Eating carrots helps you see in the dark.
True! Carrots are full of vitamin A which is a precursor to an important chemical substance used by the light sensitive cells in the retina (the rods) for vision in low light / night time. If you are deficient in vitamin A, you can have problems with night vision.
One of my favourite past-times is baking sweet treats which are coeliac, diabetic and paleo friendly, and testing them out on the GJO team – thankfully most are met with resounding success! The reason I want to share these recipes with you is that Diabetes is a big enemy of healthy eyes and is frequently first diagnosed in adults when small changes are seen in the retinal blood vessels during a routine eye exam. There’s mounting evidence of the link between sugar consumption and diabetes across populations (Basu S et al, PLOS ONE 2013), so while we each have different tolerances, it makes sense to reduce sugar consumption. But thankfully your taste buds don’t have to miss out – give this recipe a try!
If you’ve been into my consultation room lately you’ll probably remember seeing my running event medals hanging in amongst my ‘wall of nerd’ framed academic certificates. I like to think that these medals make me appear to be a well rounded person, not just a nerd, but the truth is I’m quite a mediocre runner, a plodder, but I really enjoy it and I love the chance to finish an event where I’m rewarded with a medal. Pictured above are Paul and I with our spoils after the 14km Brisbane City2South in June this year, where Paul scored a massive PB (on his birthday!), and then had to wait another 18 minutes for me to finish! If you look closely at the ‘RUN’ sign, taken in Olympic Park in London on a visit in 2013, you’ll see examples of some terrible running form. The bottom right picture is the result of this recipe!
Paul and I are now training for the New York Marathon on 1st November 2015. The last time we trained for a marathon, two years ago, we were necking high sugar energy gels on our long runs, but neither of us tolerated them well. This time I was keen to find an alternative made from real food – my ‘running balls’ are an adaptation of a rum ball recipe I first tried at Christmas and can be made into the latter through the addition of 1 tbsp of rum – I used the delicious Bundaberg Royal Liquer (chocolate and coffee flavour) for mine. Roll them in dessicated coconut once you’ve formed them for extra Christmas cheer.
These running balls are gluten, grain and dairy free and low-ish in sugar. They’re packed full of good fats with the macadamia nuts and coconut oil for slow burn energy. If you’re more tolerant of sugar than me (which is probably most people), you’ll like them as a snack with your morning coffee. I munch on one of these before a long run and have another every 7-8km along the way, instead of the energy gels I used to eat. By the time I get to the third one, though, they’re getting pretty mushy in the Brisbane heat!
1 cup macadamia
1 cup pitted dates
2 cups shredded coconut
1 heaped tbsp cacao powder
50g melted coconut oil
Stevia to taste (I use 1-2 tbsp as the dates are sweet enough)
Throw everything into your food processor and process until well combined. Spoon out a dessert spoon sized volume of the mixture into your hands and form into tight balls with some decent squeeze pressure – you should make around 16. Pop into the fridge when you’re done.
These will get melty and soft if out of the fridge for longer than an hour, depending on the temperature, so could work as a morning tea lunchbox treat. I’m happy to report that they are teenager approved as well.
It was a sunny, slightly chilly Sunday morning at my parents’ place at Swanfels, outside of Warwick, when I decided to wander out to see what Dad was up to in his shed, and say hi to his two horses Kinsman and Pepper. Pepper can be a tetchy horse, and after I fell off him on Christmas Day 2006 my horse riding days have concluded, but on Sunday he was lapping up the attention I was giving him, enjoying the head and neck rubs and not wanting them to end. I spent quite a bit of time looking at his fascinating dark eyes, and wondered what he could see. So I asked Dr Google (veterinarian version).
It turns out that there’s quite a few scientific articles on horse vision, including one review comparing horse and human vision published in the International Journal of Zoology a few years ago.(1) Generally, a horse doesn’t see as well as we do in terms of clarity of vision but sees better than a dog or a cat. Pepper can’t focus well up close to see detail, but as he doesn’t read very much, this doesn’t matter to him. Horses have dichromatic vision, which means Pepper isn’t colour blind but only sees shades of blue and green, and cannot detect red, similar to the experience of some people with colour vision deficiency. Below is an image I found hilarious, from the website of the Equine Research foundation (www.equineresearch.org) of a horse undergoing colour vision testing. He’s doing it wrong! Hahaha!
A horse’s field of vision is designed to allow them to keep ‘half an eye’ on everything. If you could see around your whole head, you would have a field of vision of 360 degrees, and horses almost can. A human with normal vision will be able to see a field of vision of almost 180 degrees out to either side horizontally, with about 120 degrees of this being binocular, meaning we use two eyes and can better appreciate depth. By comparison, with its eyes set on the side of its head, a horse’s field of vision is about 350 degrees – most of this is monocular vision, meaning the right eye sees things on the horse’s right side and the same for the left eye. The horse only has about 65 degrees of binocular vision, which he will use to spot distant objects when his head is raised. When he holds his muzzle down and his head is vertical, he will have depth perception to see objects in front of him on the ground. Apparently pulling a horse’s head down as occurs in particular equestrian disciplines shortens his field of view even more to what’s right in front of him.
But despite this, the horse has hardly any blind spot, fitting its general characteristics as a ‘flight’ type of animal, being a herbivorous prey species in the wild.
The equine eye is the largest of any land mammal, being around 40mm (2) compared to the human average of around 24mm. I researched the size of an elephant eye just to check this claim, but it turns out their eyes are around 34mm long.(3) On my interesting travels down the Google rabbit hole (I know you’ve been there too!) I even read an article equating eye size in land mammals to their speed. Apparently the fastest runners in the animal kingdom generally have the biggest eyes when compared to their body size, improving sensitivity of vision which is helpful when you’re moving quickly through the environment. Even after adjusting for body size, researchers found that nearly 90% of the variation in eye size amongst mammals related to maximum running speed.(4) There’s even evidence that male horses have exhibited superior visuospatial ability compared to females, again likely linked to speed, and possibly contributing to the relative success of male over female horses at high levels of equestrian competition.(1)
We take for granted that humans will have variation in our visual ability from person to person. This is also the case for horses, and could influence their performance, especially in equine sports where assessing vision could predict how well a particular horse may perform. The horse has a unique relationship with the human, where two very different visual systems have to work together to control what is essentially one pattern of movement.(1)
So it turns out that my friend Pepper can’t see clarity, colour or close objects as well as me, but has bigger eyes and an almost 360 degree field of view. He also tolerates the chilly weather much better than me, so after an extended pat session I left him to his Sunday morning and headed inside for a cup of tea.
- Murphy J, Hall C, Arkins S. What horses and humans see: a comparative review. Int J of Zoology 2009, Article ID 721798.
- McMullen RJ, Gilger BC. Keratometry, biometry and prediction of intraocular lens power in the equine eye. Vet Ophthalmol 2006;9(5)357-60.
- Bapodra P, Bouts T, Mahoney P, Turner S, Silva-Fletcher A, Waters M. Ultrasonographic anatomy of the Asian elephant (Elephas maximus) eye. J Zoo Wildl Med 2010;41(3):409-17.
- Heard-Booth AN, Kirk EC. The influence of maxiumum running speed on eye size: a test of Leuckart’s Law in mammals. The Anat Record 2012;295:1053-62.
The world leaders are arriving in sunny Brisbane for G20 summit meetings across the river from our George Street optometry practice. As this is a once in a lifetime opportunity to be so close to arguably the best practice in the world, is there any reason for them not to take a break from G20 meetings and GJO their eyes? For a bit of fun, and in no particular order, we thought we would take a look at the leaders that represent the majority of the world and give them an eye makeover.