Nonarteritic Anterior Ischemic Optic Neuropathy After Cataract Surgery: A Systematic Review and Meta-Analysis

Author: Shew W, Wang MTM, Danesh-Meyer HV.

Geographical coverage: North America, Asia, the Middle East, and the United States.

Sector: Cataract surgery

Sub-sector: Risk factors

Equity focus: Not reported

Study population: Patients with cataracts

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background:

Non-arteritic anterior ischaemic optic neuropathy (NAION) is a leading cause of vision loss in older adults. Its pathophysiology is unclear, but recognised risk factors include hypertension, diabetes, and a small cup-to-disc ratio. It often results in permanent optic nerve damage within weeks. Cataract surgery has been debated as a potential trigger for NAION, with case reports and observational studies suggesting a temporal link. Postoperative factors such as inflammation or intraocular pressure changes contribute to this risk. However, inconsistent findings and varying definitions of postcataract surgery NAION (psNAION) complicate the issue. Cataract surgeries are becoming more common as populations age; therefore, determining whether the procedure increases the risk of NAION is clinically important.

Objective:

To assess whether cataract surgery increases the risk of subsequent early- and delayed-onset postcataract surgery NAION (psNAION) within the first year compared with spontaneous NAION (sNAION), and to determine whether any covariates predict this risk in the general adult population.

Main findings:

The review included nine studies, five of which were included in the meta-analysis. All studies were retrospective; among these, two were population-based, one was a survey, and the remainder were cohort studies of patients undergoing cataract surgery. A total of 320 psNAION cases, 1,307 sNAION cases, 1,587,691 cataract surgeries, and 1,538,897 non-cataract surgery controls were included.

Meta-analysis of 63,823 cataract surgeries and 161,643 controls indicated a 4.6-fold increased risk of psNAION within one year of surgery (hazard ratio, HR: 4.6, 95% confidence interval [CI]: 2.7–7.8). Incidence rates were highest within the first two months postoperatively (99.92 per 100,000/year), decreasing to 32.36 per 100,000/year by one year. psNAION cases were on average 7.6 years older (95% CI: 5.09–10.14) than sNAION cases. However, other baseline risk factors showed no significant differences in pooled analyses. Mean time to onset of psNAION ranged from 2.2 to 43.8 months. Notably, 21% (18/85) of cases occurred within 3 days postoperatively, and a further 18% (15/85) occurred within 6 weeks.

Methodology:

The searches were conducted in PubMed, Embase, MEDLINE, and the Cochrane Database from 1960 to 1 June 2021 to identify all retrospective or prospective observational studies that reported NAION incidence as a primary outcome after cataract surgery. Reference lists of the retrieved articles were scanned for further eligible studies. The review did not apply any restrictions on setting, country, or language. Two reviewers independently screened the identified articles and extracted the relevant data. Discrepancies were resolved by consulting a third reviewer. The methodological quality of included studies was assessed using the Newcastle-Ottawa Scale. The findings were synthesised using random-effects model meta-analysis, and heterogeneity was assessed using the I² statistic.

Applicability/external validity:

The review acknowledged that most included cases were historical, and advances in surgical techniques – such as the shift to topical anaesthesia and less invasive procedures – may reduce the current risk of psNAION, limiting generalisability to modern practice. They also noted considerable heterogeneity across studies in terms of design, definitions, and populations, which complicates direct comparisons and broader applicability.

Geographical focus:

The review did not apply any geographical limits. The included studies were from North America, Asia, and the Middle East, though the majority were conducted in the United States.

Summary of quality assessment:

Overall, there is medium confidence in the review’s conclusion. The review employed a comprehensive search strategy with clearly defined inclusion and exclusion criteria. Screening and data extraction were conducted independently by two reviewers, and risk of bias was assessed using established tools. Study characteristics were thoroughly documented, meta-analyses were appropriately conducted, and heterogeneity was systematically explored. However, the review did not report findings by risk-of-bias status, nor did it provide a list of excluded studies.