Quantitative Cornea Hypoesthesia and Neurotrophic Ulcer Severity and Visual Outcomes

Abstract

Purpose: : While the causes of neurotrophic keratopathy are legion, the diagnosis is by and large a clinical one with the occasional employment of qualitative measures of cornea sensitivity. Reports on quantitative measurements of cornea hypoesthesia (such as via the Cochet-Bonnet aesthesiometer) are scarce with the possible exception of cases of herpes zoster infections. It is also unknown whether the degree of cornea hypoesthesia is associated with the degree of cornea compromise and final visual outcome. Therefore, we sought to evaluate the degree of quantitative cornea hypoesthesia in cases of neurotrophic keratopathy secondary to any etiology seen at our institution as well as whether the measured cornea sensitivity is correlated or associated with the grade of cornea ulceration and final visual outcome.

Methods: : Patient records from 2006-2008 from our institution with the diagnosis of neurotrophic keratopathy were identified and reviewed in a retrospective fashion. Multiple parameters were extracted including cornea sensitivity as measured by the Cochet-Bonnet aesthesiometer, the etiology of the disease, the final visual outcome, and the ulcer grade (I through III). Statistical correlation analyses were then performed.

Results: : 46 eyes of 44 patients were identified. Of these, 20 eyes of 18 patients had their cornea sensations measured by the Cochet-Bonnet aesthesiometer. Multiple etiologies of neurotrophic keratopathy were represented including herpes simplex (5), diabetes mellitus (5), herpes zoster (4), neurosurgical sequelae (3), and local iatrogenic causes (3). The cornea sensations ranged from none to 3 mm. We find no association between the degree of cornea hypoesthesia and the grade of the neurotrophic ulcer (r_s = -0.20). We also did not find a correlation between cornea hypoesthesia and final visual outcome (r = -0.36).

Conclusions: : We find that a cornea sensitivity threshold of 3 mm as measured by the Cochet-Bonnet aesthesiometer is present in cases of neurotrophic ulceration. However, cornea sensation alone was not associated with the severity of the ulceration nor correlated with the final visual outcome. These last 2 observations likely represent our limited sample size as well as other variables such as ocular co-morbidities and treatment modalities which play important roles in the clinical manifestation of disease and outcome determination.

Keywords: cornea: clinical science • innervation: sensation • keratitis