Background: The problem of 3 and 9 o'clock staining has been a challenge to rigid lens fitters since the early days of corneal lenses.
Methods: To investigate the features of peripheral corneal desiccation (PCD) in a rigid lens extended wear (RGP EW) population, a study was conducted using 12 subjects known to exhibit significant levels of PCD ("stainers"), and a matched group of individuals who had not shown significant staining with the same lens design ("non-stainers"). Analyses of factors which may be of use in predicting which patients will have problems with PCD were performed to identify differences between groups.
Results: Pre-fitting variables that were associated with the tendency for staining included higher levels of conjunctival hyperemia, a longer inter-blink interval, and poorer tear quality (higher levels of tear lipid and debris in the tear film). Variables associated with lens fitting that were predictive of staining susceptibility included poorer lens surface wetting, faster front surface drying time, an increased ratio of blink interval to lens drying time, inferior lens centration, and more variable or erratic lens movement during the blink cycle.
Conclusions: These data suggest the presence of an underlying ocular surface disorder in patients prone to PCD. It is recommended that all patients be monitored for staining on daily wear prior to commencing an extended wear regimen, and that patients displaying clinically significant levels of corneal staining not proceed to extended wear.