Drugs and Biological Agents Used in Ophthalmic Surgery

Drugs and Biological Agents Used in Ophthalmic Surgery

ADJUNCTS IN ANTERIOR SEGMENT SURGERY Viscoelastic substances assist in ocular surgery by maintaining spaces, moving tissue, and protecting surfaces. These substances are
prepared from hyaluronate, chondroitin sulfate, or hydroxypropylmethylcellulose, share the following important physical characteristics: viscosity, shear flow, elasticity, cohesiveness, and coatability, and are broadly characterized as dispersive or cohesive. They are used almost exclusively in anterior segment surgery. Complications associated with viscoelastic substances are related to transient elevation of IOP after the procedure.

OPHTHALMIC GLUE Cyanoacrylate tissue adhesive (ISODENT, DERMABOND, HISTOACRYL),
while not FDA approved for the eye, is widely used in the management of corneal ulcerations and
1108 SECTION XIV Ophthalmology perforations. It is applied in liquid form and polymerized into a solid plug. Fibrinogen glue (TISSEEL) is increasingly being used on the ocular surface to secure tissue such as conjunctiva, amniotic membrane, and lamellar corneal grafts.

CORNEAL BAND KERATOPATHY Edetate disodium (disodium EDTA; ENDRATE) is a chelating agent that can be used to treat band keratopathy (i.e., a calcium deposit at the level of Bowman’s membrane on the cornea). After the overlying corneal epithelium is removed, it is
applied topically to chelate the calcium deposits from the cornea.

ANTERIOR SEGMENT GASES Sulfur hexafluoride (SF6) and perfluoropropane gases have long been used as vitreous substitutes during retinal surgery. In the anterior segment, they are
used in nonexpansile concentrations to treat Descemet’s detachments, typically after cataract surgery.

These detachments can cause mild-to-severe corneal edema. The gas is injected into the anterior
chamber to push Descemet’s membrane up against the stroma, where ideally it reattaches and
clears the corneal edema.

VITREOUS SUBSTITUTES The primary use of vitreous substitutes is reattachment of the
retina following vitrectomy and membrane-peeling procedures for complicated proliferative vitreoretinopathy and traction retinal detachments. Several compounds are available, including
gases, perfluorocarbon liquids, and silicone oil . With the exception of air, the gases expand because of interaction with systemic oxygen, carbon dioxide, and nitrogen, and this property makes them desirable to temporarily tamponade areas of the retina. However, use of these expansile gases carries the risk of complications from elevated IOP, subretinal gas, corneal edema, and cataract formation. The gases are absorbed over a time period of days (for air) to 2 months (for perfluoropropane).

The liquid perfluorocarbons, with specific gravities between 1.76 and 1.94, are denser than vitreous and are helpful in flattening the retina when vitreous is present. If a lens becomes dislocated into the vitreous, a perfluorocarbon liquid injection posteriorly will float the lens anteriorly, facilitating surgical retrieval. This liquid can be an important tool for flattening and unrolling severely detached and contorted retinas such as those found in giant retinal tears and proliferative vitreoretinopathy but are potentially toxic if it remains in chronic contact with the retina.

Silicone oil has had extensive use for long-term tamponade of the retina. Complications from
silicone oil use include glaucoma, cataract formation, corneal edema, corneal band keratopathy, and retinal toxicity.