Mechanisms of superficial micropunctate corneal staining with sodium fluorescein: The contribution of pooling

PurposeTo establish if sodium fluorescein (SFL) dye accumulation within intercellular spaces on the ocular surface contributes to the appearance of superficial punctate corneal staining.MethodsThirteen subjects bilaterally wore PureVision™ lenses that had been pre-soaked in ReNu MultiPlus® multipurpose solution. After 1 h of lens wear, corneal staining with SFL was assessed using a standard slit-lamp technique. Participants who presented with bilateral, corneal staining were selected for further evaluation. A randomly selected eye was rinsed with saline three times. Fellow eyes (control) received no rinsing. After each rinse, the appearance of SFL staining was recorded without any further instillation of the dye. To eliminate any confounding effects of staining due to residual fluorescein in the tear menisci, corneal staining was induced in freshly excised, isolated, rabbit eyes by topical administration of 0.001% PHMB and staining, rinsing and grading were performed as above.ResultsNine out of 13 subjects presented with bilateral diffuse corneal staining (mean grade ± SD: 2.4 ± 0.7). The mean staining grades in test and control eyes respectively after each of the three rinses were (1) 2.41 ± 0.41, 2.25 ± 0.69 (p = 0.9); (2) 2.34 ± 0.79, 2.1 ± 0.83 (p = 0.8); and (3) 1.71 ± 0.65, 1.60 ± 0.79 (p = 0.6) there was no significant reduction in staining with rinsing (p > 0.05) and no difference was observed between test and control eyes at any sampling-point. Similar observations made in ex vivo rabbit eyes replicated these results.ConclusionsPooling or accumulation of SFL solution within intercellular spaces does not appear to contribute to the appearance of superficial micropunctate corneal staining.