Clinical & experimental optometry · 2009
A review of the limitations of the first hydrogel contact lenses.
Историческая статьяСтатьяОбзорНазвание и аннотация: Перевод пока не подготовлен
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Pearson Richard M
Аннотация
BACKGROUND: It is generally believed that the clinical performance of the original Czechoslovakian hydrogel contact lenses was poor but historical reviews provide very little explanation regarding their failings. There is a lack of information in the literature about their dimensions and, in particular, thickness, which is essential for the calculation of oxygen transmissibility. Until now no measurements on Czechoslovakian lenses have been reported.
METHODS: A literature search on Czechoslovakian lenses was made that spanned the first decade of their use and included peer-reviewed journals, non-refereed publications and a number of archived documents. In addition, the water content and dimensions of five Geltakt and four Spofa lenses were measured.
RESULTS: Lens packaging, lens lifetime, hygienic care, visual acuity, nominal lens dimensions, flexure, failure to correct astigmatism, corneal oedema, oxygen transmissibility, complications and wearing time are reviewed. Measurements on Czechoslovakian lenses indicate that the total diameter was similar to that of the cornea, the back optic zone radius was steep and the centre thickness was large.
CONCLUSION: Problems associated with the Czechoslovakian lenses included packaging and an initial failure to require daily disinfection. Few complications of lens wear were reported, probably due to the comparatively small number of patients fitted and the limited wearing time that they achieved. Delayed disclosure of lens dimensions handicapped the development of a fitting technique. An acceptable visual acuity was attained in selected cases, while reduced acuity may sometimes have been due to uncorrected astigmatism or to poor lens quality. The most serious disadvantage was the very low oxygen transmissibility that could result in marked corneal oedema.
METHODS: A literature search on Czechoslovakian lenses was made that spanned the first decade of their use and included peer-reviewed journals, non-refereed publications and a number of archived documents. In addition, the water content and dimensions of five Geltakt and four Spofa lenses were measured.
RESULTS: Lens packaging, lens lifetime, hygienic care, visual acuity, nominal lens dimensions, flexure, failure to correct astigmatism, corneal oedema, oxygen transmissibility, complications and wearing time are reviewed. Measurements on Czechoslovakian lenses indicate that the total diameter was similar to that of the cornea, the back optic zone radius was steep and the centre thickness was large.
CONCLUSION: Problems associated with the Czechoslovakian lenses included packaging and an initial failure to require daily disinfection. Few complications of lens wear were reported, probably due to the comparatively small number of patients fitted and the limited wearing time that they achieved. Delayed disclosure of lens dimensions handicapped the development of a fitting technique. An acceptable visual acuity was attained in selected cases, while reduced acuity may sometimes have been due to uncorrected astigmatism or to poor lens quality. The most serious disadvantage was the very low oxygen transmissibility that could result in marked corneal oedema.