Freeform vs. Aspheric Spectacle Lenses: A Comprehensive Review of Optical Performance, Clinical Outcomes, and Patient Considerations.

Spectacle lens design has evolved from spherical lenses to aspheric lenses (ASL) and freeform lenses (FFL) to improve peripheral optics and wearer comfort. In this review, we compare ASLs and FFLs across optical performance, visual function, patient-reported outcomes, and practical considerations. We synthesized evidence from more than 90 peer-reviewed studies, technical reports, and authoritative textbooks. Databases included PubMed, Scopus, Web of Science, and specialist optometry sources. Eligibility focused on comparative ASL vs. FFL studies and high-quality reports. Data were organized into themes (optical performance, visual function, subjective outcomes, and practical issues). Both ASLs and FFLs outperform spherical lenses centrally; however, FFLs demonstrate consistently lower peripheral astigmatism and mean power error, wider usable fields of view (particularly in progressive addition lenses (PALs)), and better contrast sensitivity in mesopic/low-contrast conditions. Personalization of position-of-wear parameters (vertex distance, pantoscopic tilt, wrap) is key to FFL advantages. Adaptation appears faster, and patient satisfaction is higher with FFLs, especially in complex prescriptions and progressive designs. The ASLs are cost-effective for moderate prescriptions and standard fits, while FFLs represent the benchmark for personalized spectacle correction, particularly for high ametropia and PALs, provided there are accurate measurements and quality-controlled manufacturing.