Transient Monocular Vision Loss on Awakening: A Benign Amaurotic Phenomenon

Transient Bilateral Central Scotoma on Awakening: A Distinct Phenomenon

BACKGROUND

Transient vision loss can be an alarming symptom owing to potentially serious etiologies such as thromboembolism or giant cell arteritis. Transient monocular vision loss (TVML) on awakening has been recently described as a benign phenomenon (Bouffard et al, 2017). Our objective was to describe the unique phenomenon of transient binocular vision loss (TBVL) on awakening.

METHODS

Retrospective observational case series of 5 patients who experienced TBVL on awakening seen in the neuro-ophthalmology clinic at the Mayo Clinic between 2016 and 2020. Patients who described generalized blurred vision and those with monocular transient vision loss were excluded.

RESULTS

The median age was 81.4 years (range, 68-92 years), and all were male. Every patient described a stereotyped transient bilateral central scotoma on awakening with slightly irregular borders and mild asymmetry between the 2 eyes lasting between 15 and 90 minutes. Frequency ranged from 3 to 7 times per week, and there was a median of 319 episodes (range, 126-728 episodes) before evaluation in the neuro-ophthalmology clinic. All patients had normal optic nerves, and no plaques were noted in the retinal vessels. All 5 had macular drusen, which were predominantly extrafoveal and mild. Two patients underwent electrophysiology testing, which were both normal on full-field electroretinogram (ERG), but there was blunted central wave forms on multifocal ERG. Two patients underwent dark adaptation testing, which showed both prolong and diminished dark adaptation. Neuroimaging and thromboembolic workup were unrevealing.

CONCLUSIONS

TBVL is a distinct phenomenon from TMVL on awakening, which has a different demographic and symptomology. The etiology is unclear but seems to be a focal macular process in conjunction with an autoregulatory failure resulting in a supply-demand mismatch during low-light conditions.

Comparison of optic disc head vascular density status between crowded and normal discs: An optical coherence tomography angiography study

BACKGROUND

To compare the optic disc capillary vascular status between crowded and normal optic discs using optical coherence tomography angiography (OCT-A).

METHODS

A total of 101 eyes were included in this cross-sectional, comparative study. Fifty-one eyes with crowded optic discs (Group 1) were compared with 50 eyes with normal discs (Group 2). Peripapillary and optic disc head capillary vascular density measurements were obtained quantitatively with OCT-A.

RESULTS

Mean ages were 46.2 ± 6.2 years in Group1 and 45.9 ± 6.0 years in Group2 (p=0.796).Vertical disc diameters were 1.52±0.2 mm in Group 1 and 1.61±0.16 mm in Group 2 (p=0.022) whereas horizontal disc diameters were 1.53±0.17 mm in Group 1 and 1.61±0.13 mm in Group 2(p˂0.014). OCT-A findings were as follows: radial peripapillary capillary, vascular density whole image measurements (%); 49.6 ± 2.3 in Group 1 and 49.1 ± 2.3 in Group 2 (p=0.292), peripapillary capillary density; 53.3 ± 2.8 in Group 1 and 52.6 ± 2.6 in Group 2 (p=0.176), inside disc measurements 52.4 (48.7-54.7) in Group 1 and 46.5 (42.6-49.6) in Group 2 (p˂0.001). RNFL was 118.2 ± 12.2 µm in Group 1 and 110.8 ± 11.4 µm in Group 2(p=0.002).

CONCLUSION

The vascular density of the disc circumference in individuals with healthy crowded optic discs is not different from those with normal discs. However, inside disc measurements differ between crowded and normal size discs. This finding suggests that when the disc size is reduced, the amount of vessels in it does not decrease in a way that correlates with the size. Therefore, the vascular structures are suitable for compression in the narrow optic nerve head.

Transient Visual Loss in Young Females with Crowded Optic Discs: A Proposed Aetiology

I present four cases of transient visual loss (TVL) in young females with crowded optic discs. One patient had asymmetrical cup-to-disc ratios and only experienced TVL in the eye with the more crowded disc. I review the evidence for blood flow autoregulatory dysfunction within crowded optic discs in combination with reduced ocular perfusion pressure to propose a possible aetiology for both unilateral and bilateral TVL in young females with crowded optic discs.

Transient monocular blindness: Vascular causes and differential diagnoses

Transient monocular blindness is an acute episode of ischemic origin in which one eye has profound visual loss, followed by full recovery within one hour. Transient monocular blindness most often occurs in the setting of retinal ischemia secondary to carotid embolism, but other mechanisms have been reported, including thrombosis (most often in the setting of giant cell arteritis), hemodynamic disorders (secondary to severe carotid stenosis), or vasospasm. Transient monocular blindness is considered a transient ischemic attack originating in the carotid arteries, and must be managed the same as transient ischemic attack involving the brain, in order to prevent a subsequent stroke.