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[Diode laser thermokeratoplasty. Initial clinical experiences]
G Geerling1, N Koop, A Tüngler
1Klinik und Poliklinik für Augenheilkunde, Medizinische Universität Lübeck.
Summary
This study shows that a continuously emitting laser diode can safely and effectively correct hyperopia using laser thermokeratoplasty (LTK). While regression occurs, the 1.87-micron wavelength offers a promising alternative for hyperopic correction.
Area of Science:
- Ophthalmology
- Biomedical Engineering
- Laser Surgery
Background:
- Pulsed holmium lasers are used for laser thermokeratoplasty (LTK) to treat hyperopia by shrinking corneal collagen.
- This process involves high-repetition rate microsecond pulses, causing significant intrastromal temperature increases.
- Continuously emitting laser diodes offer a steadier temperature rise, potentially improving LTK outcomes.
Purpose of the Study:
- To evaluate the safety and efficacy of diode laser thermokeratoplasty (LTK) for hyperopic correction.
- To assess the amount and stability of hyperopic correction achieved with a continuously emitting laser diode.
- To investigate the impact of different diode laser parameters on corneal tissue and refractive outcomes.
Main Methods:
- Two groups of blind human eyes (n=4 each) received LTK using a diode laser at 1.854 microns (Group I) or 1.87 microns (Group II).
- Coagulations were applied in concentric rings (single or double) using a vacuum-fixed mask and handpiece with focusing optics.
- Ophthalmologic examinations and corneal refractive power measurements were conducted preoperatively and at multiple time points up to 18 months post-surgery.
Main Results:
- Group I achieved initial hyperopic correction up to +4.9 D but experienced significant endothelial defects due to deep penetration.
- Group II achieved higher initial correction up to +6.8 D with reduced endothelial damage due to shallower penetration.
- Partial regression of the refractive effect was observed in all subjects, with more stability in Group II at 12 months (+0.9 to +5.7 D).
- Induced astigmatism was manageable in both groups at 12 months (Group I: 0.5-2.2 D; Group II: 0.3-1.6 D).
Conclusions:
- A continuously emitting 1.87-micron laser diode is safe and effective for hyperopic LTK.
- Regression of the refractive effect is most prominent within the first six postoperative months.
- Further research is needed to develop a nomogram considering patient-specific factors like age for optimal outcomes.