[Corneal sensitivity in patients treated medically for glaucoma or ocular hypertension].

PURPOSE

To evaluate the corneal sensitivity in patients treated with intraocular pressure (IOP)-lowering medications.

INTRODUCTION

Chronic administration of anti-glaucoma drops is associated with numerous tissue changes on the ocular surface. The purpose of this study was to investigate the effect of these medications and their preservative, benzalkonium chloride (BAK), on corneal sensitivity.

PATIENTS AND METHODS

Thirty-nine patients treated for glaucoma or ocular hypertension (OHT) and nine untreated patients were included in this study. Treated patients were divided into three groups according to the daily number of preserved eyedrops (0, 1 and ≥2). Corneal sensitivity was assessed using the Cochet-Bonnet esthesiometer. All patients underwent a complete examination of the ocular surface including Schirmer testing, tear film breakup time (BUT) and corneal and conjunctival fluorescein staining. The Ocular Surface Disease Index (OSDI) questionnaire was used to evaluate symptoms.

RESULTS

Corneal sensitivity was 58.8±2.8mm, 56.2±5.2mm, 50.3±12.5mm and 44.3±13.6mm in untreated patients, in patients treated with none, one and two or more instillations of preserved eyedrops, respectively. Corneal sensitivity in patients treated with preserved eyedrops was significantly lower as compared to untreated patients (P<0.001) and patients treated with preservative-free eyedrops (P=0.012). Corneal sensitivity of patients treated with intraocular pressure-lowering medications was negatively correlated to the number of instillations of preserved eyedrops (r=-0.390 ; P<0.001) as well as to the duration of treatment (R=-0.357 ; P=0.001). BUT and fluorescein staining were significantly altered in treated patients compared to the untreated control group ; however, no significant difference was observed between the treated groups. There was no significant difference for OSDI or Schirmer testing between the various groups.

CONCLUSION

Chronic administration of BAK-containing anti-glaucoma eyedrops appears to alter corneal sensitivity. These results could explain the absence of correlation between clinical signs and symptoms sometimes observed in patients treated for glaucoma or OHT.