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Purpose. Pars plana vitrectomy (PPV) has been reported to reduce macular thickness and improve visual acuity in patients with diabetic macular edema (ME). The hypothesis for the study was that after PPV, clearance is accelerated and VEGF concentrations are reduced. To test this hypothesis, hVEGF(165) injections were performed in rabbit eyes, with and without PPV, and vitreous VEGF levels were measured as a function of time. Methods. The PPV group rabbits had a bilateral 25-gauge PPV, and in the no-PPV group, rabbits had intact vitreous. Intravitreal injections of hVEGF(165) were performed, and the animals were euthanatized at time points up to 7 days. The vitreous was isolated and an enzyme-linked immunosorbent assay was used to measure the VEGF levels. Pharmacokinetic parameters were determined in a noncompartmental analysis approach. Results. Mean vitreous VEGF levels decreased more rapidly in eyes subjected to PPV than in no-PPV eyes. The vitreous VEGF half-life (t([)(1/2)(])) in PPV eyes was 10 times shorter than that in normal eyes. In addition, mean clearance and mean area under the curve (AUC) increased and decreased, respectively, in eyes that underwent PPV. Conclusions. VEGF clearance is increased after PPV. Reducing VEGF concentrations in the vitreous post-PPV may partially explain the improvement in macular thickness in some patients with ME. Unexpectedly, the half-life of VEGF in the vitreous, even in no-PPV eyes, was <3 hours, whereas compounds of similar molecular weight typically have longer vitreous half-lives. The back of the eye may be uniquely adapted with rapid-clearance mechanisms to regulate vitreous VEGF levels. Further study is suggested.

Abstract.A functional Fourier domain optical coherence tomography instrument offering spectral Doppler imaging of in vivo pulsatile human retinal blood flow was constructed. An improved phase-resolved algorithm was developed to correct bulk motion artifacts. Spectral Doppler imaging provides complementary temporal flow information to the spatially distributed flow information of the color Doppler image by providing direct visualization of the Doppler spectrum of the flow whose pattern can be further quantified with various velocity envelope curves and their corresponding flow indices. The coefficient of repeatability on resistance index measurement was assessed by analyzing 14 measurements on two vessels within two normal subjects. Previous studies suggest that retinal haemodynamics play an important role in glaucoma, 1 diabetic retinopathy, 2 and age-related macular degeneration.3 Therefore, it is desirable to assess retinal blood flow in vivo in order to investigate their role in major eye diseases. Although many flow measurement technologies have been developed, they do not provide adequate information for understanding the relationship between retinal blood flow and important ocular diseases.4 Doppler optical coherence tomography 5-11 ͑DOCT͒, a variation of optical coherence tomography ͑OCT͒ that combines coherence gating and laser Doppler effects, is an alternative that can overcome some limitations of the technologies mentioned above. 4 Because of the unknown Doppler angle between the blood flow and incident light beam and the absence of a quantification method that can generate interpretable results for clinicians, DOCT is not widely used in eye clinics. Conventional DOCT only generates a snapshot of pulsatile ocular blood flow that is projected along the light beam direction in a cardiac cycle. Most recent developments in quantifying blood flow information of the human eye utilizes 3-D vascular orientation information to estimate Doppler angle and the absolute flow velocity. 10,11 On the other hand, it is noteworthy to quantify the pulsatile flow pattern as an alternative method to investigate retinal flow dynamics. A simple projected ocular blood flow velocity ͑integration over the whole blood vessel͒ plot through a cardiac cycle was chosen by White 9 to demonstrate the pulsatile flow property, although it is possible to acquire much more hemodynamics information from the same raw data. The M-mode scanning method has been used to acquire temporal flow information in time-domain DOCT systems.12,13 The short-time fast Fourier transformation method from Doppler ultrasound 14 was used to generate Doppler spectrum wave forms 13 but without further quantification, which provides the most valuable information for clinicians. The purpose of this paper is to implement the full concept of spectral Doppler imaging, developed by scientists and clinicians in ultrasound medicine, in a Fourier-domain DOCT system and provide an alternative quantification method for an ocular blood flow pattern that may be further inves...

Introduction We compared peripapillary retinal nerve fiber layer and macular thickness measurements in patients with mild cognitive impairment (MCI) and control subjects using swept‐source optical coherence tomography (SS‐OCT). We also assessed the relationship between SS‐OCT measurements and the severity of cognitive impairment. Methods Peripapillary retinal nerve fiber layer and macular thickness were measured in 23 patients and 24 control subjects using SS‐OCT. Cognitive status was assessed using the Mini‐Mental State Examination, the Montreal Cognitive Assessment, and the Pfeffer Questionnaire. Results Most inner retinal layer thickness parameters were significantly smaller in patients with MCI, especially macular ganglion cell complex thickness measurements. Mini‐Mental State Examination and Montreal Cognitive Assessment findings were significantly correlated with most macular thickness parameters. Discussion The SS‐OCT–measured inner retinal layers of patients with MCI displayed thinning, especially in the central macular area. SS‐OCT technology can provide useful information on ocular involvement patterns and holds promise as an ocular biomarker in this patient population.

PurposeThe aims of this study are to compare optical coherence tomography (OCT)-measured macular retinal layers in eyes with permanent temporal hemianopia from chiasmal compression and control eyes; to compare regular and slow-flash multifocal electroretinography (mfERG) in patients and controls; and to assess the correlation between OCT, mfERG, and central visual field (SAP) data.MethodsForty-three eyes of 30 patients with permanent temporal hemianopia due to pituitary tumors who were previously submitted to chiasm decompression and 37 healthy eyes of 19 controls were submitted to macular spectral domain OCT, mfERG, and 10-2 SAP testing. After segmentation, the thickness of the macular retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer, and photoreceptor layer (PRL) was measured. Amplitudes and oscillatory potentials (OPs) were measured on regular and slow-flash mfERG, respectively, and expressed as the mean values per quadrant and hemifield.ResultsRNFL, GCL, and IPL thickness measurements were significantly reduced in all quadrants, whereas INL, OPL, and PRL thicknesses were significantly increased in the nasal quadrants in patients compared to those in controls. Significant correlations between OCT and 10-2 SAP measurements were positive for the RNFL, GCL, and IPL and negative for the INL, OPL, and PRL. OPs and mfERG N1 amplitudes were significantly reduced in the nasal hemiretina of patients. Significant correlations were found between OP and mfERG amplitudes for inner and outer nasal hemiretina OCT measurements, respectively.ConclusionPatients with permanent temporal hemianopia from previously treated chiasmal compression demonstrated significant thinning of the RNFL, GCL, IPL, and thickening of the INL, OPL, and PRL associated with reduced OP and mfERG N1 amplitudes, suggesting that axonal injury to the inner retina leads to secondary damage to the outer retina in this condition.