Alon Harris

Intravitreal triamcinolone with photodynamic therapy for subfoveal choroidal neovascularisation in age related macular degeneration

Aims: To report the effects of intravitreal triamcinolone acetonide (iTAAC) injections as an adjunctive treatment to photodynamic therapy (PDT) with verteporfin for new subfoveal choroidal neovascularisation (CNV) in age related macular degeneration (AMD). Methods: We retrospectively reviewed the records of all AMD patients who had iTAAC within 6 weeks of their first PDT and had a follow up of one year or longer. The proportion of eyes after one year follow up that lost or gained ⩾15 and ⩾30 ETDRS letters, baseline and one year lesion greatest linear dimension (GLD), number of PDTs, and side effects were assessed. Results: Fourteen patients were evaluated. Eleven received one initial combined treatment and three received an additional combined treatment after 6 months. Median follow up was 18 months (range 12 to 25 months). Overall, 7% gained ⩾30 letters, 50% maintained stable vision, 14% lost 15–29 letters, and 29% lost ⩾30 letters. Overall, mean GLD increased from 2580 (SD 1088) µm to 3946 (SD 1503) µm (p = 0.01). The mean number of PDTs during the first year was 2.57. Side effects were mild intraocular pressure elevation in 28.5% and cataract progression in 50% of phakic eyes. Conclusions: iTAAC with PDT in AMD was found to be relatively safe and had reasonable results for lesions with some classic component.

Laser Doppler flowmetry measurement of changes in human optic nerve head blood flow in response to blood gas perturbations.

PURPOSE The objective of this study was to establish the ability of laser Doppler flowmetry to detect relative changes in human optic nerve head hemodynamics caused by physiologic blood gas perturbations. METHODS Laser Doppler flowmetry permits the noninvasive assessment of relative blood velocity, volume, and flow (flux) in a sample volume of the nerve head. Such measurements were performed in two groups of healthy subjects. The first group (n = 11) was tested during normal room air breathing and then while breathing 100% oxygen (isocapnic hyperoxia). The second group (n = 10) was also tested under normal conditions as well as during isoxic hypercapnia (+ 15% end-tidal carbon dioxide). Results were analyzed by paired t tests. RESULTS Hyperoxia created a significant 25% (p = 0.002) decrease in optic nerve head blood flow, with blood volume decreased by 9% (p = 0.095) and blood velocity reduced by 13% (p = 0.154) compared to the room air condition. During hypercapnia, optic nerve head blood flow was increased by 28% (p = 0.012), with blood volume increased by 22% (p = 0.017) and blood velocity increased by 9% (p = 0.218) as compared to the normal room air condition. CONCLUSION Blood flow in the optic nerve head capillaries changes in response to hyperoxia and hypercapnia as demonstrated in the brain and retina. Laser Doppler flowmetry permits the noninvasive assessment of these responses in humans under conditions within the physiologic range.

A comparative study of the effects of brinzolamide and dorzolamide on retinal oxygen saturation and ocular microcirculation in patients with primary open-angle glaucoma.

Aims: To assess the effects of brinzolamide and dorzolamide on ocular haemodynamics and retinal oxygen saturation in patients with primary open-angle glaucoma (OAG). Methods: Fifteen patients with OAG were evaluated in a randomised, cross-over, double-blind study. They were treated with either brinzolamide or dorzolamide for 3 months and then crossed-over after a 4-week washout period. They were given timolol during a 4-week run-in period and during washout. The following were performed after run-in, after washout and after each treatment period: adverse events check, measurement of visual acuity, contrast sensitivity, blood pressure, heart rate, and intraocular pressure, and fundus examination. Ocular blood flow was assessed using confocal scanning laser Doppler flowmetry (HRF) and colour Doppler imaging (CDI). Retinal oxygenation levels were determined using a non-invasive measurement of haemoglobin oxygen saturation by digital photographic fundus oximetry. Results: Both brinzolamide and dorzolamide reduced the number of zero-flow pixels in the retina as measured by HRF, suggesting an increase in retinal blood flow (−6.86 and −0.452 respectively) with brinzolamide treatment resulting in fewer zero-flow pixels than dorzolamide (−6.41) (p = 0.024). Both brinzolamide and dorzolamide increased oxygen saturation in the retina as measured by photographic retinal oximetry in the superior (0.82 (p = 0.002) and 0.87 (p = 0.005)) and inferior (0.88 (p = 0.035) and 0.82 (p = 0.002)) retinal veins. No significant changes were found in CDI measurements of the retrobulbar blood supply during either treatment. Conclusion: This pilot study suggests that brinzolamide and dorzolamide may increase retinal oxygen saturation in patients with OAG.

Effect of acute intraocular pressure changes on short posterior ciliary artery haemodynamics

BACKGROUND/AIMS Vascular insufficiency due to abnormal autoregulation has been proposed as a major factor in the development of glaucoma. The anterior optic nerve is primarily perfused by the short posterior ciliary arteries. The autoregulatory capacity of these vessels in response to acutely elevated intraocular pressure (IOP) was examined in normal human subjects. METHODS Colour Doppler imaging was performed on the short posterior ciliary arteries of 10 normal subjects at baseline and during four incremental IOP elevations. Using a scleral suction cup placed temporally, IOP was elevated to approximately 25, 30, 40, and 50 mm Hg. Additional measurements were performed immediately after pressure release. Systolic and diastolic flow velocities were measured and Pourcelot’s resistivity index was calculated. RESULTS Systolic and diastolic flow velocities decreased linearly with each incremental increase in IOP (p<0.001). Pourcelot’s resistivity index increased linearly with each incremental increase in IOP (p<0.001). Changes in end diastolic velocity, peak systolic velocity, and Pourcelot’s resistivity index were linearly related to changes in IOP. CONCLUSION The normal healthy eye is not able to autoregulate to maintain PCA blood flow velocities in response to acute large elevations in IOP.

Capillary density and retinal diameter measurements and their impact on altered retinal circulation in glaucoma: A digital fluorescein angiographic study

Aim: Normal pressure glaucoma (NPG) patients exhibit prolonged retinal arteriovenous passage times in fluorescein angiography and colour Doppler imaging suggests increased resistance downstream from the central retinal and posterior ciliary arteries. The aim of the study was to elucidate the morphological source of decreased perfusion and increased resistance of the ocular circulation in NPG. Methods: Retinal arteriovenous passage time (AVP) and peripapillary arterial and venous diameters were measured in digital scanning laser fluorescein angiograms. For estimation of retinal capillary density the area of the foveal avascular zone (FAZ) and the perifoveal intercapillary area (PIA) was quantified. 36 patients with NPG (mean age 57 (SD 13) years) and 21 healthy subjects (mean age 51 (13) years) were enrolled in the comparative study. Results: In NPG patients the AVP (2.55 (1.1) seconds) was significantly prolonged (p<0.001) when compared with healthy subject data (AVP: 1.70 (0.39) seconds). No differences for arterial or venous diameter, FAZ, and PIA were observed in NPG patients compared with healthy subjects. FAZ, PIA, arterial and venous diameter were not correlated with visual field indices (except venous diameter with PSD, r=0.35 (p<0.05)) or cup to disc ratios. AVP was significantly correlated (p<0.05) with the size of the optic nerve head (r=−0.28), visual field indices (MD: r=−0.3; PSD: r=0.3; CPSD: r=0.3), and contrast sensitivity (r=−0.34}. Conclusion: AVP times are significantly prolonged in NPG. The slowing of the retinal transit does not result from capillary dropout, or changes of peripapillary arterial or venous diameters with increased vascular resistance.