After a cataract surgery procedure with vitreous loss a vitreous strand remained in the wound. An unusual visual impairment was observed.A shift in refraction depending on the pupillary diameter was observed. In miosis the refraction was estimated to +1.0 sph, in mydriasis -1.0 sph/ -0.5 cyl, respectively.We presumed that the vitreous strand between the iris and the intraocular lens caused an axial displacement of the IOL during the change from miosis to mydriasis and v.v. Therefore the vitreous strand was surgically eliminated. After surgery the refractive changes by pupillary actions were overcome. In a computer simulation (ray tracing), the amount of axial displacement of the IOL was estimated to 1.5 mm.This paper reminds of considering other reasons for loss of VA than CME, e.g. axial displacement of IOL. An adequate method of examination is the measurement of refraction in miosis and mydriasis.