Aqueous Levels of Pigment Epithelium-Derived Factor and Macular Choroidal Thickness in High Myopia

Changes in Plasma VEGF and PEDF Levels in Patients with Central Serous Chorioretinopathy

Background and Objectives: Retinal pigment epitheliopathy and hyperpermeability of choroidal vessels were postulated to be involved in the pathogenesis of central serous chorioretinopathy (CSC). Imbalanced levels of vascular endothelial growth factor (VEGF) and pigment-epithelium–derived factor (PEDF) were previously implicated in the development of chorioretinal diseases characterized by increased vascular permeability. We aimed to compare the plasma levels of proangiogenic VEGF and antiangiogenic PEDF for 26 patients with acute CSC, 26 patients with chronic CSC, and 19 controls. Materials and Methods: VEGF and PEDF levels were measured using a multiplex immunoassay or enzyme-linked immunosorbent assay. Correlations with disease duration were assessed. Results: VEGF levels differed between groups (p = 0.001). They were lower in patients with acute CSC (p = 0.042) and chronic CSC (p = 0.018) than in controls. PEDF levels were similar in all groups. The VEGF-to-PEDF ratio was lower in CSC patients than in controls (p = 0.04). A negative correlation with disease duration was noted only for PEDF levels in the group with chronic CSC (rho = −0.46, p = 0.017). Discussion: Our study confirmed that patients with CSC have imbalanced levels of VEGF and PEDF. This finding may have important implications for the pathogenesis of CSC. VEGF-independent arteriogenesis rather than angiogenesis may underlie vascular abnormalities in these patients.

High Myopia and the Complement System: Factor H in Myopic Maculopathy

High myopia (HM) is both a medical problem and refractive error of the eye owing to excessive eyeball length, which progressively makes eye tissue atrophic, and is one of the main causes for diminishing visual acuity in developed countries. Despite its high prevalence and many genetic and proteomic studies, no molecular pattern exists that explain the degenerative process underlying HM, which predisposes patients to other diseases like glaucoma, cataracts, retinal detachment and chorioretinal atrophy that affect the macular area. To determine the relation between complement Factors H (CFH) and D (CFD) and the maculopathy of patients with degenerative myopia, we studied aqueous humor samples that were collected by aspiration from 122 patients during cataract surgery. Eyes were classified according to eyeball axial length as high myopia (axial length > 26 mm), low myopia (axial length 23.5–25.9 mm) and control (axial length ˂ 23.4 mm). The degree of maculopathy was classified according to fundus oculi findings following IMI’s classification. Subfoveal choroid thickness was measured by optical coherence tomography. CFH and CFD measurements were taken by ELISA. CFH levels were significantly high in the high myopia group vs. the low myopia and control groups (p ˂ 0.05). Significantly high CFH values were found in those eyes with choroid atrophy and neovascularization (p ˂ 0.05). In parallel, the CFH concentration correlated inversely with choroid thickness (R = −0.624). CFD levels did not correlate with maculopathy. All the obtained data seem to suggest that CFH plays a key role in myopic pathology.

Refractive Errors, Ocular Biometry and Diabetic Retinopathy: A Comprehensive Review

Purpose: To summarize the association between diabetic retinopathy and refractory status as well as ocular biometric parameters; To review the theories of the protective effect of high myopia against diabetic retinopathy. Methods: A comprehensive literature search on MEDLINE, EMBASE, Web of Science and Scopus databases as well as reference list search, and systematic review of relevant publications.  Results: Myopia may delay the onset and progression of diabetic retinopathy. Increased axial length in myopia is associated with reduced risk of any diabetic retinopathy and vision-threatening diabetic retinopathy. The possible mechanisms for the protective effect of myopia against diabetic retinopathy may include posterior vitreous detachment, change in retinal blood flow and oxygen demand, choroidal thinning and altered cytokine profiles.  Conclusions: High myopia may be a protective factor against the onset and progression of diabetic retinopathy. Further studies about the mechanisms of how myopia, axial length and ocular biometrics influence the onset and progression of DR are needed.

Pigment Epithelium-Derived Factor as a Possible Treatment Agent for Choroidal Neovascularization

Choroidal neovascularization (CNV) is a sight-threatening disease and is characterized by the formation of pathological neovascularization in the choroid which extends into the subretinal space. Exudative age-related macular degeneration (AMD) is the formation of CNV in the macular area which leads to irreversible blindness. Continuous leakage and hemorrhage of the CNV lesion may eventually result in scarring or later fibrosis, which could result in photoreceptor cell atrophy. The current strategy for treating CNV is the use of antivascular endothelial growth factor (VEGF) agents. Many studies have demonstrated the efficacy of intravitreal anti-VEGF therapy. Other studies have also reported the side effects of single anti-VEGF treatment. And long-term inhibition of a single system may result in collateral damage to other visual elements. Pigment epithelium-derived factor (PEDF) is a 50 kDa protein that was first isolated from the conditioned medium of human RPE cells. PEDF has both antiangiogenesis and neuroprotective functions for photoreceptor cells. It may be a potential ocular antiangiogenic agent. This review outlines the distribution of PEDF in the eye, the mechanism of antiangiogenesis, the protective effect on the retina, and the relationship between PEDF and VEGF.

Morphological Characteristics and Risk Factors of Myopic Maculopathy in an Older High Myopia Population-Based on the New Classification System (ATN)

PURPOSE

To investigate the characteristics, mergers, and risk factors of different types of myopic maculopathy (MM) in a highly myopic population.

DESIGN

Population-based, cross-sectional study.

METHODS

A total of 1086 eyes (762 patients) were enrolled. Each participant underwent detailed ocular examinations. Combining the fundus photographs and optical coherence tomography images, types of MM were assessed as myopic atrophy maculopathy (MAM), myopic tractional maculopathy (MTM), or myopic neovascular maculopathy (MNM) according to the ATN classification system. Peripapillary atrophy (PPA) area, tilt ratio, and macular choroidal thickness (mChT) were measured individually.

RESULTS

Eyes with larger PPA area were more likely to have MAM (odds ratio [OR], 1.220; P = .037 per 1-mm² increase) and MNM (OR, 1.723; P < .001 per 1-mm² increase), and eyes with thicker mChT were less likely to have MAM (OR, 0.740; P < .001 per 10-μm increase) and MNM (OR, 0.784; P < .001 per 10-μm increase), whereas eyes with higher tilt ratio were less likely to have MTM (OR, 0.020; P < .001 per 1 increase). The severity of MTM and MNM was not precisely consistent with that of MAM.

CONCLUSIONS

Different types of MM have different risk factors; larger PPA area and thinner mChT are risk factors for MAM and MNM, whereas lower tilt ratio is a risk factor for MTM. Our results indicate that the pathogenesis of MTM is different from that of MAM and MNM, and a tractional component should be considered as a possible component to the myopic macular classification.

Relationship between Aquaporin-1 Protein Expression and Choroidal Thickness during the Recovery of Form-deprivation Myopia in Guinea Pigs

Purpose: The purpose of this study was to investigate the relationship between aquaporin-1 (AQP-1) protein expression in the choroid and choroid thickness (CT) during the recovery of form-deprivation (FD) myopia in guinea pigs.Materials and Methods: Seventy-two guinea pigs were randomly assigned to the normal control (NC) group, FD 21 group (animals wore a latex facemask in the right eye for 21 days to induce FD myopia) and four recovery (REC) groups. Guinea pigs in the REC groups also wore the facemask for 21 days to induce myopia; then, the facemask was removed, and the eye was re-exposed to the normal environment for 12 hours (REC ½ group), 1 day (REC 1 group), 2 days (REC 2 group), and 7 days (REC 7 group). All animals underwent biometric measurements (refraction, axial length, and CT), and the protein expression of AQP-1 in the choroid was determined using western blotting.Results: The protein expression of AQP-1 and CT were significantly decreased in the FD 21 group as compared with those in the NC group (p = .007 and p < .001). Both AQP-1 protein expression and CT gradually increased and peaked in the REC 2 group. Additionally, there were significant differences in AQP-1 protein expression and CT between the REC 2 group and all other groups (all p < .05). We observed a complete recovery in the in REC 7 group as compared with the NC group (p > .05). AQP-1 protein expression was significantly associated with CT (p = .001) in all groups; however, there was a significant negative correlation (p = .029) between AQP-1 protein expression and axial length in the REC groups.Conclusions: AQP-1 protein expression in the choroid was upregulated following recovery of FD myopia in guinea pigs, and these changes correlated with alterations in CT and axial length.

Correlation of axial length and myopic macular degeneration to levels of molecular factors in the aqueous

To elucidate the molecular processes associated with the development of myopic macular degeneration (MMD), we measured the intraocular concentrations of molecular factors in emmetropic and myopic eyes. This is a retrospective clinic-based case-control study that included eyes undergoing routine cataract surgery whereby aqueous humour samples were obtained. We measured the concentrations of pigment epithelium derived factor(PEDF), matrix metalloproteinase 2(MMP-2), tissue inhibitor of metalloproteinase(TIMP-2), vascular endothelial growth factor isoform A(VEGF-A), interleukin 8(IL-8), interleukin 6(IL-6), C-reactive protein(CRP), angiopoietin 2(Ang2), and amphiregulin. 38 eyes (axial length (AL): 22.4–32.4 mm), including 12 highly myopic (HM) eyes (AL ≥ 26.5 mm) without MMD and 12 HM eyes with MMD but without neovascularization were included. Eyes with MMD were found to have significantly lower VEGF-A levels (p = 0.007) and higher MMP-2 levels (p = 0.02) than control eyes after adjusting for age and gender. MMP-2 levels correlated positively (r = 0.58, p = 0.002), while VEGF-A levels correlated negatively with longer axial length (r = −0.75, p < 0.001). Both the concentrations of VEGF-A (P = 0.25) and MMP-2 (P = 0.69) were not significantly associated with MMD after adjusting for AL. These findings suggest that the predominant mechanism underlying the development of non-neovascular MMD may be axial elongation, driven in part by MMP-2 related mechanisms.

Macular choroidal thickness in highly myopic women during pregnancy and postpartum: a longitudinal study

Background

High myopia, a cause of serious visual impairment, is a significant global public health concern. We investigate longitudinal changes in macular choroidal thickness (CT) during pregnancy and 6-months postpartum in women with high myopia (HM).

Methods

A prospective longitudinal study was conducted in HM-pregnant women during the course of pregnancy (n = 42 eyes, 42 patients) and 6 months postpartum (n = 40 eyes, 40 patients, two cases lost).Macular CT was measured via enhanced-depth imaging (EDI)-optical coherence tomography (OCT) (EDI-OCT). Intraocular pressure (IOP), axial length (AL), refractive error, mean arterial pressure (MAP), mean ocular perfusion pressure (MOPP), and body mass index (BMI) were also measured.

Results

Macular CTs of HM pregnant women (214.3 ± 52.3 μm) had increased significantly during the third trimester of pregnancy compared with postpartum women (192.7 ± 51.9 μm, p = 0.014). No significant differences in AL, refractive error, or MAP were found between pregnant and postpartum groups (p > 0.05 for all parameters).During pregnancy, macular CT was negatively correlated with AL (first trimester: p = 0.010; second trimester: p = 0.013; and third trimester: p = 0.008) and positively correlated with refractive error (first trimester: p = 0.038; second trimester: p = 0.024; and third trimester: p = 0.010). No correlations between macular CT and age, IOP, MOPP, MAP, or BMI were found.

Conclusions

Our study revealed the presence of a significantly thicker choroid during the third trimester of pregnancy compared with 6-mo postpartum in HM women. Macular CT positively correlated with refractive error and negatively correlated with AL during pregnancy, but did not correlate with gestational age, MOPP, IOP, MAP, or BMI.