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Alaska Blind Child Discovery

A cooperative, charitable research project to vision screen every preschool Alaskan



Predictive Value of Inexpensive Digital Eye and Vision Photoscreening
Robert W. Arnold, MD, Michelle Clausen, BA, Holly Ryan, Rachel E. Leman, Diane Armitage, certified Orthoptist
a. Purpose:
Some consumer digital cameras have flash-lens distance ideal for photoscreening so we adapted them to an ongoing state-wide vision screening program.
b. Methods:
Digital cameras with short flash-lens distance were employed by lay screeners trained by DVD movie. Confirmatory exam by AAPOS criteria were sought from eye doctors.
c. Results:
2900 children were screened in 62 clinics by 14 screeners. 99% were readable with 6% referred. The positive predictive value was estimated as greater than 80%. The per-screening image cost was less than $100 including cameras. Some screeners interpreted images similar to central reading center.
d. Conclusion:
Pre-literate community photoscreening can be valid and cost-effective.

The American Academy of Pediatrics (AAP) recommends a series of age-appropriate vision screens over the entire course of a child’s first (amblyopia) decade1 however AAP was not yet ready in 2002 to mandate preschool, objective photoscreening. The NIH-supported Vision in PreSchoolers Studies (VIPS) used disparate outcome measures to suggest that photoscreening, in the hands of pediatric optometrists, was less sensitive than patched acuity testing or remote autorefraction. This differs from the experience of the initial large-scale validation. Small pediatric-office based validation studies criticized the high variability of photoscreening image interpretation, however large-scale centralized programs can achieve more consistently high predictive value.
The issue of MTI photoscreener cost, and lack of availability, and the experience with EyeDx digital camera, prompted investigation into certain emerging commercial digital cameras with short flash-to-lens dimensions as alternatives. In addition to two other short reports, this is the Alaska Blind Child Discovery (ABCD) experience adapting inexpensive digital flash cameras (Amblyopia Detection by Camera- ADBC) to community pediatric vision screening.
ABCD has adapted several types of consumer digital flash cameras to screening primarily including the JVC DVM70u, the Gateway DV-S20, and the Nikon CoolPix S04. ABCD has calibrated these and other pediatric vision screening devices for AAPOS-threshold levels of hyperopic anisometropia using a normal subject and induced anisometropia via contact lens. Photoscreening images are interpreted by the “Delta-Center Crescent” method. Physicians at the ABCD coordinating center use the delta center crescent method which can be taught to lay screeners using an educational video DVD.
Digital photoscreening had a referral rate of about 9% with PPV of 87% whereas MTI photoscreening had a referral rate of 7% and a PPV of 85%. The inconclusive rate for digital was 1.1% and for MTI 0.6%. The slightly higher PPV (94%) were for community JVC DVM70u screening and for school Gateway and MTI photoscreening using a tent. The lowest PPV (60%) came from community non-tent, Gateway photoscreening usually because of poor fixation or too short a distance between camera and child, which washed out the images.
Several photoscreener manufacturers are no longer financially viable. The ideal photoscreener would be portable, child-friendly, fast, on-site interpreted, referral-criteria modifiable, able to work in variable light and noise environments. Technology representing many of these features are still available at a cost. Until then, certain consumer digital flash cameras with a small flash-to-lens can provide valid and inexpensive community detection of amblyopia.

Arnold RW, Clausen M, Ryan H, Leman RE, Armitage D. Predictive Value of Inexpensive Digital Eye and Vision Photoscreening: "PPV of ABCD". Binocul Vis Strabismus Q 2007;22:148-52.

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