Purpose: Angle of Deviation (AOD) and Prism Diopter (PD) measure the relative deviation between the eyes. Many conditions can cause misalignment of the eyes (Strabismus) and result in reduced visual acuity in one eye (Amblyopia). Misalignment may be observed in children; for most, it is self-limiting. However, some may develop strabismus, which, if left uncorrected, can lead to amblyopia and loss of peripheral vision and depth perception. Clinical examination for accurate measurement of eye alignment is highly technical and prone to variations and inaccuracies. In the absence of a validated testing platform, the clinical measurement has been used as the standard measurement. Our model provides a validated tool for calibration and accurate measurement of AOD and PD. Method: The application developed measures the eye alignment. We designed 3D-printed full-scale anatomical heads with interchangeable eye inserts that feature deviations in precise pupil position in both the horizontal and vertical planes. The application’s measurement was validated by evaluating the deviation of the 3D head model printed with precisely known variations. Results: Using the model created, we validated precise AOD and PD measurements with our app, PinpointEyes APP, as predicted by the mathematical models. Conclusion: The PinpointEyes 3D Model (PPEM) is an accurate platform that validates the AOD and PD measurements in research protocols. This provides a pathway to establish the standard for the precise measurement of AOD and PD. Translational Relevance: The model developed serves as a validation platform for the accurate measurement of PD and AOD.
References
[1]
de Jong, P.T.V.M. (2021) The Diopter. Eye, 35, 1801-1803. https://doi.org/10.1038/s41433-021-01419-y
[2]
Thompson, J.T. and Guyton, D.L. (1983) Ophthalmic Prisms: Measurement Errors and How to Minimize Them. Ophthalmology, 90, 204-210. https://doi.org/10.1016/s0161-6420(83)34572-3
[3]
España, E., Alvarez, M.T., Ojea, S. and Keshishian, A. (2025) Measuring Angle of Deviation, Prism Diopter in Children-Assessing Strabismus Using Smartphone Application. OpenJournalofOphthalmology, 15, 132-146. https://doi.org/10.4236/ojoph.2025.153018
[4]
Holmes, J.M., Chandler, D.L., Christiansen, S.P., Birch, E.E., Bothun, E., Laby, D., et al. (2009) Interobserver Reliability of the Prism and Alternate Cover Test in Children with Esotropia. Archives of Ophthalmology, 127, 59-65.
[5]
Freedman, K., Ray, C. and Kirk, D. (2019) Reevaluation of Current Prism Standards with Recommendations to Increase Accuracy in the Measurement of Strabismus. AmericanJournalofOphthalmology, 198, 130-135. https://doi.org/10.1016/j.ajo.2018.09.009
[6]
Lee, L., Feng, K.M., Chuang, P., Chen, Y. and Chien, K. (2023) Preliminary Data on a Novel Smart Glasses System for Measuring the Angle of Deviation in Strabismus. Eye, 37, 2700-2706. https://doi.org/10.1038/s41433-023-02402-5
[7]
Cestari, D., Mardiz, G., Bouzika, P., Rajtar, M., Keshishian, A. and Fortin, E. (2018) Evaluation of a Novel Smartphone App for the Automated Strabismus Measurements. https://collections.lib.utah.edu/details?id=1310604&facet_format_t=%22application%2Fpdf%22
[8]
Wang, P., Pan, Y., Zhang, J. and Yang, D. (2021) Measurement Errors Induced by Inaccurate Positioning of Ophthalmic Prisms and a Simple Way to Minimize Them. InternationalJournalofOphthalmology&VisualScience, 6, 59-62. https://doi.org/10.11648/j.ijovs.20210601.19
[9]
Rainey, B.B., Schroeder, T.L., Goss, D.A. and Grosvenor, T.P. (1998) Inter-Examiner Repeatability of Heterophoria Tests. OptometryandVisionScience, 75, 719-726. https://doi.org/10.1097/00006324-199810000-00016
[10]
Moschos, M.M. (2014) Physiology and Psychology of Vision and Its Disorders: A Review. Medical Hypothesis, Discovery and Innovation in Ophthalmology, 3, 83-90. https://pmc.ncbi.nlm.nih.gov/articles/PMC4348490/
[11]
De Nava, A.S.L., Somani, A.N. and Salini, B. (2023) Physiology, Vision. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK538493/
[12]
Solomon, S.G. and Lennie, P. (2007) The Machinery of Colour Vision. NatureReviewsNeuroscience, 8, 276-286. https://doi.org/10.1038/nrn2094
[13]
Ichinose, T. and Habib, S. (2022) On and off Signaling Pathways in the Retina and the Visual System. FrontiersinOphthalmology, 2, Article 989002. https://doi.org/10.3389/fopht.2022.989002
[14]
Fox, R.S. and Stern, C. (2023) The Effects of Modulated Light on the Visual Process. AdvancesinOphthalmologyandOptometry, 8, 15-26. https://doi.org/10.1016/j.yaoo.2023.03.009
[15]
Espinosa, J.S. and Stryker, M.P. (2012) Development and Plasticity of the Primary Visual Cortex. Neuron, 75, 230-249. https://doi.org/10.1016/j.neuron.2012.06.009
[16]
Qin, W. and Yu, C. (2013) Neural Pathways Conveying Novisual Information to the Visual Cortex. NeuralPlasticity, 2013, Article ID: 864920. https://doi.org/10.1155/2013/864920
[17]
Choi, R.Y. and Kushner, B.J. (1998) The Accuracy of Experienced Strabismologists Using the Hirschberg and Krimsky Tests. Ophthalmology, 105, 1301-1306.
[18]
Alhassan, M., Hovis, J.K. and Chou, R.B. (2015) Repeatability of Associated Phoria Tests. OptometryandVisionScience, 92, 900-907. https://doi.org/10.1097/opx.0000000000000638
[19]
Johnson, R., Wynn, S. and Coffey, B. (2004) Influences of Examiner Position and Effective Prism Power on Nearpoint Alternate Cover Test. Optometry—Journal of theAmericanOptometricAssociation, 75, 496-502. https://doi.org/10.1016/s1529-1839(04)70174-8
[20]
Korah, S., Philip, S., Jasper, S., Antonio-Santos, A. and Braganza, A. (2014) Strabismus Surgery before versus after Completion of Amblyopia Therapy in Children. CochraneDatabaseofSystematicReviews, No. 10, CD009272. https://doi.org/10.1002/14651858.cd009272.pub2
[21]
Dembinski, R.L., Collins, M.E. and Kraus, C.L. (2019) Outcomes Following Surgery for Horizontal Strabismus in Children of Lower Socioeconomic Backgrounds. Strabismus, 27, 47-53. https://doi.org/10.1080/09273972.2019.1626451
[22]
Cheng, W., Lynn, M.H., Pundlik, S., Almeida, C., Luo, G. and Houston, K. (2021) A Smartphone Ocular Alignment Measurement App in School Screening for Strabismus. BMCOphthalmology, 21, Article No. 150. https://doi.org/10.1186/s12886-021-01902-w
[23]
Pundlik, S., Tomasi, M., Liu, R., Houston, K. and Luo, G. (2019) Development and Preliminary Evaluation of a Smartphone App for Measuring Eye Alignment. TranslationalVisionScience&Technology, 8, Article 19. https://doi.org/10.1167/tvst.8.1.19
[24]
Wang, R., Lyu, J., Yang, Y., Bi, S., Yu, H., Deng, H., et al. (2025) A Smartphone-Based Digital Ruler to Automatically Measure Strabismus in Ophthalmologist-Level: A Prospective, Multicenter Cohort Study. NEJMAI, 2, 11. https://doi.org/10.1056/aioa2401205
[25]
Bekerman, I., Gottlieb, P. and Vaiman, M. (2014) Variations in Eyeball Diameters of the Healthy Adults. JournalofOphthalmology, 2014, Article ID: 503645. https://doi.org/10.1155/2014/503645
[26]
Ansari, A.S., Vehof, J., Hammond, C.J., Bremner, F.D. and Williams, K.M. (2021) Evidence That Pupil Size and Reactivity Are Determined More by Your Parents than by Your Environment. FrontiersinNeurology, 12, Article 651755. https://doi.org/10.3389/fneur.2021.651755
[27]
Lazar, R., Degen, J., Fiechter, A., Monticelli, A. and Spitschan, M. (2024) Regulation of Pupil Size in Natural Vision across the Human Lifespan. RoyalSocietyOpenScience, 11, Article ID: 191613. https://doi.org/10.1098/rsos.191613