Dispensing case study: Heights matter beyond the multifocal

By Max Drennan FBDO, Specsavers Tauranga, NZ


A 9-year-old male attended the clinic with his parents. He was wearing a set of Lenticular lenses in a pair of spectacles made in Korea, their home country. The frame and lens selection looked good. The reason for his visit was for a follow-up check.

Habitual Rx:
R: +13.50 / -0.75 X 30
L: +13.00DS

New prescribed Rx:
R: +12.75 / -0.75 X 32
L: +13.00 / -0.25 X 125

New spectacles were recommended as the over-correction in the right eye was holding back the visual acuity. The patient’s parents were keen to take the Rx so that they could fulfil it the next time they went home to Korea.

When making an adjustment to the frame, it was noted that the patient had an odd posture, with his head held up well beyond what would be considered normal. This posture was most noted at the neck but did start at the base of the spine. When the patient was asked if this was causing any discomfort, he responded that he was in pain almost all the time. When asked why he took on this posture, he replied, “So I can see.”

This information and his response came as a shock to the parents as he had never mentioned his pain / discomfort before. Upon checking the original spectacles, it was discovered no heights had been allowed for. This oversight was producing around 12 D of base down prism in both eyes. To neutralise this, the patient was placing himself in a head-up position to look through the optical centre of the lens.

Unfortunately, the parents opted not to order new glasses, however if a dispensing solution were to be provided, factors to be taken into account would include adjusted PDs to allow for the patient’s growth, and correct heights with a frame of the same depth as the 42mm ‘bowl’ to help reduce vertical edge thickness. It is important to remember with any measurements that they must be done on a fitted frame. Also, due to the nature of the script, BVD and its effect on the script would need to be allowed for and adjusted as needed.

Learning outcomes

In everyday practice life, we look at taking heights for bifocals, occupations, progressives, etc. If the heights prescribed are inaccurate, the patient will call back with “I cannot read as I should” or similar.

Heights in single vision prescriptions can often be overlooked, and the negative impact of not taking them can result in the patient needing to compensate for poor dispensing practice. These errors are thought of “as normal” but are, in fact, preventable with some time and care.

Taking care in all aspects of the dispense, including frame selection and use of the VDTM, is vital to ensuring a positive outcome for the patient. A poor fitting can undermine all of these steps and best practice, so it is important to take your time to do it once and do it well.

If the script is sensitive to fit, the patient should be reminded that a refit can be arranged free of charge at any Specsavers store for the life of the spectacles.

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