What's the difference between daily and monthly contacts?

[optostudent]

I'm an optometry student, and I'm trying to figure out the difference between daily and monthly contacts. A few dailies seem to have the same materials, water contents and oxygen permeabilities as biweekly/monthly lenses of the same brand. Sometimes these dailies are thicker, thinner, or the same thickness as their biweekly/monthly counterparts. So is it just the packaging and care procedures that are different, or is there some other attribute that distinguishes them?

The lenses I'm looking at are:
SofLens Daily Disposables / SofLens 59
ProClear 1-Day / ProClear
1-Day Acuvue / Acuvue Colors

[Judy Canty]

I'm sure that one of your professors could enlighten you.

[PKCRM114]

it really depends on the manufacturer. as B&L found out years ago, you are not allowed to market the exact same lens under different modalities, but depending on the manuefaacturer there are greater or lesser differences. methafilcon, polymacon as well as some other materials haved been use for 2 week, monthly, and full year modalities. but most lenses that have come out more recently have distinct materials for different packaging.

[Judy Canty]

I do not believe this is an Optometry student. More likely, a consumer trying to choose for an online order.

[edKENdance]

Interesting question though.

[fjpod]

can't wait to hear what Chip tells him.

[PhillyEyes]

I do not believe this is an Optometry student. More likely, a consumer trying to choose for an online order.

+1 seems that way

[optostudent]

The headline was intentionally simple to attract attention, but I think it's a legitimate question. I did of course consult a professor some time ago, but he only provided a vague non-answer that wasn't very satisfying, and my curiosity has lingered since. I don't think there's any reason for mystery around the subject. I figured that practicing ECPs who were actually fitting patients might have a better knowledge of specific products and their distinguishing characteristics. I had speculated that perhaps biweekly/monthly modalities would benefit from a protein- or lipid-resistant coating that dailies wouldn't need, similar to how certain silicone hydrogels are treated with a hydrophilic plasma coating. I'm sure there are other bits of manufacturing esoterica that aren't listed in EyeDock or other contact lens databases. Why, for example, did B&L find they couldn't use the same lens for different modalities?

[fjpod]

Optostudent...can you tell me if daily soft lenses are spin cast or lathe cut?

[optostudent]

I don't know, I thought most manufacturers had moved to injection molding.

Update: Yeah, they're molded in various ways, though Ciba advertises something called Lightstream Technology, whatever that is.

[Wes]

I don't know, I thought most manufacturers had moved to injection molding.

I thought so too, aside from gas perms. Maybe it was a trick question.

[drk]

I'm sure that one of your professors could enlighten you.

LOL. So funny. So true.

[drk]

Having said that, either this consumer is an engineer or something or this kid is the real deal. Pretty intelligent line of discussion.

[fjpod]

OK, you gave the right answer. Spin casting and lathe cutting are not commonly used anymore. It was a trick question.

Consumable health care products such as drugs and contact lenses should be used as intended by the maker and approved by the FDA. Otherwise the safety and efficacy of the product is compromised, and the patient and you the prescriber, are put at risk.

[chip anderson]

In some cases it's just marketing. Several large manufacturer's got suied a while back for marketing the same lens under several different regimens. Probably since then they have made sure there are some discernable differences between DW and FW and EW. Over the years the difference has supposedly been water content, thickness, materials and whatever the FDA would give approval for the differing applications. Sometimes it is as little as the quality controls used during manufacture.

Sorry I can't give a better explaination. However I can say that there is a much higher risk of serious and minor complications with EW than with DW (not the lenses, just the application). The other side of the coin is that those practices that do not advocate EW (like mine) will see a serious decline in CL patient load.

Chip