Abstract
Purpose: :
Anterior ischemic optic neuropathy (AION) is due to ischemia of the optic nerve head, leading to significant vision loss. Sub-retinal fluid has been reported in about 10% of patients. Using a murine model of induced AION, we investigate the presence and methods of detection of such sub-retinal fluid in mice.
Methods: :
AION was induced in eight mice using a photochemical thrombosis model. In vivo quantification was performed with spectral domain optical coherence tomography (SD-OCT) on 8 adult C57BL/6 mice one day following AION using the ring scan vs. volume scan mode to assess the frequency of sub-retinal fluid following acute AION. The ring scan consisted of diameter of 12 deg, and the volume scan included 25 horizontal B-scans spanning a 15°x15° area centered on the disc.
Results: :
Within one day after experimental AION, there was optic nerve head edema on histology and staining of the disc on fluorescein angiography. As measured by the ring scan mode on SD-OCT, there was significant swelling of the peripapillary retina following AION, with 30% increased in the inner retinal thickness (retinal nerve fiber layer + retinal ganglion cell layer + inner plexiform layer) (AION eyes: 100.1 ± 2.2 µm, control eyes: 77.2 ± 0.4 µm, P < 0.0001). On day one, ring scan of the peripapillary retina showed no evidence of sub-retinal fluid on SD-OCT. In contrast, volume scan of the optic disc revealed sub-retinal fluid in 100% of AION eyes. No sub-retinal fluid was seen in the contralateral control eyes with either scan mode.
Conclusions: :
While the ring scan mode of SD-OCT allowed measurement of the retinal nerve fiber layer, it underestimated the presence of sub-retinal fluid in acute AION. Volume scan significantly increased the sensitivity of detecting sub-retinal fluid. Based on the animal data, we now routinely perform retinal nerve fiber layer ring scan, volume scan, and macular scan to assess patients with acute AION and have found increased incidences of sub-retinal fluid.
Keywords: neuro-ophthalmology: optic nerve • optic disc • neuro-ophthalmology: diagnosis