Macular Microvasculature in High Myopia without Pathologic Changes: An Optical Coherence Tomography Angiography Study

Axial length, more than aging, decreases the thickness and superficial vessel density of retinal nerve fiber layer in non-glaucomatous eyes

PURPOSE

This study seeks to build a normative database for the vessel density of the superficial retina (SVD) and evaluate how changes and trends in the retinal microvasculature may be influenced by age and axial length (AL) in non-glaucomatous eyes, as measured with optical coherence tomography angiography (OCTA).

METHODS

We included 500 eyes of 290 healthy subjects visiting a county hospital. Each participant underwent comprehensive ophthalmological examinations and OCTA to measure the SVD and thickness of the macular and peripapillary areas. To analyze correlations between SVD and age or AL, multivariable linear regression models with generalized estimating equations were applied.

RESULTS

Age was negatively correlated with the SVD of the superior, central, and inferior macular areas and the superior peripapillary area, with a decrease rate of 1.06%, 1.36%, 0.84%, and 0.66% per decade, respectively. However, inferior peripapillary SVD showed no significant correlation with age. AL was negatively correlated with the SVD of the inferior macular area and the superior and inferior peripapillary areas, with coefficients of -0.522%/mm, -0.733%/mm, and -0.664%/mm, respectively. AL was also negatively correlated with the thickness of the retinal nerve fiber layer and inferior ganglion cell complex (p = 0.004).

CONCLUSION

Age and AL were the two main factors affecting changes in SVD. Furthermore, AL, a relative term to represent the degree of myopia, had a greater effect than age and showed a more significant effect on thickness than on SVD. This relationship has important implications because myopia is a significant issue in modern cities.

Observation of the effect of posterior scleral reinforcement combined with orthokeratology and 0.01% atropine in the treatment of congenital myopia: a case report

BACKGROUND

Myopia has recently emerged as a significant threat to global public health. The high and pathological myopia in children and adolescents could result in irreversible damage to eye tissues and severe impairment of visual function without timely control. Posterior scleral reinforcement (PSR) can effectively control the progression of high myopia by limiting posterior scleral expansion, improving retrobulbar vascular perfusion, thereby stabilizing the axial length and refraction of the eye. Moreover, orthokeratology and low concentrations of atropine are also effective in slowing myopia progression.

CASE PRESENTATION

A female child was diagnosed with binocular congenital myopia and amblyopia at the age of 3 and the patient's vision had never been rectified with spectacles at the first consultation. The patient's ophthalmological findings suggested, high refractive error with low best corrected visual acuity, longer axial length beyond the standard level of her age, and fundus examination suggesting posterior scleral staphyloma with weakened hemodynamics of the posterior ciliary artery. Thereby, PSR was performed to improve fundus health and the combination of orthokeratology and 0.01% atropine were performed to control the development of myopia. Following up to 8 years of clinical treatment and observations, the progression of myopia could be well controlled and fundus health was stable.

CONCLUSION

In this report, 8-year of clinical observation indicated that PSR could improve choroidal thickness and hemodynamic parameters of the retrobulbar vessels, postoperative orthokeratology combined with 0.01% atropine treatment strategy may be a good choice for myopia control effectively.

Correlation between refractive errors and ocular biometric parameters in children and adolescents: a systematic review and meta-analysis

BACKGROUND

Refractive errors are one of the most common ocular conditions among children and adolescents, with myopia showing an increasing prevalence and early onset in this population. Recent studies have identified a correlation between refractive errors and ocular biometric parameters.

METHODS

A systematic search was conducted in electronic databases including PubMed, EMBASE, Cochrane Library, Web of Science, and Medline from January 1, 2012, to May 1, 2023. Various ocular biometric parameters were summarized under different refractive states, including axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), corneal curvature (CC), Corneal curvature radius (CR),axial length-to-corneal radius ratio (AL/CR ratio), choroidal thickness (ChT), retinal thickness (RT), retinal nerve fiber layer thickness (RNFL), and retinal blood density (VD). The differences in these parameters among different refractive states were analyzed using Stata software with fixed or random-effects models, taking into account the assessed heterogeneity level.

RESULTS

This meta-analysis included a total of 69 studies involving 128,178 eyes, including 48,795 emmetropic eyes, 60,691 myopic eyes, 13,983 hyperopic eyes, 2,040 low myopic eyes, 1,201 moderate myopic eyes, and 1,468 high myopic eyes. The results of our study demonstrated that, compared to the control group (emmetropic group), the myopic group and low, moderate, and high myopic groups showed significant increases in AL, AL/CR ratio, and ACD, while the hyperopic group exhibited significant decreases. Compared to the control group, the myopic group had a significantly increase for CC, while CR, CCT, perifoveal RT, subfoveal ChT, foveal ChT, parafoveal ChT, perifoveal (except nasal) ChT, and pRNFL (except temporal) significantly decreased. Compared to the control group, the hyperopic group had a significantly increase for subfoveal ChT, foveal ChT, parafoveal ChT, perifoveal ChT, and nasal pRNFL. Compared to the control group, the low and moderate myopic groups had a significantly decreases for the CCT, parafoveal RT (except nasal), perifoveal RT (except nasal), and pRNFL (except superior and temporal). Compared to the control group, the high myopic group had a significantly increase for CR, while LT, perifoveal ChT (except nasal), parafoveal RT, perifoveal RT, and pRNFL (except temporal) had significant decreased.

CONCLUSION

The changes of ocular biometric parameters in children and adolescents are closely related to refractive errors. Ocular biometric parameters devices, as effective non-invasive techniques, provide objective biological markers for monitoring refractive errors such as myopia.

Evidence of vascular involvement in myopia: a review

The benign public perception of myopia (nearsightedness) as a visual inconvenience masks the severity of its sight-threatening consequences. Myopia is a significant risk factor for posterior pole conditions such as maculopathy, choroidal neovascularization and glaucoma, all of which have a vascular component. These associations strongly suggest that myopic eyes might experience vascular alterations prior to the development of complications. Myopic eyes are out of focus because they are larger in size, which in turn affects their overall structure and function, including those of the vascular beds. By reviewing the vascular changes that characterize myopia, this review aims to provide an understanding of the gross, cellular and molecular alterations identified at the structural and functional levels with the goal to provide an understanding of the latest evidence in the field of experimental and clinical myopia vascular research. From the evidence presented, we hypothesize that the interaction between excessive myopic eye growth and vascular alterations are tipping-points for the development of sight-threatening changes.

Macular Vascularity and Ganglion Cell Complex Parameters in the Young Adults with Myopia and Progressive Myopia

Purpose

The purpose of this study is to determine the relationships between foveal avascular zone (FAZ), foveal vascular density (FD) and GCC (ganglion cell complex) parameters in a healthy myopic population using optical coherence tomography angiography (angio-OCT).

Patients and Methods

Three hundred and eighty-one eyes of 381 healthy participants were included into this study and assigned to three groups according to their spherical equivalent (SE) values and an additional progressive myopia group. One randomly chosen eye from each patient was analyzed. GCC mean thickness, focal loss of volume (FLV), global loss of volume (GLV), FAZ area, FAZ perimeter, and FD parameters were obtained with the RTVue AngioOCT device.

Results

FAZ area and its perimeter were strongly correlated with the belonging spherical equivalent group (p = 0.0001, p = 0.0008 accordingly), being the largest in progressive myopia subgroup (mean size 0.42mm²). Other factors that were significantly higher in myopic eyes were FLV (p = 0.0023), GLV (p = 0.0020). There were no differences in FD between groups. In the myopic and progressive myopia groups, there was a significant relationship between FAZ area and FLV, GLV, and GCC thickness. We found that in myopic eyes with AXL exceeding 26.6 mm, FAZ becomes negatively correlated to mean GCC thickness.

Conclusion

In myopia, compared to non-myopic groups, there is a greater loss of neural tissue represented by a thinner GCC layer, greater FLV and GLV parameters, and worse blood supply represented by a larger FAZ area. Eye axial length of 26.6 mm is a breaking point, where the negative FAZ area to GCC thickness relationship curve is getting significantly steeper.

Investigation of retinal microvasculature and choriocapillaris in adolescent myopic patients with astigmatism undergoing orthokeratology

Background

To observe alterations of fundus microcirculation and retinal thickness in adolescent myopic patients with astigmatism after toric and spherical orthokeratology using optical coherence tomography angiography (OCTA), to explore the effects of orthokeratology on the retinal thickness and choroidal blood flow.

Methods

A total of 48 patients were enrolled and divided into two group (toric orthokeratology (T) group and spherical orthokeratology (S) group) according to the type of lens design. OCTA was used to measure the superficial and deep retinal vessel densities at the macular region, radial peripapillary capillary (RPC) density, foveal avascular zone (FAZ) area, and choriocapillaris (ChC) perfusion area before and after orthokeratology for 3 months. The data were statistically analyzed by SPSS 19.0 software.

Results

Compared with before orthokeratology, the superficial vessel density in the fovea and parafovea in the T group significantly increased, and the deep vessel density in the whole area and fovea were significantly elevated after 3 months (P < 0.05). The superficial vessel density was significantly higher only in the parafovea in the S group after 3 months than that before orthokeratology (P < 0.05), deep vessel density in the whole area and parafovea after 3 months was significantly higher than that before orthokeratology (P < 0.05). RPC density in the two groups increased after 3 months of orthokeratology in the whole area and inside the disc area (P < 0.05).

Three months after toric orthokeratology, FAZ area in the T group was significantly reduced by 0.05 (− 0.41 to + 0.08) mm², while ChC perfusion area was enlarged by 0.06 ± 0.12 mm². FAZ area in the S group significantly decreased by 0.01 (− 0.19 to + 0.01) mm², whereas ChC perfusion area increased by 0.06 (− 0.07 to + 0.50) mm². Retinal thickness in the two groups increased after 3 months of orthokeratology in the whole area and parafoveal area (P < 0.05).

Conclusion

Orthokeratology improved retinal blood flow in macular area and RPC while controlling myopia. The changes in FAZ and ChC perfusion areas did not significantly differ between toric and spherical orthokeratology.

Various configuration types of the foveal avascular zone with related factors in normal Chinese adults with or without myopia assessed by swept-source OCT angiography

AIM

To describe the morphological characteristics of foveal avascular zone (FAZ) in normal Chinese adults with or without myopia by swept-source optical coherence tomography angiography (SS-OCTA) and analyze the possible associated factors.

METHODS

Normal Chinese adults with or without myopia aged between 18 and 60y were recruited into the study. One eye in each individual was randomly selected for scanning using SS-OCTA. FAZ parameters, central retinal thickness (CRT) and central choroidal thickness (CCT) were then analyzed. Correlations between systemic and ocular variables and FAZ parameters were subsequently evaluated. The subgroup analysis based on refractive error was also carried out.

RESULTS

In total, 127 eyes out of 127 normal subjects were finally included in the study (mean age 29.5±8.22y, 61 males and 66 females). The pattern of FAZ was variable: round configuration in 28 eyes (22%), quadrilateral configuration in 23 eyes (18%), pentagonal configuration in 20 eyes (16%), oval configuration in 15 eyes (12%), triangular configuration in 6 eyes (5%) and irregular configuration in 35 eyes (28%). The mean area of FAZ was 0.37±0.12 mm². Females had a larger FAZ (0.41±0.11 mm² vs 0.32±0.11 mm²) compared with that of males (P<0.01). All myopic individuals showed smaller FAZ area and perimeter compared with that of normal individuals (P<0.01). There was no obvious correlation between age and FAZ. In the univariate regression analysis, both axial length (AL) and refractive error were significantly related to FAZ parameters. However, only CRT showed negative correlation with FAZ in the multivariate regression analysis.

CONCLUSION

The pattern of FAZ configuration in normal Chinese adults with or without myopia is highly variable. Establishing quantitative parameters of FAZ would not only provide details of macular pathophysiology but could possibly contribute as a biomarker in disease staging.

Hemodynamic and morphological changes of the central retinal artery in myopic eyes

Due to excessive elongation of the eyeball, myopia-related vascular abnormalities are frequently observed in the central retinal artery (CRA) and its intraretinal branches. In addition to inconsistency in previously reported findings, hemodynamic (reduced flow velocity, increased vascular resistance) and morphological changes (narrower vessel diameter) were usually studied separately. This cross-sectional study evaluated the hemodynamic and morphological characteristics concurrently in a large sample of healthy myopes, by using the color Doppler ultrasound and adaptive optics retinal camera. Results showed that the retrobulbar segment of CRA had a tendency of slightly reduced flow velocity in eyeballs with longer axial length, but the correlation was not significant after adjusting for the multiple correlations. Vascular resistance was not affected by the axial elongation. With respect to the intraretinal branches, no significant changes in longer eyes of total diameter or lumen diameter were observed, while both the wall thickness and the wall cross-sectional area were significantly increased, but only a marginally increase in the wall to lumen ratio was found with increasing axial length. This implies some potential small artery remodeling in the intraretinal CRA branches. Overall, blood supply of the inner retina in healthy young myopes is likely to be maintained. Additionally, morphological parameters of vascular microstructure could be potential biomarkers to monitor myopia progression and understand myopia-related vascular abnormalities in future studies.

Abnormal Large-Scale Neuronal Network in High Myopia

Aim

Resting state functional magnetic resonance imaging (rs-fMRI) was used to analyze changes in functional connectivity (FC) within various brain networks and functional network connectivity (FNC) among various brain regions in patients with high myopia (HM).

Methods

rs-fMRI was used to scan 82 patients with HM (HM group) and 59 healthy control volunteers (HC group) matched for age, sex, and education level. Fourteen resting state networks (RSNs) were extracted, of which 11 were positive. Then, the FCs and FNCs of RSNs in HM patients were examined by independent component analysis (ICA).

Results

Compared with the HC group, FC in visual network 1 (VN1), dorsal attention network (DAN), auditory network 2 (AN2), visual network 3 (VN3), and sensorimotor network (SMN) significantly increased in the HM group. FC in default mode network 1 (DMN1) significantly decreased. Furthermore, some brain regions in default mode network 2 (DMN2), default mode network 3 (DMN3), auditory network 1 (AN1), executive control network (ECN), and significance network (SN) increased while others decreased. FNC analysis also showed that the network connection between the default mode network (DMN) and cerebellar network (CER) was enhanced in the HM group.

Conclusion

Compared with HCs, HM patients showed neural activity dysfunction within and between specific brain networks, particularly in the DMN and CER. Thus, HM patients may have deficits in visual, cognitive, and motor balance functions.

Contrast Sensitivity Is Associated With Chorioretinal Thickness and Vascular Density of Eyes in Simple Early-Stage High Myopia

Objective

To evaluate the contrast sensitivity function (CSF), chorioretinal thickness and vascular density as well as their relationships in subjects with simple early-stage high myopia.

Methods

Eighty-one young subjects were enrolled in this study. They were categorized into the simple high myopia group (sHM, n = 51) and the low-moderate myopia group (control group, n = 30). Monocular CSF under best correction was measured with the qCSF method. Retinal superficial and deep vascular density, inner and outer retinal thickness and choroidal thickness were measured using optical coherence tomography angiography.

Results

The area under log CSF (AULCSF) and cutoff spatial frequency (Cutoff SF) of the sHM group were significantly reduced compared to those of the control group (P = 0.003 and P &lt; 0.001, respectively). The parafoveal and perifoveal retinal thickness, deep vascular density and choroidal thickness were also significantly reduced in the sHM group (all P &lt; 0.05). Multiple regression analysis revealed that AULCSF was significantly correlated with retinal deep vascular density, outer retinal thickness in the parafoveal and perifoveal areas (all P &lt; 0.05).

Conclusion

Compared to low to moderate myopic eyes, patients with simple high myopia have thinner retinal and choroidal thickness, lower retinal vascular density, and reduced contrast sensitivity. Moreover, the CSF was correlated with the measures of chorioretinal structure and vasculature. The results suggest that the CSF is a sensitive functional endpoint in simple early-stage high myopia.

Kearns–Sayre syndrome with a novel large-scale deletion: a case report

Background

Kearns–Sayre syndrome (KSS) is a rare, multisystem mitochondrial encephalomyopathy. We report a case of KSS with a novel 7.6-kb deletion as assessed through a long-range polymerase chain reaction (PCR) study in the blood. In addition, optical coherence tomography angiography (OCTA) confirmed deep retinal capillary atrophy for the first time.

Case presentation

A 13-year-old patient presented with progressive vision loss and difficulty with eye opening and was diagnosed with progressive external ophthalmoplegia and retinitis pigmentosa (RP). The patient also experienced heart block, vestibular dysfunction, growth retardation and multiple demyelinating lesions. A long-range PCR study in the blood revealed a large-scale Chrm: 6341–13,993 deletion, which was first reported and broadened the genetic spectrum of this disease. The patient underwent complete ophthalmic examination, medical history review and gene detection, resulting in a confirmation of the diagnosis of KSS. The patient was given a pair of applicable glasses to wear and was followed up every 3 months. An implantable pacemaker was also installed based on the advice of the physician.

Conclusions

We reported a novel large-scale deletion in the mitochondrial DNA of KSS, and OCTA was used for the first time to confirm deep retinal capillary atrophy. Furthermore, because ophthalmic symptoms are often the primary manifestation of KSS, the relationship between ophthalmology and mitochondrial diseases should be emphasised.

Morphological characteristics of retinal vessels in eyes with high myopia: Ultra-wide field images analyzed by artificial intelligence using a transfer learning system

Purpose

The purpose of this study is to investigate the retinal vascular morphological characteristics in high myopia patients of different severity.

Methods

317 eyes of high myopia patients and 104 eyes of healthy control subjects were included in this study. The severity of high myopia patients is classified into C0-C4 according to the Meta Analysis of the Pathologic Myopia (META-PM) classification and their vascular morphological characteristics in ultra-wide field imaging were analyzed using transfer learning methods and RU-net. Correlation with axial length (AL), best corrected visual acuity (BCVA) and age was analyzed. In addition, the vascular morphological characteristics of myopic choroidal neovascularization (mCNV) patients and their matched high myopia patients were compared.

Results

The RU-net and transfer learning system of blood vessel segmentation had an accuracy of 98.24%, a sensitivity of 71.42%, a specificity of 99.37%, a precision of 73.68% and a F1 score of 72.29. Compared with healthy control group, high myopia group had smaller vessel angle (31.12 ± 2.27 vs. 32.33 ± 2.14), smaller fractal dimension (Df) (1.383 ± 0.060 vs. 1.424 ± 0.038), smaller vessel density (2.57 ± 0.96 vs. 3.92 ± 0.93) and fewer vascular branches (201.87 ± 75.92 vs. 271.31 ± 67.37), all P < 0.001. With the increase of myopia maculopathy severity, vessel angle, Df, vessel density and vascular branches significantly decreased (all P < 0.001). There were significant correlations of these characteristics with AL, BCVA and age. Patients with mCNV tended to have larger vessel density (P < 0.001) and more vascular branches (P = 0.045).

Conclusion

The RU-net and transfer learning technology used in this study has an accuracy of 98.24%, thus has good performance in quantitative analysis of vascular morphological characteristics in Ultra-wide field images. Along with the increase of myopic maculopathy severity and the elongation of eyeball, vessel angle, Df, vessel density and vascular branches decreased. Myopic CNV patients have larger vessel density and more vascular branches.

Vessel Density and Retinal Thickness from Optical Coherence Tomography Angiography as New Indexes in Adolescent Myopia

Purpose

To evaluate and quantify blood perfusion and retinal thickness (RT) from the perspective of quadrants by optical coherence tomography angiography (OCTA) in adolescents with myopia and explore the relationship between axial elongation and related indexes of OCTA.

Methods

A total of 88 subjects (149 eyes) with different degrees of myopia were included in this cross-sectional study. Vessel density (VD) and RT of quadrants in macular and peripheral regions were measured through OCTA.

Results

The superficial VD (SVD) of the parainferior region was significantly correlated with axial length (AL) between the emmetropia (EM) group and high myopia (HI) group (P=0.012). There were significant differences in deep VD (DVD) in all quadrants, except for the foveal, perifoveal, and peri-inferior regions (P > 0.05). However, there were significant alterations in the whole, parainferior, and perinasal regions (P=0.030, 0.023, and 0.035) in the low-to-moderate myopia (L–M) group compared with those in the HI group. There were significant differences in the RT in all quadrants, except for the foveal, paratemporal, and paranasal regions (P > 0.05) between the EM and L–M groups and the foveal region (P > 0.05) between the EM and HI groups. Nevertheless, only RT in the peri-inferior region of the L–M and HI groups showed significant differences. AL was negatively correlated with SVD in the perifoveal and parainferior regions (r = −0.179, P=0.029; r = −0.227, P=0.005) and inversely correlated with DVD and RT in almost all quadrants, except for the foveal region (r = −0.020, P=0.811; r = 0.135, P=1.000).

Conclusion

DVD and RT were closely associated with the severity of myopia and might be new indexes in assessing and detecting myopia development via OCTA.

High myopia and macular vascular density: an optical coherence tomography angiography study

Objective

To investigate whether there are differences inmacular vascular density (VD) between patients with high-myopia (HM) and those with non-high myopia (NHM) using Optical Coherence Tomography Angiography (OCTA).

Method

OCTA was performed on 35 eyes with HM with spherical equivalence (SE) > − 6.00D and 35 eyes with NHM with SE ≤ -6.00D. Vascular densities of the macula (overall macula, fovea, parafovea, superior hemi and inferior hemi) were measured in each of the superficial, deep and choriocapillaris layers of the retina.

Results

In the superficial retinal layer, overall macular VFD was significantly higher in the NHM compared to the HM group (51.27 ± 3.74 vs. 48.07 ± 5.69, p < 0.05). There were significant differences between the NHM and HM in parafovea (52.58 ± 5.78 vs. 49.4 ± 6.43, p < 0.05), superior-hemi (53.38 ± 4.03 vs 49.78 ± 6.84, p < 0.05) and inferior-hemi regions (53.49 ± 4.61 vs 49.05 ± 6.41, p < 0.05), but not in the fovea region. Similarly, in the deep retinal layer, overall macular VFD was significantly higher in the NHM group compared to the HM group (58.69 ± 2.46 vs. 56.90 ± 4.08, p < 0.05). There was significant differences between the HM and NHM in superior-hemi region (61.97 ± 2.68 vs. 60.08 ± 3.98, p < 0.05), but not in the fovea, parafovea, and inferior-hemi region. In the choriocapillaris, there was no difference in the overall macular VFD, nor any of the individual sectors between the HM and the NHM groups.

Conclusion

VFD in the superficial and deep retinal layers of the macula are significantly increased in the NHM compared to HM eyes. This is not the case in the choroidal capillary layers of the retina.

Vessel Density in the Macular and Peripapillary Areas in Preperimetric Glaucoma to Various Stages of Primary Open-Angle Glaucoma in Taiwan

Peripapillary and macular vessel density (VD) are reduced in myopic non-glaucomatous eyes, the dynamic range of VD may be decreased by myopia, and whether VD measurement has the potential in differentiating stages of glaucoma severity in patients with myopic glaucoma remains questionable. This observational, cross-sectional study aimed to clarify the changes in peripapillary and macular VDs in preperimetric glaucoma (PPG) and primary open-angle glaucoma in the early, moderate, and late stages. A total of 1228 eyes from 661 participants (540 normal, 67 PPG, and 521 glaucomatous) were included. Participants underwent free blood tests at the internal medicine clinic to retrieve systemic data. Patients with glaucoma were grouped by disease severity, defined by glaucomatous visual field mean defect, including early-(224 eyes), moderate-(103 eyes), and late-stage glaucoma (194 eyes), and further divided into advanced (158 eyes) and terminal glaucoma (36 eyes). Macular VD, peripapillary VD, circumpapillary retinal nerve fiber layer (cpRNFL) thickness, and ganglion cell complex (GCC) thickness were evaluated and divided into superior and inferior parts. One-way analysis of variance was performed, followed by Tukey’s post-hoc test. The peripapillary VD was significantly different between the healthy and PPG groups and the early-, moderate-, and late-stage glaucoma subgroups (all p < 0.001). Peripapillary VD measurements are helpful in differentiating the various stages of glaucoma even in patients with myopic glaucoma.

Tilted disc syndrome (TDS): New hypotheses for posterior segment complications and their implications in other retinal diseases

Tilted disc syndrome (TDS) is considered a congenital anomaly due to a delayed closure of the embryonic fissure. It is characterized by an oblique orientation of the axis of the optic disc, associated with other posterior pole anomalies such as inferior crescent, situs inversus and inferior staphyloma. The aim of this review was to summarize the data supporting the current hypotheses for the pathogenesis of TDS, and its anatomical and functional clinical consequences. Recent imaging techniques, such as magnetic resonance imaging, wide-field fundus imaging, and 2- and 3-D optical coherence tomography have provided a new perspective on TDS and its complications. Different abnormalities have previously been reported, both in the anterior and posterior segments. The focus was on vision-threatening chorioretinal changes or complications, including choroidal neovascularization and serous retinal detachments and their therapeutic options. Based on clinical observations, assumptions were proposed to understand the occurrence of complications such as chorioretinal degenerative changes, choroidal neovascularization and polypoidal choroidal vasculopathy, macular serous retinal detachment, myopic foveoschisis and chorioretinal folds. These hypotheses could be referred to as the curvature "breaking point" hypothesis, the uneven growth "tractional" hypothesis, the "container-content" imbalance hypothesis, and the "choroidal funnel" hypothesis. Because these complications could also occur in other contexts, understanding the pathogenesis of TDS complications could help to understand their pathophysiology.

Acircularity and circularity indexes of the foveal avascular zone in high myopia

This study explored the association between foveal avascular zone (FAZ) parameters and high myopia using optical coherence tomography angiography. We divided 106 eyes of 106 patients into quartiles based on the axial length. The upper quartile was then defined as the high myopia group (n = 27), while the lower quartile was the non-high myopia group (n = 26). The areas and minor axis lengths of superficial and deep FAZ, the perimeters and major axis lengths of deep FAZ were significantly larger in eyes with high myopia than in eyes with non-high myopia (P < 0.05). Inversely, the subfoveal choroidal thickness was significantly thinner in eyes with high myopia than in those with non-high myopia. Linear regression analyses showed that no significant correlation was observed between FAZ areas and acircularity and circularity indexes of FAZ in non-high myopia group. Conversely, FAZ areas strongly correlated with acircularity and circularity indexes of FAZ in high myopia group. We found that an increase in the FAZ area in highly myopic eyes was accompanied by a significant variation in FAZ acircularity and circularity indexes. Further research should address whether these findings are associated with future disease development in highly myopic eyes.

Structural and haemodynamic properties of ocular vasculature in axial myopia

The high prevalence of myopia has become a global concern, especially in East and Southeast Asia. Alarmingly, the prevalence of high myopia is increasing. Mechanical stretching caused by excessive eyeball elongation leads to various anatomical changes in the fundus. This stretching force may also lead to the development of vascular abnormalities, which tend to be subtle and easily overlooked. A healthy ocular vasculature is a prerequisite of adequate oxygen supply for normal retinal functions. This review summarises previous findings on structural and haemodynamic aspects of myopia-related vascular changes.

Associations of refractive errors and retinal changes measured by optical coherence tomography: A systematic review and meta-analysis

Studies reporting alteration in retinal thickness using optical coherence tomography (OCT) have been performed in different populations with various degrees of refractive error, producing inconsistent results. Therefore, we performed a meta-analysis to evaluate the alterations in retinal OCT measurements in myopic and hyperopic patients compared to controls. Evaluation of different retinal layers' thickness may have significance for developing novel approaches for preventing, diagnosing, and treating refractive errors and their complications. We searched PubMed and EMBASE to identify articles that reported OCT measurements of different retinal layers and regions, including macular, foveal, parafoveal, perifoveal, foveolar, ganglion cell complex (GCC), retinal nerve fiber layer (RNFL), peripapillary retinal nerve fiber layer (pRNFL), and ganglion cell and inner plexiform layer (GC-IPL) thickness in addition to macular volume, and optic disc area in myopes and hyperopes comparing their differences with controls. We applied either a fixed-effects or random-effects model for the meta-analysis of these differences based on the assessed heterogeneity level. Furthermore, subgroup analyses and metaregression, as well as publication bias and quality assessment, were conducted for the eligible studies. Forty-seven studies with a total of 12223 eyes, including 8600 cases and 3623 non-cases, are included in this meta-analysis. Our results showed that, in comparison to controls, highly myopic eyes had a significantly lower value for mean macular thickness, macular GCC, macular GC-IPL, parafoveal, perifoveal, foveal, foveolar, RNFL, and pRNFL thickness. Compared to controls, moderately myopic eyes showed a significantly thinner mean macular GCC layer and pRNFL. On the other hand, hyperopic eyes had significantly thicker average pRNFL than controls. Several other significant differences were also observed in various regional analyses. The findings of the current study affirm the retinal OCT measurement differences between myopic and hyperopic eyes compared to controls, emphasizing OCT measurements' advantages as potential biomarkers of ocular pathologies.

Evaluation of retinal vascular density and related factors in youth myopia without maculopathy using OCTA

To evaluate the retinal vascular flow density changes of myopic eyes of young adults using optical coherence tomography angiography and the factors affecting these changes. In this cross-sectional study, 90 eyes of 45 participants were analyzed and divided into three groups: mild, moderate, and high myopia (without pathological changes). Macular and radial peripapillary capillary flow densities were measured using optical coherence tomography angiography. Their relationships with the axial length, the spherical equivalent of the refractive error, and age were analyzed using analysis of variance, Pearson's correlation coefficient, and multivariate linear regression analysis. Superficial and deep macular vascular densities were significantly decreased in the high myopia group compared to the other groups. In the high myopia group, the nasal peripapillary flow density decreased, whereas the flow density inside the disc increased. The axial length negatively correlated with the superficial and deep macular vascular density, but positively correlated with the vascular density inside the disc. The spherical equivalent of the refractive error negatively correlated with the macular vascular density. The retinal vascular density decreased in the high myopia group. Hence, the microvascular network inside the disc may have a compensatory action in the hypoxic setting of high myopia.

Quantitative OCT angiography of the retinal microvasculature and choriocapillaris in highly myopic eyes with myopic macular degeneration

PURPOSE

To quantify retinal and choriocapillaris (CC) microvasculature in highly myopic (HM) eyes with myopic macular degeneration (MMD) using swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

162 HM eyes (spherical equivalent ≤ -6.0 dioptres or axial length (AL) ≥26.5 mm) from 98 participants were enrolled, including 60 eyes (37.0%) with tessellated fundus, 54 eyes (33.3%) with peripapillary diffuse chorioretinal atrophy (PDCA), 27 eyes (16.7%) with macular diffuse chorioretinal atrophy (MDCA) and 21 eyes (13.0%) with patchy or macular atrophy. PLEX Elite 9000 SS-OCTA was performed to obtain perfusion densities (PD) of the superficial and deep retinal capillary plexus, and CC signal voids (number, area and density).

RESULTS

Retinal PD decreased with increasing severity of MMD. Multivariable analysis showed that after adjustment of age and other factors, retinal PD decreased significantly in eyes with longer AL (β≤-0.51, p<0.001) and with an MMD severity of MDCA or worse (β≤-1.63, p<0.001). Reduced retinal PD were significantly associated with worse vision (β≤-0.01, p≤0.04). In terms of CC signal voids, multivariable analysis showed that longer AL (p<0.001), but not MMD severity (p≥0.12) was significantly associated with CC signal void changes in the earliest stage of MMD.

CONCLUSION

We demonstrate significant OCTA alterations in the retina and CC in HM eyes with varying severities of MMD. In eyes with early-stage PDCA, lower retinal PD and more extensive CC signal voids are predominantly associated with increasing AL. In contrast, in eyes with MDCA or worse, MMD itself was associated with sparser retinal and CC circulation.

Macular and Peripapillary Optical Coherence Tomography Angiography Metrics Predict Progression in Diabetic Retinopathy: A Sub-analysis of TIME-2b Study Data

PURPOSE

To identify optical coherence tomography angiography (OCTA)-derived vessel metrics of the macula and optic nerve head (ONH) that predict diabetic retinopathy (DR) disease progression.

DESIGN

Secondary analysis of clinical trial data.

METHODS

This was a sub-analysis of prospectively collected data from 73 subjects that participated in the TIME-2b study (Aerpio Pharmaceuticals), a multicenter clinical trial for patients with moderate-to-severe DR treated with AKB-9778 and followed over a 12-month period. Eligible subjects were tested every 3 months with color fundus photography, spectral-domain OCT, and slit-lamp biomicroscopy. OCTA of the macula and ONH was obtained for a subset of patients enrolled at participating sites. En face, full-depth retinal projections centered at the macula were analyzed for multiple metrics including foveal avascular zone (FAZ) area and perimeter, nonperfusion area, vessel density (VD), and presence of intraretinal microvascular abnormalities (IRMA). VD of the radial peripapillary capillaries was evaluated in 4 quadrants surrounding the optic disc for ONH images. Progression was defined as a ≥2-step increase in DR severity scale score or development of diabetic macular edema.

RESULTS

Over a follow-up period of 12 months, 15 of 73 (20.5%) subjects progressed. At pretreatment baseline, larger FAZ area, presence of IRMA, and reduced peripapillary VD in the superior temporal and inferior temporal regions were significantly associated with increased odds of progression.

CONCLUSIONS

FAZ area and temporal peripapillary VD are predictors of DR progression. OCTA metrics may improve progression risk assessment in DR when compared to established risk factors alone.