Normalization of Ocular Perfusion by Dorzolamide in NTG Patients: Doppler Sonographic Measurements and Mathematical Modelling

Abstract

 

Abstract:

 

Reduced perfusion in short posterior ciliary artery, which supplies the optic nerve head with blood, is hypothesized to play a role in the pathogenesis of normal tension glaucoma (NTG). In the present study it is investigated, if dorzolamide can restore ocular perfusion to normal in NTG patients. A mathematical model is proposed in order to get insight into dorzolamide’s mechanism of action.

 

Peak systolic and end–diastolic blood flow velocities (PSV and EDV resp.) in the short posterior ciliary artery (SPCA) and in the ophthalmic artery (OA) were assessed by color Doppler imaging (CDI) shortly before and after an one–month treatment with dorzolamide (30 patients). A mathematical model describing the hemodynamics in SPCA on basis of Hagen–Poiseuille’s and Ohm’s law is developed. Thereby, the blood supply of the eye is functionally distributed into an extraocular supplying component and its dependent vasculature.

 

Compared to healthy volunteers NTG patients have reduced blood flow velocities in the SPCA, but not in the OA. One–month treatment with dorzolamide lead to a significant increase of PSV and EDV in the SPCA and again not in the OA. In more than 75% of the patients PSV and EDV were normalized by dorzolamide treatment. From the proposed mathematical model, it can be assumed that dorzolamide most likely influences the tone of the intraocular vasculature and the rise in blood flow velocity in the ciliary arteries is due to an increase in the diameter of the intraocular vasculature by 7 to 10%.

 

 

^{Topically applied dorzolamide has the capability to normalize blood flow velocities in the SPCA of NTG patients. This effect is most likely due a direct impact of dorzolamide on the tone of the intraocular arterial vasculature. The results from the mathematical model additionally help to better understand CDI measurements.}

 

 

Keywords: blood supply • drug toxicity/drug effects • computational modeling