Effect of Lens Presentation on the Clinical Oculomotor Assessment at Near

Study Overview
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Brief Summary
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This study will compare near clinical oculomotor parameters (heterophoria, vergence ranges, AC/A and accommodative findings) measured when lenses and/or prisms are introduced using three different instruments namely: (i) a standard manual phoropter, (ii) an electronic phoropter and (iii) a wearable adaptive refractor (VisionFit).

Detailed Description
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Previous studies have demonstrated differences in a number of near oculomotor parameters [e.g., heterophoria, accommodative convergence to accommodation (AC/A) ratio] when measured in a manual phoropter versus a trial frame. These differences may be due to variations in proximal vergence, differences in head and eye position and restriction of the peripheral visual field. Further, a number of standard clinical oculomotor procedures require the use of Risley rotary prisms. While prism is typically introduced in a smooth, ramp-like fashion with manual phoropters, step changes in prism are created with electronic phoropters. The precise effect of these variations on clinical measurements is unclear. Accordingly, after a routine refractive examination, a standard clinical near assessment (comprising near heterophoria, AC/A ratio, horizontal vergence ranges, amplitude of accommodation and negative and positive relative accommodation) will be carried out on the same individuals through: (i) a standard manual phoropter (American Optical model 11625), (ii) an electronic phoropter (Topcon CV-5000) and (iii) a wearable adaptive refractor (VisionFit). The latter resembles a trial frame mounted on a helmet carrier (similar to a binocular indirect ophthalmoscope headset) but includes adaptive lenses that can be changed electronically.

Official Title
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Effect of Lens Presentation on the Clinical Oculomotor Assessment at Near

Conditions
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Vision Disorders

Intervention / Treatment
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* Device: Phoropter


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Corrected visual acuity of at least 20/20 (logMAR = 0.0) or better in each eye Exclusion Criteria: Strabismus, amblyopia, manifest ocular disease.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 30 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Diagnostic
Intervention Model: Single Group Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Phoropter<br>Each subject will be tested on 3 separate occasions using either the manual phoropter (American Optical 11625), electronic phoropter (Topcon CV-5000) or the wearable adaptive refractor (VisionFit). | Device: Phoropter<br>* Each subject will be tested on 3 separate occasions using either the manual phoropter (American Optical 11625), electronic phoropter (Topcon CV-5000) or the wearable adaptive refractor (VisionFit). Oculomotor measurements, i.e., heterophoria, vergence ranges, AC/A and accommodative findings will be measured at each session using the different devices. Each session will be separated by a minimum of 24 hours and a maximum of 14 days.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Near horizontal heterophoria | Near horizontal heterophoria (measured in prism diopters) will be recorded using both the Von Graefe and Modified Thorington techniques using each of the three lens presentation devices. The single set of measurements will be recorded approximately 15 minutes after the start of the trial. | approximately 15 minutes | 
| Accommodative convergence to accommodation (AC/A) ratio | The AC/A ratio will be calculated from measurements of near horizontal heterophoria (quantified in prism diopters) will be recorded using the Modified Thorington technique at 3 different accommodative stimulus levels (1.5D, 2.5D and 3.5D). Measurements will be obtained using each of the three lens presentation devices and calculated in units of prism diopter per diopter accommodation.The single set of measurements will be recorded approximately 15 minutes after the start of the trial. | approximately 15 minutes | 
| Horizontal near vergence ranges | Near base-in and base-out vergence ranges will be measured (in prism diopters) while the subject fixates a near target. Measurements will be expressed in terms of the blur point, break point and recovery measurement .The single set of measurements will be recorded approximately 15 minutes after the start of the trial. | approximately 15 minutes | 
| Minus lens amplitude of accommodation | Minus lens amplitude of accommodation (measured in diopters) will be recorded using each of the three lens presentation devices.The single set of measurements will be recorded approximately 15 minutes after the start of the trial. | approximately 15 minutes | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Negative and Positive Relative Accommodation (NRA and PRA) | NRA and PRA (measured in diopters) will be recorded using each of the three lens presentation devices.The single set of measurements will be recorded approximately 15 minutes after the start of the trial. | approximately 15 minutes |