The role of retrobulbar and retinal circulation on optic nerve head and retinal nerve fibre layer structure in patients with open-angle glaucoma over an 18-month period.

BACKGROUND/AIMS: Evidence suggests that vascular abnormalities play a role in the pathogenesis of open-angle glaucoma (OAG) in some patients. This study aims to assess changes in retrobulbar and retinal blood flow over time in patients with glaucoma and examine their relationship to glaucomatous progression, as determined by retinal and optic nerve structure. METHODS: In this observational study, 103 patients with OAG were examined at baseline and 18 months follow-up. Retrobulbar blood flow was measured by colour Doppler imaging in the ophthalmic, central retinal and temporal posterior ciliary artery (TPCA) and nasal short posterior ciliary artery. Retinal capillary blood flow was measured by confocal scanning laser Doppler. Peripapillary retinal nerve fibre layer thickness was assessed by optical coherence tomography. Non-parametric Wilcoxon signed ranks tests were used to assess for any statistically significant changes between the baseline and 18-month visits for the retrobulbar and retinal flow, as well as the structural parameters. RESULTS: In general, retinal and retrobulbar blood flow parameters decreased over 18 months. Thinning of the optic disc rim and increase in cup area were associated with a higher resistance index (p=0.0334) and lower peak systolic velocity of TPCA (p=0.0282), respectively. A higher amount of retinal zero pixel blood flow correlated with a greater increase in cup/disc ratio (p=0.0170). CONCLUSIONS: Reductions in retrobulbar and retinal blood flow over time were associated with structural glaucomatous progression, as indicated by retinal and optic nerve changes.

Cerebrospinal fluid pressure and glaucoma: regulation of trans-lamina cribrosa pressure.

Increased trans-lamina cribrosa pressure difference (TLCPD), the difference of intraocular pressure (IOP) and orbital cerebrospinal fluid pressure (CSF-P), has been investigated as a possible risk factor in glaucoma pathogenesis. In fact, lower CSF-P in the setting of normal IOP has been implicated as a potential risk factor for normal tension glaucoma. Increased TLCPD has been associated with decreased neuroretinal rim area and increased visual field defects. Furthermore, dysregulation of systemic blood pressure has been associated with changes in IOP. Recent studies have also suggested that increased body mass index (BMI) is associated with decreased prevalence of glaucoma, which may be due to an increased CSF-P with increased BMI found in many studies. Given the interaction of various pressures, their role in glaucoma pathophysiology has come under investigation and warrants further study in order to better understand the aetiology and progression of glaucoma.

Nanotechnology and glaucoma: a review of the potential implications of glaucoma nanomedicine.

The purpose of this review is to discuss the evolution of nanotechnology and its potential diagnostic and therapeutic applications in the field of ophthalmology, particularly as it pertains to glaucoma. We reviewed literature using MEDLINE and PubMed databases with the following search terms: glaucoma, nanotechnology, nanomedicine, nanoparticles, ophthalmology and liposomes. We also reviewed pertinent references from articles found in this search. A brief history of nanotechnology and nanomedicine will be covered, followed by a discussion of the advantages and concerns of using this technology in the field of glaucoma. We will look at various studies concerning the development of nanomedicine, its potential applications in ocular drug delivery, diagnostic and imaging modalities and, surgical techniques. In particular, the challenges of assuring safety and efficacy of nanomedicine will be examined. We conclude that nanotechnology offers a novel approach to expanding diagnostic, imaging and surgical modalities in glaucoma and may contribute to the knowledge of disease pathogenesis at a molecular level. However, more research is needed to better elucidate the mechanism of cellular entry, the potential for nanoparticle cytotoxicity and the assurance of clinical efficacy.

The influence of retinal blood flow on open-angle glaucoma in patients with and without diabetes.

PURPOSE: To evaluate the impact of retinal blood flow on optic nerve head (ONH) morphology in patients with open-angle glaucoma (OAG) with and without diabetes mellitus (DM). METHODS: A total of 66 patients with OAG (14 with DM, 52 without DM) were assessed at baseline and 3-year follow-up for retinal capillary blood flow using confocal scanning laser Doppler and ocular structure using Heidelberg retinal tomography and optical coherence tomography. RESULTS: Change in retinal tissue with zero blood flow in the superior and inferior retina was found to have a strong correlation with ONH changes in diabetic patients (r≥0.90, p≤0.03); however, no relation was found in the nondiabetic cohort. There were also significant changes in inferior mean flow that strongly correlated with changes in cup area (r = 0.97, p = 0.0029), cup/disc area ratio (r = 0.96, p = 0.0070), linear cup/disc ratio (r = 0.93, p = 0.0172), rim area (r = -0.97, p = 0.0036), and rim volume (r = -0.95, p = 0.0084) in diabetic patients only, while changes in the superior mean flow were only significantly associated with cup area (r = -0.30, p = 0.0498), cup volume (r = -0.36, p = 0.0178), and rim volume (r = 0.35, p = 0.0193) in nondiabetic patients. CONCLUSIONS: In this cohort of patients with OAG, changes in retinal capillary blood flow correlated more strongly with changes in ONH morphology in patients with DM than in those without DM. These data suggest that changes in retinal blood flow may play a larger role in glaucomatous ONH progression in patients with OAG with DM.

Generic medications in ophthalmology.

The purpose of this review is to discuss the process of genericisation of medications in the US and Europe with a focus on ophthalmic drugs. Regulatory guidelines of the US Food and Drug Administration and the European Medicines Agency will be discussed, and the advantages and concerns of genericisation will be explored. We will look at various studies concerning the safety and efficacy of generic drugs compared to their branded counterparts. In particular, the challenges of assuring bioequivalence and therapeutic equivalence in topical ophthalmic drugs will be examined.

Should Men and Women be Managed Differently in Glaucoma?

INTRODUCTION: To assess differences in associations of ocular perfusion pressure (OPP) as well as retinal and retrobulbar blood flow between men and women with primary open angle glaucoma (OAG). METHODS: A total of 116 patients with OAG (age 66.9 ± 10.9 years, 70 females) participating in the Indianapolis Glaucoma Progression Study were assessed for OPP, retinal microcirculation, and retrobulbar blood flow. Confocal scanning laser Doppler flowmetry measured peripapillary retinal capillary blood flow. Color Doppler imaging measured peak systolic (PSV) and diastolic blood flow velocities and vascular resistance in the ophthalmic (OA), central retinal (CRA), and nasal and temporal short posterior ciliary arteries (N/T PCA). Bivariate Spearman correlation and multivariate linear regression analyses were performed. RESULTS: In female patients with OAG, inferior retinal capillary flow was associated with OPP (r = 0.246, P = 0.044). In men, superior and inferior sector retinal blood flow was associated with OPP (r = -0.402, P = 0.006 and r = -0.357, P = 0.016, respectively). There was no statistically significant association between OPP and retrobulbar blood vessel flow velocities in male patients with OAG but there was an association between OA and TPCA PSV and OPP in female patients with OAG (r = 0.290, P = 0.015 and r = 0.357, P = 0.002, respectively). In female patients with OAG, multivariate regression showed no statistically significant effect of any variable on the superior retinal capillary blood flow, with CRA PSV as a sole predictor to the inferior retinal sector (partial rho = 0.302, P = 0.015) and in male patients with OAG, superior sector retinal capillary blood flow was independently associated with intraocular pressure (partial rho = -0.371, P = 0.016) and OPP (partial rho = -0.456, P = 0.002) with a trend of association with OPP in the inferior retina (partial rho = -0.301, P = 0.053). CONCLUSIONS: There was a positive linear association between retinal microcirculation and OPP in females and a negative association in males. Male and female patients with OAG may differ in their vascular autoregulation in response to changes in OPP.