Orbital Fat Volume After Treatment with Topical Prostaglandin Agonists

Abstract

Topical prostaglandin analogs (PGAs) are common treatment for primary openangle glaucoma (POAG) but reportedly may cause adnexal fat atrophy. We asked if patients with POAG treated with PGAs have abnormalities in orbital fat volume (OFV). METHODS. We studied 23 subjects with POAG who had never experienced intraocular pressure (IOP) exceeding 21 mm Hg and were treated long term with PGAs, in comparison with 21 age-matched controls. Orbital volume, non-fat orbital tissue volume, and OFV were measured using high-resolution magnetic resonance imaging. RESULTS. Subjects with POAG had been treated with PGAs for 39 ± 19 months (SD) and were all treated within the 4 months preceding study. In the region from trochlea to orbital apex, OFV in POAG was significantly less at 9.8 ± 1.9 mL than in the control subjects at 11.1 ± 1.3 mL (P = 0.019). However, between the globe-optic nerve junction (GONJ) and trochlea, OFV was similar in both groups. Width and cross sectional area of the bony orbit were significantly smaller in POAG than in controls (P < 0.0001). Posterior to the GONJ, the average orbital cross-sectional area was 68.2 mm 2 smaller, and the orbital width averaged 1.5 mm smaller throughout the orbit, in patients with POAG than in controls. CONCLUSIONS. Patients with POAG who have been treated with PGAs have lower overall OFV than controls, but OFV in the anterior orbit is similar in both groups. Lower overall OFV in POAG may be a primary association of this disorder with a horizontally narrower bony orbit, which may be a risk factor for POAG at nonelevated IOPs.

Adduction-Induced Strain on the Optic Nerve in Primary Open Angle Glaucoma at Normal Intraocular Pressure

“…We did not exclude subjects who had been treated for IOP reduction with topical prostaglandin agonists, since nearly all patients with POAG are treated as first-line therapy with these drugs. We have shown that topical prostaglandin agonists do not alter anterior orbital fat in the regions exposed to these drugs 20 and multivariate analysis has not demonstrated a statistical effect of exposure to these drugs on globe retraction during adduction tethering. 5 We only selected for analysis all subjects who underwent target-controlled MRI in central gaze and smaller and larger angles of adduction who demonstrated minimal ON redundancy (path length <102.5% over minimum straight-line path) in both adduction positions.…”