Optical Coherence Tomography of Optic Disc Swelling in Acute Primary Angle-Closure Glaucoma

Acute primary angle-closure glaucoma (APACG) is an ophthalmic emergency with poor outcome if initial recognition and treatment are delayed. Posterior segment signs are often difficult to detect owing to corneal edema, anterior chamber inflammation, cataract, and the use of miotics. Optical coherence tomography (OCT) is a noncontact, noninvasive imaging technology capable of obtaining high-resolution tomographic images of posterior segment ocular structures.¹ We report a case of optic disc swelling and branch retinal vein occlusion after APACG with imaging performed with OCT and fluorescein angiography. We discuss the disc appearance on OCT imaging and a finding of a partial thrombus in the venous circulation on fluorescein angiography.

A 64-year-old Chinese woman had pain, blurring of vision, and redness in the left eye for 5 days. She had no previous episodes of eye pain. Her visual acuity was 20/30 OD and hand motion OS with a left relative afferent pupillary defect and mid-dilated pupil. The left eye had conjunctival injection, corneal edema, and a shallow anterior chamber. The intraocular pressure (IOP) was 14 mm Hg OD and 54 mm Hg OS. Gonioscopy confirmed angle closure. The IOP was lowered with intravenous acetazolamide, topical timolol maleate, pilocarpine hydrochloride, and brimonidine tartrate. Topical steroids were administered. Six hours after initial examination, her IOP was 12 mm Hg.

The left cornea had cleared 12 hours after initial examination to allow a view of the left disc. This was swollen and hyperemic with peripapillary flame hemorrhages. The fundus was otherwise unremarkable. The IOP was 10 mm Hg OS. Bilateral laser peripheral iridotomy was performed. The OCT (OCT 3; Zeiss-Humphrey Systems, Dublin, Calif) of the left disc showed swelling with adjacent thickening of the retina in the papilla-macula region (Figure 1). The right disc showed no swelling.

One week later, the left disc was still swollen and hyperemic, with fluorescein angiography showing no central retinal vein occlusion. There was, however, a partial thrombus of the left superotemporal branch vein (Figure 2). One month later, the left disc was pale and cupped (0.7). The visual acuity was counting fingers OS.

Posterior segment pathologic findings reported after APACG include irreversible optic nerve damage, anterior ischemic optic neuropathy,² vitreous hemorrhage,³ and ocular decompression retinopathy.⁴ Optical coherence tomography is a diagnostic imaging tool that can perform micron resolution imaging in the eye.¹ Its high resolution permits the imaging of fine structures within the retina. In this report, OCT demonstrates that in APACG the retinal swelling involves all layers of the retina. The retinal thickness was observed to have decreased at 9 months (Figure 1) compared with initial examination. This finding could have been due to resolution of retinal swelling alone or in combination with loss of tissue. Unfortunately, no OCT retinal thickness measurements were obtained at the point of resolution of retinal swelling, which could then be used for comparison with the retinal thickness measurements at the same location 9 months after the attack of APACG. This may have demonstrated tissue losses at the posterior pole due to APACG, similar to those detected in primary open-angle glaucoma.⁵

Retinal circulatory disturbances such as central retinal vein occlusion have been described in APACG, but branch retinal vein occlusion is rare.³ The partial thrombus in the superotemporal branch vein was unexpected.

The mechanism of disc swelling and subsequent optic atrophy that occurred at 1 month could be due to marked ischemia that occurred from compression of vessels in the prelaminar region during the prolonged period of increased IOP.⁶ The resulting anoxia led to edema. With reduction in optic nerve head blood flow, there was irreversible ischemic damage to the axons. An alternative explanation is disc swelling due to blockade of rapid axonal transport during the prolonged period of increased IOP. The ganglion cells were unable to tolerate the severe blockade of transport, and axon death occurred.⁷ The presence of disc swelling at initial examination may be a prognostic marker for visual outcome, although to our knowledge this has not been reported in the literature.

Correspondence: Dr Yip, The Eye Institute, National Healthcare Group, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Republic of Singapore (leonard_yip@ttsh.com.sg).

Financial Disclosure: None.