Implantable drainage devices in glaucoma: Quo vadis?

Glaucoma, a gradually progressive class of either chronic eye disease or disorder, occurs due to increasing intra-ocular pressure. To reduce glaucoma, it is essential to stop the progression of IOP in the eye which is achieved by medical treatment, laser treatment and surgery. Profuse conventional drugs and laser surgeries are the primary go-tos for decreasing IOP. However, presently available marketed formulations using anti-glaucoma drugs have issues of either difficulty in crossing the blood retinal barrier (BRB) or lower systemic bioavailability. Hence, the drugs having lower therapeutic index would need to be administered frequently. This repeated systemic administration of high doses of drugs eventually leads to side effects, damage to the eye as well as patient noncompliance. Implants are deemed to be the suitable treatment left when such side effects are to be avoided. An eye implant is one of the choices for restoring the volume of the eye socket following evisceration and enucleation. Implantable drainage devices (IDD) aka glaucoma drainage devices (GDDs) or aqueous shunts are small reconstructive surgery devices, either solid or made of a tube fixed to an endplate. The premonition behind implants is augmenting standard glaucoma surgery which successfully is attained by surgically creating a drainage opening and positioning the device properly on it. All implants are made with an objective of decreasing IOP by enhancing the fluid outflow from the eye. A critical comparison is made among different implants like Molteno: single-plate and Double-plate, Baerveldt drainage implant, Schocket implant, Ex-Press R50 implant, Ahmed glaucoma valve, Krypton implant to the latest one's including iStent, iStent inject, Hydrus, CyPass, XEN and InnFocus.