The spectacle prescription – more than just numbers

In part 1 of her article series, ODA CEO April Petrusma says the prescription offers a wealth of information about the patient and their requirements, if decoded correctly by the optical dispenser.

Not every patient that visits the practice will have a typical, easy-to-correct prescription. As dispensers, it’s our role to dissect the prescription prescribed by the optometrist or ophthalmologist, with the aim of finding the best possible solution to meet our patient’s lifestyle and visual needs. It requires a lot more than taking a few measurements and sending an order form to the lab.

“When a patient presents with an outside prescription or the handover doesn’t run as smoothly as it should, our prescription interpretation super power comes into play.”

April Petrusma.

On first inspection, the dispenser should be looking deeper than the numbers. This is where it is our job to stop and consider what the numbers on the prescription are actually telling us. We should be looking to identify ocular conditions, pre-empting potential problems with the aim of minimising risk factors, visualising appropriate lens and frame recommendations and planning any measurements that will be required.

In a perfect world the dispenser would have access to patient consultation notes or have a smooth interactive handover with the optometrist but unfortunately this isn’t always the case. When a patient presents with an outside prescription or the handover doesn’t run as smoothly as it should, our prescription interpretation super power comes into play. The prescription offers an enormous amount of information if we look at them closely enough. Whilst it may not be spelt out in words but rather encrypted through the numbers on the piece of paper, our unique skill set means we have the ability to uncover the patient’s ocular conditions.

It’s imperative we do this, as with most ocular conditions comes a range of potential problems that dispensers have a level of control over if identified and treated correctly.

If you follow these six steps when interpreting your prescription, you have the best chance of meeting your patient’s expectations and will keep them coming back for years to come. As soon as you pick up the prescription you should STOP and THINK:

1. What does the Optical Cross look like?
2. What Ocular Conditions can you see?
3. What Potential Problems could they cause?
4. What will be the best Lens Recommendations accordingly?
5. What Frames should you recommend based on the selected lenses?
6. What Measurements will be required?

Once you put these general principles in place, you can apply the same rules to any prescription. Below is a simple example to act as a refresher for those more experienced or as a guide for those that are newer to the profession.

A case study

A skilled dispenser should always begin a dispense by visualising or drawing an optical cross. It shows the principal meridians of an astigmatic lens in the form of a simple diagram and helps us imagine what an astigmatic lens looks like through highlighting the principal powers. By starting here, we can easily note where any thickness will lie to aid in frame selection and can more easily identify the ocular conditions present to minimise potential problems and assist with lens recommendation.

Figure 1 demonstrates how the optical cross helps to identify the principal powers for each lens as well as the meridians in which they lie. This instantly starts guiding your thought process to recommendations but also allows you to easily identify the ocular conditions present.

In this case, we already know presbyopia is present due to the add in the prescription but the presence of plus (+) principal powers on both meridians in both lenses also tells us that the patient has a compound hyperopic astigmatism in both eyes. We can also identify high ametropia which is ascertained by the high refractive powers that are evident. (The textbook definition for this is a prescription of plus (+) or minus (-) 6.00 dioptres or higher).

The first step is complete and we have easily identified the ocular conditions but why is this so important and what impact does it have from a dispensing point of view?

Unfortunately, when dealing with certain prescription types, particularly those that fall into the atypical category, there are all sorts of considerations and potential problems to think about. For high ametropia (which is just one example), we must consider more than the obvious issues of lens thickness, weight and an unattractive cosmetic appearance. There is also a need to consider:

• Chromatic aberrations
• Surface reflections
• Spectacle magnification
• Field of view limitations
• Ring scotoma
• Back vertex distance compensation

Part 2 of this series will cover the considerations required by the dispenser for each of the potential problems mentioned and will discuss actions that can be taken to improve outcomes.

ABOUT THE AUTHOR: April Petrusma is the CEO of Optical Dispensers Australia and a Senior Lecturer at the Australasian College of Optical Dispensing. She is a qualified Optical Dispenser, RTO Trainer and Business Manager with a degree in Visual Communication.

This article originally appeared on Insight.

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