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Effect of Vergence Facility Testing on Horizontal Fusional Reserves
Farshad Askarizadeh1, Mohsen Heirani2, Masoud Khorrami-Nejad2
1Department of Optometry, Faculty of Rehabilitation Sciences, Tabriz University of Medical Sciences, Tabriz, Iran.
Summary
Vergence adaptation can affect fusional reserve measurements. Negative fusional reserves decreased after specific vergence facility testing, suggesting careful test sequencing in clinical practice.
Area of Science:
- Ophthalmology and Vision Science
- Clinical Optometry
- Binocular Vision Research
Background:
- Vergence adaptation is a neurophysiological response influencing binocular vision.
- Understanding its impact on clinical measurements is crucial for accurate assessment.
Purpose of the Study:
- To compare the effects of different vergence facility (VF) testing methods on subsequent horizontal fusional reserve measurements at near.
- To assess the clinical significance of vergence adaptation in vision testing sequences.
Main Methods:
- A cross-sectional study involving 50 healthy young adults.
- Baseline horizontal fusional reserves were measured using prisms.
- Vergence facility was then tested using two different flip prism methods (3∆BI/12∆BO and 8∆BI/8∆BO).
- Fusional reserves were re-measured after VF testing to evaluate adaptation effects.
Main Results:
- Negative fusional reserves significantly decreased after VF testing with 3∆BI/12∆BO prisms (p=.03).
- No significant changes in fusional reserves were observed after VF testing with 8∆BI/8∆BO prisms (p>.05).
- A positive correlation was found between pre- and post-VF fusional reserve values, regardless of the method used.
Conclusions:
- Vergence adaptation can alter negative fusional reserve measurements, particularly with the 3∆BI/12∆BO method.
- While adaptation may not be clinically significant, it is advisable to measure horizontal fusional reserves before VF testing or allow sufficient recovery time.
