It is a randomised, double-blinded clinical trial in which consenting participants who meet the inclusion criteria would be randomised into 2 groups. Subjects will be given either preserved or preservative free latanoprost for a period of 12 weeks. The efficacy and tolerability of both drugs would be assessed every 4 weeks, amongst these patients.

Ethical approval has been obtained from the Health Research Ethics Committee of Lagos University Teaching Hospital.

Patients will be recruited from the weekly glaucoma clinic, Monday, Thursday, and Friday general clinics. Each participant would be seen for a period of 12 weeks; at baseline visit, and weeks 4, 8 and 12, in which topical, label-masked preserved or preservative free latanoprost would be dispensed, with patient instructed to instill one drop of 0.005% latanoprost by 9:00pm (± 1 hour). Efficacy of the two eye drops will be assessed by measuring the intraocular pressure 3 times a day at every visit. Safety and potential adverse effects of the drops will be evaluated in terms of ocular symptoms and tear parameters. Ocular symptom values of the patients will be evaluated.

All patients will undergo ocular examinations, including visual acuity assessment, slit lamp biomicroscopy, intraocular pressure, tear film breakup time (TBUT), fluorescein staining, schirmer test, gonioscopy, standard automated perimetry, and ophthalmoscopy. Tolerability will be evaluated with the frequency and percentage of distributions of severity level using the OSDI questionnaire in each group after administration at weeks 4 and 12, respectively. The symptoms checked during follow-up visits will include; pruritus, burning/stinging, blurred vision, tearing, sticky eye sensation, eye dryness sensation, and foreign body sensation. Quality of life would be evaluated at baseline visit and at week 12, using the standard quality of life Q-15 questionnaire.

A research team would be involved in carrying out this research, Comprising the principal researcher, a pharmacist, and 2 ophthalmic nurses. Results will be collated and analysed by the principal researcher. The entire research would be carried out over a period of 9 months, from December 2022 to August 2023.

Inclusion Criteria:

• Recently diagnosed, consenting high tension, primary open angle glaucoma or ocular hypertensive patients.
• Forty years and above.
• Intraocular pressure of 21- 30mmHg (millimetres of mercury)
• Willingness to participate in the study.

Exclusion Criteria:

• Patients under 40 years of age.
• Diabetic patients
• Patients on other anti- glaucoma medications.
• Patients on topical immunosuppressive medication.
• Patients on anti-depressants.
• Patients who have had any form of ocular surgery or intervention such as cryotherapy.
• Patients using contact lens.
• Patients on any form of topical medication in the last 1 month.
• Patients diagnosed or suspected to have Sjogren syndrome.
• Patients being managed for Steven-Johnson's syndrome, ocular cicatricial pemphigoid.
• Pregnant patients.
• Previous glaucoma surgery and any refractive surgery <12 month prior to enrolment.
• Only eye patients.

Both preserved and preservative-free drugs would be masked from the patient and the principal researcher. The pharmacist would remove actual labels, and mask them with new labels, coded ''X'' and ''Y'' latanoprost 0.005%, representing either preserved or preservative free medications, known to only the pharmacist.