They will then evaluate the fluorescein pattern and perform an over-refraction
. The trial lens can then be changed based on the results until the best fit is achieved at which time the lens can be ordered.
If VA is poor during over-refraction
, check the lenses are in good condition, and check VA with spectacles to see whether the problem is lens or eye related.
Specifically, the day aided my knowledge of the link between overall fit, fluorescein pattern, visual acuity and over-refraction
* The patient's subjective response to questions about vision and comfort in their current lenses can provide an indication as to if a pre-reg in expecting a significant over-refraction
or dry ryes
The means it is even more important to be aware of the relationship between the lens power, tear lens and over-refraction
 Assuming the patient in Image A has been fitted with the correct lens power, what over-refraction
would you expect, considering the fluorescein pattern observed?
The power along the flattest meridian is obtained by an over-refraction
. The power of the cylinder is obtained by calculation, taking into account the residual astigmatism from the spherical lens along with the induced astigmatism created by the toric back surface.
is a possibility, although not everyone's technique of choice.
After checking the patient's visual acuity and over-refraction
, you'll move on to the slit lamp.
You must take a relevant history and symptoms, perform an over-refraction
, assess the lens fit, carry out an anterior eye slit lamp examination, including tear assessment, and finally, advise the patient on your findings, along with an appropriate recall date--again, all recorded on the College recording sheet.
This means it is even more important for you to be aware of the relationship between the lens power, tear lens and over-refraction
will not be necessary after correction for back vertex distance