Specialists argue that the term "rigid lenses" should be ditched and replaced with a descriptor that better fits each unique lens type.
Specialists argue that the term "rigid lenses" should be ditched and replaced with a descriptor that better fits each unique lens type. Click image to enlarge.

The term “rigid contact lens,” coined in the 1980s when PMMA materials debuted, helped to distinguish these products from the earlier “hard” lenses made of glass, as PMMA allowed some flexure yet retained its shape. It was both accurate terminology and a helpful way to distinguish these lenses from products made with hydrogel materials, which had taken on the name “soft contact lenses.” Practitioners routinely called them RGPs, for rigid gas permeables.

However, despite their new moniker, RGPs were found to be initially uncomfortable and required a period of adaptation. To lessen patient anxiety, the word “rigid” was typically dropped and doctors opted to simply call the lenses “GPs” in deference to the need for high patient motivation at the outset. This change created confusion among eye care practitioners since both soft and rigid lenses are gas permeable from a technical perspective; subsequently, its usage can be inconsistent, ambiguous and confusing. 

So argues three eminent contact lens specialists in a recent editorial for Clinical and Experimental Optometry. Nathan Efron, Stephen Vincent and Richard Lindsay, all from Queensland University of Technology, suggest that it’s now time to “call a spade a spade” and bring back the use of rigid to describe lenses that don’t conform to the shape of the eye the way soft lenses do.

Many practitioners today also interchangeably use the terms corneal lens, hard lens, flexible lens, rigid lens, hard GP lens, rigid GP lens and GP lens. “Any discipline that uses [a lot of] terms to describe the same product is asking for trouble,” the authors wrote.

To help, the authors proposed using the general terms “rigid lens” and “rigid CL” when referring non-specifically to any form of a hard lens, depending on the context. For a rigid lens that only bears on the cornea, any of the terms “corneal lens,” “rigid corneal lens,” “corneal CL” and “rigid corneal CL” could be used, they added. Looking at the bigger picture, all lenses should be classified as either hybrid (rigid central optic section and a silicone hydrogel outer skirt), soft (hydrogel, silicone hydrogel or silicone) or rigid (corneal, corneoscleral or scleral), the investigators suggested.

“These are the terms we should all be using,” the group wrote. “If the international CL fraternity is willing to adopt the consistent, unambiguous terminology presented here, then the field of CLs can continue to move forward with a much greater level of clarity, to the benefit of students, clinicians, the CL industry and CL patients.”

Efron N, Vincent S, Lindsay RG. It’s time to call a spade a spade rigid contact lens nomenclature. Clin Exp Optom. January 5, 2022. [Epub ahead of print].