Recognising the harmful effects of various light rays on the retina, manufacturers have set about developing IOLs with various light filtering properties. Here, Boris Malyugin and Tatiana Fadeeva put the YellowFlex lens to the test.
Some of the most important functional indicators of a pseudophakic eye, in addition to visual acuity at near and far distances, are full colour perception, high spatial contrast sensitivity and low contrast visual acuity. The removal of a native crystalline lens leads to loss of natural filtration of ultraviolet radiation and may cause the development of retinal degeneration.
Harmful effects of UV rays are acknowledged
In the late 1980s and early 1990s, research into the spectral properties of IOL optics intensified considerably. Having established the capacity of the crystalline lens to protect the retina from the harmful effects of blue rays, manufacturers began to work on developing an IOL containing a yellow filter. The first such lenses were the "Spektr" model IOLs, manufactured at the Intersectoral Research and Technology "Eye Microsurgery Complex" in Russia. Since then, over one million such lenses have been implanted.
Flexing some yellow muscle
Recognising the benefits of yellow light filtration, several manufacturers have launched their own yellow filtering lenses: AcrySof Natural (Alcon), Orange IOL (Ophtec), UVCY (Hoya) and YellowFlex (PhysIOL).1
I am going to discuss my experience with the YellowFlex lens; the only currently available flexible, hydrophilic acrylic (26%) IOL with a light filter.
In terms of its characteristics, the lens has a diameter of 10.5 mm with a 6.0 mm optic and it can be implanted either with an injector or with the aid of forceps. The lens optic has a 360° square edge (Two step), which prevents posterior capsule fibrosis. A dye called BlueTec gives the lens its yellow tint and captures blue light.
Putting it to the test
In the period from December 2005 to May 2006, 37 patients aged 25 to 87 years (average age 68±11.8 years) with senile cataracts of different grade were treated with phacoemulsification and implantation of a YellowFlex. The preoperative evaluation included visual acuity, keratometry, tonometry, perimetry, A and B scans, electrophysiological examinations, biomicroscopy and ophthalmoscopy tests. Meanwhile, postoperative evaluations also included visocontrastometry and colour sensitivity testing, low contrast visual acuity and aberrometry.