Aim: To comprehensively evaluate the effects of dorzolamide on the choroidal and retinal circulat... more Aim: To comprehensively evaluate the effects of dorzolamide on the choroidal and retinal circulation in patients with age related macular degeneration (AMD). Methods: In this randomised, double masked, parallel study, 36 non-exudative AMD patients were randomised in a 2 to 1 fashion to placebo versus topical dorzolamide and underwent assessment of their choroidal and retinal circulation. Scanning laser ophthalmoscope indocyanine green angiograms (ICGA) were analysed by a new area dilution analysis technique. Four areas in the perifoveal region and two areas in the temporal peripapillary region were evaluated by plotting intensity of fluorescence of each area over time. The means of the choroidal filling times and the heterogeneity of the filling times were assessed. Scanning laser ophthalmoscope fluorescein angiography (FA) was evaluated for retinal arteriovenous passage (AVP) times by plotting intensity of fluorescence of retinal vessels over time. Assessment was performed at baseline and at 4 months. Results: Compared to placebo, AMD patients treated with dorzolamide showed a significantly increased rapidity of choroidal filling in the superior and inferior peripapillary regions (p=0.007, p=0.02, respectively). No significant difference in choroidal filling times was found in any of the perifoveal areas (p=0.9). Also, on FA assessment, treatment with dorzolamide showed no statistical differences in AVP times (p=0.19). Conclusions: Dorzolamide may increase peripapillary choroidal perfusion in non-exudative AMD patients. Further studies are merited.
The Relationship Between Retrobulbar and Choroidal Hemodynamics in Non-Neovascular Age-Related Macular Degeneration
Ophthalmic surgery, lasers & imaging retina, 2007
To evaluate the relationship between retrobulbar and choroidal hemodynamics in non-neovascular ag... more To evaluate the relationship between retrobulbar and choroidal hemodynamics in non-neovascular age-related macular degeneration. Thirteen patients with age-related macular degeneration were assessed by both color Doppler imaging and scanning laser ophthalmoscope indocyanine green (ICG) angiography. Color Doppler imaging was used to measure peak systolic and end diastolic velocity (from which the resistance index, a measure of the resistance to flow downstream, was calculated) in the retrobulbar vessels. Scanning laser ophthalmoscope ICG angiograms were analyzed by area dilution analysis for quantitative choroidal fluorescence intensity assessment. Color Doppler imaging parameters were correlated with scanning laser ophthalmoscope ICG area dilution analysis parameters. A good correlation was found between the posterior ciliary arteries resistance index and scanning laser ophthalmoscope ICG area dilution analysis fluorescence duration. Scanning laser ophthalmoscope ICG area dilution analysis "duration" may serve as an alternative to color Doppler imaging in assessing the resistance to blood flow in the posterior ciliary arteries.
Purpose: To investigate differences in ocular blood flow between people of African (AD) and Europ... more Purpose: To investigate differences in ocular blood flow between people of African (AD) and European descent (ED) with healthy eyes. Methods: Retrobulbar and retinal capillary blood flow was assessed in one eye of 58 participants (24 AD, 34 ED) with healthy eyes with systemic blood pressure lower than 140/90. Retrobulbar blood flow was measured in the ophthalmic artery (OA), central retinal artery (CRA), nasal (NPCA) and temporal posterior ciliary arteries (TPCA). Peak systolic velocity (PSV), end diastolic velocity (EDV) and resistive index (RI) were assessed. Retinal capillary blood flow was assessed using mean retinal flow and avascular space defined as the percent of area measured with no blood flow. Groups were compared using t-tests and Pearson correlations were compared using Fisher r-toz transformation. Results: Compared to people of ED, people of AD had significantly lower EDV in the NPCA (p=0.01), and higher RI in the CRA (p=0.04) and TPCA (p=0.01). No significant differences were observed in mean retinal capillary flow or avascular area. In the CRA, a significant positive correlation was observed between pattern standard deviation (PSD) and PSV (p=0.02) and this correlation was significantly different from that observed in the ED group (p=0.01). A significant correlation was also observed between PSD and EDV (0.04) in the AD group. This study suggests that retrobulbar blood flow is lower in healthy eyes in persons of AD compared to ED. This may provide a mechanism through which people of AD are at increased risk for ophthalmic diseases such as glaucoma.
Aim: To determine if perfusion per unit tissue volume of retinal nerve fibre layer and optic nerv... more Aim: To determine if perfusion per unit tissue volume of retinal nerve fibre layer and optic nerve head in the inferior sector is lower than in the superior sector. Methods: Heidelberg retinal tomogram (HRT) for topographic measurement of optic nerve head and retinal nerve fibre layer and Heidelberg retinal flowmeter (HRF) for retinal blood flow were performed on 19 normal healthy subjects. Measurements from the superior and inferior sectors were compared. The perfusion/nerve fibre ratio (PNR); the blood flow per unit retinal nerve fibre tissue volume, was calculated in each sector with a formula; HRF flow measurements divided by HRT measurements. Results: Retinal nerve fibre layer thickness in the inferior retina was significantly higher than in the superior retina (p<0.05). There were, however, no differences in retinal blood flow between the superior and inferior retinal sectors. The PNR in the inferior sector were significantly lower than in the superior sector (p=0.047 for HRF mean flow/rim volume and p = 0.0282 for HRF 75th percentile flow/rim volume). Conclusions: The inferior sector of retinal nerve fibre layer and optic nerve head may have lower blood flow per unit nerve tissue volume compared to the superior sector. This result suggests that the inferior sector is more vulnerable to elevated intraocular pressure (IOP) and ischaemic insults in glaucomatous optic neuropathy.
Glaucoma Patients with Diabetes Have Increasing Vascular Resistance in the Ophthalmic and Central Retinal Arteries Compared to Glaucoma Patients without Diabetes
Investigative Opthalmology & Visual Science, 2019
To identify the factors associated with retinal vessel diameters in the population of the Thessal... more To identify the factors associated with retinal vessel diameters in the population of the Thessaloniki Eye Study. METHODS. Cross-sectional population-based study (age ‡ 60 years). Subjects with glaucoma, late age-related macular degeneration, and diabetic retinopathy were excluded from the analyses. Retinal vessel diameters were measured using the IVAN software, and measurements were summarized to central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and arteriole to venule ratio (AVR). RESULTS. The analysis included 1614 subjects. The hypertensive group showed lower values of CRAE (P ¼ 0.033) and AVR (P ¼ 0.0351) compared to the normal blood pressure (BP) group. On the contrary, the group having normal BP under antihypertensive treatment did not have different values compared to the normal BP group. Diastolic BP (per mm Hg) was negatively associated with CRAE (P < 0.0001) and AVR (P < 0.0001), while systolic BP (per mm Hg) was positively associated with CRAE (P ¼ 0.001) and AVR (P ¼ 0.0096). Other factors significantly associated included age, sex, alcohol, smoking, cardiovascular disease history, ophthalmic medication, weight, and IOP; differences were observed in a stratified analysis based on BP medication use. Our study confirms previous reports about the association of age and BP with vessel diameters. The negative correlation between BP and CRAE seems to be guided by the effect of diastolic BP as higher systolic BP is independently associated with higher values of CRAE. The association of BP status with retinal vessel diameters is determined by diastolic BP status in our population. Multiple other factors are also independently associated with retinal vessel diameters.
Purpose The incidence of eye disease increases with age and can often be linked to worsening card... more Purpose The incidence of eye disease increases with age and can often be linked to worsening cardiovascular function and increasing intraocular pressure. Estrogen is known to have vasodilatory effects in the systemic circulation. Decreased estrogen levels during menopause may therefore complicate or contribute to ocular pathologies as estrogen receptors are found in both retinal and choroidal tissue. The purpose of this investigation was to determine the effects of menopause on visual function and cardiovascular and ocular hemodynamics. Methods Twelve premenopausal and 24 postmenopausal women were evaluated at the Indiana University School of Medicine during a single study visit. Vision screening and ocular blood flow evaluations were performed, including blood pressure, heart rate, visual acuity, contrast sensitivity, intraocular pressure, and retinal capillary and retrobulbar blood flow imaging. Vision and ocular hemodynamics were compared using unpaired Student t-tests with pp<...
Diabetic retinopathy (DR) and diabetic macular edema (DME) are leading causes of blindness in the... more Diabetic retinopathy (DR) and diabetic macular edema (DME) are leading causes of blindness in the working-aged population of most developed countries. The increasing number of persons with diabetes worldwide suggests that DR/DME will continue to be major contributors to vision loss and associated functional impairment for years to come. Early detection of retinopathy in persons with diabetes is critical in preventing visual loss, but current methods of screening fail to identify a sizable number of high-risk patients. The control of diabetes-associated metabolic abnormalities (ie, hyperglycemia, hyperlipidemia, and hypertension) is also important in preserving visual function, as these conditions have been identified as risk factors for both the development and progression of DR/DME. The non-pharmacologic interventions for DR/DME, laser photocoagulation and vitrectomy, only target advanced stages of disease. Several biochemical mechanisms, including increased vascular endothelial gr...
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Papers by Alon Harris