The effect of hypotensive drugs on intraocular lenses clarity

Abstract

Objectives: To assess the effect of hypotensive drugs on light absorbance, discoloration, opacification and precipitate formation of IOLs.

Methods: In this laboratory study, four types of IOLs (two hydrophilic-acrylic-L1 and L2, and two hydrophobic-acrylic-B1 and B2) were soaked in solutions containing 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%. Non-treated IOLs and IOLs soaked in balanced salt solution (BSS) served as controls. All Treated lenses were sealed in containers and placed in an oven at 82 degrees Celsius for 120 days. Each IOL was examined using four different techniques: light microscopy imaging, light absorbance measurements at 550 nanometers through the optic's center, assessment of by a scanning electron microscope (SEM), and energy dispersive Xray spectrometry (EDX).

Results: Ninety-eight IOLs were included. All BSS-soaked IOLs appeared clear with no significant discoloration or precipitate-formation. Light absorbance in these lenses was comparable to that of non-soaked, non-heated IOLs. No calcium or phosphate were detected in either of these groups. Light absorbance differed significantly between the four treated IOL types. The drops most affecting light absorbance differed between IOLs. Gross examination revealed brown and yellow discoloration of all IOLs soaked in Dorzolamide and Brimonidine-tartrate solutions, respectively. SEM demonstrated precipitates that differed in size, morphology and distribution, between different IOL-solution combinations. EDX's demonstrated the presence calcium and phosphor in the majority of precipitates and the presence of sulfur in brown discolored IOLs.

Conclusions: In vitro, interactions between hypotensive drugs and IOLs induce changes in light absorbance, discoloration and precipitate formation.

Fig. 1. Different phenomena identified by gross inspection.

A Distribution of phenomena by drug type. B Distribution of phenomena by IOL type. L1 first type of hydrophilic acrylic IOL, L2 second type of hydrophilic acrylic IOL, B1 first type of hydrophobic acrylic IOL, B2 second type of hydrophobic acrylic IOL.

Fig. 2. Discoloration of IOLs.

IOLs soaked in Brimonidine showing yellow discoloration and IOLs soaked in Dorzolamide showing brown discoloration as compared to untreated controls and BSS-soaked controls.

Fig. 3. Precipitates.

I—Precipitates formed on different IOLs with different hypotensive drugs. II—Precipitates on hydrophilic and hydrophobic IOLs soaked in different solutions. Precipitates differ in distribution, size, and morphology in different IOL-drug combinations. There is a good correlation between SEM (A) and light microscopy imaging (B) in different IOLs and different solutions.

Fig. 4. Light absorbance.

A Light absorbance (percentage of light transmitted) of different IOL models which were soaked in different solutions. There was a statistically significant interaction between the effects of IOL type and type of solution on mean light absorbance. B a boxplot that depicts the absorbance divided by type of lenses. C Light absorbance for all IOLs in the different solutions.