Re: “ISOPT Clinical Hot Topic Panel Discussion on Cornea Anterior Segment Disease” by Asbell et al. ( J Ocul Pharmacol Ther 2019;35(8):447–456)

Dear Editor,

A recent expert panel discussion ¹ considered the difficulties of confidently diagnosing differentially between neuropathic and evaporative tear dysfunction causes of dry eye symptoms. Rosenthal and Borsook noted that scleral lenses instantly and completely block precorneal tear evaporation thereby avoiding symptoms that result from the activation of dryness and coldness detecting sensitized low-threshold C mechanoreceptors. ² Rosenthal and Borsook suggested that such symptoms would have an evaporative basis. ² We have examined if eye closure would similarly reduce dry eye symptoms by blocking tear evaporation in patients with symptoms due to evaporative tear dysfunction. ³ We hypothesized that patients with a neuropathic (rather than an evaporative tear dysfunction) basis for their dry eye symptoms would not detect any symptom reduction with eye closure. The severity of symptoms reported by a series of 75 consecutive patients attending a dry eye clinic were examined before any other examination procedure. Without any prior blink-related instructions, the level of “eyes-open” symptoms being experienced at that time was recorded on a 100 mm visual analogue scale with anchor limits of extreme comfort and extreme pain. Patients were then instructed to keep their eyes gently closed for 10 s and to indicate their closed-eyes symptoms. A double normal range interblink interval of 10 s was deemed to be an adequate time for any significant change in symptoms to be assessed. Both responses were recorded on the same visual analogue scale to allow the relation between them to be more accurately specified. For example, patients wanting to indicate no change in symptoms with eye closure can do so very accurately when the same scale is used for both assessments.

Based on their diametrically opposed levels of symptom change, 2 contrasting response subgroups of 11 patients (A) and 9 patients (B) were compared. For group A there was a mean reduction in symptom level with eye closure of 79.9% ± 12.0% (designated as a suspect evaporative dry eye group that was supported by a mean Keratograph 5M tear breakup time of 2.2 ± 3.3 s). There was a mean symptom-level increase with eye closure of 6.6% ± 9.8% for group B (designated as a possibly neuropathic symptom group as suggested by a healthier mean tear break time of 7.6 ± 3.9 s and consistent with them not having an evaporative basis for their symptoms). The patients studied were mainly from the moderate to severe end of the dry eye symptom spectrum, which could have been a reason for finding 2 diametrically opposed groups. Those not included in groups A and B were presumed to have less severe evaporative dry eye symptoms that may or may not have been associated with some degree of neuropathic symptoms. Such patients appear to be less classifiable by an evaluation of symptom change with eye closure. Nevertheless, these findings suggest that simple open versus closed-eye assessments for any related symptom changes can be another means of screening for patients who appear to have symptoms that are either predominantly due to evaporative tear dysfunction or that are predominantly neuropathic in nature.