[Devitalization of lens epithelium cells by dye-enhanced therapy]

Hitherto secondary cataract has been usually treated by Nd:YAG laser, which results in a dissection of the capsule with possible complications e.g. retinal detachment. Selective removal of the epithelial cells from the posterior capsule has not been possible. By use of dyes in connection with laser light of a suitable wavelength, lens epithelial cells could potentially be selectively destroyed. We investigated the dye indocyanine green, which has a peak absorbtion at the emission wavelength of commercially available diode lasers.

Human lens epithelial cells and 3T3 cells (mouse embryonal fibroblasts) were grown in MEM with 10% FBS. Confluent and preconfluent layers were incubated with indocyanine green and treated with a diode laser attached to a slit lamp (810 nm, Zeiss VISULAS, Zeiss Oberkochen, Germany).

Indocyanine green alone was toxic in concentrations above 5 mg/ml (60 min). Combined with laser treatment (200 mW, 100 ms, 160 microns), indocyanine green led to cell damage in preconfluent cultures at concentrations above 0.01 mg/ml (10 min). After about 2 days irradiated cells became necrotic and began to desquamate from the culture disc. Cells in confluent cultures could be devitalised at concentrations above 0.05 mg/ml (10 min) using the same power. In contrast, neither indocyanine green alone nor diode laser alone could interfere with epithelial proliferation.

The experiments show the possibility of dye-enhanced therapy of lens epithelial cells with indocyanine green and diode laser. In contrast to other photosensitizers, indocyanine green is widely used in human function tests. Therefore its use for the treatment of secondary cataracts may merit discussion.