Eye exams & cheat-sheets


DRUG BUST by Alan Cassels

As someone who sees himself as acutely sensitive to potentially unnecessary medical treatment, it was only when I sat in front of a health professional that I realized a startling and embarrassing truth: it is extremely tough to practise what you preach.

I recognize I might not be an ordinary patient. For the book I’m writing on medical screening tests, I have interviewed experts, pored over guidelines created by dependable and authoritative bodies such as the United States Preventative Services Task Force and spoken to many patients.

This research has led me to an irrefutable conclusion: most people are naked in the medical screening marketplace. A dilemma, yes, but it also makes the raison d’être of my book clear. Consumers need to do their research and be armed with some vital questions when facing an offer of medical screening. Ignorance and screening tests can be a deadly combination so you must face such tests with your eyes wide open.

Speaking of eyes, I was recently at an optometry clinic having a routine eye exam. It was the standard optometrist stuff, with various rows of letters flashed up on the wall and me trying to prove to the optometrist that my eyesight hadn’t deteriorated since my last visit. So far so good.

But then he pulled out a tool, about as big as a telephone handset. It set my Spidey senses alight; was I was about to walk the gangplank of a screening test? Trevor, the optometrist, was reassuring. He was going to use a tool I later learned is called a non-contact tonometer to shoot a puff of air into my eyes. Our conversation went something like this:

“What’s that for? Are you doing a screening test on me?”

“Yes, it’s a screening test. It makes a little puff of air against your cornea and measures the pressure of the fluid cycling inside the eye.”

“So why do you need to know the pressure inside my eyeballs?”

“It’s just a little test to see whether the fluid in your eyeball pressure is normal or not. High pressure can lead to glaucoma, which can lead to blindness.”

“Whoa… Are you telling me you’re gonna test my eyes with something that might tell me I’ve got a chance of being blind in the future? What if my eye pressure is high?”

“Then we’d talk about what it could potentially mean and we’d do a few other diagnostic tests. Other things could cause raised pressure in your eye so we’d do more tests to rule out those things. We’d also check out the visual field. If glaucoma damage was happening, you’re going to find it symptomatically in the visual field.”

“So this is just the first slice, right, this screening test?”

“Yeah. By the way, why are you asking so many questions?”

I told him about my research and the subject of the book. I told him I know of many people hurt by simple ‘screening’ tests. People need to ask the right questions and I ashamedly admitted it’s hard to think of the right questions when you’re on the spot like this.

“It’s a pretty simple test, just a puff of air into each eyeball,” he said reassuringly.

I was definitely stalling for time, scratching my brain for more questions and eventually doing what most people do when offered a medical screening test. I gave in. He shot a puff of air in each eyeball. “Your pressure is normal,” he said and then carried on with the rest of my eye exam. Whew! ‘Normal.’ I like being normal. But what if I wasn’t?

What a piercing moment of self-realization. I was thinking about all the stories I’d heard of people getting PSA tests or mammograms, with absolutely no inkling of what they were getting into. Those tests are also simple, but when abnormal test results come back, patients are often flung headfirst into life-altering dilemmas.

But Alan, chill. It was just a puff of air to the eyes. Yet the feeling I was doing things back-assward remained. How stupid is that? Agree to the test then do your own research? Wrong, wrong, wrong.

After the eye exam, I started researching tonometry and found, not surprisingly, it wasn’t a slam-dunk. One study said finding and treating ocular hypertension reduces the risk of developing glaucoma compared with a control group. Others said there wasn’t much evidence to support it as a screening tool. Like most screening tests, a strong whiff of uncertainty hung in the air.

My conclusion was absolute: I need a cheat-sheet for the next time someone offers me a screening test, something that cuts to the basics. So here are six simple questions anyone facing a screening test should be asking. (The answers provided here are specific to the eyeball pressure test.)

1. Is this screening test recommended by a quality, independent body such as the United States Preventative Services Task Force (USPSTF)?

While the USPSTF said the tonometry tests can find increased intraocular pressure (IOP), it also said the jury is still out on the evidence. Earlier detection of high eyeball pressure is not definitive in reducing the possibility you will have vision related problems in the future.

2. Can anything be done if the test does find high eyeball pressure? (Or whichever condition the test is designed to find.)

Yes, they can do other diagnostic tests to see if there is damage to the optic nerve and they can prescribe drugs, usually eye drops. This does not imply all patients with borderline or elevated eye pressure should receive medication. Higher than normal eyeball pressure is only a “risk factor” for glaucoma and many people with higher pressures never develop glaucoma. In fact, 25 to 50 percent of people with glaucoma have normal eye pressure.

3. How prevalent is the disease in question in people like me? In this case, how likely is it that someone my age is heading for glaucoma?

According to the World Glaucoma Association, glaucoma is the second most common cause of blindness worldwide but only about seven percent of all patients with glaucoma are younger than 55 years. The biggest risk factor is being old.

4. Is the test accurate?

There is uncertainty over the accuracy of tonometry because intraocular pressure changes throughout the day and the test can’t account for differences in thickness and curvature of the cornea. Operator error can always come into play. One study said the method of non-contact tonometry has a sensitivity of 22.1 percent and specificity of 78.6 percent. Sensitivity is the percentage of screened people who have the condition and are correctly identified as such. Specificity refers to the percentage of screened people who don’t have the condition and the test tells them they don’t have it.

5. Who is pushing the test and why?

Groups like the Glaucoma Foundation and the Canadian National Institute for the Blind recommend routine eye pressure checks. Drug companies that make eye drops and tonometer manufacturers would obviously like to promote this screening as much as possible. Tonometer makers promote things like World Glaucoma Day by offering free screening events and such events showcase their products. The drug maker Pfizer funds a campaign called All Eyes on Glaucoma, which recommends regular tonometry screening. Pfizer sells latanoprost or Xalatan, eye drops designed to reduce eyeball pressure.

6. If I have a positive test, what does the downstream medical treatment look like?

Not everyone who has higher than normal eyeball pressure needs eye drops. The drops can be expensive and the rules for when you should take them can be confusing. Side effects of the drugs include changes in eye colour, stinging, blurred vision, eye redness, itching and burning.

Facing an upcoming screening test? Write down these six questions on a piece of paper and stick them in your wallet. These eye exams seem simple, but not every medical screening test is as simple as a puff to the eye. It’s a good reminder you need to go into screening with your eyes wide open.

Alan Cassels is a drug policy researcher at the University of Victoria and the author of the forthcoming book Seeking Sickness, which focuses on the world of medical screening. Read more of what he’s writing about atwww.alancassels.com

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