An innovative filter for smartphones in tele-ophthalmology

Conventionally, corneal pathologies are photographed using slit lamp photography (SLP) units after staining them with fluorescein stain however, in situations where SLP is not available/possible (bedridden patients, during field medical/eye camps, infants, uncooperative patients etc.) it is difficult to capture fluorescein-stained images of the cornea. Although smartphones can capture good-quality ocular image, none have a blue filter to capture such images. Cobalt blue light unit (C-BLU) filter was developed in the department of Ophthalmology, All India Institute of Medical Sciences, Rishikesh, India, in August 2019.

This filter is a low-cost, pocket-sized adapter that can be used by anyone with a modern smartphone to obtain a clear image of the fluorescein-stained cornea (Fig. 1 and Video). The c-BLU filter can be mounted on any smartphone, where it uses of its native flashlight (Fig. 1B). The photographs captured with SLP (gold standard) (Fig. 2A, C, E and G) were compared with C-BLU filter images (Fig. 2B, D, F and H) and were comparable and reproducible. A number of corneal pathologies (Fig. 3) including a case of pseudomembranous conjunctivitis in a one month old neonate^† were photo-documented and monitored using C-BLU (Fig. 4). This can be an irreplaceable tool in the field of tele-ophthalmology and healthcare delivery when SLP is not available.

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Fig. 1 (A) Cobalt blue light unit (C-BLU) filter adapter consisting of an expandable smartphone holder arm (blue arrow) for housing the smartphone and the blue filter lens (green arrow) attached onto a movable length adjustable arm (red arrow). (B) C-BLU filter mounted on a smartphone using the expandable holder arm with the blue filter lens being aligned with the flashlight of the smartphone such that a cobalt blue light is emitted when the flashlight is turned on and image can be captured using the smartphone camera.

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Fig. 2 Photographs of common corneal pathologies acquired with slit lamp (A, C, E, and G) is being compared with C-BLU filter images (B, D, F, and H). (A-D) dry eye syndrome, (E and F) exposure keratopathy and (G and H) dendritic ulcer due to herpes simplex virus.

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Fig. 3 Various corneal pathologies have been captured using C-BLU filter and the corresponding corneal stain positive areas can be seen clearly. (A) Large epithelial defect due to firecracker. (B) limbal nodule preventing complete lid closure leading to inferior corneal exposure keratopathy. (C) Corneal laceration in superior cornea due to pencil stick injury. (D) Severe corneal ulcer and surrounding infiltrates.

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Fig. 4 (A) A one month old infant with pseudomembranous conjunctivitis was photographed using the C-BLU filter at various time-points. (B) A large epithelial defect with stain-positive areas on the cornea of infant on presentation. (C) The stain-positive areas have reduced in size after two days of treatment. (D) After four days of treatment, the epithelial defect shows regression with localization.

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Video available at ijmr.org.in.