficiency in the water (aqueous) part of their tears, stopping the drains (called punctal occlusion) can sometimes help improve the symptoms. There are two ways to do this: using small plugs, or permanently sealing the openings with cautery. Plugs are far and away the most common of the two treatments. These include temporary collagen plugs, which dissolve by themselves, which can be placed in order to test the likelihood that silicone plugs or cautery will be helpful and will not result in tear overflow (epiphora).
Where are plugs placed in the eye?
Puncta are the drainage ducts that your old tears, or extra tears, can escape through while your glands are making new ones. In each of your eyes, there is one punctum in the top eyelid and another on the bottom eyelid, at the corner of the eye that is towards your nose.
Punctal plugs do exactly what they sound like: They stop the drains, just like the plug in your kitchen sink. They are not quite as easy to put in as the plug in your sink, and they are definitely not as easy to get out (at least, not the kind that go right now into the canalicula).
Will I get collagen plugs first?
Collagen plugs dissolve on their own, usually within a few days of insertion. They are a useful way to determine whether you might be a good candidate for permanent punctal plugs.
Some patients will experience tear overflow (epiphora) with punctal plugs. If they go straight to silicone plugs, then depending what type they get it may be difficult to remove them. Collagen plugs will not necessarily prove whether silicone plugs will be helpful, but they can help gauge patients who will have overflow or who simply are very unlikely to benefit.
Do plugs hurt?
Punctal plugs are sold with a long tweezer-y looking thing used to insert them. Now, how they are inserted depends partly on what kind of plug they are, for example, some fit right into the top of the punctum (and you can see the caps in the mirror) while others are shoved way down into the canaliculum. But broadly speaking, here is what will happen: Your eye doctor will put in some eyedrops to anaesthetise your eyes. The plug will then be placed into the puntum and stretched out a bit. Once it's ready, the optometrist pushes the plug into the punctum. In some cases your eye doctor may have to work with your punctum a little bit to get the plug in. It might be a little uncomfortable, but that's unusual.
What happens once the plugs are in?
After the anaesthetic wears off, you may be sore from the insertion process. Some people also have a reaction to the plugs that makes them feel uncomfortable - this may even last up to a few days. If this happens to you, please don't despair, don't claw at your eyes and unless it's intolerable don't encourage your eye doctor to remove them - chances are, the discomfort will pass and in a couple of days you'll feel much better. On the other hand, if you see swelling or have constant pain, by all means call your doctor.
A minority may find that their tears pool up and run over after the plugs are in. This is called epiphora. Some people experience significant enough benefits from the plugs that they tolerate the overflow as the price they pay for healthier and/or more comfortable eyes. Too much overflow can be either embarrassing or convenient, depending whether it's happening during a job interview or while your great aunt is telling you all about her latest hospitalisation. But chronic overflow may be unhealthy as well as inconvenient, so by all means keep your doctor up to date on what's going on.
Punctal plugs fall into one of two groups:
- Punctal (or punctum) plugs, which are placed at the tops of the puncta. The tops of these plugs are often visible to the patient looking carefully in a mirror. Generally speaking, the advantage of punctal plugs is ease of removal, with the accompanying disadvantage that they may more easily lost.
- Intracanalicular plugs, which are inserted into the canalicula. Most plugs of this type cannot be seen after insertion. They cannot be removed in the way punctal plugs can, though they may be flushed out with irrigation.
In practice often all types of plugs collectively are referred to as punctal plugs. Both types of plugs may cause some slight discomfort, especially when turning the head all the way to one side. If a punctal plug is too loose,
- "Temporary" plugs are usually made of collagen and are designed to last long enough to determine whether a patient can benefit from plugging.
- Extended duration temporary plugs are typically made of synthetics such as PCL.
- Punctal plugs are generally made of silicone.
- Intracanalicular plugs are now available made from several different materials. Silicone plugs remain popular, although there are thought to be some risks of them migrating in places they shouldn't go, particularly if there is an attempt to irrigate them out. Other options include plugs made of a thermodynamic acrylic polymer so that it can conform to the space it's in, and those made of a hydrogel (thought to carry lower risk if it has to be irrigated out).
For such a tiny bit of material there is a surprising range of shape designs for plugs, in terms of the shaft, cap (if punctal), and overall concept.
Some noteworthy innovative designs include:
- Plugs which change shape when warmed up to body temperature and become shorter/fatter to fill the space;
- Plugs which hydrate after insertion and expand to fill the space; and
- Plugs designed for people who experience overflow (epiphora) if full occluded
The range of sizes available for a given plug varies considerably. In general sizes range from 0.2mm diameter to over 1mm but the majority of plugs are avaiable in the 0.3 to 0.5 or 0.6 range.
The medical literature does not appear to support the idea that plugs can be expected to last permanently, and in fact many of the studies entirely fail to address plug loss rates (whether falling out the front or flushing through the other end). So, in terms of duration, plugs can be grouped as follows:
- Trial: Days; occasionally weeks: This would be the collagen plugs which are often used to determine whether someone would benefit from plugs at all.
- Short Term:: Weeks, maybe months: This is the increasingly popular synthetics / "absorbables" that are expected to last up to 3 months, or 3-6 months. This is maybe a good choice for people not enamoured of the risks of silicone plugs, or who aren't sure they need long-term plugs, or who have seasonal dryness, etc.
- Long Term: Being more expensive these should ideally last at least 6 months! This would include all the plugs where they don't say how long they last, or call them long-term.
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