Tear film osmolarity in patients with facial palsy
Research type
Research Study
Full title
An observational cohort study to assess the impact of unilateral facial nerve palsy on a patient’s tear film osmolarity
IRAS ID
197091
Contact name
Jonathan Norris
Contact email
Sponsor organisation
Oxford University Hospitals NHS Foundation Trust
Duration of Study in the UK
0 years, 6 months, 1 days
Research summary
The facial nerve is responsible for controlling not only the muscles of facial expression, but also responsible for providing parasympathetic innervation to the lacrimal gland. The tear film is made up of a superficial lipid layer secreted by the Meibomian glands, an aqueous layer comprising approximately 80% of the total volume and a mucus layer. The lacirmal gland together with the accessory lacrimal glands of Krause and Wolfring make the aqueous component of tears. Studies have shown the lacrimal gland to be under the control of nerves supplied by the facial nerve while the control of the accessory glands is less well established.
Our study aims to look at the affect a facial nerve palsy has on the exocrine function of the lacrimal gland by measuring the osmolarity of the tear film. Given the important parasympathetic supply to the lacrimal gland by the facial nerve, it is our hypothesis that the tear film osmolarity will be increased in the affected eye. We are also hoping to establish if there is a link between the degree of facial nerve palsy and how abnormal the tear film osmolarity is.
The tear film osmolarity will be assessed by the CE marked, Tear Lab machine, a minimally invasive test whereby the conductivity of a tiny tear sample (50 nanolitre), collected from the tear meniscus is converted into units of tear osmolarity. Studies have classified a normal tear osmolarity as <308mOsms/L[3] and we have set this as the upper limit of a normal tear film osmolarity. The procedure is not painful and no anaesthetic is required.
It is well known the facial nerve palsy can affect the ocular surface through altering the blink response and by causing lagophthalmos. A study published in 2012 by Shah et al. found a facial nerve palsy caused a reduction in Meibomian gland function. To our knowledge there have been no published studies looking at the affects of a facial nerve palsy on tear film osmolarity. It is hoped this study will be able to identify the degree to which a facial nerve palsy patient’s tear film osmolarity is altered and serve as a base for future studies.
REC name
London - Harrow Research Ethics Committee
REC reference
16/LO/0696
Date of REC Opinion
20 May 2016
REC opinion
Further Information Favourable Opinion