Selecting Contacts


I am currently in the process of getting contacts. I am planning to research more extensively the pros and cons of contacts and glasses (particularly in terms of my own parameters: myopia with slight astigmatism), and to write them up based on my perspective. I am envisioning (…get it?) a comparison that focuses on vision quality above all else, evaluating things such as spherical aberration, chromatic aberration, peripheral vision, and so on. I am expecting contacts to come out ahead by a substantial margin – and this is ignoring other disadvantages of glasses, such as reflections, fogging, rain-splatters, less comfortable domain-specific eyewear (such as safety goggles) due to doubling up, the need for cleaning (both for hygiene, and to get rid of smudges), the need for adjustment/pushing them back up, etc. I could be wrong though.

At the moment, I am satisfied enough getting contacts because they are strictly superior for sports: well-designed sports goggles with wide coverage may not obstruct vision much, but the bands to keep them stuck to your head reduce comfort to some degree. Contacts give vision correction without the discomfort.

(Incidentally, contacts are also strictly superior for kissing, if that matters for you).

This post

This post is going to briefly outline why, in my opinion, it makes sense for most people to use silicone hydrogel daily disposable contacts over other options, at least based on the research I’ve done. I would recommend you also read this post; I found it very helpful when I was looking into these things.

Why silicone hydrogel contacts: oxygen permeability (Dk/t)

The cornea does not get oxygen from blood vessels, but from air: oxygen diffuses through the tear film covering the cornea. (Even when you are sleeping, the cornea gets oxygen from tears not blood vessels). This means that contacts need to let oxygen through. Oxygen permeability for contacts uses the units Dk/t (Diffusionskonstante per unit thickness, ja?). Good contacts have a higher Dk/t (let more oxygen through), while shoddy contacts have a lower Dk/t.

Hypothetically a company could advertise a very high Dk/t value and make thick contacts that had a lower absolute oxygen permeability than competitors with lower Dk/t values but thinner contacts. The thing is, contact thickness is mostly a function of one’s prescription (by my understanding). This is why the primary thing used to compare contact brands is a relative unit.

Silicone hydrogel (SiHy) contacts have higher Dk/t levels, which is why they are better. Good links:

Why daily disposable

Back in the dark ages of contacts, even people with relatively normal prescriptions were forced to use the same pair of contacts for a long time (my mom told me she had a pair when she was younger that was hypothetically supposed to be worn for an entire year!). Nowadays, most people seem to use either dailies, biweeklies, or monthlies. People with weirder prescriptions (lots of diopters, lots of astigmatism correction) may have less choice in their modality. Highly astigmatic people will also probably have to use toric contacts, and some people will opt for longer-wearing rigid gas-permeable (RGP) contacts to keep costs down, since their prescription might make softer, more-frequently-replaced contacts quite a bit more expensive for them than for the average person.

Extended-wear contacts are not a good idea

These are the kind of contacts that you can hypothetically sleep in, and wear continuously for at least a few days (possibly more). You can improve the wearing of contacts for long periods of time, but it still carries with it extra risk.

I personally do not understand the draw. Even if you can make extended-wear contacts “safer,” they will always be less safe than removing contacts during the night. Full stop. Just because the FDA approves something doesn’t mean it’s actually a good idea to use it.

I haven’t crunched the numbers myself, but I’m assuming that extended-wear contacts (that you use for multiple days) turn out to be cheaper than dailies, and maybe even biweeklies since you don’t have to pay for contact cases and cleaning solutions. This is the only other reason aside from laziness that I can think of for using them.

I am not even planning on using contacts from the time I get up until I go to sleep; as soon as I know that I’m going to be settled at home for the rest of the evening, out will come the glasses. And I’m not going to put contacts in until right before I leave home in the morning (well, actually before shaving, since glasses make shaving harder, but shaving is the last thing that I do before leaving home). And if I’m going to be home in my pajamas on Saturday (e.g.) – never leaving the controlled environment of my house – then I will just use glasses instead.

Minimizing the amount of time you have contacts in your eyes – even extremely oxygen-permeable SiHy contacts – just seems to be the safest, most rational approach to contact usage.

Dailies vs. biweeklies vs. monthlies

Daily disposable contacts have a lot of advantages:

  • They let you avoid cleaning lenses every night. This saves you time every single day, and also means you don’t have to keep track of buying more cleaning solution, swapping out the cases every couple months, etc.
  • They make it almost impossible to have contaminated lenses; assuming you properly clean your hands before putting in dailies, there is simply no opportunity for the lenses to collect bacteria or other microbes. (Note that properly cleaning biweeklies and monthlies makes contamination extremely unlikely, but it is less a certainty, and if you get lazy…)
  • They completely avoid discomfort from protein and lipid buildup on lenses since you are only wearing them a single day. Towards the end of wear cycles for biweeklies and especially monthlies, the lenses will get more uncomfortable due to the buildup of proteins and lipids; it is unavoidable.
  • Dailies allow for a more flexible wear pattern. With biweeklies and monthlies, once you open them, you have to discard them after 14 days or 30 days, even if you don’t wear them all of these days (or even most of these days). You can swap dailies out with glasses whenever you like, however, wearing them as frequently or infrequently as you wish without worrying about being wasteful. (Inasmuch as you are not going against intended use; dailies are arguably more wasteful from the outset).
  • Replacing accidentally torn contacts is more straightforward with dailies: if you tear a contact partway through your wear cycle for biweeklies or monthlies, unless you replace both eyes, you will end up with contacts at different “wear points.” With dailies, you don’t have this concern: you just open up another, and pop it in.

On the other hand, they have a few disadvantages too:

  • They are usually going to work out to be more expensive by a noticeable amount. (Although do keep in mind that you don’t have to keep up with contact cases or cleaning solution for dailies, which will make the total cost difference somewhat less drastic than you might expect).
    • My understanding is that the cost difference for dailies vs. the other modalities is not outrageously large if you have a pretty normal prescription, but may get more prohibitive if you require more specialized contacts due to a weirder prescription.
  • They are arguably more wasteful, and do definitely generate more material waste (plastic packaging, etc.), if that’s something you care about a lot.

In my opinion, the advantages clearly outweigh the disadvantages. I am willing to pay a little more to not have to deal with the hassle of cleaning contacts and to keep contamination risks as low as possible. For what it’s worth, when I went into my fitting appointment and waved around my notes, my doc laughed and said I did his job for him: he always recommends dailies for the reasons above.

Other things

I asked my doc a couple questions at my fitting appointment, and here’s what he said (more or less – this is a paraphrase from memory):

Is it important to have numbers or something printed on the contacts to put them in the right way?

Doc: No. If you are putting them in the wrong way, they won’t feel right, for one thing. But more importantly, you can look at the edges of the contact balanced on your finger: if they are straight like a bowl, it is the right way; if there is a “lip” (curvature outwards), then it is the wrong way.

Is there a particular type of contact (e.g, soft dailies, RGP) that is best for people new to contacts?

Doc: Soft dailies is what I always try to start people with.

Are there ever people who get too wigged out by sticking things in their eyes and end up not being able to use contacts? (nervous laughter)

Doc: No, not usually.

Closing thoughts

I’ll probably have more to say once I actually get contacts and wear them for a while (I have not even worn them as of yet, so all this is a bit theoretical at the moment). I don’t anticipate that my views will change much though.


comments powered by Disqus