Assessing ocular dominance remains a useful piece of the pre-fitting evaluation. In fact, it can help with both monovision and multifocal-prescribing. Here, I discuss the 2 ocular dominance tests, and show how employing them can aid in fitting presbyopes.
The Tests
To review, sighting dominance is when one eye is preferred as the “lead eye” when focusing on a specific point (ie, aiming at a target), while sensory dominance refers to one eye taking the lead in providing information to the brain when both eyes are viewing the same image.
1. Sighting. The determination of the dominant eye is dependent on the test used and gaze angle. The most common method reported in the literature is the “hole-in-card” test. This test determines the ocular preference (sighting eye dominance) by using the hands. That said, sighting dominance alone is not an adequate measure of ocular dominance.1
2. Sensory. The sensory test (“resistance to blur”) allows for the determination of “strength” of ocular dominance. This principle is most reliable when both eyes are correctable to the same level of acuity. Specifically, it is based on the assumption that it is easier to suppress blur in the non-dominant eye vs. the dominant eye. To per-form this method, one alternatively introduces +1.00 D over each eye in a binocular setting with best distance correction in place.
Employing Both
By using both tests, the OD is able to confirm results, especially if the patient’s eyes are not equally correctable. Also, the sensory test can easily be conducted at near to determine the patient’s “preferred” eye for near visual processing. This is useful in cases in which patients exhibit “alternating” ocular dominance depending on the visual task and testing distance.
When fitting monovision contact lenses, I find that aiming for the least disparity in correction between the eyes leads to faster adaptation and visual performance. This is achieved by prescribing the most plus to best distance vision and least plus to best near vision. It’s important to evaluate the patient’s visual comfort under binocular conditions in normal room illumination. Further, optometrists should keep in mind that with some patients, the dominant eye is preferred for near vision and, thus, may be a better fitting strategy when prescribing for patients whose near demands are more critical or important to their daily activities.
Monovision can be considered for part-time social wearers who do not require excellent stereopsis or optimal reading speed.
While most multifocal lenses should be fit with equal distance and near correction in both eyes, some optical designs are based on a “hybrid” approach. Therefore, I find better outcomes when achieving full best-corrected visual acuity in the dominant eye and no less than a 2-line reduction of corrected distance visual acuity in the non-dominant eye.
A “modified monovision” approach is also often very helpful when fitting multifocal rigid gas permeable lenses. For example, when fitting either simultaneous vision and/or translating designs, adding +0.50 D to the distance correction of the non-dominant eye augments the range of comfortable intermediate vision.
Even with the current emphasis on maintaining binocularity and fitting more multifocal lenses, identifying the “dominant eye” remains useful. Strategies surrounding ocular dominance are key to optimizing satisfaction. OM
Reference
1. Robboy MW, Cox IG, Erickson P. Effects of sighting and sensory dominance on monovision high and low contrast visual acuity. CLAO J. 1990;16(4):299-301.
