Subjective and objective measures of corneal staining related to multipurpose care systems

An objective, digital-imaging method of measuring corneal staining was evaluated in 24 subjects wearing soft contact lenses. The method was used to compare the clinical performance of common multipurpose care systems (MPS) for soft contact lens care. Subjects used three different MPS, one containing polyquaternium-1 (PQ) and two containing polyhexanide (PX1 and PX2), for 2 weeks in a randomised, single-masked (investigator) crossover study. Corneal staining induced with the three MPS was analysed using an image-processing program (ImageTool, UTHSCSA Version 2, University of Texas, USA). Conjunctival hyperaemia and papillae were also evaluated. The intraclass correlation coefficient was similar with image analysis to that of investigator grading (0.876, 0.879, respectively). Significant differences in staining response were detected using the objective method. There was significantly less staining area with polyquaternium-1 (PQ) than polyhexanide (PQ: 0.12 mm², PX2:0.91 mm²). Inferior palpebral papillae were significantly greater with PX2 than with PQ (1.0, 0.7 (0-4), respectively). The technique was shown to be an effective method of evaluating different corneal staining responses. Bilateral corneal staining in three or more quadrants is useful in the diagnosis of MPS-related staining.