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Ahmad Kheirkhah, Thomas H Dohlman, Francisco Amparo, Michael A Arnoldner, Yureeda Qazi, Arsia Jamali, Pedram Hamrah, Reza Dana; Effects of Corneal Nerve Density on the Response to Treatment in Dry Eye Disease. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3648.
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Corneal nerves, which play a critical role in maintaining corneal epithelial health, may be diminished in dry eye disease (DED). We hypothesized that variability in patients’ responses to dry eye therapy may, in part, be due to different levels of corneal nerve density. Thus, this study aimed to evaluate whether levels of corneal subbasal nerve fiber length (SNFL) before DED treatment could prognosticate the level of improvement in signs and symptoms after treatment.
This double-masked clinical trial included 37 patients with DED and 27 age-matched controls. Patients with DED were randomized to receive either loteprednol 0.5% suspension (Lotemax®) or artificial tears (AT), both twice daily for 4 weeks. At baseline, in vivo confocal microscopy (Heidelberg Retina Tomograph 3/ Rostock Cornea Module) of the central cornea was performed in both eyes of all subjects. Corneal SNFL was measured by two masked observers using NeuronJ software. Patients with DED were divided into 2 subgroups, those with low baseline SNFL and those with near-normal baseline SNFL, with the cut-off point defined as “mean minus 2 standard deviations” of SNFL of controls. Clinical signs and symptoms were assessed at baseline and after 4 weeks for all therapeutic groups and compared between subgroups with low and near-normal SNFL.
In patients with DED, SNFL (17.07 ± 6.62 mm/mm2) was significantly lower than in controls (23.33 ± 3.25, P=0.001). In the loteprednol group, although no significant improvement in any sign or symptom was noted in patients with low SNFL (<16.84 mm/mm2), subjects with near-normal SNFL (≥16.84 mm/mm2) showed significant improvement in both symptoms (P=0.04) and corneal fluorescein staining (CFS, P=0.008). Among the AT group, while cases with low SNFL (<16.84 mm/mm2) showed no significant change in any sign or symptom, subjects with near-normal SNFL (≥16.84 mm/mm2) demonstrated significant improvement in symptoms (P=0.01) and CFS (P=0.006).
Significant improvement of clinical signs and symptoms after DED treatment was evident only in the group with near-normal corneal SNFL. Consideration of corneal subbasal nerve density may thus assist in explaining the variability of patients’ responses to DED therapy. In addition, subject segmentation based on corneal nerve density may assist in improving predictability of response to therapy in DED clinical trials.
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