Michelle McCall

Spectral-Domain Optical Coherence Tomography Characteristics of Intermediate Age-related Macular Degeneration

PURPOSE Describe qualitative spectral-domain optical coherence tomography (SD-OCT) characteristics of eyes classified as intermediate age-related macular degeneration (nonadvanced AMD) from Age-Related Eye Disease Study 2 (AREDS2) color fundus photography (CFP) grading. DESIGN Prospective cross-sectional study. PARTICIPANTS We included 345 AREDS2 participants from 4 study centers and 122 control participants who lack CFP features of intermediate AMD. METHODS Both eyes were imaged with SD-OCT and CFP. The SD-OCT macular volume scans were graded for the presence of 5 retinal, 5 subretinal, and 4 drusen characteristics. In all, 314 AREDS2 participants with ≥1 category-3 AMD eye and all controls each had 1 eye entered into SD-OCT analysis, with 63 eyes regraded to test reproducibility. MAIN OUTCOME MEASURES We assessed SD-OCT characteristics at baseline. RESULTS In 98% of AMD eyes, SD-OCT grading of all characteristics was successful, detecting drusen in 99.7%, retinal pigment epithelium (RPE) atrophy/absence in 22.9%, subfoveal geographic atrophy in 2.5%, and fluid in or under the retina in 25.5%. Twenty-eight percent of AMD eyes had characteristics of possible advanced AMD on SD-OCT. Two percent of control eyes had drusen on SD-OCT. Vision loss was not correlated with foveal drusen alone, but with foveal drusen that were associated with other foveal pathology and with overlying focal hyperreflectivity. Focal hyperreflectivity over drusen, drusen cores, and hyper- or hyporeflectivity of drusen were also associated with RPE atrophy. CONCLUSIONS Macular pathologies in AMD can be qualitatively and reproducibly evaluated with SD-OCT, identifying pathologic features that are associated with vision loss, RPE atrophy, and even possibly the presence of advanced AMD not apparent on CFP. Qualitative and detailed SD-OCT analysis can contribute to the anatomic characterization of AMD in clinical studies of vision loss and disease progression. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

Developing SDOCT to assess donor human eyes prior to tissue sectioning for research

BackgroundTo compare spectral domain optical coherence tomography (SDOCT) cross-sectional images of human central retina obtained from donor eyes with and without age-related macular degeneration (AMD) to corresponding histopathology from light micrographs. To establish the utility of SDOCT for localizing pathology in the posterior eyecup, for identifying ocular disease in donor eyes, or for directing subsequent sectioning of retinal lesions for research.MethodsSeven consecutive human donor eyes were selected based on age. The eyes, with the anterior segment removed, were imaged by SDOCT with a focusing aspheric lens. Four eyes were from donors with a clinical history of AMD, and three were from age-matched donors with no history of AMD. Histopathological correlation of morphological changes detected in three eyes by SDOCT was obtained for comparison to step serial-sectioned light microscopy images of the formalin-fixed, paraffin-embedded retina. A simplified imaging setup was tested on an enucleated porcine eye for comparison.ResultsAMD pathology was detected and localized in four eyes by SDOCT. The SDOCT images correlated with the histopathology observed by light microscopy in each sectioned eye. Pathologies included a subfoveal neovascular lesion with subretinal fluid, peripapillary neovascularization, epiretinal membrane, foveal cyst, choroidal folds, and drusen. Similar imaging was possible with the simplified setup.ConclusionsSDOCT imaging identified retinal disease of the posterior eyecup in human donor eyes. Pathology detected with SDOCT was verified by light microscopy in three eyes, supporting the utility of SDOCT as a screening tool for research.

Precision Targeting with a Tracking Adaptive Optics Scanning Laser Ophthalmoscope

Precise targeting of retinal structures including retinal pigment epithelial cells, feeder vessels, ganglion cells, photoreceptors, and other cells important for light transduction may enable earlier disease intervention with laser therapies and advanced methods for vision studies. A novel imaging system based upon scanning laser ophthalmoscopy (SLO) with adaptive optics (AO) and active image stabilization was designed, developed, and tested in humans and animals. An additional port allows delivery of aberration-corrected therapeutic/stimulus laser sources. The system design includes simultaneous presentation of non-AO, wide-field (~40 deg) and AO, high-magnification (1-2 deg) retinal scans easily positioned anywhere on the retina in a drag-and-drop manner. The AO optical design achieves an error of <0.45 waves (at 800 nm) over ±6 deg on the retina. A MEMS-based deformable mirror (Boston Micromachines Inc.) is used for wave-front correction. The third generation retinal tracking system achieves a bandwidth of greater than 1 kHz allowing acquisition of stabilized AO images with an accuracy of ~10 μm. Normal adult human volunteers and animals with previously-placed lesions (cynomolgus monkeys) were tested to optimize the tracking instrumentation and to characterize AO imaging performance. Ultrafast laser pulses were delivered to monkeys to characterize the ability to precisely place lesions and stimulus beams. Other advanced features such as real-time image averaging, automatic highresolution mosaic generation, and automatic blink detection and tracking re-lock were also tested. The system has the potential to become an important tool to clinicians and researchers for early detection and treatment of retinal diseases.

Using optical coherence tomography to elucidate the impact of fixation on retinal laser pathology

Purpose: The direct comparison of in-vivo OCT images with fixed tissues sections assumes the fixation of tissue has no effect on the size and configuration of final pathology images such as light micrographs. Fixation artifact has been a concern in numerous studies of the pathology of retinal laser lesions. We tested this hypothesis. Methods: The Humphrey OCT model 2000 with a custom mirror and lens assembly was used to scan tissue phantoms and both fresh and fixed ex-vivum tissue samples. The optical configuration was determined by optimization of the contrast and signal strength on tissue phantoms. Fresh porcine retinas were scanned using this optimal configuration, then fixed using either glutaraldehyde or formalin. OCT images were taken of the tissue at various stages during the fixation process. Additionally, we examined fixed retinal tissue containing retinal laser lesions as a part of our study of ultrashort-pulsed laser effects on the macacca mulatta retina. Histologic sections were prepared and evaluated. Results: In this presentation, we describe our optical setup and image optimization process and assess the effects of glutaraldehyde and formalin processing on OCT image quality. The OCT images of glutaraldehyde-fixed laser lesions are compared with similar images of laser lesions in-vivo. Fixation artifacts appeared on OCT at 2 to 24 hours. Opacification of the lumen of large vessels was seen at two hours with both glutaraldehyde and formalin, while fixation induced retinal detachment appeared at 24 hours. Overall, there was a grater delineation of the laser lesions by OCT at 24 hours when compared to at 1 or 2 hours of fixation. Conclusions: Fixations induced changes in OCT scans of retinal tissue are present as early as 2 hours after immersion in fixative. Although both glutaraldehyde and formalin fixation preserve much of the tissue structure, these method of fixation have s significant effect on OCT imaging of both normal retinal tissue and laser lesions.

Histopathology of ultrashort pulsed laser retinal damage: changing retinal pathology with variation in spot size for near-infrared laser lesions

We wish to identify the change in extent of retinal tissue injury due to varying the spot size at the retina of ultrashort laser pulses. We compared the effects of delivery of near infrared (1060 nm) single laser pulses to an 800 micron diameter retinal spot to previously reported laser retinal effects. We examined macular lesions 24 hours after delivery of near-infrared (1060 nm wavelength) ultrashort laser to 804 micron spot-size, using fundus examination, fundus photographs and fluorescein angiograms. Using light microscopy, we examined sections of these lesions obtained 24 hours after laser delivery. The degree of retinal damage was compared to our data published previously by using a modified version of our previous grading scale. The 150 fs near infrared, large spot laser lesions were remarkable in their clinical and pathological appearance. The lesions, rather than centering on a single focal spot of pallor as typically seen in pulsed laser lesions of the retina, demonstrated a spotted pattern of multiple focal lesions across the area of laser delivery. There was also choroidal damage in several eyes but the Bruchs membrane remained intact. Although there was choroidal damage in the 150 fs near infrared wavelength small spot laser lesions there was not significant thermal spread. The small spot ultrashort visible wavelength showed no significant thermal spread and no choroidal damage. Larger spot-size demonstrated a broader area of damage than that of the smaller spot-size and different choroidal effect when compared to smaller sized lesions.

In-vivo tissue response to the free-electron laser

Purpose: We analyzed the effect of energy and rate of cutting on the in vivo ocular response to 2.94 μm wavelength Free Electron Laser incision of the cornea. We were interested in the difference between our clinical observations of the initial laser lesion and the ocular response using the biomicroscope versus optical coherence tomographs. We were also interested in the difference between these clinical in vivo data and our findings from light micrographs of fixed tissue. Methods: Corneas were incised with FEL at 2.94 μm wavelength and either 2.5 or 3.5 mJ/1.4 μsec. the rate of movement of the laser beam across tissue ranged from 0.2 mm/sec to 1.2 mm/sec. Eyes were examined for two hours postoperatively using optical coherence tomography (OCT) and compared to the clinical slit lamp examination and to light microscopic examination of fixed tissue sections. Results: OCT revealed a dramatic fibrin response directly correlated to the slow sweep of the FEL beam across the tissue (longer duration of tissue exposure to the laser beam). The OCt was better than examination at the slit lamp at demonstrating sites of fibrin attachments.