Glossary
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Sagittal depth
A measurement of the height of a lens, in millimeters, from a flat surface to the highest point of its curvature.
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Saline solution
A sterile salt solution used in cleaning, rinsing, and sometimes storing of contact lenses
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Schirmer test
Schirmer's test determines whether the eye produces enough tears to keep it moist. This test is used when a person experiences very dry eyes or excessive watering of the eyes
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Sclera
The sclera is the white of the eye and forms the outer coating of the eyeball.
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Scleral lens
A scleral lens is a large type of contact lens that rests on the sclera and creates a tear-filled vault over the cornea.
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Serratia marcescens
A bacterial organism associated with infection in contact lens wearers. The organism has been found on lenses, in lens cases, and in lens care solutions that have been mishandled by patients.
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Silicone hydrogels
Highly permeable soft contact lens materials that allow more oxygen to reach the eye than conventional soft lens materials. Initially they were intended for long periods of uninterrupted use, including overnight wear, with minimal lens handling and cleaning. Today, these materials are most used for lenses that are worn on a daily basis and removed at night, and for daily disposable, single-use lenses too.
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Snellen chart
A standardized test chart introduced in 1862 by Dutch ophthalmologist Hermann Snellen to measure visual acuity. See visual acuity below.
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Soft contact lens
Made of gel-like plastic, soft contact lenses contain varying amounts of water. They provide good initial comfort for first-time wearers but must be replaced often.
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Solution
Product used to clean, disinfect, and store contact lenses.
