Glaucoma is a chronic progredient neuropathy with typical structural changes at the optic nerve head and with functional defects in the visual fields leading to blindness at the end-stage. Both, glaucoma and dry eye disease (DED) are multifactorial disorders, and the prevalence of glaucoma and DED increases with age.

As glaucoma and DED are very common in the elderly we were interested in the prevalence of DED in different glaucoma types and in a very large sample size.

The German Glaucoma and Dry Eye Register includes analysable data from a total of 20,506 individuals with diagnosed glaucoma taken from 900 ophthalmological centres across Germany. This information has allowed the relationship between the occurrence of dry eye and potential causative factors to be dissected in detail.

Overall, 52.6% of glaucoma patients have a concomitant diagnosis of dry eye versus 47.4% who do not. The gender distribution of the register population is 60.9% (n=12,493) female and 39.1% (n=8,013) male. The German register data found that women with glaucoma were significantly more likely to develop dry eye than men with glaucoma (56.9% versus 45.7%; p<0.0001). In addition, we found a positive correlation between the number of different anti-glaucoma eye drops used and the frequency of DED: 50.9% (n=13,474) of patients using one type of medication report dry eye compared to 65.3% (n=118) of patients using 4 medications, with the association becoming apparent when at least three drugs are used. The register also indicates a positive relationship between duration of glaucoma and the frequency of dry eye. Amongst those patients with glaucoma duration of under a year, 45.3% report dry eye, rising to 58.9% of patients with disease duration of more than 15 years. Furthermore, patients with pigment dispersion glaucoma have the lowest prevalence of DED (45.2%), whereas DED was more common in POAG (52%) and in pseudoexfoliation syndrome (60.9%).

Those glaucoma patients with dry eye experience a significantly higher rate of all local symptoms, especially pain and foreign body sensation. These occur 11- and 12- times more frequently respectively, amongst glaucoma patients with dry eye compared with those without dry eye; other typical symptoms include red eye, pruritus, photosensitivity and blurred vision.

These local symptoms have a significant impact on patients' quality of life, especially when severe, restricting their daily activities, mobility and self-confidence over and above the impact from glaucoma itself, which is largely asymptomatic in the early stages. It is clear that lessening the impact of dry eye and local symptoms in these individuals would improve their quality of life and longer-term prognostic factors. One way to do this is by the use of preservative-free anti-glaucoma medication: not only would this lead to enhancement of patients' quality of life, but also to improvements in glaucoma control, since the resulting lower levels of dry eye would allow a greater proportion of patients to adhere to their medication schedule. In addition, avoiding chronic therapy with preservative-containing eyedrops is likely to have beneficial effects on the health of the cornea and conjunctiva, and increase the chance of glaucoma filtration surgery being successful.