This post features a chat with Charlotte Dawson, who has been my go-to person for certain scientific aspects of my A Quiet Rebellion books. Charlotte is a Veterinary Ophthalmologist at the Royal Veterinary College in London, UK.
MH Thaung (Caroline): Charlotte, thanks for chatting with us today. Perhaps we can start off with you telling us a bit about yourself.
Charlotte: Hello. I graduated from the RVC in 2009. After a short period in private small animal practice I undertook two rotating internships (one in private practice and one at the RVC). I then continued with a residency and am now a lecturer at the RVC. I enjoy all aspects of life working at a university including the clinical activities, teaching and research. In my spare time I like spending time with my family, friends and traveling with my dog Frank.
Caroline: How did you become a Veterinary Ophthalmologist?
Charlotte: Well… that is a good question! As an undergraduate we had very little teaching about eye and so I started to read more about it (mainly because I was worried about not passing final exams!) Then when I was in my first job I started to realise that a lot of cases I saw as a GP were eyes. I started to do lots of CPD [Note from MH: Continuing Professional Development – activities to improve expertise after formal examinations are finished] and the interest sparked from there. I then wanted to just do eyes…. And chased the dream of becoming a specialist.
Caroline: What do you like most about it?
Charlotte: I love that in my specialty I get to see all species! From snakes to cows to cats etc. I also get to keep medical and surgical skills. Most veterinary specialities you have to choose between large animals and small animals and also between medical and surgical disciplines. Ophthalmology is one of the rare ones that keeps all these aspects.
Caroline: What’s the biggest challenge?
Charlotte: The biggest challenge… well that is a toughie, Caroline! Working at a university I have to juggle clinical work (with my patients) with teaching the undergraduates and also the trainees specialising in Ophthalmology, with research. I think this constant feeling of being pulled in so many directions is difficult, but on the other hand I wouldn’t have it any other way!
Here we moved on to why I consulted Charlotte…
Caroline: I’d better say here that my books have a fantasy setting, so they shouldn’t be taken as an accurate reflection of our own world. My characters have a theory that the dreaded “beasts”, which are carnivorous, can be differentiated from harmless animals by the colour that their eyes reflect in torchlight. When working up this theory, I discussed a plausible scientific basis for this with Charlotte. Charlotte, can you tell us about differences between animal eyes?
Charlotte: Certainly. One of the things that makes my subject so cool is that each species has some different “normal” variations in their eyes. Yet there are similarities also that make all eyes function to provide vision. For example think about us, we can have different coloured irises and we know that this is inherited from your parents. In other animals they too an have different colour irises — usually blue or brown, but in cats they are yellowy-green and in some birds and replies they can be orange and red! Also, the pupil shape can be different, for example dogs have a round pupil and cats have a slit pupil…. Some reptiles have three pupils! Horses and ruminants have a granular iridica (a bobbly bit on the upper edge of the pupil)… All these variations are thought to be adaptations to help with vision.
Caroline: And about my fantasy world?
Charlotte: The part that you asked for help from me was about the reflectivity of the back of the eye that you can see from animals and people in the dark or with a flash of a camera, for example. In people we do not have the structure that is reflective (the tapetum), we have a red reflection that is from the blood vessels in the back of the eye. In veterinary species animals that have a tapetum give a shiny reflection when a light is shone into their eyes. This was what first gave people the idea for “cats eye” in the road, the reflective lights in the centre of roads to distinguish one side from the other.
Caroline: My characters, being frightened of all mammals, were looking for some way of differentiating the really dangerous (carnivorous) ones from the not-quite-so-dangerous ones. They had an idea about eyes…
Charlotte: The colour that the tapetum reflects can be different in different individuals in the same species (although usually a just a few different colours) and between species too. So this is what led us to be able to distinguish between beasts in the dark!
Caroline: Yep, the anatomic location of the tapetum varies between species, as does its cellular composition and structure. In my fantasy world, the tapeta of different species (particularly carnivores vs the rest) reflect different colours because of this. Or so my characters hypothesise… We can see here some examples of real-world tapetal reflections that Charlotte has kindly provided from her photo collection. Thanks very much for this, Charlotte!