Glossary
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Handling tint
Lenses that say "handling tint" are slightly tinted to make them more visible for both care and insertion of the lens. The tint on these lenses has no effect on eye color.
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Hard contact lens
Made of an inflexible plastic material called PMMA (polymethylmethacrylate), this was the first contact lens in wide use. Hard lenses had excellent optics, but because they kept oxygen from reaching the cornea, they've become virtually obsolete.
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Hard gas-permeables
A contact lens made of rigid plastic that transmits oxygen to the cornea.
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Hard lens
Contact lens made from a material which is stiff and rigid; lens will flex only a small amount, and will break if excessive force is applied.
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Hema
Abbreviation for hydroxyethyl methacrylate, a hydrophilic material containing 38% water commonly used in the manufacture of soft contact lenses.
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High-index lens
A High-Index lens is a type of lens with a higher index of refraction. This means that unlike traditional glass or plastic, light can travel faster through the lens to reach the eye.
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Hybrid multifocal lens
A multifocal contact lens that is soft around the peripheral with a gas permeable center.
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Hydrogel
Type of plastic material which contains water, and is commonly used in the manufacture of soft contact lenses
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Hydroxyethyl methacrylate (HEMA)
The first soft lens material; composed of monomers of hydroxyethyl methacrylate which form crosslinked chains; 38% water content, non-ionic polymer.
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Hypercapnia
The presence of a raised carbon dioxide content within ocular tissues. Contact lens wear tends to give rise to this condition, especially lenses of low gas transmissibility
