Spectral-Domain and Swept-Source OCT Angiographic Scans Yield Similar Drusen Measurements When Processed with the Same Algorithm

Purpose

An algorithm developed to obtain drusen area and volume measurements using swept-source OCT angiography (SS-OCTA) scans was tested on spectral-domain OCT angiography (SD-OCTA) scans.

Design

Retrospective study.

Participants

Forty pairs of scans from 27 eyes with intermediate age-related macular degeneration and drusen.

Methods

Patients underwent both SD-OCTA and SS-OCTA imaging at the same visit using the 6 mm × 6 mm OCTA scan patterns. Using the same algorithm, we obtained drusen area and volume measurements within both 3 mm and 5 mm fovea-centered circles. Paired 2-sample t-tests were performed along with Pearson's correlation tests.

Main Outcome Measures

Mean square root (sqrt) drusen area and cube root (cbrt) drusen volume within the 3 mm and 5 mm fovea-centered circles.

Results

Mean sqrt drusen area values from SD-OCTA and SS-OCTA scans were 1.57 (standard deviation [SD] 0.57) mm and 1.49 (SD 0.58) mm in the 3 mm circle and 1.88 (SD 0.59) mm and 1.76 (SD 0.58) mm in the 5 mm circle, respectively. Mean cbrt drusen volume measurements were 0.54 (SD 0.19) mm and 0.51 (SD 0.20) mm in the 3 mm circle, and 0.60 (SD 0.17) mm and 0.57 (SD 0.17) mm in the 5 mm circle. Small differences in area and volume measurements were found (all P < 0.001); however, the correlations between the instruments were strong (all coefficients > 0.97; all P < 0.001).

Conclusions

An algorithm originally developed for SS-OCTA scans performs well when used to obtain drusen volume and area measurements from SD-OCTA scans; thus, a separate SD-OCT structural scan is unnecessary to obtain measurements of drusen.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Rediscovering AMD with Swept-Source OCT Imaging: The 2022 Charles L. Schepens, MD, Lecture

PURPOSE

Swept-source optical coherence tomography angiography (SS-OCTA) scans of eyes with age-related macular degeneration (AMD) were used to replace color, autofluorescence, infrared reflectance, and dye-based fundus angiographic imaging for the diagnosis and staging of AMD. Through the use of different algorithms with the SS-OCTA scans, both structural and angiographic information can be viewed and assessed using both cross-sectional and en face imaging strategies.

DESIGN

Presented at the 2022 Charles L. Schepens, MD, Lecture at the American Academy of Ophthalmology Retina Subspecialty Day, Chicago, Illinois, on September 30, 2022 PARTICIPANTS: Patients with AMD METHODS: Review of published literature and ongoing clinical research using SS-OCTA imaging in AMD.

MAIN OUTCOME MEASURES

SS-OCTA imaging of AMD at different stages of disease progression.

RESULTS

Volumetric SS-OCTA dense raster scans were used to diagnose and stage both exudative and nonexudative AMD. In eyes with nonexudative AMD, a single SS-OCTA scan was used to detect and measure structural features in the macula such as the area and volume of both typical soft drusen and calcified drusen, the presence and location of hyperreflective foci, the presence of reticular pseudodrusen, also known as subretinal drusenoid deposits, the thickness of the outer retinal layer, the presence and thickness of basal laminar deposits, the presence and area of persistent choroidal hypertransmission defects, and the presence of treatment-naïve nonexudative macular neovascularization. In eyes with exudative AMD, the same SS-OCTA scan pattern was used to detect and measure the presence of macular fluid, the presence and type of macular neovascularization, and the response of exudation to treatment with vascular endothelial growth factor inhibitors. In addition, the same scan pattern was used to quantitate choriocapillaris (CC) perfusion, CC thickness, choroidal thickness, and the vascularity of the choroid.

CONCLUSIONS

Compared with using several different instruments to perform multimodal imaging, a single SS-OCTA scan provides a convenient, comfortable, and comprehensive approach for obtaining qualitative and quantitative anatomic and angiographic information to monitor the onset, progression, and response to therapies in both nonexudative and exudative AMD.

The Double Layer Sign Is Highly Predictive of Progression to Exudation in Age-Related Macular Degeneration

PURPOSE

The presences of a double layer sign (DLS) and a shallow irregular retinal pigment epithelium (RPE) elevation (SIRE) were investigated using spectral domain-OCT (SD-OCT) imaging to determine their ability to predict progression to exudative macular neovascularization (eMNV) in the unaffected fellow eyes (study eye) of participants with age-related macular degeneration (AMD) with newly diagnosed unilateral eMNV.

DESIGN

Retrospective, reanalysis of SD-OCT scans of study eyes from the Early Detection of Neovascular AMD (EDNA) study with 3 years follow-up (FU).

PARTICIPANTS

The EDNA study repository of SD-OCT scans was assessed for inclusion. Cases with incomplete data sets, low quality scans, or exhibiting other pathology were excluded, which resulted in 459 eligible cases.

METHODS

Spectral domain-OCT volume scans of study eyes were graded for irregular elevation of the RPE (IE), with length, and height measurements made on the most affected B-scan. Eyes with heterogeneous reflectivity within the IE were classified as exhibiting the DLS. Eyes with DLS where the length of separation between RPE and Bruch's membrane was ≥ 1000 μm in length and < 100 μm in height were subclassified as SIRE.

MAIN OUTCOME MEASURES

Hazard of progression to eMNV for DLS and SIRE.

RESULTS

Of the 459 eyes, 268 had IE, of which 101 were DLS-like and 51 also fulfilled criteria for SIRE. Over the 3 years FU period, 104 (23%) eyes progressed to eMNV. After an FU of 18 months, a significantly higher proportion of study eyes (P < 0.001) with IE, DLS, and SIRE developed eMNV compared with those without these features (IE: 17% vs. no IE 6.3%; DLS: 23% vs. no DLS 9.9%; SIRE: 22% vs. no SIRE 11%). In the adjusted Cox regression models, a significantly greater hazard of progression (P < 0.001) was associated with the presence of IE (adjusted hazard ratio [HR], 3.01; 95% confidence interval [CI], 1.88-4.82), DLS (adjusted HR, 3.41; 95% CI, 2.26-5.14), or SIRE (adjusted HR, 2.83; 95% CI, 1.68-4.75).

CONCLUSION

The DLS is a highly sensitive predictor of progression to eMNV, and the use of SIRE does not improve predictability.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Subretinal drusenoid deposits, age-related macular degeneration, and cardiovascular disease

Decades of studies on age-related macular degeneration (AMD), cardiovascular disease and stroke have not found consistent associations between AMD and systemic vascular disease. This study suggests that there is in fact no general relationship, but instead a strong, specific association between only the subretinal drusenoid deposit (SDD) phenotype of AMD on retinal imaging and certain co-existent vascular diseases that are high risk for compromised cardiac output or internal carotid artery stenosis. Future screening initiatives for these high -risk vascular diseases (HRVDs) with fast, inexpensive retinal imaging could make a significant contribution to public health and save lives. Likewise, screening patients with known HRVDs for unrecognized AMD of the SDD form could enable needed treatment and save vision.

Deep-learning-based automated measurement of outer retinal layer thickness for use in the assessment of age-related macular degeneration, applicable to both swept-source and spectral-domain OCT imaging

Effective biomarkers are required for assessing the progression of age-related macular degeneration (AMD), a prevalent and progressive eye disease. This paper presents a deep learning-based automated algorithm, applicable to both swept-source OCT (SS-OCT) and spectral-domain OCT (SD-OCT) scans, for measuring outer retinal layer (ORL) thickness as a surrogate biomarker for outer retinal degeneration, e.g., photoreceptor disruption, to assess AMD progression. The algorithm was developed based on a modified TransUNet model with clinically annotated retinal features manifested in the progression of AMD. The algorithm demonstrates a high accuracy with an intersection of union (IoU) of 0.9698 in the testing dataset for segmenting ORL using both SS-OCT and SD-OCT datasets. The robustness and applicability of the algorithm are indicated by strong correlation (r = 0.9551, P < 0.0001 in the central-fovea 3 mm-circle, and r = 0.9442, P < 0.0001 in the 5 mm-circle) and agreement (the mean bias = 0.5440 um in the 3-mm circle, and 1.392 um in the 5-mm circle) of the ORL thickness measurements between SS-OCT and SD-OCT scans. Comparative analysis reveals significant differences (P < 0.0001) in ORL thickness among 80 normal eyes, 30 intermediate AMD eyes with reticular pseudodrusen, 49 intermediate AMD eyes with drusen, and 40 late AMD eyes with geographic atrophy, highlighting its potential as an independent biomarker for predicting AMD progression. The findings provide valuable insights into the ORL alterations associated with different stages of AMD and emphasize the potential of ORL thickness as a sensitive indicator of AMD severity and progression.

Influence of Carotid Endarterectomy on Choroidal Perfusion: The INFLATE Study

PURPOSE

Patients with clinically significant carotid artery stenosis (CAS) undergoing carotid artery endarterectomy (CEA) were imaged with swept-source OCT angiography (SS-OCTA) imaging protocol to determine if there were changes in choroidal blood flow after surgery.

DESIGN

Prospective observational study.

PARTICIPANTS

Patients with clinically significant CAS undergoing unilateral CEA.

METHODS

All participants underwent SS-OCTA imaging using a 6 × 6-mm scan pattern on both eyes before CEA and within 1 week after CEA. Previously validated automated algorithms were used to measure the mean choroidal thickness (MCT) and choroidal vascular index (CVI) within 2.5-mm and 5-mm circles centered on the fovea. Multivariable regression analysis was conducted to evaluate the impact of various baseline factors including age, mean arterial blood pressure, and degree of stenosis, on both baseline of MCT and CVI, and the changes in MCT and CVI.

MAIN OUTCOME MEASURES

Changes in MCT and CVI.

RESULTS

One hundred sixteen eyes from 60 patients with a mean age of 71.57 ± 7.37 years were involved in the study. At baseline, MCT in both the 2.5-mm and 5-mm circles was significantly thinner on the surgical side compared with the nonsurgical side (P = 0.03), while no significant differences were seen in the CVI at baseline between the 2 sides (2.5-mm circle: P = 0.24; 5-mm circle: P = 0.09). Within 1 week after CEA, there were significant increases in the MCT on the surgical side, as compared with the nonsurgical side, in both the 2.5-mm (P < 0.001) and the 5-mm (P < 0.001) circles. No significant change in mean CVI was noted before and after CEA on the surgical side versus the nonsurgical side (2.5-mm circle: P = 0.30; 5-mm circle: P = 0.97). Multivariable regression analysis revealed that baseline MCT before CEA significantly decreased with age on both the surgical (P < 0.001) and nonsurgical sides (P = 0.003) while the changes in MCT and CVI after CEA were not associated with age, mean arterial blood pressure, or degree of stenosis.

CONCLUSION

A rapid and significant increase in MCT was observed on the ipsilateral side of CEA, suggesting an improvement in choroidal perfusion within 1 week after surgery.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Assessing Change in Exudative Age-Related Macular Degeneration With Macular Thickness Maps as a Surrogate Strategy for Remote Patient Monitoring

PURPOSE

To determine if macular thickness maps (MTMs) are sufficient to guide management of eyes with exudative age-related macular degeneration (eAMD), we compared the ability to detect change using MTMs with the ability to detect change using the entire optical coherence tomography (OCT) scan in patients undergoing therapy.

DESIGN

Retrospective, comparative diagnostic analysis.

METHODS

Patients with eAMD were imaged using macula-centered 6 × 6-mm OCT scans (CIRRUS HD-OCT 5000; Zeiss). In each case, graders were asked to determine if there were changes that warranted a full clinical assessment after viewing 2 consecutive scans using one of 3 different imaging strategies: MTMs alone, individual foveal-centered B scans alone, or 5 macular B scans including the foveal-centered B scan. Graders were told the 2 scans were taken 2 weeks apart. The consensus ground truth was reached by the graders using a CIRRUS review station to evaluate all the information contained within the OCT scans.

RESULTS

A total of 53 eyes were included in this study with 1385 imaging sessions. The Fleiss kappa was highest when graders were given MTMs alone compared with the ground truth. When the averages of all 5 graders were compared with the ground truth, the MTMs alone showed the highest level of agreement (90.05%, SD 0.78%) followed by the central B scans (87.87%, SD 1.59%) and the 5-B scan method (86.512%, SD 0.64%).

CONCLUSION

MTMs alone provide sufficient information to easily identify recurrent exudation in patients with eAMD, and these maps may be all that is needed for remote monitoring.

The Impact of Carotid Endarterectomy on Choriocapillaris Perfusion

Purpose

The impact of carotid endarterectomy (CEA) on choriocapillaris (CC) perfusion was investigated using swept-source optical coherence tomography angiography (SS-OCTA) imaging before and after surgery in patients with clinically significant carotid artery stenosis (CAS).

Methods

In this prospective observational study, patients with clinically significant CAS undergoing unilateral CEA had SS-OCTA imaging performed in both eyes before and within 1 week after surgery. The percent CC flow deficits (CC FD%) and CC thickness were assessed using previously validated algorithms. Multivariable regression analysis was conducted to evaluate the impact of variables on the change in CC measurements.

Results

A total of 112 eyes from 56 patients with an average age of 72.6 ± 6.9 years were enrolled. At baseline, significantly higher CC FD% and thinner CC thickness were observed on the surgical side (eyes ipsilateral to the side of CEA) versus the nonsurgical side (eyes contralateral to the side of CEA) (P = 0.001 and P = 0.03, respectively). Following CEA, a significant reduction in CC FD% and a significant increase in CC thickness were detected on the surgical as compared with the nonsurgical side (P = 0.008 and P = 0.01, respectively). Smoking status positively affected CC FD% change (coefficient of variation [CV] = 0.84, P = 0.01) on the surgical side and negatively affected CC thickness change on both the surgical side (CV = -0.382, P = 0.009) and the nonsurgical side (CV = -0.321, P = 0.04). The degree of stenosis demonstrated a positive influence on CC FD% change (CV = 0.040, P = 0.02) on the surgical side.

Conclusions

Unilateral CEA on the side of clinically significant CAS increases carotid blood flow, which further results in improved CC perfusion.

Comparison between B-Scan and En Face Images for Incomplete and Complete Retinal Pigment Epithelium and Outer Retinal Atrophy

PURPOSE

To evaluate and compare the detection of incomplete retinal pigment epithelium and outer retinal atrophy (iRORA) and complete retinal pigment epithelium and outer retinal atrophy (cRORA) assessed on OCT B-scans versus persistent choroidal hypertransmission defects (hyperTDs) assessed by en face choroidal OCT images.

DESIGN

Retrospective, cross-sectional study.

PARTICIPANTS

Patients with late atrophic age-related macular degeneration imaged on the same day using both Spectralis OCT and Cirrus OCT.

MAIN OUTCOME MEASURE

Agreement between the B-scan and en face OCT for the detection of hyperTDs, cRORA, and iRORA.

METHODS

Two independent graders examined en face OCT and structural OCT to determine the presence and location of hyperTDs, iRORA, and cRORA.

RESULTS

A total of 239 iRORA and cRORA lesions were detected on the B-scans, and 249 hyperTD lesions were identified on the en face OCT images. There was no significant difference (P = 0.88) in the number of lesions. There was no significant difference in the 134 cRORA lesions identified on B-scans and the 131 hyperTDs detected on en face OCT images (P = 0.13). A total of 105 iRORA lesions were identified by B-scan assessment; however, 50 of these iRORA lesions met the criteria for persistent hyperTDs on en face OCT images (P < 0.001). When considering the topographic correspondence between B-scan and en face OCT detected lesions, the mean percentage of agreement between B-scan detection of cRORA lesions with en face OCT detection was 97.6 % (P = 0.13).

CONCLUSIONS

We observed high overall agreement between cRORA lesions identified on B-scans and persistent hyperTDs identified on en face OCT. However, en face imaging was able to detect iRORA lesions that had a greatest linear dimension ≥ 250 μm in a nonhorizontal en face dimension.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Pegcetacoplan for the treatment of geographic atrophy secondary to age-related macular degeneration (OAKS and DERBY): two multicentre, randomised, double-masked, sham-controlled, phase 3 trials

BACKGROUND

Geographic atrophy is a leading cause of progressive, irreversible vision loss. The objectives of OAKS and DERBY were to assess the efficacy and safety of pegcetacoplan compared with sham treatment in patients with geographic atrophy.

METHODS

OAKS and DERBY were two 24-month, multicentre, randomised, double-masked, sham-controlled, phase 3 studies, in which patients aged 60 years and older with geographic atrophy secondary to age-related macular degeneration were enrolled at 110 clinical sites and 122 clinical sites worldwide, respectively. Patients were randomly assigned (2:2:1:1) by central web-based randomisation system to intravitreal 15 mg per 0·1 mL pegcetacoplan monthly or every other month, or sham monthly or every other month using stratified permuted block randomisation (stratified by geographic atrophy lesion area at screening, history or presence of active choroidal neovascularisation in the eye not under assessment, and block size of six). Study site staff, patients, reading centre personnel, evaluating physicians, and the funder were masked to group assignment. Sham groups were pooled for the analyses. The primary endpoint was the change from baseline to month 12 in the total area of geographic atrophy lesions in the study eye based on fundus autofluorescence imaging, in the modified intention-to-treat population (ie, all patients who received one or more injections of pegcetacoplan or sham and had a baseline and at least one post-baseline value of lesion area). Key secondary endpoints (measured at 24 months) were change in monocular maximum reading speed of the study eye, change from baseline in mean functional reading independence index score, change from baseline in normal luminance best-corrected visual acuity score, and change from baseline in the mean threshold sensitivity of all points in the study eye by mesopic microperimetry (OAKS only). Safety analyses included patients who were randomly assigned and received at least one injection of pegcetacoplan or sham. The now completed studies are registered with ClinicalTrials.gov, NCT03525613 (OAKS) and NCT03525600 (DERBY).

FINDINGS

Between Aug 30, 2018, and July 3, 2020, 1258 patients were enrolled in OAKS and DERBY. The modified intention-to-treat populations comprised 614 (96%) of 637 patients in OAKS (202 receiving pegcetacoplan monthly, 205 pegcetacoplan every other month, and 207 sham) and 597 (96%) of 621 patients in DERBY (201 receiving pegcetacoplan monthly, 201 pegcetacoplan every other month, and 195 sham). In OAKS, pegcetacoplan monthly and pegcetacoplan every other month significantly slowed geographic atrophy lesion growth by 21% (absolute difference in least-squares mean -0·41 mm2, 95% CI -0·64 to -0·18; p=0·0004) and 16% (-0·32 mm2, -0·54 to -0·09; p=0·0055), respectively, compared with sham at 12 months. In DERBY, pegcetacoplan monthly and pegcetacoplan every other month slowed geographic atrophy lesion growth, although it did not reach significance, by 12% (-0·23 mm2, -0·47 to 0·01; p=0·062) and 11% (-0·21 mm2, -0·44 to 0·03; p=0·085), respectively, compared with sham at 12 months. At 24 months, pegcetacoplan monthly and pegcetacoplan every other month slowed geographic atrophy lesion growth by 22% (-0·90 mm2, -1·30 to -0·50; p<0·0001) and 18% (-0·74 mm2, -1·13 to -0·36; p=0·0002) in OAKS, and by 19% (-0·75 mm2, -1·15 to -0·34; p=0·0004) and 16% (-0·63 mm2, -1·05 to -0·22; p=0·0030) in DERBY, respectively, compared with sham. There were no differences in key secondary visual function endpoints at 24 months. Serious ocular treatment-emergent adverse events were reported in five (2%) of 213, four (2%) of 212, and one (<1%) of 211 patients in OAKS, and in four (2%) of 206, two (1%) of 208, and two (1%) of 206 patients in DERBY receiving pegcetacoplan monthly, pegcetacoplan every other month, and sham, respectively, at 24 months. New-onset exudative age-related macular degeneration was reported in 24 (11%), 16 (8%), and four (2%) patients in OAKS, and in 27 (13%), 12 (6%), and nine (4%) patients in DERBY receiving pegcetacoplan monthly, pegcetacoplan every other month, and sham, respectively, at 24 months.

INTERPRETATION

Pegcetacoplan, the first treatment approved by the US Food and Drug Administration for geographic atrophy, slowed geographic atrophy lesion growth with an acceptable safety profile.

FUNDING

Apellis Pharmaceuticals.

Choroidal Changes After Anti-VEGF Therapy in AMD Eyes With Different Types of Macular Neovascularization Using Swept-Source OCT Angiography

Purpose

Choroidal changes before and after anti-VEGF therapy were investigated in eyes with exudative AMD to determine if there was a difference between eyes with macular neovascularization (MNV) that arises from the choroid (type 1 or 2) versus the retinal circulation (type 3).

Methods

Patients with treatment-naïve AMD were imaged with swept-source optical coherence tomography angiography using a 12 × 12-mm scan pattern. The mean choroidal thickness and choroidal vascularity index (CVI) were measured within 5-mm and 11-mm fovea-centered circles before, at the onset of, and after anti-VEGF therapy.

Results

Forty-one eyes of 37 patients were included; 24 eyes with type 1 MNV, 4 eyes with type 2 MNV, and 13 eyes with type 3 MNV. Within the 5-mm and 11-mm circles, the mean choroidal thickness and CVI measurements increased from pretreatment to the onset of exudation (P ≤ 0.03). The mean choroidal thickness and CVI measurements decreased from the onset of exudation to after treatment (P < 0.001). No significant changes in mean choroidal thickness or CVI were observed when comparing measurements before or after treatment (P ≥ 0.38). No significant differences in mean choroidal thickness or CVI measurements were observed between eyes with type 1 or 2 MNV and type 3 MNV.

Conclusions

In treatment-naïve AMD eyes with MNV, the choroidal thickness and vascularity increased at the onset of exudation and then decreased after anti-VEGF therapy. This finding suggests that these choroidal changes develop in response to the proangiogenic milieu before treatment and in response to treatment, regardless of the site of origin for the MNV.

Onset and Progression of Persistent Choroidal Hypertransmission Defects in Intermediate Age-Related Macular Degeneration: A Novel Clinical Trial Endpoint

PURPOSE

The appearance and growth of persistent choroidal hypertransmission defects (hyperTDs) detected on en face swept-source optical coherence tomography (SS-OCT) images from eyes with intermediate age-related macular degeneration (iAMD) were studied to determine if they could serve as novel clinical trial endpoints.

DESIGN

Post hoc subgroup analysis of a prospective study.

METHODS

Subjects with iAMD underwent 6 × 6 mm SS-OCT angiography imaging at their baseline and follow-up visits. The drusen volumes were obtained using a validated SS-OCT algorithm. Two graders independently evaluated all en face structural images for the presence of persistent hyperTDs. The number and area of all hyperTDs along with drusen volume were obtained from all SS-OCT angiography scans. Eyes were censored from further follow-up once exudative AMD developed.

RESULTS

A total of 171 eyes from 121 patients with iAMD were included. Sixty-eight eyes developed at least 1 hyperTD. Within 1 year after developing a hyperTD, 25% of eyes developed new hyperTDs for an average of 0.44 additional hyperTDs. Over 2 years, as hyperTDs appeared, enlarged, and merged, the average area growth rate was 0.220 mm/yr using the square-root transformation strategy. A clinical trial design using the onset and enlargement of these hyperTDs for the study of disease progression in eyes with iAMD is proposed.

CONCLUSIONS

The appearance and growth of persistent choroidal hyperTDs in eyes with iAMD can be easily detected and measured using en face OCT imaging and can serve as novel clinical trial endpoints for the study of therapies that may slow disease progression from iAMD to late AMD.

INTRAOCULAR INFLAMMATION INCIDENCE AFTER INTRAVITREAL BROLUCIZUMAB INJECTION FOR EXUDATIVE AGE-RELATED MACULAR DEGENERATION

PURPOSE

We evaluated the clinical outcomes of intraocular inflammation (IOI) of eyes with neovascular age-related macular degeneration (AMD) injected with brolucizumab in our tertiary referral center.

METHODS

A retrospective case series for which clinical records of all eyes that received intravitreal brolucizumab at Bascom Palmer Eye Institute between December 1, 2019, and April 1, 2021, were reviewed.

RESULTS

There were 345 eyes of 278 patients who received 801 brolucizumab injections. IOI was detected in 16 eyes of 13 patients (4.6%). In those patients, baseline Logarithm of Minimu Angle of Resolution (logMAR) best-corrected visual acuity was 0.32 0.2 (20/42), while it was 0.58 0.3 (20/76) at IOI presentation. The mean number of injections among eyes experiencing IOI was 2.4, and the interval between the last brolucizumab injection and IOI presentation was 20 days. There was no known case of retinal vasculitis. Management of IOI included topical steroids in seven eyes (54%), topical and systemic steroids in five eyes (38%), and observation in one eye (8%). Best-corrected visual acuity returned to baseline and inflammation resolved in all eyes by the last follow-up examination.

CONCLUSION

Intraocular inflammation after brolucizumab injection for neovascular AMD was not uncommon. Inflammation resolved in all eyes by the last follow-up visit.

Decreased Central Macular Choriocapillaris Perfusion Correlates With Increased Low Luminance Visual Acuity Deficits

PURPOSE

Correlations between low luminance visual acuity deficits (LLVADs) and central choriocapillaris perfusion deficits were investigated to help explain how increases in LLVAD scores at baseline predict annual growth rates of geographic atrophy (GA).

DESIGN

Prospective cross-sectional study.

METHODS

Photopic luminance best-corrected visual acuity (PL-BCVA) and low luminance BCVA (LL-BCVA) were measured using the Early Treatment Diabetic Retinopathy Study chart. LL-BCVA was measured using a 2.0-log unit neutral density filter. LLVADs were calculated as the difference between PL-BCVA and LL-BCVA. Within a fovea-centered 1-mm circle, the percentage of choriocapillaris flow deficits (CC FD%), drusen volume, optical attenuation coefficient (OAC) elevation volume, and outer retinal layer (ORL) thickness were assessed.

RESULTS

In all 90 eyes (30 normal eyes; 31 drusen-only eyes; 29 non-foveal GA eyes), significant correlations were found between the central CC FD% and PL-BCVA (r = -0.393, P < .001), LL-BCVA (r = -0.534, P < .001), and the LLVAD (r = 0.439, P < .001). Central cube root (cubrt) drusen volume, cubrt OAC elevation volume, and ORL thickness were correlated with PL-BCVA, LL-BCVA, and LLVADs (all P < .05). Stepwise regression models showed that central cubrt OAC elevation volume and ORL thickness were associated with PL-BCVA (R2 = 0.24, P < .05); central CC FD%, cubrt OAC elevation volume, and ORL thickness were associated with LL-BCVA (R2 = 0.44, P < .01); and central CC FD% and ORL thickness were associated with LLVAD (R2 = 0.24, P < .01).

CONCLUSIONS

The significant correlations between central CC FD% and LLVAD support the hypothesis that the ability of LLVAD to predict the growth of GA is mediated through a decrease in macular choriocapillaris perfusion.

Unleashing the power of optical attenuation coefficients to facilitate segmentation strategies in OCT imaging of age-related macular degeneration: perspective

The use of optical attenuation coefficients (OAC) in optical coherence tomography (OCT) imaging of the retina has improved the segmentation of anatomic layers compared with traditional intensity-based algorithms. Optical attenuation correction has improved our ability to measure the choroidal thickness and choroidal vascularity index using dense volume scans. Algorithms that combine conventional intensity-based segmentation with depth-resolved OAC OCT imaging have been used to detect elevations of the retinal pigment epithelium (RPE) due to drusen and basal laminar deposits, the location of hyperpigmentation within the retina and along the RPE, the identification of macular atrophy, the thickness of the outer retinal (photoreceptor) layer, and the presence of calcified drusen. OAC OCT algorithms can identify the risk-factors that predict disease progression in age-related macular degeneration.

Symmetry of Macular Fundus Features in Age-Related Macular Degeneration

PURPOSE

The symmetry of major macular fundus features in both eyes of the same patient with age-related macular degeneration (AMD) was investigated using swept-source(SS)-OCT.

DESIGN

Retrospective review of a prospective study.

PARTICIPANTS

Patients with AMD.

METHODS

Grading was performed on the first SS-OCT images obtained on the patients. Two graders diagnosed the presence of drusen, geographic atrophy (GA), and exudative AMD (eAMD) in each eye. Medical records were reviewed to assess prior exudation. To assess symmetry, 1 eye of each patient was randomly selected as the index eye and compared with the fellow eye. The kappa statistic (κ) was used to assess the symmetry of diagnosis. The intraclass correlation coefficient (ICC) was used to assess the symmetry of drusen area and volume.

MAIN OUTCOME MEASURES

Interocular symmetry of the AMD stages: drusen, GA, and eAMD.

RESULTS

A total of 1310 patients with AMD were included. The average age was 78 years (range, 50-102; 60% women). Of the 1310 subjects, 54% (701) presented with symmetric disease: 20% with bilateral drusen, 11% with bilateral GA, and 22% with bilateral eAMD. Only 0.5% of the subjects had both GA and eAMD in both eyes. Of the randomly selected index eyes, 825 (47%) were right eyes. Overall, limited interocular agreement was observed between the index and fellow eyes (54%; κ = 0.29). Kappa coefficients were poor (< 0.4) for index eyes diagnosed with drusen (κ = 0.27), eAMD (κ = 0.17), and mixed disease (κ = 0.03). There was moderate agreement between the index and fellow eyes for GA (κ = 0.50). Of the 265 patients with bilateral drusen, the symmetry of drusen area measurements had moderate ICC values of 0.70, 0.71, and 0.70 in the 3- and 5-mm diameter foveal-centered circles and in the total scan area, respectively. The ICC values for the drusen volumes were 0.65, 0.66, and 0.64, respectively.

CONCLUSIONS

Interocular symmetry was poor for eyes with drusen, eAMD, and mixed disease, but moderate for GA. Although the diagnosis of drusen was not very symmetric between eyes, when present in both eyes, the drusen area and volume measurements were moderately symmetric.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

The Impact of Cataracts on the Measurement of Macular Choriocapillaris Flow Deficits Using Swept-Source OCT Angiography

Purpose

The impact of cataracts on the measurement of macular choriocapillaris flow deficits (CC FDs) was assessed by comparing the quantitative results before and after cataract surgery using an image quality algorithm developed for swept-source optical coherence tomography angiography (SS-OCTA) scans and a validated strategy for quantifying the CC FDs.

Methods

SS-OCTA image quality scores and CC FDs measurements within the fovea-centered 1-mm, 3-mm, and 5-mm diameter circles were compared before and after cataract surgery. CC FDs changes in a modified Early Treatment Diabetic Retinopathy Study (ETDRS) grid were further investigated.

Results

Twenty-four eyes were studied. Overall image quality in all three circles was observed to improve significantly following the removal of cataracts (all P < 0.05). Although there was good repeatability in the measurements of CC FDs at both visits (intraclass correlation coefficients were over 0.95), significant decreases in CC FD measurements were observed after surgery within the 1-mm circle (P < 0.001) and the 3-mm circle (P = 0.011), but no changes were observed within the 5-mm circle (P = 0.509) or any of the quadrant sectors of the modified ETDRS grid (all P > 0.05).

Conclusions

The presence of cataracts resulted in worse image quality and increased CC FD measurements within the fovea-centered 1-mm and 3-mm circles, with the 1-mm circle being impacted the most.

Translational Relevance

The impaired detection of CC perfusion deficits within the central macula of cataract eyes needs to be appreciated when imaging the CC in phakic eyes, especially in clinical trials.

Longitudinal quantification of choriocapillaris flow deficits in persistent placoid maculopathy: a case report

BACKGROUND

Persistent placoid maculopathy (PPM) is a rare idiopathic chorioretinopathy characterized by choriocapillaris (CC) hypoperfusion. In a case of PPM, we quantified CC flow deficits (FDs) over time and observed an increase in CC perfusion as the visual acuity and outer photoreceptor anatomy improved.

CASE PRESENTATION

A 58-year-old man was diagnosed with PPM in both eyes based on the patient's clinical presentation and imaging. He presented with sudden-onset central scotomas in both eyes for about two months. On referral, the best corrected visual acuity (BCVA) was 20/20 in the right eye and 20/100 in the left eye. Plaque-like yellowish macular lesions were observed bilaterally and autofluorescence imaging showed bilateral hyperautofluorescent lesions. Fluorescein angiography (FA) revealed early-phase hyper-fluorescent staining that intensified in the late phases, while indocyanine green angiography (ICGA) displayed persistent hypofluorescence in both eyes. Foveal centered swept source optical coherence tomography (SS-OCT) B-scans showed bilateral focal deposits on the level of retinal pigment epithelium (RPE) and disruption of outer photoreceptor bands. The CC FDs were quantified on SS-OCT angiography (SS-OCTA) images using a previously published algorithm that was validated. The CC FD% was 12.52% in the right eye and 14.64% in the left eye within a 5 mm circle centered on the fovea. After 5 months of steroid treatment, BCVA remained 20/20 in the right eye and improved to 20/25 in the left eye. On OCT imaging, the outer photoreceptor bands fully recovered in both eyes, while some focal deposits remained along the RPE in the left eye. The CC perfusion in both eyes improved, with CC FD% decreasing from 12.52% to 9.16% in the right eye and from 14.64% to 9.34% in the left eye.

CONCLUSIONS

Significant impairment of macular CC perfusion was detected after the onset of PPM. Improvement in central macular CC perfusion corresponded with improvements in BCVA and outer retinal anatomy. Our findings suggest that imaging and quantification of CC FDs could serve as a valuable imaging strategy for diagnosing PPM and for following disease progression.

Decreased Macular Choriocapillaris Perfusion in Eyes With Macular Reticular Pseudodrusen Imaged With Swept-Source OCT Angiography

Purpose

To determine if macular reticular pseudodrusen (RPD) were associated with markers of impaired macular choroidal perfusion, we investigated measurements of macular choriocapillaris (CC) flow deficits (FDs), CC thickness, and mean choroidal thickness (MCT) in eyes with macular RPD compared with normal eyes and eyes with soft drusen.

Methods

Eyes with intermediate age-related macular degeneration (iAMD) and normal eyes underwent 6 × 6 mm swept-source optical coherence tomography angiography (SS-OCTA) imaging to diagnose macular RPD, occupying over 25% of the fovea-centered 5 mm diameter circle, and measure outer retinal layer (ORL) thickness, CC FDs, CC thickness, MCT, and choroidal vascularity index (CVI) using previously published strategies within the same fovea-centered 5 mm circle.

Results

Ninety eyes were included; 30 normal eyes, 30 eyes with soft drusen, and 30 eyes with macular RPD. The RPD eyes showed higher macular CC FDs than normal eyes (P < 0.001) and soft drusen eyes (P = 0.019). Macular CC thickness was decreased in RPD eyes compared with normal eyes (P < 0.001) and soft drusen eyes (P = 0.016). Macular MCT in RPD eyes was thinner than normal eyes (P = 0.005) and soft drusen eyes (P < 0.001). No statistically and clinically significant differences were found in the ORL thickness and CVI measurements between RPD eyes and the other two groups (all P > 0.05).

Conclusions

Eyes with macular RPD had decreased macular CC perfusion, decreased CC thickness, and decreased MCT measurements compared with normal and soft drusen eyes, suggesting that RPD may result from impaired choroidal perfusion.

Identification of macular neovascularization in central serous chorioretinopathy using swept-source OCT angiography

Purpose

Swept-source optical coherence tomography angiography (SS-OCTA) was used to detect the presence of macular neovascularization (MNV) in eyes with exudative central serous chorioretinopathy (CSCR).

Observations

Case 1 is a 73-year-old man using prednisolone drops with 20/40 vision and a retinal pigment epithelial detachment (PED) associated with subretinal fluid (SRF) and no clinical signs of age-related macular degeneration (AMD) in his left eye. Three months after presentation he underwent SS-OCTA imaging that revealed MNV. He received a series of intravitreal anti-vascular endothelial growth factor (VEGF) injections and SS-OCTA imaging showed a decrease in the MNV lesion size with resolution of the SRF. VA improved to 20/25. Case 2 is a 65-year-old man with recent oral steroid use, presenting with 20/20 vision, a PED, SRF, and no evidence of AMD. SS-OCTA imaging at presentation revealed MNV, which worsened on interval SS-OCTA imaging after the patient deferred treatment. Intravitreal anti-VEGF therapy was then performed with resolution of the SRF and VA improved to 20/15. A total of six cases of type 1 MNV were diagnosed with CSCR. Most were men with a history of steroid or testosterone use and were treated with good response.

Conclusions and importance

SS-OCTA imaging provides a convenient non-invasive strategy for identifying CSCR eyes with MNV without the need for dye-based angiography.

Clinicopathologic Findings in Three Siblings With Geographic Atrophy

Purpose

Age-related macular degeneration (AMD) is a leading cause of blindness among the elderly worldwide. Clinical imaging and histopathologic studies are crucial to understanding disease pathology. This study combined clinical observations of three brothers with geographic atrophy (GA), followed for 20 years, with histopathologic analysis.

Methods

For two of the three brothers, clinical images were taken in 2016, 2 years prior to death. Immunohistochemistry, on both flat-mounts and cross sections, histology, and transmission electron microscopy were used to compare the choroid and retina in GA eyes to those of age-matched controls.

Results

Ulex europaeus agglutinin (UEA) lectin staining of the choroid demonstrated a significant reduction in the percent vascular area and vessel diameter. In one donor, histopathologic analysis demonstrated two separate areas with choroidal neovascularization (CNV). Reevaluation of swept-source optical coherence tomography angiography (SS-OCTA) images revealed CNV in two of the brothers. UEA lectin also revealed a significant reduction in retinal vasculature in the atrophic area. A subretinal glial membrane, composed of processes positive for glial fibrillary acidic protein and/or vimentin, occupied areas identical to those of retinal pigment epithelium (RPE) and choroidal atrophy in all three AMD donors. SS-OCTA also demonstrated presumed calcific drusen in the two donors imaged in 2016. Immunohistochemical analysis and alizarin red S staining verified calcium within drusen, which was ensheathed by glial processes.

Conclusions

This study demonstrates the importance of clinicohistopathologic correlation studies. It emphasizes the need to better understand how the symbiotic relationship between choriocapillaris and RPE, glial response, and calcified drusen impact GA progression.

Automated segmentation and quantification of calcified drusen in 3D swept source OCT imaging

Qualitative and quantitative assessments of calcified drusen are clinically important for determining the risk of disease progression in age-related macular degeneration (AMD). This paper reports the development of an automated algorithm to segment and quantify calcified drusen on swept-source optical coherence tomography (SS-OCT) images. The algorithm leverages the higher scattering property of calcified drusen compared with soft drusen. Calcified drusen have a higher optical attenuation coefficient (OAC), which results in a choroidal hypotransmission defect (hypoTD) below the calcified drusen. We show that it is possible to automatically segment calcified drusen from 3D SS-OCT scans by combining the OAC within drusen and the hypoTDs under drusen. We also propose a correction method for the segmentation of the retina pigment epithelium (RPE) overlying calcified drusen by automatically correcting the RPE by an amount of the OAC peak width along each A-line, leading to more accurate segmentation and quantification of drusen in general, and the calcified drusen in particular. A total of 29 eyes with nonexudative AMD and calcified drusen imaged with SS-OCT using the 6 × 6 mm² scanning pattern were used in this study to test the performance of the proposed automated method. We demonstrated that the method achieved good agreement with the human expert graders in identifying the area of calcified drusen (Dice similarity coefficient: 68.27 ± 11.09%, correlation coefficient of the area measurements: r = 0.9422, the mean bias of the area measurements = 0.04781 mm²).

A Deep Learning Model for Automated Segmentation of Geographic Atrophy Imaged Using Swept-Source OCT

PURPOSE

To present a deep learning algorithm for segmentation of geographic atrophy (GA) using en face swept-source OCT (SS-OCT) images that is accurate and reproducible for the assessment of GA growth over time.

DESIGN

Retrospective review of images obtained as part of a prospective natural history study.

SUBJECTS

Patients with GA (n = 90), patients with early or intermediate age-related macular degeneration (n = 32), and healthy controls (n = 16).

METHODS

An automated algorithm using scan volume data to generate 3 image inputs characterizing the main OCT features of GA-hypertransmission in subretinal pigment epithelium (sub-RPE) slab, regions of RPE loss, and loss of retinal thickness-was trained using 126 images (93 with GA and 33 without GA, from the same number of eyes) using a fivefold cross-validation method and data augmentation techniques. It was tested in an independent set of one hundred eighty 6 × 6-mm² macular SS-OCT scans consisting of 3 repeated scans of 30 eyes with GA at baseline and follow-up as well as 45 images obtained from 42 eyes without GA.

MAIN OUTCOME MEASURES

The GA area, enlargement rate of GA area, square root of GA area, and square root of the enlargement rate of GA area measurements were calculated using the automated algorithm and compared with ground truth calculations performed by 2 manual graders. The repeatability of these measurements was determined using intraclass coefficients (ICCs).

RESULTS

There were no significant differences in the GA areas, enlargement rates of GA area, square roots of GA area, and square roots of the enlargement rates of GA area between the graders and the automated algorithm. The algorithm showed high repeatability, with ICCs of 0.99 and 0.94 for the GA area measurements and the enlargement rates of GA area, respectively. The repeatability limit for the GA area measurements made by grader 1, grader 2, and the automated algorithm was 0.28, 0.33, and 0.92 mm², respectively.

CONCLUSIONS

When compared with manual methods, this proposed deep learning-based automated algorithm for GA segmentation using en face SS-OCT images was able to accurately delineate GA and produce reproducible measurements of the enlargement rates of GA.

Progression of Polypoidal Lesions Associated with Exudative Recurrence in Polypoidal Choroidal Vasculopathy

PURPOSE

To investigate the characteristics of the branching vascular network (BVN) and polypoidal lesions in polypoidal choroidal vasculopathy (PCV) to determine near-term indicators that may predict exudative recurrence.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients with PCV receiving anti-vascular endothelial growth factor (VEGF) monotherapy or anti-VEGF plus photodynamic therapy were followed for at least 1 year using swept-source OCT angiography (SS-OCTA) imaging.

METHODS

Patients were divided into 2 groups based on whether exudative recurrence occurred during follow-up. Multiple parameters were collected and compared between the 2 groups, such as age, gender, visual acuity, number of polypoidal lesions, lesion area at the first SS-OCTA visit, and total lesion area change from the first SS-OCTA visit to the last SS-OCTA visit. To evaluate the association between SS-OCTA imaging-based risk factors and the exudative recurrences, imaging features associated with PCV such as BVN growth and polypoidal lesion progression (enlargement, new appearance, and reappearance) at each follow-up visit were analyzed. The time intervals from the nonexudative visit with lesion progression to the corresponding exudative recurrence visit were documented to explore their association with exudative recurrences. Cox regression and logistic regression analyses were used.

MAIN OUTCOME MEASURES

Association between BVN growth and polypoidal lesion progression with exudative recurrence.

RESULTS

Thirty-one eyes of 31 patients (61% men) were included. Sixteen eyes had no recurrence of exudation, and 15 eyes had recurrence during follow-up. The average follow-up duration was 20.55 ± 6.86 months (range, 12-36 months). Overall, the recurrence group had worse best-corrected visual acuity (P = 0.019) and a greater increase in lesion area (P = 0.010). Logistical regression analysis showed that polypoidal lesion progression, including new appearance, enlargement, and reappearance of polypoidal lesions, was associated with exudative recurrences within 3 months (odds ratio, 26.67, 95% confidence interval, 3.77-188.54, P = 0.001).

CONCLUSIONS

Growth of nonexudative BVN and progression of polypoidal lesions were found to be lesion characteristics associated with exudative recurrences, and progression of polypoidal lesions might serve as a stand-alone indicator for the near-term onset of exudation. In PCV, more frequent follow-up visits are recommended when polypoidal lesions show progression.

Severe retinal hemorrhages at various levels with a serous retinal detachment in a pediatric patient with aplastic anemia-A case report

Background

Aplastic anemia can cause ophthalmic abnormalities in patients. Vision loss in a child with aplastic anemia due to massive retinal hemorrhages at various levels is rare.

Case presentation

A pediatric patient with aplastic anemia presented with retinal hemorrhages at multiple levels along with a serous retinal detachment in both eyes and subsequent retinal changes after pars plana vitrectomy.

Conclusion

Anemia and thrombocytopenia in aplastic anemia could cause severe retinal hemorrhages and result in retinal atrophy and retinal edema. Vitrectomy can be performed to remove vitreous hemorrhage, but risk factors for retinal atrophy and edema need further investigation.

Detection of Nonexudative Macular Neovascularization on Structural OCT Images Using Vision Transformers

PURPOSE

A deep learning model was developed to detect nonexudative macular neovascularization (neMNV) using OCT B-scans.

DESIGN

Retrospective review of a prospective, observational study.

PARTICIPANTS

Normal control eyes and patients with age-related macular degeneration (AMD) with and without neMNV.

METHODS

Swept-source OCT angiography (SS-OCTA) imaging (PLEX Elite 9000, Carl Zeiss Meditec, Inc) was performed using the 6 × 6-mm scan pattern. Individual B-scans were annotated to distinguish between drusen and the double-layer sign (DLS) associated with the neMNV. The machine learning model was tested on a dataset graded by humans, and model performance was compared with the human graders.

MAIN OUTCOME MEASURES

Intersection over Union (IoU) score was measured to evaluate segmentation network performance. Area under the receiver operating characteristic curve values, sensitivity, specificity, and positive predictive value (PPV) and negative predictive value (NPV) were measured to assess the performance of the final classification performance. Chance-corrected agreement between the algorithm and the human grader determinations was measured with Cohen's kappa.

RESULTS

A total of 251 eyes from 210 patients, including 182 eyes with DLS and 115 eyes with drusen, were used for model training. Of 125 500 B-scans, 6879 B-scans were manually annotated. A vision transformer segmentation model was built to extract DLS and drusen from B-scans. The extracted prediction masks from all B-scans in a volume were projected to an en face image, and an eye-level projection map was obtained for each eye. A binary classification algorithm was established to identify eyes with neMNV from the projection map. The algorithm achieved 82%, 90%, 79%, and 91% sensitivity, specificity, PPV, and NPV, respectively, on a separate test set of 100 eyes that were evaluated by human graders in a previous study. The area under the curve value was calculated as 0.91 (95% confidence interval, 0.85-0.98). The results of the algorithm showed excellent agreement with the senior human grader (kappa = 0.83, P < 0.001) and moderate agreement with the junior grader consensus (kappa = 0.54, P < 0.001).

CONCLUSIONS

Our network (code is available at https://github.com/uw-biomedical-ml/double_layer_vit) was able to detect the presence of neMNV from structural B-scans alone by applying a purely transformer-based model.

Does the Outer Retinal Thickness Around Geographic Atrophy Represent Another Clinical Biomarker for Predicting Growth?

PURPOSE

To determine whether the outer retinal layer (ORL) thickness around geographic atrophy (GA) could serve as a clinical biomarker to predict the annual enlargement rate (ER) of GA.

DESIGN

Retrospective analysis of a prospective, observational case series.

METHODS

Eyes with GA were imaged with a swept-source OCT 6 × 6 mm scan pattern. GA lesions were measured from customized en face OCT images and the annual ERs were calculated. The ORL was defined and segmented from the inner boundary of outer plexiform layer (OPL) to the inner boundary of retinal pigment epithelium (RPE) layer. The ORL thickness was measured at different subregions around GA.

RESULTS

A total of 38 eyes from 27 participants were included. The same eyes were used for the choriocapillaris (CC) flow deficit (FD) analysis and the RPE to the Bruch membrane (RPE-BM) distance measurements. A negative correlation was observed between the ORL thickness and the GA growth. The ORL thickness in a 300-μm rim around GA showed the strongest correlation with the GA growth (r = -0.457, P = .004). No correlations were found between the ORL thickness and the CC FDs; however, a significant correlation was found between the ORL thickness and the RPE-BM distances around GA (r = -0.398, P = .013).

CONCLUSIONS

ORL thickness showed a significant negative correlation with annual GA growth, but also showed a significant correlation with the RPE-BM distances, suggesting that they were dependently correlated with GA growth. This finding suggests that the loss of photoreceptors was associated with the formation of basal laminar deposits around GA.

Impact of Reticular Pseudodrusen on Choriocapillaris Flow Deficits and Choroidal Structure on Optical Coherence Tomography Angiography

PURPOSE

To examine the impact of reticular pseudodrusen (RPD) on choriocapillaris blood flow and choroidal structure in individuals with intermediate age-related macular degeneration (AMD).

METHODS

Individuals with bilateral large drusen underwent optical coherence tomography (OCT), color fundus photography, near-infrared reflectance, and fundus autofluorescence imaging to determine the presence of RPD. These participants also underwent swept-source OCT angiography (SS-OCTA) imaging to determine (1) choriocapillaris flow deficit (FD) parameters, including the percentage, mean size, and number of FDs present; and (2) choroidal structural parameters, including mean choroidal thickness and choroidal vascularity index. Differences in these parameters between eyes with and without coexistent RPD were examined with and without adjustment for potential key confounders such as drusen volume from the SS-OCTA scans and age.

RESULTS

This study included 102 eyes from 51 individuals with bilateral large drusen, and the analyses showed that there were no significant differences in the choriocapillaris FD parameters (P ≥ 0.062 for all) and choroidal structural parameters (P ≥ 0.059 for all), with or without adjustment for potential confounders in this cohort. However, the percentage of FDs and the mean FD size were both significantly greater with increasing drusen volume (P ≤ 0.038 for both).

CONCLUSIONS

The coexistence of RPD in eyes of individuals with intermediate AMD was not associated with significant impairments in choriocapillaris blood flow and choroidal vascular structural changes, with or without adjustment for key confounders. These findings suggest that macular changes in these vascular parameters may not be associated with the presence of RPD.

Impact of Cataract Surgery on Low Luminance Visual Acuity Deficit Measurements

Purpose

The impact of cataract surgery on low luminance visual acuity deficit (LLVAD) measurements was investigated by measuring the LLVAD before and after cataract surgery.

Design

Prospective, longitudinal study.

Participants

Patients undergoing cataract surgery.

Methods

Photopic luminance (PL)–best-corrected visual acuity (BCVA) and low luminance (LL)–BCVA were obtained using the ETDRS chart. Low luminance visual acuity deficit scores were calculated by subtracting the LL-BCVA letter score from the PL-BCVA letter score. To demonstrate the reproducibility of these visual acuity measurements, we used data from drusen-only eyes previously published in the Complement Inhibition with Eculizumab for the Treatment of Nonexudative Age-Related Macular Degeneration (COMPLETE) study. The PL-BCVA, LL-BCVA, and LLVAD measurements obtained at an interval of 3 months in this cohort were used for comparison. In the current study, the impact of cataract surgery on LLVAD measurements was analyzed by comparing the PL-BCVA, LL-BCVA, and LLVAD measurements before and after cataract surgery.

Main Outcome Measures

The reproducibility of the visual acuity measurements and the changes in LLVAD measurement after cataract surgery.

Results

In the COMPLETE study, no clinically significant differences were found in the PL-BCVA, LL-BCVA, or LLVAD measurements between baseline and the 3-month follow-up visits with a change of –1.1 letters, –1.3 letters, and 0.1 letters, respectively (P = 0.02, P = 0.11, and P = 0.88, respectively). In the current study, significant increases were found in the PL-BCVA and LL-BCVA measurements, with a change of 7.3 letters and 10.2 letters after cataract surgery (P < 0.001 for both), and a statistically significant decrease in LLVAD measurements was found, with a change of –3.0 letters after cataract surgery (P = 0.002).

Conclusions

Because of the variable effect of cataracts on LL-BCVA measurements and the significant change in LLVAD measurements after cataract surgery, investigators should be aware that cataract surgery during a trial will have an unpredictable impact on LLVAD measurements, and pseudophakic and phakic patients should be analyzed separately.

Depth-resolved visualization and automated quantification of hyperreflective foci on OCT scans using optical attenuation coefficients

An automated depth-resolved algorithm using optical attenuation coefficients (OACs) was developed to visualize, localize, and quantify hyperreflective foci (HRF) seen on OCT imaging that are associated with macular hyperpigmentation and represent an increased risk of disease progression in age related macular degeneration. To achieve this, we first transformed the OCT scans to linear representation, which were then contrasted by OACs. HRF were visualized and localized within the entire scan by differentiating HRF within the retina from HRF along the retinal pigment epithelium (RPE). The total pigment burden was quantified using the en face sum projection of an OAC slab between the inner limiting membrane (ILM) to Bruch's membrane (BM). The manual total pigment burden measurements were also obtained by combining manual outlines of HRF in the B-scans with the total area of hypotransmission defects outlined on sub-RPE slabs, which was used as the reference to compare with those obtained from the automated algorithm. 6×6 mm swept-source OCT scans were collected from a total of 49 eyes from 42 patients with macular HRF. We demonstrate that the algorithm was able to automatically distinguish between HRF within the retina and HRF along the RPE. In 24 test eyes, the total pigment burden measurements by the automated algorithm were compared with measurements obtained from manual segmentations. A significant correlation was found between the total pigment area measurements from the automated and manual segmentations (P < 0.001). The proposed automated algorithm based on OACs should be useful in studying eye diseases involving HRF.

Multimodal Imaging and En Face OCT Detection of Calcified Drusen in Eyes with Age-Related Macular Degeneration

PURPOSE

En face OCT imaging was investigated as a method for the detection and monitoring of calcified drusen in eyes with nonexudative age-related macular degeneration (AMD).

DESIGN

Retrospective case series of a prospective study.

PARTICIPANTS

Patients with nonexudative AMD.

METHODS

A retrospective review was performed of same-day color fundus (CF), fundus autofluorescence (FAF), near-infrared (NIR), and en face swept-source (SS) OCT images to identify eyes with nonexudative AMD and calcified drusen. The appearance and progression of these lesions were compared using the different imaging methods.

MAIN OUTCOME MEASURES

Comparison between the presence of calcified drusen observed on CF images with the detection of these lesions on FAF, NIR, and en face SS OCT images.

RESULTS

Two hundred twenty eyes from 139 patients with nonexudative AMD were studied, with 42.7% of eyes containing calcified drusen either at baseline or during follow-up visits. On the en face SS OCT images, calcified drusen appeared as dark focal lesions referred to as choroidal hypotransmission defects (hypoTDs) that were detected in the choroid using a sub-retinal pigment epithelium (RPE) slab. The corresponding B-scans showed drusen with heterogenous internal reflectivity, hyporeflective cores, and hyperreflective caps. In most calcified drusen, choroidal hypertransmission defects (hyperTDs) were observed to develop over time around the periphery of the hypoTDs, giving them the appearance of a donut lesion on the en face SS OCT images. These donut lesions were associated with significant attenuation of the overlying retina, and the corresponding FAF images showed hypoautofluorescence at the location of these lesions. The donut lesions fulfilled the requirement for a persistent hyperTD, which is synonymous with complete RPE and outer retinal atrophy (cRORA). Six eyes displayed regression of the calcified drusen without cRORA developing. B-scans at the location of these regressed calcified drusen showed deposits along the RPE, with outer retinal thinning in the regions where the calcified lesions previously existed.

CONCLUSIONS

En face OCT imaging is a useful method for the detection and monitoring of calcified drusen and can be used to document the evolution of these drusen as they form donut lesions or foci of cRORA.

Multimodal Imaging, OCT B-Scan Localization, and En Face OCT Detection of Macular Hyperpigmentation in Eyes with Intermediate Age-Related Macular Degeneration

Purpose

Multimodal imaging was used to identify and characterize the cause of hyperpigmentation seen on color fundus images (CFIs) of eyes with intermediate age-related macular degeneration (iAMD).

Design

Retrospective review of a prospective study.

Participants

Patients with iAMD.

Methods

Color fundus images with macular hyperpigmentation were compared with same-day images obtained using fundus autofluorescence (FAF), near infrared reflectance (NIR), and swept-source (SS) OCT imaging. Two SS OCT en face slabs were generated: a retinal slab to identify hyperreflective foci within the retina and a slab from beneath the retinal pigment epithelium (RPE; the sub-RPE slab) that was used to detect regions that cause decreased light transmission into the choroid, also known as hypotransmission defects. All images were registered to allow for qualitative comparisons by 2 independent graders.

Main Outcome Measures

Comparison between foci of macular hyperpigmentation seen on CFIs with the detection of these regions on FAF, NIR, and SS OCT en face images.

Results

Compared with CFIs, FAF imaging seemed to be the least sensitive method for the detection of hyperpigmentation, whereas NIR and SS OCT imaging reliably detected these hyperpigmented areas. Although NIR imaging detected most of the hyperpigmentation seen in CFIs, SS OCT imaging detected all the areas of hyperpigmentation and anatomically localized these areas by using both en face and B-scan images. En face OCT slabs of the retina and sub-RPE region were registered to the CFIs, and areas of hyperpigmentation were shown to correspond to hyperreflective foci in the retina and regions of thickened RPE seen on OCT B-scans. Although both hyperpigmentation and early atrophic lesions appeared bright on NIR imaging, en face SS OCT imaging was able to distinguish these lesions because hyperpigmentary changes appeared dark and early atrophic lesions appeared bright on the sub-RPE slab.

Conclusions

En face OCT imaging in conjunction with OCT B-scans were able to identify and localize the hyperpigmentation seen in CFIs reliably. This hyperpigmentation was not only associated with intraretinal hyperreflective foci, but also corresponded to areas with a thickened RPE.

Persistent Hypertransmission Defects Detected on En Face Swept Source Optical Computed Tomography Images Predict the Formation of Geographic Atrophy in Age-Related Macular Degeneration

PURPOSE

To determine whether persistent hypertransmission defects (hyperTDs), previously shown to have a greatest linear dimension (GLD) ≥250 µm on en face swept source OCT (SS-OCT) images, serve as a stand-alone early biomarker for the future formation geographic atrophy (GA).

DESIGN

Post hoc cohort study using a subgroup of a prospective study.

METHODS

Patients with intermediate age-related macular degeneration (iAMD) underwent 6- × 6-mm SS-OCT raster scans at baseline and during their follow-up period. En face images were generated using a slab with segmentation boundaries positioned 64 µm to 400 µm beneath the Bruch's membrane. Two graders independently evaluated all en face structural images for the presence of hyperTDs with a GLD ≥250 µm and GA.

RESULTS

A total of 190 eyes were included with a mean ± SD follow-up of 31 ± 13.2 months. At baseline, 31 eyes (16%) had at least 1 hyperTD ≥250 µm, and 13 eyes (42%) progressed to GA. In those eyes without a hyperTD ≥250 µm at baseline, 42 (26%) developed hyperTDs ≥250 µm during their follow-up, and 11 eyes (7%) progressed to GA. At the last available follow-up visit, 25 eyes (13%) progressed to GA and of these 25 eyes, a prior hyperTD ≥250 µm was detected in 24 eyes before GA formed. A time-dependent Cox-survival regression analysis estimated an 80-fold (95% CI, 10.7-614, P < .001) increased risk of developing GA once a hyperTD ≥250 µm appeared.

CONCLUSIONS

Persistent hyperTDs detected on en face OCT images were shown to serve as an early stand-alone OCT biomarker for the future formation of GA.

Mitigating the effects of choroidal hyper- and hypo-transmission defects on choroidal vascularity index assessments using optical coherence tomography

Background

Changes in choroidal vascularity index (CVI) are associated with multiple choroid-related ocular diseases. CVI is calculated as the area/volume ratio of vessels in the choroid, which could be affected by alterations in regional signal intensities due to hypo-transmission defects (hypoTDs) caused by drusen and retinal pigment epithelium (RPE) detachments, and hyper-transmission defects (hyperTDs) caused by the absence of RPE. To develop a simulation model to verify the CVI assessments in eyes with hyper/hypoTDs and demonstrate that accurate CVIs can be achieved after attenuation correction on swept-source optical coherence tomography (SS-OCT).

Methods

A simulation model was developed on 6×6 mm macular scans from normal subjects. Signal intensity in a cylindrical region below RPE was altered to mimic hyper/hypoTDs. CVIs were compared inside and outside the simulated regions before and after attenuation correction. CVI assessments of OCT scans from patients with hyperTDs due to geographic atrophy (GA) and from patients with hypoTDs due to drusen that subsequently resolved with the disappearance of the hypoTDs were compared with and without attenuation correction.

Results

Ten normal eyes were recruited to generate the hyper/hypoTD simulation model. In eyes with hypoTDs, CVIs were overestimated, and in eyes with hyperTDs, the CVIs were underestimated (P<0.001). After attenuation correction, the uneven distribution of signal intensity was eliminated and the resulting CVI showed no significant difference compared with the 'ground truth', which is measured from the original scans. Attenuation correction successfully eliminated the influence of hyperTDs caused by GA on CVI measurements (n=38). Quantitatively, no significant difference was found in the CVIs of eyes before and after drusen collapse with attenuation correction (n=8).

Conclusions

The simulation model could reveal the impact of hypo/hyperTDs on CVI quantification in eyes with choroid-involved ocular diseases. The importance of attenuation correction to ensure accuracy in choroidal vessel segmentation was demonstrated by analyzing eyes with GA or drusen.

Regression of Bilateral Peripapillary Choroidal Neovascularization Associated with Idiopathic Intracranial Hypertension after Systemic Acetazolamide Treatment

A rare occurrence of bilateral peripapillary choroidal neovascularization (CNV) in an 18-year-old idiopathic intracranial hypertension (IIH) patient regressed with systemic acetazolamide treatment alone. Multimodal imaging was done, including OCT angiography (OCTA), which showed CNV. No injections were given even though she had macular fluid in her left eye. Nonetheless, the subretinal fluid resolved, and visual acuity improved. This report shows that CNV secondary to IIH can be managed with systemic therapy alone. Moreover, we showed for the first time the ability to diagnose IIH-associated CNV using OCTA.

Comparing Accuracies of Length-Type Geographic Atrophy Growth Rate Metrics Using Atrophy-Front Growth Modeling

Purpose

To compare the accuracies of the previously proposed square-root-transformed and perimeter-adjusted metrics for estimating length-type geographic atrophy (GA) growth rates.

Design

Cross-sectional and simulation-based study.

Participants

Thirty-eight eyes with GA from 27 patients.

Methods

We used a previously developed atrophy-front growth model to provide analytical and numerical evaluations of the square-root-transformed and perimeter-adjusted growth rate metrics on simulated and semisimulated GA growth data.

Main Outcome Measures

Comparison of the accuracies of the square-root-transformed and perimeter-adjusted metrics on simulated and semisimulated GA growth data.

Results

Analytical and numerical evaluations showed that the accuracy of the perimeter-adjusted metric is affected minimally by baseline lesion area, focality, and circularity over a wide range of GA growth rates. Average absolute errors of the perimeter-adjusted metric were approximately 20 times lower than those of the square-root-transformed metrics, per evaluation on a semisimulated dataset with growth rate characteristics matching clinically observed data.

Conclusions

Length-type growth rates have an intuitive, biophysical interpretation that is independent of lesion geometry, which supports their use in clinical trials of GA therapeutics. Taken in the context of prior studies, our analyses suggest that length-type GA growth rates should be measured using the perimeter-adjusted metric, rather than square-root-transformed metrics.

Optical Coherence Tomography Measurements of the Retinal Pigment Epithelium to Bruch Membrane Thickness Around Geographic Atrophy Correlate With Growth

PURPOSE

The retinal pigment epithelium (RPE) to Bruch membrane (BM) distance around geographic atrophy (GA) was measured using an optical attenuation coefficient (OAC) algorithm to determine whether this measurement could serve as a clinical biomarker to predict the annual square root enlargement rate (ER) of GA.

DESIGN

A retrospective analysis of a prospective, observational case series.

METHODS

Eyes with GA secondary to age-related macular degeneration (AMD) were imaged with swept-source OCT (SS-OCT) using a 6 × 6-mm scan pattern. GA lesions were identified and measured using customized en face OCT images, and GA annual square root ERs were calculated. At baseline, the OACs were calculated from OCT datasets to generate customized en face OAC images for GA visualization. RPE-BM distances were measured using OAC data from different subregions around the GA.

RESULTS

A total of 38 eyes from 27 patients were included in this study. Measured RPE-BM distances were the highest in the region closest to GA. The RPE-BM distances immediately around the GA were significantly correlated with GA annual square root ERs (r = 0.595, P < .001 for a 0- to 300-µm rim around the GA). No correlations were found between RPE-BM distances and previously published choriocapillaris (CC) flow deficits in any subregions.

CONCLUSIONS

RPE-BM distances from regions around the GA significantly correlate with the annual ERs of GA. These results suggest that an abnormally thickened RPE/BM complex contributes to GA growth and that this effect is independent of CC perfusion deficits.

Automatic geographic atrophy segmentation using optical attenuation in OCT scans with deep learning

A deep learning algorithm was developed to automatically identify, segment, and quantify geographic atrophy (GA) based on optical attenuation coefficients (OACs) calculated from optical coherence tomography (OCT) datasets. Normal eyes and eyes with GA secondary to age-related macular degeneration were imaged with swept-source OCT using 6 × 6 mm scanning patterns. OACs calculated from OCT scans were used to generate customized composite en face OAC images. GA lesions were identified and measured using customized en face sub-retinal pigment epithelium (subRPE) OCT images. Two deep learning models with the same U-Net architecture were trained using OAC images and subRPE OCT images. Model performance was evaluated using DICE similarity coefficients (DSCs). The GA areas were calculated and compared with manual segmentations using Pearson's correlation and Bland-Altman plots. In total, 80 GA eyes and 60 normal eyes were included in this study, out of which, 16 GA eyes and 12 normal eyes were used to test the models. Both models identified GA with 100% sensitivity and specificity on the subject level. With the GA eyes, the model trained with OAC images achieved significantly higher DSCs, stronger correlation to manual results and smaller mean bias than the model trained with subRPE OCT images (0.940 ± 0.032 vs 0.889 ± 0.056, p = 0.03, paired t-test, r = 0.995 vs r = 0.959, mean bias = 0.011 mm vs mean bias = 0.117 mm). In summary, the proposed deep learning model using composite OAC images effectively and accurately identified, segmented, and quantified GA using OCT scans.

An Update on the Hemodynamic Model of Age-Related Macular Degeneration

PURPOSE

To provide an update on the hemodynamic model of age-related macular degeneration (AMD).

DESIGN

Evidence-based perspective.

METHODS

Review of the literature and experience of the authors.

RESULTS

Choroidal hemodynamics are not the primary cause of AMD as proposed by Ephraim Friedman in 1997. However, evidence is accumulating to suggest that choroidal perfusion is an important environmental influence that contributes to our understanding of disease progression in this complex genetic disorder. Although early and intermediate AMD seem to be influenced to a large extent by the underlying genetics, the asymmetry of disease progression to the later stages of AMD cannot be explained by genetics alone. The progression of disease and the asymmetry of this progression seem to correlate with abnormalities in choroidal perfusion that can be documented by optical coherence tomography. These perfusion abnormalities in the setting of a thickened Bruch's membrane are thought to exacerbate the impaired nutritional exchange between the retinal pigment epithelium and the choriocapillaris. We propose that the genetic susceptibility to develop AMD combined with age-related changes in macular choroidal hemodynamics, such as increasing choriocapillaris perfusion deficits and decreasing choroidal vascular densities, play an important role in disease progression and may help to explain the asymmetry between eyes, particularly in the later stages of AMD.

CONCLUSIONS

This updated hemodynamic model of AMD focuses on disease progression and highlights the importance of age-related changes in the choroidal circulation as a major environmental influence on disease severity in eyes that are genetically susceptible to develop AMD.

Laser-induced choroidal neovascularization detected on optical coherence tomography angiography in patients with diabetic retinopathy

Purpose

To report two cases of laser-induced choroidal neovascularization (CNV) using swept source optical coherence tomography (SS-OCTA) imaging in patients with proliferative diabetic retinopathy.

Observations

Two patients developed CNV adjacent to laser scars, and these neovascular lesions were detected on SS-OCTA imaging. Historically, both patients had subretinal fluid associated with these lesions. Visual acuity for both patients was 20/25 in the affected eyes. Both patients were observed over multiple years with stable CNV and visual acuity.

Conclusions and importance

SS-OCTA was able to detect laser-induced CNV in a rapid and non-invasive manner. When there is no foveal involvement and excellent visual acuity, we recommend close observation since the CNV may not progress.

Diagnosing Persistent Hyper-Transmission Defects on En Face OCT Imaging of Age-Related Macular Degeneration

PURPOSE

A training exercise was performed to study the ability of graders to reliably identify precursor lesions to geographic atrophy (GA), known as persistent choroidal hyper-transmission defects (hyperTDs), using en face optical coherence tomography (OCT) images from eyes with non-exudative age-related macular degeneration (AMD).

DESIGN

Intergrader agreement study PARTICIPANTS: Eleven graders participated in this exercise.

METHODS

Formal training on how to identify persistent hyperTDs on en face OCT images was provided to the graders. Persistent hyperTDs were defined as bright lesions having a greatest linear dimension (GLD) of at least 250 μm. Training consisted of a tutorial session followed by the grading of three pretest exercises, each consisting of three cases. After all the graders scored 100% on the pretest exercises, they performed a final exercise consisting of 30 en face OCT images from 29 eyes with non-exudative AMD containing 107 hyperTDs that each grader needed to evaluate. The cases contained a variety of AMD-related atrophic lesions.

MAIN OUTCOME MEASURES

The sensitivity, positive predictive value (PPV), and modified accuracy were assessed for each grader.

RESULTS

A total of 1177 hyperTDs from 30 en face OCT images were reviewed by the graders. The mean sensitivity, PPV, and modified accuracy for all the graders were calculated to be 99.0%, 99.2%, and 98.2%, respectively. There was a 97% agreement observed between all the graders (AC₁ = 0.97). Internal graders from the Bascom Palmer Eye Institute (BPEI) had a slightly higher agreement compared with the external graders (AC₁ = 0.98 vs. 0.96). The hyperTDs most often incorrectly identified included the following features: (1) hyperTDs containing a hypo-transmission defect (hypoTD) core, (2) single hyperTDs that were incorrectly graded as two separate lesions, and (3) hyperTDs with a borderline GLD that was close to 250 μm.

CONCLUSION

The accurate detection of persistent hyperTDs on en face OCT images by graders demonstrates the feasibility of using this OCT biomarker to identify disease progression in eyes with non-exudative AMD, especially when used as a clinical trial endpoint in studies designed to test new therapies that may slow disease progression from intermediate AMD (iAMD) to GA.

Local Geographic Atrophy Growth Rates Not Influenced by Close Proximity to Non-Exudative Type 1 Macular Neovascularization

Purpose

The local growth rates of geographic atrophy (GA) adjacent to non-exudative type 1 macular neovascularization (MNV) were investigated to determine if MNV influenced GA growth.

Methods

Eyes with GA and non-exudative type 1 MNV were followed for at least 1 year. Both GA and the MNV were imaged and measured using swept-source optical coherence tomography angiography (SS-OCTA) scans. Pearson correlations were computed between local growth rates of GA, which were estimated using a biophysical GA growth model, and local distances-to-MNV. Corresponding P values for the null hypothesis of no Pearson correlation were computed using a Monte Carlo approach that adjusts for spatial autocorrelations.

Results

Nine eyes were included in this study. There were positive correlations (Pearson's r > 0) between distance-to-MNV and local GA growth in eight (89%) of the eyes; however, in all but one eye (11%), correlations were relatively weak and statistically nonsignificant after Bonferroni correction (corrected P > 0.05).

Conclusions

SS-OCTA imaging combined with GA growth modeling and spatial statistical analysis enabled quantitative assessment of correlations between local GA growth rates and local distances-to-MNV. Our results are not consistent with non-exudative type 1 MNV having a strong inhibitory effect on local GA growth rates.

Interocular asymmetry of choroidal thickness and vascularity index measurements in normal eyes assessed by swept-source optical coherence tomography

BACKGROUND

To investigate the symmetry of interocular choroidal thickness and vascularity index measurements in normal eyes using swept-source optical coherence tomography (SS-OCT). Cross-sectional and observational study. This study included 244 eyes of 122 normal adults with ages uniformly distributed from 19 to 89 years.

METHODS

SS-OCT imaging was performed using a scanning pattern of 12×12 mm. Mean choroidal thickness (MCT) and choroidal vascularity index (CVI) measurements in the entire scanning region were obtained using a validated and published automatic method. The correlation and differences (including signed and absolute differences) between bilateral MCT and CVI measurements were analyzed at the following 6 regions: 3 concentric circles centered on the fovea with diameters of 2.5, 5, and 11 mm; the inner rim from 2.5 to 5 mm circle; the outer rim from 5 to 11 mm circle; and the entire 12×12-mm scan region, respectively. Comparison of interocular MCT and CVI measurements.

RESULTS

MCT measurements in right and left eyes were strongly correlated in all regions [all intraclass correlation (ICC) >0.73], but MCT measurements in right eyes were significantly thicker than in left eyes. CVI measurements in right and left eyes were moderately correlated in all regions (all ICC >0.46), but CVI measurements in right eyes were significantly smaller than that in left eyes in the macular subregions (2.5 mm circle, 5 mm circle, and the inner rim). Neither signed nor absolute interocular differences in MCT were correlated with corresponding CVI interocular differences.

CONCLUSIONS

Choroidal differences exist between normal fellow eyes in adults in the absence of obvious pathology. This study is useful in assisting clinicians and researchers in distinguishing asymmetric changes that are to be expected in normal eyes versus changes that could be associated with diseases.