We have had a great deal of success with patients in our practice using the multifocal and now, the accommodating Crystalens. We have tried to use the time-honored test of preoperatively screening and evaluating patients for their tolerance to different levels of monovision. Dr. Strauss developed the loose lens test, which we found quite helpful but being slightly distractible, I could never find the lenses I needed. They were not in my pocket as I thought they would be. We developed the blur tolerence tester to create an inexpensive, simple model to assist us in testing patients for distance, near blur tolerance and reading abilities with different amounts of monovision.

The Blur Tolerence Test and monovision tester was designed to be simple, inexpensive, portable and user friendly. This meant that we would have to have one handheld device that would be easily transportable, used by all the doctors and technicians and be a simple rote method to determine the success of this technology for our patients. Determining first which is the patient’s dominant eye does the test. This is done with a simple Eye Dominance Test available from Gulden Ophthalmics or by a variety of other methods. Once we have established the dominant eye, we place the rotating test of low add lenses in front of the non-dominant eye. With the occluder on the dominant eye open and the non-dominant eye open, we dial in the amount of add a patient needs, either 0.75, 1.00 or 1.25 to read Jaeger 2 somewhat comfortably. This establishes that the patient can see at near using both eyes with a modified monovision change in their no dominant eye. The key point here is that we can occlude the dominant eye and show the patient that they are really, truly seeing mostly with their non-dominant eye. This can be shown to them by reopening the occluded eye demonstrating that the distance eye really is not that bothersome at near. We evaluate the lowest amount of add a patient can possibly tolerate. We then ask the patient to look in the distance. Often they will switch to their dominant eye and not realize that they are blurred in front their non-dominant eye. We then occlude the dominant eye, which is Plano, and ask them how things seem. They then complain to us that they cannot see anything and it is very blurry. We explain to them that is what it would be like if they close their dominant eye in distance vision. With both eyes open and un-occluded, we asked how they tolerate that. They can walk around the office or observe things for a few minutes. If they tolerate the un-occluded bilateral modified monovision for distance and near, they are excellent candidates for CK or LASIK with slight degrees of monovision, which seems to function quite well.

There is a term called, “summation,” which has to do with the ability of the mind and the eyes working together to additively see things that with one eye alone, would be blurred. The use of summation allows us to use much lower levels of monovision correction than normally needed. We have had a great deal of success correcting patients with this method. The Siepser Blur Tolerence Test and Eye Dominance Test helps us to determine which patients will tolerate this and at what level of monovision will meet their needs.