How I investigate watering eyes

The most important thing when I investigate watering eyes is for me to find out whether the watering is worse in the morning or towards the end of the day. People who have patients blocked nasolacrimal ducts invariably either have watered all day long or worse in the morning. Those who have hypersecretion from irritated or dry eyes will have secondary watering towards the end of the day. I then want to know whether the watering is coming down on to the cheek from close to the nose or out of the corners of the eyes. If it is close to the nose, it is highly largely it is from the tear drainage system, and if it is out towards the outer part of the eyelids, then it may be because there is a wick syndrome from upper eyelid skin.
I carry out a fluorescein dye retention test and look to see how long it takes for the orange coloured fluorescein to disappear spontaneously from the surface of the eye and at the same time I observe the height of the tear meniscus. I also exclude any other pathology that could be causing secondary watering or hypersecretion. After, I will carry out syringing and probing. I may have to dilate up the punctum and do a small punctoplasty or canaliculoplasty to overcome any obstruction found and then syringe to make sure that the saline is getting through to the nose. I look in the nose with an endoscope to see whether the fluorescein has come down the duct into the nose along the normal tear route. I also try in establish with my nasal endoscopy whether there is enough room in the nose to do watering eye DCR surgery safely should that be required and exclude pathologies that can exist in the nose and cause watering. For instance, medical diseases such as sarcoidosis TB, tumour, severe rhinitis, polyps amongst others, can rarely cause a blocked tear duct.
When I am looking in the nose to investigate watering eyes, I am thinking how easy will it be to do this surgery? What access do I have? Can I do the surgery DCR entirely through the nose with an endoscope, called endonasal endoscopic DCR, or shall I do the surgery from the outside through an external route, just monitoring everything and partly contributing to the surgery endonasally?
Before I get that far, I may want to do some further radiological investigations. Nuclear medicine dacryoscintigraphy is often clinically indicated when there are watering eyes with patency on syringing and can show normal tear drainage from the instillation of Technetium-99m pertechnetate. If there is delayed passage of the tracer into the lacrimal sac and lacrimal duct, it indicates a functional destruction either from eyelid dysfunction or narrowing of the nasolacrimal duct. If the tracer is seen to accumulate in the lacrimal sac but not go down the lacrimal duct, then it can safely be assumed that the area of functional delay is at the level of lacrimal duct either at the top, the middle or down towards the bottom. Very occasionally I have to do a CT scan or da cryo cystogram injecting radiopaque material down the lacrimal drainage system. However, the latter is not physiological and will only outline a pathology or not show any function.
In summary, assessment of a patient with watering eyes involves taking a thorough history, observing where the tears fall from and further examination of the tear drainage system in the nose with possible lacrimal dacryoscintigraphy. From the accumulated answers from clinical examination and these tests, I can deduce where the blockage is and give the patient an indication of what surgery is going to be required and how likely the success is going to be.