Tissue effects of subclinical diode laser treatment of the retina.
OBJECTIVE
To determine whether consistent tissue effects are obtained when laser lesions are produced with a commercially available diode laser that are near the limit of clinical detection at the time of treatment.


METHODS
Continuous-wave or micropulse diode laser was used to produce clinically undetectable (subthreshold) or barely detectable (threshold) retinal lesions in pigmented rabbits. Tissue effects at intervals after treatment were determined in retinal pigment epithelial (RPE) whole mounts by fluorescence microscopy, and in sections of retina and RPE by light and electron microscopy.


RESULTS
Continuous-wave and micropulse laser lesions that were originally clinically undetectable were detectable as zones of pigment mottling after 5 days. By microscopy, compaction and/or swelling was seen in the outer retina, and cells in the RPE monolayer became heterogeneous in size, shape, and pigmentation, but the tissue responses in the outer retina and RPE were variable even within and among lesions in the same eye.


CONCLUSIONS
Subthreshold energies used to create both continuous-wave and micropulse laser lesions produced variable effects on the RPE and the overlying neurosensory retina. It appears that, near the minimum effective dose of laser irradiation, individual RPE cell heterogeneity becomes detectable as variability in sensitivity to laser injury.


CONCLUSIONS
As laser energy is reduced to limit collateral tissue damage in clinical applications, it may be difficult to generate reproducible lesions because of heterogeneity among individual cells.
Pollack
J S
JS
Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, USA.
Kim
J E
JE
Pulido
J S
JS
Burke
J M
JM
D000818:Animals; D017075:Laser Coagulation; D009887:Ophthalmoscopy; D010857:Pigment Epithelium of Eye / Q000473:pathology / Q000648:ultrastructure; D011817:Rabbits; D012160:Retina / Q000473:pathology* / Q000601:surgery* / Q000648:ultrastructure