I currently use a mountain bike to commute to work but I am keen to switch to a bike more suited to commuting. I have been looking at road and cyclecross bikes but I am concerned the more horizontal seating position of these sorts of bikes would cause issue with my glasses; specifically, I would end up peering over the top of my lenses rather than through them. Is this a common problem? Do I need to worry?
Yes, in most cases normal prescription glasses sit too low on the nose for the purpose of shielding the eyes in road bike position. And as the speed increases, the need for effective eye protection grows, too. Consider either:
Getting contact lenses, and then you can wear bike specific glasses
Getting bike glasses with prescription lens inserts. In my experience, they are somewhat awkward to handle and not all optometrists will undertake fitting the lenses to what they perceive as nonstandard frames.
Ordinary prescription glasses are sufficient but suboptimal. Although I agree that the best answer is to get bike glasses with prescription lenses or contact lenses, waiting to get optimal eyewear is no reason to avoid using a road bike. I wear prescription glasses and have not yet budgeted for cycling glasses, but I have not had any major problems.
Cycling glasses would make the biggest difference when you are riding above 20 mph. If you normally ride slower than this, or if you don't have the budget, then you can wait until later to get cycling glasses or goggles.
Several months ago, I finally switched to contact lenses, and they have made a huge difference. In particular, the wide field of view afforded by contacts with cycling glasses is much better than what I might hope for in all but the most expensive prescription cycling glasses. I believe that switching to contacts was much easier (and much cheaper) than trying to find prescription cycling goggles with a wide field of view.
I still think it's better to ride than to wait for the perfect solution, but getting contacts and a decent pair of cycling glasses was surprisingly easy. I switched to contacts primarily because of cycling, and I'm glad I made the change.
Eyeglasses, particularly those with relatively "low profile" lenses, will cause problems in an extreme aero crouch position. So it depends on the specifics of your glasses, the bike, and your usual riding position.
I'm extremely nearsighted and wear glasses that are about midway on the round/low-profile axis. I ride a touring bike (ie, a road frame) with a relatively high drop bar. On the hoods I have little trouble with my glasses. On the drops (which I rarely use) I have to tilt my head up a fair amount to see through the lenses, but can when needed. (I can generally see adequately to steer when peeking over the tops of my glasses.)
My bigger problem is seeing through the glasses AND my helmet mirror at the same time. Requires careful positioning of my mirror and some twisting of the head to see behind adequately while on the hoods, and it's a lost cause while on the drops.
I find that using a "Croakie" eyeglass strap helps a lot by keeping my glasses from sliding down my nose.
I've never heard of this being a problem for anyone... but I admittedly stick to the more upright-seated end of the bicycle continuum.
I suggest you try before you buy, of course, but you may also wish to look for a bike with a longer stem, so that if you find you have this trouble, you can raise your handlebars.
Cyclocross bikes should actually be a bit more forgiving of an upright stance than straight-up roadbikes.
I currently use a mountain bike to commute to work but I am keen to switch to a bike more suited to commuting
Commuting is a form of cycling where several aspects of bike fit are important.
Firstly, you do this every day, so whatever position you have should be comfortable.
Secondly, you cannot typically freely choose your route and timing but rather must ride a route where traffic can be present during the commuting time. Thus, you need to have good visibility towards the traffic in front of you.
Thirdly, as you correctly observed, if you use eyeglasses your need to be able to see the road in front of you through the eyeglasses rather than over them.
In my case, the correction is about 1 dioptre so I can use standard glasses with my road bike position where the handlebar is 2 centimeters below the saddle. If I ride on the drops, I don't see the road in front of me through the glasses but rather over them, but this does not matter due to the relatively small 1 dioptre correction. If I need to see road signs, I can always change my position to be more upright.
I have been looking at road and cyclecross bikes but I am concerned the more horizontal seating position of these sorts of bikes would cause issue with my glasses; specifically, I would end up peering over the top of my lenses rather than through them. Is this a common problem? Do I need to worry?
Your concern is valid.
I have relatively mild 1 dioptre correction so I can ride a bike where the handlebars are 2 cm below the saddle with standard eyeglasses. Riding on the tops or hoods provides enough forwards visibility for me through the glasses; riding on the drops does not. That's not a problem, as when I ride on the drops I can always change my position or angle my head upwards momentarily to see road signs.
If your lens correction is relatively mild, I recommend a similar approach. Set up the road bike so that the handlebar level is near the saddle level. If you find this is too high for aerodynamics and you are comfortable with a lower position, you can always increase the amount of time you ride on the drops and decrease the amount of time you ride on the hoods or on the tops.
It is ridiculous to purchase a bicycle with low handlebars and then ride always on the tops or on the hoods, never using the drops position. Road bicycles are intended for varying your riding position. If you always ride on the tops or on the hoods, your handlebar is too low.
I recommend setting your bicycle so that the tops / hoods positions are rather high. Then you have enough visibility through your eyeglasses when you need it and enough aerodynamic when you need it.
When I ride on my road bike, almost invariably I see the other road bike riders riding on the hoods or on the tops. It is extremely rare to see them riding on the drops. Thus, my opinion is that the current trend of road bike handlebar position is wrong. You can always fight this trend by selecting a road bike frame one size larger, setting the handlebar to the uppermost position, and changing the stem to a shorter one so that the large frame size does not cause handlebar distance problems.
Make yourself a soft rubber mould that fits over the bridge of your nose just under your glasses. It will hold up your glasses enough to see perfectly. I use one when riding sports moto bike.
If you are unclear what I mean, put yourself in riding position, look forward then put a finger in the centre of your glasses just under them. It will lift them up enough to see ahead clearly. Hope this helps. (A 3D printer would do the job.)