Isolated bitemporal hemianopia in a patient with COVID-19

Introduction. Symptoms of lesions of the I, VII and IX pairs of cranial nerves during SARS-CoV-2 infection are observed in about a third of cases. Isolated bitemporal hemianopia as a symptom of optic nerve damage at the chiasmal level in patients with COVID-19 has not been described yet. Case report. A 65-year-old man with a history of arterial hypertension and myocardial infarction and confirmed COVID-19 infection with severe lung damage on computed tomography. Patient developed bitemporal hemianopia, confirmed by the Donders test, on the second day of hospitalization. CT scan revealed no lesions and organic pathology in the parachiasmatic region and in the substance of the brain. Two days later, there was a complete restoration of lateral vision. Discussion. The most likely cause of bitemporal hemianopia was microthrombotic or inflammatory lesion at the chiasmal level. Risk factors for thrombotic complications: male gender, age 65, history of cardiovascular diseases, increased D-dimer levels, and signs of systemic inflammation (increased levels of C-reactive protein, fibrinogen, lactate dehydrogenase, and ferritin). An alternative hypothesis for the development of chiasmal syndrome may be direct viral invasion SARS-CoV-2 of the central nervous system.

Unique human orbital morphology compared with that of apes

Humans’ and apes’ convergent (front-facing) orbits allow a large overlap of monocular visual fields but are considered to limit the lateral visual field extent. However, humans can greatly expand their lateral visual fields using eye motion. This study aimed to assess whether the human orbital morphology was unique compared with that of apes in avoiding lateral visual field obstruction. The orbits of 100 human skulls and 120 ape skulls (30 gibbons; 30 orangutans; 30 gorillas; 30 chimpanzees and bonobos) were analyzed. The orbital width/height ratio was calculated. Two orbital angles representing orbital convergence and rearward position of the orbital margin respectively were recorded using a protractor and laser levels. Humans have the largest orbital width/height ratio (1.19; p < 0.001). Humans and gibbons have orbits which are significantly less convergent than those of chimpanzees / bonobos, gorillas and orangutans (p < 0.001). These elements suggest a morphology favoring lateral vision in humans. More specifically, the human orbit has a uniquely rearward temporal orbital margin (107.1°; p < 0.001), suitable for avoiding visual obstruction and promoting lateral visual field expansion through eye motion. Such an orbital morphology may have evolved mainly as an adaptation to open-country habitat and bipedal locomotion.