Semaglutide Linked to Rare Vision Loss After Rapid 40kg Weight Drop
A 42-year-old man developed serious optic nerve damage after losing 40 kg in 2 months on Wegovy, raising ocular safety concerns.
Summary
Semaglutide is widely used for weight loss, but reports of a rare eye problem called NAION, a sudden painless loss of vision from reduced blood flow to the optic nerve, are emerging. This case report describes a 42-year-old man with diabetes, high blood pressure, high cholesterol and a long smoking history. He lost about 40 kg in 2 months on Wegovy, then noticed blurred vision in the lower part of his right eye. Exams showed a swollen optic disc and a matching visual field defect, and other causes were ruled out. Semaglutide was stopped and he received steroids, but after 6 months the swelling had resolved while the vision defect remained. One case cannot prove cause, but the authors urge vigilance, especially with very rapid weight loss.
Detailed Summary
Semaglutide has become one of the most widely used drugs for obesity and type 2 diabetes, and interest in it among health-conscious adults and clinicians is intense. As use expands, safety signals are emerging, including nonarteritic anterior ischemic optic neuropathy (NAION), a sudden, painless form of vision loss caused by reduced blood flow to the optic nerve head. This case report from Yeungnam University Hospital describes what the authors believe is the first such case in South Korea.
A 42-year-old man presented with blurred vision in the lower field of his right eye, with unclear onset. He had type 2 diabetes and hypertension for 10 years, dyslipidemia, a 15-year history of smoking about a pack a day, and took low-dose aspirin. He had started Wegovy at 0.25 mg, stepped up to 1.7 mg, and held that dose for about 2 months. He reported losing roughly 40 kg in 2 months, exercising about 2 hours daily, and having no gastrointestinal side effects. His weight at presentation was 93.4 kg at 168.3 cm.
Examination showed best-corrected visual acuity of 20/20 in both eyes, normal intraocular pressure (18 and 17 mm Hg), intact pupillary reflexes, and normal color vision. The right eye had optic disc edema with blurred margins, and automated perimetry showed a localized inferior visual field defect matching his symptoms. Antibody tests for aquaporin-4 and myelin oligodendrocyte glycoprotein were negative, and brain and orbital MRI showed only equivocal bulging of the right optic disc without signal change or enhancement. NAION was diagnosed.
Semaglutide was stopped, and after discussion with the patient he received empirical intravenous methylprednisolone, 1 g daily for 3 days, though no treatment is proven for NAION. At 6 months, the disc swelling had resolved, leaving mild optic disc pallor, but the inferior visual field defect persisted. Optical coherence tomography showed thinning of the ganglion cell-inner plexiform layer matching the field defect.
The authors note this was atypical: NAION usually occurs after age 50 and is tied to a small, crowded "disc-at-risk" anatomy, yet follow-up photographs did not suggest a markedly crowded disc, hinting at an added precipitant. Hathaway et al. in 2024 first linked semaglutide to NAION in a neuro-ophthalmology cohort, and Cai, Hsu and Simonsen supported an association, whereas Abbass and Chou found no significant increase. Differences in case ascertainment, comparators and follow-up, and reliance on diagnostic codes versus neuro-ophthalmologist adjudication, may explain the discord.
Proposed mechanisms include direct drug effects on optic nerve head perfusion or vascular regulation, and indirect effects of rapid weight loss such as reduced intake, relative hypovolemia, dehydration and low blood pressure, on top of diabetic, hypertensive and smoking-related microvascular disease. The authors stress causality cannot be established from one case, no pre-treatment eye exams were available, and disc anatomy could not be assessed in the acute phase. They call for multicenter studies and research on whether the speed and magnitude of weight loss drive risk.
Key Findings
- A 42-year-old man developed right-eye NAION after losing about 40 kg in roughly 2 months on semaglutide (Wegovy), reaching 93.4 kg at presentation
- Semaglutide was titrated from 0.25 mg to 1.7 mg and held at 1.7 mg for about 2 months before visual symptoms appeared
- He had multiple vascular risk factors: type 2 diabetes and hypertension for 10 years, dyslipidemia, and 15 years of smoking about one pack per day
- Visual acuity stayed 20/20 in both eyes, but perimetry showed an inferior field defect and fundus exam showed right optic disc edema
- Anti-aquaporin-4 and anti-MOG antibodies were negative and MRI showed no optic nerve signal change or enhancement, supporting NAION over inflammatory causes
- After stopping semaglutide and 3 days of IV methylprednisolone (1 g/day), disc edema resolved by 6 months but mild pallor and the field defect persisted
- OCT showed ganglion cell-inner plexiform layer thinning matching the field defect, and follow-up photos did not suggest a markedly crowded disc
Methodology
This is a single-patient case report from Yeungnam University Hospital with written informed consent. The evaluation included best-corrected visual acuity, intraocular pressure, pupillary and color vision testing, fundus photography, Humphrey automated perimetry, serum antibody testing, and MRI of the brain and orbits. Follow-up at 6 months used repeat fundus examination, perimetry and optical coherence tomography. No statistical analysis was performed, and no pre-treatment ophthalmic records were available.
Study Limitations
Causality cannot be established from a single case, and the authors cannot separate a direct drug effect from the effects of rapid weight loss or the patient's underlying vascular disease. Baseline ophthalmologic data were unavailable, and optic disc anatomy could not be assessed during the acute edematous phase. The report does not state any conflicts of interest, and the exact symptom onset was unclear.
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