Dr Michael Forrest

When looking at a near target, such as text on a page (or a phone), the eyes converge so that both are fixating on the object of regard. Convergence Insufficiency, in which the two eyes struggle to maintain fixation together on a near target, is a reasonably common condition in childhood and a cause of double vision, blur at near, and reading difficulty. It has often been treated using vision therapy.

More than 10 years ago the Convergence Insufficiency Treatment Trial (CITT) showed that office-based vision therapy was superior to placebo for treatment of measurable indicators of convergence insufficiency (“near point of convergence” and “positive fusional vergence”). Two follow-up papers from this study were published this week (online pre-publication) in Optometry and Vision Science and show that although these measurable markers of the condition improved with vision therapy, patient reported symptoms (via a patient survey) and, most importantly, reading performance, were not improved by vision therapy any more than by placebo.

The two take-home messages from these trials are:

If you treat convergence insufficiency, use clinical measures, rather than self-reported symptoms, to assess the severity of the condition and the response to treatment; and
if you treat convergence insufficiency, do not claim that it will improve reading skills, because it doesn’t any more than placebo.

These studies were funded by the National Institutes of Health in the USA, and conducted by academic optometry units across the USA. The study chairperson was Dr Mitchell Scheiman OD PhD, Professor at Pennsylvania College of Optometry and a vision therapist.

References:

CITT-ART Investigator Group . Effect of Vergence/Accommodative Therapy on Reading in Children with Convergence Insufficiency: A Randomized Clinical Trial. Optometry and Vision Science: October 23, 2019.

CITT-ART Investigator Group. Treatment of Symptomatic Convergence Insufficiency in Children Enrolled in the Convergence Insufficiency Treatment Trial–Attention & Reading Trial: A Randomized Clinical Trial. Optometry and Vision Science: October 23, 2019.

This international annual global day of awareness was started in 2000 by Lions Club International, and aims to be a call to action for governments and NGOs, as well as individuals.

This year the theme is “Vision First”. Worldwide there are more than 250 million people with visual impairment, 36 million of which are blind. More than 75% of these people are suffering avoidable causes of vision loss, and almost 90% of visual impairment is suffered in low and middle income countries.

In Australia, Vision 2020 is focussing on the inequality of health outcomes experienced by people of Aboriginal and Torres Strait Islander descent, and on prevention. We recommend regular eye checks, especially for over-40s, quitting smoking, eye protection for sports and work, regular exercise and following a healthy diet, wearing a hat and sunglasses, and managing diabetes.

#WorldSightDayAU

Most people having surgery to remove cataracts have been wearing glasses for years by the time their cataracts start to affect vision. Many are well used to glasses by then and ambivalent about wearing them, but an increasing number of people hope to have a degree of independence from glasses.

Before cataract surgery measurements are taken of a patient’s eyes. This is known as ocular biometry. The length of the eye, curvature of the cornea, depth of the front chamber of the eye and width of the cornea are measured, and several formulae are available to translate these measurements into a useful prediction of which intraocular lens (IOL) to implant to give good unaided distance vision. Lens selection takes quite a lot of time, and happens outside the operating theatre. With modern measurements and modern formulae the results of this prediction are very good, but not perfect. The occasional patient will still require glasses for distance, though these days the vast majority of people maintain driving vision after surgery without glasses.

Improving near vision without glasses is the challenge that lens manufacturers and surgeons are continuing to work on, but at present there are 3 main options for people that wish to improve near vision after cataract surgery: “mono-vision”, multifocal IOLs, and newer “Extended depth of focus” IOLs. All have advantages and drawbacks.

“Mono-vision” means implanting one eye with an IOL for distance and the second eye with an IOL for near. The compromise is that if the second eye is sufficiently myopic to read well, depth perception will usually be lost, and if the second eye is only slightly myopic (“mild” or “mini-“ mono-vision) so that depth perception can be preserved, reading glasses will still be needed for small print. Some people find mono-vision intolerable, although mild mono-vision is much better tolerated.

Multifocal IOLs, which have been around in one form or another for many years now, work by incorporating separate discrete optical zones into the lens. Patients with multifocal IOLs “adapt” to use the individual zones separately, with both bi-focal and trifocal options available.The technologies used to achieve the discrete zones differs between lenses, as does the distance at which near vision is clearest. All multifocal IOLs induce some degree of optical side-effects, usually haloes or “starbursts” around lights at night, presumably due to blur from the other focal zones. These effects can be severe enough that some patients choose to have a second operation to remove the lens and replace it with a monofocal IOL. In addition, because the multifocal IOL splits light between distance, intermediate and near zones (or, in the case of bifocal lenses, distance and near), contrast sensitivity suffers. This makes them inappropriate for most patients with optic nerve disease (including glaucoma) or macular disease (including macular degeneration, epiretinal membrane or diabetic maculopathy).

The latest alternative is the new category of “extended depth of focus” (EDOF) IOLs. These use similar technology to the multifocal IOLs, but induce less myopic defocus so that the risk of both reduced contrast sensitivity and bothersome haloes and glare is much less, and the compromise in distance vision is much less than with multifocal IOLs. The compromise is that these IOLs improve intermediate vision (eg reading your phone), but are not a replacement for reading glasses for most people.

IOLs that improve unaided near vision have come a long way, and are constantly evolving. For the right patient, well-informed and motivated, they can offer increased freedom from wearing glasses. They are not for everyone, though, which is why they accounted for less than 2.5% of all IOLs implanted world-wide in 2014.

Recently the NSW State Government came under fire for regulating “eyeball tattooing”. In this form of body modification tattoo ink is injected under the conjunctiva to colour the sclera. A tattoo artist, Luna Cobra, claims to have invented the procedure, and to have performed it on around 10 Australians.

This is clearly a specific tattoo niche, with a limited market. But there are major problems trying to regulate novel non-therapeutic procedures, because regulation implies that there is a safe way to perform the procedure. Skin tattooing is an ancient practice, and the earliest known tattoos were found on Otzi, the natural mummy found in South Tyrol, Italy, who lived between 3359 and 3105 BCE. The risks of skin tattooing are fairly well understood. Tattooing the sclera, on the other hand, is new, the long-term hazards are unknown, the risks of the procedure itself are many, and include blindness. The case of a man whose attempted eyeball tattoo resulted in eye penetration and tattoo pigment deposited inside his eye, requiring multiple surgeries to try and repair the damage, was published in August. There seems very little to be gained by attempting to regulate the practice, or in trying to judge who can, and who cannot, perform it safely. The sclera varies in thickness from 1.2mm down to 0.3mm in places, and perforation is a major risk anytime a needle goes near an eye. The needles I use to reattach extraocular muscles during strabismus surgery are specially designed to maintain a level within the sclera and reduce the risk of perforation.

Corneal tattooing has been used therapeutically, to restore a more normal appearance to a blind eye. The most effective way to achieve a good outcome is still not clear.

Kymionis GD1, Ide T, Galor A, Yoo SH. Femtosecond-assisted anterior lamellar corneal staining-tattooing in a blind eye with leukocoria. Cornea. 2009 Feb;28(2):211-3.

Jalil A, Ivanova T, Bonshek R, Patton N. Unique case of eyeball tattooing leading to ocular penetration and intraocular tattoo pigment deposition. Clin Experiment Ophthalmol. 2015 Aug;43(6):594-6.

There has been a lot of recent discussion in the media about concerns that myopia (short-sightedness) may be increasing among children. Parents are often concerned whether or not they can do something to reduce the chance of their children becoming myopic, or reduce their myopic progression if they already are myopic.

Risk factors for myopia in children include having myopic parents (even after controlling for environmental and demographic differences), and higher socio-economic status. A lot of work has focussed on the impact of near work and time spent indoors. Studies looking at the influence of these factors need to be very carefully designed, because of the potential for confounding bias. People who spend a lot of time outdoors may also be more likely to perform more physical exercise, which needs to be controlled for in study design in case exercise itself is a factor, and may be less likely to spend as much time performing near tasks, so this needs to be controlled for as well.

A number of recent studies have shown that the risk of myopia reduces with increasing time spent outdoors, and increasing light exposure. It also increases with reduced Vitamin D levels, but it is too early to know whether Vitamin D itself plays a role, or whether it is a marker for some other currently unrecognized consequence of light exposure. An interesting recent study in chickens found that intermittent bright light exposure had a greater effect on reducing myopia risk than continuous bright light exposure.

There is much work yet to be done, but so far it seems that putting down the games console and spending a few hours a day running around outside or climbing a tree may be beneficial in ways we parents might not have considered.

Papers:

Lan W, Feldkaemper M, Schaeffel F Intermittent episodes of bright light suppress myopia in the chicken more than continuous bright light. PLoS One. 2014 Oct 31;9(10).

McKnight CM, Sherwin JC, Yazar S, Forward H, Tan AX3, Hewitt AW, Pennell CE, McAllister IL, Young TL, Coroneo MT, Mackey DA. Myopia in young adults is inversely related to an objective marker of ocular sun exposure: the Western Australian Raine cohort study. Am J Ophthalmol. 2014 Nov;158(5):1079-85.

Yazar S, Hewitt AW, Black LJ, McKnight CM, Mountain JA, Sherwin JC, Oddy WH, Coroneo MT, Lucas RM, Mackey DA . Myopia is associated with lower vitamin D status in young adults. Invest Ophthalmol Vis Sci. 2014 Jun 26;55(7):4552-9.

Guggenheim JA, Williams C, Northstone K, Howe LD, Tilling K, St Pourcain B, McMahon G, Lawlor DA. Does vitamin D mediate the protective effects of time outdoors on myopia? Findings from a prospective birth cohort. Invest Ophthalmol Vis Sci. 2014 Nov 18;55(12):8550-8.

Karouta C, Ashby RS. Correlation between light levels and the development of deprivation myopia. Invest Ophthalmol Vis Sci. 2014 Dec 9;56(1):299-309.

Vaccination is not new technology (Edward Jenner developed the smallpox vaccine in 1796), but it is unquestionably amongst the greatest developments of medical science. Before being wiped out in 1979, smallpox is estimated to have killed 300-500 million people worldwide in the first 79 years of the 20th century.

Anti-vaccinationists are not new either, although, along with climate change denial and skepticism about the moon-landings, vaccine skepticism has grown and continues to take hold of a small but quite vocal group. There are a variety of reasons cited by anti-vaccine campaigners for their stance, including safety concerns, government intrusions, and doubts about efficacy.

But reduced uptake of vaccination has consequences for society as a whole, and especially for those vulnerable patients who are unable to be vaccinated because of immuno-compromise or other medical conditions. “Herd immunity” refers to the indirect protection enjoyed by unvaccinated people if the vaccinated population is sufficiently large that a disease doesn’t have enough eligible hosts to be spread. The percentage of people in a population that need to be vaccinated to achieve herd immunity is known as the “herd immunity threshold” (HIT). The HIT is different for different diseases, being relatively low to avoid influenza pandemics (<50%), higher for smallpox and diptheria (~85%), and much higher (~95%) for measles and pertussis (whooping cough, which kills 1/50 infected infants). Since vaccine uptake in Australia is hovering around 90%, we remain at risk of measles and pertussis outbreaks.

The recent history of Measles in Australia, and the US is very informative. In 2012 the largest measles outbreak in Australia in 15 years occurred, with 173 cases reported, mainly in WA and Southwest Sydney. The initial patient had “imported” the disease from Thailand, but it then easily spread amongst unvaccinated or incompletely vaccinated people. In the first 3 months of 2015 almost 160 people in the US contracted measles, and three quarters of these were linked to the so-called “Disneyland measles outbreak.” In most otherwise well patients measles is a self-limiting disease. But it can have severe complications. In developing countries corneal complications of measles are an important cause of blindness, with 43 of 193 blind children in a West African cohort blinded by measles. The most feared complication of measles infection is probably subacute sclerosing panencephalitis (SSPE), which causes sight-threatening problems in one third to one half of patients, and ultimately kills 50-90%.

Yesterday the Federal Government announced a policy to tie receipt of government benefits to compliance with the vaccination schedule, and the Federal Opposition joined the government, making this a bipartisan approach. Australians have long benefited from a well-funded vaccination program, with a world-class vaccination register, and it is great to see both sides of politics anxious to increase vaccine uptake. There is certainly some merit in this policy, but we need to remember that people that are scared of vaccination need information and advice, not just direction. The best place to start is with the family doctor.

Marfan Syndrome is a genetic condition that affects connective tissues, particularly the heart valves, aorta, and the eyes. People with Marfan Syndrome also tend to be tall, with long fingers and toes.

In the eye weakness and loss of the zonular ligaments that support the lens lead to lens dislocation (ectopia lentis) and reduced vision. Patients with Marfan Syndrome are also commonly highly myopic (although hypermetropia or far-sightedness can also occur), and have a substantially increased risk of retinal detachment, chronic glaucoma and early cataract. When the lens dislocates so much that glasses or contact lenses can no longer improve vision, surgery is an option. There are some controversies regarding surgical techniques and options for refractive rehabilitation after surgery, but two papers published this year describe significantly different rates of retinal detachment after surgery for Marfan, with a Chinese group reporting 11 Retinal Detachments in surgery on 64 eyes.

Marfan Syndrome was first described by Antoine Marfan, a French paediatrician, at the end of the 19th century. We now know it is caused by mutations in a gene called FBN1, which encodes fibrillin-1, a glycoprotein essential for the elastic fibres in connective tissues. The exact mechanism is not yet clear, but it looks as though fibrillin-1 prevents the accumulation of transforming growth factor beta (TGF-β), and it is likely that reduced fibrillin-1 activity in people with the FBN-1 mutation leads to accumulation of TGF-β, and that this in turn leads to the connective tissue changes of Marfan Syndrome.

When I trained in ophthalmology a combination of systemic signs was required for the diagnosis of Marfan to be made. Someone with ectopia lentis but no other problems was considered to have “isolated ectopia lentis”. We know that eye changes can occur before, and without, significant heart defects in people with Marfan, and few years ago the diagnostic criteria (the so-called Ghent Nosology) was changed so that people with ectopia lentis and either a family history of Marfan, or a FBN-1 mutation, can be diagnosed with the condition. This is important both for assessing their individual risk of developing complications, and for genetic counselling.

In Marfan Syndrome, early diagnosis can reduce the impact of the condition on vision, and reduce the likelihood of cardiac complications.

Articles

F Fan et al. Risk factors for postoperative complications in lensectomy-vitrectomy with or without intraocular lens placement in ectopia lentis associated with Marfan syndrome. Br J Ophthalmol. 2014 Oct;98(10):1338-42.

Miraldi Utz et al. Surgical management of lens subluxation in Marfan syndrome.J AAPOS. 2014 Apr;18(2):140-6.

Wrong-site surgery (performing surgery on the wrong side, wrong body part, wrong patient, or using the wrong prosthesis) is very rare, but is the most common surgical mistake. And, at least in theory, it should be easily avoided.

Ten years ago I was the RANZCO representative on a multi-disciplinary Queensland Health committee that developed Queensland Health’s correct site surgery policy and protocol. This was quite educational because around the world there are a variety of protocols that attempt to prevent this complication, and not all of them work. Some are too complicated, which means people in busy hospitals may skip steps or make errors in following the policy itself.

One research paper in the Archives of Surgery found that the incidence of wrong site surgery was less than 1 in 100,000 operations, and that most of these did not result in significant problems, but that existing protocols would only have avoided about two thirds of these. Protocols were often too complex and ineffective.

In Queensland there are 4 steps: identify the patient, check informed consent, mark the site with the patient awake, and a final check in which surgeon, scrub nurse and anaesthetist check patient, side, planned operation and prosthesis before starting.

For patients this constant checking and double-checking can be a bit tedious, but this is a simple and pretty quick way of eliminating this avoidable error.

Reference:

MR Kwaan et al.Incidence, patterns, and prevention of wrong-site surgery. Arch Surg. 2006 Apr;141(4):353-7; discussion 357-8.

Last weekend I attended the AMA National Conference in Canberra to see The President’s Medal awarded posthumously to Dr Bernard Quin. Dr Quin was an Australian doctor working in Nauru in the 1930’s, and then into the early years of the Second World War whilst Australian soldiers were stationed there. He cared for Australian workers and soldiers, and the broader local community, including a “leper colony”. After the withdrawal of Australian troops he stayed behind to continue to care for his patients while his young family were moved to safety in Melbourne. Japanese forces occupied the island and a little over 6 months later Dr Quin was murdered, along with 4 other Australians, in retaliation for an Allied raid.

I was excited to see the presentation, partly because my wife Dr Angela Ryan had been working very hard for a long time to get some form of recognition for Dr Quin. We had come to know his story through his son, Fr Peter Quin, who christened our son, and we had both been deeply affected by it. But I was also excited to witness this presentation because Dr Quin fully embodied an ideal, that of placing the welfare of our patients first. As doctors we hope to be capable of this, and recognizing a sacrifice such as his can renew our faith that this ideal, while extraordinary, is not lost to us.

Why didn’t cavemen need glasses?

I am frequently asked for advice about avoiding or ameliorating myopia, or short-sightedness, so I was interested to read a piece in The Courier Mail recently (“Caving in to the accidental diet”, Sue Dunlevy and Sarah Orr) discussing the Paleo Diet. Dunlevy and Orr quote Loren Cordain, an exercise physiologist at Colorado State University, advocate for the Paleo diet, and a researcher that has previously published an hypothesis that relates the modern observed increased prevalence of myopia to modern changes in diet. Online experts/advocates for the Paleo diet have claimed numerous health benefits on its behalf, so what’s this all about?

The Paleolithic Diet (“Paleo Diet” is trademarked) is an attempt to adopt assumptions about what early humans ate (during the “Paleolithic Era”, which ended around 10 000 years ago) and adapt them to a modern post-industrial society. The reasoning is that since we evolved to eat the diet of early humans, we should be more healthy doing so. The enthusiasm for it is based on observations made since the late 19th and early 20th century that many of the “diseases of civilization” (eg diabetes, heart disease, appendicitis, cancer, and myopia) were unknown in pre-agricultural societies when those societies were first encountered by modern doctors, but became common once these same societies transitioned to a Western diet and Western lifestyles were adopted. Some knowledge of the diet of early humans can be derived from the activity of modern hunter-gatherers, but much is derived from archeological enquiries that are properly in the field of paleo-anthropology.

From modern hunter gatherers we know that the prevalence of myopia is extremely low, around 1% or so, in pre-agricultural/pre-Industrial humans. In Western countries it is significantly greater (more than 15% in Australian adults), and higher still in Asian countries. There is significant evidence that this disparity is multifactorial, and correlates with parental education and numbers of books read amongst other factors, and inversely correlates with time spent outdoors. Cordain’s hypothesis is that high GI diets (diets high in refined carbohydrates that the body quickly breaks down to glucose, ie white flour, white rice, sugar) lead to an increase in insulin secretion, which has a number of biochemical consequences in the body. These include suppression of IGF-binding protein-1 (IGFBP-1), and increased IGF-1 (insulin-like growth factor-1). This can have effects on tissue growth, but also may lead indirectly to suppression of IGF-binding protein-3 (IGFBP-3), leading to effects on retinoid receptor signaling in the eye.

It’s an intriguing hypothesis, but there are a few problems with adopting a stone-age diet to treat your myopia. Firstly, working out what stone-age man ate on a day-to-day basis is more difficult that you might think, and adopting such a diet even harder. Hunter-gatherers forage and hunt, and eat everything when they hunt, often prizing organs such as liver and brain. Secondly, when modern hunter-gatherers hunt and forage, they typically cover a lot more ground than most city dwellers (15km daily for men, 9km daily for women). In the Paleolithic early man probably hunted by running-down prey, in what is termed “persistence hunting”, covering even more ground. So if you want to live like a caveman, get out and run!

That’s not to say that evolution can’t teach medicine anything. Quite the opposite. Learning about how we evolved to become human teaches us quite a lot about what it means to be human, at least as far as our bodies are concerned. Our modern diets and lifestyles would be unimaginable to our pre-agricultural cousins, and for all the technological improvements that have helped us treat infections and other diseases, we are spending more of our healthcare resources treating diseases that are, to a very large extent, caused by the way we live. Spending more time on our feet and eating less highly processed foods intuitively make sense, and find support in the available research. But the relationship of diet to myopia progression is more problematic.

Part of the problem is the interpretation of available data, which is often colored by the prism of the established low-fat diet dogma. A relatively recent study of Singaporean children in which diet was assessed by a survey completed by the children, and then stratified according to carbohydrate, total fat, cholesterol, saturated fat and polyunsaturated fat intake, concluded that myopia progression is associated with cholesterol intake. The data, included with the paper, is difficult to reconcile with the author’s conclusion, and appear to me to support only a conclusion that dietary fat, cholesterol and carbohydrate have no apparent impact on myopia progression.

We need to be very careful when assessing research that advocates changes in the way we live our daily lives. Having a better understanding of where we came from May help this. But recognizing that is understanding is a work in progress is paramount.

@doctor_forrest

Cordain L, Eaton SB, et al. An evolutionary analysis of the aetiology and pathogenesis of juvenile-onset myopia. Acta Ophthalmol Scand. 2002 Apr;80(2):125-35.

Lim LS, Gazzard G, et al. Dietary factors, myopia, and axial dimensions in children. Ophthalmology. 2010 May;117(5):993-997

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