Individually Designed PALs vs. Power Optimized PALs Adaptation Comparison

Abstract

ABSTRACT

The object of the present study is the analysis of the factors determining adaptation to progressive addition lenses (PAL) of the first-time users. Only novice test persons were chosen in order to avoid the bias of previously worn particular lens design. In everyday life we encounter ever-growing demand for better visual acuity at all viewing distances. The presbyopic population needs correction to far, near and intermediate distance with different dioptric powers and PAL lenses are the most suitable solution. For optimal results with this type of lens, several individual parameters must be considered: correct refraction, precise ocular and facial measures and proper mounting of lenses into the frame. Nevertheless, first time wearers encounter various difficulties in the process of adapting to this type of glasses and adaptation time differs greatly between individual users. It is known that the time of adaptation can be improved if all the parameters related to the user's eye and spectacle frame are taken into account: pupillary distance, fitting height, back vertex distance, pantoscopic angle and curvature of the frame. The adaptation can be further facilitated by designing individual viewing zones within the progressive corridor, accordingly to user’s daily activities (e.g. expanded middle zone for computer work). The question that arises is how much the above-mentioned individual parameters really affect the ease of adaptation and comfort when wearing progressive glasses. To clarify this, in the present study, the individual PAL lenses (with inclusion of all mentioned options of individual design) were compared to customized PAL (respecting pupillary distance and fitting height only). Adaptation process was monitored over a period of four weeks. The collected results represent scores of user’s subjective impressions, where the users themselves rated their adaptation to new progressive glasses and the degree of subjective visual acuity. The results show that adaptation time to fully individually fit PAL is easier. The information obtained from users is valuable in everyday optometry practice because along with the manufacturer's specifications, the user’s experience can give us a better insight in design and characteristics of progressive lenses.