“Eye tattooing” encompasses two medically distinct concepts.
The two are fundamentally different in purpose, technique, and safety, so they must be clearly distinguished.
Corneal pigment implantation is a medical procedure performed by an ophthalmologist, used to treat corneal leukoma or iris defects. In contrast, eyeball tattooing is a body modification that injects ink under the conjunctiva, often performed by practitioners without specialized medical training, and carries a very high risk of serious complications.
KTP itself is a therapeutic procedure, not a disease. The following symptoms may occur after surgery.
Findings that may be observed after eyeball tattooing are as follows3).
| Indication | Specific Example |
|---|---|
| Cosmetic improvement | Corneal leukoma, corneal opacity |
| Functional improvement | Iris defect, aniridia |
| Symptom relief | Glare and diplopia after PI |
Corneal pigmentation is a useful alternative for patients who cannot be improved with contact lenses or reconstructive surgery 2). In recent years, procedures to change the color of the eye for purely cosmetic purposes have been increasing 1, 2).
In the study by Alio et al., the following exclusion criteria were established 1).
KTP procedures are broadly classified into superficial and intrastromal methods based on the depth of pigment placement 2).
Superficial Manual Keratopigmentation (SMK)
Method: Repeated punctures of the corneal surface with a 25–27G needle to deposit pigment.
Advantages: Useful for small-area corrections and touch-ups.
Limitations: Prone to fading; rarely used alone today.
Superficial Automated Keratopigmentation (SAK)
Method: An automated micropuncture device deposits pigment to a depth of 120 μm.
Advantages: More uniform and faster than the manual method.
Limitations: Fading may occur within one month, especially with lighter colors.
Manual Intrastromal Keratopigmentation (MIK)
Method: A corneal pocket is created with a diamond blade and filled with pigment.
Advantages: Longer pigment retention.
Limitations: Technically complex; not suitable for purely cosmetic purposes.
Femtosecond Laser-Assisted Keratopigmentation (FLAAK)
Method: A femtosecond laser creates a corneal tunnel, into which micronized mineral pigment is injected.
Advantages: Excellent pigment uniformity and retention, high safety
Indications: Both therapeutic and purely cosmetic purposes
Typical parameters of FLAAK based on the report by Alio et al.1) are as follows.
Ink is injected multiple times under the bulbar conjunctiva using a needle. The same ink used for skin tattoos is often employed3). This is a body modification without medical indication and is not recommended ophthalmologically.
In the series of 234 eyes by Alio et al. (including therapeutic indications), the complication rate was 12.82%, with the majority being photosensitivity (49%), fading (19%), and neovascularization (7%)2).
In the FLAAK study of 166 eyes for purely cosmetic purposes 1), the following results were obtained.
| Evaluation item | Result |
|---|---|
| Visual acuity change | No significant difference |
| Intraocular pressure change | No significant difference |
| Visual field (MD) | No significant difference |
| Endothelial cell loss | 3.5% (1 year) |
| Contrast sensitivity | Decreased but within normal range |
| Patient satisfaction | 84.3% |
In 166 eyes (83 patients) followed for 12 months, no infection, uveitis, corneal perforation, neovascularization, or retouching due to fading was observed. Two cases developed photosensitivity and dry eye for 4 months, which improved with medication. 1)
Retouching (color correction) after FLAAK is relatively common; D’Oria et al. reported that 35.4% required at least one retouching session. 2)
The only serious complication reported with FLAAK to date is bilateral progressive corneal ectasia in a patient with a history of LASIK, which was stabilized with corneal cross-linking (CXL). 2)
In ocular tattooing, globe perforation occurred in 11 of 17 reported cases (68%). 3) Complications associated with perforation include:
Other complications besides perforation have been reported: 3)
If ink reaches the inside of the eye, early removal is recommended3).
Femtosecond laser-assisted corneal pigmentation (FLAAK) is considered a relatively safe procedure when performed by an experienced ophthalmologist with appropriate indications. However, mild decreases in endothelial cell count and contrast sensitivity have been reported, and long-term safety data are still insufficient. Always consult thoroughly with a specialist before deciding.
Electron microscopy of corneal tattoo specimens shows electron-dense pigment granules within keratocytes and between collagen fibers. Sekundo et al. reported that pigment particles from non-metallic dye corneal tattoos were retained within the cell membranes of keratocytes even 61 years after the procedure.
The most widely used third- to fourth-generation micronized mineral pigments (Biochromaeyes®, Neoris®) have a particle size of less than 2.5 μm2). Animal studies have shown no pigment diffusion, inflammation, or neovascularization, indicating good biocompatibility2).
The pigment composition includes propanediol and micronized mineral pigments (iron oxide, titanium oxide, etc.) and is adjusted to match the pH of the cornea1). CE-certified medical-grade pigments are used.
In FLAAK, endothelial cell density decreased from 2393±124 cells/mm² preoperatively to 2309±127 cells/mm² one year postoperatively (a decrease of 3.5%), which was statistically significant1). Ferrari et al. also reported a 3% decrease in endothelial cells after one year2). Shorter surgical time and creation of tunnels near the limbus using a femtosecond laser may reduce manual incision, potentially minimizing damage to corneal nerves and endothelium1).
Ink particles that enter the eye move through the aqueous humor and coat the lens, corneal endothelium, and trabecular meshwork. This can cause severe foreign body reactions, uveitis, and secondary pigmentary glaucoma 3). Ink particles are phagocytosed by macrophages, and pigment deposited in the dermis triggers an immune response. Sarcoidosis-like uveitis has been reported as a delayed-type hypersensitivity reaction 3).
In the FLAAK study on 166 eyes (83 patients) for purely cosmetic purposes, Alio et al. reported no significant changes in visual acuity, intraocular pressure, or visual field at 12 months of follow-up, with a patient satisfaction rate of 84.3%. No serious complications were observed. 1)
In a review by Balparda et al., FLAAK is described as a “safe procedure with relatively few complications,” and postoperative visual acuity in normal eyes is maintained. Patient satisfaction for purely cosmetic purposes is reported to be approximately 92.5%. 2)
The following alternatives exist as methods to purely change eye color 2).
Permanent makeup on the eyelid margin (eyeliner tattoo) has been reported to cause meibomian gland dropout and tear film instability 3). Delayed-type hypersensitivity granulomas due to aluminum-silicate pigments have also been reported 3).
Data on the long-term safety (over 5 years) of KTP for purely cosmetic purposes are still limited 1, 2). Further research is needed, particularly on the following points.
Currently, very few facilities in Japan perform corneal pigmentation (keratopigmentation). This procedure is mainly performed in some facilities in Europe, the Middle East, and South America. If you wish to undergo the procedure in Japan, please consult a corneal specialist, including the possibility of referral to an experienced overseas facility.
