The lenses of both my eyes developed cataracts over the last couple of years, causing my vision to become blurry even with glasses. It was getting so blurry that I was on the verge of losing my license to drive. Here's what a typical scene, the grocery store, looked like to me:
Are the eggplants $1.39 or $1.59? Are those zucchini or cucumbers? Is the guy in the background, with the blue helmet, a friend or neighbour? I couldn't say.
Cataracts are age-related, like grey hair and wrinkles. Nearly everyone will develop cataracts eventually; about 40% of the population shows signs at age 50, about 90% by age 80. If you live long enough, you'll probably get them. The proteins of the eye's lens become cloudy and optically inhomogeneous, making vision foggy and blurry. Bright lights against dark backgrounds get a 'haze' around them, as in the illustration to the right.
There are thought to be many causes of cataracts, with UV radiation from sunlight high on the list. I certainly enjoyed a lot of sun in my life, especially when young. I guess I should have worn UV-blocking sunglasses more often.
Prior to the onset of cataracts, my vision with glasses was excellent, with above-average visual acuity. In my mid-forties, my myopia even improved slightly (see graph below, of my right eye). But at age 53, things began to deteriorate -- my myopia worsened, and new glasses didn't entirely fix it; my vision started becoming uncorrectably blurry. I didn't recognize until years later that the sequence is typical of the development of cataracts (even that slight improvement in my myopia, in my mid-forties, was also apparently related to the development of cataracts).
The chart below is for my right eye, and my left eye was similar. The chart shows my need for refractive correction versus my age, up to the time of my cataract surgery. Zero on the vertical axis is vision without need for glasses (ie., no refractive error); negative numbers are myopia (near-sightedness). When my required correction was -7D, my glasses were getting pretty thick.
What the chart doesn't show is loss of acuity. In concert with those refractive changes, I was also losing the ability to see clearly, even with glasses. Finally it was getting bad enough that I was on the verge of not being legal to drive. At that point, my ophthalmologist said my cataracts were 'mature' and recommended cataract surgery (influenced, I gather, by provincial guidelines).
Another symptom of the cataract development for me was multiple images per eye, faint and slightly offset, and arranged in a triangle, as illustrated in the figure to the right. This might be unusual or not normally mentioned by patients as none of the specialists I was speaking with seemed to recognize it as a cataract symptom. Why the triangular arrangement? I wonder if it has something to do with the tripartite arrangement of our embryonic eye lenses. Maybe the protein changes in the eye related to cataract development were spatially inhomogeneous and thus gave rise to the optical effects.
Without intervention, cataracts can get worse until the eye is so cloudy and white that vision is completely lost. Lots of people were, in history, and are, in the Third World, blinded by cataracts. Cataracts can also develop so slowly that they never get bad enough to justify the risks of surgery.
Cataract surgery involves replacing the natural lens of the eye (which does 1/3 of the focusing work, the rest being done by the cornea) with an artificial (acrylic) lens six millimeters in diameter (see photo to the left; the two legs hold it in position).
Surgery for my eyes was performed in Ottawa, where I live, at the Riverside Hospital, which reportedly does the most cataract surgeries of any place in Canada. My left eye was done first, followed three weeks later by the right eye -- only one eye is done at a time for safety. After about three hours of preparation involving about a half-dozen staff and specialists, the operation itself took about ten minutes and was done with local anesthetic.
Briefly, the way the operation works is this: Starting three days prior, eye drops (an antibiotic and an anti-inflammatory) are applied four times daily. A hour prior to the surgery, eye drops dilate the iris. With me lying on a stretcher under bright lights and with optical equipment aimed at my eye, the surgery starts with a tiny 2 mm incision made through the side (base) of the cornea, giving access to the lens capsule. An ultrasonic device is inserted into the lens that turns it into mush, and then the lens bits are pulled apart and flushed out. When the lens capsule is empty, a syringe-like tube is used to insert the implant, rolled up, into the lens capsule. When it has been injected and is in the lens capsule, it unrolls, with two 'legs' that hold it in place, centered on the eye. The capsule is 'topped up' with saline solution (I guess), and the surgery is complete -- the incision in the cornea heals in a few days. Eye drops are applied four times daily for the first week containing an antibiotic, anti-inflammatory, and steroid, then only the anti-inflammatory for another three weeks.
The day I went, 14 other people were also having an eye done. I was the youngest in the batch, and most people seem to have years between one eye and the other (I gather my cataracts progressed quickly). My surgeon had worked on over 18,000 eyes at that point.
My vision immediately after the operation was cloudy, probably because of a gel they apply. My surgery occurred in the late afternoon, and they gave me an eye shield to wear that night to guard against pressing against or rubbing the eye while sleeping.
Next morning, when I took off the eye shield: Wow! I could see more sharply than I could ever remember! That felt really great.
Most surprising to me was how clearly I could see peoples' faces. I had forgotten how much non-verbal communication goes on out there. The world is a beautiful, beautiful place, especially when in sharp focus.
Cataracts also make the natural lens change colour slightly. I hadn't noticed this gradual colour shift in my vision over the years of cataract development, but after the first operation, when I had still one eye with a cataract as a reference, it was obvious. The photos below simulate what I saw out of my two eyes, one with the new lens and one still with the cataract:
Notice the luxurious green grass in the left photo, and the bright blue sky of the right. Question: Which photo is 'real' and which photo simulates vision with a cataract?
Answer: The right-most photo is most 'real'. Cataracts impart a yellow colour cast (which progresses toward brown, I'm told). The yellow enhances greens and muddies blues. So with my new manufactured lens, the world seems more blue, 'cool', and crisp.
During the few weeks between surgeries, when I had one eye still with a cataract, I used a computer screen and Photoshop to try to record and quantify the colour cast imparted by the cataract, compared with the newly-improved post-surgery eye. I set up two grey squares of colour with a spacer-panel in the middle (below), then put my face close to the display with each eye looking at its own colour square, and adjusted the blue/yellow balance of one square until the two squares appeared to match. The result was so surprising that I tried confirming it by reversing it, to see if altering the cast for the other eye made a difference. Below are the results -- when I had just one cataractous eye, both of the two end-panel pairs below appeared equally grey (when viewed one panel per eye, ie., close up so that each eye could only see its panel). Only the right eye had a cataractous lens at that point.
Accommodation vs Age (source) (after age 55, it stays at about 1 D)
As we get older, we lose the ability to change the focus distance of our eyes. We start life with a fabulous range of about 14 dioptres, but as we age our focus range -- our ability to 'accommodate' -- decreases more-or-less linearly until it hits one dioptre around age 50, where it stays for the rest of life. The chart to the right shows accommodation ability vs age, drawing on data from several hundred people.
The new artificial lenses now in my eyes have no ability to accommodate -- they are fixed at one focus distance. That condition is almost the same as with a natural lens more than 50 years old.
My eyes still have the muscles that would do the focusing; if the implant could respond, maybe I'd have the focus range of a teenager. But the lens can't respond, not even one dioptre like an aged natural lens, and so I'm stuck at just one focal length. The surgeon chooses what power of lens to implant based on measurements of my eye (using a laser and ultrasound), and on my desired outcome. My choice was for my eyes to focus at infinity, to give me perfect distance vision without glasses. That's a big decision, because it's not easy to change implants (once the lens unrolls in your eye, it requires a much bigger incision to get it out).
Now I have reading glasses with progressive lenses, which have varying strength depending on where one looks through them (thus I've joined the people who tilt back their heads to see through the bottom of their glasses to see close). In situations requiring just one focal distance, it's more comfortable to have fixed focal length glasses, so at the computer and when reading, I use dollar-store reading glasses. At the computer, I've got the screen about 80 cm away, and am using +1 D glasses. For reading, I use +2 D. For close work, I use +3.25 D. A bonus with presbyopia (as opposed to myopia) is that plus-power lens magnify, whereas minus-power lens shrink things; so with reading glasses (and perhaps thanks to the aspherical IOL and my now-cataract-free lens), text is sharp, bold, and high contrast. It's a pleasure.
People with developing cataracts may find this section interesting, but if you are younger, by the time you need cataract surgery, let's hope researchers (maybe you!) will have developed even better solutions. You might want to skip down to the Summary section.
In 2010, here were my intra-ocular lens (IOL) choices:
Another option is to have different types implanted, one in each eye -- which could be different technologies, or more commonly, different refractive powers. When the power of each eye's lens is different, the arrangement is called 'monovision'. One eye's lens is set to focus at distance (infinity) and the other eye's lens is set for reading (eg., +3 D, ie., 33 cm). It works because the brain ignores the out-of-focus eye, but it means that only one eye is in focus at a time (hence the 'mono' in 'monovision'), reducing stereo vision and reducing the opportunity for one eye to help the other eye (this gets more important as one ages because 'floaters' in the vitreous often drift by, affecting vision in that eye). Many people wear contact lens using this monovision technique to cope with presbyopia as they approach age 50; for them, it is natural to continue that strategy with IOLs.
I love sharp, binocular vision -- I guess I could be said to be 'obsessed' with vision quality --and I don't mind wearing glasses, so I went with the single focus, aspherical IOL from Abbott, called Tecnis ZCB00 in both eyes, with powers chosen so that my resting focus would be at infinity.
This means I am much like a normal emmetropic person at age 50: I can see distance perfectly but need reading glasses; I can't comfortably read labels, eg., at the grocery store, or menus at restaurants (though in bright light, with my iris small and thus performing like a pinhole lens, I can almost read normal-size print). With these lenses, and with glasses for reading, I have great visual acuity (perhaps better than natural, thanks to the aspherical lens).
When I was near-sighted, presbyopia for me wasn't big deal; as a myope, I just looked under or over my glasses to see close. But after cataract surgery, I'm now an emmetrope, with eyes that focus (only) at infinity. My reading situation is quite changed. Whereas before to see close I was able to simply take off glasses, now to see close I need to put a pair on! So presbyopia is now slightly more of a nuisance for me than it was when myopic. On the other hand, now I often don't even bother with glasses (since I only need them for reading and close work), for example, when exercising or play sports, swimming, waking up at night, sleeping under the stars.
The surgeon uses measurements of the eye to decide what power of IOL to implant. It's not entirely accurate, with outcomes apparently plus/minus about 0.25 D. It's better to be nearsighted (helps with reading) than farsighted, so my surgeon aimed for a refractive error of -0.25 to -0.75 D, which in bright light is nearly indistinguishable (due to the pinhole effect) from 0 (ie., focus at infinity). I got lucky: My outcome was 0 the day after surgery, and I measured my distance acuity (using this test), without glasses, as 20/12 or 20/13 - wow! But as the eye healed, it changed slight and is now about 20/20. My right eye, which has mild astigmatism, has an outcome of -0.75 with +0.75 D of astigmatism, giving an acuity without glasses of 20/23. Glasses, of course, can correct those small errors, but in bright light with a small iris, that small correction is unnecessary (makes no difference).
Studies say that as we age, our cornea usually slowly changes. On average, we become hyperopic at a rate of about 0.5 D per decade from age 40 to 60. I like what I've got now, so I hope not much changes.
Also with age, apparently our cornea starts developing higher order aberrations not easily corrected (though maybe laser surgery, which reshapes the surface of the cornea, can deal with that?). This information fits with what older people told me when I spoke with them in the ophthalmologist waiting room about their vision; their visual acuity outcomes after cataract surgery were not as good as mine; maybe they had higher-order corneal aberrations.
(For more info, here's a search for age-related vision changes.)
Mock-up of a faint halo seen in low light
(occurs only when my pupil is dilated)
Night vision with the lens I chose (aspherical, fixed focus Tecnis ZCB00) is good-to-perfect until my pupils open wide. Then there is sometimes a single, almost circular halo, at an angle of approximately 5 degrees from the light source (see a mock-up to the right), with a bit of radial glare out to the halo radius. The halo and the glare are modulated by pupil dilation. For example, a dim distant headlight may have the halo until the approaching headlights are bright enough to close down the pupil. Some lights are too dim to generate a noticeable halo, and bright lights constrict the pupil and thus eliminate the halo; only lights 'in between' generate the halos.
In normal driving conditions, the light of my own headlights on the road is usually enough to keep the pupils small enough to suppress halos and thus vision is excellent.
I'm not sure what generates the halos. There is talk on the web about glare from the edge of the IOL, but I find things are in focus outside the halo.
Usually the halos don't grow to being complete circles. Halos start from the top of my visual field, differing slightly between eyes. If an obstruction close to the eye is moved laterally, slowly toward the point source, the halo is gradually blocked, starting from the side opposite the obstruction, well before the point source is obstructed. I take this to be due to the image reversal that occurs in the eye.
Non-point-sources, such as a screen in a theatre, also produce 'halos', but in that case it looks more like broad border (as you'd expect). Halos in such low-light conditions are more likely for me.
These halos could be a 'temporary' feature that disappear with age. As we age, our pupils do not open as wide (so we can't see as well in the dark; more info). This probably explains why when sharing experiences with other cataract patients, all considerably older than me, with the same IOL type, no one else reported night-time halos -- likely their pupils don't open wide enough. So I expect the 'halo effect' won't be with me forever.
Whatever artifacts, I'm told people become accustomed to them. I don't consider them to be a significant problem (certainly not comparable to the benefits).
When looking through optical instruments (eg., microscope or binoculars), there seems to be a smaller 'sweet spot' than with natural lens; if not aligned, there is distortion visible on the edges of the visual field. I've only noticed this when looking through instruments.
Occasionally, if the light is at a particular angle, the IOL appears to 'flutter' in response to an eye movement.
Floaters seem less noticeable. I attribute this to now-excellent stereo vision, providing the brain with redundant visual information that it can use when a floater goes by in one eye.
The surgeon uses a microscope (with two auxillary eye-sets for observers) with a very bright light; though it was quite uncomfortable, one must stare at the light to keep the eye positioned. For days afterwards, I saw a wine-red colour cast in my central vision area in dim light upon awakening, quite strong the first morning and diminishing over about a week.
With progressive lenses, it's necessary to turn your head to see, but with IOLs (and, of course, contacts), it's easier to just turn one's eyes. After the first operation, after a day or two of wild enjoyment of the novelty of 'perfect vision' with no glasses, I noticed my eye muscles aching, as if overworked! That cleared up in a day or so.
As mentioned, the surgery only takes a few minutes, and there are videos (eg., on YouTube, eg., this one) that show an entire operation. Watching that video made me queasy -- it was easier to experience the operation from the 'inside'.
It's fabulous being able see sharply again, and being able to do it in most situations without glasses is a bonus. I'm grateful to all the researchers and engineers who made this technology available, to my Ottawa ophthalmologist/surgeon (James Cameron) for his judgment and skill, and to the staff at the hospital -- and to my fellow Canadians, whose health care system makes this available to everyone. It's a life-changer. One can undoubtedly get by without vision, but I'm sure glad to be able to see well again.
My vision is still great, and I'm pleased with my choice of aspherical lenses focused at infinity. I usually wear glasses with progressive lenses for reading, but aside from reading can see perfectly without glasses.
About seven years after the cataract surgery, one eye developed a faint 'second cataract', caused by cells growing on the normally-transparent membrane at the back of the lens capsule. This condition, called 'posterior capsule opacification', apparently develops eventually for about 20% of cataract surgery patients. Again, researchers and technologists have developed a fix: A YAG laser is used to cut a hole in the membrane in a procedure called a 'capsulotomy'. I walked into an office, sat in front of what looked like yet another eye-testing instrument on a desk between me and the surgeon, looked into it, and about 15 seconds later, after a few clicking sounds, it was done, painlessly, miraculously. The surgeon-without-a-knife guides the laser to cut a hole in the posterior capsule membrane. I'm back to having great vision!
Here's excellent general information about cataract surgery: Canadian Ophthalmological Society evidence-based clinical practice guidelines for cataract surgery in the adult eye
There's lots of information about the various lenses on the internet, from the manufacturers and eye surgeons, but most of it is superficial, more like marketing (eg., for my lens, the manufacturer's page starts: "Cataract surgery is more than just the most common surgical procedure in the world. It's an opportunity to rejuvenate your vision to how it was when you were 19."). The best source of data I found was the US FDA web site, which publishes the results of studies they require be done before allowing the manufacturer to sell the lens (so where's Canada on that, and making it public? The FDA data was the most useful data I could find.). Of course new products will likely be developed, but probably the FDA site will still be a good place to look. Here are the FDA pages for the two lenses:
Safety and Effectiveness Data, Tecnis Multifocal Interocular Lens (2009)
Safety and Effectiveness Data, ReSTOR Multifocal Interocular Lens (2005)
(The single-focal IOLs are more mature technology and apparently thus don't require recent data submissions; much applies from the studies of multi-focals, however.)
As you can read in those FDA report statistics, not all cataract surgery works out well; a few percent of people end up with no improvement or vision barely qualifying for driving (20/40), and there's even a risk of losing vision. So it's a serious surgery with risks. Although the view in the photo at the top of this page is blurry, I was aware that vision even at that level would be a dream for the many people with severe vision problems, so I was content to put off surgery until my ophthalmologist thought the risks and health system costs were justified. On the other hand, there are web sites apparently so confident about results that they promote surgery as a reasonable response to even just presbyopia (implanting multi-focals), saying "why not have perfect vision?"
Cataract surgery in Canada is covered by provincial health care, and of course that means the province has a say in when you get it. That was fine with me, both practically and philosophically, but if that doesn't suit, there's a place in Toronto (Herzig Eye Institute) that offers surgery on a private clinic basis, for about $4000 per eye. I considered it but it would have required several trips to Toronto and, although hard to evaluate, after discussing it with my ophthalmologist, it seemed that the public system available in Ottawa, my home town, would be quite fine. Canada's standard of cataract eye treatment seems as good as anywhere; there was no need to pull a "Danny Williams" move (you'll recall Williams, as premier of Newfoundland, went to the US for heart surgery, apparently not confident in care he'd receive in his own province) (but if you are interested, Spain seems to be a hot-spot for eye treatment -- and eye-damaging sun -- coincidence?).
A Toronto-area friend needed cataract surgery about the same time as me, so we did research together. He decided on a ReSTOR multi-focal IOL in one eye, and went to a private clinic (for cataract surgery and excimer laser treatment to correct astigmatism). His outcome was as promised, and he loves not having to wear glasses in most situations, which was his priority. As described above, I decided to go for single-focal aspherical to maximize vision quality at infinity, at the cost of needing reading glasses. Both of us are quite satisfied.
Here's interesting information about the cost to our public health system for cataract surgery: Estimates of the costs of cataract surgery, from www.eyesite.ca/english/program-and-services/policy-statements-guidelines in 2010.
Here's a web site with a good-quality test of visual acuity that you can do at home.