Name: Using an Automated Hirschberg Test App to Evaluate Ocular Alignment (Video) | JoVE Journal
Uploaded: 2020-03-24T15:00:00.000+00:00
Duration: 5 min 40 s
Description: Learn to measure strabismus using an automated smartphone Hirschberg test app for clinical and research applications. This method enables accurate ocular alignment assessment with minimal training requirements.

ai_agent_IP

ai_agent

maintenance

instantTrialDurationMinutes

isBiopharma

enableNewMyJoveSectionDesign

educationFeatures

seoMetaApi

ai_copilot_institution_blacklist

ai_chat_institution_blacklist

freeAccessWindow

ssoRoleCapture

scheduledMaintenanceBanner

joveLabsFeatures

disable_autoplay_for_bots

extended_trial_duration

5 minutes

This work was supported in part by NIH grant R44EY025902 and by the Mass Eye &#38; Ear Curing Kids Grant.

This study was conducted in accordance with the tenets of the Declaration of Helsinki, at Schepens Eye Research Institute (Boston, MA) and Spaulding Rehabilitation Hospital (Boston, MA). Informed consent was obtained from all the participants. The study was approved by the local institutional review boards of Mass Eye and Ear (Boston, MA).
NOTE: Patient inclusion criteria were prior diagnosis of horizontal strabismus (constant or intermittent exotropia or esotropia) and no other visual impairments. This study was a part of a larger one reported previously12. Data for 14 patients recruited in the US in the larger study12 are reported here with permission. An optometrist specialized in vision rehabilitation who routinely evaluate strabismus in clinic performed prism and alternate cover test, following by measurement with the app to prevent bias of the cover test results by the objective app measurement.
1. Prepare the test
NOTE: Testing can be performed in any environment; however, the following controls are likely to aid in successful testing.
<ol>
	<li>Conduct the test in a well-lit environment. Let the patients face in a direction such that corneal reflections from windows and ceiling lights are not located in the center of the eyes. Try to avoid strong background light, such as windows. 
	NOTE: Usually it helps to have a ceiling light right above the head, or a window on one side of the patient. Sometimes, asking the patient to hold their hand above their brow or using a visor can help shield the eyes from strong light sources which create additional reflections on the cornea, as needed. Turning off point light sources such as canister lights or gooseneck lamps will decrease the intensity of extra corneal reflections, making it easier for the software to detect the reflection from the camera flash as intended. If point light source is needed it may be diffused by pointing it at the wall or using a diffuser (i.e., lamp shade).</li>
</ol>
2. Measure tropia (manifest strabismus) with single snapshot&#8722;near fixation
<ol>
	<li>Launch the app and set the mode to No Cover (button at upper right corner).</li>
	<li>Select near fixation (button at lower right corner).</li>
	<li>Hold the phone in landscape orientation about 40 cm from the patient at eye level with the rear-camera facing the patient to be measured. 
	NOTE: The distance does not have to be accurately controlled. The app can automatically compensate for different distances.</li>
	<li>Instruct the patient to fixate on the flash light, which is off at this point. For tests requiring precise accommodation such as when screening for accommodative esotropia, paste a fixation target (such as a letter) on the back of the phone, directly below or above the flashlight.</li>
	<li>While the patient confirms he/she is fixating, press the round button to take a snapshot, which will be analyzed by the app.</li>
	<li>When the analysis is completed, the app will show detected eye features: limbus (iris outer) boundary indicated by a large circle (green), the center of the eye indicated by a cross (green), and the location of the corneal reflection indicated by a small circle (red). Verify these features are detected without obvious errors (such as incorrect limbus fitting, or incorrect location or missing corneal reflection).</li>
	<li>On the same screen, under the captured picture, the app will show the measurements related to the eye alignment. If satisfied with the results, press the save button to save the current test in the phone. Otherwise, press the back-arrow button to retest.</li>
</ol>
3. Measure tropia (manifest strabismus) with snapshot&#8722;far fixation
NOTE: To measure tropia for far fixation, the angle kappa for each eye needs to be measured at least once. The app will automatically choose the latest measurement of angle kappa in the history. If it is not available for either eye, the app will give a reminder to first obtain this measurement (see section 6 for details of angle kappa measurement).
<ol>
	<li>Launch the app and set the mode to No Cover (button at upper right corner).</li>
	<li>Select far fixation mode (button at lower right corner).</li>
	<li>Hold the phone in landscape orientation about 40 cm from the patient at eye level with the rear face of the phone facing the patient. 
	NOTE: The distance does not have to be accurately controlled. The app can automatically compensate for different distances.</li>
	<li>Place the phone slightly below two eyes so that the patient can look above the phone and fixate a target in the distance (typically 5 m away). Make sure the camera is in approximately between the two eyes, not too far to the side of either eye.</li>
	<li>While making sure the patient is fixating properly, press the round button to take a snapshot.</li>
	<li>When the analysis is completed, the app will show detected eye features: limbus boundary indicated by a large circle (green), the center of the eye indicated by a cross (green), and the location of the corneal reflection indicated by a small circle (red). Verify these features are detected without obvious errors (such as incorrect limbus fitting, or incorrect location or missing corneal reflection).</li>
	<li>Under the picture there are measurement outcomes for eye alignment including prism diopters. If satisfied with the results, press the save button to save the test in the phone. Otherwise, press the back-arrow button to retest.</li>
</ol>
4. Measure intermittent strabismus or phoria with cover test&#8722;near fixation
<ol>
	<li>Launch the app and toggle on the cover test mode (button at upper right corner), and select near fixation (button at lower right corner).</li>
	<li>Hold the phone in landscape orientation about 40 cm from the patient. 
	NOTE: The distance does not have to be accurately controlled. The app can automatically compensate for different distances.</li>
	<li>Instruct the patient to fixate the flash light, which is turned off at this point. For tests requiring precise accommodation, paste a fixation target on the back of the phone, directly below or above the flashlight.</li>
	<li>Use an occluder to cover one of the eyes.</li>
	<li>Press the round button. The app will start to monitor the status of the two eyes (whether one eye is covered).</li>
	<li>While making sure the patient is fixating properly, remove the occluder quickly (i.e., cover-uncover test), or first move the occluder between the two eyes to perform alternate covering a few times and then take the occluder away quickly. The app will automatically take a picture as soon as the occlude is taken away from eyes.</li>
	<li>When the analysis is completed, the app will show detected eye features: iris indicated by a large green circle, the center of the eye indicated by a green cross, and corneal reflection from flash indicated by a small red circle. Verify these features are detected without obvious errors.</li>
	<li>Under the picture there are measurement outcomes for eye alignment in prism diopters. If satisfied with the results, press the save button to save the test in the phone. Otherwise, press the back-arrow button to retest.</li>
</ol>
5. Measure intermittent strabismus or phoria with cover test&#8722;far fixation
NOTE: To measure intermittent ocular misalignment for far fixation, the angle kappa for each eye needs to be measured at least once. The app will automatically choose the latest angle kappa measure. If it is not available for either eye, the app will give a reminder to first obtain this measurement (see section 6 for details of angle kappa measurement).
<ol>
	<li>Launch the app and set the mode to cover test (button at upper right corner).</li>
	<li>Select far fixation (button at lower right corner).</li>
	<li>Hold the phone in landscape orientation about 40 cm from the patient at eye level. 
	NOTE: The distance does not have to be accurately controlled. The app can automatically compensate for different distances. It is best if the flash light/camera is between the eyes. Since the camera and flash are off to one corner in most phone models, this means the phone display itself will be slightly off-center.</li>
	<li>Instruct the patient to look just above the phone and to fixate the target in distance (typically 6 m away).</li>
	<li>Use an occluder to cover an eye.</li>
	<li>Press the round button. The app will start to detect the uncovering of the eye.</li>
	<li>While making sure the patient is fixating properly, remove the occluder quickly (i.e., cover-uncover test), or first move the occluder between the two eyes to perform alternate covering a few times and then take the occluder away quickly. The app will automatically take a picture as soon as the occluder is taken away from eyes.</li>
	<li>When the analysis is completed, the app will show detected eye features: limbus boundary indicated by a large circle (green), the center of the eye indicated by a cross (green), and the location of the corneal reflection indicated by a small circle (red). Verify these features are detected without obvious errors (such as incorrect limbus fitting, or incorrect location or missing corneal reflection).</li>
	<li>Under the picture there are measurement outcomes for eye alignment in prism diopters. If satisfied with the results, press the save button to save the test in the phone. Otherwise, press the back-arrow button to retest.</li>
</ol>
6. Measure angle kappa
<ol>
	<li>Launch the app.</li>
	<li>Select Measure angle kappa.</li>
	<li>Hold the phone in landscape orientation about 40 cm from the patient at eye level. 
	NOTE: The distance does not have to be accurately controlled. The app can automatically compensate for different distances.</li>
	<li>Instruct the patient to use the eye to be tested (either eye) to fixate on the flash light, which is off at this point. Have the other covered by hand or an occluder.</li>
	<li>While making sure the patient is fixating properly, tap the round button to take a snapshot, which will be analyzed by the app.</li>
	<li>When the analysis is completed, the app will show the detected eye features: limbus boundary indicated by a large circle (green), the center of the eye indicated by a cross (green), and the location of the corneal reflection indicated by a small circle (red). Verify these features are detected without obvious errors (such as incorrect limbus fitting, or incorrect location or missing corneal reflection). Under the picture there are measurement outcomes for angle kappa (in degrees).</li>
</ol>

<ol><li>Kemper, A. R., Clark, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Preschool+vision+screening+in+pediatric+practices%5BTitle%5D)+AND+%22Clinical+Pediatrics%22%5BJournal%5D)">Preschool vision screening in pediatric practices.</a> Clinical Pediatrics. 45 (3), 263-266 (2006).</li>
<li>Rowe, F. VIS group UK. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+profile+of+strabismus+in+stroke+survivors%5BTitle%5D)+AND+%22Eye%22%5BJournal%5D)">The profile of strabismus in stroke survivors.</a> Eye. 24 (4), 682-685 (2010).</li>
<li>Black, K., McCarus, C., Collins, M. L. Z., Jensen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Ocular+Manifestations+of+Autism+in+Ophthalmology%5BTitle%5D)+AND+%22Strabismus%22%5BJournal%5D)">Ocular Manifestations of Autism in Ophthalmology.</a> Strabismus. 21 (2), 98-102 (2013).</li>
<li>Taylor, K., Elliott, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Interventions+for+strabismic+amblyopia%5BTitle%5D)+AND+%22Cochrane+Database+of+Systematic+Reviews%22%5BJournal%5D)">Interventions for strabismic amblyopia.</a> Cochrane Database of Systematic Reviews. 10 (8), (2011).</li>
<li>Cotter, S. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Fixation+preference+and+visual+acuity+testing+in+a+population-based+cohort+of+preschool+children+with+amblyopia+risk+factors%5BTitle%5D)+AND+%22Ophthalmology%22%5BJournal%5D)">Fixation preference and visual acuity testing in a population-based cohort of preschool children with amblyopia risk factors.</a> Ophthalmology. 116 (1), 145-153 (2009).</li>
<li>Robaei, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Factors+Associated+with+Childhood+Strabismus%3A+Findings+from+a+Population-Based+Study%5BTitle%5D)+AND+%22Ophthalmology%22%5BJournal%5D)">Factors Associated with Childhood Strabismus: Findings from a Population-Based Study.</a> Ophthalmology. 113 (7), 1146-1153 (2006).</li>
<li>Tarczy-Hornoch, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Risk+factors+for+decreased+visual+acuity+in+preschool+children%3A+the+multi-ethnic+pediatric+eye+disease+and+Baltimore+pediatric+eye+disease+studies%5BTitle%5D)+AND+%22Ophthalmology%22%5BJournal%5D)">Risk factors for decreased visual acuity in preschool children: the multi-ethnic pediatric eye disease and Baltimore pediatric eye disease studies.</a> Ophthalmology. 118 (11), 2262-2273 (2011).</li>
<li>Chan, K. W., Deng, L., Weissberg, E. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Detection+of+Strabismus+by+Non-Health+Care+Professionals+in+an+Ethnically+Diverse+Set+of+Images%5BTitle%5D)+AND+%22JAMA+Ophthalmology%22%5BJournal%5D)">Detection of Strabismus by Non-Health Care Professionals in an Ethnically Diverse Set of Images.</a> JAMA Ophthalmology. 134 (1), 30-36 (2016).</li>
<li>Hunter, D. G., Guyton, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Vertical+location+of+the+corneal+light+reflex+in+strabismus+photography%5BTitle%5D)+AND+%22Archives+of+Ophthalmology%22%5BJournal%5D)">Vertical location of the corneal light reflex in strabismus photography.</a> Archives of Ophthalmology. 116 (6), 767-771 (1998).</li>
<li>Eskridge, J. B., Wick, B., Perrigin, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+Hirschberg+test%3A+a+double-masked+clinical+evaluation%5BTitle%5D)+AND+%22American+Journal+of+Optometry+and+Physiological+Optics%22%5BJournal%5D)">The Hirschberg test: a double-masked clinical evaluation.</a> American Journal of Optometry and Physiological Optics. 65 (9), 745-750 (1988).</li>
<li>Hasebe, S., Ohtsuki, H., Tadokoro, Y., Okano, M., Furuse, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+reliability+of+a+video-enhanced+Hirschberg+test+under+clinical+conditions%5BTitle%5D)+AND+%22Investigative+Ophthalmology+%26+Visual+Science%22%5BJournal%5D)">The reliability of a video-enhanced Hirschberg test under clinical conditions.</a> Investigative Ophthalmology & Visual Science. 36 (13), 2678-2685 (1995).</li>
<li>Pundlik, S., Tomasi, M., Liu, R., Houston, K., Luo, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Development+and+Preliminary+Evaluation+of+a+Smartphone+App+for+Measuring+Eye+Alignment%5BTitle%5D)+AND+%22Translational+Vision+Science+%26+Technology%22%5BJournal%5D)">Development and Preliminary Evaluation of a Smartphone App for Measuring Eye Alignment.</a> Translational Vision Science & Technology. 8 (1), 19(2019).</li>
<li>Cheng, W., et al. The EyeTurn App for School Vision Screening. American Academy of Optometry Annual Meeting. San Antonio, TX, , (2018).</li>
<li>Committee on Practice and Ambulatory Medicine and Section on Ophthalmology. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Use+of+Photoscreening+for+Children%27s+Vision+Screening%5BTitle%5D)+AND+%22Pediatrics%22%5BJournal%5D)">Use of Photoscreening for Children's Vision Screening.</a> Pediatrics. 109 (3), 524-525 (2002).</li>
<li>Simons, B. D., Siatkowski, R. M., Schiffman, J. C., Berry, B. E., Flynn, J. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pediatric+photoscreening+for+strabismus+and+refractive+errors+in+a+high-risk+population%5BTitle%5D)+AND+%22Ophthalmology%22%5BJournal%5D)">Pediatric photoscreening for strabismus and refractive errors in a high-risk population.</a> Ophthalmology. 106 (6), 1073-1080 (1999).</li>
<li>Kerr, N. C., Somes, G., Enzenauer, R. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+effect+of+developmentally-at-risk+status+on+the+reliability+of+the+iScreen%28R%29+photorefractive+device+in+young+children%5BTitle%5D)+AND+%22The+American+Journal+of+Orthopedics%22%5BJournal%5D)">The effect of developmentally-at-risk status on the reliability of the iScreen(R) photorefractive device in young children.</a> The American Journal of Orthopedics. 61, 117-123 (2011).</li>
<li>Arnold, R. W., O'Neil, J. W., Cooper, K. L., Silbert, D. I., Donahue, S. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Evaluation+of+a+smartphone+photoscreening+app+to+detect+refractive+amblyopia+risk+factors+in+children+aged+1-6+years%5BTitle%5D)+AND+%22Clinical+Ophthalmology%22%5BJournal%5D)">Evaluation of a smartphone photoscreening app to detect refractive amblyopia risk factors in children aged 1-6 years.</a> Clinical Ophthalmology. 12, 1533-1537 (2018).</li>
</ol>

All authors have a pending patent application on a method of measuring strabismus using a smartphone camera. The technology is being commercialized by EyeNexo LLC, which was founded by authors GL, PS, MT and KH, under a license from Mass Eye and Ear.

A person without professional training can use the EyeTurn app to capture pictures of the eyes and obtain ocular alignment measurements, which might be interpreted by an eye care specialist onsite or remotely. The app only provides magnitude of the misalignment, rather than any interpretation or diagnosis. Eye care professionals such as optometrists or ophthalmologists should determine if the misalignment is significant or not, and make a diagnosis after considering other factors including the conditions under which the ...

Measurement of eye alignment is frequently performed in vision care clinics. Cover test with prism neutralization is the commonly used clinical method for quantifying the degree of eye misalignment (strabismus). This method requires a high degree of training and experience. Accurate measurement becomes more challenging when patients cannot fully engage in the exam such as young children1, individuals with brain injuries or stroke2, or developmental disabilities3. Furthermore, there is a need for ocular alignment testing in school screening, because strabismus develops during childhood in an estimated 5&#8722;8% of the US population4, and is a substantial risk factor for amblyopia with about 30&#8722;40% of cases of amblyopia attributed to strabismus5,6,7. However, school nurses are normally not trained to conduct the standard cover test with prism neutralization for such screening. For non-eye care professionals, an additional challenge in strabismus screening is that intermittent strabismus (misalignment is not always manifested) and smaller magnitudes of misalignment are not visually obvious (&#60;15 prism diopters [&#916;])8.
In an attempt to address the challenges in the detection and measurement of strabismus, we have developed a smartphone app (EyeTurn) that implements and automates the photographic Hirschberg method9 by comparing the displacement of corneal reflections between the eyes. While conventional photographic Hirschberg method has been shown to have good reproducibility in clinics10,11, the cost for dedicated, standalone devices is a barrier for wide adoption. By providing an easy-to-use tool to measure eye alignment with standard smartphones, we hypothesize it will be widely adopted in school vision screening and used by non-eye care professionals. Our previous evaluation studies have shown that the app measurement is consistent with the current clinical standard of prism and alternate cover test12, for strabismus magnitudes of esotropia and exotropia up to 60&#916;. In a pilot school screening study, we also showed that the app can help the school nurse detect children with intermittent exotropia who were missed by standard school vision screening protocols13.
The iOS version of the app is currently available to researchers and clinicians upon request for research purposes. The requesters have thus far included school nurses, pediatric ophthalmologists, optometrists, neuro-ophthalmologists, and strabismus specialists. The purpose of this article is to share the detailed app protocols for using the app to evaluate ocular alignment under different viewing conditions, namely, near and far fixation distance; with and without eye covering to break binocular fusion.

<table><tbody><tr><td>EyeTurn</td><td>EyeNexo</td><td></td><td>Smartphone app for measureing eye misalignment</td></tr></tbody></table>

using an automated hirschberg test app to evaluate ocular alignment

Using an Automated Hirschberg Test App to Evaluate Ocular Alignment

A smartphone app has been developed to perform the automated photographic Hirschberg test for objective measurement of ocular misalignment. By computing the difference in corneal reflection generated by the phone camera flash relative to the iris center based on high resolution images, the app can measure misalignment with a much higher precision than the naked eye performing the Hirschberg test. It has been validated in a previous clinical evaluation study by comparing to the clinical gold standard-prism and alternate cover test. The goal of this article is to describe the testing techniques regarding how to use the app to measure ocular alignment for different fixation distances, without or with cover to break fusion, as well as angle kappa, so that users can use the app to perform equivalent tests typically done in clinic using prisms.

In this work, we describe the protocols to evaluate ocular alignment using a smartphone app that performs the photographic Hirschberg test. The interface of the app is shown in Figure 1. The users can choose to perform cover test or measure a patient with both eyes fixating at a target simultaneously, either at near or far fixation distances. Once the viewing conditions are determined depending on the test purposes, the users can follow the protocols and take...

We present a protocol of using a smartphone app to perform Hirschberg test for measuring manifest and intermittent ocular misalignment (strabismus) under near and far fixation conditions.

A smartphone app has been developed to perform the automated photographic Hirschberg test for objective measurement of ocular misalignment. By computing ...

using-an-automated-hirschberg-test-app-to-evaluate-ocular-alignment

Research

JoVE Journal

Medicine

This protocol describes the scanning light scattering profiler (SLSP) that enables the full-angle quantitative evaluation of forward and backward scattering of light from intraocular lenses (IOLs) using goniophotometer principles.

Scanning Light Scattering Profiler (SLPS) Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

This manuscript describes a protocol for the in vivo imaging of the mouse retina with high-resolution spectral domain optical coherence tomography (SD-OCT). It focuses on retinal ganglion cells (RGC) in the peripapillary region, with several scanning and quantifying approaches described.

Optical Coherence Tomography: Imaging Mouse Retinal Ganglion Cells In Vivo

This protocol describes how to correctly perform the video head impulse test with two separate test systems commonly used worldwide. Both the 2D and 3D video head impulse test methods are described.

Testing of all Six Semicircular Canals with Video Head Impulse Test Systems

The present research demonstrates a method to accurately examine dynamic visual acuity (DVA) in myopic subjects with eyeglass correction. Further analysis indicated that the closer the refraction state to emmetropia, the better the eyeglass-corrected binocular DVA is at both 40 and 80 degrees per second.

Binocular Dynamic Visual Acuity in Eyeglass-Corrected Myopic Patients

VisualEyes2020 (VE2020) is a custom scripting language that presents, records, and synchronizes visual eye movement stimuli. VE2020 provides stimuli for conjugate eye movements (saccades and smooth pursuit), disconjugate eye movements (vergence), accommodation, and combinations of each. Two analysis programs unify the data processing from the eye tracking and accommodation recording systems.

Quantification of Oculomotor Responses and Accommodation Through Instrumentation and Analysis Toolboxes

In this paper, we present a novel automated method for assessing visual acuity in infants and toddlers by using an eye-tracking system.

An Automated Method for Assessing Visual Acuity in Infants and Toddlers Using an Eye-Tracking System

Anterior segment high-resolution optical coherence tomography (HR-OCT) is a promising non-invasive modality for the diagnosis and therapeutic evaluation of ocular surface squamous neoplasia (OSSN). Here, the system setup, scanning technique, and representative diagnostic results are presented.

Anterior High-Resolution Optical Coherence Tomography in the Diagnosis and Therapeutic Monitoring of Ocular Surface Squamous Neoplasia

This paper presents the protocols and clinical validation data for using a smartphone app to subjectively measure refractive error.

Subjective Refraction Test Using a Smartphone for Vision Screening

The methodology explored visual and vestibular contributions to gaze stabilization during optokinetic and whole-body rotations. Stimulations were carried out through visual, vestibular, and visuovestibular trials. Torsional eye-movement gain and nystagmus frequencies served as indicators for the subcortical relay of sensory-specific motion information towards the reflexive brainstem response for each trial.

Using Eye-tracking to Assess the Relative Importance of Visual and Vestibular Input to Subcortical Motion Processing in the Roll Plane

The binocular wavefront optometer agrees well with traditional refraction techniques in both objective and subjective refraction measurements, offering superior accuracy and clinical utility. Its standardized protocol reduces optometrist workload and provides a more accurate refractive assessment for post-refractive surgery individuals.

Comparison of Agreement and Accuracy using Binocular Wavefront Optometer with Autorefractor and Phoropter

Learn to measure strabismus using an automated smartphone Hirschberg test app for clinical and research applications. This method enables accurate ocular alignment assessment with minimal training requirements.

Using an Automated Hirschberg Test App to Evaluate Ocular Alignment

Explore More Videos