Veljanovska, Marija and Kosturanova, Marija and Stojanovska, Zdenka (2013) Ophthalmic lenses-necessity of standardization in Republic of Macedonia. In: Third Conference on Medical Physics and Biomedical Engineering, 18-19 Oct 2013, Skopje, Macedonia.
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Abstract
Most of the people in RM purchase their glasses over the counter (OTC) readers which are not
made by prescription and custom made parameters: sphere power for each eye, cylinder, axis and
monocular PD (distance between pupils). Unfortunately, the cheap price and uninformed patient are the
main reasons for using these non-prescribed and mass-produced glasses, with poor quality and one size
fits all. Practically prescription glasses have to design for any user individually. In order to cover all
refractive corrections correctly, the optical center of each lens mast be aligned with the center of each of
eyes' pupils.
In this research 14 pairs of OTC glasses were observed. They were investigated for two parameters:
prescribed lens power which is for mostly non-symmetric for both eyes with the power of wearing OTC
glasses; as well for PD of patients and optical centre of the glasses lens. For 14 lenses of the total 28, the
differences between prescribed and wearing power were obtained; ranged from 0.250 to 2.50 D. The
optical center of a lens was shifted away from its expected position (front of the eye) in 24 cases resulted
decentration from 1.0 to 6.5 mm. Consequently, induced prismatic effect was in range 0.25 - 1.80Δ: with
an average value of 0.73Δ. Further more, obtained results were compared with ANSI Z-90
Standardization Tolerance Chart. In 19 cases, diference in lens power exceed limit of 0.125D and given
limit of 0.33Δ prismatic effect was not satisfied for 14 lenses. Taking into account both criteria only, two
lenses were safe for using according to investigated parameters.
It should be note that even they cannot damage eyes they will impaired the vision and made less
productivity and safety in working with them. Vision is something that we should all take seriously, so
never risk making eye problems worse by postponing a prescription. Even small numbers cases and
parameters, the results of this research indicate a necessity for standardizations as well regulations for
ophthalmic lenses.
| Item Type: | Conference or Workshop Item (Speech) |
|---|---|
| Subjects: | Medical and Health Sciences > Health sciences |
| Divisions: | Faculty of Medical Science |
| Depositing User: | Zdenka Stojanovska |
| Date Deposited: | 04 Feb 2015 09:48 |
| Last Modified: | 04 Feb 2015 09:48 |
| URI: | https://eprints.ugd.edu.mk/id/eprint/12225 |
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