Meibomian gland dysfunction (MGD) is among the leading causes for dry eye syndrome (DES), affecting millions of people worldwide. We have shown in a previous study that tear film thickness (TFT) is reduced in patients with DES and that this reduction correlates with tear break up time (BUT) as well as with the severity of subjective symptoms. Even though systemic tetracyclines as well as topical azithromycin can be used for the treatment of MGD, it seems that topical azithromycin is more effective than tetracyclines and also has the advantage of better tolerability. The hypothesis of the present study is that topical treatment with azithromycin leads to a more pronounced increase in TFT compared to oral doxycycline in patients with DES caused by MGD.

The objective of this study is to compare the effect of treatment with topical azithromycin or oral doxycycline on tear film thickness in patients with DES caused by MGD.

Inclusion Criteria:

• Men and women aged over 18 years
• Signs of meibomian gland plugging or expressibility of the meibomian glands.
• DES most likely caused by MGD, no other cause identifiable which is more likely (e.g. intake of concomitant medication that could induce DES, systemic diseases such as systemic arthritis or diabetes), as judged by the investigator
• Signed and dated written informed consent.
• History of dry eye syndrome for at least 3 months
• Normal ophthalmic findings except dry eye syndrome and MGD, ametropia < 6 Dpts
• BUT ≤ 10 seconds

Exclusion Criteria:

• Participation in a clinical trial in the 3 weeks before the screening visit
• Symptoms of a clinically relevant illness in the 3 weeks before the first study day
• Presence or history of a severe medical condition that will interfere with the study aim as judged by the clinical investigator
• Sjögren's syndrome
• Stevens-Johnson syndrome
• Presence or history of a severe ocular condition that will interfere with the study aim as judged by the clinical investigator
• Treatment with corticosteroids in the 4 weeks preceding the study
• Wearing of contact lenses
• Topical treatment with any ophthalmic drug in the 4 weeks preceding the study except topical lubricants Ocular infection
• Ocular surgery in the 6 months preceding the study
• Pregnancy, planned pregnancy or lactating
• Contraindication against the use of topical azithromycin or oral doxycycline