Abstract: Corneal sensitivity & nerve morphology

Another verrrry nice study from one of my favorite journals. The background of this is: we know folks with dry eye tend to have decreased corneal sensitivity, but can we find evidence in the nerve morphology itself that explains it? And can we show a similar correlation in patients with or without dry eye?

Answer: Yes.

I also find it interesting that they would use glaucoma patients specifically as an ocular surface disease group (makes perfect sense on the basis that glaucoma patients have fried their eyes with BAK-preserved glaucoma drops, but admitting signals huge progress in ophthalmology).

Of course, our DEZ members will all want to know the answer to this conundrum: If my corneal sensitivity is DEcreased from dry eye disease, how come I hurt so dang much?!

The relationship between subbasal nerve morphology and corneal sensation in ocular surface disease.

Purpose: The purpose of this study is to evaluate the relationship between the in vivo confocal microscopic (IVCM) morphology of subbasal corneal nerves and corneal sensitivity in patients with ocular surface disease.
 Patients and methods: Ten healthy volunteers (control group), 12 patients with dry eye (dry eye group) and 14 patients treated with IOP-lowering topical medications (glaucoma group) were included. Central corneal sensation was measured using the contact Cochet-Bonnet esthesiometer. IVCM of the cornea was performed and the following subbasal corneal nerves parameters were analyzed: density, number, width, number of beadings, number of branching, tortuosity and reflectivity. One eye of each subject was included in the study.
 Results: Corneal sensitivity was significantly decreased in dry eye and glaucoma patients compared to controls. The density and number of subbasal corneal nerves were also significantly decreased in dry eye and glaucoma patients compared to controls. There was no difference in terms of subbasal nerve width, number of beadings, tortuosity, reflectivity and number of branching between the dry eye, the glaucoma, and the control groups. In all subjects, corneal sensitivity correlated positively with the density and number of subbasal nerves. However, in the dry eye group, corneal sensitivity correlated with the density and the number of nerves, while, in the glaucoma group, corneal sensitivity correlated only with the tortuosity of subbasal nerves.
 Conclusions: The relationship between corneal sensation and subbasal nerve morphology, as evaluated with IVCM, depends on the pathophysiological mechanism of ocular surface disease.

Invest Ophthalmol Vis Sci. 2012 Jun 13. [Epub ahead of print]

Labbe A, Alalwani H, Van Went C, Brasnu E, Georgescu D, Baudouin C.

Source

Department of Ophthalmology III, Quinze-Vingts National Eye Center, 28 rue de Charenton, Paris, 75012, France.