Many Ready-Made Reading Spectacles Fail the Required Standards

BCLA CLEAR Presbyopia: Management with contact lenses and spectacles

This paper seeks to outline the history, market situation, clinical management and product performance related to the correction of presbyopia with both contact lenses and spectacles. The history of the development of various optical forms of presbyopic correction are reviewed, and an overview is presented of the current market status of contact lenses and spectacles. Clinical considerations in the fitting and aftercare of presbyopic contact lens and spectacle lens wearers are presented, with general recommendations for best practice. Current options for contact lens correction of presbyopia include soft simultaneous, rigid translating and rigid simultaneous designs, in addition to monovision. Spectacle options include single vision lenses, bifocal lenses and a range of progressive addition lenses. The comparative performance of both contact lens and spectacle lens options is presented. With a significant proportion of the global population now being presbyopic, this overview is particularly timely and is designed to act as a guide for researchers, industry and eyecare practitioners alike.

Visual performance of new affordable and auto-adherent lenses for presbyopia correction

Presbyopia is a visual condition that affects all of us, evolving with time, reducing the range of accommodation and the ability to work at near. Reading glasses, bifocals or multifocal lenses are the most common solutions. In this work, we demonstrate the near visual performance of new elastomeric auto-adherent lenses developed for the correction of presbyopia. Visual acuity and contrast sensitivity were measured in 10 presbyopic subjects. The results showed that wearing either conventional trial ophthalmic lenses or the new elastomeric lenses provided similar visual quality. These elastomeric lenses can be placed in, or removed from the distance-vision spectacles of the wearers, providing an affordable solution for correcting presbyopia at its clinical onset, which might be especially useful in subjects with different refractive error in each eye and for those with astigmatism.

Modelling ready-made spectacle coverage for children and adults using a large global database

BACKGROUND/AIMS

To model the suitability of conventional ready-made spectacles (RMS) and interchangeable-lens ready-made spectacles (IRMS) with reference to prescribing guidelines among children and adults using a large, global database and to introduce a web-based application for exploring the database with user-defined eligibility criteria.

METHODS

Using refractive power and interpupillary distance data for near and distance spectacles prescribed to children and adults during OneSight clinics in 27 countries, from 2 January 2016 to 19 November 2019, we modelled the expected suitability of RMS and IRMS spectacle designs, compared with custom-made spectacles, according to published prescribing guidelines.

RESULTS

Records of 18 782 presbyopic adult prescriptions, 70 619 distance adult prescriptions and 40 862 paediatric prescriptions were included. Globally, 58.7%-63.9% of adults could be corrected at distance with RMS, depending on the prescribing cut-off. For presbyopic adult prescriptions, coverage was 44.1%-60.9%. Among children, 51.8% were eligible for conventional RMS. Coverage for all groups was similar to the above for IRMS. The most common reason for ineligibility for RMS in all service groups was astigmatism, responsible for 27.2% of all ineligible adult distance prescriptions using the strictest cut-off, 31.4% of children's prescriptions and 28.0% of all adults near prescriptions globally.

CONCLUSION

Despite their advantages in cost and convenience, coverage delivered by RMS is limited under current prescribing guidelines, particularly for children and presbyopic adults. Interchangeable designs do little to remediate this, despite extending coverage for anisometropia. Our free application allows users to estimate RMS coverage in specific target populations.

Assessment of optical quality of ready-made reading spectacles for presbyopic correction

PURPOSE

Many presbyopic patients in both developed and developing countries use ready-made reading spectacles for their near vision correction even though the quality of these spectacles cannot always be assured. This study assessed the optical quality of ready-made reading spectacles for presbyopic correction in comparison with relevant international standards.

METHODS

A total of 105 ready-made reading spectacles with powers ranging from +1.50 to +3.50 dioptres (D) in +0.50 D steps were randomly procured from open markets in Ghana and assessed for their optical quality, including induced prisms and safety markings. These assessments were done in line with the International Organization for Standardization (ISO 16034:2002 [BS EN 14139:2010]) as well as the standards used in low-resource countries.

RESULTS

All lenses (100%) had significant induced horizontal prism that exceeded the tolerance levels stipulated by the ISO standards, while 30% had vertical prism greater than the specified tolerances. The highest prevalence of induced vertical prism was seen in the +2.50 and +3.50 D lenses (48% and 43%, respectively). When compared with less conservative standards, as suggested for use in low-resource countries, the prevalence of induced horizontal and vertical prism reduced to 88% and 14%, respectively. While only 15% of spectacles had a labelled centration distance, none had any safety markings per the ISO standards.

CONCLUSION

The high prevalence of ready-made reading spectacles in Ghana that fail to meet optical quality standards indicates the need for more robust, rigorous and standardised protocols for assessing their optical quality before they are sold on the market. This will alleviate unwanted side effects including asthenopia associated with their use. There is also the need to intensify public health awareness on the use of ready-made reading spectacles, especially by patients with significant refractive errors and ocular pathologies.

Refractive error correction among urban and rural school children using two self-adjustable spectacles

Objective

Self-refracting spectacles (SRSs) have different optical and mechanical designs, which may affect the refractive outcome, depending on the experience of the end user. This study compared the performance of two SRS among children in Ghana.

Methods and analysis

A cross-sectional study of two Alvarez variable-focus SRS designs was conducted. A total of 167 children (mean age 13.6±1.6 years) identified as having refractive error were recruited from 2465 students who underwent screening. Subjects completed self-refraction using FocusSpecs, and Adlens, autorefraction and cycloplegic subjective refraction (CSR) (gold standard). Wilcoxon signed-rank test was used to compare visual outcomes and accuracy of refraction and graphically illustrated using Bland-Altman plots.

Results

Eighty (47.9%) urban and 87 (52.1%) rural children were analysed and only about one-quarter 40 (24.0%) wore spectacles. The proportion who achieved visual acuity of ≥6/7.5 with FocusSpec, Adlens, autorefraction and CSR among urban schools were 92.6%, 92.4%, 60% and 92.6%, while those in rural schools were 81.6%, 86.2%, 54.0% and 95.4%, respectively. The mean±SD spherical equivalent errors for urban and rural schools using FocusSpec, Adlens and CSR were −1.05±0.61 D, –0.97±0.58 D and −0.78±0.53 D; and −0.47±0.51 D, –0.55±0.43 D and −0.27±0.11 D, respectively. The mean differences between the two self-refraction spectacles for urban and rural schools were not statistically different (p>0.00) but differed significantly when both were compared with the gold standard (CSR) (p<0.05).

Conclusion

Background and refraction experience of school children did not significantly affect self-refraction.

A Comparison of Spectacles Purchased Online and in UK Optometry Practice

Purpose

To compare spectacles bought online with spectacles from optometry practices.

Methods

Thirty-three participants consisting of single vision spectacle wearers with either a low (N = 12, mean age 34 ± 14 years) or high prescription (N = 11, mean age 28 ± 9 years) and 10 presbyopic participants (mean age 59 ± 4 years) wearing progressive addition lenses (PALs) purchased 154 pairs of spectacles online and 154 from UK optometry practices. The spectacles were compared via participant-reported preference, acceptability, and safety; the assessment of lens, frame, and fit quality; and the accuracy of the lens prescriptions to international standard ISO 21987:2009.

Results

Participants preferred the practice spectacles (median ranking 4th, IQR 1–6) more than online (6th, IQR 4–8; Mann-Whitney U = 7345, p < 0.001) and practice PALs (median ranking 2nd, IQR 1–4) were particularly preferred (online 6.5th, IQR 4–9, Mann-Whitney U = 455, p < 0.001). Of those deemed unacceptable and unsafe, significantly more were bought online (unacceptable: online 43/154 vs. practice 15/154, Fisher’s exact p = 0.0001; unsafe: online 14/154 vs. practice 5/154, Fisher’s exact p = 0.03).

Conclusions

Participants preferred spectacles from optometry practice rather than those bought online, despite lens quality and prescription accuracy being similar. A greater number of online spectacles were deemed unsafe or unacceptable because of poor spectacle frame fit, poor cosmetic appearance, and inaccurate optical centration. This seems particularly pertinent to PAL lenses, which are known to increase falls risk. Recommendations are made to improve both forms of spectacle provision.

Analysis of readymade readers and near–inter-pupillary distance for presbyopic patients in optometric practice in Cape Town, South Africa

Purpose and background: This study has particular significance in ophthalmic dispensing as well as for optometry when considering the use of readymade readers (RMRs) both in private practice and in the public health sector. This study investigated firstly whether the optical centre (OC) distance for a sample of RMRs correlates with the near–inter-pupillary distance (near-IPD) for presbyopic patients, whether induced prism occurs with convergence when reading and whether RMR lenses are free of optical strain. Methods: Near-IPDs (measured by a single individual) were obtained from record cards of 1080 patients (540 male patients and 540 female patients). The OC distances were determined for 60 RMRs using a Nikon PL-2 screen vertometer, and induced prismatic effects were calculated for vertical and horizontal meridians. The presence of optical strain was analysed and graded using crossed polarised filters (within a polariscope). Results: The measured average near-IPD was 59.04 mm (s.d. ±2.87) for the 540 female patients and 61.59 mm (s.d. ±3.08) for the 540 male patients. The measured average RMR OC distance was 64.49 mm (s.d. ±3.74) for female patients and 62.77 mm (s.d. ±1.57) for male patients. Based on the mean near-IPD and the corresponding RMR OC distance, the average horizontal prismatic effect found in RMRs designed for female patients with induced prism was 0.11 pd base-out (5.06 mm outwards) and 0.04 pd base-in (1.26 mm inwards). For male RMRs, this was 0.03 pd base-out (1.32 mm outwards) and 0.02 pd base-in (1.28 mm inwards). When comparing RMR distances with near-IPDs, t = -7.87, p < 0.001 for female patients and t = -3.69, p < 0.001 for male patients. The average vertical differential prismatic effect for female patients was 0.67 pd and it was 0.68 pd for male patients. Optical strain was observed in 66.67% and 56.67% of RMR lenses for female and male patients, respectively. The strain pattern was found to be most severe in the inferior temporal periphery for 34 RMRs for female patients and for 20 RMRs for male patients, followed by the inferior nasal periphery for 27 and 18 lenses (RMRs) for male and female patients, respectively. Conclusion: Most RMRs were found to be within international standard tolerances for horizontally induced prismatic effects, but 10% of female and 36.67% of male RMRs had vertical prismatic effects, which exceeded international standards. Significant optical strain was found in the inferior nasal reading portion of the RMRs. Keywords: Readymade readers (RMR’s); prismatic effect; strain; interpupillary distance; presbyopia; reading

Nasopupillary Asymmetry

Purpose. To establish the prevalence of nasopupillary asymmetry (difference in nasopupillary distances) in the population and its relation with the interpupillary distance. Methods. A retrospective descriptive study was conducted by reviewing of 1262 medical records. The values of nasopupillary asymmetry and the interpupillary distance were obtained. A statistical analysis was made and the correlation between these variables was established. Results. Seventy-nine percent of the population presented some degree of nasopupillary asymmetry. The interpupillary distance had a very low correlation with the nasopupillary asymmetry (r = 0.074, P = 0.0). Conclusion. It is advisable to use the nasopupillary distance of each eye as a standard measurement.

Influence of age on measured anatomical and physiological interpupillary distance (far and near), and near heterophoria, in Arab males

PURPOSE

To compare the effects of age and near phoria on interpupillary distance measured at far (FIPD) and near (NIPD) using the Viktorin's and pupillometer (PD-5) methods.

METHODS

Interpupillary distance (IPD) by Viktorin's method and the corneal reflex pupillometer (PD-5) method, as well as near heterophoria by the Saladin near point card, were each obtained on 133 randomly selected normal subjects aged 20-67 years. Comparison within and between techniques, influence of age on IPD, and near heterophoria were assessed.

RESULTS

The mean FIPD varied significantly from the NIPD (P < 0.001 for both methods). Overall, FIPD ranged from 56-73 mm, and NIPD ranged from 50-70 mm. For FIPDs of 55 mm, 63 mm, and 71 mm, the corresponding NIPDs were less by 3.9 mm, 4.4 mm, and 5.0 mm, respectively, which were measured by Viktorin's method, and 4.0 mm, 4.6 mm, and 5.2 mm, respectively, measured by the PD-5 method. Between methods, the limits of agreement were: -3.9 mm and 3.2 mm (P > 0.05) for FIPD, and -3.1 mm and 2.9 mm (P > 0.05) for NIPD. Both IPDs varied significantly across age groups (P < 0.0001). Post hoc analysis revealed a significant variation (P < 0.01 in both techniques) only in the comparison between age groups 16-25 years and 41-67 years. The mean difference was -2.2 mm (-4.0 mm to -0.3 mm) and -2.8 mm (-4.7 mm to -1.0 mm) for Viktorin's method for FIPD and NIPD, respectively. For PD-5, the corresponding values were -1.3 mm (-3.2 mm to 0.4 mm) and -1.7 mm (-4.1 to -0.5 mm). Also, the near phoria differed significantly (P < 0.0001) across age groups and correlated positively with age (r(2) = 0.27, P < 0.0001) and NIPD (r(2) > 0.04; P < 0.03, both techniques).

CONCLUSION

The difference between FIPD and NIPD (about 4.4 mm in Arab males) was observed independent of the technique used. The Viktorin's and the PD-5 methods of IPD assessment resulted in similar values, and therefore, could be interchangeably used. However, caution is advised in cases of high power refractive corrections as the difference could vary from -4 mm to +3 mm (FIPD) and -3 mm to +3 mm (NIPD). Both IPDs have demonstrated an increase until the patients are in their early 40s, and a slight decrease has been observed thereafter. Age and NIPD were significantly associated with heterophoria in our subjects.