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Summary SOFT CONTACT LENSES
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Complete notes on RGP lenses
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667Contact Lens Study notes (B)RGP Lens Types
Corneal diameter lenses (7-12mm)
Corneal – scleral (12.1 – 15mm)
Mini – scleral (15.1 – 18mm)
Scleral (>18mm)
Corneal RGP Fitting
Often regarded as more complex
Fitting= straightforward
Less margin for error if your preliminary measurements though as
require precise fitting
Advantages Disadvantages
Robust- Can be re-polished Physical comfort – need to build up
tolerance
Easy to clean – soaking solutions Greater movement of the lens-
stronger dislodging
Fewer Solution problems
Last longer FB entrapment
Easy to handle (no inside out, rigid)
Stable vision – avoid fit of toric
potential (tear lens)
Good O2 supply
Less dehydration
Customisation (high rx, tints etc etc)
Good tear Exchange
When to choose RGP
Moderate Corneal Astigmatism- avoid the wear of toric lens
High complex rx
History of allergies
Problems with soft contact lens (damage, deposits, solutions, SCL
induced papillary conjunctivitis)
, Financial reasons
Poor compliance with other lenses
High visual demands
When to avoid an RGP
Contact sports
Water sports
Dusty environments – increase in foreign bodies
*Main ones to focus on – BOZR, BOZD, TD*
The BOZD 1-1.5mm smaller than the total diameter (TD). Large enough
to cover pupil in different light conditions
FOZD 0.5mm larger than BOZD
Centre thickness- too thing a lens leads to flexure which can lead to a
breakage and residual astigmatism
Edge lift; to prevent mechanical pressure on the cornea allow tear
exchange and enable lens removal
, Tear Lens
Once picked a lens and looked at fit we are now looking at the rx
When an RGP fits, a small lens is formed between the RGP and the
cornea which is called the Tear lens.
Both combined give the total rx
If lens is flat = negative tear lens
If lens is steep = Positive tear lens
SPECIFICATION = BOZR / TD / BVP (same as soft CL)
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