Finally! A topic I feel qualified to offer advice about. In my day job as an optometrist, yours is a question that comes up fairly often in a variety of contexts: "Am I better off keeping my glasses on or taking them off for some particular task." I think the best advice posted so far was to talk to your eye doctor. Having said that, it may be helpful to have a better understanding of the physiology underlying your visual concerns and impacting your choices to resolve them.

People need glasses (or contact lenses) for one or more of the following reasons:

Nearsightedness (can't see adequately beyond a certain distance)
Farsightedness (greater effort required to see things at near distances than at far distances--often confused with presbyopia)
Astigmatism (an error in the shape of the eye's lenses resulting in asymmetric or distorted focus)
Presbyopia (the loss of flexibility of the lens inside the eye that occurs with age resulting in decreased range of focus)
Protection (safety glasses or sunglasses)

The best answer to your question depends on to what degree and in what combination you need help with the foregoing as well as your personality type, your budget and the specific demands of the task at hand.

In younger patients, correcting vision with glasses or contact lenses is fairly straightforward. Figure out the patient’s refractive error (that is the error in the lens configuration of the person’s eye when they are looking at a distant target), and then design glasses or contact lenses to correct that error. Then at around age 35 to 45, presbyopia begins to complicate things.

We are born with tremendous flexibility of the lens inside the eye. Our focusing mechanism uses cables called zonules which are attached radially between the perimeter of the lens and a band of muscle tissue called the ciliary body circling the front of the eye just behind the iris. When the ciliary muscle constricts, its circumference becomes smaller and the tension in the zonules is reduced. This allows the lens to bulge from front to back, increasing its radius of curvature and consequently adding focusing power to the lens system in the eye. This process and its reverse are called accommodation and is how a normal eye changes from distance to near focus and back again.

Presbyopia begins at birth when we have 18+ Diopters of accommodation. Unfortunately we lose about 1 Diopter every three years. A little quick math will show that you have blessed little accommodative ability left by your 40’s and none at all by age 60 (then the lens becomes less clear and that is cataract…but that’s another story).

So how does all this affect your decision as to what approach to take for dealing with the particular visual difficulties arising from your vision status and the tasks you are calling on your eyes to perform? Bear with me, just a little more physiology.

I mentioned above that nearsighted people have difficulty seeing things beyond a certain distance. This is because even with the ciliary muscle completely relaxed, and the zonules flattening the lens into its lowest power configuration; the lens is too strong for the length of the eyeball resulting in the image of a distant object focusing too soon, before the light hits the retina. For every nearsighted person, as he moves closer to the object of regard there is a point (called the far point) at which the object becomes clear. The amount of divergence in the light coming from an object located at the far point is equal to the amount of nearsightedness. So, the more nearsighted you are the closer you have to be to something in order to see it clearly. We prescribe glasses or contacts to move the patient’s far point back out to optical infinity and if they’re under 40 we’re good to go. The glasses clear their distance vision and their accommodative ability allows them to adequately focus on near objects. So, when a person who is nearsighted and over 40 starts having difficulty reading the settings on his camera, he can just take his glasses off and use his nearsightedness to make up for his declining accommodative ability.

A person who is farsighted has a different and somewhat opposite situation. His lens system is not strong enough for the length of his eyeball. So the light entering his eye never comes into focus before striking the retina. But the farsighted person has a trick up his sleeve. He can use some of his accommodative ability to add power to his eye’s lens system and bring things into focus. As long as he isn’t too farsighted and is young enough to have adequate accommodative ability, he can walk around all day seeing clearly far away and up close without glasses. Sure, as time goes on his eyes may feel a little tired at the end of the day and the damn phonebook print keeps getting smaller and, “Why do they keep making restaurants dimmer and dimmer.”

Astigmatism comes from a part of the eye, usually the clear dome shaped lens in the front—the cornea, being warped in shape—not spherical. In mathematical terms it is toric, more steeply curved along one meridian than it is along the perpendicular meridian. Astigmatism blurs and distorts focus at all distances all the time. Astigmats can also be nearsighted or farsighted and they also pay that inevitable price of survival—presbyopia.

Now, I’ll go back to your original questions: As you can see from the other posts, there is no one solution for everyone, but here are my thoughts informed by a (too) long career of helping photographers and regular people address these issues.

Wearing glasses vs adjusting the dioptric value of the eyepiece.
1. If you have astigmatism to an appreciable degree you will never be able to achieve a clear view through the viewfinder without your glasses.
2. If you are nearsighted and want to see outside the camera clearly you have to put the glasses back on… On-off-on-off… We call these patients frequent flyers. They’re in once a month or so to get the glasses adjusted and tightened and replace them at about twice the rate of average because they’ve lost or broken them.
3. I’ve always kept my glasses on for photography. Vignetting resulting from the eye being 5 or 10 millimeters further from the eyepiece is minimal. The biggest downside is scratching or smudging the glasses. Keep a microfiber cloth handy.

Contact lenses
1. If you’re caught in the throes of presbyopia, contact lenses are a compromise. I have many patients wearing multifocal contact lenses and many others using monovision where the dominant eye is corrected for distance and the other eye for near. Many patients…but very few serious photographers. The loss of sharpness of vision is a price they just don’t want to pay.
2. Single vision contacts can work if you don’t mind putting on reading glasses.

Glasses options
1. The number one option for all presbyopes is the progressive lens. I didn’t say progressives are the best choice for everyone just that they should top the list for consideration. Progressives like all multifocal lenses for general use have the distance correction at the top of the lens and an increasingly stronger added power below the line of sight to make up for the loss of accommodation. The transition from distance to intermediate to near zones of the lens is smooth and continuous allowing for proper focus at all distances. The rap on progressive lenses is that they have narrow intermediate and near zones and create unwanted peripheral distortion and make particularly susceptible people essentially… seasick or otherwise uncomfortable with their vision. However, today’s digitally surfaced progressives incorporate aspheric surfaces which minimize the distortion. In my practice, those who truly never tolerate the progressive lenses are growing fewer and fewer.
2. Lined multifocals have a distinct ledge in the lens below which is the additional power needed for near. It is an all or nothing transition. As the need for additional reading power increases with age the lined bifocal becomes too strong for fingertip distance viewing. Trifocals add a second line delineating an intermediate power zone.
3. Single vision with multiple pairs of glasses is certainly the least convenient option. People using this option have generally been unsuccessful with the previous two options. I’ll just point out here that single vision (and lined multifocals) do have less peripheral distortion than progressives but not zero distortion. It’s really a case of liking the distortion you’re used to vs something new and different. The fact is that more than 95% of my patients adapt very well to progressive lenses if I’ve done my job properly prescribing and fitting them and they give them a fair try.

Parting thoughts
If you wear glasses, you’re over 50 and do more than an hour or two of computer work at a stretch more than occasionally (and which of us doesn’t?), do yourself a BIG FAVOR and get your optometrist to prescribe you a pair of progressive computer glasses. The Essilor Computer Lens is my favorite lens of this type. It is a progressive lens where the starting point of the progressive zone is higher up in the lens. There is a wide viewing area in the center of the lens for intermediate (finger tip) distance, a tiny sliver of the distance correction at the tip top of the lens and the additional power needed for near below the lens center. These are not for general use and distance vision is definitely compromised. But the ease of viewing multiple monitors and stuff spread around on my workstation without having to contort my head and neck to look through the “right” part of my glasses has been revolutionary for me. In addition to computer use, I wear them all day seeing patients and when I’m working in my woodshop.

Glasses are not cheap and well designed, made and adapted lenses are definitely not cheap. If you are a regular visitor to the UglyHedgehog and have taken the time to read this ridiculously long post, I’m going to bet that you don’t buy the cheapest junk lenses for your cameras from the least reputable vendors. IMHO, you should treat your eyes at least as well as your cameras.

Finally, a story: A patient and friend of mine for many years is now in his late 40’s. I’ve been warning him during his annual exam for several years about his coming visual apocalypse and by his most recent visit it had finally arrived. He is mildly farsighted and had been getting by for distance with his diminishing accommodative ability and for reading by stretching out his arms or digging out a pair of his wife’s old over the counter reading glasses. After I explained his visual status and frankly that things were not going to be getting any better in this lifetime, he decided to try progressive lenses. $600 dollars later (and that’s the “friend price”) he walked out of the office with his new glasses in his pocket. He was back within a week looking kind of edgy. When I met with him in the exam room he wasted no time in telling me how terrible the glasses worked and how he couldn’t keep them on for more than a few minutes. I re-checked all of our work and found no changes indicated. His vision was better than 20/20 at all distances, but the glasses just didn’t feel right to him. I explained that his case is the toughest to solve. Someone who has for years denied any real problem with his eyes, stands up to read the newspaper in the morning, has his wife read the menu in the restaurant and still claims to see the golf ball a country mile is not going to have an easy time adapting to his new and very different glasses. As I told my friend it takes time and perseverance to adapt to a prescription like his, but in the end life is so much better being able to see what you’re looking at. His young son who was along at the second visit put it more succinctly: “You’ve got to toughen up, Buttercup.” Sage advice for all of us.

Having lost my newest eyeglasses and broken one lens on my backups, I am now forced to stop procrastinating and get a new pair. And I am likely going to have to concede and get my first bifocals (sigh).

In the past, I have always removed my glasses when shooting, and adjusted my diopter accordingly.

Do most photographers who wear glasses keep them on while shooting or remove them? And does the bifocal issue have any bearing on this?

Additionally, I am also considering contact lenses, although I have never worn them. How does the bifocal issue factor in for contacts while shooting?

Having lost my newest eyeglasses and broken one lens on my backups, I am now forced to stop procrastinating and get a new pair. And I am likely going to have to concede and get my first bifocals (sigh).

In the past, I have always removed my glasses when shooting, and adjusted my diopter accordingly.

Do most photographers who wear glasses keep them on while shooting or remove them? And does the bifocal issue have any bearing on this?

Additionally, I am also considering contact lenses, although I have never worn them. How does the bifocal issue factor in for contacts while shooting?

Having lost my newest eyeglasses and broken one lens on my backups, I am now forced to stop procrastinating and get a new pair. And I am likely going to have to concede and get my first bifocals (sigh).

In the past, I have always removed my glasses when shooting, and adjusted my diopter accordingly.

Do most photographers who wear glasses keep them on while shooting or remove them? And does the bifocal issue have any bearing on this?

Additionally, I am also considering contact lenses, although I have never worn them. How does the bifocal issue factor in for contacts while shooting?