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Throughout my years of dispensing optical products as an optician/dispenser, I have developed techniques that enable me to build patients? confidence while saving time and money. These helpful hints have proven invaluable to me when I troubleshoot an optical challenge.
Throughout my years of dispensing optical products as an optician/dispenser, I have developed techniques that enable me to build patients' confidence while saving time and money. These helpful hints have proven invaluable to me when I troubleshoot an optical challenge.
Here are some of my most-used "how-tos" to help you develop the skills and intuition to know what needs to be done and how to do it.
Tip #1: Get the axis right the first time.
The solution: No matter what the cause, the solution is the same:
Place back in the lensometer, and voila! The sphere and cylinder lines should be clear and straight, placing the lens in correct alignment the first time, saving you time, and giving you a professional image in front of the patient.
Tip #2: Knowing when (and how) to take a single vision optical center height.
Occasionally, a patient will not adjust to a new design or new lens material, for example, shifting from CR-39 sphere base to a high-index aspheric design. Getting the best optical zone in front of the patient's visual axis is crucial in these cases. Single- vision lenses are typically blocked and aligned with the vertical optical center placement in the middle of the B frame dimension, the "datum line."
Problem is, most of us don't wear our frames with our eyes in the center. We usually choose a design where we are looking above the datum line, in the upper third of the eyewire. Even though some pantoscopic tilt is in place-in effect, raising the optical center-an additional measurement may be required. According to Martin's formula for lens tilt, for every 2° of pantoscopic tilt the optical center is raised 1 mm. This may place the best optical zone (the center of the lens) away from the patient's line of sight. The result is aberration and a general feeling of uncomfortable vision for the wearer.
Instead of writing off the non-adapt as a design or material issue, try this:
Problem solved, because you pre-adjusted the frame with the correct positioning of vertex distance, pantoscopic tilt, and face form. And, because you took the measurement with the eyewear plane to the face, it automatically takes care of the 2° of panto/1 mm optical center shift. That extra step in your fitting technique can make all of the difference.