Minimising instilled volume reduces the impact of fluorescein on clinical measurements of tear film stability.
OBJECTIVE
To compare clinical tear film break-up time measurements obtained non-invasively, with those measured following minimal and conventional volumes of fluorescein instillation.


METHODS
Forty-one subjects (20 male, 21 female, mean±SD age 34±11years), with or without dry eye, participated in a prospective cross-over study. Tear film break-up time was measured by the Tearscope Plus™ with fine grid insert. Measurements were made in triplicate, with no fluorescein instillation (NIBUT), then following application of a minimal volume of 1μl fluorescein from the Dry Eye Test™ (mTBUT), and finally with 15-30μl of fluid instilled via a conventional fluorescein strip (TBUT). A fifteen-minute interval between each set of measurements minimised the risk of residual contamination effects.


RESULTS
All three techniques displayed statistically significant pairwise correlation (all p<0.001). TBUT values were significantly shorter than both NIBUT (geometric mean 8.6s versus 10.9s, p=0.03) and mTBUT (geometric mean 8.6s versus 10.6s, p=0.03), and demonstrated narrower spread (both p<0.05). No significant differences were detected between NIBUT and mTBUT (all p>0.05).


CONCLUSIONS
Tear film break-up time values measured with conventional fluorescein instillation were shortened, while minimal fluorescein instillation and non-invasive methods produced comparable readings. This suggests that minimising instilled volumes can reduce the impact of fluorescein on clinical measurements of tear film stability.
Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand; Warringal Private Hospital, Heidelberg, VIC, Australia.
Jennifer K
JK
Mooi
Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand.
Michael T M
MTM
Wang
Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand.
Joevy
J
Lim
Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand; Centre for Eye Research Australia (CERA), Melbourne, VIC, Australia.
Andreas
A
Müller
Department of Ophthalmology, New Zealand National Eye Centre, The University of Auckland, New Zealand. Electronic address: jp.craig@auckland.ac.nz.
Jennifer P
JP
Craig
D000293:Adolescent; D000328:Adult; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D015352:Dry Eye Syndromes / Q000175:diagnosis* / Q000378:metabolism; D005260:Female; D019793:Fluorescein / Q000008:administration & dosage* / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000493:pharmacokinetics; D006801:Humans; D007322:Instillation, Drug; D008297:Male; D009883:Ophthalmic Solutions; D011446:Prospective Studies; D013666:Tears / Q000737:chemistry* / Q000187:drug effects; D055815:Young Adult
D005456:Fluorescent Dyes; D009883:Ophthalmic Solutions; D019793:Fluorescein
Break-up time; Fluorescein; Tear film; Tear film stability