Multifocal electroretinogram in birdshot chorioretinopathy.

PURPOSE: To characterize multifocal electroretinogram parameters in patients with birdshot chorioretinopathy. METHODS: Twenty-eight patients with birdshot chorioretinopathy consecutively included from 2006 to 2011 were matched to 27 healthy subjects for age, axial length, and lens status. Multifocal electroretinogram was prospectively evaluated using the Vision Monitor system. RESULTS: Birdshot chorioretinopathy eyes differed significantly from healthy eyes by a decrease in mean root mean square values (-24.7%), P1 (-17.3%) and N2 (-27.5%) amplitude, and the P1/N1 ratio (-26.3%) as well as an increase in N1 (8.7%) and P1 (5.4%) implicit time (IT). An effect of the degree of eccentricity (5 zones) was found for root mean square (P < 0.001), P1 (P < 0.001) and N2 (P < 0.001) amplitude, and P1 IT (P < 0.001). Root mean square, the P1/N1 ratio, P1 and N2 amplitudes, P1 and N1 ITs were significantly correlated with visual acuity, mean defect of visual field, foveal threshold, and color vision score. The fluorescein angiographic score was significantly correlated to N1 and N2 amplitudes and N1 IT. CONCLUSION: Amplitudes and ITs of the multifocal electroretinogram parameters are impaired in patients with birdshot chorioretinopathy and are well correlated with other anatomical and functional tests. Periodic testing could guide the immunosuppressive treatment.

Twenty-four-hour rhythm of ocular perfusion pressure in non-arteritic anterior ischaemic optic neuropathy.

PURPOSE: In non-arteritic anterior ischaemic optic neuropathy (NAAION) patients, circulatory insufficiency within the optic nerve has previously been hypothesized to be related to nocturnal systemic hypotension. The main objective of this prospective cohort study was to investigate the nyctohemeral variations in ocular perfusion pressure (OPP) in NAAION patients. METHODS: In 20 patients with NAAION, the intraocular pressure (IOP) was measured using the Tono-Pen XL(™) electronic tonometer every hour for 24 hr. Blood pressure (BP) was evaluated over 24 hr. Mean OPP was calculated with the following formula: OPP sitting position = (0.74 × mean BP) - IOP and OPP lying position = (0.84 × mean BP) - IOP. A nonlinear least squares dual-harmonic regression analysis approach was used to model the 24-hr rhythms of OPP data. RESULTS: On average, a 24-hr amplitude of 4.7 ± 2.6 mmHg was found for OPP. The patients were classified as either having a diurnal OPP rhythm (i.e. with a diurnal acrophase, 10% of the cases), a nocturnal OPP rhythm (45%) or absence of OPP rhythm (45%). Four patients had a nocturnal reduction in OPP (mean, -11%). CONCLUSION: The physiological nocturnal rhythm of OPP was maintained in 45% of the NAAION patients. The nocturnal reduction in OPP seen in 20% of the patients was within the range of OPP where optic nerve blood flow autoregulation is still fully operative. A high prevalence of obstructive sleep apnoea syndrome in our population (71%) may explain the low frequency of systemic nocturnal hypotension.

Continuous response of optic nerve head blood flow to increase of arterial blood pressure in humans.

PURPOSE: This study investigates the effect of increased ocular perfusion pressure (OPP) on optic nerve head (ONH) hemodynamics. METHODS: In 21 healthy subjects, the increase in arterial blood pressure (BP), measured continuously using a pneumatic transcutaneous sensor, was produced by isometric exercise consisting of 2 minutes of hand-gripping. ONH blood flow parameters-namely the velocity (Vel), number (Vol), and flux (F) of red blood cells-were measured using the laser Doppler flowmeter (LDF). RESULTS: In those 14 healthy subjects who exhibited a similar increase in BP to handgrip superior to 30% of baseline BP, group average increases of BP and OPP amounted to 34% ± 3% (SEM) and 43% ± 3%, respectively. The increase in F of 19% ± 8%, resulting from an increase in Vel (17% ± 7%) and Vol (6% ± 7%), was significantly less than predicted for a passive autoregulatory response, as revealed also by the increase in vascular resistance (R = OPP/F). Spearman test of linear correlations between F and time during handgrip led to the identification of one group of eight subjects (with a stable F) and one group of six subjects (with an increase in F). A closed-loop gain (G) of the regulatory process, defined as G = 1 - {(F - Fbl)/Fbl}/{(OPP - OPPbl)/OPPbl}, was found to be rather independent from the OPP, with an average value 0.7 ± 0.07. G was 0.83 ± 0.06 for the group of eight subjects with stable F and 0.3 ± 0.15 for the group of six subjects with F increasing with the OPP. CONCLUSIONS: The continuous recording of both BP and LDFs represents a novel and more precise approach to the characterization of ONH hemodynamics during isometric exercise, especially useful in the future for patients with ocular diseases. The efficiency of the ONH blood flow autoregulation appears to vary significantly between healthy subjects. (ClinicalTrials.gov number, NCT00874913.).