Selective Laser Trabeculoplasty (SLT) is a glaucoma treatment that has been shown to effectively lower intraocular pressure by increasing aqueous outflow through macrophage recruitment. There is evidence of increased drainage in the nasal quadrants of the eye. This study aims to compare whether there is a difference in the reduction of eye pressure when SLT is performed nasally and temporally.

This study aims to evaluate if there is a difference between 180 degree nasal and temporal selective laser trabeculoplasty (SLT) in treatment outcomes. It is known that there is increased aqueous collectors and veins and thus aqueous drainage in the nasal quadrants of the eye. If SLT works by the hypothesized biologic mechanism in which macrophages remodel the aqueous drainage system to increase outflow, performing SLT in an area concentrated with aqueous veins may increase outflow more. As a result, we hypothesize that nasal 180 degree SLT may have better outcomes compared to the temporal counterpart. The results of this study may help inform decisions when performing 180 degree SLT and provide insight to SLT's mechanism of action. The primary objective of this study is to determine if there is a difference in treatment efficacy between nasal and temporal 180 degree SLT by measuring differences in baseline and post-operative intraocular pressures. We hypothesize that nasal SLT will have superior outcomes compared to temporal SLT due to increased number of aqueous veins.

Inclusion Criteria:

• Diagnosis of open angle glaucoma, ocular hypertension, pigmentary dispersion syndrome and pseudoexfoliation syndrome
• Participant must be over 18 years of age
• IOP > 16mmHg on at least two consecutive occasions separated by one month
• Two sighted eyes with visual acuity of 20/200 or better
• Informed consent from patient

Exclusion Criteria:

• Diagnosis of secondary OAG (aside from pigmentary and pseudoexfoliation glaucoma) or narrow angle glaucoma
• Previous incisional glaucoma surgery
• Incisional glaucoma surgery scheduled within 1 year of intervention
• Corneal disease affecting visualization of anterior chamber of the eye
• Treatment or plan to treat with topical or systemic steroids
• Previous selective laser trabeculoplasty treatment

The patients will be recruited from the glaucoma practice at St. Joseph's Healthcare Hamilton. A baseline clinical eye examination will be completed to include or exclude the participant from the study according to the criteria below. The baseline exam will include a comprehensive questionnaire of the participant's past ocular history, relevant systemic diseases, glaucoma risk factors, and surgical history.