Dispensing: Prescription analysis – Case #6

This case was among a series presented by Miranda Richardson FBDO, Assistant Director of Professional Examinations for the Association of British Dispensing Opticians, for peer discussion at the second Specsavers Dispensing Conference (SDC2) in August 2018.

Case #6

Habitual Rx:

Right   Left
+1.25 +0.50 180 Distance +1.00 +0.75 180
 +3.25 -0.50 90 Near +3.00 -0.75 90 IN 

Prescriber’s comments:

  • Bifocals

Looking at the above prescription, consider the following discussion points with your dispensing team:

  • What is the reading addition?
  • Does any part of the prescription need to be transposed?
  • What is the age of the patient? How is this estimated?
  • What is the purpose of the prism?
  • The patient has prism at near only. Why?
  • Would you dispense all in one eye?


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  • The reading addition is not +2.00. It is R +1.50 L +1.25 – be aware of the Cyl form. Given this, why may different reading additions be prescribed?
  • The patient’s age is approximately 45/50, according to amplitude of accommodation.
  • The purpose of the prism is to correct the convergence insufficiency at near only.
  • Why would we split prism? When would prism not be split?
  • How could the prism at near only be dispensed in bifocal form?

Possible recommendations:

  • Prism can be split between the two eyes:
    • For cosmesis and to balance the spectacles
    • 2base in right and left
    • Prism may be left in one eye if there is a difference in the prescriptions; it does not have to be split evenly
  • Bifocals containing prism at near only:
    • Franklin split
    • Presto prism controlled bifocal
    • Decentred D-seg to induce base in at near – need to use a D35 or D45
  • Odd additions are rare, but some of the reasons why different reading additions may be prescribed include:
    • Anatomical dimensions
    • One cataract has been operated on and not the other
    • Pathological reasons


More in the Prescription Analysis series
Case #1 and series introduction
Case #2
Case #3
Case #4
Case #5
Case #6
Case #7
Case #8

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