Hearing loss is generally considered in relation to the auditory system, including cochlear dysfunction, sensory hair-cell injury, neural degeneration, aging, noise exposure, and ototoxicity. This framework is clinically appropriate; however, cochlear function also depends on the integrity of the local microcirculation. The stria vascularis requires tightly regulated blood flow, oxygen delivery, and ion transport to maintain the electrochemical environment necessary for hearing. Disturbances in this vascular system may therefore contribute to auditory dysfunction.
Against this background, this study examined whether retinal vascular architecture was associated with hearing acuity in a health checkup population.
The retina cannot be regarded as a surrogate for the cochlea, because the two organs differ substantially in both anatomy and function. Nevertheless, each contains a microvascular network that may be influenced by systemic vascular and metabolic conditions. Retinal vessels can be visualized and quantified noninvasively, whereas cochlear microvessels cannot be assessed directly in routine clinical settings. Retinal imaging may thus provide a practical means of examining the broader microvascular context in which hearing loss develops.
Looking beyond vessel caliber
Earlier population-based studies reported associations between retinal microvascular abnormalities and hearing impairment. Most of these investigations focused on individual vessel measures, such as retinal arteriolar caliber, venular caliber, and the arteriolar-to-venular ratio. Although informative, these indices do not fully characterize the branching structure of the retinal vascular network.
Retinal vascular fractal dimension (FD) was therefore evaluated in the present study. FD quantifies the complexity and density of vascular branching across the retinal network. Higher FD values generally correspond to a denser and more complex branching pattern, whereas lower values indicate reduced vascular complexity. In this respect, FD provides a broader description of retinal vascular architecture than isolated vessel-caliber measurements.
Nonmydriatic fundus photography and pure-tone audiometry, which are both routinely performed in health checkup settings, were evaluated together. Retinal photographs were analyzed using Singapore I Vessel Assessment software, and hearing thresholds were measured by standardized air-conduction audiometry. This approach permitted the associations between retinal FD, hearing thresholds at several frequencies, and the high Fletcher index to be assessed within the same analytical framework.
Associations after adjustment for demographic and cardiometabolic factors
The cross-sectional analysis included 575 participants. Higher arteriolar FD, venular FD, and total FD were associated with lower hearing thresholds, which correspond to better hearing acuity.
After adjustment for age, sex, smoking status, alcohol consumption, hypertension, coronary heart disease, diabetes, and hyperlipidemia, each 1-standard-deviation increase in arteriolar FD was associated with a 2.85-dB lower hearing threshold at 1 kHz. Each 1-standard-deviation increase in venular FD was associated with a 2.61-dB lower hearing threshold at 2 kHz. Corresponding associations were also observed for the high Fletcher index, which reflects hearing sensitivity within the speech-frequency range.
Age required particular consideration because both hearing thresholds and retinal vascular measures vary with advancing age. The associations between FD and hearing outcomes remained after adjustment for age and other cardiometabolic covariates. This finding does not exclude residual confounding, but it indicates that age alone was unlikely to explain the observed relationships.
The restricted cubic spline analyses were consistent with the regression results. As FD increased, estimated hearing thresholds decreased. The effect estimates were modest and should be interpreted accordingly. Retinal imaging cannot diagnose hearing loss, and the present findings do not support the use of retinal FD as an independent screening measure. Rather, they indicate that retinal vascular architecture may be associated with hearing acuity within a broader systemic vascular context.
A biologically plausible but unproven vascular link
The cochlea is metabolically active and relies on the appropriate regulation of blood flow, oxygen delivery, and ion transport. Microvascular dysfunction may compromise the blood-labyrinth barrier, disrupt cochlear homeostasis, and impair sensory hair-cell function. Related vascular processes may also influence the retinal circulation.
Reduced retinal FD should not be interpreted as direct evidence of impaired cochlear perfusion. It may instead represent a marker of a broader systemic microvascular phenotype that is relevant to both retinal and cochlear tissues. A less complex retinal vascular network may reflect vascular aging, endothelial dysfunction, or metabolic injury, each of which may also be associated with auditory decline.
This interpretation is consistent with previous evidence linking retinal microvascular changes to cardiovascular disease, diabetes, and sleep-disordered breathing. It also raises questions regarding endothelial function, pericyte-mediated regulation of local blood flow, and the effect of metabolic disease on cochlear vascular homeostasis. These mechanisms were not examined directly in the present study and require dedicated longitudinal and experimental research.
What remains unresolved
Because the study was retrospective and cross-sectional, neither temporal sequence nor causality can be inferred. It remains uncertain whether alterations in retinal vascular structure precede hearing loss, arise from shared risk factors, or develop concurrently with auditory decline.
Residual confounding from physical activity, nutritional status, medication use, and unmeasured lifetime noise exposure may also remain. In addition, bone-conduction audiometry was unavailable; therefore, sensorineural and conductive components of hearing loss could not be differentiated. These limitations should temper the clinical interpretation of the findings.
Prospective studies with repeated retinal imaging and audiometric assessment are required to determine whether changes in retinal FD precede subsequent hearing decline. Future research should incorporate bone-conduction testing, detailed noise-exposure histories, and more complete characterization of cardiometabolic risk. Retinal capillary imaging with optical coherence tomography angiography may also clarify whether specific microvascular features are associated with auditory outcomes.
The principal message is not that the eye can diagnose disease of the ear. Hearing loss may instead need to be considered within a wider systemic framework in which vascular health is relevant. The retina provides a noninvasive and quantifiable view of the microcirculation, and the present findings indicate that retinal vascular fractal patterns are associated with hearing acuity in a health checkup population. Whether these measures have prognostic value should be established in future longitudinal studies.
This post is based on: Xu R, Qi X, Li Y, Bian X, Zhang X, Wang J, Chen T, Meng X. Association between retinal vascular fractal dimension and hearing loss: a cross-sectional study. Scientific Reports. 2025;15:30425. https://doi.org/10.1038/s41598-025-16451-1