This is a prospective, multi-centre, cross sectional observational study to determine the prevalence of ocular surface disease (OSD) in glaucoma patients, nationwide. The study also analyses sub group of OSD prevalence, stratified according to the treatment types (i.e. preserved, preservative-free, and combination of preservative-free and preserved eyedrops), and illustrates the patient perspective on OSD.

For this prospective, multi-centre, cross sectional observational study, patients who attend routine eye examination at the medical institutions and who have been diagnosed with primary open-angle glaucoma, primary angle-closure glaucoma, pseudoexfoliation glaucoma, pigment dispersion glaucoma or ocular hypertension will be studied. The medical institutions are selected across different regions of Malaysia to assess the nationwide prevalence of OSD in glaucoma patients. The routine assessments include Corneal Evaluation, Tear Break-Up Time (TBUT), Hyperemia and Schirmer's test whereby the data from these assessments will be collected and analyzed. The study will also includes Symptom Evaluation and Questionnaire feedback.

Inclusion Criteria:

• 1) Age of 21 years or older and those who can provide informed consent.
• 2) On anti-glaucoma medications for >6 months
• 3) IOP ≤ 21 mm Hg in the study eye at the screening examination (under treatment)
• 4) If only one eye is eligible, it is to be evaluated. If both eyes are eligible, then the eye with a higher NEI score will be selected for evaluation.
• 5) A best-corrected visual acuity score of 6/36 on the Snellen Chart, or better in each eye.

Exclusion Criteria:

• 1) Those with secondary ocular hypertension or glaucoma
• 2) Those with severe visual field disorder (mean deviation of 20 dB or worse)
• 3) Those with a history of ocular surgeries (intraocular surgery including ocular laser treatment which may affect the patient's ocular surface condition) within 6 months prior to the study initiation.
• 4) Those with a history of glaucoma surgery
• 5) Those with a history of corneal refractive surgery
• 6) Those with severe dry eye associated with systemic disorders, or in need of drugs to treat dry eye
• 7) Those with ocular allergy, ocular infection or ocular inflammation
• 8) Those using eye drops for other ocular comorbidities
• 9) Those who need to use systemic or ophthalmic steroids (excluding topical skin steroidal ointment)
• 10) Female patients who are pregnant, nursing or lactating
• 11) Those who use contact lenses
• 12) Any corneal abnormality or other corneal comorbidity condition preventing reliable applanation tonometry
• 13) Those on oral antihistamine, antipsychotic or anti-depressant drugs.

Patients who attend routine eye examination at the medical institutions will be studied. The medical institutions are selected across different regions of Malaysia to assess the nationwide prevalence of OSD in glaucoma patients.

To be confirmed