When Seiichi Miyake found out a close friend was losing their ability to see clearly, he wanted to help. That desire led to an entirely new way for the visually impaired to navigate big cities, railways and parks. 

In 1965, Miyake invented the tactile paving slab (or "Tenji block" in Japan) with his own money. Monday's Google Doodle celebrates the first introduction of the block, 52 years ago.

The Tenji blocks were first introduced to the Japanese city of Okayama on March 18, 1967, next to a school for the blind, and would go on to revolutionize the way the visually impaired interact with the world, making it safer and easier to get around public spaces independently.

Miyake's original design, which was installed in all Japan Railway platforms in the 1970s and has rapidly found its way to cities across the globe, featured two tactile patterns that people with visual impairments can detect with a cane or through their feet -- providing cues on which way they should head.

One pattern features a series of raised lines that indicate "forward". The second design is commonly referred to as the "truncated domes" pattern, a series of small bumps that act as a "stop" sign -- typically at the edge of a train platform or before a motorway.

A number of different patterns have been designed since, with smaller raised dots or more pill-shaped bumps signifying different directional cues around the world. For instance, when the raised lines are horizontal in the direction of travel, that might mean "look out for steps ahead". 

All of those cues, which many may not even notice as they wander through a city, are incredibly important for those with limited vision.