Hyaluronic acid is a naturally occurring polysaccharide with distinct physicochemical properties which underlie its application as a viscoelastic tool in ophthalmological surgery. In cataract surgery the role of hyaluronic acid in facilitating procedures and protecting the corneal endothelium is well established. Some benefit has also been gained with the use of hyaluronic acid in penetrating keratoplasty, trabeculectomy, retinal reattachment and trauma surgery, although its efficacy in these indications is less well-defined in the published literature. In addition to its lubricating and cushioning properties, demonstration of some in vitro anti-inflammatory activity and a possible disease-modifying effect for hyaluronic acid in animals has prompted its investigation as a treatment in osteoarthritis and, to a much lesser extent, in rheumatoid arthritis. Hyaluronic acid 20 mg, as weekly intra-articular injections for 3 to 7 weeks, improved knee pain and joint motion in patients with osteoarthritis. Although this occurred to a greater degree than with placebo in most comparisons, the effects of hyaluronic acid was similar to those of placebo in the largest trial. In the few available comparisons with other agents, hyaluronic acid appeared equivalent to methylprednisolone 40 mg (for 3 weeks) and to a single injection of triamcinolone 40 mg. Hyaluronic acid was distinguished from other therapies by providing a sustained effect after treatment discontinuation. Together with its very good tolerability profile, these properties justify further study of hyaluronic acid in patients with osteoarthritis. Some limited evidence of improvement in patients with rheumatoid arthritis, and a possible healing effect of hyaluronic acid on tympanic membrane perforations, represent additional areas of interest for future investigation. In summary, hyaluronic acid is a well-established adjunct to cataract surgery and may prove to be a promising option in the treatment of patients with osteoarthritis. Its very good tolerability provides further impetus for examination of its potential role in an extended scope of arthritic and ophthalmological indications, and in wound healing.

Hyaluronic acid. A review of its pharmacology and use as a surgical aid in ophthalmology, and its therapeutic potential in joint disease and wound healing.

Hyaluronic acid (also known as hyaluronan or hyaluronate) is naturally found in many tissues and fluids, but more abundantly in articular cartilage and synovial fluid (SF). Hyaluronic acid (HA) content varies widely in different joints and species. HA is a non-sulfated, naturally occurring non-protein glycosaminoglycan (GAG), with distinct physico-chemical properties, produced by synoviocytes, fibroblasts, and chondrocytes. HA has an important role in the biomechanics of normal SF, where it is partially responsible for lubrication and viscoelasticity of the SF. The concentration of HA and its molecular weight (MW) decline as osteoarthritis (OA) progresses with aging. For that reason, HA has been used for more than four decades in the treatment of OA in dogs, horses and humans. HA produces anti-arthritic effects via multiple mechanisms involving receptors, enzymes and other metabolic pathways. HA is also used in the treatment of ophthalmic, dermal, burns, wound repair, and other health conditions. The MW of HA appears to play a critical role in the formulation of the products used in the treatment of diseases. This review provides a mechanism-based rationale for the use of HA in some disease conditions with special reference to OA.

Hyaluronic Acid: Molecular Mechanisms and Therapeutic Trajectory.

The Effect of Phacoemulsification on Aqueous Outflow Facility

Comparison of the effects of viscoat and healon on postoperative intraocular pressure

Intraocular pressure (IOP) was measured before and 6, 24, 48 and 72 h after extracapsular catacact extraction with implantation of a posterior chambers lens in 3 groups of patients. Group I (30 patients): Sodium hyaluronate (Healon®) was used during anterior capsulotomy and lens implantation and was aspirated at the end of surgery. Group II (22 patients): Healon as in group I + 500 mg acetazolamide at the end of surgery. Group III (17 patients): BSS and/or air was used instead of Healon during surgery. In all groups statistically significant rises in IOP after 6 h were followed by significant falls in the remaining post-operative period. The rise and subsequent fall in IOP was significantly greater in group I than in group III. Acetazolamide in group II did not prevent excessive rises in IOP. Aspiration probably shortens the period of Healon-induced hypertension. We recommend a meticulous aspiration of Healon at the end of surgery.

Bo T. Philpson

Papers

Sodium Hyaluronate in Cataract Surgery: I. Report on the Use of Healon® in Two Different Types of Intracapsular Cataract Surgery