Hagfish genome elucidates vertebrate whole-genome duplication events and their evolutionary consequences.

Polyploidy or whole-genome duplication (WGD) is a major event that drastically reshapes genome architecture and is often assumed to be causally associated with organismal innovations and radiations. The 2R hypothesis suggests that two WGD events (1R and 2R) occurred during early vertebrate evolution. However, the timing of the 2R event relative to the divergence of gnathostomes (jawed vertebrates) and cyclostomes (jawless hagfishes and lampreys) is unresolved and whether these WGD events underlie vertebrate phenotypic diversification remains elusive. Here we present the genome of the inshore hagfish, Eptatretus burgeri. Through comparative analysis with lamprey and gnathostome genomes, we reconstruct the early events in cyclostome genome evolution, leveraging insights into the ancestral vertebrate genome. Genome-wide synteny and phylogenetic analyses support a scenario in which 1R occurred in the vertebrate stem-lineage during the early Cambrian, and 2R occurred in the gnathostome stem-lineage, maximally in the late Cambrian-earliest Ordovician, after its divergence from cyclostomes. We find that the genome of stem-cyclostomes experienced an additional independent genome triplication. Functional genomic and morphospace analyses demonstrate that WGD events generally contribute to developmental evolution with similar changes in the regulatory genome of both vertebrate groups. However, appreciable morphological diversification occurred only in the gnathostome but not in the cyclostome lineage, calling into question the general expectation that WGDs lead to leaps of bodyplan complexity.

Evolution of two distinct variable lymphocyte receptors in lampreys: VLRD and VLRE.

Jawless vertebrates possess an alternative adaptive immune system in which antigens are recognized by variable lymphocyte receptors (VLRs) generated by combinatorial assembly of leucine-rich repeat (LRR) cassettes. Three types of receptors, VLRA, VLRB, and VLRC, have been previously identified. VLRA- and VLRC-expressing cells are T cell-like, whereas VLRB-expressing cells are B cell-like. Here, we report two types of VLRs in lampreys, VLRD and VLRE, phylogenetically related to VLRA and VLRC. The germline VLRD and VLRE genes are flanked by 39 LRR cassettes used in the assembly of mature VLRD and VLRE, with cassettes from chromosomes containing the VLRA and VLRC genes also contributing to VLRD and VLRE assemblies. VLRD and VLRE transcription is highest in the triple-negative (VLRA-/VLRB-/VLRC-) population of lymphocytes, albeit also detectable in VLRA+ and VLRC+ populations. Tissue distribution studies suggest that lamprey VLRD+ and VLRE+ lymphocytes comprise T-like sublineages of cells.

Evolution of variable lymphocyte receptor B antibody loci in jawless vertebrates.

Three types of variable lymphocyte receptor (VLR) genes, VLRA, VLRB, and VLRC, encode antigen recognition receptors in the extant jawless vertebrates, lampreys and hagfish. The somatically diversified repertoires of these VLRs are generated by serial stepwise copying of leucine-rich repeat (LRR) sequences into an incomplete germline VLR gene. Lymphocytes that express VLRA or VLRC are T cell-like, while VLRB-expressing cells are B cell-like. Here, we analyze the composition of the VLRB locus in different jawless vertebrates to elucidate its configuration and evolutionary modification. The incomplete germline VLRB genes of two hagfish species contain short noncoding intervening sequences, whereas germline VLRB genes in six representative lamprey species have much longer intervening sequences that exhibit notable genomic variation. Genomic clusters of potential LRR cassette donors, fragments of which are copied to complete VLRB gene assembly, are identified in Japanese lamprey and sea lamprey. In the sea lamprey, 428 LRR cassettes are located in five clusters spread over a total of 1.7 Mbp of chromosomal DNA. Preferential usage of the different donor cassettes for VLRB assemblage is characterized in our analysis, which reveals evolutionary modifications of the lamprey VLRB genes, elucidates the organization of the complex VLRB locus, and provides a comprehensive catalog of donor VLRB cassettes in sea lamprey and Japanese lamprey.

Interocular symmetry of the foveal avascular zone area in healthy eyes: a swept-source optical coherence tomography angiography study.

PURPOSE: To determine the presence or absence of interocular differences in the foveal avascular zone (FAZ) area in healthy eyes. STUDY DESIGN: Cross-sectional study. METHODS: We examined 236 healthy eyes of 118 consecutive subjects (mean age, 39.1 ± 18.9 years). We used swept-source optical coherence tomography angiography (OCTA) images of the FAZ to measure its area from both the superficial capillary plexus (SCP-FAZ) and the whole retinal capillary plexus (WCP-FAZ). We also investigated the relationship between interocular differences in SCP-FAZ and other factors such as: axial length, spherical equivalent, central retinal thickness, and retinal vascular density. RESULTS: There was no significant difference in the FAZ area between the right and left eyes in either the SCP-FAZ (P = 0.61) or WCP-FAZ (P = 0.80), and the FAZ areas of both eyes showed significant positive correlations (SCP-FAZ; P < 0.001, R2 = 0.884, WCP-FAZ; P < 0.001, R2 = 0.856). Bland-Altman plots showed that the mean interocular difference in SCP-FAZ area was 0.002 ± 0.037 mm2 (95% confidence interval, -0.072-0.075 mm2), and in the WCP-FAZ area, 0.050 ± 0.044 mm2 (95% confidence interval, -0.036-0.137 mm2). Multivariate regression analysis showed that none of the investigated factors were significantly associated with interocular differences in SCP-FAZ (P = 0.61, R2 = 0.138). CONCLUSIONS: There was no significant interocular difference in SCP- and WCP-FAZ areas in healthy eyes. The normal range of values for interocular difference in SCP-FAZ area was 0.002 ± 0.037 mm2 and in the WCP-FAZ area, 0.050 ± 0.044 mm2.

ADVERSE EFFECT OF MACULAR INTRARETINAL HEMORRHAGE ON THE PROGNOSIS OF SUBMACULAR HEMORRHAGE DUE TO RETINAL ARTERIAL MACROANEURYSM RUPTURE.

PURPOSE: To investigate the clinical course of submacular hemorrhage associated with ruptured retinal arterial macroaneurysm using swept-source optical coherence tomography. METHODS: This study included 23 eyes of 23 consecutive patients diagnosed with submacular hemorrhage associated with ruptured retinal arterial macroaneurysm. Cases underwent displacement of submacular hemorrhage (vitrectomy + subretinal injection of tissue plasminogen activator + air tamponade) and were followed up for 6 months after surgery. Localization of the preoperative hemorrhage and its effect on preoperative and postoperative best-corrected visual acuity, central retinal thickness, and continuity of the ellipsoid zone were measured. RESULTS: Macular intraretinal hemorrhage (IRH) was observed in 17 eyes (73.9%, IRH [+] group) and was not observed in 6 eyes (26.1%, IRH [-] group). The IRH (+) group showed worse postoperative best-corrected visual acuity values compared with the IRH (-) group (0.89 ± 0.47 in logarithm of the minimal angle of resolution units, Snellen equivalent 20/155 and 0.16 ± 0.23, 20/29, respectively; P < 0.01), smaller central retinal thickness values (97.7 ± 53.5 µm, 173.0 ± 32.3 µm, respectively; P < 0.01), and a higher rate of ellipsoid zone disruption (100%, 33.3%, respectively; P < 0.01). CONCLUSION: Patients with preoperative macular IRH showed lower postoperative visual acuity and worse macular contour after submacular hemorrhage displacement compared with patients without macular IRH.

EN FACE IMAGE-BASED ANALYSIS OF RETINAL TRACTION CAUSED BY EPIRETINAL MEMBRANE AND ITS RELATIONSHIP WITH VISUAL FUNCTIONS.

PURPOSE: To evaluate the relationship between retinal traction caused by epiretinal membrane and visual functions. METHODS: In this institutional study, en face swept-source optical coherence tomography images of 141 eyes of 130 patients with epiretinal membrane were analyzed to investigate maximum depth of retinal folds, which represents retinal traction strength and the distribution pattern of retinal folds. We investigated the relationships between the maximum depth and distribution pattern of retinal folds and visual functions as well as the effects of membrane peeling. RESULTS: Maximum retinal fold depth was significantly correlated with the metamorphopsia score (P < 0.001). Fifteen eyes showed retinal folds radially extending from the macular epiretinal membrane (radiating folds group), whereas 126 eyes showed a multidirectional pattern of retinal folds (multidirectional folds group). The radiating folds group showed a significantly lower metamorphopsia score (P = 0.014). Multiple regression analysis revealed that the metamorphopsia score was significantly related to maximum retinal fold depth (P = 0.003), distribution pattern (P = 0.015), and central retinal thickness (P < 0.001). One month after membrane peeling, parafoveal retinal folds resolved completely in all cases, and both visual acuity (P < 0.001) and average metamorphopsia score (P = 0.036) were significantly improved. CONCLUSION: Both the strength and the distribution pattern of retinal traction are significantly related to metamorphopsia in epiretinal membrane patients.

Ancient BCMA-like Genes Herald B Cell Regulation in Lampreys.

The TNF superfamily ligands BAFF and APRIL interact with three receptors, BAFFR, BCMA, and TACI, to play discrete and crucial roles in regulating B cell selection and homeostasis in mammals. The interactions between these ligands and receptors are both specific and redundant: BAFFR binds BAFF, whereas BCMA and TACI bind to either BAFF or APRIL. In a previous phylogenetic inquiry, we identified and characterized a BAFF-like gene in lampreys, which, with hagfish, are the only extant jawless vertebrates, both of which have B-like and T-like lymphocytes. To gain insight into lymphocyte regulation in jawless vertebrates, in this study we identified two BCMA-like genes in lampreys, BCMAL1 and BCMAL2, which were found to be preferentially expressed by B-like lymphocytes. In vitro analyses indicated that the lamprey BAFF-like protein can bind to a BCMA-like receptor Ig fusion protein and to both BCMAL1- and BCMAL2-transfected cells. Discriminating regulatory roles for the two BCMA-like molecules are suggested by their differential expression before and after activation of the B-like lymphocytes in lampreys. Our composite results imply that BAFF-based mechanisms for B cell regulation evolved before the divergence of jawed and jawless vertebrates.

Physiological Properties of Photoautotrophic Microalgae and Cyanobacteria Relevant to Industrial Biomass Production.

Photoautotrophic mass culture of microalgae is currently under investigation for social implementation, since such organisms are anticipated to be resources of alternative fuels and materials for reducing global warming. Production scale-up of culture systems and economy balance are great barriers for practical usage. In order to develop new culture systems such as attachment on solid surfaces or biofilms, we investigated various characteristics of photosynthesis in Chlorella, not only in liquid but also on filter membranes. In aquatic cultures, the photosynthetic rate was almost the same as the specific exponential growth rate at over 32 °C, suggesting that highly efficient cell growth was achieved at that temperature. The algal cells could fix about 50 mmol carbons per mole photons, at cloudy-day-level light intensities, which result to produce 1.2 g dry cell weight in calculation. Moreover, Chlorella could grow on a membrane surface at almost the same rate as in liquid. Similar tolerance to water deficiency was observed in a cyanobacterium, Synechocystis, in which gene expression responded in 30 min after the stress. Such a tolerance was also observed in other species of microalgae and cyanobacteria in photosynthesis.

BCL6 Evolved to Enable Stress Tolerance in Vertebrates and Is Broadly Required by Cancer Cells to Adapt to Stress.

Several lines of evidence link the canonical oncogene BCL6 to stress response. Here we demonstrate that BCL6 evolved in vertebrates as a component of the HSF1-driven stress response, which has been co-opted by the immune system to support germinal center formation and may have been decisive in the convergent evolution of humoral immunity in jawless and jawed vertebrates. We find that the highly conserved BTB corepressor binding site of BCL6 mediates stress adaptation across vertebrates. We demonstrate that pan-cancer cells hijack this stress tolerance mechanism to aberrantly express BCL6. Targeting the BCL6 BTB domain in cancer cells induces apoptosis and increases susceptibility to repeated doses of cytotoxic therapy. The chemosensitization effect upon BCL6 BTB inhibition is dependent on the derepression of TOX, implicating modulation of DNA repair as a downstream mechanism. Collectively, these data suggest a form of adaptive nononcogene addiction rooted in the natural selection of BCL6 during vertebrate evolution. SIGNIFICANCE: We demonstrate that HSF1 drives BCL6 expression to enable stress tolerance in vertebrates. We identify an HSF1-BCL6-TOX stress axis that is required by cancer cells to tolerate exposure to cytotoxic agents and points toward BCL6-targeted therapy as a way to more effectively kill a wide variety of solid tumors.This article is highlighted in the In This Issue feature, p. 565.

Cancer Immunity and Gene Expression Data: A Quick Tool for Immunophenotype Evaluation.

The rapid advancement of next generation sequencing technology has resulted in accumulation of many datasets in cancer clinical and research laboratories, many of which do not have bioinformaticians. Xu and colleagues developed a user-friendly web-based tool to define the tumor immunophenotype among patients with cancer. By uploading user-defined datasets on the web, it can systematically track, analyze, and visualize the status of anticancer immune activity and the proportion of tumor-infiltrating immune cells. This tool can help immunologists and clinical researchers to perform quick, efficient, and comprehensive analysis of the tumor immunophenotype.See related article by Xu et al., p. 6575.

Embedding of lamellar hole-associated epiretinal proliferation combined with internal limiting membrane inversion for the treatment of lamellar macular hole: a case report.

BACKGROUND: We recently reported that lamellar macular hole (LMH) with lamellar hole-associated epiretinal proliferation (LHEP) can be effectively treated by embedding the LHEP into the retinal cleavage to improve foveal contour and visual acuity. Here, we report a case of LMH with LHEP for which we performed embedding of the LHEP combined with internal limiting membrane (ILM) inversion. We then evaluated the effects of this surgery on macular morphology and visual functions. CASE PRESENTATION: A 62-year-old man presented with visual disturbance (20/29) and metamorphopsia in his right eye. B-scan optical coherence tomography (OCT) imaging revealed the presence of both partial-thickness defect of the macula with degenerative retinal cleavage and LHEP at the surface of the retina. En face OCT imaging showed the absence of retinal fold. We performed phacoemulsification with intraocular lens implantation, vitrectomy, embedding of LHEP into the retinal cleavage, and ILM inversion. Three months after the surgery, both foveal contour and visual acuity (20/20) were improved and metamorphopsia was reduced. CONCLUSION: Embedding of the LHEP combined with ILM inversion may be an effective treatment for LMH with LHEP.

Impact of Polyp Regression on 2-year Outcomes of Intravitreal Aflibercept Injections: A Treat-and-Extend Regimen for Polypoidal Choroidal Vasculopathy.

We conducted intravitreal aflibercept injections (IVAs) for 37 Japanese patients (28 males, 9 females, mean age 73.4 years) with polypoidal choroidal vasculopathy (PCV), with a treat-and-extend regimen (TER). We evaluated the impact of polyp regression after a loading dose (2-mg IVA 1×/month for 3 months) on the patients' 2-year treatment outcomes. Thirty-seven eyes were treated with IVA by a TER for 2 years. We divided the patients into 2 groups based on their polyp status after the loading dose: polyp regression (PR+) (n=19) and no polyp regression (PR-) (n=18). We compared the groups' best-corrected visual acuity (BCVA), central retinal thickness (CRT), recurrence rate, total number of injections, and final treatment interval. Both the BCVA and CRT were significantly improved by the treatment in both groups, with no between-group difference in the amount of change (p=0.769). In the polyp regression (+) group, recurrence was significantly less common (p=0.03), the mean total number of injections was significantly lower (p=0.013), and the mean treatment interval was significantly longer (0.042). Regarding the 2-year outcomes for PCV, the eyes with post-loading-dose polyp regression demonstrated less frequent recurrence and required fewer numbers of injections compared to the eyes without polyp regression.

Results of a Treat-and-Eextend Regimen of Intravitreal Ranibizumab Injection for Macular Edema due to Branch Retinal Vein Occlusion.

To investigate the effectiveness of a treat-and-extend regimen (TAE) of intravitreal ranibizumab injections (IVR) for macular edema (ME) due to branch retinal vein occlusion (BRVO). We retrospectively examined 35 eyes of 35 patients with ME due to BRVO who underwent TAE for 1 year. Patients whose treatment interval extended to 12 weeks were switched to a pro re nata regimen (PRN; TAE to PRN group), while TAE was continued for patients whose treatment interval was less than 12 weeks (continued TAE group). Changes in best-corrected visual acuity (BCVA), central retinal thickness (CRT), and predictive factors for inclusion in the TAE to PRN group were analyzed. BCVA and CRT both improved significantly at 1 year compared with baseline (p<0.001). Sixteen eyes (45.7%) were included in the TAE to PRN group, while 19 eyes (54.3%) were included in the continued TAE group. BCVA in the TAE to PRN group was significantly better than that in the continued TAE group at 1 year (p=0.047). BCVA at baseline and macular BRVO were significant predictive factors for inclusion in the TAE to PRN group. TAE was effective for improving BCVA and CRT. The TAE to PRN group showed significantly better prognosis.

Traumatic Globe Luxation with Complete Optic Nerve Transection Caused by Heavy Object Compression.

Traumatic eyeball luxation is a rare clinical condition with a dramatic presentation. Here, we describe a unique case of traumatic globe luxation and complete optic nerve transection caused by heavy object compression. A 45-year-old male automobile mechanic was injured when a truck slipped from its supports, crushing his head and face. On arrival, his right eyeball was obviously displaced anteriorly and he had no light perception. Computed tomography revealed complex frontal bone and facial fractures with underlying brain contusion in addition to complete transection of the right optic nerve. The patient was successfully treated using a multidisciplinary approach.

Issues with the Specificity of Immunological Reagents for NLRP3: Implications for Age-related Macular Degeneration.

Contradictory data have been presented regarding the implication of the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome in age-related macular degeneration (AMD), the leading cause of vision loss in the Western world. Recognizing that antibody specificity may explain this discrepancy and in line with recent National Institutes of Health (NIH) guidelines requiring authentication of key biological resources, the specificity of anti-NLRP3 antibodies was assessed to elucidate whether non-immune RPE cells express NLRP3. Using validated resources, NLRP3 was not detected in human primary or human established RPE cell lines under multiple inflammasome-priming conditions, including purported NLRP3 stimuli in RPE such as DICER1 deletion and Alu RNA transfection. Furthermore, NLRP3 was below detection limits in ex vivo macular RPE from AMD patients, as well as in human induced pluripotent stem cell (hiPSC)-derived RPE from patients with overactive NLRP3 syndrome (Chronic infantile neurologic cutaneous and articulate, CINCA syndrome). Evidence presented in this study provides new data regarding the interpretation of published results reporting NLRP3 expression and upregulation in RPE and addresses the role that this inflammasome plays in AMD pathogenesis.

Assessment of Lamellar Macular Hole and Macular Pseudohole With a Combination of En Face and Radial B-scan Optical Coherence Tomography Imaging.

PURPOSE: To investigate lamellar macular hole (LMH) and macular pseudohole (MPH) using a combination of en face and radial B-scan OCT. DESIGN: Retrospective observational case series. METHODS: Setting: Institutional study. PATIENT POPULATION: En face and radial B-scan OCT images of 63 eyes of 60 patients diagnosed with LMH or MPH based on an international classification were reviewed. OBSERVATION PROCEDURES: Cases were classified using en face images based on the presence/absence of epiretinal membrane (ERM), retinal folds, parafoveal epicenter of contractile ERM (PEC-ERM), and retinal cleavage. We compared the en face imaging-based classification system with the international classification system using radial B-scan images. We quantitatively evaluated visual function and macular morphology. MAIN OUTCOME MEASURES: Characterization of multimodal OCT-based subtypes of LMH and MPH. RESULTS: All cases showed ERM and were classified into 4 groups. In the first group, which lacked retinal folds and showed significantly lower visual acuity than the other groups, 81% of eyes had degenerative LMH. In the second group, which lacked PEC-ERM and retinal cleavage and showed significantly lower retinal fold depth, all eyes had MPH. The third group, in which 95% of eyes had symmetric tractional LMH, included eyes with retinal cleavage but without PEC-ERM, and this group showed higher circularity of the foveal aperture and cleavage area than the group with both these features, in which all eyes had asymmetric tractional LMH. CONCLUSIONS: Multimodal OCT enables classification of LMH and MPH based on pathologic conditions. Retinal traction in particular may be useful for determining treatment methods.

The influence of subretinal injection pressure on the microstructure of the monkey retina.

PURPOSE: To investigate the influence of subretinal injection pressure on the microstructure of the retina in a monkey model. METHODS: After vitrectomy, balanced salt solution was injected subretinally into one eye each of four cynomolgus monkeys while controlling the injection pressure. Initially, a pressure of 2 psi was used, and this was gradually increased to determine the minimum required pressure. Subsequent injections were performed at two pressures: minimum (n = 13) and high (n = 6). To compare the influence of these injection pressures on retinal structure, optical coherence tomography (OCT) was performed before surgery and every week afterwards. The monkeys were euthanized and their eyes were enucleated at 1 or 6 weeks after the injections. The eyes were processed for light microscopy and transmission electron microscopy (TEM) as well as for TdT-mediated dUTP nick end labeling. RESULTS: The minimum pressure required to perform subretinal injection was 6 psi. After injection at this pressure, both OCT and microscopy showed that the retinal structure was well-preserved throughout the experimental period at all injection sites. Conversely, after injection at high pressure (20 psi) OCT images at all injection sites showed disruption of the ellipsoid zone (EZ) after 1 week. Microscopy indicated damage to the photoreceptor outer segment (OS) and stratification of the retinal pigment epithelium (RPE). After 6 weeks, OCT demonstrated that the EZ had become continuous and TEM confirmed that the OS and RPE had recovered. Photoreceptor apoptosis was absent after subretinal injection at both pressures. CONCLUSIONS: The retinal damage caused by subretinal injection increases depending on pressure, indicating that clinicians should perform subretinal injection at pressures as low as possible to ensure safety.

Evolution of Alternative Adaptive Immune Systems in Vertebrates.

Adaptive immunity in jawless fishes is based on antigen recognition by three types of variable lymphocyte receptors (VLRs) composed of variable leucine-rich repeats, which are differentially expressed by two T-like lymphocyte lineages and one B-like lymphocyte lineage. The T-like cells express either VLRAs or VLRCs of yet undefined antigen specificity, whereas the VLRB antibodies secreted by B-like cells bind proteinaceous and carbohydrate antigens. The incomplete VLR germline genes are assembled into functional units by a gene conversion-like mechanism that employs flanking variable leucine-rich repeat sequences as templates in association with lineage-specific expression of cytidine deaminases. B-like cells develop in the hematopoietic typhlosole and kidneys, whereas T-like cells develop in the thymoid, a thymus-equivalent region at the gill fold tips. Thus, the dichotomy between T-like and B-like cells and the presence of dedicated lymphopoietic tissues emerge as ancestral vertebrate features, whereas the somatic diversification of structurally distinct antigen receptor genes evolved independently in jawless and jawed vertebrates.

A novel cell exclusion zone assay with a barrier made from room temperature vulcanizing silicone rubber.

OBJECTIVE: To examine the usefulness of room temperature vulcanizing (RTV) silicone rubber as a barrier material for cell exclusion zone assays. METHODS: We created barriers using three types of RTV silicone rubber with differing viscosities. We then assessed the adherence of these barriers to culture dishes and their ease of removal from the dishes. We tested the effect of the newly created barriers on the extracellular matrix (ECM) protein fibronectin by attaching and then removing them from fibronectin-coated culture dishes. We also conducted cell exclusion zone assays with MIO-M1 cells using this new barrier in order to measure cell migration. We used real time reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical staining to measure the effect of fibronectin on MIO-M1 cell migration and the effect of migration (with fibronectin coating) on basic fibroblast growth factor (bFGF) expression in MIO-M1 cells. RESULTS: Of the three types of RTV silicon rubber tested, KE-3495-T was the best in terms of adherence to the dish and ease of removal from the dish. When barrier attachment and removal tests were performed, this rubber type did not have an effect on the fibronectin that coated the dish. In the cell exclusion assay, removal of the barrier revealed that a cell-free area with a distinct margin had been created, which allowed us to conduct a quantitative assessment of migration. Fibronectin significantly promoted the migration of MIO-M1 cells (P = 0.02). In addition, both real time RT-PCR and immunohistological staining indicated that bFGF expression in migrating MIO-M1 cells was significantly higher than that in non-migrating cells (P = 0.03). CONCLUSIONS: RTV silicone rubber can be used to create an effective barrier in cell exclusion zone assays and allows simple and low-cost multi-parametric analysis of cell migration.

Factors affecting foveal avascular zone in healthy eyes: An examination using swept-source optical coherence tomography angiography.

OBJECTIVE: To examine factors affecting foveal avascular zone (FAZ) area in healthy eyes using swept-source optical coherence tomography angiography (OCTA). METHODS: This prospective, cross-sectional study included 144 eyes of 144 individuals (77 women, 67 men) with a best corrected visual acuity of at least 20/20 and no history of ocular disorders. The area of the superficial FAZ was assessed using OCTA. Age, gender, central retinal thickness (CRT), retinal vascular density, refractive error, and axial length were examined to determine associations with FAZ area. RESULTS: The mean age of the subjects was 42.1 ± 20.2 years (range: 10-79 years). The mean FAZ area was 0.32 ± 0.11 mm2, while the mean retinal vascular density was 35.53 ± 0.92%. Multivariate regression analysis was performed using FAZ area as the dependent variable and age, gender, CRT, retinal vascular density, refractive error, and axial length as independent variables. The results of this analysis demonstrate that CRT and retinal vascular density were significantly associated with FAZ area in our sample (P < 0.001, R2 = 0.425). Age, gender, refractive error, and axial length were not significantly correlated with FAZ area, while CRT and retinal vascular density were negatively correlated with FAZ area (CRT: P < 0.001, R2 = 0.356; retinal vascular density: P < 0.001, R2 = 0.189). CONCLUSIONS: OCTA results suggest that CRT and retinal vascular density negatively affect FAZ area in healthy eyes.