Wednesday, January 30, 2013

New study confirms orthokeratology for slowing myopia progression

Orthokeratology slows the progression of myopia by causing positive changes in the peripheral retinal

Yet another study, this one out of Australia, supports orthokeratology for slowing the progression of myopia.  The study was published in the journal Ophthalmic & Physiological Optics on January 24, 2013.   

The goal of the study authors was to describe the time course of changes in both peripheral refraction and corneal topography in myopic adults wearing myopic orthokeratology (OK) lenses.  That means that the researchers wanted to to see how the surface of the cornea - the clear dome that covers the colored part of the eye - changed over time and whether the focusing power of a subject's peripheral vision changed overtime when overnight orthokeratology lens retainers were worn.

The study design was simple.  Nineteen patients were fitted with ortho-k lenses and the researchers measured their peripheral focusing power and the contours of the surface of the cornea after 1, 4, 7 and 14 nights of ortho-k retainer lens wear.

The study reached the following conclusions:

Orthokeratology caused significant changes in both peripheral refraction and corneal topography. The greatest change in refraction and corneal refractive power across the horizontal corneal meridian occurred during the first night of OK lens wear. Subsequent changes in both peripheral refraction and corneal topography were less dramatic, in the same manner as reported changes in apical radius and central refraction after OK. This study confirms that with OK treatment, the peripheral retina experiences myopic defocus, which is conjectured to underlie the observed slowing of myopia progression.
The study adds to our understanding of the mechanism by which orthokeratology slows myopia progression.  The culprit in myopia is thought to be focusing power in an eye's peripheral vision.  This study explains how orthokeratology causes positive changes in this part of the eye that result in a slowing of myopia progression

The role of the peripheral retinal in causing myopia progression may be difficult for the lay person to understand.  One of the best explanations that we have read comes from the College of Optometrists in Vision Development blog post, "Its All About the Blur":

New theories on the development of myopia are evaluating the role of peripheral retina. When lenses are prescribed for any type of refractive error (myopia, hyperopia, astigmatism), those lenses put a clear and focused image on the fovea, which is essentially the “bullseye” on the retina. Whenever we want to see something clearly, we aim our eyes so the image falls on the fovea. The lenses allow us to see clearly precisely because the image is focused on the fovea. But those lenses (especially spectacles) have a different curvature than the retina. The result is a slight defocus on the peripheral retina. The further away from the central retina you are, the greater the amount of defocus. This is not something noticeable by the average patient, because the amount of blur is small, and because we don’t notice blur as well in the periphery. But it seems that our retinas DO notice, because there is significant evidence that this peripheral defocus drives the eye to elongate, and that elongation results in myopia.

Related articles: 

Orthokeratology is shown to be safe for correcting myopia in children
Aug 11, 2012

Orthokeratology is shown to be effective in correcting astigmatism and myopia
Jun 18, 2012

New study supports orthokeratology for myopia control and for astigmatism correction
Jan 10, 2012

Laser eye surgery makes you queasy? Orthokeratology is a safe and effective alternative 
Jun 09, 2011

The myopia epidemic: why it is so dangerous. - See For Life
Oct 12, 2011.

Tuesday, January 29, 2013

Vision loss from glaucoma - preventable if caught early - is on the rise in Canada: Canadians are not taking easy steps to protect themselves

Research published in the June issue of the Journal of Ophthalmology shows that Canadians are not taking easy steps to protect themselves against glaucoma.  The study found that 50% of those who are newly diagnosed with the disease are already in the moderate to advanced stages of the disease.  By this time they have suffered irreversible and often devastating vision loss.

Early detection is key because if caught early glaucoma can be managed and its progress halted.  But there are virtually no symptoms in the early stages of the disease.  That is why early detection is only possible through a complete eye exam by an optometrist or ophthalmologist. 
The obvious implication of the study is that Canadians are not doing enough to protect themselves against glaucoma.  Everyone should have an annual eye exam.

An article in the Toronto Star presented the following story that puts a human face on the tragedy that can occur if one ignores the need for eye exams as well as how fortunate you can be if you see your optometrist:
Keith Henderson, 62, a retired millwright in Alvinston, Ont., is fortunate. Ten years ago his brother was diagnosed with advanced glaucoma, which prompted Henderson to see an optometrist and request extra vigilance. Extra tests — which he had to pay for — showed he had high pressure. He eventually had prophylactic laser treatment to relieve the pressure.
“I won’t lose my eyesight to glaucoma because of what has been done,” says Henderson.
Henderson’s brother, Larry, now 65, is just about completely blind now, he says. The factory worker, was 55 when diagnosed, didn’t know to get regular exams.
“He didn’t get checked because he didn’t have coverage and then it started to get severe,” Henderson says. “They’ve got him as good as they could get him, but he’s lost a terrific amount of his vision.”
Diagnoses before there is vision loss is key. For patients, who catch it early and are diligent with treatment, vision can be preserved, Buys says.
Too many are doing it too late. “In a country that boasts of universal health care, our patients are coming in with already serious and significant loss of vision,” Hutnik says.
While we have a health care systems that calls itself "universal", eye exams are not covered.  Yet, as the story above demonstrates, they are critical.  The rationale for not insuring critical health services is often founded on the principle that people must have personal responsibility for their own health.  For whatever reason - lack of knowledge, lack of resources, lack of awareness of what can go wrong with their health - too many people are not doing the right things.  I hope some of them will read this blog post and make an appointment with their optometrist. 

Wednesday, January 23, 2013

Non-surgical treatment alternatives to strabismus surgery - the risk of a single childhood exposure to anesthesia

The risks of strabismus surgery and exposure to anesthesia during surgery

We previously wrote about the new scientific evidence that repeat exposure to anesthesia at a young age is associated with the development of learning disabilities and ADHD later on in life.  As eye doctors, we care about this because strabismus (cross eyes, eye turn, esotropia, exotropia) is often treated in very young children with surgery using general anesthesia.  The safety of exposing children to anesthesia has been questioned in light of the recent research.  And with strabismus surgery there is a very high risk of repeat surgeries being performed on the same patient (click here to learn about all the risks of strabismus surgery) which means more potentially harmful anesthesia exposure.

The risks of surgery pose a problem because vision therapy is a safe and effective non-surgical treatment for most types of strabismus, which makes most people think twice about surgery as a first choice treatment.

A famous case of vision therapy treatment for strabismus was the subject of the book Fixing My Gaze, an inspirational book by neuroscientist, Susan Barry, who was born with strabismus and had lived all her life without stereo vision, meaning that she could not see in three dimensions.

Even a single exposure to anesthesia during surgery is associated with developmental problems in children: new study

There is now new evidence that even a single exposure to anesthesia can be dangerous for a child.  A study published in December 2012 in the journal Evidence Based Medicine  found that children exposed to anaesthesia for surgery under 3 years of age were found to be at significantly increased risk for developing disabilities in receptive language, expressive language, total language and abstract reasoning at age 10.

The study authors commented that:

This study was the first to report the effects of anaesthetic exposure early in life on neuropsychological outcome using individually administered neurocognitive tests. Perhaps due to the greater sensitivity of these tests, Ing and colleagues observed disability even following a single exposure in early childhood, while several previous reports, utilising group-administered tests, had only detected learning abnormalities following multiple exposures.

This is the latest of 250 studies that have linked anesthesia exposure at a young age to brain development disorders.  The previous studies found a link between anesthesia and learning disabilities in children who had two more more exposures to anesthesia, while the new study found a link in children with just one exposure.  In the study's own words:

Thus far, more than 250 studies in immature animals have demonstrated that exposure to commonly used anaesthetics produces neuronal cell death, alters brain development and may lead to neurocognitive impairment. Similarly, in humans, an association between learning disabilities and two or more anaesthetic exposures has been observed in some studies, as most recently reported in children under 2 years of age.
According to Cyber-Sight, a program of ORBIS International, a non-profit organization that prevents and treats blindness by providing quality eye care, "most immature patients (younger than mid-teens) require general anesthesia for extraocular muscle surgery." Click here to read more about anesthesia use in strabismus surgery.

Repeat strabismus surgeries are common

Children who have strabismus surgery are risk of repeat surgeries, all of which carry the same risk. Eye surgeons often lament the need for repeat eye surgeries for strabismus patients. Surgeon, John W. Simon, notes that "patients must regularly contend with the unfortunate reality that even the most accurately planned and carefully executed surgery may not totally eliminate the deviation [i.e. the misalignment of the eyes] or completely normalize rotations. In addition, strabismus tends to recur over time." This limitation of surgery often results in the the patient being subjected to repeated surgeries - all of which may be unsuccessful. It is not uncommon for a patient to have had two or three or more surgeries and still have a noticeable misalignment or poor binocular vision together with depth perception problems or all three. For this reason, the surgeon's view is that "strabismus is less a problem to be cured than a problem to be controlled, with the minimum number of surgeries": Simon, John W. Complications of Strabismus Surgery. Current Opinion in Ophthalmology. 2010. 21: 361-366.

One study found that only 45% of children had successful alignment of the eyes at an eight-year follow up to their strabismus surgery. And while the low percentage was disappointing enough, 20% of the children had to undergo repeat strabismus surgeries which were ultimately unsuccessful: Awadein A, Sharma M, Bazemore MG, et al. Adjustable suture strabismus surgery in infants and children. J AAPOS 2008; 12:585–590.

Parents need to get the right information and ask the right questions

Parents of children with strabismus need to carefully evaluate the available treatment options.  They should see a developmental optometrist like Dr. M.K. Randhawa  to talk about whether vision therapy is effective for the type of strabismus that the child has.   Parents contemplating surgery need to ask their surgeons about the risk of anesthesia exposure during surgery as well as all the other risks of strabismus surgery (ranging from death - a mortality rate of 1.1 per 10,000 cases is reported - scars, repeat surgeries, infections, lost muscles, vision loss, lack of depth perception). 

Parents should consider vision therapy if their developmental optometrist thinks that vision therapy is appropriate for the type of strabismus that the child has. At our clinic, we have successfully treated dozens of strabismus patients, achieving straight eyes as well as functional binocular vision and depth perception and other developmental optometrists likely have similar results. 

Here is a TED talk on vision therapy by neuroscientist, Dr. Susan Barry, author of Fixing my Gaze:

Thursday, January 17, 2013

South Asians are at higher risk of glaucoma - January is Glaucoma Awareness Month

Look out South Asians living in North America! You have a higher risk of glaucoma than other ethnicities, according to a new American study that looked at glaucoma risk among Asian Americans, including those of Indian and Pakistani ancestry. While the study looked at Americans, the findings will likely apply to Canadians who share a similar diet and lifestyle.

The study concluded that, among Asian Americans, Japanese Americans have the highest risk (9.5%) followed by Indian and Pakistani Americans (7.7%) of open angle glaucoma, the most common variant of the disease.

If you have a high risk of glaucoma, the best thing that you can do to protect yourself is to see the eye doctor at least once a year. Glaucoma can only be detected early enough in an optometric eye examination. It does not cause pain or blurriness or other obvious symptoms. That is why doctors often call glaucoma the "silent thief of sight". The disease is so gradual that you will likely not know that you have suffered permanent vision loss, beginning with your peripheral vision. Some people with undiagnosed glaucoma are no longer legal to drive and don't know it. Read this older post for more about glaucoma.

For optometrists and ophthalmologists, this study means that they need to carefully examine their Asian patients and check both the pressure inside he eye and assess the condition of the optic nerve as well as perform visual field testing where appropriate.

Vision therapy or surgery for strabismus (esotropia, exotropia)?

Strabismus surgery.  Image: wikipedia.

We here at Vision Source Vancouver think that it makes good sense to use effective non-surgical vision therapy to treat strabismus (sometimes called cross eyes, eye turn, esotropia, exotropia).  The reason is that strabismus or eye muscle surgery has many risks of bad or harmful outcomes.   

This website has featured articles outlining the risks associated with strabismus surgery and reported on studies that demonstrate the effectiveness of vision therapy in treating most kinds of strabismus -without any of the risks associated with surgery.

Professor Dominick Maino, a fellow of the College of Optometrists in Vision Development, recently had a discussion with an eye surgeon on his own blog, MainosMemos, on why surgery, because of the risks and results that are not satisfactory for many patients,  should only be used as a last resort. As only one example of undesirable outcomes, a study on surgery found that only 45% of children had successful alignment of the eyes at an eight-year follow up to their strabismus surgery. And while the low percentage was disappointing enough, 20% of the children had to undergo repeat strabismus surgeries which were ultimately unsuccessful: Awadein A, Sharma M, Bazemore MG, et al.Adjustable suture strabismus surgery in infants and children. J AAPOS 2008; 12:585–590. 

Other risks of strabismus surgery include death, infections, blindness, scars, mistakes like surgery on the wrong eye, etc.  You can read more about risks here

One can't ignore the studies regarding anesthesia and the potential for future cognitive impairment. This is a work in progress and the pediatric specialties are following closely.
However, the surgeon goes on to say:

Like anything in medicine (and you should be well-versed since you received an "Excellence in Medicine" award) you have to consider the risk-vs.-benefit ratio. If I have a young patient with a 40 PD decompensated exotropia who is in danger of developing irreversible amblyopia and loss of stereoacuity, 30-40 minutes of anesthesia for strabismus surgery is not going to prevent him or her from getting into Harvard. [NB vision therapy and patching will not touch a 40 XT]. People need to be properly educated, look at all of the facts, and not over-react.
If there are no studies that prove that anaesthesia during strabismus surgery is totally safe, our point is that it is not sensible to take the risk when you don't need to.  The basic ethical principle in medicine is "do no harm".  If there is a treatment option that has no risk of harm, it should be the first choice.  There are some types of strabismus that vision therapy cannot effectively treat, and for those surgery is probably a good idea given the cost-benefit analysis.  But for the most common kinds of strabismus, vision therapy is a safe and effective treatment. 

Dr. Maino referred to the following recent studies on strabismus surgery that highlight the reasons why it should not be first choice option for treating strabismus:

Haridas A, Sundaram V. Adjustable versus non-adjustable sutures for strabismus. Cochrane Database of Systematic Reviews 2005, Issue 1. Art. No.: CD004240. DOI: 10.1002/14651858.CD004240.pub2

"No reliable conclusions could be reached regarding which technique (adjustable or non-adjustable sutures) produces a more accurate long-term ocular alignment following strabismus surgery or in which specific situations one technique is of greater benefit than the other. High quality RCTs are needed to obtain clinically valid results and to clarify these issues. ......"

Rowe FJ, Noonan CP. Botulinum toxin for the treatment of strabismus. Cochrane Database of Systematic Reviews 2012, Issue 2. Art. No.: CD006499. DOI: 10.1002/

The majority of published literature on the use of botulinum toxin in the treatment of strabismus consists of retrospective studies, cohort studies or case reviews. Although these provide useful descriptive information, clarification is required as to the effective use of botulinum toxin as an independent treatment modality. Four RCTs on the therapeutic use of botulinum toxin in strabismus have shown varying responses ranging from a lack of evidence for prophylactic effect of botulinum toxin in acute sixth nerve palsy, to poor response in patients with horizontal strabismus without binocular vision, to no difference in response in patients that required retreatment for acquired esotropia or infantile esotropia. It was not possible to establish dose effect information.Complication rates for use of Botox™ or Dysport™ ranged from 24% to 55.54%.

Elliott S, Shafiq A. Interventions for infantile esotropia. Cochrane Database of Systematic Reviews 2005, Issue 1. Art. No.: CD004917. DOI: 10.1002/14651858.CD004917.pub2

The main body of literature on interventions for IE are either retrospective studies or prospective cohort studies. It has not been possible through this review to resolve the controversies regarding type of surgery, non-surgical intervention and age of intervention. There is clearly a need for good quality trials to be conducted in these areas to improve the evidence base for the management of IE.

Br J Ophthalmol. 2012 Oct;96(10):1291-5. Epub 2012 Aug 11.Surgical intervention in childhood intermittent exotropia: current practice and clinical outcomes from an observational cohort study. Buck DPowell CJSloper JJTaylor RTiffin PClarke MPImproving Outcomes in Intermittent Exotropia (IOXT) Study group

After surgery 65% had fair to poor outcomes and 20% of the subjects remained XT or the XT recurred

BMC Ophthalmol. 2012 Jan 18;12:1. doi: 10.1186/1471-2415-12-1.The improving outcomes in intermittent exotropia study: outcomes at 2 years after diagnosis in an observational cohort.
Buck DPowell CJRahi JCumberland PTiffin PTaylor RSloper JDavis HDawson EClarke MP.

....8% ...of those treated surgically required second procedures for overcorrection within 6 months of the initial procedure and at 6-month follow-up 21% ... were overcorrected ....

Wednesday, January 16, 2013

January 2013 is Glaucoma Awareness Month

January is Glaucoma Awareness Month. We urge everyone to take control of their eye health and have an eye exam to help minimize the risk of developing glaucoma.  When you lose vision to glaucoma, you never get it back.

Glaucoma is the second leading cause of blindness in Canada. Even so, public awareness around glaucoma is low. For example, according to a recent survey by the American Optometric Association:

• 90% of respondents think glaucoma is preventable. Only
10% know it's not, but that it's treatable.
• 86% don't know what part of vision glaucoma affects.
• 72% think glaucoma has early warning signs.

The truth is that the only defence against glaucoma is early diagnosis and treatment. People who wait until something noticeable happens to their vision are too late. They have already suffered permanent vision loss.

Regular eye exams are the first line of defense for early detection of glaucoma. Glaucoma is often called the silent thief of sight because it often strikes without pain or other symptoms. That's why it is critical for patients to receive a dilated eye exam from their eye doctor so that eye pressure and and the nerves in the eye can be examined for signs of glaucoma.

Ethnicity affects your risk of developing glaucoma. For example, South Asians have a higher risk than Europeans of developing glaucoma.

Recent studies show that Canadians are not taking basic steps (getting eye exams) to protect themseves against glaucoma. And by the time they are diagnosed, they have already lost vision that they will never get back. It does not have to be that way if you take control of your health and get regular eye exams.

Related Articles
The best protection against glaucoma
Feb 27, 2012

Vision loss from glaucoma - preventable if caught early
Nov 02, 2011

South Asians are at higher risk of glaucoma
Apr 28, 2011
Health warning on eye drop - glaucoma risks
Jan 05, 2012
The myopia epidemic: why it is so dangerous- myopia and glaucoma risks
Oct 12, 2011

Only 38 years old and risking blindness - man suffers permanent vision loss after avoiding the eye doctor for years 
May 24, 2011

Children's eye exams

Did you know that a child should have their first eye exam at the age of six months and then annually thereafter?  Like most medical conditions, eye health and vision problems are much more treatable when caught early.

Good vision in infants is also critical for visual, brain and overall development.  A child with poor vision is prevented from effectively exploring and understanding the world and deprived of valuable brain stimulation.  Studies have also proven what eye doctors already know, that vision problems that persist lead to adult problems such as joblessness, incarceration, lower income and behaviour problems.  Life threatening diseases can also lurk in the eyes of young child.  Read more...
Here is a video of Dr. M. K. Randhawa talking about a patient story from our Vancouver eye clinic involving a five-year-old girl who had been legally blind her whole life - until she came in for an eye exam:

Image courtesy of arztsamui /

Wednesday, January 9, 2013

Can nutrition fight glare, increase contrast, help you see farther, and help you process visual information faster?

This is Viso XC lens coating that fights glare.
Can the right eye nutrition do this?
Much attention has been devoted lately to macular pigment (MP), which is composed of the  carotenoids lutein and zeaxanthin.  Macular pigment is found in a part of your eye called the retina.  In fact, it is found in high concentrations in a part of the retina called the macula.   People who have lots of lutein and zeaxanthin in their system have a much lower risk of developing eye diseases like cataracts and macular degeneration.  Those diseases can cause permanent vision loss and blindness.

The interesting thing is that, in addition to protecting you from very bad eye diseases, recent science has discovered that lutein and zeaxanthin have the following every-day vision benefits...Read more...