Katrina P. Winter

Validated Automatic Segmentation of AMD Pathology Including Drusen and Geographic Atrophy in SD-OCT Images

PURPOSE To automatically segment retinal spectral domain optical coherence tomography (SD-OCT) images of eyes with age-related macular degeneration (AMD) and various levels of image quality to advance the study of retinal pigment epithelium (RPE)+drusen complex (RPEDC) volume changes indicative of AMD progression. METHODS A general segmentation framework based on graph theory and dynamic programming was used to segment three retinal boundaries in SD-OCT images of eyes with drusen and geographic atrophy (GA). A validation study for eyes with nonneovascular AMD was conducted, forming subgroups based on scan quality and presence of GA. To test for accuracy, the layer thickness results from two certified graders were compared against automatic segmentation results for 220 B-scans across 20 patients. For reproducibility, automatic layer volumes were compared that were generated from 0° versus 90° scans in five volumes with drusen. RESULTS The mean differences in the measured thicknesses of the total retina and RPEDC layers were 4.2 ± 2.8 and 3.2 ± 2.6 μm for automatic versus manual segmentation. When the 0° and 90° datasets were compared, the mean differences in the calculated total retina and RPEDC volumes were 0.28% ± 0.28% and 1.60% ± 1.57%, respectively. The average segmentation time per image was 1.7 seconds automatically versus 3.5 minutes manually. CONCLUSIONS The automatic algorithm accurately and reproducibly segmented three retinal boundaries in images containing drusen and GA. This automatic approach can reduce time and labor costs and yield objective measurements that potentially reveal quantitative RPE changes in longitudinal clinical AMD studies. (ClinicalTrials.gov number, NCT00734487.).

Dynamics of Human Foveal Development after Premature Birth

PURPOSE To determine the dynamic morphologic development of the human fovea in vivo using portable spectral domain-optical coherence tomography (SD-OCT). DESIGN Prospective, observational case series. PARTICIPANTS Thirty-one prematurely born neonates, 9 children, and 9 adults. METHODS Sixty-two neonates were enrolled in this study. After examination for retinopathy of prematurity (ROP), SD-OCT imaging was performed at the bedside in nonsedated infants aged 31 to 41 weeks postmenstrual age (PMA) (= gestational age in weeks + chronologic age) and at outpatient follow-up ophthalmic examinations. Thirty-one neonates met eligibility criteria. Nine children and nine adults without ocular pathology served as control groups. Semiautomatic retinal layer segmentation was performed. Central foveal thickness, foveal to parafoveal (FP) ratio (central foveal thickness divided by thickness 1000 μm from the foveal center), and 3-dimensional thickness maps were analyzed. MAIN OUTCOME MEASURES In vivo determination of foveal morphology, layer segmentation, analysis of subcellular changes, and spatiotemporal layer shifting. RESULTS In contrast with the adult fovea, several signs of immaturity were observed in the neonates: a shallow foveal pit, persistence of inner retinal layers (IRLs), and a thin photoreceptor layer (PRL) that was thinnest at the foveal center. Three-dimensional mapping showed displacement of retinal layers out of the foveal center as the fovea matured and the progressive formation of the inner/outer segment band in the opposite direction. The FP-IRL ratios decreased as IRL migrated before term and minimally after that, whereas FP-PRL ratios increased as PRL subcellular elements formed closer to term and into childhood. A surprising finding was the presence of cystoid macular edema in 58% of premature neonates that appeared to affect inner foveal maturation. CONCLUSIONS This study provides the first view into the development of living cellular layers of the human retina and of subcellular specialization at the fovea in premature infant eyes using portable SD-OCT. Our work establishes a framework of the timeline of human foveal development, allowing us to identify unexpected retinal abnormalities that may provide new keys to disease activity and a method for mapping foveal structures from infancy to adulthood that may be integral in future studies of vision and visual cortex development. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.

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.

Spatial correlation between hyperpigmentary changes on color fundus photography and hyperreflective foci on SDOCT in intermediate AMD.

PURPOSE Macular hyperpigmentation is associated with progression from intermediate to advanced age-related macular degeneration (AMD). The purpose of this study was to accurately correlate hyperpigmentary changes with spectral domain optical coherence tomography (SDOCT) hyperreflective foci in eyes with non-advanced AMD. METHODS A prospective cross-sectional analysis of 314 eyes (314 subjects) with intermediate AMD was performed in the multicenter Age-Related Eye Disease Study 2 (AREDS2) Ancillary SDOCT Study to correlate hyperpigmentary changes on color fundus photographs (CFP) with abnormal morphology on SDOCT. Spatial coregistration was performed with an automated algorithm in two nonoverlapping subsets of 20 study eyes, which permitted double-masked CFP and SDOCT grading by certified investigators. RESULTS Macular CFP hyperpigmentation was significantly associated with SDOCT intraretinal hyperreflective foci in the 314 study eyes (P < 0.001). In a substudy of 40 eyes, automated intermodality spatial coregistration was successfully achieved in all 136 (100%) retinal regions selected for CFP and SDOCT grading. In one subset of 20 study eyes, 28 of 39 (71.8%) retinal CFP regions with hyperpigmentation were correlated with focal hyperreflectivity on SDOCT, versus seven of 39 (17.9%) control regions (P < 0.001). In another subset of 20 eyes, 21 of 29 (72.4%) SDOCT regions with hyperreflective foci were correlated with hyperpigmentary changes on CFP, versus two of 29 (6.9%) control regions (P < 0.001). CONCLUSIONS A novel algorithm achieves automated intermodality spatial coregistration for masked grading of regions selected on CFP and SDOCT. In intermediate AMD, macular hyperpigmentation has high spatial correlation to SDOCT hyperreflective foci and often represents the same anatomical lesion. (ClinicalTrials.gov number, NCT00734487.).

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.

Windows of opportunity: applying ultrashort laser pulses for selective tissue effects

Ultrashort pulsed laser retinal effects vary widely depending on the configuration of the laser energy as it reaches the retina and surrounding structures. Tissue response is determined by: wavelength, pulsewidth, energy per pulse, peak irradiance, linear optics of the beam path, and non linear optics of the ultrashort beam. In vivo, we have reported a range of lesions from visible and from near infrared ultrashort laser pulses. New data from additional infrared studies in vivo is combined with our previous data to present an overview of retinal effects and how these might be selected for retinal surgical use.