Progressive Lenses

Advanced & Innovative Progressive Lenses Fittings in Williston VT for the Clearest Vision

Dr. Clark offers specialized care for patients needing progressive lenses (aka blended bifocals).

Approximately 10 percent of people who need a reading prescription are unable to use progressive bifocal lenses.

Approximately another 40 percent are never quite happy with their progressive bifocals but have to tolerate them because their visual needs require this style of bifocal.

The main cause for patients rejecting and having discomfort with progressive bifocals is because the placement of the bifocal reading area is not placed correctly in that individual’s frame.

For success: the bifocals of both lenses have to be placed so that the patient’s visual axes pass through the center of the reading areas of these bifocals.

It’s that simple!

The problem:

The optical industry (optometrists and opticians) have used external measurements to determine where to place the bifocal reading areas within an eyeglass frame. These measurements have been used for 100 years because the industry has mistakenly assumed that the physical measurement — or corneal pupillary measurement — and the visual axis measurement were the same. This assumption is incorrect.

This error of judgment was not a problem with older style of bifocal lenses, flat tops etc. The new style progressive bifocals need to have very accurate measurements and placement to succeed and be comfortable.

In almost all individuals, there is a difference between the physical measurement or pupillary reflex measurement and the visual axis measurement. The difference ranges from 1mm to 5mm of displacement error. As the displacement error of the progressive lenses increases, the chance for intolerance with these progressive lenses increases.

The solution:

Measure the actual visual axis of every individual that needs progressive bifocal lenses.

It’s that simple!

Dr. Clark has developed and patented a measuring device that easily and accurately measures the visual axes in each individual’s eye. Using this new technique, our office is having great success creating happier progressive lens wearers using this visual axis measurement information.

Related Articles

Read an article from the Williston Observer about Dr. Clark’s patent.

Measure visual, not pupillary, axis for accurate PAL placement, Optometry Times, November December 2011


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Williston Office


8:00 am-5:00 pm


8:00 am-5:00 pm


8:00 am-5:00 pm


8:00 am-5:00 pm


8:00 am-5:00 pm






Reviews From Our Satisfied Patients

  • ""Being new to Vermont, I wasn't sure which optometry practice was best for me. I landed at the office of Thomas H. Clark OD after a terrible experience at another optometry office nearby. Dr. Clark and his team have proven to be just what I was looking for. Dr. Clark is an excellent eye doctor and his team provides exemplary service. They offer a good selection of products and their lab turns out excellent high quality lenses that offer the clearest vision correction I have ever had in glasses. Their knowledge, ability, care and professionalism is superior to others that I have found. If you seek vision correction that is spot on, and you value high quality patient care, I recommend a visit to this office in Williston, VT.""