Pooja D. Jani

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 (&bgr; = −0.19; P = 0.001) and SaO2 (&bgr; = −0.11; P = 0.003). History of controlled systemic hypertension was associated with an increase in arteriovenous difference in SO2 (&bgr; = 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.

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.

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.

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.

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.

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.