Optical Appliances Competency 4.9

Competency 4.9

The ability to manage non-tolerance cases

If a non-tolerance case occurs, practitioners must be able to logically identify the problem quickly and efficiently.  This competency assesses the trainee’s ability to listen to the patient and to solve the problem.

Non-tolerance cases can occur for many reasons.  They could be generally categorised as,

  • Pathological
  • Refractive
  • Dispensing

Pathological non-tolerance cases may exist if the effect of an ocular condition has not been fully appreciated.

For example, nuclear sclerosis of the lens.

  • Initially the visual acuity was 6/18 and following refraction corrected to 6/9.
  • As the patient expected to see 6/5 in perfect clarity through the new spectacles, and although he has a slightly sharper image, he is more aware of glare and complains that the spectacles are ‘not right.’
  • Generally, these forms of non-tolerance are mismanagement of expectation.

Refractive non-tolerances are just as described, where the new prescription issued is incorrect. Patients may complain of blurred vision and asthenopic symptoms, finding that their distance vision is “better through my old glasses”, or “have to read very close… no one reads this close!” Patients who have been over-minus’d may complain of ‘straining’ or ‘pulling’ of the eyes as accommodation is stimulated to try and create a sharp image.  It is also very common for trainees and newly qualified optometrists to over plus a patient as they try to ‘push the plus’ in the distance refraction.  This is compounded by an over reliance on the  +1.00 blur test; some patients may simply remember the letter chart whereas others who have miotic pupils (which reduce the size of the blur circle) may perform better than expected.

Dispensing non-tolerances may be caused by an error or non-tolerance to the lens form, design or fitting.  Generally this is more common with multifocal lenses due to the increased number of parameters in the lens design, although non-tolerance to single vision lenses does occur.

The best approach to non-tolerance cases is to treat the situation as an examination, with,

  • History and symptoms,
  • Examinations and checks targeted at those points
  • Finished by conclusions and advice to the patient

There is a general rule that the history and symptoms should give you an 80% idea of the diagnosis.  This rule applies to non-tolerances too.

Best Form Evidence

You should be ale to present a non –tolerance Patient Record card to the Assessor; at least one, but three where possible.  In this case, admitting more mistakes on your part will actually count in your favour here as you will have more to discuss and therefore have more evidence for the Assessor to sign off!

The record card should be laid out clearly showing the patient’s chief complaint, the tests carried out to investigate the complaint, and any advice or alterations made to solve the non-tolerance.

Role Play / Case Scenarios may also be used with the examiner perhaps playing the role of the patient, listening to your problem solving technique, and Questioning you on which aspects you are focussing on and why.

Unacceptable Evidence

Providing no advice or solutions to a problem would be a cause for failure.  If a case occurred which was pathological in origin, and refraction and dispensing non-tolerances had been eliminated, the Assessor will still expect to see that further counselling had been given to the patient regarding the pathology and any alternative management options given, including referral.

Example Case of Non Tolerance

Date: 0X/0X/0X

Px  c/o DV still blurry with new Rx.   Also notices glare more, especially at night.

Px aware VA better with new Rx than old.

Previous Rx


Distance Acuity

Near Add

Near Acuity



-2.00 / -0.50 x 80


Add +2.50

N5 slow



-1.75 DS


N5 slow

Spectacles: S/V distance OC’s accurate with optimal tilt and bow

Ophthalmoscopy:  clean + clear

External Examination: clean + clear

Media: Nuclear sclerosis cataract R Grade 3, L Grade 2

1. Px advised VA↑ with new Rx. No further↑ poss. due to nuclear sclerosis, lens opacities cause of glare

3. Px advised referral for surgery possible if wishes –discussed risks and benefits

4. Px happy – 6/12 recall – code 2.0 – surgery declined

Areas of further study

Study should be aimed at knowing the causes of non-tolerance and how a patient would be present.

Dispensing knowledge should be slightly greater due to the number of variables in spectacles. Understand the fundamentals of lens design for both single vision and multifocal lenses.  Knowledge of lens forms and how these may cause non-tolerances should be known e.g. V-values, base curves. Consider why some frames need an “8 base” lens compared to a standard 6 base, which frames these are and the consequences of glazing with the wrong base lens.

Understand the specific measurements needed for fitting multifocal lenses, the fitting positions of the lenses and makings found on the lenses.  Appreciate the different design of progressive lenses and how these can be used to produce a wider field of vision for certain tasks.  Certain patient groups will be better suited to standard corridor progressive lenses than the short corridor lenses.  Correct lens choice will greatly reduce the number of non-tolerance cases.

As progressive powered lenses rely on accurate fitting to ensure best optical and visual performance, there are many causes for non-tolerance.  Consider the solutions for progressive powered lenses if the complaint is:

  • Patient lifts their head or spectacles to read clearly
  • Patient lowers head to see distance vision clearly
  • Patient complains of wavy and blurry peripheral vision
  • Patient complains of a narrow reading area
  • Patient tells how holding the reading book to one side makes it more in focus

Consider the correct positioning of lenses in the frame and how the frame should be set to produce the best optical performance for example, frame position, frontal bow, decentration of lens centres when needed.  With high-powered lenses, it is important to check vertex distances of the frame compared to the testing distance and ensure that any vertex power adjustments have been made.


  1. Tutti Frutti says:

    Excellent! Cheers Peter.

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