VT Works

Real world changes in space and distance employ a SOLI response. That is to say, in real life, when objects get closer they become bigger, and conversely, when they travel further away, they become smaller. This premise seems to be at the basis of our visual logic in terms of how we “write” our spatial codes for maneuvering. Without thinking, we know if we see a car down the road and it appears to be getting bigger, it must be getting closer, and vice versa. It’s really a fascinating system.

With monocular lenses, although visual logic is employed, SILO becomes an available option to the patient. Remember, even with one eye covered, when we change accommodation vergence is still affected. So with a -6.00 lens, for instance, we stimulate accommodation to meet the demand of the lens and vergence is passively changed – meaning convergence occurs. The inverse applies for plus lenses and divergence. A key element to understanding all of this is remains in how lenses create a focal point, and we adjust our eyes to meet that focal point. Minus lenses create a focal point between our eyes and the target we are viewing thus giving the appearance of “smaller in”, and plus lenses create a focal point behind the target, which creates the appearance of “larger out”. Granted, this form of SILO can feel much harder to appreciate than the binocular version.

Level Two – Lens On Clear/Lens Off Clear

This activity comes by many different names, with the most common being “Monocular Accommodative Rock”. The entire emphasis of this level asks the patient to meet the accommodative demands of the lens. Key in all this is helping the patients understand it’s not the lenses which are making the change; rather, the lenses are causing a disruption, or conflict, which they, the patient, need to visually resolve.

With a similar setup to level one, the patient should be seated comfortable with an age appropriate text at Harmon’s distance. If you are able to offer them a slantboard or appropriately sloped surface, even better.

The activity involves asking the patient to place the lens in front of their unpatched eye, approximately in the same position as a pair of eyeglasses, while asking them to clear the image in front of them as quickly as possible. Once this is achieved, the lens should be removed, and again, the patient is asked to clear the image as quickly as possible.

As the Vision Therapist, our job (along with offering clear and concise directions), is to be observers. Does the lens we chose offer an appropriate demand to the patient? Is the patient able to achieve at this task with some effort but without feeling visually overwhelmed? Again, in the session preparation phase of our day prior to the patient’s arrival, we should have decided which power would be an appropriate place to begin, in terms of lens power. Some of this information can be gathered based on the success and/or struggles in level one, and any disparities can be discussed with the Developmental Optometrist. In our observations, we might be watching for pupil constriction, variable lags of accommodation (one eye seems to take longer to clear the image than the other eye), does the patient need to squint to achieve this task, is the eye under the patch converging or divering appropriately, or do they even feel the need to move closer than Harmon’s distance to make the target clear? While squinting and changing their working distance is never optimal – remember, moving closer induces more accommodative demand – we can offer them assistance simply by changing the target size, adding more light, or even backing down the lens power some to see if they are able to achieve at an optimal level.

Along with flexibility, stamina, and control, a key element in this level is the patient’s awareness of where they are looking – remember “where am I?” versus “where is it?” – and the associated feeling tone in achieving clarity with the given lens. The resultant outcome hopefully being a SILO response.

A few tips to keep in mind:

• Equality is important. Before the patient is ready to move on, they should be able to achieve relatively equally in both eyes
• Avoid the snapshot. I usually try to work this activity twice, in two separate sessions, just to avoid any false positives
• Patient Feedback – How do you feel about this?

Cheers!