Analysis of surface whitening of extracted hydrophobic acrylic intraocular lenses.
OBJECTIVE
To identify the cause of light scattering on the surface (ie, whitening) of extracted AcrySof intraocular lenses (IOLs).


METHODS
Department of Ophthalmology, Dokkyo Medical University, Tochigi, Japan.


METHODS
Dislocated IOLs extracted from 3 patients were stored and the IOL surfaces examined under light microscopy. The effect of whitening on visual function was evaluated by measuring light transmission with a spectrophotometer. To determine the cause of opacification, the IOLs were examined for calcium phosphate deposits using an electron probe X-ray microanalyzer. The IOL surface, including the presence of organic deposits and evidence of hydrolysis, was also examined by Fourier-transform infrared spectrophotometry. The IOLs were then dried, immersed again in physiological saline, and serially examined for changes in opacification.


RESULTS
The optic surfaces of all IOLs had opacification due to whitening. Light transmission in the visible range of 360 to 800 nm was 4% less than that of unused IOLs. The X-ray microanalysis showed no calcium phosphate deposits. Fourier-transform infrared spectrophotometry of the IOL optic material showed no evidence of hydrolysis. Opacification disappeared after the IOLs were dried and then reappeared over time when the IOL was immersed again in physiologic saline.


CONCLUSIONS
The findings strongly suggest that whitening of the hydrophobic acrylic IOL was due to trace water molecules that infiltrate the optic. Within the 3-dimensional network of the polymeric lens material, the molecules are too small to form observable voids but can form water aggregates of sufficient size to scatter visible light, causing opacification (ie, whitening).
Matsushima
Hiroyuki
H
Department of Ophthalmology, Dokkyo Medical University, Tochigi, Japan. hiro@dokkyomed.ac.jp
Mukai
Koichiro
K
Nagata
Mayumi
M
Gotoh
Norihito
N
Matsui
Eiichiro
E
Senoo
Tadashi
T
D000368:Aged; D000369:Aged, 80 and over; D002130:Calcium Phosphates / Q000032:analysis; D020878:Device Removal; D004577:Electron Probe Microanalysis; D019544:Equipment Failure Analysis; D005136:Eye Proteins / Q000032:analysis; D005260:Female; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D007910:Lenses, Intraocular; D008027:Light; D008297:Male; D008689:Methacrylates; D011108:Polymers; D011475:Prosthesis Failure; D012542:Scattering, Radiation; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared
D002130:Calcium Phosphates; D005136:Eye Proteins; D008689:Methacrylates; D011108:Polymers; C104020:poly(methylmethacrylate-co-ethylhexylmethacrylate); C020243:calcium phosphate