Key point: The large 2023 Finnish registry study published in Journal of Cataract & Refractive Surgery found no excess of newly diagnosed mental‑behavioural or neurological diseases in 4 986 patients who received bilateral blue‑filtering IOLs compared with matched patients who received clear UV‑only IOLs. Other, mostly smaller studies give a mixed picture: some report subtler changes in sleep architecture, circadian hormone output or cognition that favour clear lenses, while several others find no difference or even slightly better sleep with BF‑IOLs. Overall, hard‑endpoint morbidity (depression, dementia, Parkinson disease, etc.) has not been shown to rise after implantation of blue‑blocking lenses, but there is biologically plausible concern that permanently reducing short‑wavelength light could blunt circadian signalling.
1 | What the 2023 JCRS paper actually showed
| Feature | Details |
|---|---|
| Citation | Karesvuo M et al. J Cataract Refract Surg. 2023;49(7):679‑685. doi:10.1097/J.JCRS.0000000000001184 |
| Design | Retrospective, population‑based cohort drawn from a Finnish hospital registry. All patients had uncomplicated bilateral cataract surgery between 2007‑2018. Follow‑up ran through 2021. |
| Groups | • Clear UV‑only IOLs (non‑BLF) = 2 609 patients • Blue‑Filtering IOLs (BLF) = 2 377 patients |
| Outcomes | Incident ICD‑10 diagnoses of (a) mental & behavioural disorders and (b) diseases of the nervous system recorded after second‑eye surgery. |
| Statistics | Kaplan‑Meier curves and multivariable Cox models adjusted for age & sex. |
| Findings | No significant difference in overall incidence of any mental or neurological diagnosis. A univariate hint of fewer sleep‑disorder codes in the BLF group lost significance after adjustment (HR 0.76, 95 % CI 0.53‑1.07). |
| Conclusion | “BLF IOLs were not associated with mental and behavioural disorders or diseases of the nervous system.” |
Strengths – bilaterally implanted lens of the same type, >4 900 patients, up to 14 years’ follow‑up.
Limitations – non‑random lens allocation, reliance on hospital coding (may miss milder cases), no direct sleep or cognition tests.
2 | Other peer‑reviewed evidence hinting at possible negative effects of blocking blue light
| Domain | Core study (year) | What it found | Quality & caveats |
|---|---|---|---|
| Circadian physiology & cognition | Chellappa SL et al. JAMA Ophthalmol 2019 (N = 13 IOL patients in‑lab) | Compared with clear‑lens recipients, BF‑IOL patients showed slower psychomotor reaction times, less slow‑wave sleep and smaller melatonin responses during evening blue‑enriched light. | Small cross‑sectional lab protocol; not powered for disease outcomes. |
| Global survival | Tuuminen R et al. iScience 2021 (Finnish registry, N≈48 500) | Clear‑lens recipients had 10 % lower all‑cause mortality over ≈7 years than BF‑IOL recipients after multivariable adjustment. | Observational; cannot separate lens choice from surgeon or patient factors. |
| Sleep & mood in the community | Ayaki M et al. Sleep & Biological Rhythms 2015 (Japan, N = 961) | BF‑IOL wearers reported more insomnia symptoms and higher depression scores six months after surgery than clear‑IOL subjects. tandfonline.com | Questionnaire study; baseline mental‑health status not randomised. |
| Meta‑review of visual & non‑visual outcomes | Brøndsted AE & Cochrane Review group 2015/2018 | No strong visual‑acuity benefit of BF‑IOL; mixed or null evidence for glare, AMD progression, sleep or cognition; trials generally small (<150 per arm) and heterogeneous. | Highlights need for larger randomised data. |
Counter‑evidence exists as well: two RCTs found no deterioration of sleep after BF‑IOL implantation (Alexander I 2014; Brøndsted AE 2015/2017), and one reported slightly better sleep efficiency with the blue‑filter lens. pmc.ncbi.nlm.nih.gov
3 | Why the biology remains plausible
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Intrinsically‑photosensitive retinal ganglion cells (ipRGCs) use melanopsin, peaking at ~480 nm.
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Their signals set circadian phase, pupil reflexes, alertness, and sleep pressure.
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The aged crystalline lens already filters ~30‑50 % of this band. A yellow chromophore in BF‑IOLs cuts another 15‑25 %.
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Chronic under‑stimulation could, in theory, worsen sleep fragmentation, mood or neurodegenerative risk—especially in elders who spend much of the day indoors at low light levels.
4 | Current best interpretation
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Large registry (JCRS 2023) → no measurable increase in coded mental‑health or neurological diagnoses up to ~14 years post‑surgery.
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Smaller mechanistic studies → blue‑filtered lenses may blunt some immediate non‑visual light responses (melatonin, vigilance, slow‑wave sleep).
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Population data on survival or dementia → mixed; one Finnish study favoured clear lenses, a Taiwanese claims‑database study found no dementia signal.
Therefore the headline claim that BF‑IOLs cause mental or neurological disease is not supported; if an effect exists it is likely subtle and manifests through sleep/circadian pathways rather than frank diagnostic categories.
5 | Practical guidance for patients & clinicians
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Disease prevention: Neither lens type has shown protection against age‑related macular degeneration in long‑term randomised data.
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Non‑visual considerations: Patients with insomnia, seasonal mood issues or high cognitive‑performance demands may prefer clear UV‑only IOLs, while those at high risk of intense light exposure (eg, arc‑welding) might opt for BF‑IOLs.
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Lighting hygiene matters more than lens tint: Adequate bright‑daytime light (>1000 lux), limited nighttime blue‑rich light, and outdoor activity remain the strongest circadian levers.
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Future research: Larger randomised trials measuring objective sleep, cognition and mood over years—not weeks—are needed to settle the question.
Bottom line
The 2023 JCRS study is real and methodologically sound; it reports no clinical excess of mental or neurological disorders after bilateral implantation of blue‑filtering IOLs. Evidence for subtler circadian or cognitive downsides remains suggestive but not definitive, and conflicting studies exist. Clinicians should individualise IOL choice, balancing retinal‑protection theory against the proven physiological value of blue light for brain health.
