August 18, 2021 | Student | Optometry | Pre-reg

Independent Optometrist Jason Searle shares his Top 10 Tips for prescribing glasses – excellent advice if you’re a pre-reg optometrist, newly-qualified optometrist or training to become an independent prescribing optometrist.

University and pre-registration clinics are where we understand that what we find subjectively may not be what we prescribe to our patients. Many supervisors taught me different ways of working and how to make sure what we find on the day gets converted into glasses that not only allow our patients to see clearly, but to minimise any adaptation problems that they may have. Over the years of working multiple optometry jobs I have really come to the conclusion that optical prescribing really is 50% science and 50% art.

A non-tol or a recheck can really hit an optometrist’s confidence, especially if you are newly qualified – as you may doubt your skills, be concerned that you have dented your patients’ confidence in you and nervous that your practice will be disappointed that chair-time is used up sorting out the non-tol and the cost of any remake that may arise. They still happen to me on occasion, and it is something I still take personally – but I have found that these tips really do help minimise those occasions!

Top Tips for Prescribing Glasses (Quick navigation)

  1. Demonstrate the Change when prescribing
  2. Demonstrate Further when prescribing
  3. Why Change Things?
  4. Little by Little
  5. Less with Age
  1. Advise Advise Advise
  2. Plus Be Gentle
  3. Don’t Get Silly With Cyls
  4. Distance Specific Changes
  5. Think Before You Ink

1) Demonstrate the Change when prescribing

This is simple to do and ought to be done every time you look to change someone’s prescription. If you are able to, hold up trial lenses that demonstrate the change over your patient’s current glasses. Granted that approve – this demonstration will help add to your recommendation to update their glasses. If they don’t notice a difference (and there are no other reasons to prescribe, then don’t push the update!) I also document this result on the record.

2) Demonstrate Further when prescribing

As you are aware the Snellen chart is not a good representation of real life, as the world is much more than black letters on a white background. Use a trial frame and show them the change outside the testing room. Let them look at a sign at the other end of the street or number plates in the car park with the new prescription and their current glasses and see if they appreciate the improvement. This can help if there appears to be little improvement in VA but noticing a change in prescription, aiding your decision as to whether to prescribe or not.

3) Why Change Things?

There is an old saying that goes “If it ain’t broke then don’t fix it”. If the patient is happy with their vision and they are able to do what they want to do (as well as meeting any relevant visual standards) in their current glasses, why should we change it? If you leave things as they are then they cannot be intolerant of the prescription should they buy a new pair (it will help then to identify a dispensing-related issue).

Yes, there is a commercial aspect to our roles and most of the patients buying new glasses are due to changes in their prescription, but finding “no change” or a stable prescription doesn’t mean they won’t convert! Discuss spare pairs, a new frame, sunglasses, different styles, lens upgrades – you’ll be surprised on how many people will be after a new frame or want some sunglasses or accessories. So don’t change things to try and win a conversion!

4) Little by Little

Following on from the rule above, you may find a large change in prescription that will benefit the patient meaning a change in prescription is required. For this, I will say a big change is anything over 0.50 dioptres and, although presently symptomless the lack of update may prompt difficulties to develop in the near future. You can change the prescription here, but don’t prescribe the full change immediately, opt to give 50-75% of the difference. This should help correct the refractive error, improve vision, but not be so different that the patient cannot adapt to it.

5) Less with Age

Be conservative with the changes made to prescriptions in older patients. Numerous studies show that older patients tolerate changes to spectacle prescriptions much less than younger patients. They are also more prone to falls, which a large change in prescription can cause. The last thing you want on your conscience is that a patient has suffered a fall due to your new optical prescription.

There becomes an issue with this rule that I encounter frequently. Older patients tend to have large refractive changes due to presbyopia (and inability to tolerate uncorrected latent hyperopia) and myopic shifts due to nuclear sclerotic cataracts. These shifts can cause large changes in refraction in short periods of time. Large changes may improve their acuity but cause anisometropic diplopia or balancing issues. Changing little but often means that the patient may require frequent spectacle updates, which will be a financial concern for the patient experiencing these frequent changes. Careful discussion with your patients and discussions with the practice manager/owner on managing these cases ethically and commercially may aid in this area.

6) Advise Advise Advise

Advising the patient of what we are doing should come naturally – after all we advise about eye health, vision and a whole host of other optometry-related topics each day. If I modify a prescription, I inform my patient and also write it on the prescription. This will help anyone who is rechecking the prescription what has been done and aid in rectifying it if problems arise.

If changes are likely to cause some initial visual discomfort (change in cylinder axis or any large change that is deemed necessary), advising the patient at the time of handing over the prescription and advising the dispensing optician what you have done will help them know what to expect when collecting their new glasses. I personally advise that any new pair of glasses can be a bit like a new pair of shoes and they can take a few days for your body to make them comfortable, which often works a charm. Just remember to document your advice!

7) Plus Be Gentle

I remember hearing “push the plus” at every refraction clinic during my university years and, whilst pushing the plus has good reason behind it, not prescribing to the needs of your patient may lead you in to a non-tol when your patients cannot see so well in the distance.  Young hyperopes have a lot of accommodation to consider and some of these hyperopes like to correct themselves by accommodating! Prescribing enough to help settle their symptoms (if they have any) will benefit them greatly, whilst partially correcting the plus will allow it easier for them to adapt to the spectacles.

8) Don’t Get Silly With Cyls

This is one gem that will have been taught to you at university and, with my -4.75 DC prescription, I can confirm that cylinders should not be messed with unnecessarily. Changes in cylindrical correction can cause big issues in tolerance to new glasses, with both power changes and axis changes having a significant impact on the final tolerance of the new prescription. A good rule of thumb is to split the difference between the patient’s current spectacle prescription and the subjective findings – the smaller change allows for better adaptation whilst improving vision. Just remember to advise your patient about what you are doing!

A word of caution to this however, make sure you remember the 2 for 1 rule if changing the cylindrical power (i.e. for every 0.50 DC adjustment of power, adjust the spherical power of your prescription by 0.25 in the other direction to ensure that the focus remains on the retina!)

9) Distance Specific Changes

Remember Rule 3 of “Why Change Things”? This rule is also distance specific. For example, if a patient says that their distance vision is worse but their near vision is fine, then generally you don’t need to change the prescription for near (unless they appreciate an improvement!).  Just be wary that your new distance prescription (a change of say -0.50 DS in each eye) doesn’t reduce their near performance if keeping the reading addition the same. Be sure to factor in the change to keep the relevant distances at their required focus.

10) Think Before You Ink

I feel I may be cheating you out of a rule with this one, but the most important rule is this one. Think before you ink – remember that whatever numbers and symbols you put down in the prescription boxes is what is going to be made in to the spectacles your patient is going to wear. Run through your recommendation based on what you have found, the patient’s symptoms, their visual status and the rules above to work out what you need to prescribe to give a clear, comfortable prescription that will satisfy the needs of your patient.

Remember also to document other prescription-relevant information (back vertex distance, if you’ve modified the prescription or highlight if one eye is plus and the other is minus etc.) on the prescription and records. Providing as much relevant information will help make sure the glasses are made to your instruction and will provide less scope for any errors to arise.

Bonus Tip! – Uncertain on Results? Don’t Hesitate to Recheck Before Prescribing glasses

If you are ever unsure on a prescription, don’t hesitate to hold off prescribing glasses and recheck on another occasion. A large or unusual change in refraction can throw you and may be a sign of something not quite right (poorly controlled diabetes, a patient who is poor at subjective refraction or someone who seems distracted can all do this, as well as macular pathology such as cystoid macular oedema or central serous chorioretinopathy).  Don’t be afraid to hold off prescribing until further investigations have been conducted and/or a recheck on another day has been completed. It is usually better to measure twice and cut once than it is to have an unhappy patient with glasses they can’t see through (or even worse, missed pathology!)

Bonus Tip 2! Retinoscopy Rules!

I use my retinoscope on every patient (even if it is over their existing prescription). Sometimes this can save you time as it can let you know if there are any significant changes in prescription and can help give confidence on your patient’s subjective results (especially if they seem to be going off on a tangent!). The added benefit is that you can see if there are any lenticular opacities that may affect the final result (of which may subsequently be discussed as a reason why the prescription has changed or acuity being less than expected).

This concludes the 10 golden rules (and the 2 bonus tips!) that I use when prescribing. What rules do you stick by? If you have any you would like to add, then feel free to give us an email [email protected].


If you are currently looking for a new role in optometry make sure to check out our latest vacancies. Whether you are an expert at the art of prescribing glasses or want to gain more valuable experience, we can help you find a role that suits your needs. If you are a pre-reg or student optometrist looking for useful resources and advice check out our Instagram page. For any more enquiries give us a call on 01423813452 or email us at [email protected]

August 18, 2021 | Student | Optometry | Pre-reg