**Background:** Blue light, the high-energy end of the visible spectrum (approximately 400–500 nm), has been implicated in retinal damage, particularly through the generation of reactive oxygen species and accumulation of lipofuscin in retinal pigment epithelium cells, contributing to age-related macular degeneration (AMD). Beyond the classic photoreceptors (rods and cones), a subpopulation of retinal ganglion cells—intrinsically photosensitive retinal ganglion cells (ipRGCs)—expresses the photopigment melanopsin, with peak sensitivity at ~480 nm. These cells mediate non-image-forming visual responses, including pupillary light reflex, circadian photoentrainment, and photophobia. Given the widespread use of blue-enriched light-emitting diode (LED) devices, understanding both local retinal and systemic effects of blue light is clinically important. This narrative review aims to provide a comprehensive overview of the harmful biological consequences of blue light exposure on the human retina and body.
**Methods:** The review followed SANRA guidelines and searched PubMed/Medline, Scopus, EMBASE, Cochrane Database of Systematic Reviews, and Clinical Trials for studies published between 2010 and 2022. Keywords included “blue light”, “retina”, and “intrinsically photosensitive retinal ganglion cell”. Inclusion criteria were clinical studies and randomized controlled trials in English with human participants; studies with fewer than 10 participants were excluded. After screening 333 records, 20 abstracts were selected, and after full-text review, 17 studies were included.
**Key Results:** The 17 studies were categorized into three groups:
1. **Intraocular lenses (IOLs) and retinal protection (5 studies):** Neumaier-Ammerer et al. (2010) found no difference in visual acuity or contrast sensitivity between yellow-tinted and clear IOLs, except for color vision under mesopic conditions. Kara-Junior et al. (2011) reported no differences in central macular thickness, contrast sensitivity, or color vision after 5 years. Nagai et al. (2015) observed a statistically significant lower incidence of abnormal fundus autofluorescence (FAF) and any form of AMD in the yellow-tinted IOL group (p < 0.05). Ayaki et al. (2015) found improved ocular pain scores with yellow-tinted IOLs (p < 0.05) but no differences in other visual function subscales. Mokuno et al. (2016) found no significant difference in color vision error scores between macular disease and control groups.
2. **Retinal electrophysiology (3 studies):** Gagné et al. (2011) showed that short-term blue light exposure reduced both scotopic and photopic b-wave amplitudes on electroretinography (ERG), with effects persisting for one hour. Morita et al. (2018) reported that Lactobacillus paracasei KW3110 improved critical flicker frequency (CFF) at 4 weeks but not at 8 weeks. Li et al. (2021) demonstrated reduced multifocal ERG (mfERG) amplitudes in parafoveal regions among participants using visual display terminals >8 hours/day for >5 years.
3. **Systemic effects (9 studies):** Hoggan et al. (2016) found that thin-film optical notch filter spectacles (620 nm) reduced headache impact scores (HIT-6) in chronic migraine patients. Yuda et al. (2016, 2017) showed that blue light significantly decreased high-frequency (HF) heart rate variability (HRV) and increased LF/HF ratio, indicating vagal suppression. Zivcevska et al. (2018) demonstrated greater discomfort thresholds for blue light (470 nm) vs. red light (635 nm) under both monocular and binocular conditions. Kaiser et al. (2021) found enhanced orbicularis oculi electromyography (OO-EMG) responses in migraineurs with aura at 400% contrast. Zele et al. (2021) reported lower EMG thresholds and supranormal post-illumination pupil response (PIPR) in migraineurs, suggesting melanopsin hypersensitivity. Ali et al. (2021) found no significant increase in migraine attacks following blue multifocal pupillographic objective perimetry (mfPOP) stimulation.
**Clinical Implications:** The review underscores that while blue-blocking IOLs may reduce abnormal FAF and AMD incidence, their clinical benefit remains controversial due to inconsistent results across studies. The consistent finding that blue light triggers photophobia and migraine through ipRGC activation supports the use of tinted lenses (e.g., FL-41, optical notch filters) as potential therapeutic tools. The suppression of vagal cardiac modulation by blue light suggests possible cardiovascular implications, though studies are small and short-term. The review emphasizes the need for larger, longer-term studies with objective measures (e.g., OCT, ERG, pupillometry) and standardized lighting conditions to clarify blue light's damaging effects. It also highlights the importance of considering individual differences, such as macular pigment optical density and migraine subtype, in future research.