Around 1980, SEIKO was engaged in exchanges with a doctor from the Ophthalmology Department of Shinshu University.
SEIKO had asked this doctor, who had only used bifocal lenses previously, to conduct monitoring of "P-1 Mild," a progressive lens that had won high acclaim at the time and, as a result, the doctor in question proclaimed, "I feel like I've returned to my youth!" and gave the product his unreserved approval.
Following this, the same doctor made the following enquiry: "I wonder if it would be possible to produce a lens that would make it easier to see my hands when I'm performing surgical procedures."
With this in mind, work began on development of a progressive lens for indoor use that would be ideal for performing indoor work such as surgical procedures.
One important consideration for a lens exclusively for indoor use is how wide a field of vision can be achieved from close distance to intermediate distance (approximately 5 m). To overcome this problem, SEIKO chose to adopt a method that used a 25 mm progressive corridor featuring continuous variations in power.
Since progressive lenses at that time generally incorporated a progressive power corridor of 16 mm, needless to say, a 25 mm corridor was a world first.
Realization of a 25 mm progressive power corridor reduced distortion and blurring and enabled commercialization of a lens with a wide field of vision from close to intermediate distances. Nowadays, this would be called a close to intermediate distance lens.
In June 1986, this lens made its world debut under the name "Senior 50," representing the birth of the world's first progressive lens (close to intermediate distance lens).
This lens was the first of its kind not only in Japan, but in the world, to make use of this concept.
From the time the product was launched commercially, the lens won high acclaim for its realization of reduced distortion and blurring and its comfortable fit. This is an historical product that created the subsequent market for progressive lenses for indoor use (close to intermediate distance lens).
SEIKO'S application-specific design concept of the ideal lens matched to various scenarios came into full bloom with the advent of this product.
At the present time, further improvements have been made, resulting in commercially-available products such as "Caster" and "Roomiest" , "Indoor LD" successors to "Senior 50."