Comparison of Five Camera Systems for Capturing and Grading Trachoma Images

To establish the presence or absence of trachoma in the Pacific Island region. Trachoma Rapid Assessment methodology was used in Kiribati, Nauru, Vanuatu, Solomon Islands and Fiji. Advised by key informants, high-risk communities were chosen from each country. All available children aged 1-9 years and adults > or = 40 years were examined. A total of 903 adults > or = 40 years and 3102 children aged 1-9 years were screened at 67 sites. Rates of active trachoma in children were >15% in all sites in Kiribati and >20% in all sites in Nauru. However, there was a high variability of rates of active trachoma in survey sites in Vanuatu, Solomon Islands and Fiji with rates ranging from 0% to 43% (average 23.3%), 6.0% to 51.9% (average 30.5%) and 0% to 48.8% (average 22.1%) respectively. Average rates of scarring trachoma in adults were 61.9% in Kiribati, 12.5% in Nauru, 38.2% in Vanuatu, 67.0% in the Solomon Islands and 18.8% in Fiji. Rates of trichiasis and trichiasis surgeries suggest the possibility of blinding trachoma in the region. The findings indicate that trachoma is present in all the Pacific Island countries screened. Further prevalence studies are required, and trachoma control measures should be considered.

The WHO is committed to eliminating trachoma as a public health concern by 2020.1 Since decisions for mass treatment are determined by the prevalence of clinical trachoma in a community, efficient and accurate methods for monitoring clinical activity remain a priority.2 However, reliability of clinical examination is poor and disagreement between graders is common.3 Photography of the conjunctiva could reduce variability and improve accuracy of trachoma surveillance. Currently, research studies use single-lens reflex (SLR) cameras to validate field grading.4 Yet, SLR cameras are expensive and require substantial field training to operate, and thus few trachoma programmes have adopted this technology. A simpler, more affordable camera may increase uptake of this diagnostic technique. In view of growing applications of mobile technology,5 we examined the use of smartphone imaging in trachoma. During a recent programme, Partnership for the Rapid Elimination of Trachoma (PRET study) visit in Niger, we performed the clinical examination, SLR, and smartphone photography of the everted right upper tarsal conjunctiva in 61 study participants.4 Study participants, aged 6 months to 5 years, were from four villages, each of which had received a mass azithromycin distribution one year prior. Clinical examinations were performed by a PRET-certified examiner with 2.5× magnifying loupe and a flashlight. Examiners used the simplified WHO grading scheme, which classifies follicular trachoma (TF) as the presence of at least five follicles ≥0.5 mm in diameter on the upper tarsal conjunctiva, and trachomatous inflammatory-intense (TI) as papillary hypertrophy and inflammatory thickening obscuring over half of the deep tarsal vessels.6 SLR photographs were taken by a PRET-certified photographer with a handheld Nikon D-40, with a 105 mm f/2.8D AF Macro Nikkor Autofocus lens, using manual settings with the flash engaged. Smartphone images, captured immediately after the SLR photo, were taken with an iPhone four camera using autofocus and without flash in order to minimise glare from the phone's screen. Photos were systematically cropped and resized to match the approximate size of the conjunctiva in the SLR images. Three PRET-certified trachoma graders reviewed the photographs independently and in random order within one sitting and without discussion. Latent Class Analysis was performed to assess test performance with both cameras and field grades given the absence of a gold standard. Sensitivities and specificities for the latent gold standard were obtained for (i) SLR photography; (ii) smartphone photography and; (iii) clinical field grades. For clinical activity, field grades had similar sensitivity to SLR photos, but higher specificity than both cameras. SLR photos were moderately more sensitive and more specific than the iPhone photos (table 1). While iPhone photos were the least sensitive for TF, compared with both the SLR photos and field grades, iPhone photos were the most sensitive for TI. However, iPhone photos were moderately less specific than both field grades and SLR photos. Table 1 Sensitivity, specificity and inter-grader reliability (κ) for trachoma grading (N=61) Active trachoma (TF and/or TI) TF TI Grade assigned N (%)  iPhone 25 (41.0%) 11 (18.0%) 16 (26.2%)  SLR 24 (39.3%) 20 (32.8%) 11 (18.0%)  Field grade 23 (37.7%) 20 (32.8%) 11 (18.0%) Sensitivity  iPhone 78% (63.9–95.3) 41% (26.1–94.4) 91% (82.4–99.4)  SLR 81% (69.0–95.4) 88% (68.0–94.3) 76% (50.5–94.4)  Field grade 81% (66.7–95.6) 88% (68.0–95.0) 76% (53.7–93.8) Specificity  iPhone 91% (80.8–100.0) 91% (83.1–100.0) 91% (83.1–100.0)  SLR 97% (89.2–100.0) 98% (88.2–100.0) 96% (90.8–99.4)  Field grade 100% (97.5–100.0) 98% (87.5–100.0) 96% (90.7–99.3) Inter-grader reliability  iPhone 0.86 (0.80–0.90) 0.63 (0.57–0.73) 0.83 (0.73–0.86)  SLR 0.78 (0.63–0.83) 0.76 (0.71–0.81) 0.65 (0.55–0.71) SLR, single lens reflex; TF, follicular trachoma; TI, trachomatous inflammatory-intense. The iPhone demonstrated moderate inter-grader reliability (table 1). iPhone inter-grader reliability was higher than SLR for active and TI grades. Inter-grader reliability was the highest for clinically active trachoma with the iPhone photographs. iPhones were less reliable for TF than SLR photos, but more reliable for TI. The advantages of photographic examinations include reproducible grading by centres of expertise, auditability, and increased accessibility to official graders. We were unable to demonstrate that the iPhone could be used in lieu of SLR photography, which has been considered costly. However, updates to the camera with newer smartphone models, an external lens attachment, and lighting adjustments could soon make smartphones a viable alternative to SLR photography. The ability to both share images through cellular data and capture relevant information electronically could dramatically facilitate accurate and efficient methods for diagnosis and treatment of blinding trachoma.

Validation of trachoma elimination requires monitoring after discontinuation of trachoma program activities, though such evaluations are not commonly done. Conjunctival examinations and smartphone photography were performed on a random sample of pre-school children from 15 villages in a region of Burkina Faso thought to have eliminated trachoma. No clinically active trachoma was detected by in-field or photographic evaluation. Smartphone images demonstrated high agreement with field grading (>99% concordance). Trachoma appears to have been eliminated from this area of Burkina Faso. Smartphone cameras may be a useful aid for monitoring in resource-limited settings.