Effect of the osmolarity change in multipurpose solutions induced by an improper contact lens case cleaning procedure

- Daily contact lens (CL) case air-drying increases solution osmolality.
- Higher osmolality causes more stinging and discomfort for CL wearers.
- Hyperaemia and bulbar/corneal staining also increase.

PurposeTo determine whether variations in multipurpose disinfecting solution (MPDS) storage osmolarity from inappropriate contact lens (CL) case cleaning affect ocular surface integrity and wearer comfort.MethodsThere were twenty contact lens cases (study CLCs) in the study group. Ten were filled with ReNu Multiplus® and 10 with SoloCare Aqua™ (MPDS-1 and -2, respectively) and kept closed for 8 h; the cases were then emptied and kept open for air-drying for 16 h. This procedure was carried out every day for two months. Storage solution osmolarity was measured on days 0, 15, 30, 45 and 60.Ten subjects were then fitted with both month-old lenses stored in the study CLCs and with new lenses stored in new cases with fresh solution for 24 h (control CLCs). Symptoms, tear osmolarity and percentage of subjects whose conjunctival hyperaemia and ocular surface staining scores changed were determined after 1 h of wear.ResultsStudy CLC osmolarity increased in both solutions after two months (p < 0.05). For MPDS-1 there were differences in stinging between study CLCs and control CLCs after 10 min of CL wear (p = 0.04), and in comfort after 10 (p = 0.035) and 60 min wear (p = 0.042). Significant (p < 0.05) differences between study CLC and control CLC groups were also found for MPDS-2 in limbal hyperaemia (study: 50% change; control: 0% change) and bulbar and corneal staining (study: 80% change; control: 20% change).ConclusionThe stored-MPDS osmolarity increase caused by air-drying the CLCs could affect the ocular surface. This increase might reduce lens wear comfort.