filtering of blue light can increase depression, especially in the winter months (SAD). The trademarked "Natural Yellow" material is available in three hydrophilic IOLs. Dr. Patrick H. Benz of Benz Research and Development created the first IOL material to incorporate the same UV-A blocking and violet light filtering chromophore that's present in the human crystalline lens in order to attempt to protect the retina after cataract extraction of the natural crystalline lens. A Cochrane Review found little evidence of important differences between blue‐light filtering and non‐blue‐light filtering lenses for protecting the macula (back of the eye) after cataract surgery. This may have been due to studies being too small and too short‐term to provide reliable results. Posterior capsule opacification Posterior capsule opacification (PCO), often referred to as "after cataract", is the most common complication of cataract surgery. In a small percentage of patients, posterior chamber intraocular lenses may form PCOs a few months after implantation. They are easily treatable, and typically only require a one-time capsulotomy procedure (using a Nd:YAG laser) to clarify. Materials The materials that have been used to manufacture intraocular lens implants include poly(methyl methacrylate) (PMMA), silicone, hydrophobic acrylate, hydrophilic acrylate and collamer. Poly(methyl methacrylate) (PMMA) was the first material to be used successfully in intraocular lenses. British ophthalmologist Harold Ridley observed that Royal Air Force pilots who sustained eye injuries during World War II involving PMMA windshield material did not show any rejection or foreign body reaction. Deducing that the transparent material was inert and useful for implantation in the eye, Ridley designed and implanted the first intraocular lens in a human eye. Advances in technology have brought about the use of silicone and acrylic polymers, both of which are soft foldable inert materials. This allows the lens to be folded and inserted into the eye through a smaller incision. Specifically, acrylic lenses are a better choice in people who have a history of uveitis or are likely to have to undergo retinal surgery requiring vitrectomy with replacement by silicone oil, such as persons with proliferative diabetic retinopathy or who are at high risk of retinal detachment, such as persons with high myopia. A study found that in participants with a history of uveitis, eyes treated with hydrophobic acrylic IOLs were over twice as likely to have a best corrected visual acuity of 20/40 or more, compared to eyes treated with silicone IOLs. History Sir Harold