Simultaneous Assessment of Vascular Responses and Oxygen Saturation Changes to Hypercapnia in Diabetic Mouse Retinas Using Dual-Color Optical Coherence Tomography

Abstract

Purpose : Impaired retinal vascular response to physiological stimuli may serve as an early indicator of blinding diseases such as diabetic retinopathy. We hypothesize that integrating near infrared (NIR) optical coherence tomography angiography (OCTA) with visible light OCT (vis-OCT) measurements could yield insights into retinal hemodynamic reactions to hypercapnia.

Methods : Our dual-color SD-OCT integrates a NIR-OCT at ~850 nm (~2.9 mm axial resolution in tissue and ~97 dB sensitivity) and a vis-OCT at ~580 nm (~2.5 mm axial resolution in tissue and ~87 dB sensitivity). Healthy adult mice and their diabetic littermates (db/m vs. db/db) were imaged before and after a 10 min challenge with inhaled 2 L/min 5% CO₂. Timelapse measurements were initiated at the pre-stimulation baseline and subsequently recorded every 3 minutes from the start of the CO₂ challenge, continuing until 5 minutes post-challenge completion. Changes in vascular density and diameter were measured in first-order vessels of the superficial network using en face projections from OCTA and oxygen saturation (SO₂) changes were measured using vis-OCT.

Results : Co-registered cross-sectional and 3D images of the retina can be obtained using the integrated OCT system (Fig. 1a). In both healthy (db/m) and diabetic (db/db) mice (n =4 each), en face projections from OCTA enabled consistent visualization of the superficial retinal vascular network (Fig. 1b). In our pilot study, hypercapnia did not result in significant vasodilation in either group. However, a reduction in SO₂ was observed during hypercapnia using vis-OCT (Fig. 1c), highlighting the effectiveness of this imaging technique.

Conclusions : NIR and vis-OCT offer complementary insights into retinal hemodynamics, enabling non-invasive tracking of vasodilation and oxygenation changes in response to hypercapnia. This approach may be promising for early detection of the diminished vasodilatory response to hypercapnia often observed in diabetic retinopathy. Further research is warranted to explore the hemodynamic impacts of various vasodilatory stimuli to facilitate early diagnosis of the disease.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Fig. 1: (a) Co-registered NIR and vis-OCT cross-sectional images. En face OCTA projections (b) and SO₂ maps (c) comparing baseline and 4 min during hypercapnia in non-diabetic (db/m) and diabetic (db/db) mice.