Never is better than late for silicone IOL implantation

By Stefanie Petrou Binder MD

Heidelberg — An interesting case study describing opacification of a silicone IOL ten years after implantation has made researchers wonder whether more IOLs might tend to opacify if given enough time.

Michael Martin MD, of the Heidelberg University Eye Clinic, described the case at the annual meeting of the DGII (German-Speaking Organisation of Intraocular Lens Implantation and Refractive Surgery).

The patient was a 58-year-old female who received a +22 D silicone IOL (FKI, Silkon Optik) in her right eye following cataract surgery in 1991. Three years later, a +22.5 D PMMA IOL (728A, Kabi Pharmacia) was implanted in her left eye, with 13.5 mm overall diameter (7.0 mm optic diameter). 

Both eyes received IOLs of almost the same strength. However, her corrective lens prescription showed considerable variation between the eyes. The left eye was corrected for +0.5 sph / -0.5 cyl / 85° and right eye +2.25 sph / -0.75 cyl / 120°. The patient was referred to the clinic again in 2001 complaining of a slowly deteriorating visual acuity in her right eye along with glare sensitivity.

“It was the patient’s right eye that caught our interest. Biomicroscopic exams revealed white, milky opacification in the central optic zone of the silicone IOL. The opacification formed a circular pattern on the peripheral aspect of the optic. We detected this ring-shaped opacification using retroillumination,” Dr Martin recalled. 

He noted that despite this lens opacification, the patient’s subjective visual acuity registered a surprisingly good 0.8 D. There was no evidence of intraocular irritation, widespread anterior or posterior capsule leaf fibrosis or capsulorhexis shrinkage. The patient was managed with hyperopic corrective lenses. The silicone IOL was not removed or replaced since the patient had good vision, and capsular leaf adhesion was likely to have been adequate due to the large optic surface area.

“All IOL materials can undergo biodegradation. The resultant IOL opacification may -or may not - appear long after implantation. As most patients receive IOLs at an advanced age, however, the likelihood of poor visual acuity resulting from material biodegradation opacifications is low. Indeed, opacification and discoloration resulting from production errors are more frequent,” he noted.

Silicone lenses have been on the market longer than any other type of foldable IOL.
In the 1980s, studies showed yellow staining of silicone IOLs. However, the high quality silicone materials now in use has made yellow staining silicone IOLs a thing of the past. 

Opacification is now more often associated with acrylic hydrophilic foldable lenses and this has been traced to potential errors in the production and sterilisation processes.

“It may be time to again consider the possibility of opacification in silicone lenses. This case suggests a new factor that can influence IOL opacification – material biodegradation related to implantation time. This may become more of an issue as patients get younger and implantation duration increases,” Dr Martin said.