Preservative free saline guide

The most current version of this page is now in our Knowledge Base

Please click here for the Preservative Free Saline Guide

SAFETY CAUTION: DO NOT USE AQUA NAINA as a substitute for Purilens. It is not cleared for filling sclerals and is not packaged properly for a preservative-free solution. 

What brand of preservative free saline should I get?

NOTE: This video is getting a bit outdated... planning to make a new one soon. 

Overview

Buffered or unbuffered?

Unbuffered salines have two ingredients: Purified water and sodium chloride (a/k/a salt). These are often labeled as sodium chloride solution.

Buffered salines have four ingredients: Purified water and sodium chloride PLUS two ingredients for buffering purposes: sodium borate and boric acid.

Why add buffers to salines? The reason for buffers is to raise the pH to more closely match the pH of our natural tears, and to stabilize the pH so that it doesn't get more acidic after opening the way simple unbuffered saline can.

What's the pH thing all about? The pH of the human eye tends to be around 7. Straight sodium chloride solution (i.e. unbuffered preservative free saline) is acidic, with a pH around 5.5 - or less. Furthermore, without buffers, the pH can drop lower after opening, which doesn't necessarily matter if you're using single-use vials and use them immediately after opening, but for larger packages or bottles, it matters more. Buffered salines aim for a pH around 7, just like the eye, on the assumption this will be more comfortable in the eye.

Based on years of purely anecdotal evidence from scleral lens and PROSE users... for many, the absence or presence of buffers does not seem to make any difference at all and they've happily used Addipaks off-label for forever.

However, for some users, particularly those with dry or sensitive eyes and/or with an extensive history of corneal disease, the acidity of unbuffered saline seems to cause eye irritation, a burning sensation, and/or a tendency to lens fogging. Fogging is an especially pervasive and frustrating problem for scleral lens users.

Therefore, historically, those with the most complex medical histories have tended to prefer buffered salines for use with PROSE and full size scleral lenses. (Unisol 4 and Simply Saline, both now discontinued, were buffered salines as well, with the exact same ingredients as Purilens Plus and ScleralFil.) On the other hand, some doctors may have concerns about the buffers themselves being an irritant for some patients. As with all solutions for scleral lenses, discuss your choice with your doctor, for sure!

Why isn't this better known?

Unfortunately, there is very little published literature about the question of buffered versus unbuffered salines. Here's an article from May 2019 that's worth reading. It reports a case series in which four out of five scleral lens users with dry eye preferred buffered saline. 

What size?

Many patients, especially those fitted with standard scleral lenses and using ClearCare as their only cleaning regimen, do not need a lot of saline to fill their lenses. In those cases, the 5mL sizes such as LacriPure tend to meet their needs the best. For those who do a lot of rinsing, for example, rinsing daily cleaners off PROSE, or rinsing cleaners or disinfection agents off Hydra PEG coated lenses, Purilens Plus tends to be more practical as it has the lowest cost per volume and it's the only one in a bottle you can keep for awhile. Additionally, many people use Purilens at home and single use vials when traveling.

Don't forget!

• Make sure your eye doctor is involved your saline decisions. This is especially important for PROSE and scleral lens users, and for anyone using products "off label".
• If you are using single-use vials, discard them the day you open them. It's not only about the risk of contamination (since they have no preservatives), but we are told that the pH of unbuffered salines drops rapidly after opening.