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Biomedical subjects

C H Meyer

Publications and source records attributed to C H Meyer.

At least 37 records · Page 2Linked to original sources
PubMed2004

[Massive subretinal hemorrhages. A challenge for vitreous body surgeons].

BACKGROUND: In patients with advanced age-related macular degeneration (AMD), massive subretinal hemorrhage may sometimes be the reason for a loss of peripheral vision, leading to a significantly reduced quality of life. PATIENTS AND METHODS: During the years 1995-2001 we operated five eyes (five consecutive patients) with acute massive subretinal hemorrhage extending into all four quadrants and profoundly reduced vision in the fellow eye due to a Junius-Kuhnt macular scar. Within an interval of 1-2 weeks after the bleeding, pars plana vitrectomy with peripheral retinotomy was performed. After the retina was turned upside down and the partially liquified blood was removed, the underlying subfoveal CNV membrane was removed with a vitrectome. Three phakic eyes required additional cataract surgery and IOL implantation. The retina reattached under PFCL and a silicone oil tamponade applied for 3-6 months. RESULTS: The removal of the subretinal hemorrhage was without complications. The size of the subretinal membrane was between 4 and 6 PD with partially fibrovascular tissue. After the membrane was removed, a large central pigment epithelium defect made a macular rotation impossible. Visual acuity of hand motion improved from preoperatively 0.05 to postoperatively 1/35 to 0.1 after a follow-up of 3-6 months. CONCLUSION: In patients with such an extremely reduced visual acuity and visual field, subretinal surgery with removal of the subretinal blood may achieve sufficient vision for the patients' orientation.

Aged↗
PubMed2001

Efficient off-resonance correction for spiral imaging.

A new spiral imaging technique incorporates the acquisition of a field map into imaging interleaves. Variable density spiral trajectories are designed to oversample the central region of k-space, and interleaves are acquired at two different echo times. A field map is extracted from this data and multifrequency reconstruction is used to form an off-resonance corrected image using the entire dataset. Simulation, phantom, and in vivo results indicate that this technique can be used to achieve higher image and/or field map spatial resolution compared to conventional techniques. Magn Reson Med 45:521-524, 2001.

Artifacts↗
PubMed2001

Real-time interactive coronary MRA.

An interactive real-time imaging system capable of rapid coronary artery imaging is described. High-resolution spiral and circular echo planar trajectories were used to achieve 0.8 x 1.6 mm2 resolution in 135 ms (CEPI) or 1.13 x 1.13 mm2 resolution in 189 ms (spirals), over a 20-cm FOV. Using a sliding window reconstruction, display rates of up to 37 images/sec were achieved. Initial results indicate this technique can perform as a high-quality 2D coronary localizer and with SNR improvement may enable rapid screening of the coronary tree.

CD-I↗
PubMed2001

Retinal pigment epithelial tear with vitreomacular attachment: a novel pathogenic feature.

BACKGROUND: The development of tears of the retinal pigment epithelium (RPE) has classically been described with or without choroidal neovascularization (CNV) or after laser treatment. Tangential shear forces within the RPE or CNV are usually considered to cause the dehiscence. METHODS: Three patients with CNV and spontaneous RPE tear and additional vitreomacular traction were examined by fluorescein angiography (FA), optical coherence tomography (OCT) and kinetic ultrasound. RESULTS: From the pre-tear to the tear stage a sudden decrease in vision was observed. Fluorescein angiographic images demonstrated RPE-tear formation with blocked filling in the area of the contracted RPE and a well-demarcated hyperfluorescence in the bed of the torn RPE. OCT-scans demonstrated vitreomacular traction at the foveal area in all three cases. Kinetic ultrasound revealed vitreous attachments at the optic disc and fovea. CONCLUSION: Magnitude, variation of mechanical forces, and the continuous shear stress of the aged vitreous gel transmitted across vitreoretinal attachments may cause a chronic stimulus to retina and RPE. Vitreomacular traction may contribute to the subsequent formation of RPE tears via mechanical or cell mediator pathways.

Aged↗
PubMed2001

Macular translocation with radial scleral ouffolding: experimental studies and initial human results.

PURPOSE: Different techniques have been proposed for translocating the macula in patients with subfoveal neovascularization secondary to age-related macular degeneration. A new approach utilizing radial outfolding of the sclera was investigated. MATERIALS AND METHODS: Surgical techniques and retinal displacement were evaluated in animal trials using metal scleral clips. Successful translocation and reattachment of the retina was achieved in eight rabbits (eight eyes). We conducted a retrospective review of macular translocation surgery, performed with radial scleral outfolding, in a series of five consecutive human patients (five eyes) using full-thickness transscleral mattress sutures. RESULTS: After surgery, vision improved in two of five patients, with one patient achieving a visual acuity of 20/50. The mean angle of rotation was 11.5 deg (range 8.6 -15.1). The mean amount of foveal displacement was 1,276 pm (range 852-1,620). Complications included one case of retinal detachment, one of diplopia, and one of subretinal hemorrhage. CONCLUSIONS: Limited macular translocation by radial scleral outfolding can improve vision in selected patients. Radial evagination appears to be as effective as circumferential infolding.

Aged↗
PubMed2001

Induced corneal astigmatism after macular translocation surgery with scleral infolding.

OBJECTIVE: To document the corneal astigmatism that occurs with macular translocation after scleral infolding surgery. DESIGN: Retrospective case series of a nonrandomized clinical trial. PARTICIPANTS: Eight consecutive age-related macular degeneration patients (eight eyes) with choroidal neovascularization who underwent macular translocation with scleral infolding at the Duke University Eye Center from December 1998 through October 1999. METHODS: We retrospectively reviewed the charts of eight consecutive patients who underwent macular translocation surgery involving scleral infolding in the superotemporal quadrant. Two patients subsequently underwent release of scleral infolding. MAIN OUTCOME MEASURES: After surgery, these eyes were evaluated for corneal astigmatism with manifest refraction, keratometry, and computerized corneal topography. RESULTS: All eight eyes of eight patients revealed marked degrees of corneal astigmatism. Measurement of astigmatism via manifest refraction, keratometry, and corneal topography confirmed postoperative astigmatism corresponding to the axis of the scleral infolding. The amount of corneal astigmatism ranged from 1.75 to 7.37 diopters (D; mean, 4.60 D), with steepening along the axis of scleral infolding in the superotemporal quadrant of each eye (mean, 42.50 degrees from vertical; range, 24 degrees -66 degrees from vertical). Release of scleral infolding in two patients resulted in significant reduction of corneal astigmatism. CONCLUSIONS: Scleral shortening procedures used in macular translocation surgery may induce large amounts of corneal astigmatism. These patients should be assessed with keratometry and corneal topography to determine the accurate amount and axis. Thereafter, contact lens fitting or scleral infolding release may be considered as therapeutic options for large amounts of astigmatism persisting after surgery.

Astigmatism↗
PubMed2001

Rapid evaluation of left ventricular volume and mass without breath-holding using real-time interactive cardiac magnetic resonance imaging system.

OBJECTIVES: The purpose of this study was to validate cardiac measurements derived from real-time cardiac magnetic resonance imaging (MRI) as compared with well-validated conventional cine MRI. BACKGROUND: Although cardiac MRI provides accurate assessment of left ventricular (LV) volume and mass, most techniques have been relatively slow and required electrocardiogram (ECG) gating over many heart beats. A newly developed real-time MRI system allows continuous real-time dynamic acquisition and display without cardiac gating or breath-holding. METHODS: Fourteen healthy volunteers and nine patients with heart failure underwent real-time and cine MRI in the standard short-axis orientation with a 1.5T MRI scanner. Nonbreath-holding cine MRI was performed with ECG gating and respiratory compensation. Left ventricular end-diastolic volume (LVEDV), left ventricular endsystolic volume (LVESV), ejection fraction (EF) and LV mass calculated from the images obtained by real-time MRI were compared to those obtained by cine MRI. RESULTS: The total study time including localization for real-time MRI was significantly shorter than cine MRI (8.6 +/- 2.3 vs. 24.7 +/- 3.5 min, p < 0.001). Both imaging techniques yielded good quality images allowing cardiac measurements. The measurements of LVEDV, LVESV, EF and LV mass obtained with real-time MRI showed close correlation with those obtained with cine MRI (LVEDV: r = 0.985, p < 0.001; LVESV: r = 0.994, p < 0.001; EF: r = 0.975, p < 0.001; LV mass: r = 0.977, p < 0.001). CONCLUSIONS: Real-time MRI provides accurate measurements of LV volume and mass in a time-efficient manner with respect to image acquisition.

Adult↗
PubMed2001

Successful macular translocation with temporary scleral infolding using absorbable sture.

PURPOSE: To describe successful macular translocation with temporary scleral infolding in a series of patients with small subfoveal choroidal neovascularization due to age-related macular degeneration or ocular histoplasmosis syndrome. METHODS: Ten eyes of 10 consecutive patients were studied in a prospective, nonrandomized clinical trial. Macular translocation with scleral infolding (MTSI) was performed. Absorbable polyglactin suture was used to create temporary scleral infolding. Distance and stability of retinal translocation, corneal topography, visual acuity, and rates of complications were measured. RESULTS: The median distance of translocation in the early postoperative period was 1,700 microm (range, 680-3,200) and did not regress after resolution of the scleral infolding. Induced postoperative oblique corneal astigmatism resolved, coinciding with the disappearance of peripheral retinal elevation due to scleral infolding. Three patients gained more than two lines of vision, two patients were within two lines of preoperative vision, and five patients lost more than two lines of vision. Complications were similar to previously published reports. CONCLUSION: Temporary scleral infolding is an effective technique in MTSI. The distance of translocation is comparable to that achieved with nonabsorbable suture or scleral resection, and does not regress after resolution of the scleral infolding. Induced postoperative corneal astigmatism appears to resolve.

Aged↗
PubMed2001

Outcome of selective peripheral denervation for cervical dystonia.

30 patients with cervical dystonia were treated by selective peripheral denervation (SPD) (Bertrand procedures). Follow-up 12-75 (median 26) months after surgery showed strong group improvements in the clinical state (Toronto Western Spasmodic Torticollis Rating Scale) and in performance of ADL, impairment, lifestyle and degree of incapacity (rating scales used by Australia's Department of Veterans' Affairs). SPD can give long-term benefits important clinically, in the home and in society.

Activities of Daily Living↗
PubMed2000

Combined connectivity and a gray-level morphological filter in magnetic resonance coronary angiography.

A connectivity algorithm combined with a new gray-level morphological filter dramatically improves the segmentation of tortuous coronary arteries from 3D MRI. Small coronary arteries are segmented from the larger ventricles with a new filter. These blood vessels are segmented from the noise background with connectivity. Coronary angiograms were computed in nine datasets acquired on volunteers with 3D stack of spirals and contrast-enhanced navigator sequences by both a maximum intensity projection and surface rendering. Surface images provided depth information needed to distinguish branching arteries from crossing veins. Magn Reson Med 43:892-895, 2000.

Algorithms↗