Tear Film Dynamics between Low and High Contact Lens Dry Eye Disease Questionnaire (CLDEQ-8) Score with a Lehfilcon A Silicone Hydrogel Water Gradient Contact Lens: A Non-Invasive Methodology Approach

The purpose of this study is to evaluate the tear film dynamics between individuals with low and high Contact Lens Dry Eye Disease Questionnaire (CLDEQ-8) scores when wearing Lehfilcon A silicone hydrogel water gradient contact lenses. In this study, we implemented a longitudinal, single-location, self-comparison investigation. Variables measured included conjunctival redness, lipid layer thickness, tear meniscus height, first and mean non-invasive break-up time, CLDEQ-8, and standard patient evaluation of eye dryness (SPEED). In the second phase, participants were re-evaluated after 30 days of wearing the contact lenses to assess the tear film wearing the lenses. In a longitudinal comparison by group, we found that lipid layer thickness decreased 1.52 ± 1.38 (p < 0.01) and 0.70 ± 1.30 (p = 0.01) Guillon patterns degrees in the low and high CLDEQ-8 group, respectively. MNIBUT increased in 11.93 ± 17.93 (p < 0.01) and 7.06 ± 12.07 (p < 0.01) seconds. Finally, LOT increased in 22.19 ± 27.57 (p < 0.01) and 16.87 ± 25.09 (p < 0.01). In conclusion, this study demonstrates the effectiveness of Lehfilcon A silicone hydrogel water gradient contact lenses in improving tear film stability and reducing subjective dry eye symptoms in individuals with low and high CLDEQ-8 scores. However, it also led to an increase in conjunctival redness and a decrease in tear meniscus height.

Impact of acute conjunctivitis on ocular surface homeostasis in dogs

OBJECTIVE

To investigate the effects of acute conjunctivitis on tear film characteristics and corneal sensitivity in dogs.

ANIMALS STUDIED

Eight female spayed Beagle dogs (1.5-2 years old, 7.5-10 kg).

PROCEDURES

On two consecutive days, one randomly selected eye in each dog received 1 or 375 mg/mL histamine solution to induce mild or severe conjunctivitis, while the contralateral eye served as control. Diagnostic tests were performed in the following order: fluorescein instillation and repeated tear collection over 20 minutes (to determine tear volume [TV] and turnover rate [TTR] by fluorophotometry), Schirmer tear test-1 (STT-1), tear ferning, corneal esthesiometry, and tear film breakup time (TFBUT).

RESULTS

Results are presented as median values for severe conjunctivitis, mild conjunctivitis, and control eyes. Eyes with severe conjunctivitis had significantly higher STT-1 (24, 19.5, 17.5 mm/min; P = .002) and significantly lower TFBUT (10.5, 13.5, 15.5 s; P = .002), but no changes were noted in corneal tactile sensation (2, 2.5, 2.5 cm) or tear ferning (grades 2, 2, 2.5). Severe conjunctivitis significantly increased TV by nearly 10-fold (631, 97, 65 µL) initially (reflex tearing), although basal TV returned rapidly (<5 minutes) in all eyes (46, 58, 48 µL). Finally, there was a nonsignificant trend for higher reflex TTR in the conjunctivitis vs control eyes (68, 58, 43%/min).

CONCLUSIONS

Experimentally induced conjunctivitis increases tear quantity and decreases tear quality in dogs, but has no impact on corneal sensitivity. Changes in tear film dynamics could affect ocular pharmacology (eg, precorneal retention time), although homeostasis of lacrimal volume and drainage is rapidly restored.

Fourier-Domain OCT Imaging of the Ocular Surface and Tear Film Dynamics: A Review of the State of the Art and an Integrative Model of the Tear Behavior During the Inter-Blink Period and Visual Fixation

In the last few decades, the ocular surface and the tear film have been noninvasively investigated in vivo, in a three-dimensional, high resolution, and real-time mode, by optical coherence tomography (OCT). Recently, OCT technology has made great strides in improving the acquisition speed and image resolution, thus increasing its impact in daily clinical practice and in the research setting. All these results have been achieved because of a transition from traditional time-domain (TD) to Fourier-domain (FD) technology. FD-OCT devices include a spectrometer in the receiver that analyzes the spectrum of reflected light on the retina or ocular surface and transforms it into information about the depth of the structures according to the Fourier principle. In this review, we summarize and provide the state-of-the-art in FD-OCT imaging of the ocular surface system, addressing specific aspects such as tear film dynamics and epithelial changes under physiologic and pathologic conditions. A theory on the dynamic nature of the tear film has been developed to explain the variations within the individual compartments. Moreover, an integrative model of tear film behavior during the inter-blink period and visual fixation is proposed.

The precorneal tear film as a fluid shell: the effect of blinking and saccades on tear film distribution and dynamics

We conducted a series of experiments to elucidate the behavior of the human precorneal tear film (PCTF) during blinking and horizontal and vertical saccades. Methodology included video-interferometry with subsequent image cross-correlation (tear film lipid layer [TFLL]) and video-microscopy (mucoaqueous subphase [MAS]). We observed that the TFLL interference pattern deteriorates rapidly with successive blinks and degrades slowly with repeated horizontal saccades during blink suppression when dark arcs of thinning appear in the fluorescein-stained PCTF. Furthermore, after full downgaze and a return to the primary position, a transient horizontal bright band appears, deep to the spreading TFLL. It may be followed by local disturbances in the interference pattern. Two horizontal dark bands form in the stained PCTF after the return saccade. PCTF disruption may occur below the lower band during blink suppression. We concluded that shearing during horizontal saccades is insufficient to disturb the tear film structure greatly. The MAS and TFLL move together as a fluid shell. The dark arcs/bands are caused by meniscus-induced thinning, imprinted onto the PCTF at the lid margin. Their stability during blink suppression suggests that the MAS has gel-like properties. The horizontal bright bands are probably due to transient corneal indentation in downgaze. In downgaze, the disturbance of the TFLL and MAS below the dark bands is possibly due to shearing across the MAS in the return phase. This could cause desiccating stress in everyday activities, such as working at a computer.