Publications by authors named "Margaret R Strampe"

6 Publications

  • Page 1 of 1

Retinal Nerve Fibre Layer Thickness Increases with Decreasing Spectralis OCT Signal Strength in Normal Eyes.

Neuroophthalmology 2020 Apr 29;44(2):100-103. Epub 2019 Oct 29.

Department of Ophthalmology & Visual Neurosciences, University of Minnesota Medical School, Minneapolis, Minnesota, USA.

We sought to determine effect of signal strength on mean retinal nerve fibre layer (RNFL) using Spectralis optical coherence tomography (S-OCT). Thirty normal subjects (18 female, mean 37.9 years, range 24-61) were imaged with S-OCT using variably dense Bangerter foils to alter Q value (1 unit signal strength = 4 units Q). We found a statistically significant (p < 0.01) linear relationship (R = 0.8643) between Q and RNFL (1 unit decrease Q = 0.181 um mean RNFL increase). Unlike previous observations of Cirrus and Stratus OCT, we found RNFL thickness does not decrease with decreasing signal strength in S-OCT.
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http://dx.doi.org/10.1080/01658107.2019.1653934DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7202426PMC
April 2020

Assessing the Interocular Symmetry of Foveal Outer Nuclear Layer Thickness in Achromatopsia.

Transl Vis Sci Technol 2019 Sep 2;8(5):21. Epub 2019 Oct 2.

Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI, USA.

Purpose: We examine the interocular symmetry of foveal outer nuclear layer (ONL) thickness measurements in subjects with achromatopsia (ACHM).

Methods: Images from 76 subjects with - or -associated ACHM and 42 control subjects were included in the study. Line or volume scans through the fovea of each eye were acquired using optical coherence tomography (OCT). Image quality was assessed for each image included in the analysis using a previously-described maximum tissue contrast index (mTCI) metric. Three foveal ONL thickness measurements were made by a single observer and interocular symmetry was assessed using the average of the three measurements for each eye.

Results: Mean (± standard deviation) foveal ONL thickness for subjects with ACHM was 79.7 ± 18.3 μm (right eye) and 79.2 ± 18.7 μm (left eye) compared to 112.9 ± 15.2 (right eye) and 112.1 ± 13.9 μm (left eye) for controls. Foveal ONL thickness did not differ between eyes for ACHM ( = 0.636) or control subjects ( = 0.434). No significant relationship between mTCI and observer repeatability was observed for either control ( = 0.140) or ACHM ( = 0.351) images.

Conclusions: While foveal ONL thickness is reduced in ACHM compared to controls, the high interocular symmetry indicates that contralateral ONL measurements could be used as a negative control in early-phase monocular treatment trials.

Translational Relevance: Foveal ONL thickness can be measured using OCT images over a wide range of image quality. The interocular symmetry of foveal ONL thickness in ACHM and control populations supports the use of the non-study eye as a control for clinical trial purposes.
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http://dx.doi.org/10.1167/tvst.8.5.21DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6779097PMC
September 2019

The Utility of Frame Averaging for Automated Algorithms in Analyzing Retinal Vascular Biomarkers in AngioVue OCTA.

Transl Vis Sci Technol 2019 Jan 18;8(1):10. Epub 2019 Jan 18.

Department of Cell Biology, Neurobiology, & Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA.

Purpose: This study proposes an optical coherence tomography angiography (OCTA) frame-averaging method and investigates the effects of the number of frames acquired and averaged on metrics quantifying the foveal avascular zone (FAZ), vessel morphology, and parafoveal intercapillary area (PICA).

Methods: Ten OCTA frames were acquired for each of the 19 subjects without known retinal disease using the AngioVue OCTA system. For each subject, acquired frames were ranked by an image quality metric. A subset of frames was then registered and averaged. The effects of the number of frames acquired and averaged on FAZ segmentation and metrics of FAZ geometry, vessel morphology, and PICA were analyzed.

Results: Frame averaging increased the accuracy of the automatically segmented FAZ region; for example, the absolute error in FAZ area decreased from 0.026 mm (1 frame) to 0.005 mm (5 frames). Averaging multiple frames exponentially decreased the estimated number of vessel endpoints and increased the average vessel length with a 32% decrease in number of endpoints and 14% increase in average vessel length when averaging five frames compared with one. Frame averaging also improved the precision of PICA estimates.

Conclusions: Averaging multiple OCTA frames using the Optovue AngioVue system reduced error in FAZ segmentation and improved the robustness of OCTA vessel morphology and perfusion metrics. The study demonstrated limited benefit in acquiring and averaging more than five frames.

Translational Relevance: Averaging multiple OCTA frames improved the robustness of OCTA foveal biomarkers with limited benefit when averaging more than five frames.
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http://dx.doi.org/10.1167/tvst.8.1.10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6340247PMC
January 2019

Intraobserver Repeatability and Interobserver Reproducibility of Ellipsoid Zone Measurements in Retinitis Pigmentosa.

Transl Vis Sci Technol 2018 May 4;7(3):13. Epub 2018 Jun 4.

Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI, USA.

Purpose: To examine repeatability and reproducibility of ellipsoid zone (EZ) width measurements in patients with retinitis pigmentosa (RP) using a longitudinal reflectivity profile (LRP) analysis.

Methods: We examined Bioptigen optical coherence tomography (OCT) scans from 48 subjects with RP or Usher syndrome. Nominal scan lengths were 6, 7, or 10 mm, and the lateral scale of each scan was calculated using axial length measurements. LRPs were generated from OCT line scans, and the peak corresponding to EZ was manually identified using ImageJ. The locations at which the EZ peak disappeared were used to calculate EZ width. Each scan was analyzed twice by each of two observers, who were masked to their previous measurements and those of the other observer.

Results: On average, horizontal width (HW) was significantly greater than vertical width (VW), and there was high interocular symmetry for both HW and VW. We observed excellent intraobserver repeatability with intraclass correlation coefficients (ICCs) ranging from 0.996 to 0.998 for HW and VW measurements. Interobserver reproducibility was also excellent for both HW (ICC = 0.989; 95% confidence interval [CI] = 0.983-0.995) and VW (ICC = 0.991; 95% CI = 0.985-0.996), with no significant bias observed between observers.

Conclusions: EZ width can be measured using LRPs with excellent repeatability and reproducibility. Our observation of greater HW than VW is consistent with previous observations in RP, though the reason for this anisotropy remains unclear.

Translational Relevance: We describe repeatability and reproducibility of a method for measuring EZ width in patients with RP or Usher syndrome. This approach could facilitate measurement of retinal band thickness and/or intensity.
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http://dx.doi.org/10.1167/tvst.7.3.13DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5989764PMC
May 2018

A case of congenital retinal macrovessel in an otherwise normal eye.

Am J Ophthalmol Case Rep 2017 Dec 9;8:18-21. Epub 2017 Sep 9.

Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, WI, United States.

Purpose: To present the case of a 37-year-old female with a foveal macrovessel.

Observations: The patient had an incidental finding of congenital retinal macrovessel (CRM) in the left eye on optical coherence tomography (OCT). Visual acuity was normal, and slit lamp and dilated fundus examinations were otherwise unremarkable. OCT angiography (OCTA) imaging allowed for visualization of the depth profile of the vessel as well as the foveal avascular zone (FAZ). The FAZ and foveal pit were both smaller in the affected eye compared to the fellow eye.

Conclusions And Importance: We describe findings of OCTA imaging in a patient with CRM. Previous reports have relied on examination using fluorescein angiography, which does not provide sufficient axial resolution to discern the different vascular plexuses. This report further characterizes how this rare condition can affect foveal morphology and retinal vasculature.
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http://dx.doi.org/10.1016/j.ajoc.2017.09.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5731666PMC
December 2017

INTRAOPERATIVE IMAGING OF RETAINED PERFLUOROCARBON LIQUID USING SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY.

Retin Cases Brief Rep 2019 ;13(4):381-384

Department of Ophthalmology & Visual Sciences, Medical College of Wisconsin, Milwaukee, Wisconsin.

Purpose: To report images of retained perfluorocarbon liquid (PFCL) on the surface of the retina obtained during an intraoperative use of hand-held spectral domain optical coherence tomography.

Methods: A 54-year-old man underwent pars plana vitrectomy with injection of PFCL to repair retinal detachment. Postoperatively, visually significant PFCL droplets were found to be retained in the eye. During the surgical removal of PFCL, a hand-held spectral domain optical coherence tomography was used to image the retina with the patient supine.

Results: Spectral domain optical coherence tomography images of the retained PFCL illustrated magnification of the areas of the outer retina underlying PFCL bubbles. The images obtained had some similarities to the patient's own observation of "floaters."

Conclusion: Droplets of PFCL over the retina result in imaging artifact, most likely due to a lensing effect caused by differences in refractive index between the PFCL and vitreous humor. Although the utility of hand-held spectral domain optical coherence tomography for infants has previously been established, this case presents further application of spectral domain optical coherence tomography in adults when imaging in the supine position is required.
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http://dx.doi.org/10.1097/ICB.0000000000000607DOI Listing
March 2020
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