Types of Vision Screening Devices (Continued)

Plus Optix has introduced a photoscreening instrument that allows detection of ocular misalignment in addition to an automated calculation of refractive error.  It is a handheld video/photorefractor that binocularly measures refractive error in 8 meridia and measures eye alignment.  Although field evaluation of this instrument has only recently begun, there are many advantages to the Power Refractor including automated interpretation and the ability to alter the referral criteria.

An earlier version of the Plus Optix instrument (Power Refractor) was tested in the VIP studies.  The purpose of the VIP study was to compare 11 preschool vision screening tests administered by licensed eye care professionals.  Sensitivity for detecting children with one or more targeted conditions (amblyopia, strabismus, significant refractive error, and unexplained visual acuity) at selected levels of specificity was the primary outcome measure.  The Power Refractor had a higher sensitivity than other photoscreening devices but was statistically significantly lower than the Retinomax autorefractor.  The study reported a screenability rate of 98.5%, a positive predictive value ranging from 50-60%, and a sensitivity of 54% when specificity was set to 90%. 

Dahlmann-Noor recently published one of the first studies evaluating the Plus Optix as a screening tool to detect risk factors for amblyopia by comparing it with gold standard orthoptic vision screening in children.  Results from a community-based screening of 288 children aged 4-7 reported a referral rate of 5.6% for the Plus Optix compared to a 12.5% referral rate from orthoptic screening.  However, the Plus Optix underestimated visually significant refractive errors and also indicated only moderate sensitivity (44%; 95% CI 27.9 to 61.9%) but a high specificity (100%; 95% CI 98.5 to 100%) to detect factors associated with amblyopia.   The authors of the study concluded that the using a single screening test in young children may miss a significant number of children with amblyopia or amblyogenic risk factors.

In another study published in 2008 by Matta, Singman, and Silbert the Plus Optix vision screener referred 67% of the 58 patients found to have amblyopia or amblyopia risk factors based on AAPOS referral criteria.  Matta and colleagues found the Plus Optix to also have a sensitivity of 98%, specificity of 69%, and false-negative rates of 1.4%.   For practical purposes, Arnold and Clausen pointed out in a separate study that estimated sensitivity, positive predictive value, and speed of objective photoscreeners exceeded that of visual acuity testing.

iScreen is a company which uses digital photography and a high quality photograph with off axis photo screening to detect amblyopia risk factors.    Their marketing plan typically places the screening device in the primary care doctor’s office with remote image transfer to a centralized location for interpretation.  Referral criteria are proprietary and have not been published.  Kennedy and Thomas demonstrated high sensitivity and specificity of the iScreen visual screening instrument when tested in the pediatric ophthalmologists’ office.  Results reported a sensitivity of 92.4% at a specificity of 89.1% when a total of 449 consecutive patients (median age 7 years) from a private pediatric ophthalmology practice underwent screening with the iScreen photoscreener.  In the VIP study, the iScreen device had nearly identical sensitivity as MTI Photoscreening with a screenability rate of 99.9%.  When failure criteria was set to obtain 94% specificity, the iScreen sensitivity for all of the targeted conditions was statistically significantly below the values of noncycloplegic retinoscopy, the Retinomax Autorefractor, the SureSight, and LEA Symbols Visual Acuity test.

An important advance in the interpretation of automated vision screening devices into primary care offices is a new CPT code for vision screening, 99174, which became effective January 1, 2008.  Its RVU value (0.68) recognizes photoscreening as a useful adjunct in the primary care office.  A statement encouraging the use of photoscreening for preschool vision screening has also been published by the American Academy of Pediatrics and is currently being updated.