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M. Lin, K.A. Copley, C.J. Radke; Assessment Of Pre–Lens Tear–Film Stability By Slit–lamp Examination, Placido Ring Reflection, IBUT, And Advancing Contacting Angles: Do They Correlate? . Invest. Ophthalmol. Vis. Sci. 2006;47(13):95.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the correlation among four common methods of assessing pre–lens tear film stability (PrLTFS).
The PrLTFS of lotrafilcon A SCLs was assessed on 24 experienced wearers 15 minutes after lens insertion and after 2–week of lens wear. Assessment was made in the order of (1) a slit–lamp examination with white light and a diffuser, (2) examining reflected mier images from a photokeratoscope, (3) invasive breakup time (IBUT) and (4) ex–vivo lens wettability . With the slit–lamp, PrLTFS was graded on a scale of 0 (most stable) to 4 (least stable). Similarly, a 0–4 scale of ring distortion and haze was applied on central, inferior, nasal and temporal zones of the photokeratoscopic images (0 gives no distortion or haze and 16 gives maximum distortion or haze) taken 10 seconds after blink. IBUT was defined as the time required to observe the first PrLTF break up (black spot or streak) after a blink using a slit–lamp with cobalt blue light and yellow filer after instillation of 2 µl of Fluorosoft. Finally, wettability of the SCLs was determined by the liquid advancing angle from a captive air bubble.
The average ± SE advancing angle for fresh and worn lenses was 39 ± 1.8 º and 80 ± 5 º, respectively (p = 0.001).
For lotrafilcon A SCLs, both slit lamp and reflected placido ring distortion showed that worn lenses exhibited significantly poorer PrLTFS compared to fresh lenses. Captive–bubble advancing contact angles showed decreased wettability upon lens wear correlating directly with poorer PrLTFS. IBUT was not sensitive enough to detect differences in tear–film disruption, most likely because first black spot/streak appearance reflects a single localized area. Evaluating reflected ring distortion may be useful in a large sample–size study to replace the slit–lamp method, eliminating the need for qualitative assessment of tear quality by trained clinicians.
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