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

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.

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.

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.

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.