title: Reflectance imaging of the human retina at 810 nm does not suffice to optimize the parameters of hydrodynamic rebalancing laser treatment.
abstract: The hydrodynamic rebalancing laser (HRL) procedure is an ophthalmic therapy based on the administration of subthreshold infrared (810 nm) laser light to selected areas on the retina to treat various retina diseases. Heterogeneities of tissue response are observed, including undesired retinal damages. Variations of tissue absorbance were hypothesized to cause this uneven response. Irradiation parameters (diameter = 100 μm; power = 1 W; irradiation time: 50 to 200 ms), location and tissue response were studied in 16 patients (20 eyes, 2535 laser spots) to discover any correlation between tissue response and normalized fundus reflectance at 810 nm. The results demonstrate a complex relationship between some pathologies and occurrences of retinal damage, but no clear correlation. One possible reason is that the resolution of reflectance images is insufficient to see “small” (40 μm or less) absorption centers, particularly deep-seated ones. Additionally, tissue parameters other than variations of the fundus optical absorption influence heat diffusion and temperature increases. Monitoring or individualizing the light dose in HRL therapy, or any similar infrared diode laser-based therapy will require more sophisticated technologies, including imaging the retina’s reflectance with an improved resolution, as well as refined methods to detect complex correlations between retinal damage and specific pathologies.
authors.affiliation: Swiss Federal Institute of Technology, Medical Photonics Group, SB-ISIC, Station 6, 1015 Lausanne, Switzerland.
authors.forename: Filippo
authors.initials: F
authors.lastname: Piffaretti
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Ballini
authors.forename: Roberto
authors.initials: R
authors.lastname: Perotti
authors.forename: Matthieu
authors.initials: M
authors.lastname: Zellweger
authors.forename: Edoardo
authors.initials: E
authors.lastname: Vezzola
authors.forename: Michel
authors.initials: M
authors.lastname: Sickenberg
authors.forename: Georges
authors.initials: G
authors.lastname: Wagnières
mesh_terms: D000328:Adult; D000368:Aged; D003941:Diagnostic Techniques, Ophthalmological; D005654:Fundus Oculi; D006801:Humans; D057446:Hydrodynamics; D007259:Infrared Rays; D053685:Laser Therapy / Q000379:methods*; D054023:Lasers, Semiconductor / Q000627:therapeutic use; D008875:Middle Aged; D013508:Ophthalmologic Surgical Procedures / Q000379:methods*; D055620:Optical Phenomena; D012160:Retina / Q000473:pathology* / Q000601:surgery*; D012164:Retinal Diseases / Q000473:pathology / Q000601:surgery; D012171:Retinal Vessels / Q000473:pathology / Q000601:surgery; D055815:Young Adult