Tearing in adults
There are many causes of watery eyes in adults and a useful way to summarise the main potential problems is as follows:
- 1. Conditions which cause increased tear production
- Anything which irritates the eye surface can lead to excess tears being made eg ingrowing eyelash, foreign body under upper lid, eyelid margin lump. Tear production is also often increased in allergy or infection. One of the commonest causes in this group is a condition known a Posterior Blepharitis, also known as Meibomian Gland Dysfuction. The function of the meibomian glands is to secrete an oily film onto the tears to reduce evaporation, and the gland orifices sit on the eyelid margin just behind the root of the eyelashes. Inflammation and blockage of the gland openings results in a less stable tear film which "breaks up" too quickly. Realising that the eye surface is wetting poorly the lacrimal gland produces more watery tears to try and improve lubrication. The excess tears can flood the drainage system leading to "compensatory" watering. To read more, including the treatment options, please look at the section on Blepharitis.
- 2. Eyelid Abnormalities
- The tears travel along the lower eyelid until they reach in the inner corner of the eye and exit through the upper and lower drainage holes (puncti). If the lid is lax it may fall away from the eye surface (see Ectropion) such that the lower punctum is no longer in contact with the globe and therefore cannot be accessed by the tears. The treatment for watering under these circumstances may be an eyelid operation to correct the malposition.
- Normal blinking is an important part of successful tear drainage. Eyelid closure results in the compression of the lacrimal tear sac. As the eyelids open the lacrimal sac expands causing the tears to be "sucked" into the lacrimal drainage system, this is known as the "lacrimal pump". Watery eyes are therefore often a problem in diseases which affect the ability to blink fully eg: facial weakness secondary to Bell's palsy (see Facial Weakness)
- 3. Conditions which reduce tear drainage
- Commonly watery eyes are due to reduced tears draining away from the eye into the nose. The "plumbing" problem may be anywhere in the lacrimal outflow apparatus. One of the easier causes to treat is a narrowing of the drainage holes - "punctal stenosis". These plug holes can often be widened using perforated punctal plugs which are usually inserted under anaesthetic drops. They are left in for a few months to stretch the drainage opening and are easy to remove in the out-patients.
Many people with watery eyes will have a narrowing or blockage further down-stream in the lacrimal system, most commonly at the lower end of the tube (naso-lacrimal duct) before it enters the nose. This is usually caused by chronic inflammation or infection and can be diagnosed during the consultation by syringing the system with a salt solution.
This is done with the patient lying down having had anaesthetic drops instilled into both eyes. A tiny cannula is inserted into the lower and then upper punctum and it is attempted to syringe saline down the drainage system. Using this technique it is possible to detect and locate any stenosis (narrowing) or occlusion (obstruction) in the outflow system. If present the best option to alleviate watering involves an operation to create a new artificial tear duct channel into the nose, the term for such a procedure is a Dacryocystorhinostomy (DCR).
Occasionally additional investigations, such as an X-ray of the tear drainage system, can be useful. There are two main ways to image the lacrimal system in order to detect narrowing, stones from infection or blockage:
- 1. Dacryocystography (DCG)
- This involves injecting a contrast medium into the lacrimal system and then taking a plain X-ray to determine whether the radiographic dye passes freely into the nose.
- 2. Lacrimal scintigraphy
- A drop of a radio-labelled tracer is instilled into the eye and the passage of the drop in the lacrimal apparatus is filmed to ascertain whether there is any "hold-up" in the system.