Background: Opacification of Hydroview posterior chamber intraocular lenses had been prescribed, but many aspects of this complication remain unknown, including its aetiology, clinical features, pathogenesis, prognosis and treatment. This paper describes an epidemic of Hydroview intraocular lens (IOL)-opacification. Methods: Subjects in whom the Hydroview IOL was implanted were recalled for evaluation of its transparency, assessment of contrast sensitivity (CS) VCTS (Vistech CO, Dayton, Ohio, USA) and visual acuity (LogMAR), and analysis of medical and surgical data. The results of IOL exchange in 69 eyes of 67 patients are also presented. Results: Of 103 patients recalled, 46 (44.6%) and 3 (2.9%) exhibited opacification of the implanted IOL in one and both eyes, respectively. CS was significantly worse in the presence of an opacified IOL (P< 0.050), even when Snellen acuity was unaffected. Where the viscoelastic employed during the primary cataract surgery was reliably documented,VISCOAT was used in 100%of cases (43/43), whereas Healonid had not been used in any (0/57)-(P< 0.0001). Following IOL exchange, visual acuity improved from a mean (±SD) of 0.75 (0.41) to 0.4 (0.34) LogMAR. Conclusions: The prevalence of Hydroview IOL opacification is associated with the use of VISCOAT in the primary cataract surgery, and there is a biochemically plausible rationale to account for this. Visual acuity and contrast sensitivity are adversely affected by opacification of the Hydroview IOL, but CS to a greater extent. Exchange of opaque IOLs is a visually rewarding procedure. Background: Opacification of Hydroview posterior chamber intraocular lenses had been prescribed, but many aspects of this complication remain unknown, including its aetiology, clinical features, pathogenesis, prognosis and treatment. This paper describes an epidemic of Hydroview intraocular lenses (IOL) -opacification. Methods: Subjects in whom the Hydroview IOL was implanted were recalled for evaluation of its transparency, assessment of contrast sensitivity (CS) VCTS (Vistech CO, Dayton, Ohio, USA) and visual acuity (LogMAR), and analysis of medical and surgical data . Results of IOL exchange in 69 eyes of 67 patients were also presented. Results: Of 103 patients recalled, 46 (44.6%) and 3 (2.9%) showed opacification of the implanted IOL in one and both eyes, respectively. significantly worse in the presence of an opacified IOL (P <0.050), even when Snellen acuity was unaffected. Where the viscoelastic employed during the primary cataract surgery was indeed documented, VISC OAT was used in 100% of cases (43/43), while Healonid had not been used in any (0/57) - (P <0.0001). Following IOL exchange, visual acuity improved from a mean (± SD) of 0.75 (0.41) to 0.4 (0.34) LogMAR. Conclusions: The prevalence of Hydroview IOL opacification is associated with the use of VISCOAT in the primary cataract surgery, and there is a biochemically plausible rationale to account for this. Visual acuity and contrast sensitivity are adversely affected by opacification of the Hydroview IOL, but CS to a greater extent. Exchange of opaque IOLs is a visual rewarding procedure.