Effects of dorzolamide/timolol fixed combination on retrobulbar hemodynamics in pseudoexfoliative glaucoma

Retrobulbar Short Posterior Ciliary Artery Hemodynamics in Patients with Pseudoexfoliation Glaucoma and Primary Open-Angle Glaucoma

Purpose

To investigate retrobulbar blood flow changes in the short posterior ciliary arteries (SPCAs) in patients with pseudoexfoliation glaucoma (PEG) and primary open-angle glaucoma (POAG).

Methods

In this prospective study, there were 22 eyes in the PEG group, 28 eyes in the POAG group, and 28 eyes with senile cataract in the control group. Peak systolic velocity (PSV), end-diastolic velocity (EDV), mean velocity (Vm), and resistivity index (RI) parameters of the temporal and nasal SPCAs were compared between the study groups.

Results

Mean temporal PSV, EDV, and Vm value were significantly lower in both the POAG group and the PEG group (P = 0.049, P = 0.004, P = 0.020), respectively. Temporal SPCA RI values were not significantly different between the groups (P = 0.115).

Conclusion

There are retrobulbar blood flow changes in glaucomatous compared to nonglaucomatous eyes. However, SPCAs blood flow characteristics are similar between PEG and POAG subtypes.

Synergistic Effect of Acetazolamide-(2-hydroxy)propyl β-Cyclodextrin in Timolol Liposomes for Decreasing and Prolonging Intraocular Pressure Levels

The purpose of this study was to design, for the first time, a co-loaded liposomal formulation (CLL) for treatment of glaucoma including timolol maleate (TM) in the lipid bilayer and acetazolamide (Acz)-(2-hydroxy)propyl β-cyclodextrin (HPβCD) complexes (AczHP) solubilized in the aqueous core of liposomes. Formulations with TM (TM-L) and AczHP (AczHP-L), separately, were also prepared and characterized. A preliminary study comprising the Acz/HPβCD complexes and their interaction with cholesterol (a component of the lipid bilayer) was realized. Then, a screening study on formulation factors affecting the quality of the product was carried out following the design of the experiment methodology. In addition, in vitro release and permeation studies and in vivo lowering intraocular pressure (IOP) studies were performed. The results of the inclusion complexation behavior, characterization, and binding ability of Acz with HPβCD showed that HPβCD could enhance the water solubility of Acz despite the weak binding ability of the complex. Ch disturbed the stability and solubility parameters of Acz due to the fact of its competence by CD; thus, Chems (steroid derivative) was selected for further liposome formulation studies. The optimization of the lipid bilayer composition (DDAB, 0.0173 mmol and no double loading) and the extrusion as methods to reduce vesicle size were crucial for improving the physico-chemical properties and encapsulation efficiency of both drugs. In vitro release and permeation studies demonstrated that the CLL formulation showed improvement in in vitro drug release and permeation compared to the liposomal formulations with a single drug (TM-L and AczHP-L) and the standard solutions (TM-S and AczHP-S). CLL showed high efficacy in reducing and prolonging IOP, suggesting that the synergistic effect of TM and Acz on aqueous humor retention and the presence of this cyclodextrin and liposomes as permeation enhancers are responsible for the success of this strategy of co-loading for glaucoma therapy.