Ocular blood flow and oxygen delivery to the retina in primary open‐angle glaucoma patients: the addition of dorzolamide to timolol monotherapy

Abstract

ABSTRACT.Purpose: To assess the effects of adding dorzolamide to timolol monotherapy on ocular haemodynamics and retinal oxygen saturation in patients with primary open-angle glaucoma (POAG).Methods: Twenty-four patients (12 healthy, 12 with POAG) were treated with dorzolamide ⁄ timolol combination (DT) versus timolol maleate 0.5% twice daily in a randomized, crossover, double-blind study conducted over a period of 18 months. Patients received each treatment for 8 months then crossed over to the other treatment after a 1-month washout and second baseline. Goldmann applanation tonometry, Heidelberg retinal flowmetry (HRF), colour Doppler imaging (CDI) and retinal photographic oximetry were performed at each visit.Results: DT significantly reduced intraocular pressure (IOP) in both glaucomatous [right eye (OD) )13.15%, left eye (OS) )14.43%; p < 0.036] and non-glaucomatous (OD )12.4%, OS )13.88%; p < 0.039) patients compared to timolol after 8 months of treatment. DT significantly reduced the number of zero blood flow pixels in the superior ()39.72%; p < 0.014) and inferior ()51.44%; p < 0.008) retina in the nonglaucomatous group and inferior retina in the glaucomatous group ()55.38%, p < 0.006). The continuation of timolol monotherapy from baseline did not change (p < 0.05) any measured parameter and neither treatment had a significant effect (p < 0.05) on retinal oximetry or CDI parameters. Conclusion:The addition of dorzolamide to timolol monotherapy decreases IOP and increases retinal blood flow in the superficial retinal vasculature in both glaucomatous and healthy patients following 8 months of treatment. The combination of increased retinal blood flow with consistent oxygen saturation may potentially increase oxygen delivery to the retina.

Oxygen saturation measurements of the retinal vasculature in treated asymmetrical primary open-angle glaucoma using hyperspectral imaging

“…Studies using various retinal oximetry devices to measure the oxygen saturation of the retinal vasculature in glaucoma have been reported. [12][13][14][15][16][17][18][19][20] Hyperspectral imaging combines spectroscopy with digital imaging whereby spectral data (using numerous contiguous wavelengths of light) are obtained in every pixel of an image plane. An oximetry study of the retinal vascular network using a hyperspectral imaging system (images acquired using more than three contiguous wavelengths) in glaucoma has not yet been reported.…”

Effect of Trabeculectomy on Ocular Hemodynamic Parameters in Pseudoexfoliative and Primary Open-angle Glaucoma Patients

“…Some data support increased blood flow and the enhancement of OBF regulation with carbonic anhydrase inhibitors. Several studies have shown dorzolamide's ability to increase various measures of OBF parameters, [10][11][12] although other studies failed to show similar effect. 13,14 Dorzolamide's vasodilatory effects might be explained by induced acidosis in local tissues.…”

Comparison of Intraocular Pressure, Blood Pressure, Ocular Perfusion Pressure and Blood Flow Fluctuations During Dorzolamide Versus Timolol Add-On Therapy in Prostaglandin Analogue Treated Glaucoma Subjects

“…Our study findings may be explained by the vasodilatative effect of dorzolamide. Dorzolamide hydrochloride is perhaps the most vasoactive topical glaucoma treatment and several studies have shown it to increase various measures of ocular blood flow parameters [19,20,21,22,23,24], although other studies have failed to show similar effect [25,26,27]. Several authors when analysing normal subjects found that a single instillation of dorzolamide showed no significant effects on the blood flow through major retinal vessels [28,29,30,31,32].…”

“…showed that addition of dorzolamide to timolol monotherapy decreases IOP and increases retinal blood flow in the superficial retinal vasculature in both glaucomatous and healthy patients. The combination of increased retinal blood flow with consistent oxygen saturation may potentially increase oxygen delivery to the retina [38]. …”