Ophthalmology Poster Session
Glaucoma is a chronic disorder characterised by a triad of symptoms, consisting of an increase in intraocular pressure (IOP), the progressive deterioration in the visual field and the appearance of an optic neuropathy (1,2).
Beta-blockers are the elective drugs for the treatment of chronic open-angle glaucoma (3). They lead to a reduction in IOP by inhibiting the production of acqueous humor, probably due to direct action on the ciliary body epithelium (4,5,6). Beta-blockers can be divided on the basis of their pharmacological properties into beta 1-selective and non-selective. The former act more selectively on beta 1 receptors, while the latter act on the beta 1 and on the beta 2 receptors. The non-selective ones can be further divided according to the presence or absence of intrinsic sympathomimetic activity. This activity refers to the capacity of the drug to cause even slight, early activation of the adrenergic receptor, obviously an inferior activity to complete agonists. Carteolol is a non-selective beta-blocker with intrinsic sympathomimetic activity.
The aim of this study was to assess the efficacy of Carteolol in improving the blood flow at the level of the orbital vessels and in blocking the development of glaucomatous optic neuropathy.
Materials and Methods
We studied 40 patients, 25 males and 15 females, aged between 53 and 68 years (mean 63.4) with chronic simple open-angle glaucoma. The patients were divided in a random, double-blind manner into two groups. Group A was administered a non-selective beta-blocker (Timolol maleate 0.5%) twice a day. Group B was administered a non-selective drug with intrinsic sympathomimetic activity (Carteolol 2%). All the patients were examined with an Color Doppler Imaging (CDI) of the ophthalmic artery (OA) and the posterior ciliary arteries (PCA's) and computerised perimetry before starting treatment and after one year of treatment. CDI was performed using an Asynchronous-Hitachi ecograph with a 7.5 MHz linear probe. The visual field examination was performed with a Humphrey 740 perimeter and the 30.2 Full Threshold program.
Statistical analysis was performed, using the Student t test for paired and unpaired data, on the variations in the peak systolic velocity (PSV) and the resistance indices (RI) in the vessels studied with Color Doppler imaging as well as the MD and the CPSD of computerised perimetry
The results are summarized in Table 1.
*comparision between Timolol maleate and Carteolol
Tab 1 – Statistical assessment of the variation in the the perimetric and flow indeces after topical treatment with Timolol maleate and Carteolol.After 18 months of therapy, a reduction of resistence index was observed in patients treated with carteolol, in the posterior ciliary arteries (p <0.001) with an improvement of MD (p < 0.002) and CPSD (p < 0.002) indexes of the authomatic perimetry.
Discussion and Conclusion
This study revealed how a good pressure compensation is obtained with Carteolol even if the tonometric values were slightly higher than the control group. The reduction in ocular pressure is accompanied by a reduction in the resistance indices for the posterior ciliary arteries with statistically significant improvement in the perimetric indices as compared with the group treated with Timolol maleate, where there was a progressive worsening. The significant reduction in the PCA's resistance indices in the group treated with Carteolol can be linked to the drug interaction with the vessel endothelium. This leads to intraluminal release of vasodilating prostacyclins, as well as the extraluminar release of vasodilating endothelial factors (in particular nitric oxide) as a result of the activation of the alpha-2 adrenergic receptors (7).
We believe that Carteolol, although it has a similar pressure-reducing effect to Timolol maleate, is also a drug which is effective in blocking glaucomatous optic neuropathy, reducing the posterior ciliary artery resistance and thus improving circulation at the head of the optic nerve.
1. Phelps CD: Glaucoma: General concepts. In Duane's Clinical Ophthalmology (Tasman W, Jaeger EA, eds.) vol 3. JB Lippincot, Philadelphia, 1993, chap 42, pp1-8.
2. Migdal CD: Primary open-angle glaucoma. In Duane's Clinical Ophthalmology (Tasman W, Jaeger EA, eds.) vol 3. JB Lippincottz Philadelphia, 1993, chap 52, pp 1-32.
3. Hurvitz LM et al: New developments in the drug treatment of glaucoma. Drugs 41:514-32,1991.
4. Araise M, Takase M: Effects of pilocarpine and carteolol, a new beta-adrenergic blocking agent, on human aqueous humor dynamics. Acta Soc. Ophthalmol. Jpn., 84, 12, 2085, 1980.
5. Nathanson JA: Human ciliary process adrenergic receptor: pharmacological characterization. Invest. Ophthalmol. Vis. Sci.,21,798,1981.
6. Trope GE, Clark B: Beta-adrenergic receptors in pigmented ciliary process. Br. J. Ophthalmol., 66,788,1982.
7. Janczewski P, Boulanger C, Iqbal A, Vanhoutte PM: Endothelium-dependent effects of Carteolol. J. Pharmacol. Exp. Ther.,247,590-5,1988.
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|Cellini, M.; Moretti, M.; Versura, P.; Rossi, A.; Torreggiani, A.; (1998). Influence of Carteolol and Timolol on Visual Field and Ocular Blood Flow in Patients with Glaucoma. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Available at URL http://www.mcmaster.ca/inabis98/ophthalmology/cellini0571/index.html|
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