Publications by authors named "Dara Koozekanani"

33 Publications

Short term visual and structural outcomes of anti-vascular endothelial growth factor (anti-VEGF) treatment delay during the first COVID-19 wave: A pilot study.

PLoS One 2021 17;16(2):e0247161. Epub 2021 Feb 17.

Department of Ophthalmology and Visual Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States of America.

Regularly scheduled intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections are essential to maintaining and/or improving many ocular conditions including: neovascular age-related macular degeneration (nAMD), diabetic retinopathy, and retinal vein occlusions with macular edema (RVO). This study aims to assess the effect of unintended delays in anti-VEGF treatment during the first wave of the COVID-19 pandemic. This retrospective case series identified patients receiving regularly scheduled anti-VEGF intravitreal injections based on current procedural terminology (CPT) code at two practices in Minnesota. Diagnoses were limited to nAMD, diabetic macular edema (DME), proliferative diabetic retinopathy, and RVO. Patients were divided into two groups based on whether they maintained or delayed their follow-up visit by more than two weeks beyond the recommended treatment interval during the COVID-19 lockdown. The 'COVID-19 lockdown' was defined as the period after March, 28th, 2020, when a lockdown was declared in Minnesota. We then compared the visual acuity and structural changes to the retina using ocular coherence tomography (OCT) to assess whether delayed treatment resulted in worse visual outcomes. A total of 167 eyes from 117 patients met criteria for inclusion in this study. In the delayed group, the average BCVA at the pre- and post-lockdown visits were 0.614 and 0.715 (logMAR) respectively (p = 0.007). Central subfield thickness (CST) increased from 341 to 447 in the DME delayed group (p = 0.03) while the CST increased from 301 to 314 (p = 0.4) in the nAMD delayed group. The results of this pilot study suggests that treatment delays may have a negative impact on the visual and anatomic outcomes of patients with nAMD and DME. Future studies with larger sample sizes are required for further investigation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0247161PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7888661PMC
March 2021

Bilateral Ocular Ischemic Syndrome in the Setting of Chronic Angle Closure Glaucoma.

J Glaucoma 2021 05;30(5):e262-e264

Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN.

We report novel case of a 57-year-old woman who developed bilateral ocular ischemic syndrome in the setting of chronic angle closure glaucoma without associated angle neovascularization. Detailed is a course in which markedly prolonged, elevated intraocular pressure led to significantly reduced arterial perfusion at the level of the central retinal artery, leading to the clinical picture of ocular ischemic syndrome.
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http://dx.doi.org/10.1097/IJG.0000000000001767DOI Listing
May 2021

Title: BILATERAL UVEITIS AND HYPOTONY FOLLOWING TREATMENT WITH TOPICAL CIDOFOVIR.

Retin Cases Brief Rep 2020 Nov 20. Epub 2020 Nov 20.

Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota.

Purpose: To report a case of bilateral uveitis and hypotony associated with topical cidofovir treatment.

Methods: Case report.

Results: A 59-year-old diabetic male with HIV/AIDS presented with photophobia, ocular pain, and decreased vision. He was found to have bilateral hypotony, anterior uveitis, and serous choroidal detachments. Infectious disease workup, patient-reported history, and review of the patient's electronic medication list did not identify the etiology. Treatment with intensive topical corticosteroids led to resolution of uveitis and choroidal effusions within 3 months and resolution of hypotony within 9 months. Two years after his initial presentation, the patient developed acute recurrence of bilateral hypotony, anterior uveitis, and serous choroidal detachments shortly after intravenous cidofovir treatment. Careful re-evaluation of the patient's outside medical records revealed that he had initiated treatment for rectal herpes simplex virus with compounded topical cidofovir one month prior to his initial presentation.

Conclusion: To our knowledge, this is the first reported case of topical cidofovir causing ocular toxicity. Compounded and topical medications, like cidofovir in this case, may not appear on a patient's electronic medication list, so a focused review of outside medical records may be beneficial when a particular medication toxicity is suspected.
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http://dx.doi.org/10.1097/ICB.0000000000001101DOI Listing
November 2020

Comparing fundus autofluorescence and infrared imaging findings of peripheral retinoschisis, schisis detachment, and retinal detachment.

Am J Ophthalmol Case Rep 2020 Jun 26;18:100666. Epub 2020 Mar 26.

Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA.

Purpose: The primary goal of this study was to identify characteristic features of peripheral degenerative retinoschisis (RS), schisis detachment (SD) and retinal detachment (RD) on both fundus autofluorescence (FAF) and infrared (IR) imaging, using spectral domain optical coherence tomography (SD-OCT) imaging of the peripheral retina as the confirmatory imaging tool.

Methods: This is a descriptive case series study. A total of 27 eyes of 22 patients were included. Thirteen eyes of 10 patients diagnosed with RS, 4 eyes of 3 patients diagnosed with SD, and 10 eyes of 9 patients diagnosed with RD were included. Patients with images of poor quality were excluded. Heidelberg Spectralis HRA + OCT machine (Heidelberg Engineering, Heidelberg, Germany) were used to acquire the images.

Results: All conditions appeared as areas of hypo-AF on FAF and hypo-reflectance on IR imaging. Accentuated vasculature of the lesion was noted with IR imaging due to elevation of the RS and RD, which was less frequently observed with FAF. On FAF, a hyper-AF leading edge around the RS lesion indicated the presence of intraretinal or subretinal fluid and an extension of the RS. Retinal breaks/holes were best visualized with IR imaging. SD-OCT confirmed the diagnosis in all performed cases.

Conclusions: We were unable to differentiate between RS and RD based solely on findings from FAF and IR imaging. However, the combination of them with SD-OCT can assist in the diagnosis of RS from RD and in the evaluation of RS progression. OCT remains the main modality imaging to differentiate these conditions.
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http://dx.doi.org/10.1016/j.ajoc.2020.100666DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7125323PMC
June 2020

Presumed mast cell choroidal infiltrate in aggressive systemic mastocytosis.

Am J Ophthalmol Case Rep 2020 Jun 4;18:100614. Epub 2020 Feb 4.

Department of Ophthalmology and Visual Neuroscience, University of Minnesota, Minneapolis, MN, USA.

Purpose: To report a rare case of a unilateral choroidal mast cell infiltration in a patient with aggressive systemic mastocytosis (ASM).

Observations: The patient is a man in his fifties with a diagnosis of ASM. He developed visual complaints in the right eye associated with an area of subretinal fluid on fundus examination. Visual acuity at presentation was 20/150 in the right eye and 20/25 in the left eye. After ophthalmic and radiologic imaging workup, the patient was diagnosed with presumed choroidal mast cell infiltrate. The index of suspicion was high due to the prior ASM diagnosis. External beam radiation and intravitreal injection treatments were offered but the patient declined. The patient was switched from interferon to a new targeted systemic therapy for ASM, midostaurin. Despite some mixed, temporary response in systemic symptoms/signs of ASM at four months, the choroidal lesion and subretinal fluid were stable with visual acuity at 20/125.

Conclusion And Importance: Mast cell choroidal infiltration in ASM should be considered as part of the differential with acute/subacute vision changes. Diagnosis requires exclusion of other possibilities with ocular imaging and in this case, monitoring for development of other malignancies in which there were none. Midostaurin's ocular response was not on par with systemic response. Additional localized ocular therapies may be required.
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http://dx.doi.org/10.1016/j.ajoc.2020.100614DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021538PMC
June 2020

ADVERSE EVENTS OF THE ARGUS II RETINAL PROSTHESIS: Incidence, Causes, and Best Practices for Managing and Preventing Conjunctival Erosion.

Retina 2020 Feb;40(2):303-311

Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea.

Purpose: To analyze and provide an overview of the incidence, management, and prevention of conjunctival erosion in Argus II clinical trial subjects and postapproval patients.

Methods: This retrospective analysis followed the results of 274 patients treated with the Argus II Retinal Prosthesis System between June 2007 and November 2017, including 30 subjects from the US and European clinical trials, and 244 patients in the postapproval phase. Results were gathered for incidence of a serious adverse event, incidence of conjunctival erosion, occurrence sites, rates of erosion, and erosion timing.

Results: Overall, 60% of subjects in the clinical trial subjects versus 83% of patients in the postapproval phase did not experience device- or surgery-related serious adverse events. In the postapproval phase, conjunctival erosion had an incidence rate of 6.2% over 5 years and 11 months. In 55% of conjunctival erosion cases, erosion occurred in the inferotemporal quadrant, 25% in the superotemporal quadrant, and 20% in both. Sixty percent of the erosion events occurred in the first 15 months after implantation, and 85% within the first 2.5 years.

Conclusion: Reducing occurrence of conjunctival erosion in patients with the Argus II Retinal Prosthesis requires identification and minimization of risk factors before and during implantation. Implementing inverted sutures at the implant tabs, use of graft material at these locations as well as Mersilene rather than nylon sutures, and accurate Tenon's and conjunctiva closure are recommended for consideration in all patients.
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http://dx.doi.org/10.1097/IAE.0000000000002394DOI Listing
February 2020

RETOUCH: The Retinal OCT Fluid Detection and Segmentation Benchmark and Challenge.

IEEE Trans Med Imaging 2019 08 26;38(8):1858-1874. Epub 2019 Feb 26.

Retinal swelling due to the accumulation of fluid is associated with the most vision-threatening retinal diseases. Optical coherence tomography (OCT) is the current standard of care in assessing the presence and quantity of retinal fluid and image-guided treatment management. Deep learning methods have made their impact across medical imaging, and many retinal OCT analysis methods have been proposed. However, it is currently not clear how successful they are in interpreting the retinal fluid on OCT, which is due to the lack of standardized benchmarks. To address this, we organized a challenge RETOUCH in conjunction with MICCAI 2017, with eight teams participating. The challenge consisted of two tasks: fluid detection and fluid segmentation. It featured for the first time: all three retinal fluid types, with annotated images provided by two clinical centers, which were acquired with the three most common OCT device vendors from patients with two different retinal diseases. The analysis revealed that in the detection task, the performance on the automated fluid detection was within the inter-grader variability. However, in the segmentation task, fusing the automated methods produced segmentations that were superior to all individual methods, indicating the need for further improvements in the segmentation performance.
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http://dx.doi.org/10.1109/TMI.2019.2901398DOI Listing
August 2019

OCT Fluid Segmentation using Graph Shortest Path and Convolutional Neural Network

Annu Int Conf IEEE Eng Med Biol Soc 2018 Jul;2018:3426-3429

Diagnosis and monitoring of retina diseases related to pathologies such as accumulated fluid can be performed using optical coherence tomography (OCT). OCT acquires a series of 2D slices (Bscans). This work presents a fully-automated method based on graph shortest path algorithms and convolutional neural network (CNN) to segment and detect three types of fluid including sub-retinal fluid (SRF), intra-retinal fluid (IRF) and pigment epithelium detachment (PED) in OCT Bscans of subjects with age-related macular degeneration (AMD) and retinal vein occlusion (RVO) or diabetic retinopathy. The proposed method achieves an average dice coefficient of 76.44%, 92.25% and 82.14% in Cirrus, Spectralis and Topcon datasets, respectively. The effectiveness of the proposed methods was also demonstrated in segmenting fluid in OCT images from the 2017 Retouch challenge.
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http://dx.doi.org/10.1109/EMBC.2018.8512998DOI Listing
July 2018

Association of Optic Nerve Head Drusen with Best Vitelliform Macular Dystrophy: A Case Series.

Case Rep Ophthalmol 2018 Jan-Apr;9(1):76-86. Epub 2018 Jan 26.

Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, USA.

Purpose: To report the association of optic nerve head (ONH) drusen with Best vitelliform macular dystrophy (BVMD).

Methods: Chart review.

Patients: Five patients from 3 families.

Results: Multimodal imaging and ophthalmic examination demonstrated findings consistent with ONH drusen, in association with BVMD, in 5 patients.

Conclusion: We report the association of BVMD with ONH drusen in 5 patients. This combination has previously been reported only once. We recommend that patients with a diagnosis of BVMD undergo autofluorescence and ultrasound imaging of the optic nerve to help facilitate this diagnosis, as some ONH drusen can be buried.
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http://dx.doi.org/10.1159/000485963DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5892333PMC
January 2018

Fully-automated segmentation of fluid regions in exudative age-related macular degeneration subjects: Kernel graph cut in neutrosophic domain.

PLoS One 2017 23;12(10):e0186949. Epub 2017 Oct 23.

Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN, United States of America.

A fully-automated method based on graph shortest path, graph cut and neutrosophic (NS) sets is presented for fluid segmentation in OCT volumes for exudative age related macular degeneration (EAMD) subjects. The proposed method includes three main steps: 1) The inner limiting membrane (ILM) and the retinal pigment epithelium (RPE) layers are segmented using proposed methods based on graph shortest path in NS domain. A flattened RPE boundary is calculated such that all three types of fluid regions, intra-retinal, sub-retinal and sub-RPE, are located above it. 2) Seed points for fluid (object) and tissue (background) are initialized for graph cut by the proposed automated method. 3) A new cost function is proposed in kernel space, and is minimized with max-flow/min-cut algorithms, leading to a binary segmentation. Important properties of the proposed steps are proven and quantitative performance of each step is analyzed separately. The proposed method is evaluated using a publicly available dataset referred as Optima and a local dataset from the UMN clinic. For fluid segmentation in 2D individual slices, the proposed method outperforms the previously proposed methods by 18%, 21% with respect to the dice coefficient and sensitivity, respectively, on the Optima dataset, and by 16%, 11% and 12% with respect to the dice coefficient, sensitivity and precision, respectively, on the local UMN dataset. Finally, for 3D fluid volume segmentation, the proposed method achieves true positive rate (TPR) and false positive rate (FPR) of 90% and 0.74%, respectively, with a correlation of 95% between automated and expert manual segmentations using linear regression analysis.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0186949PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5653365PMC
November 2017

Fully Automated Segmentation of Fluid/Cyst Regions in Optical Coherence Tomography Images With Diabetic Macular Edema Using Neutrosophic Sets and Graph Algorithms.

IEEE Trans Biomed Eng 2018 05 31;65(5):989-1001. Epub 2017 Jul 31.

This paper presents a fully automated algorithm to segment fluid-associated (fluid-filled) and cyst regions in optical coherence tomography (OCT) retina images of subjects with diabetic macular edema. The OCT image is segmented using a novel neutrosophic transformation and a graph-based shortest path method. In neutrosophic domain, an image is transformed into three sets: (true), (indeterminate) that represents noise, and (false). This paper makes four key contributions. First, a new method is introduced to compute the indeterminacy set , and a new -correction operation is introduced to compute the set in neutrosophic domain. Second, a graph shortest-path method is applied in neutrosophic domain to segment the inner limiting membrane and the retinal pigment epithelium as regions of interest (ROI) and outer plexiform layer and inner segment myeloid as middle layers using a novel definition of the edge weights . Third, a new cost function for cluster-based fluid/cyst segmentation in ROI is presented which also includes a novel approach in estimating the number of clusters in an automated manner. Fourth, the final fluid regions are achieved by ignoring very small regions and the regions between middle layers. The proposed method is evaluated using two publicly available datasets: Duke, Optima, and a third local dataset from the UMN clinic which is available online. The proposed algorithm outperforms the previously proposed Duke algorithm by 8% with respect to the dice coefficient and by 5% with respect to precision on the Duke dataset, while achieving about the same sensitivity. Also, the proposed algorithm outperforms a prior method for Optima dataset by 6%, 22%, and 23% with respect to the dice coefficient, sensitivity, and precision, respectively. Finally, the proposed algorithm also achieves sensitivity of 67.3%, 88.8%, and 76.7%, for the Duke, Optima, and the university of minnesota (UMN) datasets, respectively.
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http://dx.doi.org/10.1109/TBME.2017.2734058DOI Listing
May 2018

Artery/vein classification of retinal blood vessels using feature selection.

Annu Int Conf IEEE Eng Med Biol Soc 2016 Aug;2016:1320-1323

Automated classification of retinal vessels in fundus images is the first step towards measurement of retinal characteristics that can be used to screen and diagnose vessel abnormalities for cardiovascular and retinal disorders. This paper presents a novel approach to vessel classification to compute the artery/vein ratio (AVR) for all blood vessel segments in the fundus image. The features extracted are then subjected to a selection procedure using Random Forests (RF) where the features that contribute most to classification accuracy are chosen as input to a polynomial kernel Support Vector Machine (SVM) classifier. The most dominant feature was found to be the vessel information obtained from the Light plane of the LAB color space. The SVM is then subjected to one time training using 10-fold cross validation on images randomly selected from the VICAVR dataset before testing on an independent test dataset, derived from the same database. An Area Under the ROC Curve (AUC) of 97.2% was obtained on an average of 100 runs of the algorithm. The proposed algorithm is robust due to the feature selection procedure, and it is possible to get similar accuracies across many datasets.
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http://dx.doi.org/10.1109/EMBC.2016.7590950DOI Listing
August 2016

Automated detection of neovascularization for proliferative diabetic retinopathy screening.

Annu Int Conf IEEE Eng Med Biol Soc 2016 Aug;2016:1300-1303

Neovascularization is the primary manifestation of proliferative diabetic retinopathy (PDR) that can lead to acquired blindness. This paper presents a novel method that classifies neovascularizations in the 1-optic disc (OD) diameter region (NVD) and elsewhere (NVE) separately to achieve low false positive rates of neovascularization classification. First, the OD region and blood vessels are extracted. Next, the major blood vessel segments in the 1-OD diameter region are classified for NVD, and minor blood vessel segments elsewhere are classified for NVE. For NVD and NVE classifications, optimal region-based feature sets of 10 and 6 features, respectively, are used. The proposed method achieves classification sensitivity, specificity and accuracy for NVD and NVE of 74%, 98.2%, 87.6%, and 61%, 97.5%, 92.1%, respectively. Also, the proposed method achieves 86.4% sensitivity and 76% specificity for screening images with PDR from public and local data sets. Thus, the proposed NVD and NVE detection methods can play a key role in automated screening and prioritization of patients with diabetic retinopathy.
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http://dx.doi.org/10.1109/EMBC.2016.7590945DOI Listing
August 2016

ENDOGENOUS NOCARDIA ENDOPHTHALMITIS PRESENTING AS A MASS LESION IN A PATIENT WITH METATSTATIC NONSMALL CELL CARCINOMA OF THE LUNG.

Retin Cases Brief Rep 2019 Spring;13(2):145-149

Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota.

Purpose: To report a case of Nocardia cyriacigeorgica endophthalmitis.

Methods: Case report.

Results: A 71-year-old man on long-term steroid therapy for poor respiratory function from lung carcinoma and presumed recent liver metastases presented with a four week history of blurry vision in the left eye. Ophthalmic examination revealed a white elevated mass in the macula with hemorrhage, concerning for metastasis. The patient was treated for presumed ocular metastases but had poor response to radiotherapy and was diagnosed four weeks later with N. cyriacigeorgica by retinal biopsy. Despite intravitreal and systemic antibiotics, the patient had progression of disease and died of respiratory involvement.

Conclusion: Nocardia endogenous endophthalmitis can present as a mass retinal lesion in immunosuppressed patients with metastatic disease. Early vitreous and retinal biopsy may be required for definitive diagnosis and treatment. A pulmonary source of infection should be suspected and monitored closely.
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http://dx.doi.org/10.1097/ICB.0000000000000545DOI Listing
May 2019

The Effect of Scleral Buckling Surgery on Choroidal Thickness Measured by Enhanced Depth Optical Coherence Tomography: A Cross-Sectional Study.

Ophthalmol Ther 2016 Dec 6;5(2):215-222. Epub 2016 Sep 6.

Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA.

Introduction: To assess the anatomical changes taking place in the choroid after a scleral buckle (SB) procedure for retinal detachment repair.

Methods: This cross-sectional study looked at 23 adults with a history of unilateral retinal detachment repaired with a SB or other encircling element. The subjects underwent bilateral Enhanced Depth Spectral Domain Optical Coherence Tomography to image the choroid. The choroidal thickness (CT) was measured, and the non-operative eye was used as an internal control.

Results: CT was measured to be 170.8 ± 60.9 µm (mean ± SD) in eyes with SBs compared to 175.1 ± 61.9 µm in non-operative eyes. There was no statistically significant difference between the two groups (mean 4.3 µm, 95% CI -8.7, 17.3, p value 0.4973, paired t test).

Conclusion: Placement of an SB as part of a surgery to repair retinal detachment did not significantly alter CT at the macula.
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http://dx.doi.org/10.1007/s40123-016-0060-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5125122PMC
December 2016

Strategies for Improving Patient Comfort During Intravitreal Injections: Results from a Survey-Based Study.

Ophthalmol Ther 2016 Dec 2;5(2):183-190. Epub 2016 Aug 2.

Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA.

Introduction: Many ocular diseases require intravitreal injections of pharmacological agents. Optimizing patients' experiences during injections is important to ensure compliance and maintenance of quality of life. The objective of this study was to identify strategies to help alleviate discomfort during intravitreal injections.

Methods: A cross-sectional study surveying 128 patients during clinic visits between 2014 and 2015 in two outpatient Retina Clinics (one academic and one private). Patients receiving an intravitreal injection(s) for any retinal disorder were given a questionnaire with 10-yes/no responses for various potential strategies. Responses were stratified by sex, age (<30 years, 30-60 years, and >60 years) and total number of prior injections (0-9 injections, 10-20 injections and >20 injections).

Results: A total of 128 patients were surveyed: 59 males, 41 females and 28 with no sex specified. Our results identified four favorable strategies as those receiving more than 50% "yes" votes. These included the presence of technician/staff during the procedure, the use of a neck pillow, a verbal warning before the injection and performing injections in both eyes on the same day. Other specific strategies were identified for females, younger patients and those with greatest experience. These included: females preferred having their hand held during injections (P = 0.001) and using a stress ball (P = 0.000) when compared to males. Stratifying by age, patients 30-60 years old preferred having their hand held (P = 0.008) and background music (P = 0.007). Stratifying by prior injections, patients with >20 prior injections preferred having their hand held (P = 0.001), using a stress ball (P = 0.021) and, if necessary, having bilateral injections performed the same day to improve comfort (P = 0.037).

Conclusions: Having an extra staff member present during the injection, having a neck pillow, having a verbal warning prior to injection and having both eyes injected on the same day were indicated as favorable strategies by over half of those surveyed. Further, specific strategies were identified for females, younger patients (30-60 years old) and those with greatest experience (>20 injections).
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http://dx.doi.org/10.1007/s40123-016-0058-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5125120PMC
December 2016

Implantation of the Argus II Retinal Prosthesis in an Eye With Short Axial Length.

Ophthalmic Surg Lasers Imaging Retina 2016 Apr;47(4):369-71

The authors describe the implantation of the Argus II Retinal Prosthesis System (Argus II) (Second Sight Medical Products, Sylmar, CA) into a short axial length (AL) eye. The authors' main modification is the use of endocyclophotocoagulation (endo-CPC) to the ciliary processes in the area that the cable enters through the sclerotomy. This case describes the surgical technique necessary for successful implantation of the Argus II into a short AL eye. The use of endo-PC prevents chafing to the ciliary processes, does not affect postoperative intraocular pressure, and facilitates direct visualization of the structures during the surgery, preventing damage during implantation.
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http://dx.doi.org/10.3928/23258160-20160324-12DOI Listing
April 2016

3-D localization of Diabetic Macular Edema using OCT thickness maps.

Annu Int Conf IEEE Eng Med Biol Soc 2015 Aug;2015:4334-7

This paper presents a novel automated system that segments 3-D thickness maps of sub-retinal layers from healthy and abnormal OCT image stacks with Diabetic Macular Edema (DME). These automated thickness maps are well correlated (r > 0.7) with the manually segmented thickness maps. The thickness maps demonstrate highly irregular regions in the inner and outer nuclear layers for patients with DME when compared to the healthy images. The combined area of irregularity in the inner and outer nuclear layers can thereby be extracted as a novel metric with correlation r = 0.99 to track the severity of DME. No other existing automated algorithm has extracted inner sub-retinal layer thickness maps from OCT image stacks of DME patients. The proposed system is fast and robust in locating the sub-retinal changes caused by DME in the 3-D sub-retinal micro-structure.
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http://dx.doi.org/10.1109/EMBC.2015.7319354DOI Listing
August 2015

Optic Disc Boundary and Vessel Origin Segmentation of Fundus Images.

IEEE J Biomed Health Inform 2016 11 26;20(6):1562-1574. Epub 2015 Aug 26.

This paper presents a novel classification-based optic disc (OD) segmentation algorithm that detects the OD boundary and the location of vessel origin (VO) pixel. First, the green plane of each fundus image is resized and morphologically reconstructed using a circular structuring element. Bright regions are then extracted from the morphologically reconstructed image that lie in close vicinity of the major blood vessels. Next, the bright regions are classified as bright probable OD regions and non-OD regions using six region-based features and a Gaussian mixture model classifier. The classified bright probable OD region with maximum Vessel-Sum and Solidity is detected as the best candidate region for the OD. Other bright probable OD regions within 1-disc diameter from the centroid of the best candidate OD region are then detected as remaining candidate regions for the OD. A convex hull containing all the candidate OD regions is then estimated, and a best-fit ellipse across the convex hull becomes the segmented OD boundary. Finally, the centroid of major blood vessels within the segmented OD boundary is detected as the VO pixel location. The proposed algorithm has low computation time complexity and it is robust to variations in image illumination, imaging angles, and retinal abnormalities. This algorithm achieves 98.8%-100% OD segmentation success and OD segmentation overlap score in the range of 72%-84% on images from the six public datasets of DRIVE, DIARETDB1, DIARETDB0, CHASE_DB1, MESSIDOR, and STARE in less than 2.14 s per image. Thus, the proposed algorithm can be used for automated detection of retinal pathologies, such as glaucoma, diabetic retinopathy, and maculopathy.
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http://dx.doi.org/10.1109/JBHI.2015.2473159DOI Listing
November 2016

Association of Disorganization of Retinal Inner Layers With Vision After Resolution of Center-Involved Diabetic Macular Edema.

JAMA Ophthalmol 2015 Jul;133(7):820-5

Vitreoretinal Service, Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis.

Importance: Macular edema (ME) prognosis and treatment response vary according to the underlying abnormalities. Biomarkers of visual acuity (VA) improvement could influence management decisions in different types of ME.

Objective: To investigate whether disorganization of retinal inner layers (DRIL) and other spectral-domain optical coherence tomography (SD-OCT)-derived variables are associated with subsequent VA after ME resolution in both nondiabetic and diabetic ME.

Design, Setting, And Participants: A retrospective, longitudinal cohort study in which Snellen VA testing and SD-OCT macular imaging were performed, was conducted at a tertiary referral eye center for retinal diseases. The medical records of all patients with ME from December 1, 2010, to December 31, 2012, were reviewed. The date of the last follow-up was June 1, 2013. Participants included 55 patients (70 eyes) with center-involved ME that had resolved during an 8-month period. Patients were grouped based on the source of ME (diabetic vs nondiabetic). Exclusion criteria included significant media opacity interfering with good-quality SD-OCT image acquisition. Masked graders analyzed the central 1500-μm macular region for changes, including cysts, DRIL length and extent, and outer retinal layers disruption. Intragrader and intergrader agreement Spearman rank correlation coefficients ranged from 0.70 to 0.93 for quantitative measurement, and κ values ranged from 0.88 to 1.00 for qualitative grading.

Main Outcomes And Measures: Visual acuity and morphologic changes measured on SD-OCT.

Results: In both groups, VA after ME resolution correlated with baseline VA. In diabetic ME involving a multivariable model including baseline VA and DRIL, total length was associated with subsequent VA as determined by a parameter estimate (PE) of 0.0003 (95% CI, 0-0.0006) (P = .03). The VA change during the 8-month period, after adjusting for baseline VA, was best associated with DRIL change (PE, 0.0002 [95% CI, 0-0.0003]; P = .04). Participants whose DRIL resolved, both early and late, showed improvement in their VA deficit at 8 months (least squares mean [SE], 41.3 [28.5] and 40.9 [37.5], respectively) compared with nonresolvers, whether inconsistent or persistent, whose VA worsened. After adjustment for baseline VA, eyes with persistent DRIL showed the largest difference in VA deficit compared with those with no baseline DRIL (-89.6 [27.2] vs 49.7 [19.6], respectively; P = .006).

Conclusions And Relevance: The presence of DRIL at baseline and its resolution pattern may be associated with subsequent VA after resolution of center-involved diabetic ME.
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http://dx.doi.org/10.1001/jamaophthalmol.2015.0972DOI Listing
July 2015

Iterative Vessel Segmentation of Fundus Images.

IEEE Trans Biomed Eng 2015 Jul 13;62(7):1738-49. Epub 2015 Feb 13.

This paper presents a novel unsupervised iterative blood vessel segmentation algorithm using fundus images. First, a vessel enhanced image is generated by tophat reconstruction of the negative green plane image. An initial estimate of the segmented vasculature is extracted by global thresholding the vessel enhanced image. Next, new vessel pixels are identified iteratively by adaptive thresholding of the residual image generated by masking out the existing segmented vessel estimate from the vessel enhanced image. The new vessel pixels are, then, region grown into the existing vessel, thereby resulting in an iterative enhancement of the segmented vessel structure. As the iterations progress, the number of false edge pixels identified as new vessel pixels increases compared to the number of actual vessel pixels. A key contribution of this paper is a novel stopping criterion that terminates the iterative process leading to higher vessel segmentation accuracy. This iterative algorithm is robust to the rate of new vessel pixel addition since it achieves 93.2-95.35% vessel segmentation accuracy with 0.9577-0.9638 area under ROC curve (AUC) on abnormal retinal images from the STARE dataset. The proposed algorithm is computationally efficient and consistent in vessel segmentation performance for retinal images with variations due to pathology, uneven illumination, pigmentation, and fields of view since it achieves a vessel segmentation accuracy of about 95% in an average time of 2.45, 3.95, and 8 s on images from three public datasets DRIVE, STARE, and CHASE_DB1, respectively. Additionally, the proposed algorithm has more than 90% segmentation accuracy for segmenting peripapillary blood vessels in the images from the DRIVE and CHASE_DB1 datasets.
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http://dx.doi.org/10.1109/TBME.2015.2403295DOI Listing
July 2015

Reply: To PMID 24568725.

J Cataract Refract Surg 2014 Oct;40(10):1752-3

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http://dx.doi.org/10.1016/j.jcrs.2014.08.014DOI Listing
October 2014

DREAM: diabetic retinopathy analysis using machine learning.

IEEE J Biomed Health Inform 2014 Sep;18(5):1717-28

This paper presents a computer-aided screening system (DREAM) that analyzes fundus images with varying illumination and fields of view, and generates a severity grade for diabetic retinopathy (DR) using machine learning. Classifiers such as the Gaussian Mixture model (GMM), k-nearest neighbor (kNN), support vector machine (SVM), and AdaBoost are analyzed for classifying retinopathy lesions from nonlesions. GMM and kNN classifiers are found to be the best classifiers for bright and red lesion classification, respectively. A main contribution of this paper is the reduction in the number of features used for lesion classification by feature ranking using Adaboost where 30 top features are selected out of 78. A novel two-step hierarchical classification approach is proposed where the nonlesions or false positives are rejected in the first step. In the second step, the bright lesions are classified as hard exudates and cotton wool spots, and the red lesions are classified as hemorrhages and micro-aneurysms. This lesion classification problem deals with unbalanced datasets and SVM or combination classifiers derived from SVM using the Dempster-Shafer theory are found to incur more classification error than the GMM and kNN classifiers due to the data imbalance. The DR severity grading system is tested on 1200 images from the publicly available MESSIDOR dataset. The DREAM system achieves 100% sensitivity, 53.16% specificity, and 0.904 AUC, compared to the best reported 96% sensitivity, 51% specificity, and 0.875 AUC, for classifying images as with or without DR. The feature reduction further reduces the average computation time for DR severity per image from 59.54 to 3.46 s.
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http://dx.doi.org/10.1109/JBHI.2013.2294635DOI Listing
September 2014

Blood Vessel Segmentation of Fundus Images by Major Vessel Extraction and Subimage Classification.

IEEE J Biomed Health Inform 2015 May;19(3):1118-28

This paper presents a novel three-stage blood vessel segmentation algorithm using fundus photographs. In the first stage, the green plane of a fundus image is preprocessed to extract a binary image after high-pass filtering, and another binary image from the morphologically reconstructed enhanced image for the vessel regions. Next, the regions common to both the binary images are extracted as the major vessels. In the second stage, all remaining pixels in the two binary images are classified using a Gaussian mixture model (GMM) classifier using a set of eight features that are extracted based on pixel neighborhood and first and second-order gradient images. In the third postprocessing stage, the major portions of the blood vessels are combined with the classified vessel pixels. The proposed algorithm is less dependent on training data, requires less segmentation time and achieves consistent vessel segmentation accuracy on normal images as well as images with pathology when compared to existing supervised segmentation methods. The proposed algorithm achieves a vessel segmentation accuracy of 95.2%, 95.15%, and 95.3% in an average of 3.1, 6.7, and 11.7 s on three public datasets DRIVE, STARE, and CHASE_DB1, respectively.
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http://dx.doi.org/10.1109/JBHI.2014.2335617DOI Listing
May 2015

Delayed presentation of retained nuclear fragment following phacoemulsification cataract extraction.

J Cataract Refract Surg 2014 Apr 22;40(4):671-4. Epub 2014 Feb 22.

From the Department of Ophthalmology (Mokhtarzadeh, Kaufman, Koozekanani), University of Minnesota Medical School, Minneapolis, Minnesota, and the Department of Ophthalmology (Kaufman), State University of New York, Brooklyn, New York, USA; the Department of Surgical Specialties-Ophthalmology (Meduri), University of Messina, Italy.

Unlabelled: An 87-year-old woman presented 11 months after routine phacoemulsification cataract extraction and posterior chamber intraocular lens implantation in her left eye complaining of the abrupt onset of redness and decreased vision in that eye. Examination revealed a mild anterior chamber reaction and significant corneal edema. The eye was minimally responsive to topical steroid therapy, and initial serial slitlamp examinations with gonioscopy were unrevealing. After multiple head-positioning maneuvers were performed, a retained nuclear fragment was uncovered. The nuclear fragment was aspirated and liquefied by the phacoemulsification device in the anterior chamber. A retained nuclear fragment with an intact posterior capsule is a recognized cause of inflammation in the immediate postoperative presentation. Delayed presentation of symptoms is rare and presumably secondary to sequestration of the fragment behind the iris. We present a case and a review of the literature regarding sequestered retained nuclear fragments following what is initially thought to be uneventful cataract extraction.

Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.
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http://dx.doi.org/10.1016/j.jcrs.2014.02.013DOI Listing
April 2014

Automated localization of cysts in diabetic macular edema using optical coherence tomography images.

Annu Int Conf IEEE Eng Med Biol Soc 2013 ;2013:1426-9

This paper presents a novel automated system that localizes cysts in optical coherence tomography (OCT) images of patients with diabetic macular edema (DME). First, in each image, six sub-retinal layers are detected using an iterative high-pass filtering approach. Next, significantly dark regions within the retinal micro-structure are detected as candidate cystoid regions. Each candidate cystoid region is then further analyzed using solidity, mean and maximum pixel value of the negative OCT image as decisive features for estimating the area of cystoid regions. The proposed system achieves 90% correlation between the estimated cystoid area and the manually marked area, and a mean error of 4.6%. Finally the proposed algorithm locates the cysts in the inner plexiform region, inner nuclear region and outer nuclear region with an accuracy of 88%, 86% and 80%, respectively.
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http://dx.doi.org/10.1109/EMBC.2013.6609778DOI Listing
August 2015

Clinical and histopathologic findings after photodynamic therapy of choroidal melanoma.

Retina 2012 May;32(5):942-8

Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota 55905, USA.

Background: Photodynamic therapy (PDT) has been used occasionally as an alternative treatment for uveal melanomas. The present study describes the clinical and histopathologic features of five choroidal melanomas after PDT.

Methods: Three patients with pigmented choroidal melanomas were treated with PDT and intravitreal bevacizumab 1 week before undergoing biopsy and brachytherapy to minimize the risks of bleeding during the biopsy. Another two patients received PDT as a primary treatment for peripapillary amelanotic melanomas, one of them also in combination with bevacizumab.

Results: The tumors treated with PDT and bevacizumab showed a marked reduction in tumor vascularity assessed by indocyanine angiography, and the biopsies were conducted without recognizable bleeding, showing viable tumor cells. The tumors receiving PDT as a primary treatment were followed by progressive tumor growth that led to enucleation years after. The histopathology revealed overlying fibrosis with invasion of sclera and optic nerve.

Conclusion: Photodynamic therapy and bevacizumab can induce closure of the superficial vasculature of a pigmented choroidal melanoma, but in none of our cases, there was evidence of tumor destruction from this treatment. Preoperative PDT may be useful to reduce the potential of bleeding at the time of tumor biopsy. Our cases do not support the use of a single session of PDT as a primary treatment for pigmented small choroidal melanomas.
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http://dx.doi.org/10.1097/IAE.0b013e31825097c1DOI Listing
May 2012

RetCam II Fluorescein Angiography to Guide Treatment and Diagnosis of Coats Disease.

Ophthalmic Surg Lasers Imaging 2010 Mar 9:1-3. Epub 2010 Mar 9.

Coats disease is a well-described clinical condition featuring peripheral leakage from telangiectatic vasculature, resulting in exudative retinal detachments and exudative deposits. It often affects pediatric patients, requiring examinations and treatments to be performed under anesthesia. It can be difficult to distinguish from retinoblastoma. The RetCam II is a wide-field fundus imaging system that can also obtain intraoperative fluorescein angiography. The case of a 5-year-old girl diagnosed with Coats disease is presented. She presented with an exudative detachment, a submacular nodule, and peripheral telangiectasis. An examination under anesthesia, including angiography, was performed. The angiograph revealed characteristic aneurysms as well as extensive areas of telangiectasis and ischemia not readily visible on examination. The angiogram allowed more diagnostic certainty and guided a more complete treatment than otherwise possible. We propose that fluorescein angiography with the RetCam II system can be a useful tool when examining and treating pediatric patients with Coats disease.
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http://dx.doi.org/10.3928/15428877-20100215-86DOI Listing
March 2010

Hemorrhagic Retinoschisis in Shaken Baby Syndrome Imaged with Spectral Domain Optical Coherence Tomography.

Ophthalmic Surg Lasers Imaging 2010 Mar 9:1-3. Epub 2010 Mar 9.

Spectral domain optical coherence tomography (SD-OCT) images from an infant victim of shaken baby syndrome who presented with vitreous hemorrhage in the left eye and bilateral, large hemorrhages over both maculae. Both RetCam and SD-OCT images were obtained, demonstrating the position of the blood beneath the internal limiting membrane of the right macula. Image registration software was used to register the photographic images with the surface projection images obtained by the SD-OCT. In the left eye, the vitreous hemorrhage was removed with vitrectomy, and the retinoschisis cavity incised to allow drainage.
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http://dx.doi.org/10.3928/15428877-20100215-87DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3182288PMC
March 2010