Validation of modified smartphone camera against single lens reflex (SLR) camera and in-person grading of trachoma.

Abstract

Purpose : Trachoma grading according to the simplified World Health Organization (WHO) grading scheme is typically performed in-person but has the potential to be done remotely. A novel smartphone attachment (Ocular CellScope, University of California, Berkeley) that incorporates a +25D lens to magnify images captured from a smartphone camera is promising, but has not been validated against images from more traditional single lens reflex (SLR) cameras.

Methods : A random sample of 1-9 year old children from 13 rural communities in Ethiopia was enrolled in this cross-sectional study. The superior tarsal conjunctiva of each child was graded for trachomatous inflammation-follicular (TF) and trachomatous inflammation-intense (TI) according to the WHO’s simplified grading system. Conjunctival photographs were then taken using two cameras : a Nikon D-series SLR camera and an iPhone 4S coupled to the Cellscope attachment. Images were graded for TF and TI by 2 photo-graders masked to camera type and to each other’s grades, with discrepancies adjudicated by a third masked grader.

Results : 499 children were enrolled with conjunctival photography performed with both cameras. The results of field grading, SLR photo-grading, and smartphone photo-grading are cross-tabulated in Table 1. Smartphone photo-grading tended to under-estimate TF relative to SLR photo-grading (Table 1), although agreement was relatively good with field grading for both methods of photography.

Conclusions : Images from both SLR and smartphone showed substantial agreement with field trachoma grading, with better agreement for TF than for TI. This suggests that when research studies or trachoma programs use conjunctival photography for trachoma grading, the CellScope attachment coupled to a smartphone will provide similar results to SLR photography, and be more convenient, cost-effective, and easier-to-use.

This is a 2020 ARVO Annual Meeting abstract.