A painful red eye with rainbow halos, headache, nausea or vomiting needs an eye emergency department that day
These can be signs of acute angle-closure glaucoma: fluid cannot drain and eye pressure rises sharply. Longer delay can cause irreversible optic-nerve damage. During Wuhan's lockdown, average delay was about 241 hours and blindness affected 21.87%; in the corresponding following-year period, delay was about 121 hours and blindness 7.84%.
What it takes
The immediate decision costs nothing. Eye-pressure and anterior-chamber examinations can take half a day.
What you may gain
A Wuhan eye hospital compared acute primary angle-closure presentations during 76 lockdown days in 2020, 54 people/64 eyes, with the corresponding 2021 period, 46 people/51 eyes. Demographics were similar. Symptom-to-treatment times were 241.84±211.95 versus 121.53±96.12 hours (P=0.001); presentation pressures were 52.63±12.45 versus 45.16±9.79 mmHg (P=0.001). Blindness rates were 21.87% versus 7.84%. Glaucomatous optic neuropathy occurred in 20/64 eyes (31.25%) versus 7/51 (13.73%), P=0.03. A Korean hospital retrospectively studied 50 eyes after one acute episode followed by lens extraction; 25 (50%) had some visual-field loss one year later. Longer time to pressure reduction predicted greater risk of loss (P=0.005). In another prospective study, 43 people with shallow anterior chambers lay prone in darkness for 1 hour. Pressure rose in both eyes (P<0.01), by a median 3.60 mmHg in the dominant eye and 2.70 mmHg in the other (P<0.05).
Context & considerations
Grade B: Wuhan's retrospective comparison cannot separate delay from other lockdown effects, and the Korean retrospective sample contained only 50 eyes. The proposed trigger is not screens themselves but darkness dilating pupils combined with prolonged head-down/prone positioning pushing the lens forward. People with shallow chambers are susceptible, particularly those over 50, farsighted people and those with family histories of angle closure. The source describes this pattern as unlikely in young people gaming overnight. Headache and vomiting can overshadow the eye symptoms and lead to misdiagnosis as gastroenteritis, migraine or hypertension. Painless non-red one-eye loss is discussed in entry 5; blue-light glasses in Chapter 6, entry 16.
Research & references
Zhou L, Wu S, Wang Y, Bao X, Peng T, Luo W, Ortega-Usobiaga J (2022). Clinical presentation of acute primary angle closure during the COVID-19 epidemic lockdown. Frontiers in Medicine, 9, 1078237. https://doi.org/10.3389/fmed.2022.1078237; Sung MS, Kim HJ, Park SW (2023). Predictors of long-term visual field outcome after an episode of acute primary angle closure. Clinical & Experimental Ophthalmology, 51(4), 291-299. https://doi.org/10.1111/ceo.14206; Wang J, Wang J, Ng TK, Huang C (2025). Asymmetric intraocular pressure changes in dominant and contralateral eyes: the dark room prone provocative test. Seminars in Ophthalmology, 40(4), 325-331. https://doi.org/10.1080/08820538.2024.2443972