The Effect of Tear Supplementation on Ocular Surface Sensations during the Interblink Interval in Patients with Dry Eye

Abstract

PurposeTo investigate the characteristics of ocular surface sensations and corneal sensitivity during the interblink interval before and after tear supplementation in dry eye patients.MethodsTwenty subjects (41.88±14.37 years) with dry eye symptoms were included in the dry eye group. Fourteen subjects (39.13±11.27 years) without any clinical signs and/or symptoms of dry eye were included in the control group. Tear film dynamics was assessed by non-invasive tear film breakup time (NI-BUT) in parallel with continuous recordings of ocular sensations during forced blinking. Corneal sensitivity to selective stimulation of corneal mechano-, cold and chemical receptors was assessed using a gas esthesiometer. All the measurements were made before and 5 min after saline and hydroxypropyl-guar (HP-guar) drops.ResultsIn dry eye patients the intensity of irritation increased rapidly after the last blink during forced blinking, while in controls there was no alteration in the intensity during the first 10 sec followed by an exponential increase. Irritation scores were significantly higher in dry eye patients throughout the entire interblink interval compared to controls (p<0.004). NI-BUT significantly increased after HP-guar (p = 0.003) but not after saline drops (p = 0.14). In both groups, either after saline or HP-guar the shape of symptom intensity curves remained the same with significantly lower irritation scores (p<0.004), however after HP-guar the decrease was significantly more pronounced (p<0.004). Corneal sensitivity to selective mechanical, cold and chemical stimulation decreased significantly in both groups after HP-guar (p<0.05), but not after saline drops (p>0.05).ConclusionOcular surface irritation responses due to tear film drying are considerably increased in dry eye patients compared to normal subjects. Although tear supplementation improves the protective tear film layer, and thus reduce unpleasant sensory responses, the rapid rise in discomfort is still maintained and might be responsible for the remaining complaints of dry eye patients despite the treatment.

External eye symptoms in indoor environments

“…Although the threshold for sensory irritation in the upper airways by formaldehyde is unaltered at low RH in mice, it may be speculated that a desiccated PTF with dry spots would facilitate direct exposure contact to the corneal epithelium and thus become more susceptible to sensory irritants or reactive oxygen species. For instance, patients with DED perceived a rapid increase and higher intensity of irritation after the last blink during forced blinking, while the intensity among controls remained unaltered the first 10 seconds and then increased …”

Cyclosporine A Decreases Dryness-Induced Hyperexcitability of Corneal Cold-Sensitive Nerve Terminals

“…Ocular discomfort is reported to be a major complaint of DED [ 9 , 26 , 27 ]. The activation of corneal sensory nerves (polymodal and mechano- nociceptors and cold thermoreceptors) is responsible for the sensations evoked from the ocular surface [ 4 , 5 ].…”