Tvrda gas-propusna (RGP) kontaktna sočiva Koncepcija

Slide 19
Fluoresceinski model
Rigid Gas Permeable Contact Lenses Design
Fluorescein Pattern
The fluorescein pattern observed under an RGP lens depends on its back surface shape.
The diagrams, representing cross-sectional traces of tear lens thickness under rigid lenses,
show the expected patterns from two possibilities.
An aspheric shape ideally aligns with the cornea. As a result, little or no fluorescein is
seen anywhere except at the lens edge. The latter is due to the tear reservoir/meniscus
deliberately formed at the lens edge.
A spherical BOZD shows the effect of a spherical curve not aligning with the aspheric
cornea. The bull’s-eye appearance refers to the concentric bright band (ring of
fluorescence) surrounding the dark centre (absence of fluorescence) which results. This
effect is much less pronounced with a small BOZD) even when the BOZR is altered to
compensate for the change in sagittal height.
Fluoresceinski model
Floresceinski model koji se vidi ispod RGP sočiva zavisi od oblika zadnje površine.
Dijagrami predstavljaju poprečne preseke debljine šupljina ispod tvrdog sočiva
pokazujući dve mogućnosti.
Asferični oblik idealno naleže na korneu. Kao rezultat, malo ili upšte se nevidi
fluorescein, osim na ivici. Na ivicama se vidi zbog suza/meniskusa koji se formira na
ivici sočiva.
Sferični BOZD pokazuje efekat da sferna krivina ne naleže potpuno na asfernu korneu.
Pojava oka bika se ogleda u koncentričnim trakama (prsten fluoresceina) koji opkoljava
tamni centar (odsustvo fluoresceina). Ovaj efekat je manje primetan za mali BOZD.