Normative values and predictors of retinal oxygen saturation.

PURPOSE: To determine normal retinal oxygen saturation (SO2) values measured with retinal oximetry in a multiethnic group of healthy subjects and to evaluate the association of retinal SO2 with demographic and clinical parameters. METHODS: Retinal oximetry was performed in both eyes of 61 normal healthy subjects. Global and quadrant venous (SvO2) and arterial oxygen saturation (SaO2), arteriovenous difference in SO2, and venular and arteriolar width were measured. The association of SO2 parameters with age, gender, ethnicity, refraction, iris color, history of controlled systemic hypertension, and smoking was analyzed. RESULTS: Average SvO2 and SaO2 were 55.3 ± 7.1% and 90.4 ± 4.3%, respectively. All average measurements were comparable in both eyes, both genders, and among ethnic groups. Inferonasal quadrant SaO2 was higher in Asians. Age was associated with decreased SvO2 (ß = -0.19; P = 0.001) and SaO2 (ß = -0.11; P = 0.003). History of controlled systemic hypertension was associated with an increase in arteriovenous difference in SO2 (ß = 3.99; P = 0.013). CONCLUSION: This is the first description of retinal SO2 in healthy, multiethnic subjects. Aging decreases SvO2 and SaO2 and should be accounted for when interpreting retinal oximetry measurements. Other demographic and clinical parameters studied did not seem to significantly influence retinal SO2 measurements.

Corneal avascularity is due to soluble VEGF receptor-1.

Corneal avascularity-the absence of blood vessels in the cornea-is required for optical clarity and optimal vision, and has led to the cornea being widely used for validating pro- and anti-angiogenic therapeutic strategies for many disorders. But the molecular underpinnings of the avascular phenotype have until now remained obscure and are all the more remarkable given the presence in the cornea of vascular endothelial growth factor (VEGF)-A, a potent stimulator of angiogenesis, and the proximity of the cornea to vascularized tissues. Here we show that the cornea expresses soluble VEGF receptor-1 (sVEGFR-1; also known as sflt-1) and that suppression of this endogenous VEGF-A trap by neutralizing antibodies, RNA interference or Cre-lox-mediated gene disruption abolishes corneal avascularity in mice. The spontaneously vascularized corneas of corn1 and Pax6+/- mice and Pax6+/- patients with aniridia are deficient in sflt-1, and recombinant sflt-1 administration restores corneal avascularity in corn1 and Pax6+/- mice. Manatees, the only known creatures uniformly to have vascularized corneas, do not express sflt-1, whereas the avascular corneas of dugongs, also members of the order Sirenia, elephants, the closest extant terrestrial phylogenetic relatives of manatees, and other marine mammals (dolphins and whales) contain sflt-1, indicating that it has a crucial, evolutionarily conserved role. The recognition that sflt-1 is essential for preserving the avascular ambit of the cornea can rationally guide its use as a platform for angiogenic modulators, supports its use in treating neovascular diseases, and might provide insight into the immunological privilege of the cornea.

Nanoparticles sustain expression of Flt intraceptors in the cornea and inhibit injury-induced corneal angiogenesis.

PURPOSE: To determine whether long-term expression of intraceptors can be achieved using plasmid albumin nanoparticles and whether nanoparticles can inhibit and cause regression of murine corneal neovascularization induced by mechanical-chemical trauma. METHODS: Albumin nanoparticles encapsulating pCMV.Flt23K were developed as a lyophilized product that is easily redispersed in an aqueous medium. Nanoparticles were injected into the corneas of uninjured BALB/c mice and observed for toxicity for 3 weeks. Entry of nanoparticles into corneal cells was demonstrated through transmission electron microscopy and confocal imaging. Naked pCMV.Flt23K, nanoparticles encapsulating pCMV.Flt23K, or empty pCMV nanoparticles were injected into uninjured mouse corneas. These corneas were subjected to mechanical alkali trauma 3 weeks after injection. RESULTS: Nanoparticles were nontoxic to the cornea and entered into corneal keratocyte cytoplasm. They persisted for at least 4 weeks in the cornea, expressed effective intraceptor levels for at least 5 weeks, and reduced corneal neovascularization by approximately 40% (P = 0.035) at 5 weeks after administration. CONCLUSIONS: Albumin nanoparticles are not toxic to the cornea and can express intraceptors for extended periods that are effective in suppressing injury-induced corneal neovascularization.

Geographic Information Systems Mapping of Diabetic Retinopathy in an Ocular Telemedicine Network.

Importance: Minimal information exists on the use of geographic information systems mapping for visualizing access barriers to eye care for patients with diabetes. Objective: To use geographic information systems mapping techniques to visualize (1) the locations of patients participating in the North Carolina Diabetic Retinopathy Telemedicine Network, (2) the locations of primary care clinicians and ophthalmologists across the state, and (3) the travel times associated with traveling to the 5 primary care clinics in our study. Design, Setting, and Participants: Cross-sectional study conducted from January 6, 2014, to November 1, 2015, at 5 Area Health Education Center primary care clinics that serve rural and underserved populations in North Carolina. In total, 1787 patients with diabetes received retinal screening photographs with remote expert interpretation to determine the presence and severity of diabetic retinopathy. Participants included patients 18 years or older with type 1 or type 2 diabetes who presented to these 5 clinics for their routine diabetes care. Main Outcomes and Measures: Development of qualitative maps illustrating the density of patients with diabetes and their distribution around the 5 North Carolina Diabetic Retinopathy Telemedicine Network sites by zip code and the density of ophthalmologists and primary care clinicians by zip code relative to US Census Urban Areas. A travel time map was also created using road network analysis to determine all areas that can be reached by car in a user-specified amount of time. Results: Mean (SD) age of patients was 55.4 (12.7) years. Women made up 62.7% of the study population. The study included more African American patients (55.4%) compared with white (35.5%) and Hispanic (5.8%) patients. The mean (SD) hemoglobin A1c level was 7.8% (2.4%) (to convert to proportion of total hemoglobin, multiply by 0.01), and the mean (SD) duration of diabetes was 9.2 (8.2) years. Whereas the clinics located in Greensboro, Asheville, and Fayetteville screened patients from more immediate surrounding areas, the Greenville site had the widest distribution of zip codes, suggesting that patients travel from greater distances to reach this facility. Primary care clinicians were spread somewhat uniformly across the state, whereas ophthalmologists were concentrated around urban centers. Also, the number and type of surface roads surrounding the clinics determined the distance and time patients must travel to receive care. Conclusions and Relevance: Geographic information systems mapping is a useful technique for visualizing geographic access barriers to eye care for patients with diabetes and may help to identify underserved areas that would benefit from the expansion of retinal screening programs via telemedicine.

Evaluation of Diabetic Retinal Screening and Factors for Ophthalmology Referral in a Telemedicine Network.

Importance: Retinal telescreening for evaluation of diabetic retinopathy (DR) in the primary care setting may be useful in reaching rural and underserved patients. Objectives: To evaluate telemedicine retinal screenings for patients with type 1 or 2 diabetes and identify factors for ophthalmology referral in the North Carolina Diabetic Retinopathy Telemedicine Network. Design, Setting, and Participants: A preimplementation and postimplementation evaluation was conducted from January 6, 2014, to November 1, 2015, at 5 primary care clinics serving rural and underserved populations in North Carolina among 1787 adult patients with type 1 or 2 diabetes who received primary care at the clinics and obtained retinal telescreening to determine the presence and severity of DR. A total of 1661 patients with complete data were included in the statistical analysis. Intervention: Nonmydriatic fundus photography with remote interpretation by an expert. Main Outcomes and Measures: Number of patients recruited, level of detected DR, change in rates of screening, rate of ophthalmology referral, percentage of completed referrals, and patient characteristics associated with varying levels of DR. Results: Of the 1661 patients (1041 women and 620 men; mean [SD] age, 55.4 [12.7] years), 1323 patients (79.7%) had no DR, 183 patients (11.0%) had DR without a need for an ophthalmology referral, and 155 patients (9.3%) had DR with a need for an ophthalmology referral. The mean rate of screening for DR before implementation of the program was 25.6% (1512 of 5905), which increased to 40.4% (1884 of 4664) after implementation. A total of 93 referred patients (60.0%) completed an ophthalmology referral visit within the study period. Older patients (odds ratio [OR], 1.28; 95% CI, 1.11-1.48) and African American patients (OR, 1.84; 95% CI, 1.24-2.73) or other racial/ethnic minorities (OR, 2.19; 95% CI, 1.16-4.11) had greater odds of requiring an ophthalmology referral compared with white and/or younger patients. Patients with higher hemoglobin A1c levels (OR, 1.19 per unit change; 95% CI, 1.13-1.25 per unit change) and longer duration of diabetes (OR, 1.76 per decade; 95% CI, 1.53-2.02 per decade) had greater odds of DR requiring an ophthalmology referral. History of stroke (OR, 1.65; 95% CI, 1.10-2.48) and kidney disease (OR, 1.59; 95% CI, 1.10-2.31) were strongly associated with DR and ophthalmology referral. Conclusions and Relevance: When implemented in the primary care setting, retinal telescreening increased the rate of evaluation for DR for patients in rural and underserved settings. This strategy may also increase access to care for minorities and patients with DR requiring treatment.

Flt-1 intraceptor induces the unfolded protein response, apoptotic factors, and regression of murine injury-induced corneal neovascularization.

PURPOSE: To determine whether Flt24K, a recombinant construct of domains 2 to 4 of VEGFR-1 (Flt) coupled with an endoplasmic reticulum retention signal (KDEL) can bind VEGFR-2 and induce apoptosis, unfolded protein response (UPR), and regression of injury-induced corneal neovascularization. METHODS: Human microvascular endothelial cells were transfected with pCMV.Flt24K and subjected to hypoxia. Cell lysates underwent Western blot analysis with anti-XBP-1 antibody and RT-PCR for CHOP. Human malignant melanoma cells (which express VEGFR-2 but not Flt), were transfected with pCMV.Flt24K, and lysates underwent immunoprecipitation with anti-FLT antibody, and Western blot analysis for VEGF and VEGFR-2. Mouse corneas sustained injury induced by topical NaOH and mechanical scraping and were injected with pCMV.Flt24K 2 weeks later. Corneas were harvested 2 days later for Western blot analysis for XBP-1 and caspase-3 or 1 week later for quantification of neovascularization and TUNEL staining. Saline and empty pCMV vector were used in control experiments. RESULTS: The mean percentage area of corneal neovascularization in mice 3 weeks after corneal injury and 1 week after intrastromal injection of empty pCMV vector or pCMV.Flt24K was 55.4% +/- 2.7% vs. 19.3% +/- 6.1%, respectively (P < 0.001). Flt24K was found to bind VEGFR-2 and upregulate activated XBP-1 and CHOP in vitro. In vivo, pCMV.Flt24K upregulated activated XBP-1 and caspase-3. Apoptosis was observed in corneal neovascular endothelium in corneas treated with pCMV.Flt24K but not in the control. CONCLUSIONS: The Flt24K intraceptor can bind VEGFR-2 within cells, induce the unfolded protein response in vitro and in vivo, elicit apoptosis of vascular endothelial cells in vivo, and induce regression of corneal neovascularization in vivo.

Flt-1 intraceptors inhibit hypoxia-induced VEGF expression in vitro and corneal neovascularization in vivo.

PURPOSE: To determine whether subunits of VEGF receptor-1 coupled with an endoplasmic reticulum retention signal can block hypoxia-induced upregulation of VEGF secretion in corneal epithelial cells and block murine corneal angiogenesis induced by corneal injury. METHODS: Human corneal epithelial cells, transfected with plasmids encoding Flt23K or Flt24K (the VEGF-binding domains of the Flt-1 receptor coupled with the endoplasmic reticulum retention peptide KDEL), were subjected 2 days after transfection to 5% hypoxia for 24 hours. Supernatant was sampled at 24 hours and assayed for VEGF by ELISA. For in vivo models, mouse corneas underwent intrastromal injections of plasmids encoding Flt23K or Flt24K, and 2 days later, sustained injury induced by topical NaOH and mechanical scraping. Corneas were assessed 2 days later for VEGF ELISA and leukocyte counting or 1 week later for quantification of neovascularization. RESULTS: Hypoxia induced VEGF by human corneal epithelial cells was sequestered by both Flt23K and Flt24K; Flt-1 23K suppressed VEGF secretion as well. Intrastromal delivery of plasmid Flt23K suppressed VEGF by 40.4% (P = 0.009), leukocytes by 49.4% (P < 0.001), and neovascularization by 66.8% (P = 0.001). Flt24K suppressed VEGF expression by 30.8% (P = 0.042), leukocytes by 25.8% (P < 0.001), and neovascularization by 49.5% (P = 0.015). CONCLUSIONS: Flt-1 intraceptors, which are endoplasmic reticulum retention signal-coupled VEGF receptors, significantly suppress hypoxia-induced VEGF secretion by corneal epithelial cells in vitro. In vivo, delivery of naked plasmids expressing these intraceptors inhibits injury-induced upregulation of VEGF, leukocyte infiltration, and corneal neovascularization.

Residual and Dynamic Range of Retinal Nerve Fiber Layer Thickness in Glaucoma: Comparison of Three OCT Platforms.

PURPOSE: To estimate visual field (VF) sensitivity at which retinal nerve fiber layer (RNFL) thinning reaches the measurement floor and at which RNFL stops thinning (change points), the dynamic range of RNFL thickness, and the number of steps from normal to RNFL floor among three optical coherence tomography (OCT) devices. METHODS: Glaucomatous patients (n = 58) and healthy subjects (n = 55-60) prospectively underwent VF testing and RNFL thickness measurement with Cirrus, Spectralis, and RTVue. Change points and corresponding RNFL thicknesses were estimated with simple linear regression (SLR) and Bayesian change point (BCP) analyses. The dynamic range and number of steps to RNFL floor were determined. RESULTS: The average VF change points and corresponding residual thickness at the time RNFL stopped thinning were -22.2 dB and 57.0 µm (Cirrus), -25.3 dB and 49.2 µm (Spectralis), and -24.6 dB and 64.7 µm (RTVue). The RNFL dynamic ranges derived from SLR values were wider on Spectralis (52.6 µm) than on Cirrus (35.4 µm) and RTVue (35.5 µm); the corresponding number of steps to reach the RNFL floor were 9.0 on Cirrus, 10.6 on Spectralis, and 8.3 on RTVue. CONCLUSIONS: The relative VF sensitivity at which average RNFL thickness reaches the measurement floor, the residual layer thickness, and RNFL dynamic measurement range differ among the three devices. However, the number of steps from normal to the RNFL thickness floor is comparable.

Pars plana vitrectomy for rhegmatogenous retinal detachment associated with benign retinal tumors.

Two patients with known histories of benign retinal tumors presented with rhegmatogenous retinal detachments (RRD) in the same eye. One had a retinocytoma and presenting vision of 20/50, while the other had congenital hypertrophy of the retinal pigment epithelium and vision of 20/30. Both had subretinal fluid accumulation in a configuration consistent with a retinal break near the tumor; however, no breaks were detected on examination or intraoperatively. Pars plana vitrectomy (PPV), drainage retinotomy, fluid-air exchange, barrier laser around the tumor, and gas tamponade successfully reattached the retina in both cases. After 12 and 6 months of follow-up, respectively, final vision was 20/25 and the retina remained attached. RRD may be associated with benign retinal tumors presumably with microscopic breaks at the margins. In these cases, PPV, drainage retinotomy, fluid-air exchange, endolaser around the tumor, and gas tamponade can be effective for treatment.

Focal choroidal excavation associated with polypoidal choroidal vasculopathy.

A 48-year-old woman presented with blurred vision in her right eye for 6 weeks. Visual acuity was 20/300 and 20/25 in the right and left eyes, respectively. Fundus examination showed subretinal hemorrhage in the superonasal macula in the right eye, whereas the left eye was normal. Fluorescein angiography showed blocked fluorescence from hemorrhage and a round distinct hypofluorescent spot along the inferotemporal arcade. Indocyanine green angiography revealed hyperfluorescent tubular and aneurysmal dilatations consistent with polypoidal choroidal vasculopathy in the superior macula. Spectral-domain optical coherence tomography showed retinal pigment epithelial irregularities and detachment. Scans through the round area of hypofluorescence revealed a conforming focal choroidal excavation and thinning of the underlying choriocapillaries. Because the pathogenesis of focal choroidal excavation is currently unclear, the authors propose the possibility of an acquired etiology related to loss of choriocapillaries from perfusion abnormalities as evidenced here.