Influence of Anterior Segment Trauma on Endogenous Hyaluronan in the Rabbit Cornea and Aqueous

Effects of sympathetic denervation on the hyaluronan content of the anterior segment in the normal and traumatized rabbit eye

PURPOSE

To determine whether there is any involvement of sympathetic nerves in the regulation of ocular hyaluronan production in the normal and traumatized rabbit iris.

METHODS

Unilateral sympathetic denervation was performed by removing the right superior cervical ganglion. Hyaluronan concentrations in the iris and aqueous were measured with a radiometric assay at various time intervals after denervation. Peripheral iridectomy was also performed in both denervated and non-denervated eyes.

RESULTS

Hyaluronan concentrations in the iris tissue after denervation were observed to have increased after 1 day, reaching a peak of 129.6 +/- 5.7 microg/g wet weight at day 3. Two weeks later, hyaluronan concentrations had fallen back to normal levels. Ocular trauma with peripheral iridectomy in denervated eyes caused an increase of hyaluronan content of up to 253.5 +/- 30.5 microg/g wet weight, which was not significantly different from hyaluronan concentrations observed after the same trauma in non-denervated eyes.

CONCLUSION

Cervical sympathetic denervation results in a moderate increase of the hyaluronan content in the rabbit iris and does not appear to influence the hyaluronan response of the iris to trauma.

Influence of laser irradiation on endogenous hyaluronan in rabbit iris and aqueous humor

PURPOSE

To monitor changes of endogenous hyaluronan in the iris tissue and aqueous humor after an isolated trauma to the iris by argon laser irradiation of the anterior surface of the iris.

METHODS

Iris and aqueous hyaluronan concentrations in rabbit were measured with a radiometric assay at different time points after laser irradiation.

RESULTS

Total hyaluronan content in iris tissue increased 3-fold to a peak concentration of 71-72 microg/g at 1 and 2 days after laser treatment. Aqueous hyaluronan increased to a maximum of about 1.6 microg/ml at 2 h and 12 h after laser irradiation of the iris.

CONCLUSIONS

The iris tissue responds with increased hyluronan synthesis to an isolated iris argon laser irradiation and it seems to be the most important source of aqueous hyaluronan.

Corticosteroid Suppression of TraumaInduced Hyaluronan in Rabbit Cornea and Aqueous

BACKGROUND

Corneal and aqueous hyaluronan have recently been shown to react in response to several different types of trauma, including cataract surgery. In order to find ways to influence the reaction, we have evaluated the effect of topical dexamethasone (Isopto-Maxidex, Alcon Universal Ltd, Fort Worth, Tex) or indomethacin (Confortid, Dumex Ltd, Copenhagen, Denmark) on the postoperative hyaluronan concentration in rabbit cornea and aqueous after extracapsular lens extraction.

METHODS

The drugs were administered as topical eye drops three times daily. The hyaluronan concentration in rabbit cornea and aqueous after extracapsular lens extraction was measured with a radioligand assay.

RESULTS

Dexamethasone treatment (1 mg/mL) significantly suppressed the increase in corneal hyaluronan seen after extracapsular lens extraction, 2 (p < or = 0.0022) and 3 weeks (p < or = 0.0002) after surgery, while indomethacin did not induce any significant difference at 2 weeks. When the dexamethasone concentration was lowered to 0.1 and 0.2 mg/mL, there was still a significant decrease (p < or = 0.009) in hyaluronan concentration, but at lower concentrations of dexamethasone (0.01 and 0.02 mg/mL), no significant decrease was seen. The increase in aqueous hyaluronan concentration seen 2 days after surgery in untreated eyes was significantly lowered by both dexamethasone (p < or = 0.0076) and indomethacin (p < 0.036).

CONCLUSIONS

Dexamethasone lowers reactive corneal and aqueous hyaluronan concentration in vivo after extracapsular lens extraction.

Randomized Clinical Trial of Topical Sodium Hyaluronate After Excimer Laser Photorefractive Keratectomy

BACKGROUND

Sodium hyaluronate (Healon) has been reported to promote corneal epithelial healing following severe eye burns in humans and rabbits. Endogenous hyaluronate has been shown to be significantly increased in the corneal tissue following extracapsular lens extraction, anterior segment trauma, and radial keratotomy. The authors report the use of topical sodium hyaluronate administration on the cornea of eyes which have been treated by photorefractive keratectomy for myopia.

METHODS

Forty eyes of 40 patients undergoing excimer laser photorefractive keratectomy for myopia were studied to evaluate the effect of topical sodium hyaluronate versus placebo (Healon buffer) instillation on pain and corneal epithelial healing in an observer blind randomized clinical trial.

RESULTS

There was no significant difference between patients whose eyes were treated with sodium hyaluronate and those treated with a placebo (Healon buffer), with regard to the amount of postoperative pain or the rapidity of corneal epithelial healing.

CONCLUSIONS

Topical sodium hyaluronate administration showed no effect on pain or corneal epithelial healing following photorefractive keratectomy in this study.