Abstract
Purpose:
Optical coherence tomography (OCT) is useful in diagnosing and monitoring retinal pathology such as age-related macular degeneration, diabetic macular edema (DME), central serous chorioretinopathy, and epiretinal membrane, among others. This study compared the ability of horizontal (H) 25-, 13-, and 7-cut macular OCT vs 24-, 12-, and 6-cut radial (R) macular OCT in identifying various macular pathology.
Methods:
This was a prospective study of 161 established patients evaluated at Wilford Hall Eye Center Retina Clinic between September and October of 2019. Pathology included age-related macular degeneration, central serous chorioretinopathy, DME, and epiretinal membrane, among others. Patients obtained 25-, 13-, and 7-cut H raster OCT as well as 24-, 12-, and 6-cut R OCT. Primary outcomes were sensitivity in detecting macular fluid and each macular abnormality.
Results:
The 24-cut radial (R24) OCT equally or out-performed the H25 (horizontal 25-cut OCT) in detecting macular fluid across all pathological groups. Generally, a higher number of cuts correlated with better detection of fluid. In detecting any macular abnormalities, H25, R24, and R12 had 100% sensitivity. R6 OCT had near 100% sensitivity across all groups, except for DME (95%). Overall, R OCT had better sensitivity (0.960) than H OCT (0.907) in detecting macular pathology.
Conclusions:
R outperformed H macular OCT in detecting fluid and other abnormalities. Clinically, both scanning patterns can be used by ophthalmologists in diagnosis and management of commonly encountered macular diseases. Technicians may be able to use a variety of these scans to screen for pathology prior to physician evaluation.
Keywords: imaging, macula, OCT, retina
Introduction
Optical coherence tomography (OCT) is a noninvasive and safe method for obtaining detailed anatomical information in vivo. It is commonly used to monitor vision-threatening diseases such as diabetic retinopathy and age-related macular degeneration (AMD). 1 -3 OCT is a relatively quick, noninvasive, and consistent method to assess and help diagnose retinal pathology. 4 Recent studies have focused on the impact of OCT scan density on the qualitative analysis of conditions such as AMD 5 and diabetic macular edema (DME), 6 showing that lower scan densities were inferior to higher scan densities. However, despite these findings, the authors concluded that the lower-density results remain clinically acceptable. With new technology, retinal thickness and volume maps can be generated using only a small subset of B-scans in a volume cube, 6,7 allowing for quicker imaging with similar ability to make an accurate diagnosis.
Few studies compare the efficacy of different scan patterns (horizontal raster vs radial) in the evaluation of macular diseases. A study published in 2014 showed a clinically unacceptable rate of missed holes in standard horizontal raster scans (61-line, 20% missed holes) as compared with high-density radial scans (24-line, 0% missed holes) and even with lower-density radial scans (6-line, 12% missed holes). 8 This suggested that radial scans may facilitate enhanced foveal imaging as compared with horizontal scans.
The aim of this study was to determine the sensitivity of various OCT scan patterns and densities in the diagnosis of macular diseases. The results of this study will help clinicians determine the best parameters to use when evaluating, monitoring, and treating patients with a variety of macular disorders.
Methods
This is a prospective study of 161 patients evaluated at Wilford Hall Eye Center Retina Clinic (San Antonio, Texas) during September and October 2019. The inclusion criteria were both new and established patients with macular pathology. Exclusion criteria included absence of macular pathology and poor image quality on any scan (due to surface irregularity, media opacities, or any other cause). All imaging was obtained with Spectralis spectral-domain OCT (SD-OCT) imaging (Heidelberg Engineering Inc) using Automatic Real Time. For quicker acquisition of images, Automatic Real Time was reduced, although a minimal required image quality as determined by our retina specialist was maintained. Ophthalmic photographers were instructed to manually center each scan on the fovea when eccentric fixation was detected during OCT acquisition. Each patient underwent high-definition horizontal raster scan (25 cuts [H25]), followed by high-definition radial scan (24 cuts [R24]). Thirteen- and 7-line horizontal (H13 and H7, respectively) raster scans were then obtained, followed by 12- and 6-line radial (R12 and R6, respectively) scans using similar parameters to the high-definition volume scans.
All images were reviewed by a retina specialist (P.D.) after the time of the study to identify abnormalities. The presence or absence of pathology as well as subretinal (SRF) or intraretinal fluid (IRF) were noted for each scan type. The primary outcome was sensitivity in detecting macular pathology, which was calculated in the following way:
Sensitivity = true positive / (true positive + false negative).
All negative results (no macular pathology) were compared with the results of the different scans and densities for the same patient to see whether another scan identified pathology. If pathology was found on other scans then the normal reports were deemed false negatives.
Statistical analysis was performed using SPSS statistics, version 20.9 (IBM) with categorical variables reported as proportions and continuous variables as medians ± SD. Each identified disorder was grouped within similar pathological categories to help with statistical analysis, and these groups were each analyzed independently. Analyzed groups included AMD (wet, dry, and macular neovascularization in other disorders), vitreoretinal interface disorders (epiretinal membranes [ERMs], lamellar holes, vitreomacular adhesion and traction, and full-thickness macular holes), cystoid macular edema (CME; any cause, excluding diabetes), DME, and central serous chorioretinopathy (CSCR).
Results
A total of 161 patients met the inclusion criteria and were included in the study. Wet AMD (40%), ERM (16%), and DME (15.5%) were the most frequent macular pathologies identified (Table 1).
Table 1.
The Incidence of Macular Pathology Identified Across All 161 Patients.
| Primary diagnosis distribution | ||
|---|---|---|
| Pathology | Count | Percentage |
| CME | 20 | 12.4 |
| MNV | 8 | 5.0 |
| CSCR | 7 | 4.3 |
| DME | 25 | 15.5 |
| Dry AMD | 1 | 0.6 |
| ERM | 26 | 16.1 |
| LH | 2 | 1.2 |
| GA | 1 | 0.6 |
| HRVO | 1 | 0.6 |
| FTMH | 1 | 0.6 |
| Torpedo maculopathy | 1 | 0.6 |
| VMA | 1 | 0.6 |
| VMT | 3 | 1.9 |
| Wet AMD | 64 | 40.0 |
| Total | 161 | 100 |
Abbreviations: AMD, age-related macular degeneration; CME, cystoid macular edema; CSCR, central serous chorioretinopathy; DME, diabetic macular edema; ERM, epiretinal membrane; FTMH, full-thickness macular hole; GA, geographic atrophy; HRVO, hemiretinal vein occlusion; LH, lamellar hole; MNV, macular neovascularization; VMA, vitreomacular adhesion; VMT, vitreomacular traction.
In detecting macular IRF or SRF, R24 scans had the highest sensitivity across all macular pathology groups (Table 2), with sensitivities of 0.977, 1.00, 1.00, 1.00, and 0.917, for AMD, CME, CSCR, DME, and ERM groups, respectively. H25 was the scan type with the next highest sensitivity for detecting macular fluid across all pathological groups. For both horizontal and radial scans, the higher the number of cuts per scan, the greater the sensitivity. This was true with 1 exception: H7 scans had greater sensitivity detecting macular fluid (0.920) than H13 scans (0.880).
Table 2.
Sensitivity of Each Scan Type for Detecting Macular Fluid for All Groups of Macular Pathology.a
| Sensitivity for macular fluid | ||||||
|---|---|---|---|---|---|---|
| Pathology | H25 | H13 | H7 | R24 | R12 | R6 |
| AMDb | 0.930 | 0.837 | 0.837 | 0.977 | 0.907 | 0.814 |
| CMEc | 1.000 | 0.944 | 0.944 | 1.000 | 1.000 | 0.889 |
| CSCRd | 1.000 | 0.667 | 0.667 | 1.000 | 1.000 | 1.000 |
| DMEe | 0.960 | 0.880 | 0.920 | 1.000 | 0.960 | 0.960 |
| VRIf | 0.833 | 0.667 | 0.667 | 0.917 | 0.750 | 0.667 |
Abbreviations: AMD, age-related macular degeneration; CME, cystoid macular edema; CSCR, central serous chorioretinopathy; DME, diabetic macular edema; H, horizontal; R, radial; VRI, vitreoretinal interface disorders.
aThe 1 case of torpedo maculopathy was excluded from grouped analysis.
bIncludes wet/dry AMD, macular neovascularization, and geographic atrophy (n = 74 patients).
cIncludes hemiretinal vein occlusion (n = 21 patients).
dn = 7 patients.
en = 25 patients.
fIncludes epiretinal membrane, lamellar hole, full-thickness macular hole, vitreomacular adhesion, and vitreomacular traction (n = 33 patients).
Radial OCT had near 100% sensitivity in detecting pathology. For high-density scans (R24 and R12), this rate was 1.00 for all groups of pathological groups. Low-density radial OCT (R6) had rates of 1.00, 0.950, 1.00, 1.00, and 1.00 in detecting abnormalities in AMD, CME, CSCR, DME, and vitreoretinal interface disorders, respectively. These rates for high-, intermediate-, and low-density radial scans outperformed horizontal raster intermediate (H13) and low-density (H7) OCT (Table 3). H13 and H7 did not demonstrate 100% sensitivity in detecting any group of pathology.
Table 3.
Sensitivity of Each Scan Type in Detecting Macular Pathology for Each Group of Pathology.
| Sensitivity for macular pathology | ||||||
|---|---|---|---|---|---|---|
| Pathology | H25 | H13 | H7 | R24 | R12 | R6 |
| AMD | 1.000 | 0.986 | 0.986 | 1.000 | 1.000 | 1.000 |
| CME | 1.000 | 0.950 | 0.950 | 1.000 | 1.000 | 0.950 |
| CSCR | 1.000 | 0.857 | 0.857 | 1.000 | 1.000 | 1.000 |
| DME | 1.000 | 0.960 | 0.960 | 1.000 | 1.000 | 1.000 |
| VRI | 1.000 | 0.970 | 0.970 | 1.000 | 1.000 | 1.000 |
Abbreviations: AMD, age-related macular degeneration; CME, cystoid macular edema; CSCR, central serous chorioretinopathy; DME, diabetic macular edema; H, horizontal; R, radial; VRI, vitreoretinal interface disorders.
In each different pathological group, both for horizontal and radial scans, the higher-cut scans had equal to or greater sensitivity in detecting abnormalities than fewer-cut scans, with no exceptions (Table 3). The average sensitivity, when taken from all disease groups, was 0.972, 0.872, and 0.876 for H25, H13, and H7, respectively, as well as 0.989, 0.962, and 0.928 for R24, R12, and R6, respectively (Table 4).
Table 4.
Average Sensitivity of Each Subtype (Cut Number) of Horizontal (H) and Radial (R) Optical Coherence Tomography in Detecting All Macular Pathologies Listed in Table 1.
| Average sensitivity per lines used in scan | |
|---|---|
| H25 | 0.972 |
| H13 | 0.872 |
| H7 | 0.876 |
| R24 | 0.989 |
| R12 | 0.962 |
| R6 | 0.928 |
Overall, radial OCT had greater sensitivity (0.960) than horizontal raster OCT (0.907) in identifying macular abnormalities.
Conclusions
The purpose of this study was to compare the sensitivity of different SD-OCT scan patterns and densities in detecting macular pathology. Although similar studies have been previously performed, 9,10 this study compared the Heidelberg OCT R24 with the H25 scan, which is a novel comparison. Our results suggest that, for the most part, greater scan density provides greater sensitivity in detecting macular fluid and other abnormalities, with 1 exception. H7 OCT identified macular fluid in patients with DME that H13 OCT missed (sensitivity of 0.920 vs 0.880). This may suggest utility in using multiple scans with different numbers of cuts in patients with DME.
A study from 2014 that was conducted at Wills Eye Hospital (Philadelphia, PA) compared H25 vs R6 OCT in detecting fluid in neovascular AMD. They found better detection ability in the high-density horizontal OCT compared with the low-density radial scan. 9 We found similar results in our study: H25 was better than R6 at detecting macular fluid in patients with neovascular AMD (93% vs 81% sensitivity, respectively). They also found 4 false negatives in R6 when screening for fluid in DME, which H25 was able to pick up on (n = 140 for DME). 9 In contrast, we found equal sensitivity between H25 and R6 scans in DME screening (see Table 2), albeit with a smaller sample size (n = 140 vs n = 25). A later study published in 2016 compared R12 with H25 in detecting abnormalities in neovascular AMD. They found 98.3% and 97.5% diagnostic sensitivity, respectively, 10 which was better than the sensitivity we found (91% vs 93%; see Table 2). Based on our results, macular fluid was best identified in pathology groups via R24 OCT.
In screening for any macular abnormalities, radial OCT outperformed horizontal raster OCT in both low- and intermediate-density cuts. Both types of high-density scans (R24 and H25) performed exceptionally well, with 100% sensitivity in detecting macular abnormalities across all pathology groups. This illustrates that R6, R12, R24, and H25 OCT all provide superb sensitivity in finding macular abnormalities. Clinically, the H7 and H13 also demonstrated high sensitivity, with few false negatives. However, moving forward, to eliminate these false negatives in clinical practice, clinicians may consider using the previously mentioned scans (R6, R12, R24, and H25) in favor of the lower-density horizontal scans.
We suspect that radial scans outperformed horizontal scans overall (0.96 vs 0.907 sensitivity, respectively) because they, by definition, pass through the macular center and are thus best at identifying IRF/SRF and other pathology. In addition, the scan time differences between the 2 protocols are minimal. Thus, when screening for macular pathology, it may be more beneficial to use a radial scan protocol. When the most detail for the pathology under question is desired, a higher-definition line scan centered on the pathology may likely be best.
An important topic for discussion is clinical efficiency and utility of screening for any macular abnormalities. Moving forward, these high-sensitivity scans may be able to be used in coordination with artificial intelligence to screen for pathology and guide closer evaluation by the vitreoretinal specialist. Once the scan is identified as abnormal, the clinician can investigate further, especially in conditions such as neovascular AMD and DME, for which fluid detection weighs heavily on the direction of clinical management. This may improve overall clinic flow and maximize efficiency.
Limitations of this study included the following: All scans were evaluated by 1 retina specialist at a single academic institution, and the results were from a single SD-OCT machine (Heidelberg Spectralis). It is possible that different OCT machines may lead to different results. In addition, our study included a relatively small number of patients, especially for the CSCR group (n = 7), with wide variability among analyzed groups (AMD, n = 74). Future studies may achieve larger sample sizes across pathological groups. Finally, in our methodology there were no false positives. If an abnormality was determined by our retina specialist to be present on OCT, we took this as a true positive in all cases. Future studies may employ additional retina specialists to review all scans to determine whether there is any interprovider variability in scan assessment and thus ascertain diagnostic specificity.
Footnotes
Authors’ Note: The view(s) expressed herein are those of the author(s) and do not reflect the official policy or position of Brooke Army Medical Center, the US Army Institute of Surgical Research, the US Army Medical Department, the US Army Office of the Surgeon General, the Department of the Army, the Department of the Air Force, the Department of Defense, or the US Government.
Ethical Approval: Institutional review board approval was requested, and the board (59th Medical Wing Institutional Review Board, Lackland Air Force Base, San Antonio) approved the study with an exempt status regarding the protection of human subjects. This case report was conducted in accordance with the Declaration of Helsinki. The collection and evaluation of all protected patient health information was performed in a Health Insurance Portability and Accountability Act (HIPAA)—compliant manner.
Statement of Informed Consent: Informed consent was obtained prior to performing the procedure. All patients provided verbal consent.
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.
ORCID iD: Halward M.J. Blegen IV, DO 
https://orcid.org/0000-0001-7480-0076
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