Dysfunctional Lens Syndrome: Molecular, Biomechanical, Optical and Clinical Aspects of Crystalline Lens Aging

Dysfunctional Lens Syndrome (DLS) represents a progressive age-related decline in the optical and functional performance of the crystalline lens. Although cataract remains the most clinically recognizable endpoint of lens aging, important visual changes often occur much earlier, including presbyopia, increased higher-order aberrations (HOAs), intraocular scatter, reduced contrast sensitivity and deterioration of retinal image quality. These changes reflect progressive molecular, biomechanical and optical alterations within the aging crystalline lens in different stages.

This narrative review was based on a literature search on PubMed and reference list of relevant review articles, clinical studies and book chapters published during the last 25 years, using terms related to DLS, crystalline lens, lens aging, lens biomechanics, presbyopia, HOAs, dysfunctional lens index and refractive lens exchange. Articles were selected according to their relevance and provided evidence to the molecular, biomechanical, optical, clinical and therapeutic aspects of lens aging.

Available evidence indicates that lens aging begins before clinically significant cataract becomes evident. Molecular changes in long lived crystallins, impaired redox homeostasis, altered ion-water balance and membrane remodeling contribute to increased lens density, reduced transparency and protein aggregation. These changes are accompanied by progressive lens growth, nuclear stiffening, loss of accommodation, alteration of the gradient refractive index, HOAs, intraocular scatter and reduced contrast sensitivity.

Recognition of DLS may improve the assessment of patients with preserved visual acuity but impaired quality of vision. A broader evaluation of crystalline lens function may support more individualized decision-making in presbyopia management, cataract surgery and lens-based refractive procedures. An integrated perspective for the management of DLS in its different stages is proposed as a guidance for the practical ophthalmologist.