Myopic macular schisis: Insights into distinct morphological subtypes and novel biomechanical hypothesis

PURPOSE

To analyze the features of myopic macular schisis (MMS) in different retinal layers and to explore the role of Müller cells in the pathophysiology of such condition.

METHODS

Spectral-domain optical coherence tomography (SD-OCT) images of myopic eyes with staphyloma and macular schisis were reviewed. The morphological features of MMS were analyzed and correlated with their geographical location in the parafoveal and perifoveal region. A biomechanical model was adopted to explain MMS morphological differences. The effect of the different schisis subtypes with best corrected visual acuity (BCVA) was also explored.

RESULTS

A total of 36 eyes from 26 patients were included in this study. MMS was classified into inner, middle and outer retinal subtypes. The prevalence of middle retinal schisis was significantly lower in the parafovea, within a central 3 mm-diameter circle (p < 0.001) centered at the fovea . The prevalence of inner retinal schisis was significantly higher outside the central 3-mm diameter circle, in the perifoveal region (p < 0.001). No significant differences were noted in the prevalence of outer retinal schisis for these two locations (p = 0.475). The presence of middle retinal schisis within the central 3-mm diameter circle showed a weak association with lower BCVA (p = 0.058). The presence of outer retinal schisis within the central 3-mm diameter circle was significantly related with lower BCVA (p = 0.024).

CONCLUSION

Three major forms of MMS are distinguished: inner, middle and outer retinal schisis. This classification may have clinical importance as only the outer grade of schisis was associated with vision loss.

Klebsiella pneumoniae Endophthalmitis with Subretinal Abscess: A Case Series and Review of the Literature

This study assessed prognostic factors and the role of vitrectomy in patients with subretinal abscesses secondary to K. pneumoniae endophthalmitis. We reviewed published studies, including three cases from our cohort. Among 50 eyes, 26 had poor visual outcomes (final visual acuity <20/800, eyeball removal, or phthisis bulbi). Poor outcomes correlated with delayed ocular symptom-to-diagnosis time, initial visual acuity <20/800, severe vitritis, and macular involvement of abscesses (p < 0.001, p = 0.008, p < 0.001, and p = 0.033, respectively). Vitrectomy had a trend towards reducing eyeball removal and phthisis bulbi rates compared with non-vitrectomy (10.8% vs 30.8%, p = 0.181). However, the final visual acuity was not different and the rate of retinal detachment tended to be higher in vitrectomized eyes (45.9% vs 15.4%, p = 0.095). The study suggested that vitrectomy and drainage of K. pneumoniae subretinal abscesses could be avoided in patients with a mild degree of vitritis.

Effect of fenestrated sterile drape and face mask on bacterial dispersion toward the periocular area during intravitreal injection

This experimental crossover study was performed to investigate whether fenestrated surgical drapes (covering the nose and mouth but with an opening over the periorbital area) with or without patients' surgical face masks increase periorbital bacterial dispersion during simulated intravitreal injection conditions. Each of the 16 healthy volunteers performed 14 scenarios involving different mask and drape conditions in both silent and speaking situations. In each scenario, the subject lay down flat on the back with a blood agar plate being held at the inferior orbital rim perpendicular to the face to capture airflow from breathing/speaking. Another blood agar plate placed 50 cm away from the subject served as an experimental control. A total of 224 experiments were performed. Speaking situations significantly showed more colony forming units (CFUs) compared with their controls (P = 0.014). There were no significant differences in CFUs between wearing vs not wearing the masks (P = 0.887 for speaking and P = 0.219 for silent) and using vs not using the drapes (P = 0.941 for speaking and P = 0.687 for silent). Reusable and disposable drapes were also not significantly different (P = 1.00 for speaking and P = 0.625 for silent). Streptococcus spp., the oropharyngeal microbiota, were only cultivated from speaking scenarios. While refraining from speaking (for both practitioners and patients) is the mainstay of reducing bacterial dispersion and risks of post-injection endophthalmitis, the use of fenestrated surgical drapes or patients' face masks did not significantly affect the amount of bacterial dispersion toward the periorbital area.

Optical Coherence Tomography Angiography Biomarkers in Thai Patients With Diabetic Nephropathy: A Diabetic Eye and Kidney Diseases (DEK-D) Study

Purpose

To identify optical coherence tomography angiography (OCTA) biomarkers to predict the diabetic nephropathy (DN) and their associations with 24-hour urine albumin levels in diabetic patients.

Methods

This cross-sectional, observational study examined 186 eyes from 93 individuals subdivided into three groups according to 24-hour urine albumin levels: no DN, early DN, and late DN. Vessel density (VD), fractal dimension, foveal avascular zone area, intercapillary area, central retinal thickness, and subfoveal choroidal thickness were measured from OCTA images to determine their association with the DN stages.

Results

VD values of the superficial capillary plexus, deep capillary plexus, and whole retina were significantly lower in the early DN group compared to the no DN group (adjusted P = 0.042, 0.016, and 0.008, respectively). VD values for the deep capillary plexus and whole retina were significantly decreased in the late DN group compared to the no DN group (adjusted P = 0.025 and 0.021, respectively). Mean fractal dimension, intercapillary area, foveal avascular zone area, central retinal thickness, and subfoveal choroidal thickness were not statistically different among the three groups.

Conclusions

VD may be a useful parameter for the early non-invasive screening of DN. Further studies in larger populations are needed to establish a cutoff value for detection.

Translational Relevance

This study investigated the association of each retinal vasculature measurement by OCTA and diabetic nephropathy status which could serve as an alternative way to screen for albuminuria.

Detecting and staging diabetic retinopathy in retinal images using multi-branch CNN

Purpose

This paper aims to propose a solution for detecting and grading diabetic retinopathy (DR) in retinal images using a convolutional neural network (CNN)-based approach. It could classify input retinal images into a normal class or an abnormal class, which would be further split into four stages of abnormalities automatically.

Design/methodology/approach

The proposed solution is developed based on a newly proposed CNN architecture, namely, DeepRoot. It consists of one main branch, which is connected by two side branches. The main branch is responsible for the primary feature extractor of both high-level and low-level features of retinal images. Then, the side branches further extract more complex and detailed features from the features outputted from the main branch. They are designed to capture details of small traces of DR in retinal images, using modified zoom-in/zoom-out and attention layers.

Findings

The proposed method is trained, validated and tested on the Kaggle dataset. The regularization of the trained model is evaluated using unseen data samples, which were self-collected from a real scenario from a hospital. It achieves a promising performance with a sensitivity of 98.18% under the two classes scenario.

Originality/value

The new CNN-based architecture (i.e. DeepRoot) is introduced with the concept of a multi-branch network. It could assist in solving a problem of an unbalanced dataset, especially when there are common characteristics across different classes (i.e. four stages of DR). Different classes could be outputted at different depths of the network.

Optical Coherence Tomography Features for Identifying Posttreatment Complete Polypoidal Regression in Polypoidal Choroidal Vasculopathy

PURPOSE

To determine accuracy and relative risk (RR) of posttreatment optical coherence tomography (OCT) features in identifying complete or incomplete polypoidal regression in polypoidal choroidal vasculopathy (PCV).

DESIGN

Validity analysis.

METHODS

Treatment-naive PCV eyes undergoing OCT and indocyanine green angiography (ICGA) at baseline and posttreatment were included. Two graders confirmed diagnosis and identified posttreatment complete or incomplete regression on ICGA. Two other graders classified OCT characteristics of pigment epithelial detachment (PED) (polypoidal lesion) based on 5 prespecified features: "A," no PED; "B," PED with internal homogeneous reflectivity with predominant "BUN" (blended retinal pigment epithelium with underlying structure) sign; "C," PED with internal homogeneous reflectivity with minimal "BUN"; "D," heterogeneous PED; and "E," PED with hyporeflectivity.

RESULTS

Among 130 polypoidal lesions (65 pretreatment and 65 posttreatment) of 39 PCV eyes (39 patients; 54% female; mean age±SD: 64.6±8.2), all pretreatment lesions showed feature D on OCT. Posttreatment lesions with complete regression (31 lesions) showed OCT features A, B, C, D, and E in 32%, 45%, 13%, 10%, and 0%, respectively. Posttreatment lesions with incomplete regression (34 lesions) showed OCT features A, B, C, D, and E in 0%, 6%, 15%, 79%, and 0%, respectively. Presence of either feature A or B had highest accuracy (86%; 95% confidence interval: 75%-93%); 77% sensitivity; 94% specificity; RR 5.0 (3.5-7.1, P<0.001) for complete regression. Presence of feature D had highest accuracy (85%; 95% confidence interval: 74%-92%); 79% sensitivity; 90% specificity; RR 4.6 (3.0-6.9, P<0.001) for incomplete regression.

CONCLUSIONS

Without ICGA, OCT features could provide high accuracy in identifying posttreatment complete or incomplete polypoidal regression in PCV.

Development and Validation of a New Design Selfassessment logMAR Visual Acuity Test (“Chudjane” iPhone- and iPad-based Application) in a Normal Eyes Population

Objective: To validate and further design the “Chudjane” application (app), a new design self- assessment logMAR test for distance visual acuity (VA), by comparing the results against the use of a standard numeric ETDRS chart in normal eye population.Materials and Methods: In total, 52 volunteers who had a normal eye exam and best-corrected VA score by numeric ETDRS (NE) chart equal to or better than 6/6 (logMAR score 0.00 or less) were included. The “Chudjane” app with 3 patterns of optotypes (Arabic numbers (AN), Tumbling-E (TE) and Landolt-C (LC)) was used twice to assess VA individually.Results: The mean VA in each test NE, AN, TE, LC from the first round were -0.06, -0.10, -0.08 and -0.04, respectively compared to -0.07, -0.12, -0.09 and -0.05 from the second round respectively. Comparing results from the first and second round revealed that NE and LC had higher test-retest reliability (ICC=0.712, 0.789 respectively) than AN and TE (ICC=0.140, 0.495 respectively). For validity, result from NE was compared to each app test using the second round values. Modified Bland-Altman plot showed the mean differences (95% LOA) for NE-AN, NE-TE and NE-LC of 0.05 (-0.11 to 0.20), 0.02 (-0.11 to 0.15) and -0.03 (-0.19 to 0.13) respectively. Simple linear regression analysis of the difference (i.e. NE-AN, NE-TE and NE-LC) on NE showed that the difference did not depend on the NE value with slope close to zero.Conclusion: The study demonstrated that by using the «Chudjane» application, LC had higher test-retest reliability and higher validity than TE and AN compared to the standard ETDRS chart.

Are intravitreal injections essential during the COVID-19 pandemic? Global preferred practice patterns and practical recommendations

Tertiary outpatient ophthalmology clinics are high-risk environments for COVID-19 transmission, especially retina clinics, where regular follow-up is needed for elderly patients with multiple comorbidities. Intravitreal injection therapy (IVT) for chronic macular diseases, is one of the most common procedures performed, associated with a significant burden of care because of the vigorous treatment regimen associated with multiple investigations. While minimizing the risk of COVID-19 infection transmission is a priority, this must be balanced against the continued provision of sight-saving ophthalmic care to patients at risk of permanent vision loss. This review aims to give evidence-based guidelines on managing IVT during the COVID-19 pandemic in common macular diseases such as age-related macular degeneration, diabetic macula edema and retinal vascular disease and to report on how the COVID-19 pandemic has affected IVT practices worldwide.

To illustrate some real-world examples, 18 participants in the International Retina Collaborative, from 15 countries and across four continents, were surveyed regarding pre- and during- COVID-19 pandemic IVT practices in tertiary ophthalmic centers. The majority of centers reported a reduction in the number of appointments to reduce the risk of the spread of COVID-19 with varying changes to their IVT regimen to treat various macula diseases. Due to the constantly evolving nature of the COVID-19 pandemic, and the uncertainty about the normal resumption of health services, we suggest that new solutions for eye healthcare provision, like telemedicine, may be adopted in the future when we consider new long-term adaptations required to cope with the COVID-19 pandemic.

Subretinal gnathostomiasis: A successful focal laser photocoagulation for a living parasite

Purpose

To report a case of subretinal gnathostomiasis presenting with progressive subretinal tracts of a living parasite and successfully treated with focal laser photocoagulation.

Method

Observational case report.

Patient

A 29-year-old Thai male complained of blurred vision and floaters in his left eye for two weeks. An ocular examination showed multiple, whitish, subretinal tracks at the superotemporal retina. After 5 days of oral albendazole, a moving parasite was confirmed by multimodal retinal imaging. An immunoblotting analysis was positive for Gnathostoma species.

Result

The patient was treated by laser photocoagulation with frequency-doubled Nd:YAG laser around and over the parasite. Oral albendozole was continued and naproxen was prescribed for four weeks. His vision improved to 20/20 and the inflammation subsided completely within three months. The patient has been followed for five years without local and systemic complications.

Conclusions

Focal laser photocoagulation without systemic steroids could be a successful treatment for active subretinal gnathostomiasis with a satisfactory safety profile in a long-term follow-up.

In-Person Verification of Deep Learning Algorithm for Diabetic Retinopathy Screening Using Different Techniques Across Fundus Image Devices

Purpose

To evaluate the clinical performance of an automated diabetic retinopathy (DR) screening model to detect referable cases at Siriraj Hospital, Bangkok, Thailand.

Methods

A retrospective review of two sets of fundus photographs (Eidon and Nidek) was undertaken. The images were classified by DR staging prior to the development of a DR screening model. In a prospective cross-sectional enrollment of patients with diabetes, automated detection of referable DR was compared with the results of the gold standard, a dilated fundus examination.

Results

The study analyzed 2533 Nidek fundus images and 1989 Eidon images. The sensitivities calculated for the Nidek and Eidon images were 0.93 and 0.88 and the specificities were 0.91 and 0.85, respectively. In a clinical verification phase using 982 Nidek and 674 Eidon photographs, the calculated sensitivities and specificities were 0.86 and 0.92 for Nidek along with 0.92 and 0.84 for Eidon, respectively. The 60°-field images from the Eidon yielded a more desirable performance in differentiating referable DR than did the corresponding images from the Nidek.

Conclusions

A conventional fundus examination requires intense healthcare resources. It is time consuming and possibly leads to unavoidable human errors. The deep learning algorithm for the detection of referable DR exhibited a favorable performance and is a promising alternative for DR screening. However, variations in the color and pixels of photographs can cause differences in sensitivity and specificity. The image angle and poor quality of fundus photographs were the main limitations of the automated method.

Translational Relevance

The deep learning algorithm, developed from basic research of image processing, was applied to detect referable DR in a real-word clinical care setting.

Non-Neovascular Pachychoroid Disease Mimicking Exudative Age-Related Macular Degeneration

Purpose:

To describe a case of pachychoroid disease most compatible with central serous chorioretinopathy (CSC) presented with a large relapsing retinal pigment epithelial detachment (PED) associated with only a small amount of subretinal fluid (SRF) in the background of macular drusen in an elderly patient mimicking neovascular age-related macular degeneration (AMD).

Methods:

This was a review of 32 months of the clinical course and findings on multimodal imaging including fundus photography, optical coherence tomography, fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), and optical coherence tomography angiography (OCTA).

Results:

A large relapsing PED sometimes with small amount of SRF at its apex was found in the background of macular drusen in the right eye of a 63-year-old Thai woman. The relapses of the PED showed an apparent association with recent steroid exposure. Multimodal imaging demonstrated the characteristics of pachychoroid diseases with pachyvessels and choroidal hyperpermeability. The PED and SRF responded well to anti-vascular endothelial growth factor (anti-VEGF) therapy, especially aflibercept, but could also be spontaneously resolved without anti-VEGF. No evidence of choroidal neovascularization or polyps could be identified by serial FFA, ICGA, and OCTA even when the retinal pigment epithelium was completely flat with no obscuration by PED.

Conclusions:

A large PED with little SRF could present signs of CSC. This clinical presentation could be confused with neovascular AMD, and multimodal retinal imaging was crucial to guide correct diagnosis and management.

Recent advances in wide field and ultrawide field optical coherence tomography angiography in retinochoroidal pathologies

Introduction: With the advent of wide field (WF) and ultra-wide field (UWF) imaging in color fundus photography and fluorescein angiography (FA), the importance of an expanded field-of-view (FOV) has been illustrated for early detection of several chorioretinal disorders. The need to bring similar utility to optical coherence tomography angiography (OCTA) is imperative.Areas covered: For this review, we explored all research items with WF or UWF on Pubmed Central and Google Scholar. Software-based methods included algorithms for motion correction, artifact reduction, image pre-processing, post-processing and montage protocols while hardware methods included swept-source OCTA, faster scanning sources, hardware-based motion tracking and image registration, scanning sources with faster speeds and lower resolution. For various disorders such as diabetic retinopathy, uveitis, vascular disorders, among others, the increased FOV showed demonstrably increased detection rates and diagnostic yield.Expert opinion: Increased FOV in OCTA imaging is a meaningful and impactful step in ophthalmic imaging. Overcoming the hardware-based limitations can potentially yield higher FOV without loss of important details. In addition to improvements in the hardware and available equipment, better software tools and image processing algorithms may greatly enhance the utility of UWF OCTA in care of patients with various retinochoroidal diseases.

Long-term visual and anatomic outcomes of patients with peripapillary pachychoroid syndrome

Background/Aims

To analyse the long-term anatomic and visual outcomes of patients with peripapillary pachychoroid syndrome (PPS), a recently described entity in the pachychoroid disease spectrum.

Methods

This study retrospectively included patients from several retina centres worldwide. Visual acuity (VA), retinal thickness and choroidal thickness at baseline, 6 months and final follow-up were assessed. Temporal trends in VA and anatomic characteristics were evaluated. Visual and anatomic outcomes in eyes that were observed versus those that were treated were analysed.

Results

Fifty-six eyes of 35 patients were included with mean follow-up of 27±17 months. Median VA was 20/36 at baseline and remained stable through follow-up (p=0.77). Retinal thickness significantly decreased subfoveally (p=0.012), 1.5 mm nasal to the fovea (p=0.002) and 3.0 mm nasal to the fovea (p=0.0035) corresponding to areas of increased thickening at baseline. Choroidal thickness significantly decreased subfoveally (p=0.0030) and 1.5 mm nasal to the fovea (p=0.0030). Forty-three eyes were treated with modalities including antivascular endothelial growth factor injection, photodynamic therapy, and others. VA remained stable in treated eyes over follow-up (p=0.67). An isolated peripapillary fluid pocket in the outer nuclear layer was characteristic of PPS.

Conclusion

Patients with PPS experienced decreased retinal oedema and decreased choroidal thickening throughout the course of disease. While some patients experienced visual decline, the overall visual outcome was relatively favourable and independent of trends in retinal or choroidal thickening.

Unusual non-nanophthalmic uveal effusion syndrome with histologically normal scleral architecture: a case report

Background

To report an unusual case of non-nanophthalmic uveal effusion syndrome (UES) with histologically normal sclera but responsive to scleral resection.

Case presentation

A73-year-old man presented with a bullous retinal detachment without ciliochoroidal detachment on funduscopic examination of the right eye. The axial length of both eyes was normal. Extensive investigations for possible causes of exudative retinal detachment were performed with unremarkable results except for choroidal hyperpermeability on indocyanine green angiography (ICGA). Ultrasound biomicroscopy (UBM) revealed scleral thickening with peripheral choroidal elevation leading to the diagnosis of UES.

Partial thickness sclerectomy and sclerotomy was performed resulting in complete retinal reattachment, reduction of choroidal hyperpermeability on ICGA and improvement of visual acuity. However, histological studies of the excised sclera revealed no scleral architectural changes or abnormal deposits.

Conclusions

The diagnosis of UES in non-nanophthalmic eyes is challenging. Thorough systemic and ocular investigations are critical to rule out other etiologies. UBM can be helpful to evaluate scleral thickness and anterior choroid in equivocal cases. Our case was unique in that, although the sclera was thick, no abnormal microscopic scleral architecture could be identified. Misdiagnosis may lead to different surgical procedures such as vitrectomy resulting in unfavorable outcomes.

Relationship Between Nerve Fiber Layer Hemorrhages and Outcomes in Central Retinal Vein Occlusion

Purpose

To evaluate the depth and pattern of retinal hemorrhage in acute central retinal vein occlusion (CRVO) and to correlate these with visual and anatomic outcomes.

Methods

Retinal hemorrhages were evaluated with color fundus photography and fluorescein angiography at baseline and follow-up. Snellen visual acuity (VA), central foveal thickness (CFT), extent of retinal ischemia, and development of neovascularization were analyzed.

Results

108 eyes from 108 patients were evaluated. Mean age was 63.6 ± 16.1 years with a predilection for the right eye (73.1%). Average follow-up was 17.2 ± 19.2 months. Mean VA at baseline was 20/126 and 20/80 at final follow-up. Baseline (P = 0.005) and final VA (P = 0.02) in eyes with perivascular nerve fiber layer (NFL) hemorrhages were significantly worse than in eyes with deep hemorrhages alone. Baseline CFT was greater in the group with perivascular hemorrhages (826 ± 394 µm) compared to the group with deep hemorrhages alone (455 ± 273 µm, P < 0.001). The 10 disc areas of retinal ischemia was more common in patients with perivascular (80.0%) and peripapillary (31.3%) versus deep hemorrhages alone (16.1%, P < 0.001). Neovascularization of the iris was more common, although this differrence was not significant, in the groups with peripapillary (14.3%) and perivascular (2.0%) NFL versus deep hemorrhages alone (0.0%).

Conclusions

NFL retinal hemorrhages at baseline correlate with more severe forms of CRVO, with greater macular edema, poorer visual outcomes, and greater risk of ischemia and neovascularization. This may be related to the organization of the retinal capillary plexus. The depth and pattern of distribution of retinal hemorrhages in CRVO may provide an easily identifiable early biomarker of CRVO prognosis.

PERIVASCULAR GRANULOMATA IN THE RETINA DEMONSTRATED BY EN FACE OPTICAL COHERENCE TOMOGRAPHY IN A PATIENT WITH BLAU SYNDROME

PURPOSE

To describe the multimodal retinal imaging findings of a case of Blau syndrome.

METHODS

Case report. The multimodal retinal imaging findings, including widefield angiography, cross-sectional and en face spectral domain optical coherence tomography, and optical coherence tomography angiography, of a case of Blau syndrome are described.

RESULTS

A 12-year-old Hispanic girl with polyarticular arthritis, skin rash, and panuveitis was diagnosed with a rare condition referred to as Blau syndrome. Genetic testing identified an NOD2 mutation. Cross-sectional and en face optical coherence tomography illustrated presumed perivascular granulomata in the middle retina. Optical coherence tomography angiography failed to display flow within these lesions.

CONCLUSION

This report illustrates the presence of a remarkable distribution of perivascular, presumably granulomatous, retinal lesions in the middle retina. Similar perivascular granulomata have been noted in the histopathological analysis of ocular sarcoidosis.

The Expanded Spectrum of Perifoveal Exudative Vascular Anomalous Complex

PURPOSE

To expand our understanding of the uncommon entity, referred to as perifoveal exudative vascular anomalous complex (PEVAC) by describing multimodal imaging findings, including optical coherence tomography angiography (OCT-A).

DESIGN

Retrospective cohort study.

METHODS

Patients diagnosed with PEVAC were identified at 4 retina referral centers worldwide and underwent complete ophthalmologic examination including structural OCT, OCT-A, fluorescein angiography (FA), and indocyanine green angiography (ICGA). Demographics and clinical findings were analyzed at baseline and at available follow-ups.

RESULTS

Fifteen eyes (15 patients, mean age 73 ± 13 years) were included. Six of 15 eyes were diagnosed with coincident age-related macular degeneration (AMD) and 2 with myopic macular degeneration. On fundus examination PEVAC presented as a large perifoveal isolated aneurysm, unifocal in 12 of 15 eyes, associated with small retinal hemorrhages and intraretinal exudation. On structural OCT, PEVAC appeared as a round hyperreflective lesion with hyporeflective lumen, typically surrounded by intraretinal cystic spaces. Dye angiography demonstrated a well-defined hyperfluorescent lesion with variable leakage on FA and without leakage on ICGA. OCT-A showed flow signal correlating with the aneurysmal lesion connecting to retinal capillary plexuses. Seven patients were followed for 13.0 ± 10.5 months with no evidence of functional/anatomic changes. Three patients underwent anti-vascular endothelial growth factor (VEGF) intravitreal injections without improvement. Two eyes were associated with a type 3 neovascularization eccentric to PEVAC.

CONCLUSIONS

PEVAC is an isolated, perifoveal, aneurysmal abnormality, occurring in otherwise healthy patients who may manifest other macular disease including AMD and myopic macular degeneration. PEVAC did not typically respond to anti-VEGF therapy, and may be associated with type 3 neovascularization.

Quantitative Analysis of Three Distinct Retinal Capillary Plexuses in Healthy Eyes Using Optical Coherence Tomography Angiography

Purpose

To identify and quantify the three distinct retinal capillary plexuses and the foveal avascular zone (FAZ) in healthy subjects according to age using optical coherence tomography angiography (OCTA) with novel projection artifact removal (PAR) software and improved segmentation.

Methods

All eyes in this cross-sectional study underwent OCTA imaging using RTVue XR Avanti with novel PAR AngioVue software. OCTA scans were analyzed and the three main parafoveal retinal capillary plexuses were segmented and vessel density and FAZ area were calculated.

Results

A total of 152 normal eyes from 95 subjects (39 males, 56 females, mean age 42 ± 25 years) were included. The mean vessel density was 15.48 ± 2.04 mm-1 in the superficial retinal capillary plexus (SCP), 15.28 ± 1.82 mm-1 in the intermediate retinal capillary plexus (ICP), and 16.33 ± 2.32 mm-1 in the deep retinal capillary plexus (DCP) for 3 × 3-mm OCTA images. Analysis of 3 × 3-mm scans yielded a mean FAZ area of 0.270 ± 0.101 mm2. The average reduction in vessel density per year of age with 3 × 3-mm OCTA scans was 0.04 mm-1 (0.22%) in the SCP, 0.05 mm-1 (0.27%) in the ICP, and 0.06 mm-1 (0.30%) in the DCP. The average increase in FAZ area per year of age was 0.0015 mm2 (0.72%).

Conclusions

Novel PAR software may provide improved visualization of all three major parafoveal retinal capillary plexuses including the ICP. Using this technology, SCP, ICP, and DCP vessel density decreased with increasing age while FAZ area increased with age.

Foveal and Peripapillary Vascular Decrement in Migraine With Aura Demonstrated by Optical Coherence Tomography Angiography

Purpose

Migraine, particularly with aura, has been associated with ocular and systemic ischemic complications, but there are limited data on the ocular vasculature in migraine. We used optical coherence tomography angiography (OCTA) to assess perfusion of the macula and optic nerve in migraine patients, with (MA) and without (MO) aura, compared to healthy controls (HC).

Methods

We recruited 15 MA (mean age 42 years), 12 MO (mean age 46 years), and 22 HC (mean age 39 years) participants from neurology and neuro-ophthalmology clinics. Participants underwent optical coherence tomography and 3 × 3 mm OCTA of the macula and optic nerve. Foveal avascular zone area was automatically measured using AngioVue software, and vessel density was calculated as blood vessel length divided by scan area (mm-1) after skeletonization of OCTA images.

Results

On macular OCTA, MA participants had an enlarged foveal avascular zone area when compared with HC (0.300 ± 0.019 vs. 0.220 ± 0.066 mm2, P = 0.006). In addition, superficial foveal vessel density was decreased in MA participants when compared with MO participants (7.8 ± 0.31 vs. 9.3 ± 0.44, P = 0.04) and HC (7.8 ± 0.31 vs. 9.4 ± 0.21 mm-1, P = 0.002). On optic nerve OCTA, the MA participants had reduced superior peripapillary vessel density when compared with the MO participants (12.0 ± 0.45 vs. 14.0 ± 0.38 mm-1, P = 0.031) and HC (12.0 ± 0.45 vs. 14.1 ± 0.53 mm-1, P = 0.035). There were no significant differences between the MO and HC groups.

Conclusions

Migraine with, but not without, aura was associated with foveal and peripapillary vascular decrements, which may possibly mediate increased risk of ocular and systemic vascular complications in these patients. OCTA could potentially be useful as a biomarker for migraine with aura.

REGRESSION OF TYPE 2 NEOVASCULARIZATION INTO A TYPE 1 PATTERN AFTER INTRAVITREAL ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR THERAPY FOR NEOVASCULAR AGE-RELATED MACULAR DEGENERATION

PURPOSE

To study eyes with Type 2 (subretinal) neovascularization (NV) secondary to neovascular age-related macular degeneration (nAMD) that shows lesion regression into a Type 1 (subretinal pigment epithelium) pattern after treatment with intravitreal anti-vascular endothelial growth factor (VEGF) therapy.

METHODS

Retrospective consecutive case series. Patients showing regression of Type 2 neovascularization into a Type 1 pattern after envelopment by retinal pigment epithelium were included in this analysis. A review of the clinical records and multimodal imaging of these cases was performed at baseline, 1, 3, 6, and 12 months. Demographic data, best-corrected visual acuity (BCVA), color fundus photography, fundus autofluorescence (FAF), fluorescein angiography, near-infrared reflectance (NIR), and structural spectral-domain optical coherence tomography (SD-OCT) were reviewed and analyzed. When available, optical coherence tomography angiography images were analyzed as well.

RESULTS

Ten eyes of 9 patients (6 males) diagnosed with treatment-naive pure Type 2 neovascularization secondary to nAMD were included. The mean age was 80.7 years (SD ± 4.30). Mean best-corrected visual acuity expressed in logMAR (Snellen) was 0.45 ± 0.20 (20/55) at baseline and significantly improved to 0.22 ± 0.13 (20/32) at 3-month follow-up (P-value: 0.007). At baseline, color photographs and fundus autofluorescence showed a pigment ring around the neovascular lesion in 6 eyes. A hyperreflective ring was visible on NIR in all eyes at 3-month follow-up. Color photographs showed a tessellated fundus appearance in 9 of the 10 eyes. Serial structural spectral-domain optical coherence tomography scans showed the gradual regression of the Type 2 lesions into a Type 1 pattern with envelopment by the retinal pigment epithelium. En face and cross-sectional optical coherence tomography angiography showed baseline subretinal flow patterns which, after treatment, exhibited reduced flow beneath an intact hyperreflective retinal pigment epithelium (RPE) band.

CONCLUSION

Pure Type 2 lesions are infrequent in nAMD, often leading to poor visual outcomes related to subretinal fibrosis. We describe an alternate regression pattern occurring in eyes with early Type 2 lesions treated with intravitreal anti-vascular endothelial growth factor therapy in which the neovascular tissue is enveloped by retinal pigment epithelium producing a Type 1 pattern. These eyes appear to have better visual outcomes than typically seen with Type 2 lesions related to reduced outer retinal damage.

Optical Coherence Tomography Angiography in Fovea Plana

Fovea plana is characterized by the anatomical absence of the foveal pit in eyes with normal visual function. The authors have analyzed three cases of idiopathic fovea plana with optical coherence tomography angiography (OCTA). As previously reported, the authors found the absence of a foveal avascular zone in all cases with OCTA; however, a preserved fusion of both the superficial and the deep capillary plexuses was found around the foveal center. This novel observation cannot be detected with conventional dye-based angiography, in which the deep capillary plexus is not visualized. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:670-673.].

THE SPECTRUM OF AMALRIC TRIANGULAR CHOROIDAL INFARCTION

PURPOSE

To describe the multimodal imaging findings, including optical coherence tomography angiography analysis, and spectrum of etiologies associated with Amalric triangular choroidal infarction.

METHODS

This study is a multicenter, retrospective, observational case series review of the clinical and multimodal imaging findings for six patients with Amalric triangular choroidal infarction.

RESULTS

Six patients (10 eyes) with Amalric triangular choroidal infarction were enrolled. Patients' ages ranged from 7 years to 90 years (mean 54 years, median 60 years). Wedge-shaped or triangular areas of choroidal ischemia were evident with fluorescein angiography in all patients and with indocyanine green angiography in one patient. Optical coherence tomography angiography demonstrated choriocapillaris flow reduction that colocalized with outer retinal structural abnormalities with en face optical coherence tomography and corresponded with the triangular zones of choroidal infarction identified with fluorescein angiography in one patient. Etiologies included giant cell arteritis in three cases: traumatic carotid dissection, traumatic retrobulbar hemorrhage, and malignant hypertension secondary to lupus-associated nephropathy.

CONCLUSION

The Amalric triangular syndrome of choroidal infarction can occur as a result of a spectrum of etiologies, especially giant cell arteritis. Infarction is evident on traditional angiography in all cases. Optical coherence tomography angiography may provide a simple noninvasive tool to evaluate choroidal ischemia.

Quantitative OCT Angiography of the Retinal Microvasculature and the Choriocapillaris in Myopic Eyes

Purpose

To study the retinal capillary microvasculature and the choriocapillaris (CC) in myopic eyes using quantitative optical coherence tomography angiography (OCTA) analysis.

Methods

Macular OCTA images of 3 × 3 mm were obtained using the RTVue-XR Avanti with AngioVue. Quantitative measurements of the retinal capillary microvascular layers and the CC were analyzed using en face projection images. Vessel density and fractal dimension of the superficial and deep retinal capillary plexus, and area and density of flow reduction in the CC were analyzed, quantified, and compared with an age-matched control group.

Results

Fifty eyes with myopia and 34 age-matched healthy eyes were included in this study. The vessel density and the vessel branching complexity using fractal dimension of the retinal capillary microvasculature were significantly lower in myopic eyes (P < 0.001 and P = 0.001). The total number of flow voids in the CC was lower (108.93 vs. 138.63, P = 0.001) but the total and average flow void area was significantly higher (total area 3.715 ± 0.257 vs. 3.596 ± 0.194 mm2, P = 0.026; average area 0.044 ± 0.029 vs. 0.028 ± 0.010 mm2, P = 0.002) compared with the healthy control group. Average choroidal thickness was lower in the myopic group versus the normal control cohort (123.538 ± 73.477 vs. 246.97 ± 41.745 μm, P < 0.05) and significantly reduced in eyes with lacquer cracks (LC) compared with myopic eyes without LC formation (P = 0.003). There was no correlation between choroidal thickness and quantitative parameters of the CC in the myopic eyes.

Conclusions

The density of the retinal capillary microvasculature is reduced and the area of flow deficit in the CC is increased in eyes with greater myopia. The relevance of microvascular alterations in the setting of myopia warrants further study.

Retinal Capillary Density and Foveal Avascular Zone Area Are Age-Dependent: Quantitative Analysis Using Optical Coherence Tomography Angiography

Purpose

The purpose of this study was to quantify retinal capillary density and the foveal avascular zone (FAZ) area in normal subjects according to age, using optical coherence tomography angiography (OCTA).

Methods

All eyes in this cross-sectional study underwent OCTA using RTVue XR Avanti with AngioVue. OCTA scans were analyzed and processed, and vessel density and FAZ dimensions were calculated.

Results

A total of 113 normal eyes from 70 subjects were included (30 males, 40 females; mean 48 ± 20 years of age). The mean vessel density and FAZ dimensions were significantly smaller in the superficial retinal capillary plexus (SCP) than in the deep retinal capillary plexus (DCP), using quantitative OCTA analysis (all P< 0.0001). With 3 × 3-mm scans, the mean vessel density was 13.431 ± 1.758 mm-1 in the SCP, 18.812 ± 1.796 mm-1 in the DCP, and 5.913 ± 1.308 mm-1 and 10.447 ± 1.262 mm-1 with 6 × 6-mm scans in the SCP and DCP, respectively. Mean FAZ areas were 0.289 ± 0.108 mm2 at the SCP and 0.614 ± 0.200 mm2 at the DCP. Age was a predictor of SCP and DCP vessel density and FAZ area in the SCP. Vessel density decreased 0.0393 mm-1 (0.26%) per year in the SCP and 0.0574 mm-1 (0.27%) per year in the DCP. FAZ areas increased 0.0014 mm2 (0.63%) and 0.0011 mm2 (0.20%) per year in the SCP and DCP, respectively.

Conclusions

SCP and DCP vessel density decreased with increasing age, while FAZ area increased with age. Normal age-matched measurements provide important standardized values that may facilitate management of retinal vascular disorders.

En Face Optical Coherence Tomography Analysis to Assess the Spectrum of Perivenular Ischemia and Paracentral Acute Middle Maculopathy in Retinal Vein Occlusion

PURPOSE

To assess the spectrum of perivenular ischemia in eyes with retinal vascular obstruction (typically central or hemicentral retinal vein obstruction) using en face optical coherence tomography (OCT).

DESIGN

Retrospective observational case series.

METHODS

Eyes with recent retinal vascular occlusion illustrating paracentral acute middle maculopathy (PAMM) in a perivenular fern-like pattern with en face OCT were evaluated in this study. Multimodal retinal imaging including en face OCT segmentation of the inner nuclear layer was performed in all patients. Color fundus photography and fluorescein angiography (FA) images were used to create a vascular overlay of the retinal veins vs the retinal arteries to map the distribution of PAMM with en face OCT analysis.

RESULTS

Multimodal retinal imaging was performed in 11 eyes with acute retinal vascular obstruction. While 7 eyes demonstrated obvious findings of retinal vein obstruction (5 with central and 2 with hemicentral retinal vein occlusion), 4 eyes were unremarkable at presentation. En face OCT analysis demonstrated a spectrum of perivenular PAMM illustrating a fern-like pattern with sparing of the periarteriolar area in all cases.

CONCLUSION

En face OCT may illustrate a remarkable perivenular pattern of PAMM in eyes with retinal vascular obstruction even in the absence of significant funduscopic findings. Perivenular PAMM with en face OCT demonstrates a wide spectrum of variation with narrow fern-like perivenular lesions at the mildest end and more diffuse lesions with only periarterial sparing at the most severe end of the spectrum. Arterial hypoperfusion secondary to outflow obstruction from a central retinal vein obstruction appears to be the most common cause of this presentation, although primary arterial hypoperfusion may also be an etiology.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF A29 BIRDSHOT CHORIORETINOPATHY COMPLICATED BY RETINAL NEOVASCULARIZATION

PURPOSE

To describe the quantitative optical coherence tomography angiography analysis of the superficial and deep retinal capillary plexus in a case of A29 birdshot chorioretinopathy (BCR) complicated by retinal neovascularization.

METHODS

Multimodal retinal imaging, including optical coherence tomography angiography with quantitated vessel density analysis of the superficial and deep retinal capillary plexus, was performed in a case of A29 BCR. Capillary density (mm) was defined as the total vessel length (mm) per area (mm).

RESULTS

A 39-year-old healthy white man presented with vitreous hemorrhage and retinal neovascularization at baseline. Clinical presentation was consistent with BCR and human leukocyte antigen testing confirmed A29 positivity. Optical coherence tomography angiography was performed 6 years after the diagnosis and revealed capillary density reduction in the superficial and especially in the deep retinal capillary plexus. Quantitative vessel density analysis was compared with the mean capillary density of 11 age-matched normal eyes and demonstrated 6% and 18% reduction of the superficial plexus in the right and left eyes of our patient, respectively. For the deep plexus, a reduction of 25% and 32% was found in the right and left eyes, respectively.

CONCLUSION

In this patient with BCR, capillary density reduction was most marked at the deep retinal capillary plexus level and may explain the development of retinal neovascularization in this case. Quantitative optical coherence tomography angiography may be a useful tool to study and to monitor retinal microvascular changes in patients with BCR and should be further explored as a biomarker of therapeutic response.

Subretinal Hyperreflective Material Imaged With Optical Coherence Tomography Angiography

PURPOSE

The range of subretinal hyperreflective material (SHRM) seen in macular disease includes type 2 macular neovascularization, fibrosis, exudation, vitelliform material, and hemorrhage. The prognostic significance of SHRM has been evaluated retrospectively in clinical trials, but discriminating SHRM subtypes traditionally requires multiple imaging modalities. The purpose of this study is to describe optical coherence tomography angiography (OCTA) flow characteristics and artifacts that might help to distinguish SHRM subtypes.

DESIGN

Validity analysis.

METHODS

Patients with age-related macular degeneration (AMD), myopia, pachychoroid disease, and macular dystrophy, manifesting SHRM on optical coherence tomography (OCT), were recruited. Clinical chart review and multimodal imaging established the SHRM subtype. All patients underwent OCTA. OCT and OCTA images were examined together for (1) intrinsic flow, (2) retinal projection onto the anterior SHRM surface (strong, weak, absent), (3) retinal projection through SHRM onto retinal pigment epithelium (RPE), and (4) masking of choriocapillaris flow.

RESULTS

Thirty-three eyes of 25 patients were included (type 2 neovascularization ×3; fibrosis ×4; exudation ×10; hemorrhage ×5; vitelliform ×17). Mean age per eye was 76 years (standard deviation: 12). Intrinsic flow was strongest in type 2 neovascularization. Subretinal fibrosis showed limited flow in residual large-caliber vessels and branches. Flow was not detected within foci of exudation, hemorrhage, or vitelliform lesions. Retina-SHRM surface projection was strongest onto smooth-surfaced SHRM and weaker onto exudation. Retinal projection was weakest on the surface of vitelliform lesions. Retina-RPE projection was masked by dense hemorrhage and vitelliform material. In compound SHRM, OCTA distinguished between vascular and avascular components.

CONCLUSION

Optical coherence tomography angiography can distinguish vascular from avascular SHRM components. OCTA artifacts may distinguish certain avascular SHRM components.

Optical Coherence Tomography Angiography of Type 1 Neovascularization in Age-Related Macular Degeneration

Age-related macular degeneration continues to be the leading cause of severe central vision loss in older adults of European descent. Optical coherence tomography angiography (OCT-A) enables more accurate identification of type 1 neovascularization in age-related macular degeneration than traditional fluorescein and indocyanine green angiographies. In addition, OCT-A facilitates the morphological classification of type 1 lesions, including features characteristic of early, mature, and fibrotic lesions. Vessel complex analysis, including lesion area and capillary density quantification, can also be readily measured and monitored over time. Performing this analysis following anti-vascular endothelial growth factor therapy may lead to a better understanding of the efficacies and responses to such treatments. Although some limitations currently exist, OCT-A is a promising imaging modality that could prove to have profound implications if incorporated into regular clinical practice.

Stability of Bevacizumab Divided in Multiple Doses for Intravitreal Injection

OBJECTIVE

To investigate the stability of bevacizumab in multiple doses divided from a single-use vial for intravitreal injection after storage at 4°C for up to six months and under drug transfer condition in tropical climate.

MATERIAL AND METHOD

Five syringes (0.1 mL, 2.5 mg) of bevacizumab were withdrawn each from five new bevacizumab single-use vials (4 mL, 100 mg) under sterile technique. The concentration of bevacizumab in each syringe was measured at two dilutions (2 x 10(6) and 4 x 10(6) fold) using enzyme-linked immunosorbent assay at baseline and after storage at 4°C for 1-, 3-, and 6-month. Each assay was performed at least twice. To simulate the drug transfer condition, bevacizumab was placed in a brown plastic bag and put in another transfer plastic bag with an ice cube for 30 minutes prior to the assay at 1-, 3-, and 6-month.

RESULTS

The concentrations of bevacizumab (mean ± standard deviation) at baseline, 1-, 3-, and 6-month were 26.24 ± 1.95, 25.43 ± 3.80, 27.87 ± 2.81, and 24.25 ± 2.00 mg/mL, respectively. The lowest lower limit of 95% confidence interval for the mean concentration was 23.32 mg/mL at 6-month storage, which was 89% of the mean baseline concentration and considered to be non-inferior to the baseline concentration.

CONCLUSION

Bevacizumab in a single-use vial could be divided into multiple small doses for intravitreal injection with sufficient stability when refrigerated at 4°C for up to six months and under the drug transfer condition in tropical climate.

Enhanced depth imaging spectral-domain optical coherence tomography of the choroid in Thai population

OBJECTIVE

To examine subfoveal choroidal thickness (SFCT) in Thai population using enhanced depth imaging spectral- domain optical coherence tomography (EDI-OCT) and to study its correlation with foveal retinal pigment epithelium thickness (FRPE), central neurosensory retinal thickness (CNRT), age, and refraction.

MATERIAL AND METHOD

Four hundred eighty eyes from 240 subjects without glaucoma, retinal, or choroidal diseases underwent scanning of the retina and choroid using EDI-OCT SFCT FRPE, and CNRT measurements were based on the 1:1 micron images and wereperformed by two independent observers. The reliability ofmeasurements between the observers was evaluated by intraclass correlation coefficient (ICC). The correlations of SFCT with FRPE, CNRT, age, and refractive error were analyzed

RESULTS

The mean age of the subjects was 36.22 years (range 20-81years). The means (95% reference intervals) of SFCT, CNRT andFRPE were 294.02 μm (137.14-450.90 μm), 174.22 μm (141.82-206.62 μm), and 41.94 μm (34.65-49.23 μm), respectively. SFCT and CNRThad excellent reliability between the two observers [ICC = 0.947 (95% CI, 0.918-0.963) and 0.929 (95% CI, 0.906-0.945), respectively], while FRPE showed good reliability [ICC = 0. 729 (95% CI, 0.637-0.793)]. SFCT had a low positive correlation with FRPE (r = 0.179, p<0. 0001) but not with CNRT (p = 0.317). SFCT showed a positive correlation with refraction (r = 0.338, p<0.0001) and a negative correlation with age (r = -0.166, p<0.0001). Regression analysis suggested that the SFCT decreased by 12.23 pm per one decade oflife and by 11.42 pm per one diopter of myopia.

CONCLUSION

Normal values of SFCT in Thai population were obtained SFCT significantly decreased with older age and higher myopia. SFCT was associated with FRPE, reflecting the same vascular supply of the choroid and retinal pigment epithelium. When measured with our technique based on the 1:1 micron images, the reliability ofSFCT measurement was very high despite highly morphologic inter-individual variations.

Stability of epitheliotrophic factors in autologous serum eye drops from chronic Stevens-Johnson syndrome dry eye compared to non-autoimmune dry eye

PURPOSE

To compare the concentrations of epitheliotrophic factors in autologous serum eye drops (ASE) prepared from sera of chronic Stevens-Johnson syndrome (SJS) patients with dry eyes to those prepared from non-autoimmune dry eye controls and to study the stability of the epitheliotrophic factors in different storage conditions.

METHODS

Twenty-percent ASE were prepared from 10 chronic SJS patients with dry eyes and 10 age-matched non-autoimmune dry eye controls. The concentrations of major epitheliotrophic factors comprising epidermal growth factor (EGF), transforming growth factor-beta1 (TGF-β1), transforming growth factor-beta2 (TGF-β2), and fibronectin in those ASE preparations were determined by enzyme-linked immunosorbent assay (ELISA) at baseline and after different storage conditions: at 4 °C for 1 week and 1 month; and at -20 °C for 1, 3 and 6 months.

RESULTS

There were no significant differences in the concentrations of EGF, TGF-β1, TGF-β2 and fibronectin in 20% ASE between the SJS and control groups (EGF: 176.9 ± 40.9 vs. 185.5 ± 36.9 pg/mL, TGF-β1: 9.5 ± 2.1 vs. 9.5 ± 1.9 ng/mL, TGF-β2: 55.3 ± 30.0 vs. 63.91 ± 45.6 pg/mL and fibronectin: 70.5 ± 20.2 vs. 62.2 ± 21.3 µg/mL, respectively). These factors were stable at 4 °C for up to 1 month. Storage at -20 °C for up to 6 months resulted in a slight decrease in TGF-β1 (SJS: from 9.5-8.4 ng/mL, p < 0.01 and control: from 9.5-8.1 ng/mL, p < 0.01).

CONCLUSIONS

The results suggested that the epitheliotrophic capacity of ASE from chronic SJS should be comparable to those from non-autoimmune dry eye patients, and that ASE should be sufficiently stable for up to 6 months, if stored properly at -20 °C.

Mitochondrial haplogroup background may influence Southeast Asian G11778A Leber hereditary optic neuropathy

PURPOSE

To investigate the role of mitochondrial DNA (mt DNA) background on the expression of Leber hereditary optic neuropathy (LHON) in Southeast Asian carriers of the G11778A mutation.

METHODS

Complete mtDNA sequences were analyzed from 53 unrelated Southeast Asian G11778A LHON pedigrees in Thailand and 105 normal Thai controls, and mtDNA haplogroups were determined. Clinical phenotypes were tested for association with mtDNA haplogroup, with adjustment for potential confounders such as sex and age at onset.

RESULTS

mtDNA subhaplogroup B was significantly associated with LHON. Follow-up analysis narrowed the association down to subhaplogroup B5a1 (P = 0.008). Survival analyses with Cox's proportional hazards modeling on 469 samples (91 affected and 378 unaffected), adjusted for sex and heteroplasmy, revealed that haplogroup B5a1 tended to increase the risk of visual loss, but the trend was not statistically significant. Conversely, haplogroup F, the second most common haplogroup in the control population, was the least frequent haplogroup in LHON. This negative association was narrowed down to subhaplogroup F1 (P = 0.00043), suggesting that haplogroup F1 confers a protective effect. The distributions of sex, age at onset and heteroplasmy were not significantly different among haplogroups.

CONCLUSIONS

The specific mtDNA background B5a1 was significantly associated with Southeast Asian G11778A LHON and appeared to modify the risk of visual loss.

Genome-wide linkage scan and association study of PARL to the expression of LHON families in Thailand

Leber hereditary optic neuropathy (LHON) is the most common mitochondrially inherited disease causing blindness, preferentially in young adult males. Most of the patients carry the G11778A mitochondrial DNA (mtDNA) mutation. However, the marked incomplete penetrance and the gender bias indicate some additional genetic and/or environmental factors to disease expression. Herein, we first conducted a genome-wide linkage scan with 400 microsatellite markers in 9 large Thai LHON G11778A pedigrees. Using an affecteds-only nonparametric linkage analysis, 4 regions on chromosomes 3, 12, 13 and 18 showed Zlr scores greater than 2 (P < 0.025), which is consistently significant across several linkage statistics. The most suggestive marker D3S1565 (Zlr > 2 in 10 of 16 allele sharing models tested) was then expanded to include the region 3q26.2-3q28 covering SLC7A14 (3q26.2), MFN1 (3q26.32), MRPL47 (3q26.33), MCCC1 (3q27.1), PARL (3q27.1) and OPA1 (3q28-q29). All of these candidate genes were selected from the Maestro database and had known to be localized in mitochondria. Sixty tag SNPs were genotyped in 86 cases, 211 of their relatives and 32 unrelated Thai controls, by multiplex-PCR-based Invader assay. Analyses using a powerful association testing tool that adjusts for relatedness (the M(QLS) statistic) showed the most evidence of association between two SNPs, rs3749446 and rs1402000 (located in PARL presenilins-associated rhomboid-like) and LHON expression (both P = 8.8 x 10(-5)). The mitochondrial PARL protease has been recently known to play a role with a dynamin-related OPA1 protein in preventing apoptotic events by slowing down the release of cytochrome c out of mitochondrial cristae junctions. Moreover, PARL is required to activate the intramembranous proteolyses resulting in the degradation of an accumulated pro-apoptotic protein in the outer mitochondrial membrane. Under these circumstances, variants of PARL are suggested to influence cell death by apoptosis which has long been believed to intrigue the neurodegeneration of LHON.

Transmission of heteroplasmic G11778A in extensive pedigrees of Thai Leber hereditary optic neuropathy

Leber hereditary optic neuropathy (LHON) is characterized by the acute or subacute bilateral painless loss of central vision, predominantly in young males. G11778A is the most common mitochondrial DNA mutation responsible for the disease. Thirty-seven percent of our LHON pedigrees (which is a much higher prevalence than that generally found) carried heteroplasmic G11778A. Analyses of four large Thai LHON pedigrees spanning four to six generations strongly suggested that the transmission of the heteroplasmic G11778A mutation is under selective pressure in favour of the mutated allele and that heteroplasmy influences the disease expression.

The unique characteristics of Thai Leber hereditary optic neuropathy: analysis of 30 G11778A pedigrees

Leber hereditary optic neuropathy (LHON) is characterized by acute or subacute bilateral visual loss, and affects mostly young males. The most common mitochondrial DNA mutation responsible for LHON worldwide is G11778A. Despite different genetic backgrounds, which are believed to influence the disease expression, most features of LHON are quite common in different populations. However, there seem to be a few ethnic-specific differences. Analyses of our 30 G11778A LHON pedigrees in Thailand showed some characteristics different from those of Caucasians and Japanese. In particular, our pedigrees showed a lower male to female ratio of affected persons (2.6:1) and much higher prevalence of G11778A blood heteroplasmy (37% of the pedigrees contained at least one heteroplasmic G11778A individual). Heteroplasmicity seemed to influence disease manifestation in our patients but did not appear to alter the onset of the disease. The estimated overall penetrance of our G11778A LHON population was 37% for males and 13% for females. When each of our large pedigrees were considered separately, disease penetration varied from 9 to 45% between the pedigrees, and also varied between different branches of the same large pedigree. Survival analysis showed that the secondary LHON mutations G3316A and C3497T had a synergistic deleterious effect with the G11778A mutation, accelerating the onset of the disease in our patients.

Proportion of 11778 mutant mitochondrial DNA and clinical expression in a thai population with leber hereditary optic neuropathy

BACKGROUND

The proportion of mutant mtDNA in blood has been found to correlate with the frequency of visual loss in cases with mtDNA mutations associated with Leber hereditary optic neuropathy (LHON), especially in men. We sought to determine this correlation in a Thai population of LHON.

METHODS

Densitometric quantification of blood mtDNA with the 11,778 LHON mutation in 137 symptomatic cases and their asymptomatic maternal relatives in 30 Asian pedigree families was performed. Asymptomatic maternal relatives under the age of 16 years were excluded. The visual outcome in symptomatic cases with homoplasmy and heteroplasmy was compared.

RESULTS

Heteroplasmy was detected in eight (12.9%) symptomatic and 30 (40%) asymptomatic individuals. The quantification of blood mutant mtDNA in the eight symptomatic cases ranged from 44% to 93% (mean=75%). The visual outcome of the cases with heteroplasmy was not different from that of cases with homoplasmy. There was a correlation between the proportion of mutant mtDNA and the likelihood of visual loss.

CONCLUSIONS

The prevalence of heteroplasmy among pedigrees of the 11,778 LHON mutation in Thailand was similar to that of other Asian populations and may be greater than in 11,778 LHON pedigrees from white backgrounds. The proportion of mutated mtDNA correlated with visual loss, but the effect of heteroplasmy on clinical expression seemed not to relate to gender.