Retinal Hydration Assessment With Optical Coherence Tomography: Unraveling Its Significance in Retinal Fluid Dynamics, Macular Edema and Cell Viability.

PURPOSE

The purpose of this study was to quantify retinal hydration (RH) levels with optical coherence tomography (OCT) and determine the extent of cellular damage resulting from intraretinal fluid alterations.

METHODS

We took 6.0 mm sections of the human sensory retina that were excised from 18 fresh (<24 hours) donor eyes. They were either exposed to various osmotic stresses between 90 and 305 mOsm or dehydrated under a laminar flow hood. Change in tissue weight was used to calculate the retinal water content (RWC). Image analyses were conducted on OCT between 0 and 180 minutes to assess retinal thickness (RT) and "optically empty areas" (OEAs) representing intraretinal fluid. Correlations were sought among RWC, OEA, RWC, and RT. The effect of RH on retinal cell viability (RCV) was assessed with the Live-Dead Assay.

RESULTS

RH demonstrated a stronger correlation with the OEA than plain RT measurements (r = 0.99, P < 0.001). RH-RCV interaction fits well to a bell-shaped curve. A significant proportion of retinal cells (>80%) remained viable despite the change in RH ranging between 0.87 and 1.42 times. This "safe zone" was found to be associated with a 22% increase in OEA (r = 0.99, P < 0.01).

CONCLUSIONS

OCT has been demonstrated as a valuable tool for assessing RH and can be used for intraretinal fluid content analysis. RH is a better indicator of RCV compared with RT. Computing RH may improve the determination of functional outcome of intravitreal pharmacotherapeutics used for diabetic macular edema and exudative age-related macular degeneration.

TRANSLATIONAL RELEVANCE

We link basic research and clinical care by assessing retinal hydration's impact on retinal fluid dynamics, macular edema, and cell viability.