The development of the technologies used in modern contact lenses is something far more significant than can be dealt justice in this article. We are fortunate today to have an unprecedented amount of options for managing vision defects at our disposal! Glasses and contact lenses can both be manufactured in record time and volume and made available at prices that are within reach, for all socioeconomic levels. This is the first time in history that vision correction has been so easy and effective; it’s important to stress that, while we’re comparing the merits of different types of contact lenses today, neither rigid nor soft lenses can be called a bad choice. They’re simply different solutions for similar problems.
Modern rigid, gas-permeable lenses, what you’ll be buying when you ask for hard contact lenses, are a major step up from previous hard lenses. A hard lens consists of a small, finely shaped piece of a firm, rigid, transparent polymer; the most common such material is polymethyl methacrylate (PMMA). PMMA is marketed under a wide variety of names. For instance, you’re probably familiar with Plexiglas. Plexiglas is PMMA. Treated appropriately before being put into service, PMMA is a durable, cost-effective, and completely safe material and an ideal choice for a contact lens. It is gas-permeable, as with all materials used for hard lenses in the current day, which is important.
Lenses which are non-gas permeable don’t allow oxygen to reach your cornea. When wearing such lenses for extended durations, such as overnight, there’s a real risk of corneal hypoxia. That’s nasty business! Among other things, corneal hypoxia carries a risk of causing corneal ulcers. I’ll spare you the clinical details, but it’s safe to say that there’s a real risk of a permanent decrease in vision. It is a very positive thing that contemporary hard lenses don’t have this problem anymore!
Now, let’s discuss the merits of hard lenses. Chief among these would be their rigidity. Hard lenses sit on top of the eye and don’t necessarily have to conform to its exact shape. As a result, they can correct defects like astigmatism, which soft lenses cannot. If you have astigmatism, hard lenses aren’t just your best bet for contact lenses; they’re your only bet! Soft lenses won’t do the job you need them to. None of the other points matter under these circumstances: hard lenses work, soft lenses don’t. That’s not saying that soft lenses are an inferior product, they just have their pros and cons, much like hard lenses.
Soft lenses, on the other hand, are made from a hydrogel, and most of the market is based explicitly on a silicone hydrogel right now. The hydrogels are semi-solid and very similar to the biological components of your eye in their moisture and consistency. This makes soft lenses more comfortable and easier to get used to. Furthermore, hydrogels, especially the most common silicone hydrogels, have far better oxygen permeability than the materials used in even the most cutting-edge rigid lenses. You can wear an oxygen-permeable rigid lens overnight, but you can wear a continuous-wear soft lens for a month at a time if you absolutely must. The silicone hydrogels are more hydrophobic than some other forms of hydrogels, which slightly reduces their comfort, but they’re still a step up from hard lenses.
What’s more, hydrogels are also offered in a disposable form, so you can simply buy a set of lenses, wear them until the end of their lifespan, and replace them with a new one when that comes to an end. This is far easier than cleaning and maintaining hard lenses, which requires pricey specialized cleaning solutions, and if done wrong can risk causing an eye infection. On the downside, though, soft lenses aren’t as durable as hard ones; as a result, there are environments where it’s simply not possible to wear them.
So, what’s the best choice for your contact lens type? That depends. Talk to your optometrist and consider your personal needs and wants; at the end of the day, the best contact lens is the one that’s most compatible with your eyes and your lifestyle.