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Background/aims: Endothelial cell dysfunction in the ocular circulation may contribute to normal pressure glaucoma (NPG). This study aimed to investigate the contributions made by endothelium derived relaxing factors to relaxation of (1) subcutaneous resistance arteries from patients with NPG, and (2) porcine ciliary arteries. Methods: Human gluteal resistance arteries were isolated from seven patients with NPG and matched controls. Human and porcine arteries produced endothelium dependent relaxation when exposed to acetylcholine (ACh) (10 29 23610 25 M) or bradykinin (10 210 23610 26 M). Pharmacological agents were used to inhibit the nitric oxide pathway (L-arginine analogues, soluble guanylate cyclase inhibitor), endothelium derived hyperpolarising factor (EDHF) activity (potassium channel antagonists), and prostaglandin synthesis (cyclo-oxygenase inhibitors). Results: In all arteries, endothelium dependent relaxation was attenuated by nitric oxide (NO) inhibition or potassium channel blockade, but not by cyclo-oxygenase inhibition. Inhibition of ACh mediated relaxation by potassium channel antagonists was greater (p,0.05) in patients with NPG (Emax, 55.4% (SD 8.16%) relaxation, n = 4) than controls (Emax, 81.8% (6.0%), n = 5). In contrast, combined inhibition of NO synthase (NOS) and cyclo-oxygenase produced similar inhibition of ACh mediated relaxation in both groups. Conclusions: The enhanced contribution of EDHF to ACh mediated relaxation in systemic resistance arteries from NPG patients may contribute to the maintained endothelium mediated relaxation in these vessels. EDHF also contributes significantly to bradykinin mediated relaxation in porcine ocular ciliary arteries. Therefore, similar changes in the balance of relaxing factors in the ocular circulation could influence the response of the eye to vascular endothelial dysfunction in NPG.

SUMMARY A technique is described for producing an iridotomy in the treatment of closed-angle and secondary glaucoma using a single pulse from a dye laser. It was successful in 28 out of 32 eyes treated, and no significant complications were encountered.Previous publications (Perkins and Brown, 1973;Brown, 1977) have shown that it is possible to produce a functioning iridotomy with a combination of argon and ruby lasers. This had the advantage of being an outpatient procedure, particularly useful for cases in which conventional surgery was contraindicated, but had the disadvantage that several treatments were required to achieve complete penetration of the iris. Theoretical studies (Wheeler, 1977) and animal experiments indicated that lasers with a shorter pulse, such as that from a dye laser, would produce a complete iridotomy with 1 pulse (Bass et al., 1977). This method has been used on 32 eyes of 28 patients in most of whom conventional surgery was contraindicated. Four patients had both eyes treated, 1 being a case of Marfan's syndrome (Table 1). MethodsTwo tunable dye lasers were used: Electrophotonics Model 33 and Electrophotonics Model 43. The dyes employed to date were (1) cresyl violet, (2) rhodamine 640; both of these were in a pure methanol solution and tuned to X 633 nm; (3) rhodamine 6G (? 590 nm) and coumarin 102 (X 488 nm), which were prepared initially in solution with methanol and subsequently in a methanol/water mixture of 1: 1.