Larger Diameter RGP lens

Discussion in 'Optometry Archives' started by Pia, Feb 27, 2009.

  1. Pia

    Pia Guest

    Hi,


    I have used 9mm diameter Rigid Gas Permeable contact lens for over
    20 years with base curve of 7.8. Yesterday, a new optometrist tested
    my eyes and said the 9mm diameter is too small and prescribe me
    10mm. Isn't 10mm too big? She said my eyes is 9.5mm but she
    wants larger like 10mm for more comfortable fit. After researching
    in the net, I learnt that larger diameter can have poorer tear
    exchange.
    Now how do I know if the 10mm is optimal or poor for my tear
    exchange?

    Also she said my base curve is now 7.9. How do you calculate
    changes in base curve and increase in optical powers (like 0.1mm
    base curve increase corresponding to decrease in powers like
    -1.0 diopters? What's the formula?

    Thanks.

    Pia
     
    Pia, Feb 27, 2009
    #1
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  2. Pia

    Neil Brooks Guest


    One possible way: try it.
     
    Neil Brooks, Feb 28, 2009
    #2
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