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UV and the Eye

Image credit: Essilor Australia

Moderate exposure to ultraviolet radiation (UVR) from the sun is a necessary part of maintaining normal health (read the next blog for more about this!). However, excessive exposure to UVR has no health benefits and actually leads to adverse consequences for not only the skin, but also the eye. Interestingly, the eye occupies less than two percent of the whole body surface area, but it represents the ONLY organ system to allow the penetration of visible light deep into the human body.

So what are the known eye health effects of UVR?

Photokeratitis and photoconjunctivitis

Acute inflammation of the cornea (photokeratitis) and the conjunctiva (photoconjunctivitis) occur within a few hours of UVR exposure. These reactions can be likened to sunburn of the very sensitive tissues of the eyeball and eyelids. Photokeratitis and photoconjunctivitis are very painful conditions, but they are temporary reactions and do not seem to result in long-term damage to the eye or vision.

Pterygium

A pterygium is when the conjunctiva (clear membranous tissue covering the sclera or white part of the eye) becomes dysplastic and grows towards and over the cornea. Pterygium has been linked to prolonged UV exposure and is attributed to the accumulatively damaging effects of UVR. If the pterygium grows close to the pupil, it needs to be surgically removed otherwise, the eye will be blind. Pterygiums are found in 10% of Queenslanders (nearly half a million people!).

Cataracts

Cataracts are the leading cause of blindness in the world. The World Health Organisation estimates that up to 20% of cataracts may be caused by over-exposure to UVR. UVR is absorbed by the lens of the eye which leads to damage of the lens which may result in cataract formation. Cataract is when the lens of the eye becomes cloudy, making vision hazier and not completely correctable with glasses or contact lenses. Surgery is performed to remove the cloudy lens and replace it with a clear artificial lens.

Cancer of the eyelid

The eyelid region is one of the most common sites for non-melanoma skin cancers such as basal cell carcinoma and squamous cell carcinoma. Cancers of the eyelid account for 5 to 10% of all skin cancers of the human body. Like skin cancer of the rest of the human body, cancers of the eyelid are caused by the accumulative effects of UVR.

Age-related macular degeneration

Age-related macular degeneration is the leading cause of blindness in the western world. The retina is highly susceptible to photochemical damage from continuous exposure of light and oxygen. The cornea and lens block a major portion of UVR (see Figure 1) from reaching the retina. Although the relationship between UV light exposure and AMD is unclear, we know that short wavelength radiation (UV and even blue light from the visible spectrum) induce significant oxidative stress to the retina which may increase risk of the development of macular degeneration.

Check out our next blog to find out the best ways to protect our eyes from UV radiation!

References

Bergmanson, P.G., Sӧderber, P.G. The significance of ultraviolet radiation for eye diseases. A review with comments on the efficacy of UV-blocking contact lenses. Ophthalmic Phys Optics. 2002; 15(2): 83-91.
Cruickshanks, K.J., Klein, R., Klein, B.E. Sunlight and Age-Related Macular Degeneration: The Beaver Dam Eye Study. Arch Ophthalmol. 1993; 111(4):514-518.

By | 2018-06-28T07:03:01+00:00 28th October 2015|Eyesight and Health|0 Comments

Dissolving Cataracts

Cataracts are the leading cause of blindness worldwide. Currently, the only way to treat cataracts is to have them surgically removed. Cataract surgery is one of the most common surgeries performed in Australia. Imagine if cataracts could be treated without the need for surgical intervention.  What if surgery became a thing of the past and cataracts were treated with eye drops instead? Well this may sound like a bizarre plot in a science fiction movie, but scientists say it could well be our treatment modality in the near future.

The human lens is comprised of crystallin proteins which are assembled in a highly organised fashion essential for maintaining transparency and refractive power. The function of the lens is to transmit light and focus it on the retina. Disruption to the ordered structure of the lens proteins leads to unordered aggregation of proteins and subsequent formation of cataract.

cataracts clear eye websize

View of clear healthy lens through pupil.

cataracts cloudy eye websize

View of cataractous lens (yellow appearance) through pupil.

Researchers at the University of California, San Diego, have developed a topically applied treatment that has been shown to shrink and even dissolves cataracts. The new treatment has been researched and developed over many years and is based on the use of a naturally occurring steroid, lanosterol. Research has shown that lanosterol inhibits protein aggregation and cataract formation in rabbit and dog lenses in vivo. This is a very exciting technological development in potential cataract treatments because although surgery to remove cataracts is efficacious and safe, ageing populations around the world are predicted to require a two-fold increase in cataract surgery in the next 20 years. This would mean a significant impact on our public health system which is already struggling to cope with long waiting lists for cataract surgery.

It is very easy to screen for cataracts non-invasively with your general eye examination and as the eye is easily accessible for topical application of drugs, a pharmacological treatment for cataract is a promising thought for the future!

 

References

Pascolini, D. & Mariotti, S. P. Global estimates of visual impairment: 2010. Br. J. Ophthalmol.96, 614–618 (2012)

Zhao, L., Chen, X., Jin, X., Lin, D., Wen, C., Abagyan, R., Su, Z., Gao, W., Kozak, I., Granet, D., Yan, Y., Zhang, K., Wu, F., Chung, C., Zhu, J., Xi, Y., Flagg, K., Wang, Y., Tjondro, H. Lanosterol reverses protein aggregation in cataracts: 2015. Nature. 523, 607-611.

 

By | 2018-06-28T07:03:01+00:00 14th October 2015|Eye conditions, Uncategorized|2 Comments

Paul’s experience adapting to progressive glasses

I started working in optometry practice as a 16 year old edging lenses to fit frames, and found myself needing glasses a year later. My first pair of glasses were standard single vision glass photochromic that darkened in the sun, which looking back over nearly thirty years reveals how far lens designs have developed. The same type of sun darkening lenses are available in lighter and safer plastic with far more options available to make the lenses thinner, scratch resistant, and anti-reflective.

Continued technological development, however, is most noticeable when considering progressive lenses that provide correction for distance and near in the same pair of glasses, without the visible line that is seen with bifocal lenses. Thirty years ago I had enough focussing power in my eyes to not need near correction. Going on to qualify as an optometrist I always knew this wouldn’t last, and true to form, when I reached the grand age of 44 my arms started to become too short!

Having been involved in and around optometry practice for my entire working life, and listened to various patient complaints about adapting to progressive lenses, the inevitability for needing progressive glasses for myself was something I dreaded. The arrival of this least anticipated day was announced by Katie who having unpacked the order was excited to see what my new glasses looked like, so I put them on to oblige, fully expecting to whip them off immediately to revert back to my trusty single vision glasses. But wait, I thought, I can actually see with these! What’s all the fuss about!

My next first person lesson in progressive lenses was delivered two years later when I required stronger reading power at the bottom of the lenses. Now I could notice the blur when I moved my head around, that I had heard countless patients tell me about. My previous ‘first’ progressives were pretty mild in strength, and I know from my optics training that higher near add powers bring with them bigger distortions. But I had also been trained to advise patients that given a few days of adaption the distortions will largely disappear. Now I was experiencing this for myself I failed to see how this would work!

True to form my vision did settle down and over a period of 3-4 days I found things less distorted and now a few weeks on fail to notice the distortions at all, and only notice blur when I look into the distance through the near vision part at the bottom of the lens (when lifting my chin right up), which is supposed to happen. My new lenses were designed to give me a wider field of intermediate distance vision to help me see my two computer screens without moving my head too much, which they do so I’m glad I stuck with it for a few days to let them settle in.

Progressive lenses – the main points:

  • The latest evolution of progressive lens design means that lenses are custom made for the individual to suit their viewing requirements.
    • Previous to this designs were developed for specific tasks so the most appropriate design was selected based on the user’s requirements.
    • Go back some more and it was a choice between hard (wide field of view but heavy distortions) or soft (narrow field of view but milder distortions) designs.
  • The older types of progressive lenses are still available and often sold with the same description as the newer designs but at reduced prices – as with most things in life, you get what you pay for.
  • Newer designs can be tailored towards the tasks you do most. In my case this is for computer use where I need a wide intermediate corridor to take in my two screens, but for others this might be biased towards closework or distance vision for driving.
  • As I found first hand, progressive lenses can feel really odd to start with, particularly as the near addition power increases, but in most cases people adapt within a few days.
    • But, this should only take a few days and if they still feel odd after three to four days you should return to your optometrist for advice.
By | 2018-06-28T07:03:01+00:00 7th October 2015|Glasses|0 Comments

Hormones and Dry Eye

Dry eye is a very common problem, affecting people of all ages, gender and occupations. The symptoms of dry eye include red, itchy, stingy, gritty/sandy and watery eyes. These symptoms are often exacerbated by wind, air conditioning and computer use. Research shows however that dry eye is more prevalent in contact lens wearers, females and as we get older. So why are females more affected than males? The simple answer is hormones.

Karen came to see me a month ago about her red, irritated and watery eyes which had been annoying her over the past few weeks. Karen reported using lubricating eye drops every now and then but found that the drops were only effective for 15-20mins before her eyes would be irritated again. Karen had recently celebrated her 52nd birthday and currently wears glasses for reading and the computer. I asked Karen about her general health and she reported starting hormone replacement therapy medication for menopausal symptoms approximately two months ago. During our consultation, Karen and I discussed hormonal changes and how this can affect our eyes. Karen had never thought that her eye symptoms might be related to her hormonal symptoms!

Research has found that 60 percent of menopausal women are affected by dry eye but only 16 percent of these women realise that their hormones are to blame. For women affected by dry eye symptoms due to hormonal changes, using normal lubricating drops every now and then is unlikely to provide them with much relief; it is like putting a band aid on an abscess – it kind of works for a bit but is not really addressing the real problem.

So how does a change in hormones bring about a change in the eye? Research shows that plummeting hormones levels affect the ocular tissues and the composition of tears. Androgens, or sex hormones including both testosterone and estrogen can influence tear production. As we age, our androgen levels naturally decrease. As women start out with less androgens to begin with, a dramatic decrease in hormones during menopause and then continued reduction with increased age, androgen levels may fall below the amount needed for optimum eye health leading to the onset of dry eye. So if a lack of hormones is responsible for dry eye, one should be able to replace these hormones through medication (ie HRT) and alleviate the symptoms, right? Wrong. The Women’s Health Initiative study of over 25 000 women found an increased risk of dry eye in women using HRT. The role of HRT in menopausal women is unclear as some researchers support the idea that medication improves both quality and quantity of tears, whereas others have shown that it increased the incidence of dry eye.

So what did I suggest for Karen? I prescribed consistent use of lubricating eye drops to help alleviate symptoms and recommended changes in diet to help encourage quality tear production so that at least the tears that are produced are of good quality. Karen has been doing well for the past month now using this treatment regime to manage her dry eye.

Keep a look out for a future blog post on nutrition tips for healthy eyes.

References

Sullivan DA, Yamagami H, Liu M, et al. Sex steroids, the meibomian gland and evaporative dry eye. Adv Exp Med Biol 2002;506A:389-99.

Schaumberg DA. Hormone replacement therapy and dry eye syndrome. JAMA 2001;286:2114.

By | 2018-06-28T07:03:01+00:00 1st October 2015|Eyesight and Health|0 Comments

Surprising health conditions that optometrists find first!

They say that the eyes are the window to your soul, but did you know they are also a window to your overall health?  Signs of many health conditions including those associated with an increased risk of heart disease and stroke can be seen with an eye exam. The retina, or the back of your eye, is the only place in your body where your blood vessels and nerves can be seen without needing to cut you open! This makes regular eye examinations essential in detecting important medical issues in their very early stages! Some of the health conditions that can be detected during an eye exam include:

  • Cancer
  • Diabetes
  • High blood pressure
  • High cholesterol
  • Multiple sclerosis
  • Rheumatoid arthritis

Cancer

An eye exam may just save your life in this case! Everything from brain tumours to metastases in the eye from breast and lung cancers to leukaemia can be detected by an eye test. Patients will often be unaware of the cancer unless it is affecting their centre of vision, otherwise it may go undetected for a critical period of time which will likely influence the overall prognosis.

Diabetes

One of the very first signs of Type 2 Diabetes (before any symptoms have arisen!) is small amounts of bleeding in the retina.1 This is a sign of diabetic retinopathy, one of the most leading causes of vision loss in people with diabetes. If left untreated, blindness can result, however the outcome is greatly improved if the condition is caught early and successfully managed. When diabetic retinopathy is detected in the early stages, lifestyle changes such as weight management, exercise and diet control can prevent further damage to the eye and subsequently, vision.

High blood pressure

High blood pressure often causes weakening and narrowing of the arteries, characteristic changes that can be seen by an optometrist during your eye exam. Multiple studies2,3 have found a strong association between heart disease and narrowing of the retinal blood vessels, which adds further credence to the importance of regular routine eye exams.

Multiple sclerosis

Optic neuritis (inflammation of the optic nerve) can be a harbinger of MS which is a degenerative disease of the nervous system (it can also be the result of an infection or other causes too).4 Optic neuritis occurs in 75 percent of people with MS and is the first sign of the disease in up to 25 percent of cases.

Rheumatoid arthritis

Approximately one quarter of all people with rheumatoid arthritis have problems with their eyes – dry eye being to most common issue.5 Rheumatoid arthritis is an inflammatory disease with autoimmune links that affects the small joints of in the hands and feet. Dry eye is often associated with rheumatoid arthritis.

 

Most people don’t realize that by visiting their optometrist for an eye examination, and importantly, having their ocular health assessed, signs of many health conditions can detected. Once detected, these health conditions can then be actively treated and managed to ensure better prognosis and overall outcome for the patient.

 

References

[1] Lorenzi M, Gerhardinger C. Early cellular and molecular changes induced by diabetes in the retina. Diabetologia. 2001; 44:791-804.
[2] Witt N, Wong TY, Hughes AD, Chaturvedi N, Klein BE, Evans R, McNamara M, Thom SA, Klein R. Abnormalities of retinal microvascular structure and risk of mortality from ischemic heart disease and stroke. Hypertension. 2006; 47: 975–981.

[3] Wong TY, Klein R, Richey Sharrat A, Duncan BD, Couper DJ, Tielsch JM, Klein BE, Hubbard LD. Retinal arteriolar narrowing and risk of coronary heart disease in men and women: the atherosclerosis risk in communities study. Journal of the American Medical Association. 2002; 287(9): 1153-1159.

[4] Gordon-Lipkin E, Chodkowski B, Reich S, Smith SA, Pulicken M, Balcer LJ, Frohman EM, Cutter G, Calabresi PA. Retinal nerve fiber layer is associated with brain atrophy in multiple sclerosis. Neurology. 2007; 69(16): 1603-1609.

[5] Fujita M, Igarashi T, Kurai T, Sakae M, Yoshino S, Takahashi H. Correlation between dry eye and rheumatoid arthritis activity. American Journal of Ophthalmology. 2005; 140(5): 808-813.

 

By | 2015-10-21T13:04:25+00:00 29th September 2015|Eye conditions, Eyesight and Health|0 Comments

Kate’s Running Balls

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!

 

Ingredients

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.

By | 2018-06-28T07:03:01+00:00 27th September 2015|Just for fun|1 Comment

Travelling with Contact Lenses!

So this Friday, I am heading to the airport with my twin sister to fly out of Australia and travel around Europe for almost four weeks! I am currently starting the packing process (what do I pack?!) and my sister, who is an orthoK wearer, asked what she should do with her contact lenses while travelling.  It got me thinking about how many of my patients ask me the same thing!

For some people, travelling with contact lenses is so much of a hassle that they will prefer to leave them at home and just wear glasses. However, I say you don’t have to give up contact lens wear while travelling – especially as they are very convenient when you are do lots of swimming, hanging out at the beach, playing sports (think skiing, beach games, backyard cricket, golf etc) and sightseeing!

Contact Lens websizeThera Tears websize

 

Here are some tips for travelling with your contact lenses to ensure clear vision and healthy eyes!

  • If wearing contact lenses during plane travel, always use lubricating eye drops to prevent the lenses from dehydrating and making your eyes red and sore. Use non-preserved drops (Thera Tears are great!) every 1-2 hours.
  • Again for plane travel, it is a good idea to keep your contacts, case and travel sized solution in your carry-on luggage just in case you and your checked bags get separated!
  • Consider wearing daily disposable contact lenses while you travel. These lenses are worn once, so fresh lenses are worn every day and you eliminate the need to carry heavy and bulky lens solutions.
  • Bring spare lenses! Even if you are only travelling for 2 weeks and you wear monthly lenses, if you accidently tear or lose a lens you will be caught short!
  • Make sure you have your prescription up to date and take it with you just in case.

Travelling is such a fun and exciting time and there is so much to see while we travel so make sure to take care of your contacts and your eyes so you don’t miss a thing!

By | 2018-06-28T07:03:01+00:00 24th September 2015|Eyesight and Health|1 Comment

Three 8 year old Vietnamese kids and OrthoK

In February 2015 Paul and I volunteered a week at the Vietnam National Institute of Ophthalmology in Hanoi, teaching OrthoK fitting to the staff of the Refractive Department. The VNIO is a specialty eye hospital, employing about 500 staff and seeing around 2000 patients per day. I was also there in March 2014 teaching the fundamentals of rigid contact lens fitting, and was greeted with squeezy hugs from Minh Anh (Hanoi’s only qualified optometrist) and Dr Huong (Hanoi’s nicest and most cuddly ophthalmologist) whom I’d worked closely with in 2014 and had kept in touch with since. If you’re wondering why there’s only one qualified optometrist in Hanoi, and indeed only a total of three in a country of 90 million people, read on.

Hanoi had just entered a cold snap as we have arrived, so Minh Anh and Dr Huong brought scarves and extra layers for us today, because they’re so lovely. After three months of relentless 30+ degree heat in Brisbane, though, Paul and I were really enjoying mid-teens temperatures even though the locals were all rugged up! Each morning Paul or I gave lectures to the staff, and then were treated to a tasty lunch at a local street eatery, usually washed down with cinnamon tea. We would then see patients in the afternoon.

On this initial day, our first three patients are all 8 years of age, and all around -5.00. This is generally considered a high level of myopia (shortsightedness), meaning that anything further away than 20cm from their nose is blurred. The younger you are when you become myopic, generally the faster you progress (1) so parents looking to do something to slow down this worsening are wise for two reasons: higher levels of myopia are strongly associated with higher levels of eye diseases like glaucoma, macular degeneration and retinal detachment in adulthood (2) and because very high spectacle prescriptions have been shown to affect quality of life.(3)

Vietnam kids 1 websizee

 

Twin sisters came first – little M only got her last pair of glasses at the end of 2014 and has progressed two more steps of myopia in two months. Her mother said M’s first pair of glasses were only a year ago, and were less than half of the current strength. Her twin sister P has a similar story. After measurement including corneal topography, or mapping of the eye surface to select the best fitting lens, M&P then sat in the waiting room with trial OrthoK lenses on their eyes.

M was reclining in her Dad’s arms with her eyes closed enjoying a toasty winter’s day cuddle. Their mother discussed OrthoK with me through Minh Anh, reassured her daughters and took photos of the two overseas experts discussing trial lens selection with their eye doctors. Mum said she was only -1.00 and her husband is -4.00 – both girls have surpassed their parents’ myopia by only age 8.

Our third patient, a little boy of the same age who soon becomes nicknamed ‘Little Champ’, was lead out of the room with his eyes closed for a similar waiting room nap. We then brought M&P back in to check their lens fitting. M had a reduction in her myopia of nearly half in her 30 minute nap; P a little less. They were shown lens handling along with their mum and dad, and we planned to see them back in the morning. Paul and I gave M&P a koala toy to take home with them which they both seem quite taken with, although their unruffle-able demeanour wouldn’t give it away – they were entirely quiet and calm throughout having eye drops and contact lenses popped onto their eyes.

Vietnam kids 2 websize

 

Around the world there is an increase in children of all ethnicities becoming myopic (4), and the reasons are multifactorial. Minimal time spent outside and high educational demands are key factors. I had an interesting conversation with one of the VNIO ophthalmologists at a dinner held in our honour later in the week. He said his children were myopic, and were getting worse, when they lived in an apartment with no significant outside view. Since they had moved to a higher apartment and could see further from the windows, their eyes had stopped worsening! While there’s probably a bit more to it such as the children getting older, where generally progression will slow down (1), there’s some truth to this observation!

Optometry isn’t a regulated profession in Vietnam, meaning that anyone can set up an optical shop with an automatic refraction machine (which takes an average reading of a spectacle prescription) and call themselves an optometrist or optician. Across the road from VNIO, the street is lined with these optical shops. Unfortunately for a lot of these myopic kids, this means that their glasses aren’t accurate, and whether they are over- or under-corrected, both can lead to worsening of myopia.(5,6)

Little Champ returned and his lenses look good for proceeding to an overnight trial. Mum was then  instructed on lens handling and was struggling a bit, which gave Little Champ the giggles – no sight of tears or even a frowny face! While Dr Huong finished lens care discussions with his mum, Little Champ was folding up a paper plane out of a tissue I gave him earlier and flying it towards his toy koala. We saw him the next morning too.

Our three 5D myopic kids have done brilliantly after their first night in OrthoK. Twin girls M&P both crack smiles when their lenses are taken off, experiencing clearer vision with over half of their myopia being reduced in one night. Little Champ arrives at 9am and peeks in through the glass windowed door, looking a bit squinty as is normal on the first morning when the lenses are worn in for fitting assessment. He stands up in front of the microscope, rather than sitting down, because it’s at the perfect level for his 3 and a half feet of height. He’s been lucky enough to undergo even more overnight myopia reduction than our twin girls, and happily departs with all three due for follow up in another week

 

REFERENCES

  1. Donovan L, Sankaridurg P, Ho A, Naduvilath T, Smith III EL, Holden BA. Myopia progression rates in urban children wearing single-vision spectacles. Optom Vis Sci 2012;89:27-32.
  2. Flitcroft DI. The complex interactions of reintal, optical and environmental factors in myopia aetiology. Prog Retin Eye Res 2012;31:622-60.
  3. Rose K, Harper R, Tromans C, Waterman C, Goldberg D, Haggerty C, Tullo A. Quality of life in myopia. Br J Ophthalmol 2000;84:1031-4.
  4. Dolgin E. The myopia boom. Nature 2015;519:276-8.
  5. Chung K, Mohidin N, O’Leary DJ. Undercorrection of myopia enhances rather than inhibits myopia progression. Vis Res 2002;42:2555-9.
  6. Gwiazda JE, Hyman L, Norton TT, Hussein ME, Marsh-Tootle W, Manny R, Wang Y, Everett D; COMET Group. Accommodation and related risk factors associated with myopia progression and their interaction with treatment in COMET children. Invest Ophthalmol Vis Sci. 2004 Jul;45:2143-51.

 

By | 2018-06-28T07:03:01+00:00 22nd September 2015|Contact Lenses, Eye conditions|0 Comments

Horsing Around

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!

Horsing around in text image

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.

 

REFERENCES

  1. Murphy J, Hall C, Arkins S. What horses and humans see: a comparative review. Int J of Zoology 2009, Article ID 721798.
  2. McMullen RJ, Gilger BC. Keratometry, biometry and prediction of intraocular lens power in the equine eye. Vet Ophthalmol 2006;9(5)357-60.
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By | 2018-06-28T07:03:01+00:00 17th September 2015|Just for fun|0 Comments

Tasmanian Lifestyle Congress wrap up!

This past weekend, Kate, Paul and myself braved the incredibly chilly Hobart weather to attend the 11th Tasmanian Lifestyle Congress (TLC). It was a weekend sure to be filled with fun, an exciting private viewing of the artworks in the Museum of Old and New Art (MONA) and of course, lots of nerdy learning!

Both Saturday and Sunday were jam packed full of interesting lecture topics ranging from kids’ vision (we had particular interest in this!), retinal disease, novel lenses for people with significant vision loss and good nutrition for the eye. Sunday morning over a delicious breakfast, Paul presented a lecture on the history of orthokeratology which highlighted the improvements in orthoK technology (lens designs, assessment techniques etc) over the past few decades. Sunday afternoon, Kate presented a lecture on myopia control in kids – one of her biggest optometric passions and a lecture she has presented at conferences around the world. It was very inspiring watching and listening to two people who are so passionate about optometry and what we as optometrists can do for our patients!

Amongst all the learning, we managed to explore the sites of Hobart – including an incredibly quick visit to the Salamanca markets in the wind, rain and freezing temperatures! My Aunt and Uncle, local Hobart residents all their lives, took me to a lovely French inspired cafe in Battery Point (oldest part of Hobart) for breakfast on Saturday morning. I was excited to wander around the Salamanca markets but as it was a particularly unfavourable day weather-wise, I only lasted about five minutes before hightailing it back to the warmth of the hotel! I may be a well seasoned shopper, but even I couldn’t do much damage in that time!

Saturday was the Congress Dinner at MONA. We had an hour where the museum was only open to us so we could explore and check out the artwork. One of my personal favourite installations was the ‘Waterfall wonder’ – random words cascade down the sandstone backdrop to represent the flood of words/information we are constantly exposed to. There are some pretty ‘out there’ artworks at MONA too but I’ll leave it to you to Google search what I am talking about!

All in all, TLC was a great conference with a relaxed and welcoming vibe where I learnt lots of new things, met some wonderful colleagues around the country and got to spend some time in beautiful Hobart.

By | 2018-06-28T07:03:01+00:00 3rd September 2015|General Eye Interest, What we've been up to|0 Comments