The goal of the proposed project is the development and evaluation of a novel mobile medical application for the detection and monitoring of strabismus (eye misalignment). The image analysis technology necessary to measure strabismus using the corneal reflection technique (Photographic Hirschberg Test) has been available for many decades, however it has never been deployed using a smart phone. A smart phone platform will eliminate barriers of cost (since the hardware is maintained and updated by the smart phone industry), leading to rapid wide spread application and allowing the technology to finally reach its potential level of impact for children's eye care in the detection and management of strabismus. Strabismus causes visual confusion and double vision which ultimately results in the brain suppressing vision from the deviated eye. In children this results in under-development (amblyopia) with permanent vision loss in the deviated eye if not detected and treated at a young age. Strabismus in children is also associated with coordination problems such as postural instability and severe social disadvantages. Strabismus develops in an estimated 3-8% of children in the U.S. The prototype smart phone app (Referred to here as the Mobile Eye Alignment App - MEAA), uses photographic analysis of the corneal reflection (Purkinjie image) generated by the smart phone camera flash. The corneal reflection method uses the displacement of the reflection from the center of the pupil in the deviated eye to calculate the amount of eye misalignment. This measurement technique will be deployed for the proposed project using the hardware of the iPhone, a popular phone with an iOS operating system. Preliminary results suggest the app can measure differences in eye alignment of 1.6° (2.8 prism diopters). If successfully developed, the app has potential to be utilized to advance pediatric strabismus research by facilitating and reducing the cost of collecting enormous amounts of data from the general population and under-served or remote populations for epidemiological studies, and allowing researchers to capture eye alignment data much more frequently than is currently possible. Such a tool could better delineate the natural history of strabismus and perhaps help determine its causes. While devices are available which could make these measurements, the costs are prohibitively high (\>$3,000 ea.) and will not reach the widespread availability of smart phones. Clinical goals for the app are to provide eye doctors with an objective measurement tool in the exam room, allow daily monitoring of treatment effects, and eventually to be used as a screening tool by school nurses, pediatricians, and parents. The barriers to market success of stand-alone devices is not the accuracy sensitivity or specificity of photographic analysis technique which has been reported with sensitivity from 53% to near 90% and specificity ranging from 76% to 94% for strabismus detection. Impact of strabismus screening for the young - Early detection for strabismus in young children, especially during the critical period up to 2 years of age, is important to ensure that treatment is administered as soon as possible. The success of amblyopia treatment depends on several factors, but principally on the age of onset and the age at which the treatment is initiated. Therapy for amblyopia is maximally effective if started before age 3 and can be initiated as early as 8 months, underscoring the critical need for early and widespread access to strabismus screening. Indeed, countries with long-standing early vision screening programs have reported significantly reduced rates of amblyopia. Access to strabismus screening is also important for older, school age children (age 7-17) suffering from amblyopia, for whom treatment can lead to significant improvements in visual acuity ranging from 20%-70% of patients, depending on their age bracket.

Aims Specific Aim 1: Develop and test key functionality of the strabismus app by comparing measurements with successive versions of the prototype app to known angles of eye deviation (non-strabismic volunteers will gaze at off axis targets of known eccentricity). Specific Aim 2: Evaluate the strabismus app accuracy and feasibility in a clinical environment.

Primary Hypothesis: For strabismus ranging from 1 to 30 prism diopters (target range), the optimized version of the app will provide measurements which are not significantly different from the ground truth (simulated strabismus) or clinical tests of eye alignment.