Findings from a study published in Optometry and Vision Science evaluated the clinical signs and symptoms of dry eye disease (DED) and their association with the severity of peripheral neuropathy in patients with type 2 diabetes (T2D).
Give me some background.
Peripheral neuropathy is a long-term debilitating complication of diabetes that affects at least 50 to 66% of all patients with diabetes mellitus.
Previous studies have proposed that a reduction in corneal nerves caused by peripheral neuropathy leads to disruption in ocular surface homeostasis that potentially contributes to the pathophysiology of DED.
Now talk about the study.
In this prospective cross-sectional study, investigators recruited 63 participants with T2D and performed detailed assessments of DED using:
- Dry eye questionnaires (Ocular Surface Disease Index [OSDI], Dry Eye Questionnaire-5 [DEQ-5])
- Tear osmolarity
- Lipid layer thickness
- Noninvasive keratographic tear breakup time (NIKTBUT)
- Phenol red thread test (PRT)
- Ocular surface staining
What else?
Corneal nerve morphology was imaged using corneal confocal microscopy.
Then: By using the Total Neuropathy Scale, participants were stratified into two neuropathy groups:
- No/mild neuropathy (n = 48 [76%])
- Moderate/severe neuropathy (n = 15 [24%])
Findings?
In total, DED was diagnosed in 31 participants (50%) of the cohort.
The odds of developing DED in the moderate/severe neuropathy group were four times higher compared to the no/mild neuropathy group (95% confidence interval [CI] 1.10-13.80, p = 0.030).
In the moderate/severe neuropathy group, 11 participants (73%) were diagnosed with signs and symptoms of dry eye compared to 20 patients (42%) in the no/mild neuropathy group.
How did DED diagnostics differ between groups?
To take this comparison further, in the moderate/severe neuropathy group:
- DEQ-5 scores were significantly higher (p = 0.020)
- PRT values (p = 0.048) were significantly reduced
- Corneal nerve fiber length (p < 0.001) was significantly reduced
The OSDI questionnaire scores and NIKBUT measurements showed no significant difference between both groups.
Anything else?
Neuropathy scores were independently associated with PRT measurements and nerve fiber length while adjusting for age, gender, hemoglobin A1c, and duration of diabetes in regression analyses.
- Meaning: This strongly suggests a connection between diabetic peripheral neuropathy and both lacrimal hyposecretion (i.e., dry eye) and corneal nerve loss.
Take home.
These findings suggest that T2D patients with peripheral neuropathy have a higher risk of developing DED, which further increases the severity of neuropathy.
The observation that worsening peripheral neuropathy is associated with reduced tear secretion suggests that it may contribute to aqueous insufficiency.
Further, the lack of correlation between DED symptom severity and corneal nerve loss indicates that these patients are often asymptomatic—potentially due to compromised corneal sensitivity.
Next steps?
Future studies could include longitudinal assessments of corneal nerve and ocular surface health with more diversified sample sizes in conjunction with novel neurotrophic treatments.