Council uncovers high failure rate in optical precision of lensesfor spectacles - CHOICE # 374

The perfect vision is unjustifiably denied to many a spectacle wearer - .because of the problem with the optical precision in the manufacture of the lenses.

This stunning revelation was brought to light in a survey of the Consumer Council on a total of 100 pairs of prescription eyeglasses purchased from optical shops.

Out of the 100 samples of progressive and myopia spectacles, more than half (54 pairs) were found to be fitted with lenses that failed to conform to the prescriptions.

The variances were in excess of the tolerance limit laid down in the standard - the specification for Tolerances on Prescription Ophthalmic Lenses prepared by the Hong Kong Optometric Association and the Hong Kong Society of Professional Optometrists.

Amongst the 54 pairs of lenses in question, a high 63% failure rate was detected in the progressive spectacles (34 pairs), while a lower rate of 37% in the myopia spectacles (20 pairs).

The samples were found to fail in one or more properties relating to the specification tolerance.

The biggest variances were 0.33 dioptre, or 0.21 dioptre beyond the tolerance limit, in spherical power (for correction of myopia), and 0.19 dioptre, or 0.07 dioptre in excess of the limit, in cylindrical power (for correction of astigmatism).

The optical industry maintains that the variances between the prescriptions and optical precision of the lenses are within the tolerable limits for the human eyes.

But the Consumer Council holds a different view: It is the responsibility of the optometrists of the optical shops to check and ensure that the eyeglasses dispensed to consumers are in conformity of the prescriptions.

Otherwise, they should return the lenses to the manufacturers for rectification.

The problem with some of the optical shops may be due to the lack of proper apparatus for them to measure the spectacle lenses with the needed degree of precision.

This is because the focimeters they use for measurement "usually take 0.12 dioptre or 0.25 dioptre as a single measurement unit", and therefore cannot detect variances as fine as those stipulated in the Specification.

As consumers generally cannot ascertain for themselves whether or not the spectacles are as originally prescribed, improvement in this area is obviously in urgent need for the industry to safeguard the interests of consumers in eye care.

In the same study, the Consumer Council sought also to survey the practices of the optical shops in having eye examination conducted by registered optometrists.

According to Section 18 of the Supplementary Medical Professions Ordinance, a person (as in the case of the optometry profession) registered shall keep displayed, in a conspicuous position, in any premises in which he practices his profession, his certificate of registration, or a certified copy of such certificate.

It was found that only in 58 cases of the 100 samples purchased were the certificates of registration of the optometrists who performed the eye examination seen clearly on display, in 5 cases the examiners simply presented themselves as registered optometrist by means of name tag or name card, and in the remaining 37 cases it was uncertain if the eye tester was in fact a registered optometrist or not.

Consumers are advised to always look for shops with registered optometrist or qualified professional to conduct eye examination for spectacle prescription. Only registered optometrists and persons exempted under the Optometrists (Registration and Disciplinary procedure) Regulation are allowed to conduct testing vision, prescribing and fitting optical appliances.