Abstract
Purpose :
To establish a method of tear collection from the tear film reservoir (TFR) of a scleral lens (SGP) system and to measure the protein, lipid, and protease concentrations in the TFR of SGP wearers with and without keratoconus (KC).
Methods :
Habitual SGP wearers were recruited. Subjects applied their SGP 4h prior to the study visit, applying the lenses with preservative free saline (approximately 2ml is used to fill the bowl of the lens). At the visit, the TFR fluid from beneath the SGP system was collected by having the subject tilt their head forward, allowing an investigator to remove the lens and collect the fluid from the concave portion of the SGP using a micropipette. After collection, the TFR samples were analyzed for protein, lipid and matrix metalloproteinase (MMP)-1, -2, -7, -9, and -10 (MMP multiplex bead array) concentrations.
Results :
Twenty six SGP wearers were recruited (n=15 with KC; n=11 post-refractive surgery patients). The mean volume of TRF collected from subjects in this study was 47 ± 48 µl (range 4 – 212 µl). No significant differences were found between the protein median concentrations in the KC and the non-KC group, 2.85 vs 3.75 µg/µl respectively, (p = 0.11). There were no differences found in lipid concentration between the two groups (0.0015 µg/µl in KC group, 0.0020 µg/µl in non-KC group; p = 0.88).There were no differences in the concentrations of MMP-1 (p = 0.90), MMP-2 (p = 0.98), MMP-7 (p = 0.78), or MMP-10 (p = 0.74). The concentration of MMP-9 was significantly higher in the KC group (median KC: 581.74 pg/ml, median non-KC: 105.19 pg/ml, p = 0.01).
Conclusions :
We report a method for collecting the TFR which is in direct contact with the ocular surface in SGP wearers that is suitable for total and specific protein and lipid analysis. Here we found that MMP-9 is increased in the KC group of SGP wearers, although studies expanding on this pilot data are indicated to develop a clearer relationship between TFR components and KC.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.