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THE EFFECT OF pH WHEN FILLING SCLERAL LENSES FOR DRY EYE

Patients who have severe ocular surface disease sometimes rely on scleral lenses to help manage their vision and symptoms of irritation and dryness. An important component of scleral lens wear is the fluid that is used to fill the lenses prior to application, because that fluid interacts with the ocular surface throughout the entire day.

Assessing the Effect of Filling Solution pH in Dry Eyes

Sterile preservative-free saline solutions come in buffered and non-buffered formulations with a range in pH. We performed a case series to assess whether the pH of scleral lens filling solutions affects subjective comfort in patients who have dry eyes. First, the pH of common, preservative-free 0.9% NaCl scleral solutions were measured with an Apera pH meter three times using different vials and bottles (Table 1).

TABLE 1 pH OF COMMON SCLERAL FILLING SOLUTIONS
SOLUTION pH
Addipak 5.3
Modudose 5.6
Lacripure 6.5
ScleralFil 7.3
Purilens 7.4

Five healthy patients between the ages of 20 and 42 were included in this case series. All patients had symptomatic dry eye and were using no treatments other than artificial tears. A clinical evaluation for ocular surface disease was performed with fluorescein and lissamine green staining, and the patients completed the Texas Eye Research and Technology Dry Eye Questionnaire (DEQ). All patients were then fitted with Art Optical Ampleye scleral lenses with a 15.5mm diameter. They wore the lenses for at least 10 hours a day and cleaned and stored the lenses only in Unique pH (Menicon) GP multipurpose solution.

Three of the patients filled their scleral lenses with a buffered filling solution (ScleralFil, Bausch + Lomb) for the first two weeks, and two filled their lenses with non-buffered saline solution (Addipak, Teleflex) first. After two weeks of lens wear, the DEQ and the dry eye evaluation were repeated. The patients then switched filling solutions. At the end of four weeks, the DEQ and the dry eye evaluation were repeated once more, and patients were asked to compare the filling solutions. Patients evaluated comfort on initial application and at the end of day.

There was no difference in fluorescein and lissamine green staining between baseline and after use of either filling solution. The DEQ showed a significant improvement in dry eye symptoms with scleral lens wear regardless of solution used (Figure 1).

Figure 1. The mean DEQ score prior to scleral lens wear and following two weeks of buffered versus non-buffered saline solution.

When asked which filling solution they preferred at the end of the four-week period, four out of five patients reported better end-of-day comfort with the buffered filling solution. All patients reported that they would continue scleral lens wear to help manage their dry eye symptoms.

Clinical Implications

Our case series shows that patients who have dry eyes and who wear scleral lenses may prefer filling their lenses with a buffered versus a non-buffered filling solution. This may be due to the large difference in pH between a non-buffered solution and that of the natural tear. Research needs to be done to evaluate the effect of filling solution pH on normal eyes as well as on eyes with other corneal diseases/degenerations. CLS

The authors wish to thank Dr. Emily Cheng for her work on this case series.