Abstract
Purpose :
The aim of this study was to compare the precorneal retention time of two different formulations (eye drops and eye gel) of the same fixed steroid-antibiotic combination (FC) containing 0.1% dexamethasone and 0.3% netilmicin by using optical coherence tomography (OCT).
Methods :
The study was performed in 16 (healthy) subjects age between 14 and 78 years (mean 46,68±SD18,75; 11 females, 5 males). One eye of each subject randomly received a single dose of the FC (Netildex, SIFI, Italy)formulated as eye drop and the fellow eye received a single dose of the same product formulated as eye gel. Evaluation was performed using an ultra-high resolution anterior segment spectral domain OCT (Optovue). Central tear film thickness (CTFT) was measured before instillation (T 0) and then immediately after instillation after 2 blinking (T1) and the every 10 min for 1 h (T2 to T7) and finally after 2 h (T8). The precorneal retention time was calculated by plotting CTFT in function of time. Differences between time points and groups were analysed by Student’s t test.
Results :
Baseline CTFT was 516±33 and 518±30 μm (mean ± SD) in the eyes to be treated with eye gel and eye drops, respectively. Only the eye gel was able to increase significantly CTFT (p<0.001). The maximum effect was observed immediately after instillation (T1=532±35 μm), then reduced progressively returning to the baseline values 60 min (T7) after instillation. By contrast the instillation of eye drops was not capable to increase CTFT. Differences between two formulations were statistically significant after instillation (T1, p<0.0001), at 10 min (T2, p<0.001) and at 20 min (T3, p<0.01).
Conclusions :
These data indicate that a single instillation of the FC formulated as eye gel has a longer precorneal retention time than the corresponding eye drop solution. The presence of the polymer xanthan gum in the eye gel formulation may explain such results. In addition the study confirms that an ultra-high resolution anterior segment spectral domain OCT may be a useful tool for measuring precorneal residence time of any compounds on the ocular surface.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.