study the effect of different concentrations of benzalkonium chloride on the ocular surface of non-dry-eyed patients post cataract surgery.

60 eyes of will be included in this study.

• 20 eyes will receive regular Tobradex 0.1mg/ml BAK 5 times per day (Group 1).
• 20 eyes will receive Dexathalm multidose 0.05mg/ml BAK 5 times per day (Group 2).
• 20 eyes will receive single dose unit Dexathalm NO BAK 5 times per day (Group 3).

Preoperative assessment:

All selected patients will receive thorough explanation of the study design and aims, an informed consent will be obtained from all patients.

Tear break up time (TBUT) will be measured non-invasively by Ocular Surface analyzer.

Ocular Surface disease index will be calculated by filling a questionnaire. 12-item questionnaire provide a rapid assessment of the symptoms of ocular irritation consistent with dry eye disease and their impact on vision-related functioning.

Postoperative:

1. All patients will be examined at day1, 1 week and 3 week postoperative.
2. At 3 weeks re-evaluate I. TBUT by non-invasive ocular surface analyzer II. OSDI by filling the questionnaire.

Inclusion Criteria:

• Patients undergoing uncomplicated cataract surgery
• Cataract grade: (LOCSIII): NO2NC2,C3,P2

Exclusion Criteria:

Preoperative non-invasive TBUT<10 seconds. Patients who have rheumatoid arthritis or autoimmune diseases affecting corneal surface.

Involutional entropion or ectropion preoperative Postoperative significant corneal edema requiring medication.