Two interesting questions concerning pharmacology related to women are why certain eye disorders related to a reduced antioxidant function of tears show a predilection for feminine gender; and why oestrogen therapy reportedly improves or worsens the symptoms of dry-eye syndrome and other ocular disorders.

Lacrimal fluid peroxidase is an antioxidant and antimicrobial enzyme whose main role is to protect the ocular surface. Some investigators consider lacrimal peroxidase an enzymatic marker of protein secretion regulated by the autonomic nervous system. Others suggest that the lacrimal gland, like its secretions, is directly influenced by sex hormones, including androgens, oestrogens and progestins. Which of these hormones are directly implicated is unclear.

Like the composition of lacrimal fluid, the morphology of the lacrimal gland also undergoes changes related to sex and age. Although these differences suggest that oestrogens may have a role in glandular secretion precisely how they intervene remains controversial.

The data from this review strongly favour the proposed positive feedback between plasma oestrogen levels and human lacrimal peroxidase activity. They also underline the influence of gender and ageing, as well as hormone-replacement therapy in menopausal women, and of oral contraceptives in normocyclic women. More research is warranted on the mechanisms underlying oestrogen-induced changes in human lacrimal peroxidase activity.