Neuropathic pain: Etiology, pathophysiology, mechanisms, and evaluations

Abstract

To illustrate that ocular pain may occur in patients with neurotrophic keratopathy (NK) that typically are thought to lack symptoms of discomfort, and that aa subset of these patients may also present with neuropathic corneal pain (NCP).Retrospective Case series of 7 stage 1 NK patients who presented with concurrent ocular pain, as confirmed by clinical examination, proparacaine challenge test, and in vivo corneal confocal microscopy (IVCM). Records were assessed for results of ocular surface disease index (OSDI), pain on visual analog scale (VAS), ocular pain assessment survey (OPAS), best-corrected visual acuity (BCVA), corneal fluorescein staining (CFS) score, and IVCM findings. IVCM findings were compared to that of 20 healthy reference controls.Mean age of patients was 63.7 ± 11.6 (range 44–76) years and 56.9 ± 8.6 (range 42–74) years in reference controls (p = 0.11). At presentation, ocular discomfort was 8.0 ± 1.3 (range 7–10) on VAS and mean OSDI scores were 72.26 ± 6.81 (range 62.50–79.54). Mean BCVA was 20/40, and mean CFS scores were 3.43 ± 0.79 (range 2–4) on the Oxford scale. IVCM analysis showed significant decrease in mean total, main and branch nerve densities in ranges consistent with NK as compared to normal controls (p < 0.001 for all), increased dendritiform cell density in three patients (p < 0.001), and the presence of microneuromas in six of the patients.Patients with NK are thought to present with hypoesthesia. However, nerve damage and inflammation, which play a role in the development of NK may result in the development of chronic ocular pain, such as NCP, resulting in potential underdiagnosis of either disease.