Research
Research areas have included:

Macular degeneration
Rheumatoid arthritis instead of minocycline (both of which have demonstrated modest efficacy for this disease)

Research reagent
Doxycycline and other members of the tetracycline class of antibiotics are often used as research reagents in in vitro and in vivo biomedical research experiments involving bacteria as well in experiments in eukaryotic cells and organisms with inducible protein expression systems using tetracycline-controlled transcriptional activation. The mechanism of action for the antibacterial effect of tetracyclines relies on disrupting protein translation in bacteria, thereby damaging the ability of microbes to grow and repair; however protein translation is also disrupted in eukaryotic mitochondria impairing metabolism and leading to effects that can confound experimental results. Doxycycline is also used in "tet-on" (gene expression activated by doxycycline) and "tet-off" (gene expression inactivated by doxycycline) tetracycline-controlled transcriptional activation to regulate transgene expression in organisms and cell cultures. Doxycycline is more stable than tetracycline for this purpose. At subantimicrobial doses, doxycycline is an inhibitor of matrix metalloproteases, and has been used in various experimental systems for this purpose, such as for recalcitrant recurrent corneal erosions. COVID-19
After a large-scale trial showed no benefit of using doxycycline in treating COVID‑19, the UKs National Institute for Health and Care Excellence (NICE) updated its guidance to not recommend the medication for the treatment of COVID‑19. References
External links
"Doxycycline". Drug Information Portal. U.S. National Library of Medicine.
Enophthalmos is a posterior displacement of the eyeball within the orbit. It is due to either enlargement of the bony orbit and/or reduction of the orbital content, this in relation to each other.It should not be confused with its opposite, exophthalmos, which is the anterior displacement of the eye. It may be a congenital anomaly, or be acquired as a result of trauma (such as in a blowout fracture of the orbit), Horners syndrome (apparent enophthalmos due to ptosis), Marfan syndrome, Duanes syndrome, silent sinus syndrome or phthisis bulbi. References
Further reading
Cline RA, Rootman J (1984). "Enophthalmos: a clinical review". Ophthalmology. 91 (3): 229–37. doi:10.1016/s0161-6420(84)34299-3. PMID 6717910. == External links ==