HARRY really wasn’t happy.

I spied this normally gregarious Westie in the waiting room, sitting unusually quietly under the seat, hidden away beneath his owner’s legs.

Normally the wee rascal would have been attempting to cause carnage, in the nicest possible way.

He would have greeted every newcomer noisily, whined at every lack of attention and jumped up every time a consulting room door opened.

But not today.

Today Harry did not want to meet Sally.

His concerned owner plucked him up when I called his name and carried him to my table, where he stood miserable and sad, head held low, avoiding eye contact with me.

She said: "He’s just not been himself these last few days. He is hiding away under the bed and hardly comes out even to eat.’ He doesn’t want to go outside and normally he is desperate to chase the squirrels and bark at the cats next door and run about in the park.’ I think he must be seriously ill."

Her distress was obvious and she chattered away anxiously as I looked at him.

I knew Harry pretty well and this just was not him.

Even though it seemed very obvious what was wrong, it is important to run through the history and carry out a full examination to be sure.

And I was sure.

You only had to lift Harry’s head to see that he resented the light being in his eyes.

To be fair, his hair pattern mostly hid the crusting around them and the thick, green, gloopy yuck that filled them.

He tried dogfully to open them fully but he could not. They were too sore.

Seeing the discharge, his owner worried that he had a bacterial conjunctivitis, like her grand-daughter got, but it was far more serious than that.

Harry was affected by Keratoconjunctivitis sicca, which is commonly known as Dry Eye.

Tears are crucial to the comfort and well-being of the cornea, the front surface of the eye. They contain both a watery and a mucinous component and are responsible for lubricating, nutrifying and cleaning.

A deficiency in the watery part (usually caused by immune mediated destruction of the tear gland), will result in drying of the cornea with subsequent inflammation, pain, pigmentation and a typical green discharge that is often mistaken for infection. Left untreated, Dry Eye results in ongoing discomfort and pigmentation of the cornea, which reduces vision.

Any dog that appears to be suffering from recurrent eye infections should be checked, as the condition can be confirmed by carrying out a tear test, which takes only a minute and involves painlessly placing an absorbent strip into the corner of the eye.

Normal tear production values are around 20mm/minute, with levels below 10mm requiring urgent attention, lest more damage occurs. Treatment involves the use of ciclosporin drops (which are usually required lifelong) and, initially at least, artificial tear replacements and antibiotics.

We cleaned Harry up, clipped the hair from around his eyes to allow easier management and got him started on medication immediately. Pretty soon, he was back to his normal self.