624712
research-article2015
DSTXXX10.1177/1932296815624712Journal of Diabetes Science and TechnologyMendez et al
Special Section
Feasibility of Spectral Domain Optical Coherence Tomography Acquisition Using a Handheld Versus Conventional Tabletop Unit
Journal of Diabetes Science and Technology 2016, Vol. 10(2) 277–281 © 2015 Diabetes Technology Society Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1932296815624712 dst.sagepub.com
Nicole Mendez1, Natasha V. Nayak, MD2, Anton M. Kolomeyer, MD, PhD3, Ben C. Szirth, PhD1, and Albert S. Khouri, MD1
Abstract Purpose: Patients afflicted with ocular complications of diabetes represent a diverse demographic who often cannot undergo spectral-domain optical coherence tomography (SD-OCT) imaging of the retina due to postural restraints. Our pilot study compared imaging acquisition methods using SD-OCT in the handheld (HH) mode versus the conventional tabletop (TT) method. Methods: Our study included 22 undilated eyes of 22 subjects (mean ± SD age, 35.8 ± 16.8 years) imaged using HH and TT iVue SD-OCT (Optovue, Fremont, CA). Statistical analysis was performed using Microsoft Excel 12.2.7 (Microsoft Corporation, Redmond, WA) software with an accepted significance of P < .05. Results: Strong intraclass correlation coefficient was observed for (1) overall (.97), superior (.93), and inferior (.94) ganglion cell complex thickness, and (2) central (.98), inferior (.90), superior (.92), nasal (.94), and temporal (.93) macular retinal thickness. Mean scan quality index was adequate but lower in HH versus TT SD-OCT (62.8 vs 68.1, respectively; P < .0001). Multiple attempts for adequate imaging were required more frequently in HH versus TT SD-OCT (34% vs 5%, respectively; P < .001). Conclusion: HH SD-OCT may be a feasible alternative to TT SD-OCT in select situations, especially in patients suffering from diabetic complications with limited mobility. Keywords diabetes, imaging methods, optical coherence tomography, macula/fovea Diabetes mellitus is considerably one of the most prevalent endocrine disorders, with an estimated 8.3% of the world’s adult population affected.1 This chronic endocrine and metabolic condition manifests in people of all ages. The highest number of people afflicted with diabetes is between the ages of 40 and 59.1 An estimated 80 000 cases present yearly involving patients younger than 15 years, with an increase in incidence of 4% predicted.2-4 This worldwide diabetes epidemic has become a global burden, contributing to an estimated US$548 billion in health expenditures and 5.1 million deaths attributed to the disease in 2013.1 By 2035 an estimated 592 million people will be afflicted with this disorder.1 The rise in new cases of type 1 diabetes is associated with the development of its often-devastating complications. The complications of diabetes have been specifically classified by Melendez-Ramirez et al5 into 2 groups: micro vascular or macro vascular manifestations. Among the micro vascular
complications is diabetic retinopathy (DR), one of the most negative complications affecting a diabetics’ quality of life. This potentially blinding complication represents the most recurrent cause of blindness for adults aged 20 to 74 years.6 The Wisconsin Epidemiologic Study of Diabetic Retinopathy reported 3.6% of type 1 diabetic patients suffering from legal blindness.7 Due to the macrovascular complications of diabetes such as: peripheral vascular disease, foot and leg 1
Department of Ophthalmology and Visual Science, Rutgers New Jersey Medical School, Newark, NJ, USA 2 Department of Ophthalmology, New York Eye and Ear Infirmary of Mount Sinai, NY, USA 3 Department of Ophthalmology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA Corresponding Author: Albert S. Khouri, MD, Rutgers New Jersey Medical School, 90 Bergen St, Ste 6100, PO Box 1709, Newark, NJ 07103, USA. Email:
[email protected]
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ulcers and diabetes-related amputations;8,9 this patient population may be wheelchair bound and can experience limited access to table-mounted equipment during ocular screenings. Spectral-domain optical coherence tomography (SD-OCT) has proven its role as a valid method in diagnosing visionthreatening diseases,10 particularly the morphological changes seen in the retina secondary to retinal vein occlusion, DR, and macular edema.11 However, most SD-OCT platforms are attached to a table, thereby limiting its potential widespread use in community eye screenings; especially for patients who have limited head and neck mobility, are in a permanent recumbent position or are noncompliant. Based on our experience throughout the past decade in performing community-based ocular screenings for the indigent population,12,13 we found that reliable follow-up is particularly difficult to achieve. It is therefore vital to have prompt access to easily mobile equipment capable of obtaining high-resolution imaging, to provide early diagnosis and appropriate management of vision threatening diseases. Current tabletop (TT) SD-OCT platforms are not amenable for use in recumbent, chair-bound patients, as well as those in the ICU and the OR setting. Some of the current SD-OCT equipment is more compact and lighter in weight facilitating its use in the handheld (HH) position. Implementation of HH SD-OCT14-16 technology may enhance the usability and applicability of this technology. However, to our knowledge, there have been no studies comparing the quality and feasibility of HH image acquisition to standard TT imaging. In the following, we present results of a comparative, imaging study of TT versus HH SD-OCT technology during community eye screenings. The analysis focuses on intraclass correlation, scan quality index, and need for repeat imaging.
both HH and TT SD-OCT (Optovue iVue SD-OCT Wellness report; Optovue Corporation, Fremont, CA), and (3) an onsite medical director (ASK) who assessed the screening data, reviewed the images, counseled participants regarding the results and referred selected participants for follow-up examinations if necessary. For the purpose of this study, only the left eye was included in this analysis. Based on the image quality scale of the SD-OCT machine, as well as subjective determination of image quality by the imaging professional, a repeat image was obtained when appropriate. The total number of required imaging attempts was recorded. All scans were processed in under 2 minutes using the Optovue iVue SD-OCT iWellness software (Optovue, Fremont, CA). The iWellness report is based on a single scan and provides the following data: (1) retinal thickness (central, superior, inferior, nasal, and temporal quadrants) and (2) ganglion cell complex thickness (GCT; total, superior, and inferior). A representative comparison of TT versus HH SD-OCT iWellness report is presented in Figure 1. Images were presented in a randomized order and quality was assessed independently by an ophthalmologist (ASK) and 2 ophthalmology residents (AMK, NVN). Unique to the Optovue software, is the device’s ability to calculate the average of all scanned images and determine the best use for clinical evaluation on 0-100 scale. The instrument deems an image quality greater than 40 as sufficient for clinical evaluation. When more than 1 image was obtained per eye, the highest was used for statistical comparison. Statistical analysis was performed using Microsoft Excel 12.2.7 (Microsoft Corporation, Redmond, WA) software. Data are presented as mean ± standard deviation (SD) unless otherwise noted. Paired t test and Pearson correlation coefficient tests were used where appropriate. A P value less than .05 was considered statistically significant.
Methods
Results
This cross-sectional, pilot-imaging study was approved by the Rutgers University Internal Review Board and fulfilled HIPAA compliance. The imaging was performed at telemedicine eye screenings in Newark, New Jersey, in 2013. The screening protocol was explained and consent was obtained from all subjects. The screening participants were assigned a morning or afternoon session, which in our experience improves cooperation. Inclusion criteria included age (18 years or older) and clear media (ie, cornea, lens, vitreous). Exclusion criteria included significant corneal opacification, dense cataract, or any other pathology precluding high quality posterior segment imaging. A thorough description of our adult screening procedure has been previously published.17 In brief, the screening team consisted of (1) senior medical students who guided participants in the completion of an intake form, (2) an imaging professional (BCS) who acquired nonmydriatic images using
Twenty-one of 22 (95%) participants who presented to the screening session and met inclusion criteria were included in the study. Mean ± SD age was 35.8 ± 16.8 years; 57% were female; 71% were African American and 29% Caucasian. One subject was excluded due to significant media opacity and was advised to undergo a dilated eye examination by an eye care physician. Based on the iWellness image processing report, a strong intraclass correlation coefficient (ICC) was observed for overall (.97), superior (.93), and inferior (.94) GCT and for central (.98), inferior (.90), superior (.92), nasal (.94), and temporal (.93) retinal thickness. There were no statistically significant differences in GCT or retinal thickness between HH and TT SD-OCT (Table 1). Mean number of imaging attempts was 2.5 per eye, with 8 (38%) requiring multiple attempts. Multiple attempts were required more frequently in HH versus TT SD-OCT (34% vs 5%, respectively; P < .001).
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Figure 1. iWellness left eye images obtained during the screening process. (A) Tabletop image. (B) Handheld image.
Mean scan quality index was adequate but lower in HH versus TT SD-OCT (62.8 vs 68.1, respectively; P < .0001) (Table 2). A strong Pearson correlation coefficient (r = .832) was observed for image quality scores for HH versus TT.
Discussion For over 20 years, OCT technology has continued to revolutionize imaging acquisition and clinical diagnostics. With the advent of SD-OCT over a decade ago, imaging and resolving
power of ocular structures have evolved considerably in their ability to identify ocular pathologies.18 Its popularity among ocular professionals is primarily attributed to its ability to noninvasively investigate the eye and provide reproducible images necessary in the diagnosis of ocular pathologies such as DR. One of the most important factors in caring for those with diabetes is the premature detection of such manifestations.5 Thus, the need for early evaluation of the possible pathological complications of diabetes is essential in providing immediate and preventative treatment.19
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Table 1. Mean ± Standard Deviation Ganglion Cell Complex Thickness (GCT) and Macular Retinal Thickness (N = 21).
Mean total GCT Mean GCT (superior) Mean GCT (inferior) Mean macular retinal thickness (central) Mean macular retinal thickness (superior) Mean macular retinal thickness (inferior) Mean macular retinal thickness (nasal) Mean macular retinal thickness (temporal)
Handheld (μm)
Tabletop (μm)
P value
87.80 ± 11.63 86.71 ± 11.29
86.14 ± 11.68 85.29 ± 11.20
.086 .341
89.00 ± 12.69
87.14 ± 12.66
.319
238.81 ± 29.45
236.14 ± 32.39
.374
281.95 ± 20.89
283.14 ± 20.09
.159
278.33 ± 21.82
278.98 ± 21.25
.542
291.81 ± 23.31
292.74 ± 21.45
.531
269.50 ± 24.86
271.81 ± 20.99
.537 Figure 2. Optovue handheld spectral-domain optical coherence tomography technique in a recumbent patient with limited mobility. Image was captured in a nonmydriatic mode using a foot pedal (not shown).
Table 2. Image Quality Scores for Handheld Versus Tabletop Spectral-Domain Optical Coherence Tomography (N = 21). Quality score (%) 0-39 40-69 70-100
Handheld
Tabletop
2 13 6
0 12 9
The SD-OCT is a noninvasive, noncontact imaging system capable of generating high-resolution, ~5 micron optical cross sections of the retina and the optic nerve.20 Through a single axial scan, the SD-OCT generates its information by assessing the frequency spectrum of the interference between the stationary reference mirror and the reflected light.21 The repeatability of SD-OCT measurements overtime is important for correct interpretation for investigational and clinical use and its success has been proven over several studies.22,23 Current SD-OCT imaging modalities are readily applied to the ambulatory adult population. The size of the SD-OCT machines, along with the position and height of the chinrest, precludes its use in an immobile adult, suffering from diabetic complications. Thus, advancements in the design of SD-OCT are necessary to uphold its abilities in detecting ocular pathologies across the diverse patient population presenting with diabetes. Through our study, we have determined a need for incorporating HH SD-OCT imaging devices for the handicapped
population suffering from the manifestations of diabetes. The HH iVue SD-OCT was developed as a portable headpiece with a handle. By adding a laptop for ease of portability and a foot pedal that permits hands-free image acquisition in a nonambulatory patient, the iVue system was found to be a valuable tool in the handicapped and recumbent population during community eye screenings, surgeries, and office visits (Figure 2).24 By implementing the HH SD-OCT into everyday use, our goal was to improve the current, standard of care. HH SD-OCT technology possesses the ability to alter management of patients who are wheel-chair bound or have postural requirements that preclude other structural tests and expand eye screenings during which traditional TT SD-OCT imaging cannot be obtained. Despite statistically significantly lower mean scan quality and more frequent need for additional images to be obtained; clinically (as illustrated by GCT and macular thickness measurements) the HH SD-OCT positioning fared comparably to the TT SD-OCT setup. We therefore believe that the HH device is illustrative of some advancements for the future generations of this invaluable technology.
Conclusion Diabetic patients have witnessed first-hand a benefit in the use of SD-OCT in measuring macular and central fovea
Mendez et al thickness.25-27 In our study, HH SD-OCT output was strongly correlated with TT SD-OCT. Although HH SD-OCT required multiple attempts more frequently and had slightly lower quality, the HH SD-OCT is a feasible and reliable option for patients with postural restrictions, for who the TT SD-OCT is not applicable. In utilizing its foot paddle for image capture, the HH SD-OCT provided quality images and proved conducive to community eye screenings requiring portability. The benefits of the HH SD-OCT were evident by its lightweight, portable, and user-friendly nature. Our results demonstrating the feasibility of HH SD-OCT as an alternative to TT SD-OCT warrants further investigation on the overall imaging data reliability, repeatability, and applicability to community screenings, tele-screening, use in the diabetic population, and other situations. Abbreviations DM1, type 1 diabetes mellitus; DR, diabetic retinopathy; GCT, ganglion cell complex thickness; HH, handheld; ICC, intraclass correlation coefficient; SD-OCT, spectral domain optical coherence tomography; TT, tabletop.
Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.
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