Troubleshooting of Dissatisfied Spectacle Wearers
The management of dissatisfied spectacle wearers is both an art and a science. As in many areas of medicine, the management of expectations is critical. Demonstrations with trial frames and overrefracting with the patient’s existing spectacles may be helpful tools. Major changes (such as cylinder axis changes) should be carefully evaluated and discussed with the patient prior to prescribing. Many potential problems can be prevented with appropriate attention during the prescribing and fitting process. A good working relationship with the optometrist and dispensing optician is critical. The written prescription is helpful in preventing problems. The interpupillary distance (monocular for PALs) should be included. Vertex distance should be specified for high prescriptions. The exact type of bifocal, trifocal, or PAL should be specified or noted if it should remain the same as in the current glasses. Any prismatic correction should be carefully noted, mentioning whether it is the same as the current glasses so that the dispensing optician can verify this. The dispensing optician has extensive latitude in the actual materials and coatings of the lens as well as the type and style of the bifocal and the vertex distance unless it is written on the prescription. For instance, if the prescriber wishes to keep the same base curve as the current spectacles (to decrease changes in image size in the case of anisometropia) this should be specified on the prescription. The lens material should be indicated, especially if it is a high-index or impact-resistant material. Any photochromic or lens tint or other coatings that the prescriber wants the spectacles to have should be specified.
A “balance lens” may be specified for a completely blind eye. This allows the dispensing optician to place a lens that is cosmetically similar to the fellow eye. In some cases, this may lessen the cost of the lens for the patient. Care must be taken in prescribing this for an eye with limited but usable vision (amblyopia, macular degeneration). Leaving the power of this lens at the discretion of the optician with only cosmetic concerns may cause functional problems.
Once the patient presents with dissatisfaction with a new spectacle correction, a detailed history of the problem must be performed. The nature of the complaint should be isolated, if possible, to its source: distance or near vision, static or dynamic, and blurring, distortion, and/or diplopia. The spectacle power and optic center should be determined and confirmed with that ordered. The refraction should be rechecked, especially in the case of a significant difference from the previous spectacle correction.
In the case where the previous spectacle correction is not different from the new one, then a comparison of other properties of the spectacles is helpful. In addition to the verification of the optical centers (induced prism), prismatic correction, or slaboff in the previous correction should also be present in the new prescription. Changes in base curve and center thickness (from old to new) may cause aniseikonia symptoms. If the previous prescription is very old, it should be checked with a Geneva lens clock for plus (front) cylinder design. Differences in bifocal type and position should be noted. Positioning and alignment of PALs should be noted. A change in model of PAL may cause significant problems. A change from traditional bifocals or trifocals to PALs may also be a source of problems. Vertex distance changes and pantoscopic tilt may lead to effective lens power differences. Finally, lens material changes may cause chromatic aberrations.
Excerpted from BCSC 2020-2021 series : Section 3 - Clinical Optics. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.