Purpose To evaluate tear neuropeptides (NPs) (vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), substance P (SP), nerve growth factor (NGF)) in chronic ocular topical hypotensive therapy with and without benzalkonium chloride (BAK) preservative.
Methods A comparative, open label, cross-sectional study of patients using antiglaucoma medications for >6 months with BAK (group I), without BAK (group II) and controls was done. Tear NPs (ELISA), ocular surface evaluation tests (tear breakup time (TBUT), Schirmer’s test, corneal and conjunctival staining score) and confocal central corneal subbasal nerve fibre layer (SBNFL) imaging was done.
Results Of 153 eyes evaluated, group 1 (82 eyes (41 patients; mean age 48±14.5 years)) and group 2 (71 eyes (36 patients; mean age 43.11±15 years)) were on therapy for a mean duration of 10.05±2.0 and 9.67±2.3 months, respectively. Tear analysis showed elevated SP and NGF (p<0.01); decreased CGRP (p=0.03), VIP and NPY (p<0.01) compared with controls (n=30, mean age 29.33±5.7 years). Tear NP levels (SP (p=0.1), NGF (p=0.33), CGRP (p=1), VIP (p=0.87), NPY (p=0.83)) and SBNFL (p=0.09) were comparable in both groups. There was no correlation seen between tear NP levels and clinical tests and SBNFL.
Conclusion Our study analysis points towards altered tear NP levels in eyes on chronic topical hypotensive therapy in comparison with controls with no significant difference in tear NP levels and central corneal SBNFL density between the BAK preservative and BAK-free antiglaucoma therapy.
- substance p
- ocular surface
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Contributors VM contributed to the conception of the work, critical revision and accountable for all aspects of the work. VM, RD, MS and SV contributed to the analysis and interpretation of data for the work.
RD, MS, VG, TD and SV contributed to data acquisition. VG and TD contributed to the interpretation of data for the work. All authors contributed to the manuscript drafting and final approval of the version.
Funding This study was supported by Extramural Research Funding from the Indian Council of Medical Research (Project ID: 5/4/6/7/Oph/12-NCD-II).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval All India Institute of Medical Sciences Ethics Committee Institute Ethics Approval (Ref No:- IEC/NP-241/2012).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.