Hypotensive Drugs Significantly Reduce Intraocular Lens Clarity

Patients with intraocular lenses (IOL) who are exposed to hypotensive drugs are susceptible to a loss of clarity in the form of changes to light absorbance, discoloration and precipitate formation, according to a laboratory study published in Eye.  

In the study, 4 types of IOLs (2 hydrophilic-acrylic—L1 and L2, and 2 hydrophobic-acrylic — B1 and B2) were soaked in solutions consisting of timolol-maleate 0.5%, dorzolamide 2%, brimonidine-tartrate 0.2%, latanoprost 0.005%, brimonidine-tartrate/timolol-maleate 0.2%/0.5% and dorzolamide/timolol-maleate 2%/0.5%. Nontreated IOLs and IOLs soaked in balanced salt solution (BSS) were used as controls. 

The investigators sealed all treated lenses in containers and placed these lenses in an oven at 82˚ Celsius for 120 days. They assessed each IOL using 4 different examinations: light microscopy imaging, light absorbance measurements, scanning electron microscope (SEM), and energy dispersive x-ray spectrometry (EDX).

A total of 98 IOLs (49 hydrophilic lenses and 49 hydrophobic lenses) were included in the study. The researchers observed that all BSS-soaked IOLs seemed clear with no significant discoloration or precipitate-formation. They note that light absorbance in these lenses were similar to nonsoaked, nonheated IOLs. The team did not identify any calcium or phosphate in either of the groups. They found that light absorbance differed significantly between the 4 IOL types.

The drops most affecting light absorbance differed among IOLs, according to the report. Gross examination demonstrated brown and yellow discoloration in all IOLs soaked in dorzolamide and brimonidine-tartrate solutions, respectively. SEM showed precipitates that differed in size, morphology and distribution, among different IOL-solution combinations. EDXs showed calcium and phosphor in the majority of precipitates and sulfur in brown discolored IOLs.

“This in vitro study preliminary demonstrated a clear correlation between IOLs’ loss of clarity and exposure to hypotensive drugs,” according to the researchers. “Hypotensive drugs significantly affect hydrophobic and hydrophilic IOL clarity in vitro. This manifests as changes in light absorbance, discoloration, and precipitate formation.”

Study limitations include failure to evaluate the effects of non-active ingredients (including those of the preservative), conditions in the study significantly differed compared with conditions in the human eye, and the visual significance of these results require further evaluation.