YOU COULD SAY I’VE TAKEN the plunge, though normally I must say that I’d put my little toe in to test the water first. Or maybe it would be better to say I’ve bitten the bullet, though why one should want to bite a bullet I’m not sure!
For months I’ve been taking my glasses on and off to move between distance vision and reading. The problem, of course, is my developing nuclear sclerosis. The nucleus of the lens, you might remember, is what forms before birth with the cortex forming continually around it post-natally. And as time goes on the nucleus gets squeezed by this ever-encompassing mass of cortical lens fibres.
Every dog over 10-years-old has this change, giving the haze one classically sees through the pupil in older animals, though a look through the pupil with one’s direct ophthalmoscope shows that it isn’t a blinding cataract as the tapetal reflection is still visible.
In fact, for dogs, nuclear sclerosis seems to make little or no difference to their vision. But we depend on a flexible lens to be able to vary our optical focus from near to far and back again, to accommodate in optical parlance.
So my ageing eyes now need varifocals and have done for several months. And you might ask why I’ve not got on and visited my optician to sort this out. Generally over the years we’ve had a great relationship, talking about vision problems in dogs and cats and how they relate to the issues that he sees in people.
Short-sightedness is a big problem in people, of course, but not at all in dogs, or so you would think. When I give practical classes in ophthalmoscopy at the vet school we discuss using the direct ophthalmoscope to best advantage. There are some key features that must be grasped early on, I tell the students.
The first is that if all you see when looking into the eye with the ophthalmoscope is a bright light, then you’ve got it the wrong way round. They all laugh as that is a bit obvious! But I always think that there’s no harm in a bit of humour – if you laugh you’ll learn, to my mind.
But then the next key issue is that there are black and red numbers on the ophthalmoscope. The black numbers are positive dioptre lenses. We use zero to look at the retina, +10 to look at the lens and iris and +20 to look at the cornea and adnexa – it’s as simple as that.
But why then have red negative dioptre lenses? “To the retina and beyond,” I might say, though some of the students these days might be too young to remember Buzz Lightyear in Toy Story! A negative dioptre lens would take your focal plane into the retrobulbar space if the retina weren’t in the way.
But myopic individuals have an abnormally deep posterior segment to their eyes. This is where the negative dioptre comes into play to allow one to focus on the retina, further back than the zero setting on the ophthalmoscope.
It’s interesting to ask the vet students how many of them are myopic. The answer comes back at around 50%, certainly in Cambridge. They and I spent too much time under the bedclothes late at night reading just when our eyes were developing.
Our posterior sclera grew abnormally so that at rest our lenses focused light from close up onto our retinas. It’s a growing problem, particularly in the Far East where children are forced to read from a very young age. But surely not in dogs, I hear you cry!
I well remember my first myopic patient, a little Chinese crested dog which had been kept in a tea chest for the first year of its life. It had what is known as near field myopia quite as much as if it had been reading under the bedclothes late at night.
We gave it corrective contact lenses but in reality, although its new owners were concerned regarding its welfare, the dog seemed to have little in the way of behaviour problems so after a while its contact lenses were forgotten.
Several rescue greyhounds seem to be short-sighted too, as we can tell by refracting them just as my optician does for me. I surmise that these dogs too have been kept in small kennels in their early life, and they never seem to win races with the same regularity as do normally sighted dogs, hence perhaps why they end up in rescue kennels.
This, ladies and gentleman, I have to admit, has been a bit of a diversion from where I was heading, towards discussing the issue of ageing. I have to tell the students at the start of my lectures that if I veer off too dramatically on a tangent they should haul me back to the topic in hand.
And what I was going to confess before deviating onto myopic dogs was that I left sorting my varifocals out too long as it seemed to be the first sign that I am ageing. Somehow, when I look in the mirror each morning to shave, I should see my hair turning more and more grey and wrinkles developing. But these don’t have a functional impact and so can easily be forgotten. Not so my presbyopia, the failure of accommodation.
Don’t worry, be happy
But does it really matter? You’re only as old as you feel, or so they say, and at heart I feel I never really reached my teens. Life is quite as much fun now as I was when I was 12, or actually quite a bit more so. So as long as I keep doing my 10,000 steps each day and eating my five portions of fruit and vegetables, maybe I can put off worrying too much about getting older.
Incidentally, and perhaps ironically, Wikipedia tells me that “bite the bullet” was first used as a phrase by Rudyard Kipling in his 1891 novel The Light that Failed, a book that tells the life of Dick Heldar, a painter who goes blind.
“Bite the cartridge”, on the other hand, comes from the Indian Rebellion of 1857 or “chew the bullet” from 1796 where clenching a bullet or leather strap between one’s teeth was a way of coping with extreme pain during surgery in the days pre- anaesthetic. It goes on to talk of the Euthyphro dilemma in Plato’s dialogue between Socrates and Euthyphro, but I’m not sure we’ve any further space to cover that today. Thank goodness, I hear you cry!