How do I know if I have dry eye?

Almost nobody arrives saying "my tear film is unstable". They say their eyes feel gritty, like there is sand or an eyelash in there. That they burn or sting by late afternoon. That they water at the worst moments. That their contact lenses used to be comfortable all day and now are not. That their vision goes soft while reading and sharpens again when they blink hard.

Tired, heavy eyes at the end of a working day are on the list too, and are often put down to simply being tired. So is a pulling sensation or a feeling of pressure in or behind the eye, which surprises people when it turns out to be the lids.

Evaporative dry eye usually follows a shape through the day. Mornings can be fine, or can be the worst part if your lids do not fully close overnight. Symptoms build through the afternoon, and are worse after long screen sessions, in air conditioning, on a plane, or outdoors in wind and cold.

Symptoms that are constant and unchanging, or that came on suddenly, point somewhere else and are worth having looked at promptly.

The reason symptoms are not enough is that the same set of complaints can come from blocked oil glands, from lid margin inflammation, from allergy, or from a combination of all three — and each is treated differently. As part of a thorough eye examination, a screening called meibography images the glands in the lower lids. The optometrist reads those images alongside a slit lamp examination to judge what state the meibomian glands are in.

That is also what decides whether treatment is worth your money. If your glands are working and something else is driving the symptoms, light and heat are not the answer, and we would rather tell you that at the assessment than after a course.