In vitro simulation of the first technique for non-invasive measurement of volumetric ophthalmic artery blood flow in humans.

BACKGROUND AND OBJECTIVE: To evaluate the accuracy, reproducibility, and variability of volumetric flow measurements taken by color Doppler imaging ultrasound, using an in vitro "phantom" model to simulate the ophthalmic artery. MATERIALS AND METHODS: An agar flow phantom with two wall-less lumens was constructed to simulate the ophthalmic artery. Velocity and volumetric flow measurements were taken for various flow rates and ultrasound probe positions. The measurements were analyzed for accuracy, reproducibility, and variability. RESULTS: Velocity measurements were more accurate than flow measurements (8 of 24 vs 3 of 24 accurate trials). The average coefficient of variation for volumetric blood flow was 11.4% (n = 120). Volumetric flow significantly correlated with velocity (R(2) = 0.408, n = 600, P < .001). The highest correlation was achieved using the large lumen with the probe held at 75 degrees , offset to the flow (R(2) = 0.862, n = 75). CONCLUSION: Based on an in vitro model, non-invasive color Doppler imaging recordings of volumetric flow measurements in the ophthalmic artery significantly correlated with velocity and higher correlations were found using the larger lumens, although the data showed a lack of high accuracy in measurements of flow and velocity.

Diagnostic ability of Fourier-domain vs time-domain optical coherence tomography for glaucoma detection.

PURPOSE: To compare retinal nerve fiber layer (RNFL) thickness assessments and the discriminating ability of Fourier-domain optical coherence tomography (FD-OCT) with that of time-domain optical coherence tomography (TD-OCT) for glaucoma detection. DESIGN: Prospective, nonrandomized, observational cohort study. METHODS: Normal and glaucomatous eyes underwent complete examination, standard automated perimetry, optic disc photography, TD-OCT (Stratus OCT; Carl Zeiss Meditec, Dublin, California, USA), and FD-OCT (RTVue; Optovue Inc, Fremont, California, USA). One eye per subject was enrolled. Two consecutive scans were acquired using a 3.46-mm diameter scan with TD-OCT and a 3.45-mm diameter scan with FD-OCT. For each of 5 RNFL parameters, the area under the receiver operator characteristic curve was calculated to compare the ability of FD-OCT and TD-OCT to discriminate between normal and glaucomatous eyes. RESULTS: Fifty healthy persons (mean age, 65.3 +/- 9.9 years) and 50 glaucoma patients (mean age, 67.7 +/- 10.5 years) were enrolled. Average, superior, and inferior RNFL thickness measurements (in micrometers) were significantly (P < .01) greater with FD-OCT compared with TD-OCT in normal eyes (103.3 +/- 12.6 vs 96.3 +/- 10.7, 134.5 +/- 18.6 vs 113.9 +/- 16.3, and 129.7 +/- 16.9 vs 125.5 +/- 15.8, respectively) and glaucomatous eyes (P < .001; 77.6 +/- 17.6 vs 70.4 +/- 18.6, 108.0 +/- 26.8 vs 86.8 +/- 30.2, 82.2 +/- 3.3 vs 73.5 +/- 26.1, respectively). The area under the receiver operator characteristic curves for RNFL thickness were similar (P > .05) using FD-OCT (average, 0.88; superior, 0.80; inferior, 0.94) and TD-OCT (average, 0.87; superior, 0.79; inferior, 0.95). CONCLUSIONS: Cross-sectional peripapillary RNFL thickness measurements obtained using FD-OCT generated with the RTVue are greater than those obtained with TD-OCT and have similar diagnostic performance for glaucoma detection.

Ocular toxoplasmosis presenting with focal retinal nerve fiber atrophy simulating glaucoma.

PURPOSE: We describe a patient with ocular hypertension and nonglaucomatous retinal nerve fiber layer (RNFL) atrophy associated with an ocular toxoplasmosis retinal lesion. PATIENT AND METHOD: Single case report. RESULTS: An RNFL defect was identified adjacent to a circumscribed pigmented chorioretinal lesion superior to the macular region. The optic disc showed a prominent central cup without focal neural rim atrophy. Red-free photography and RNFL imaging using optical coherence tomography and scanning laser polarimetry showed corresponding focal RNFL atrophy. The toxoplasmosis lesion was characterized by an apparent full thickness disruption in retinal architecture, including the retinal ganglion cell layer, using spectral-domain optical coherence tomography. CONCLUSIONS: Nonglaucomatous retinal lesions may simulate glaucomatous RNFL atrophy and visual field loss, particularly when focal damage to the retinal ganglion cells occurs. Careful inspection of the retina and optic disc, with attention to the integrity of the neural rim, and analysis of the pattern of RNFL loss in proximity to a retinal lesion may enable the clinician to differentiate glaucomatous and nonglaucomatous pathogenic mechanisms.

Migration of glaucoma drainage device extender into anterior chamber after trauma.

PURPOSE: Glaucoma drainage devices, on rare occasions, need repositioned and the intraocular portion of the implant tube is found to be "too short" to do so. Previously, a technique was described for "extending" the tube with angiocatheter material (rather than replacing the entire apparatus), and had been performed successfully without complication for 7 years. This case describes the first known complication: trauma causing anterior chamber migration of the tube extension requiring retrieval and reconstruction of the tube extension apparatus. PATIENT AND METHODS: One eye of 1 patient (age 8) with a prior glaucoma drainage device and tube extension with angiocatheter material with elevated intraocular pressure after direct trauma to the eye from a pencil. Office examination revealed inferior corneal edema and no tube segment visible in the anterior chamber on limited examination due to age-related compliance. Gonioscopy under anesthesia revealed the tube extender in the inferior anterior chamber. The tube extender was retrieved from the anterior chamber. The glaucoma drainage device was surgically exposed and the tube extension was reconstructed, including securing the tube extension with a suture placed through the lumens of both the angiocatheter extender and the tube extension. RESULTS: The reconstructed tube extension maintained good draining function with the secured extension and no further migration of the tube extension into the anterior chamber was seen. CONCLUSIONS: Tube extension using angiocatheter material continues to be a viable, cost-effective option in difficult cases. Placing a securing suture in patients prone to eye trauma can be considered.

Reduced cerebrovascular blood flow velocities and vasoreactivity in open-angle glaucoma.

PURPOSE: To compare cerebral blood flow velocities between open-angle glaucoma (OAG) patients and controls, at baseline and during hyperoxia. DESIGN: Observational cohort study. METHODS: A prospective study was conducted in a single institution. Sixteen OAG patients and 15 normal subjects, matched for age, were enrolled. Patients and controls were studied at baseline, while breathing room air, and during 100% oxygen breathing. The eye with the more severe visual field defect was chosen in glaucoma patients, while in controls, the study eye was chosen randomly. Subjects with history of diabetes, cardiovascular, or respiratory disease were excluded. Measurements included brachial arterial pressure, heart rate, intraocular pressure and transcranial Doppler (TCD). Mean and peak velocity and pulsatility index of the ipsilateral middle cerebral artery (MCA) were measured by TCD. RESULTS: At baseline, MCA mean and peak systolic blood flow velocities were significantly lower in glaucoma patients compared with controls velocities were significantly lower in glaucoma patients compared with controls (mean velocity: 50.2 vs 65.3 cm/s, P <.05; peak velocity: 74.2 vs 96.8 cm/s, P <.05). Additionally, while hyperoxia significantly decreased both mean and peak systolic velocities in MCA of controls (mean velocity: 65.3 vs 57.7 cm/s, P <.05; peak velocity 96.8 vs 87.9 cm/s, P <.05), it did not cause any significant change in OAG patients. CONCLUSIONS: Glaucoma patients were found to have lower MCA blood flow velocities and an absence of vasoreactivity to hyperoxia, compared with controls. The relationship of these cerebral hemodynamic abnormalities to glaucoma pathogenesis and progression remains to be explored.