Not all salines are the same!!
Saline is an integral part of contact lens practice, being used regularly by most people who wear contact lenses. Its most common use is as a rinsing agent, either after the contact lenses have been cleaned by a surfactant cleaner or prior to insertion of a contact lens onto the eye. As I have noted in previous blogs, under no circumstances should any type of water be used on contact lenses. Studies continue to show that there is an increased incidence of corneal infections associated with the use of water on contact lenses. These infections are caused by Acanthamoeba, a parasite commonly found in tap and other sources of water. This infection, called Acanthamoeba keratitis (AK), can be very difficult to treat and can lead to severe and permanent loss of vision. Quite simply, water should not be used for cleaning, rinsing or storage of the contact lenses.
More recently, with the increase in prescribing of the larger rigid (scleral) lenses – which are fitted as a sealed system – saline has been used to fill the space between the back surface of the lens and the cornea. These lenses are filled with saline prior to insertion and this liquid reservoir prevents the formation of air bubbles under the lens and provides lubrication for the front surface of the eye during contact lens wear.
The saline used for contact lens wear comes in two forms. It can either be in a bottle or in unit dose form. The multidose bottle of saline must incorporate a preservative which minimizes the risk of microbial contamination. The unit dose form dose of saline does not need to include a preservative so it can be unpreserved saline. In the bottle form, only preserved saline is permitted to be used with contact lenses. Unpreserved saline in a multidose (bottle) form is not allowed to be used with contact lenses and has to be labelled as such ‘Not suitable for use with contact lenses’. The reason for the ban on the use of bottled unpreserved saline with contact lenses is a long story dating back to late last century which I’ll cover in a future blog.
For patients who use saline to fill their scleral contact lenses prior to insertion, it is critical that no preservative be trapped between the contact lens and the ocular surface, as during the many hours of contact lens wear this preservative will cause significant irritation to the ocular surface resulting in marked discomfort for the patient. Therefore, for these patients it is important that they use either an unpreserved unit dose saline or a bottled preserved saline that incorporates a preservative which breaks down when the saline is released from the bottle. The only such product available in Australia at the present time is the Lens Plus OcuPure Saline from AMO. The patented ingredient OcuPure is a preservative that transforms into natural tear components in the eyes when exposed to light, so providing the comfort and performance of a preservative-free saline. Hence, the Lens Plus OcuPure Saline is the only bottled (multidose) preserved saline presently suitable for use with scleral lenses.
On many occasions, my colleagues and I have seen patients who have previously been wearing scleral lenses without problem suddenly present with sore eyes associated with contact lens wear. This is often due to the patient mistakenly using a bottled saline or multipurpose contact lens solution that simply is not suitable for filling the bowl of the scleral lens prior to insertion. An important example where patients often get confused is the Reclens unit dose unpreserved saline and the Reclens preserved saline that comes in a bottle. Both are good products. However, only the unit dose Reclens is suitable for use with scleral lenses. Using the bottled (multidose) form for insertion is not acceptable as the preservative in this saline will get trapped under the sealed fit of the scleral lens and cause irritation to the eye.