Abstract
Evaluation of nonmydriatic fundus photographs captured with a low-cost, smartphone-based camera facilitated remote screening of patients for enlarged optic nerve cup-to-disc ratio in the Independent Nation of Samoa, an underserved setting with one full-time ophthalmologist in the entire country. To investigate factors that impact inter-rater agreement of glaucoma suspect optic disc status using a low-cost, handheld nonmydriatic fundus camera. Color fundus photographs were obtained using the PanOptic iExaminer attached to an iPhone 6S by a lay examiner on 206 participants in the Independent Nation of Samoa. Images were remotely graded by an ophthalmologist and optometrist, and images from participants identified as at-risk for glaucoma were escalated to a glaucoma subspecialist for review. Fundus photo brightness, contrast, and focus were measured using the cup, rim, and temporal regions of the disc. Stereoscopic image pairs were subsequently generated from a subset of individual nonmydriatic photographs. Features suggestive of glaucoma based on optic disc cupping were identified in 16.0% (33/206) of participants. There was moderately strong agreement between graders (90.3%) with κ=0.53 [95% confidence interval (CI)=0.33-0.73]. The intraclass correlation coefficients for the cup-to-disc ratio (CDR) and its difference were 0.84 (95% CI=0.81-0.87) and 0.68 (95% CI=0.59-0.75). Of the 33 participants identified, 94% had clinical risk criteria for potential glaucoma when reviewed by a subspecialist. Color fundus photograph cup brightness was significantly associated with cup-to-disc (CDR) grade, R2=0.36 (P<0.001), in which a brighter disc yielded a higher CDR. Smartphone-based screening is a simple, low-cost method capable of measuring the CDR of the optic nerve. When combined with testing for other glaucoma risk factors such as intraocular pressure, this method of measuring CDR may help identify those patients who should be referred for further ophthalmologic assessment. We are currently conducting studies to assess the sensitivity and specificity of smart phone-based remote screening.
Highlights
Screening for vision-threatening conditions in resource-constrained settings remains a significant challenge in healthcare.[1,2] Advances in handheld, battery-operated devices, have overcome difficulties associated with fundus photography outside of the traditional clinic.[2]
When combined with testing for other glaucoma risk factors such as intraocular pressure, this method of measuring cup-to-disc ratio (CDR) may help identify those patients who should be referred for further ophthalmologic assessment
We found that clinically-gradable images can be obtained from nearly 82% of eyes in a teleophthalmology program conducted throughout twelve remote villages in the Independent Nation of Samoa, a country where only one full-time ophthalmologist serves an island population of nearly 200,000 people.[4]
Summary
Screening for vision-threatening conditions in resource-constrained settings remains a significant challenge in healthcare.[1,2] Advances in handheld, battery-operated devices, have overcome difficulties associated with fundus photography outside of the traditional clinic.[2]. We explore the impact of quantitative fundus photograph metrics, including image brightness, contrast, and focus, on inter-rater agreement of glaucoma suspect status
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