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Objective Screening for Amblyopia: A New Paradigm?

ABCD response to the Rebiscan manuscript by Jost, et al.

Robert W. Arnold, MD, the Alaska Blind Child Discovery

2014: Photoscreening is becoming mainstream in pediatric practice since it allows reliable interpretations in infants and toddlers before they are able to be acuity screened.  Photoscreening makes use of eccentric flash photography, pupillary red reflex comparison and the linear relationship between the advancing light crescent as a function of refractive error for various pupil sizes.  Photoscreening has been validated, confirmed by the AAP[1] and has received reimbursement in many locations using a CPT code 99174.

AAPOS has developed a uniform method for validating photoscreeners designed for pre-verbal children based on the anatomic and refractive risk factors that lead to amblyopia[2].  The prevalence of amblyopia 20/40 or worse is about 2.5% whereas the prevalence of anatomic / cycloplegic refractive risk factors is 21%- a disparity mainly due to three common conditions: moderately high astigmatism, compensated hyperopia and intermittent strabismus that do not cause severe amblyopia in most children[3]. 

In addition to actual photoscreening, there are at least two other objective techniques to screen for amblyopia; autorefraction and birefringence screening.  A recent manuscript compares these two.

Jost, et al compare the decade-old, sequential, monocular Hartman-Shack autorefractor Welch Allyn Suresight with the not-yet commercialized Rebiscan (Pediatric Vision Screener) employing polarized bifoveal birefringence scanning[4]. The sensitivity and specificity- to detect strabismus and/or amblyopia for Suresight (using AAPOS? Referral criteria?) was 74% and 62% whereas for Rebiscan was 97% and 87%.  Rebiscan detected some straight-eyed anisometropia.

It would be very useful to know how these two objective screeners compare with photoscreeners.  Unfortunately, the current study, so new it does yet have pagination, cannot answer this question.  There could be many methods to validate a screening instrument[5]. Yost, et al, propose their own, non-uniform method.  Welch Allyn Suresight performed well in the NIH-sponsored Vision in Preschoolers Study (VIPS) that also proposed a non-uniform validation and instead was an internal calibration of the SureSight.

Since VIPS, Suresight has not performed very well.  Donahue recalibrated the Suresight refractive estimates to improve specificity, however the Suresight could not match the MTI photoscreeners in terms of ROC curve validation[6].  The new Jost comparative study does not use the manufacturer’s decade old interpretation, or the Donahue-improved criteria, but instead plug in the Confirmatory Exam AAPOS exam criteria rather than the intended instrument criteria.  This effectively hobbles the otherwise impotent Suresight, and makes the Rebiscan shine in comparison to Suresight.

Photoscreening has performed well in real-world screening.  Central reading centers using specific interpretation criteria have achieved referral rates as low as 5-7% with positive predictive value amblyopia risk factors of near 90%[7].  Computer-interpreted, infrared, multiradial photoscreeners can out-perform the MTI[8].  Toddlers identified by photoscreening can attain treatment acuity 33% better than children detected by photoscreening as preschoolers[9].  The photoscreener mainly identifies children who are unable to accommodate within 1.5 diopters of plano in one or both eyes, in one or more meridian.  Children with isolated amblyopic strabismus can be detected by parents[10].  ABCD suspects that significant amblyopia due only to small-angle, constant strabismus is extremely rare.

Much has been learned about amblyopia through carefully, collaborated, multi-center randomized trials by the Pediatric Eye Disease Investigator Group (PEDIG).  Busy pediatric ophthalmology and optometry practices are encouraged and rewarded to recruit as many amblyopic patients into the Amblyopia Treatment Studies (ATS) with the following exclusions (must be old enough to do enrollment EVA patched acuity, no other structural eye problems, no developmental delays, predicted to comply with follow-up).  Enrolled patients fall into four groups: 30% pure strabismic (large angle > 20 pd), 30% anisometropic, 30% mixed refractive- strabismic and 10% bilateral ametropic[11].  PEDIG findings can be summarized: 1) refractive and some strabismic amblyopes gain 2-4 lines of acuity with spectacle treatment alone[12], 2) Part time patching (2hrs = 6 hrs)[13] and/or atropine 2-7 times per week[14] in the sound eye adds 1-2 lines acuity gain, and 3) long term amblyopia success is better when treatment is started early (age 3-4 years versus 5-7 years)[15].  PEDIG investigators cannot improve mean amblyopia acuity to better than 20/32 if treatment starts at an age when children perform visual acuity screening.

Despite PEDIG’s best efforts, some children- usually with mixed refractive – strabismic amblyopia have poor (less than driving) vision even after 5-7 years of thorough, complaint treatment.  These difficult patients (<10% of PEDIG amblyopies and therefore 0.25% of all children) appear to have fixation instability.

It would be helpful to find these severe strabismic amblyopic children earlier.  Enter David Hunter’s and David Guyton’s birefringence screener.  In order for the Rebiscan to “pass” a patient, the instrument must detect radially polarized refractions from both eyes representing binocular foveation.

ABCD calls for a re-evaluation of Jost’s data employing AAPOS validation criteria to determine the uniform comparison of the Rebiscan, and to determine the relative merit of their new validation technique.

References:

1.         Miller JM, Lessin HR, AAP: Instrument-based pediatric vision screening policy statement. Pediatrics 2012, 130(5):983-986.

2.         Donahue SP, Arthur B, Neely DE, Arnold RW, Silbert D, Ruben JB: Guidelines for automated preschool vision screening: A 10-year, evidence-based update. J AAPOS 2013, 17(1):4-8.

3.         Arnold RW: Amblyopia risk factor prevalence. J Pediatr Ophthalmol Strabismus 2013, 50(4):213-217.

4.         Jost RM, Yanni SE, Beauchamp CL, Stager DR, Sr., Stager D, Jr., Dao L, Birch EE: Beyond Screening for Risk Factors: Objective Detection of Strabismus and Amblyopia. JAMA ophthalmology 2014.

5.         Arnold RW, Armitage MD: Performance of four new photoscreeners on pediatric patients with high risk amblyopia. J Pediatr Ophthalmol Strabismus 2014, 51(1):46-52.

6.         Rowatt AJ, Donahue SP, Crosby C, Hudson AC, Simon S, Emmons K: Field evaluation of the Welch Allyn SureSight vision screener: incorporating the vision in preschoolers study recommendations. J AAPOS 2007, 11(3):243-248.

7.         Longmuir SQ, Pfeifer W, Leon A, Olson RJ, Short L, Scott WE: Nine-year results of a volunteer lay network photoscreening program of 147 809 children using a photoscreener in Iowa. Ophthalmology 2010, 117(10):1869-1875.

8.         Matta NS, Arnold RW, Singman EL, Silbert DI: Comparison between the plusoptiX and MTI Photoscreeners. Arch Ophthalmol 2009, 127(12):1591-1595.

9.         Kirk VG, Clausen MM, Armitage MD, Arnold RW: Preverbal photoscreening for amblyogenic factors and outcomes in amblyopia treatment: early objective screening and visual acuities. Arch Ophthalmol 2008, 126(4):489-492.

10.       Rosner J, Rosner J: Parents as screeners for strabismus in their children. J Visual Impair Blindness 1988, 82:193-194.

11.       Wallace DK, Chandler DL, Beck RW, Arnold RW, Bacal DA, Birch EE, Felius J, Frazier M, Holmes JM, Hoover D et al: Treatment of bilateral refractive amblyopia in children three to less than 10 years of age. Am J Ophthalmol 2007, 144(4):487-496.

12.       PEDIG, Cotter SA, Edwards AR, Wallace DK, Beck RW, Arnold RW, Astle WF, Barnhardt CN, Birch EE, Donahue SP et al: Treatment of anisometropic amblyopia in children with refractive correction. Ophthalmology 2006, 113(6):895-903.

13.       PEDIG, Wallace DK, Edwards AR, Cotter SA, Beck RW, Arnold RW, Astle WF, Barnhardt CN, Birch EE, Donahue SP et al: A randomized trial to evaluate 2 hours of daily patching for strabismic and anisometropic amblyopia in children. Ophthalmology 2006, 113(6):904-912.

14.       PEDIG, Repka MX, Cotter SA, Beck RW, Kraker RT, Birch EE, Everett DF, Hertle RW, Holmes JM, Quinn GE et al: A randomized trial of atropine regimens for treatment of moderate amblyopia in children. Ophthalmology 2004, 111(11):2076-2085.

15.       PEDIG, Holmes JM, Lazar EL, Melia BM, Astle WF, Dagi LR, Donahue SP, Frazier MG, Hertle RW, Repka MX et al: Effect of age on response to amblyopia treatment in children. Arch Ophthalmol 2011, 129(11):1451-1457.

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