Prescribing Yoked Prism Lenses- Examiner Agreement Using the Kaplan Nonverbal Battery

Background:

Autism Spectrum Disorder (ASD) is marked by deficits in social communication and behavior, and difficulties in sensorimotor function, including visual processing.^1,2 Yoked prism lenses, an optometric intervention, target dysfunctions in the ambient vision system. ASD individuals wearing yoked prism lenses have demonstrated improvements in posture, spatial awareness, and behavior in double blind studies^.3,4 Though results support clinical application, prescribing studies have been limited to one single investigator team ^5,6 This study evaluates the clinical method for determining yoked prism prescriptions for ASD individuals using the Kaplan Nonverbal Battery (KNB). The KNB is a series of nine tasks that do not require verbal response from patients; it is scored using a 5-point scale focusing on 39 facets of the tasks.⁷

Objectives:

To determine inter-examiner agreement between two masked examiners evaluating yoked prism prescription using the KNB by live and video presentation.

To determine intra-examiner agreement between two masked examiners evaluating habitual correction using the KNB by live and video presentation.

Methods:

Ten nonverbal, or minimally verbal, ASD subjects between 9 and 17 years old were enrolled and completed a comprehensive eye examination. All subjects adapted to spectacles by wearing their refractive correction, or plano lenses if emmetropic, for four weeks. Subjects then completed two videotaped study visits; at each visit, they completed the KNB wearing their habitual spectacle correction and then wearing yoked prism lenses of five-prism diopters base up or down. Two examiners assessed subjects’ performance on the KNB live. Two other examiners assessed the subjects’ performance via video recordings. Examiners were masked to the prescription of the yoked prism lenses and other examiner responses. Agreement between and within examiners was computed using the weighted version of Cohen’s kappa.

Results:

Nine out of ten subjects completed both study visits and all nine tasks of the KNB. Inter-examiner and intra-examiner agreement were calculated for both the live and video presentations. Both inter-examiner and intra-examiner agreement were markedly better when examiners scored results using video presentation. In the yoked prism lenses evaluation, overall inter-examiner agreement for live presentation was 0.726 (visit 1) and 0.357 (visit 2), but on video presentation increased to 0.702 (visit 1) and 0.678 (visit 2). In evaluation of the habitual correction, intra-examiner agreement on live presentation was 0.451 for examiner 1 and 0.579 for examiner 2, but increased to 0.861 for examiner 3 and 0.875 for examiner 4.

Conclusions:

Masked examiners using the KNB to determine the yoked prism prescription for nonverbal or minimally verbal ASD children showed good inter-examiner agreement when evaluating videotaped presentation, but not by live presentation. Intra-examiner agreement in assessing KNB when the subject wore their habitual correction also was very good. Clinicians and investigators using the KNB to determine yoked prism prescription show good agreement when evaluating videotaped performance.