Tear volume in relation to contact lens wear and age

We examined the tear volume of the inferior conjunctival sac in relation to patient age and complications of contact lens wear using a special phenol red thread test. Records of patients who had undergone this test between 1984 and 1987 were reviewed. Based on the wet length of the thread, three groups were defined: 9 mm or less, 10-14 mm, and 15 mm or more. Those patients who showed consistent results over three or more separate testings were selected for this study. A total of 11,336 eyes met this criterion. A confidence interval of 95% was established as a basis for comparison of the groups. We found that the percentage of eyes with 9 mm or less of wet length increased with the age of the subject group. Likewise, the percentage of each age group with 15 mm or more of wet length steadily decreased among progressively older groups. Eyes wearing PMMA lenses with 9 mm or less of wet length showed the highest incidence of superficial punctate keratitis (SPK) and erosion. The group of eyes wearing high-DK lenses with 15 mm or more of wet length showed the lowest incidence of SPK and erosion.