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Tissue effects of subclinical diode laser treatment of the retina
J S Pollack1, J E Kim, J S Pulido
1Department of Ophthalmology, Medical College of Wisconsin, Milwaukee, USA.
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.
Clinical Relevance:
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.
Insights
Diode laser treatment near the clinical detection limit produced variable retinal pigment epithelial (RPE) and outer retina effects in rabbits. Individual RPE cell heterogeneity may explain inconsistent laser lesion outcomes.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Retinal Research
Background:
- Diode lasers are used in ophthalmology for retinal treatments.
- Achieving consistent therapeutic effects with minimal laser energy is clinically desirable.
- Subthreshold laser parameters aim to reduce collateral tissue damage.
Purpose of the Study:
- To evaluate the consistency of tissue effects from diode laser lesions near the clinical detection threshold.
- To investigate the impact of subthreshold and threshold laser energies on retinal tissues.
Main Methods:
- Retinal lesions were created in pigmented rabbits using continuous-wave or micropulse diode lasers at subthreshold or threshold levels.
- Tissue effects were analyzed using fluorescence microscopy, light microscopy, and electron microscopy at various time points post-treatment.
Main Results:
- Clinically undetectable laser lesions became visible as pigment mottling after 5 days.
- Microscopy revealed variable changes in the outer retina and retinal pigment epithelium (RPE) cell morphology.
- Significant variability in tissue responses was observed within and between lesions in the same eye.
Conclusions:
- Subthreshold diode laser energies induce inconsistent effects on the RPE and neurosensory retina.
- Individual RPE cell heterogeneity contributes to variable sensitivity and lesion outcomes near the minimum effective laser dose.
- Reducing laser energy for clinical applications may compromise lesion reproducibility due to cellular variability.