contact lens practice pearls
Role of Ocular Dominance in Presbyopic Lens Correction
Does ocular dominance play a role in achieving success with presbyopic contact lens patients? Let's look at methods to assess dominance and why performing these tests is time well spent.
BY THOMAS G. QUINN, OD, MS, FAAO
Assessing Ocular Dominance
The most common method of assessing ocular dominance is referred to as the extended arms technique (Figure 1). Although there are minor variations of this approach, they all measure sighting dominance. You can think of sighting dominance as a measure of how one's system is "wired," much like being right- or left-handed.
Does Sighting Dominance Matter?
In a 1987 study, Shor et al found no relationship between sighting dominance and the ability to suppress blur (such as that introduced with monovision or multifocals with unequal adds). This supported numerous other studies that concluded dominance wasn't a significant factor in monovision success.
Robboy et al (1990) suggested that sighting dominance alone may not be an adequate measure of ocular dominance. They suggest sensory dominance may play an important role. This assertion is supported in work by Collins and Goode (1994) and more recently by Handa et al (2005) who found binocular summation was influenced by the strength of ocular dominance.
Assessing Sensory Dominance
You can measure sensory dominance by alternately placing plus lenses in front of each eye independently under binocular conditions and asking the patient to report when he experiences the greater visual disturbance.
Figure 1. The extended arms technique for assessing ocular dominance.
There are three ways to introduce the plus lenses. One option is to place the patient behind the phoropter with his best spectacle correction in the instrument. With both eyes viewing, begin to gradually introduce plus in front of one eye and ask the patient to report when he first notices blur. Note the phoropter reading. Repeat for the other eye. The eye that accepts the least plus is more disturbed by the blur and is therefore the dominant eye.
A second method utilizing the phoropter is to alternately rotate the +1.50D retinoscopy lens in front of each eye under binocular conditions. The eye the lens is in front of when the patient reports the greater disturbance in vision is the dominant eye.
I prefer to simply place a +2.00D trial spectacle lens in front of each eye alternately. The eye I have the lens in front of when the patient reports the greater visual blur is the dominant eye. An important caveat: both eyes must be optimally corrected for distance viewing before administering this technique. If you previously under-minused an incipient presbyope in one eye to get him by for awhile, you must correct this before proceeding with this method.
So Now What?
Assessing both sighting and sensory dominance may be the best approach. Robboy et al (1990) found that when both types of dominance occurred in the same eye, it was easier to suppress blur.
It only takes a few moments to perform each test and the information may serve as a stepping stone on our way to achieving success with presbyopic contact lens patients.
Dr. Quinn is in group practice in Athens, Ohio, is a diplomate of the Cornea and Contact Lens Section of the American Academy of Optometry and advisor to the GP Lens Institute.