Retinal thermal deformations measured with phase-sensitive optical coherence tomography in vivo

Area of Science:

• Ophthalmology
• Biomedical Optics
• Retinal Imaging

Background:

• Precise temperature control is crucial for safe and effective retinal laser therapy.
• Existing methods lack the precision to calibrate laser power for non-damaging, patient-specific treatments.
• Understanding thermal effects in the retina is key to preventing tissue damage.

Purpose of the Study:

• To demonstrate a method for in vivo temperature rise measurement in the retina using phase-sensitive optical coherence tomography (pOCT).
• To investigate the differences in thermal deformation patterns between healthy and degenerate retinas.
• To explore the potential of pOCT-derived biomechanical data as a diagnostic tool for photoreceptor degeneration.

Main Methods:

• Utilized phase-sensitive optical coherence tomography (pOCT) to measure thermally induced optical path length changes (ΔOPL) in vivo.
• Applied short (10-ms) laser pulses to induce controlled heating of the retina.
• Analyzed the spatial confinement of retinal deformations in response to laser-induced thermal expansion.

Main Results:

• Achieved temperature rise detection with a precision better than 1°C, sufficient for laser power calibration.
• Observed distinct differences in thermal deformation confinement between wild-type and degenerate rat retinas.
• Healthy retinas showed localized deformations between the RPE and photoreceptor inner segments, while degenerate retinas exhibited deeper penetration.

Conclusions:

• pOCT provides precise, in vivo measurement of retinal temperature changes during laser therapy.
• Differences in thermal deformation patterns suggest a structural damping mechanism in healthy photoreceptors, potentially involving the connecting cilium.
• The distinct biomechanical response of healthy versus degenerate retinas offers a novel diagnostic approach for photoreceptor degeneration.