To investigate if the Eye Drop Guide more effective than carefully instructed routine technique for chronic glaucoma patients to self-instill eye drops.

And what factors are associated with the failure of self-instillation eye drops with the Eye Drop Guide?

The participants are randomized into 2 groups. For group I; the participants will be instructed to use the Eye Drop Guide first while for group II; the participants will be instructed to use the routine self-instillation technique first. The instruction will be given to all participants by the same investigator. The participants are allowed to practice until confidence in the techniques to which they are assigned. The participants then are instructed to use only that technique to instill eye drops in both eyes every day and keep the diary to document the date, time of practice, and number of bottles use in each eye for practice at home. The investigators make a telephone visit at 1 week to remind the practice routine and the follow up schedule. The 2 week follow up will be scheduled to evaluate the self-instillation performance using the techniques to which they are assigned by the VDO recordings under the same setting as Day 1.

After VDO recordings the participants will be switched to receive the other technique with the same instruction as the other group. Allow the same period of practice in the hospital and at home. The investigators again will make a 1-week telephone visit and 2-week follow up after self-practice at home. At week 4 the VDO recordings of self-instillation performance will be taken again under the same setting as previous records.

Inclusion Criteria:

• Have been diagnosed of chronic glaucoma for 3 months or longer
• Age of 18 years or over
• Self-administer eye drops regularly

Exclusion Criteria:

• Perioperative patients
• Patients who were blind from other diseases
• Patients with ophthalmic conditions that affect the eye drop instillation e.g. nystagmus, ptosis, exophthalmos, enophthalmos, microphthalmos, symblepharon, restrictive ophthalmoplegia
• Patients whose underlying conditions would affect the patient's adherence to the protocol e.g. dementia, psychosis, mental retardation, neurological conditions resulting in tremor or paralysis, rheumatoid arthritis, hand deformities
• Patients who are allergic to artificial tears eye drop
• Patients who are not able to return for the follow-up schedule