Tear secretions from lacrimal gland differ in normal versus dry eyes
Tears are necessary for maintaining the health of the ocular surface and normal vision. Several internal and external factors may affect tear film composition, integrity, and stability negatively, resulting in dry eye disease (DED). Recent research suggests that tear secretion significantly differs between evaporative dry eyes (EDE) aqueous deficient dry eye and dry eye in cicatrising conjunctivitis (CC). The research has been published in the journal BMJ Ophthalmology on February 17, 2021.
Dry eye disease (DED) is a multifactorial syndrome that can be caused by the alteration in the quality or quantity of the precorneal tear film. Studies suggest that between 5% and 50% of the adult population have symptoms of dry eye disease, and the condition is more common in Asian populations, especially in females. Evaporative dry eye, a condition affecting the meibomian glands, is one of the most common underlying causes of dry eye. Nearly 90% of people diagnosed with evaporative dry eye have MGD! However, the variation in the secretory status of the main lacrimal gland in dry eyes and normal eyes remains unclear. Therefore, researchers of the LV Prasad Eye Institute, Hyderabad, India conducted a study to investigate the secretory status of the main lacrimal gland in healthy and dry eye disease (DED) via fluorescein-assisted direct assessment of tear secretion from the palpebral lobes.
It was a prospective trial of 100 subjects, among which 25 were healthy subjects (50 lobes) and 75 subjects were with DED (cicatrising conjunctivitis (CC, n=27), evaporative dry eyes (EDE, n=25) and Sjogren's syndrome (SS, n=23)). The major outcome assessed was the number and location of ductular openings, tear flow rate per gland and per ductule, and the time lag for the initiation of secretion.
Key findings of the study were:
♦ Ductular openings could be observed in all patients with EDE and healthy subjects, however, upon examination, researchers noted only 33% (18/54) glands of CC patients and 67% glands (31/46) patients with SS revealed ductules.
♦The median number of ductules per lobe was 4 in normal (range 3–5), 3 in EDE (3–6), 1 in SS (0–3) and 0 in CC group (0–3).
♦They found a significant lesser tear flow rate per lobe in CC (0.00 µL/min) and SS (0.21 µL/min) than in normal lobes (1.05 µL/min, and EDE (0.99 µL/min) eyes.
♦ They also noted a significant difference in tear flow rate between SS and CC group.
♦ They observed that the maximum time lag occurred in the CC group (median, 20 s), followed by the SS group (median, 1.5 s) whereas the EDE group had similar time lag (<1 s) as of normal glands.
The authors concluded, "Direct assessment of tear secretion from the palpebral lobe demonstrates significant differences between EDE, aqueous deficient dry eye and dry eye in CC".
For further information:
https://bjo.bmj.com/content/early/2021/02/16/bjophthalmol-2020-318159
