Perfect tolerance is expected when one implants a phakic intraocular lens (pIOL) in the anterior segment. Not only should the material be compatible, but the pIOL must respect the anatomy of the anterior chamber. Based on 3 years of experience using an anterior segment optical coherence tomographer (Visante OCT, Carl Zeiss Meditec), I have defined numerous safety criteria for pIOLs. The internal dimensions of the anterior chamber must be considered along different meridians. I propose an objective measurement of the iris dome, the crystalline lens rise (CLR), which is the distance between the anterior pole of the crystalline lens and a line joining the 2 opposite iridocorneal angles. In a series with the Artisan IOL (Ophtec), pigment dispersion syndrome appeared in 70% of cases in which the CLR was greater than 600 microm. Angle-supported IOLs must be placed relative to the anterior chamber's largest diameter; in the same series of cases, the anterior chamber was oval with a large vertical axis in 74% of cases. The posterior face of an angle-supported IOL must have a 700 microm vault to respect the physiological modifications of the crystalline lens. It is difficult to know the posterior chamber's exact diameter as it varies with the horizontal or vertical axis. It also undergoes constant modifications due to accommodation and aging.