Published in Research

Decreased corneal sensitivity may be indicative of PDR

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4 min read

A new study from the American Journal of Ophthalmology found that patients with proliferative diabetic retinopathy (PDR) had reduced corneal sensitivity compared to patients with non-proliferative diabetic retinopathy (NPDR).

Give me some background first.

Diabetic retinopathy (DR) is a leading cause of blindness globally, and diabetic keratopathy (DK) is a common complication of diabetes mellitus; however, the relationship between DR and DK has not been fully explained in the past.

Previous studies of ocular complications in diabetes patients have explored these conditions in homogenous populations, note the study authors, and might not apply to all racial and ethnic groups.

Now talk about the study.

When evaluating 100 eyes of 50 patients, 66% of whom self-identified as Hispanic or Latino, and 8% of whom identified as Black or African American, were recruited for the study from a private retinal practice in Texas.

Severity of DR was assessed using the Diabetic Retinopathy Severity Scale (DRSS) score.

Hold up, what exactly is DRSS?

For context, the Early Treatment Diabetic Retinopathy Study (ETDRS) scale can be further subdivided and quantified by disease characteristics. Non-proliferative diabetic retinopathy (NPDR) is classified as none (0-10), mild (10-30), moderate (30-47), moderately severe (47-51), and severe (51-60) while proliferative diabetic retinopathy (PDR) is classified as mild (60-64), moderate (65-70) and high risk (70-100).

Patient criteria?

Patients were all adults with diabetes mellitus type 1 or 2 and present DR (DRSS >3). The following were the exclusion criteria:

  • Vitrectomy
  • Cornea, eyelid, glaucoma, or retina surgery
  • NK or other cranial nerve V pathology
  • Ocular herpes simplex virus (HSV) infection or herpes zoster ophthalmicus (HZO)
  • Ocular chemical trauma
  • Corneal dystrophies
  • Pan-retinal photocoagulation (PRP)
  • Cataract surgery within the preceding 3 months

Patients’ corneal sensitivity was assessed using the Cochet-Bonnet esthesiometer, followed by slit-lamp examination, dilated fundoscopic examination, and retinal imaging with OCT and a fundus camera.

To note, if the patient had active Stage 2 to 3 neurotrophic keratitis (NK) at the time of screening, they were excluded from the study.


Patients with PDR (DRSS score >60) had “significantly” decreased corneal sensitivity compared to those with NPDR (DRSS score <60). Further, eyes with PDR were more likely to suffer from a greater magnitude and degree of corneal sensitivity loss in all four quadrants compared to those eyes with NPDR.

Go on…

The study authors further note a high rate of comorbidity between DK and DR, and suggest that corneal sensitivity testing be added to the list of screening tests for DR.

They also observed that the use of anti- vascular endothelial growth factor (VEGF) did not reverse neural impairment after administration in the study population.

Take home.

“Screening of diabetic patients for early evidence of decreased corneal sensation presents a potential opportunity to develop and implement therapeutic interventions to prevent progression to NK and associated vision loss,” note the authors in the final summary.

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