Keratopigmentation in the modern era: A review of current techniques, results, and safety

Abstract

To conduct a literature review on current knowledge regarding keratopigmentation (KTP), with a particular focus on femtosecond-assisted procedures. A narrative literature review was performed. Academic databases (PubMed, Google Scholar, Cochrane Library, and SciELO) were searched for articles containing the keywords “keratopigmentation” and “corneal tattoo.” All relevant articles were reviewed, and appropriate ones related to the topic were included in the review. KTP has a variety of indications, including enhancing the aesthetic profile of blind eyes with decompensated corneas and alleviating symptoms related to iris atrophy. The trend of strictly cosmetic KTP has recently gained popularity among several surgeons worldwide. Despite some controversy, most articles reported excellent outcomes associated with KTP, alongside a high safety profile. Histopathological studies have demonstrated that modern micronized pigments are entirely biocompatible. Femtosecond laser-assisted KTP appears to be a safe and effective procedure. However, more long-term studies are necessary to enhance our understanding of the risks associated with strictly cosmetic applications of this technique.

Introduction

Keratopigmentation (KTP), commonly referred to as “corneal tattooing,” is a surgical procedure that involves depositing pigments into the human corneal stroma.[1] This technique has been proposed as an effective and safe option for enhancing the cosmetic appearance of blind eyes that are not suitable for corrective surgery,[2] as well as for alleviating visual symptoms associated with pupillary or iris defects.[3]

The history of KTP is extensive, with numerous techniques proposed for corneal tattooing.[4] One of the earliest descriptions of the process comes from the Greek physician Galen (c. 129–c. 200 AD), who used it “to disguise unsightly leucomata.”[5] The technique of corneal tattooing through multiple punctures for aesthetic restoration was also documented by the Byzantine author Aetius Amidenus in the sixth century.[6] According to Hasani et al.,[7] “ both physicians would first cauterize the corneal surface with a heated stilt, and after the cauterization, the dye was applied to the eye using a variety of pigments such as powdered nutgalls, iron or copper sulfate.” The modern technique of KTP started with the oculoplastic surgeon Louis Von Wecker, who would use cocaine to anesthetize the eye surface and then insert black ink pigment with the use of a needle.[8]

Methods

This work constitutes a narrative literature review focused on KTP, with a particular emphasis on its cosmetic indications—an area of growing clinical and social relevance. The primary aim of this review was to explore, summarize, and critically appraise the current body of literature surrounding KTP, offering an integrated perspective on the available evidence, its development over time, and future areas for research and clinical improvement.

The literature search was conducted using a multi-database strategy, including PubMed, Google Scholar, the Cochrane Library, and SciELO. The search terms employed included “Keratopigmentation,” “Corneal Tattoo,” “Cornea Tattoo,” and “FLAAK.” No restrictions were applied with regard to the year of publication, to include both historical and contemporary perspectives on the technique. However, language was restricted to English, Spanish, and French, reflecting the linguistic competencies of the author team and the predominant languages used in KTP-related literature.

The initial phase involved screening titles and abstracts for relevance. Articles were selected for full-text review if they addressed KTP directly or tangentially, including clinical applications, surgical techniques, outcomes, complications, or ethical considerations. Reference lists of included articles were also manually screened to identify additional sources that may have been omitted in the original database search.

All selected full-text articles were independently reviewed by at least two authors. To promote collaborative assessment and consistency in interpretation, the authors conducted a series of online meetings in which the articles were discussed in detail. Differences in opinion were resolved by consensus.

The final selection of articles reflects a combination of methodological rigor, clinical relevance, and diversity in perspective. This process enabled the authors to develop a narrative synthesis of the current evidence base, highlighting key themes, knowledge gaps, and areas for further research in KTP, particularly in the context of cosmetic indications.

Indications of KTP

Currently, KTP is a viable procedure that can be applied in various clinical scenarios. Traditionally, most KTP procedures have had restorative or therapeutic objectives. Early interventions primarily aimed to enhance the aesthetic profile of blind eyes with decompensated corneas or leukocoria[9] in patients “deemed inappropriate candidates for penetrating keratoplasty.”[10] Today, corneal tattooing is still used occasionally “for the treatment of corneal scars in eyes without visual prognosis, when iris print contact lenses or bulbar shells are not tolerated and the patient is not willing to undergo enucleation.”[11] In these circumstances, patients generally report high levels of satisfaction with the outcomes.[12]

Another indication for KTP is the alleviation of dysphotopsia caused by iris anomalies, such as large iridotomies or iris atrophy. Segal et al.[13] described a series of patients who received treatment by intralamellar manual PTK for symptoms related to large peripheral iridotomies. All patients were either intolerant of or unwilling to try painted contact lenses, and each reported at least some improvement in their symptoms following surgery. Islam and Franks[14] published the positive effects of KTP in managing glare in patients with large iridotomies near the interpalpebral fissure. For patients considering KTP to address post-iridotomy dysphotopsias, a straightforward test has been devised and published by Ong-Tone et al.[15] In this test, a surgical marking pen is used to apply a mark over the area of the peripheral iridotomy believed to be causing the symptoms. This marking hinders the entry of light through the iridotomy, allowing the patient to evaluate any improvement in their dysphotopsia symptoms. If an improvement is noted, the patient can then proceed with KTP, which is expected to yield favorable results.

Purely cosmetic KTP in normal-seeing eyes has recently grown in popularity across the globe and is currently offered at a number of eye surgery centers. The idea behind this approach is to provide an easy and safe way to change the apparent color of the eyes to better align with the patient’s desires. Previous studies have noted participants mention blue iris color as “a positive aspect than other bridal colors,” mentioning it as a “blue-eyes stereotype” in which this color of eyes is preferred.[16] This preference for lighter eye color can be attributed to the diffusion of “Western, of American, beauty ideals” in a globalized “blonde and blue-eyed model.”[17] In strictly cosmetic KTP, results are also encouraging, with numerous researchers finding this procedure to achieve “good cosmetic results” and being “associated with high patient satisfaction.”[18]

Surgical techniques

Various techniques for KTP have been developed over time, featuring numerous modifications in both the application methods and the composition of the pigments used. Currently, according to Hasani et al.,[7] KTP procedures can be categorized into two groups based on the relative depth at which the dyes are placed: superficial (which includes superficial manual KTP and superficial automated KTP) and intralamellar (which encompasses manual intralamellar KTP and femtosecond-assisted KTP).

Superficial manual KTP

Superficial manual KTP (sometimes referred to as SMK) was the first method of KTP ever developed and has been used for thousands of years. It consists of the inclusion of dye in the superficial layers of the cornea via multiple repeated punctures by using a pointy device, such as a needle [Fig. 1]. Al-Shymali et al.[19] report using a 25-G sterile needle “used by repeatedly puncturing the area of the cornea, in which KTP was needed and a drop of pigment had been previously deposited.” A 27-G needle has also been used successfully.[20]

Figure 1.

Immediate post-surgical view of a female patient who underwent superficial manual keratopigmentation using commercial skin tattoo ink. The patient had a history of congenital glaucoma and a decompensated cornea, making her a non-candidate for keratoplasty.

Superficial manual KTP is now very seldomly used and has been replaced by automated methods which are easier and faster to perform. As has been emphasized, manual techniques are “used only in cases in which a small pocket has to be used to mask a small underlying defect or a peripheral iridotomy.”[19] This technique can also be used adjunctly as a touch-up to improve cosmesis “in cases where intrastromal KTP was not sufficient to provide a satisfactory cosmetic appearance because of superficial corneal opacities.”[20]

Superficial automated KTP

Superficial automated KTP (sometimes referred to as SAK) involves using an automatic micropuncturing machine to deposit dye in the anterior layers of the corneal stroma, typically up to 120 µm from the corneal surface[7] [Fig. 2]. Automatic micropunctures are repeated “until the adequate amount of micronized pigment [is] visually presented in the superficial cornea to achieve an acceptable cosmetic appearance.”[21] This technique can either be used as a standalone procedure or combined with intralamellar procedures when these do not produce a good enough aesthetic result.[19] A puncture device (Vissum Eye MP System; Madrid, Spain) has been designed for deposition of pigment in the cornea,[19] allowing for controlling the penetration depth of the needles by modifying the longitudinal axial vibration of the tip.[22] There are multiple tip types that can be used depending on the area that needs to be covered. For limbus and pupil simulation, single-needle tips are recommended, while iris simulation should be done with tips including three or five needles.[22] Other automated devices, not made for eye surgery, have been used before, in an off-label manner. Singh and Sinha[23] reported the use of a digital permanent makeup cosmetic tattoo machine (Model Z × 1511) “manufactured by a Chinese company” (exact company name unspecified) with favorable cosmetic results and a good safety profile. The Ultra Pen (Electric Ink; Barcelona, Spain) has also been successfully used for automated superficial KTP, employing both one-needle and three-needle tips.[24] With any superficial technique, some color fading can occur naturally, especially with lighter colors and during the first month after the procedure.[25] Animal studies have demonstrated this method to not cause any corneal pigment dispersion, inflammation, or neovascularization.[22]

Figure 2.

Clinical photograph of a blind patient with decompensated cornea who underwent superficial automatic keratopigmentation using commercial skin tattoo ink. Courtesy of Dr. Isabel Cristina Gómez-Suárez (Medellín, Colombia)

Manual intralamellar KTP

Manual intralamellar KTP (sometimes referred to as MIK) is a manual technique in which a number of corneal pockets are created, later to be filled with pigment. This technique has been extensively used[7] mainly to correct visual symptoms related to iris defects and for aesthetic reasons in blind eyes not amenable to other surgeries. It is not recommended for purely aesthetic reasons in normal-seeing eyes as it may not have the exact nature needed for a natural-looking aspect. A variation of manual intralamellar KTP that has been described is creating a corneal flap with a microkeratome and placing tattoo pigment on the interface. This has been used in the past to hide leukoma and has been described as providing a good result.[26]

Intralamellar pigment deposition has been proven to be safe and effective, both in animals and in humans. Amesty et al.[27] performed manual intralamellar KTP in 28 New Zealand white rabbits and found no pigment diffusion, inflammation, or neovascularization upon histopathological examination.

A number of different surgical techniques for manual intralamellar KTP have been proposed and tested. One of them includes making a radial incision superiorly with a calibrated diamond blade up to 40%–50% of stromal depth and then using a helicoidal dissector (similar to the one used to implant corneal rings) to dissect corneal lamellae at the same depth.[19] This tunnel is later filled with pigment by using a 1 mL syringe with a 27-G flat cannula. Helicoidal tunnel directors for PTK have been designed by Alió and are currently sold by Epsilon (Epsilon Eye; Mumbai, India) [Fig. 3].

Figure 3.

Helicoidal dissectors and pupil dissectors designed for manual intralamellar keratopigmentation

Another technique[19] involves marking the pupil zone and then making 4–5 radial incisions from the edge of the marked pupil to the limbus, penetrating 40%–50% of the corneal thickness using a 45° knife. A microcrescent knife is then employed to perform intralamellar dissection, creating a tunnel that connects all the radial incisions. To shape the pupil, an arcuate incision is made, taking care to avoid contact with the radial incisions or the dissections created. These dissections are subsequently filled with pigment to simulate the appearance of the iris and the pupil respectively.

Finally, another technique includes a partial manual trephination of the cornea (generally up to 50%) followed by a lamellar dissection with a diamond blade, forming a flap. Then, the interface of this flap is filled with pigment.[11]

Femtosecond-assisted KTP

Femtosecond-assisted KTP was formerly known by the acronym FAK.[28] Nevertheless, to avoid confusion with a similar-sounding word, it has started to be now referred to as (femtosecond laser-assisted intralamellar KTP) FIK.[19] It is also referred to as femtosecond laser-assisted annular KTP (FLAAK). Any of the three acronyms can be currently found in the literature as there is no standardization so far.

All femtosecond-assisted KTP procedures involve the repurposing of the intrastromal corneal ring modules of femtosecond lasers. This includes modifying the characteristics of a 360° corneal ring module to create a potential space that will later be filled with pigment [Fig. 4]. As of the writing of this article, there is no specific KTP module available for any femtosecond laser; consequently, all procedures are performed as off-label applications of the original intracorneal ring module.

Figure 4.

Clinical photograph of a patient who underwent femtosecond-assisted keratopigmentation 5 years ago

The general technique is as follows: the patient is prepared and draped. Then, a femtosecond laser is used to create corneal tunnels using an intracorneal ring module. Tunnel parameters vary depending on the surgeon’s preferences. Internal diameter is generally set as 4.0 mm,[29] 4.5 mm,[30] or 5.5 mm,[31] while the external diameter is generally set as 9.0 mm,[30] 9.3 mm,[32] or 9.5 mm.[29,31] Tunnel depth is variable, ranging from 230 μm,[29] 300 μm,[30,31] to 350 μm.[31] It is currently our practice to use a 5-mm internal diameter and a depth of 175 μm for the tunnel creation. Femtosecond energy is generally set as 1.5 mJ[30] to 2 mJ.[31] One or two incisions are also programmed on the laser to access the tunnels. When one incision is made, it is made superiorly at 90°[29] so as to be covered by the eyelid. When two incisions are made, they are regularly programmed at 90° (superior) and 270° (inferior) to allow for easier access to different segments of the tunnel. In those cases where only one incision is made with the femtosecond laser, a second incision is manually made using a calibrated micrometer diamond blade.

Once the tunnel is created, helicoidal dissectors are used to open and extend it as close to the corneal limbus as possible. Neoris dissectors (with a smooth internal edge and a sharp external side) can be safely used to dissect the cornea toward the corneal limbus in an easy and safe manner [Fig. 5]. Ideally, the limbus itself should not be touched, resulting in a small, regular ring of untreated cornea approximately 1 mm in width that remains unchanged in color. The presence of this dark “limbal ring” not only enhances the safety of the procedure by preventing pigment contact with the limbus but also improves the aesthetic outcome. Previous psychological studies have demonstrated that faces with a dark corneal limbal ring in the eyes are perceived as more attractive than those without, likely serving as an indicator of youth and health.[33] Dark limbal rings can also subconsciously act as a health cue, with women rating males with limbal rings as “more desirable short-term mates.”[34]

Figure 5.

Neoris dissectors

Finally, the said tunnel is filled with pigment, which can be done by one of two approaches. The most common is merely injecting the pigment by using a syringe coupled with a flat cannula.[7] Alternatively, some surgeons impregnate the helicoidal dissectors with pigment and then repeatedly enter the tunnels, depositing small amounts of color with each movement. This latter technique may result in a less homogeneous, and thus more natural, appearance to the eye.

A number of femtosecond laser brands have been used to create the tunnels for this technique. At the time of writing this article, the only femtosecond machine capable of constructing the tunnels and the two venting incisions is Zeiss’ VisuMax (Carl Zeiss Meditec AG; Jena, Germany).[32] Other machines that have been used for performing this procedure include the Allegretto FS200 (Alcon; Forth Worth, United States)[35] and IntraLase (Advanced Medical Optics Inc; Santa Ana, California).[19]

FLAAK was first described by Alió et al.[29] for pathological eyes in 2011 and by Ferrari[36] for pure cosmetic purposes in 2015.

Pigments and inks

A number of different pigments and inks have been used in the past to perform KTP, with most of them seeming to provide a safe surgery.

Commercially available skin tattoos have been used before, and most articles describe them to be safe for corneal application. Ong-Tone et al.[15] used alcohol-based black tattoo pigment (Spaulding Color Corp, Voorheesville, NY) in a group of patients with iridotomy-induced dysphotopsia and did not report any complications. This same kind and brand of tattoo ink has been reported in a case of femtosecond-assisted KTP for a blind eye with leukocoria, finding “no intraoperative or postoperative adverse events” at 6 months follow-up.[9] Indian authors have described successfully and safely using a commercial skin tattoo ink (Jet Black Outliner Tattoo Ink; Star Brite Colors; Connecticut, United States) in a blind patient with a decompensated cornea.[37] Garrido-Hermosilla et al.[38] also used commercial black skin tattoo ink (Alkimia Inkside Deep Black; Alkimia Technology and Stetic SA; Madrid, Spain) to simulate a pupil in a bilaterally blind patient with terminal glaucoma and severe band keratopathy. Specifically, they used a single-dose container with 3 mL of ink. The authors emphasize that “the use of sterile single-dose containers greatly facilitates both the surgery in time and in form.” They did not show “any side effects” to the use of skin tattoo ink in the patient.

Sirerol et al.[39] evaluated the biocompatibility of black iron-oxide mineral micronized pigments (based on iron oxide, ferric oxide yellow, CI 15850, pigment blue 29, ethanol, propylene glycol, glycerin, drilling, amidroxy pamplemousse, and sorbitol) in leghorn hens subjected to manual intralamellar KTP. The pigment layer was found to be well-defined, with no signs of pigment diffusion or undue inflammation upon histopathological study.

Different pigments used for medical tattoos have been used previously, with good results. Yin et al.[35] used pigments employed for medical tattoos (PenMark, PMT Corporation; Minnesota, United States) in patients who underwent femtosecond-assisted KTP due to symptomatic iris defects. No complications were noted, aside from some initial foreign body sensation and light sensitivity. Similarly, Chao et al.[40] used the same brand of pigments (using a mix of white, navy blue, slate blue, charcoal green, and green) in a patient with intractable photophobia secondary to traumatic aniridia in a hypotonous eye. No complications were found, and dye color showed no fading past 18 months of following. Significant color change by oxidation has been described after the use of an iron-based black pigment.[41]

Currently, most surgeons prefer to use third-generation micronized pigments (Biotic Phocea; Marseille, France) or fourth-generation micronized pigments (Neoris; Paris, France), with particles smaller than 2.5 μm in size. This is believed to induce less foreign body reaction and is more stable through time.[31]

Safety and complications

There has been considerable controversy surrounding the application of KTP, particularly for strictly aesthetic purposes. Much of this apprehension stems from previous experiences with techniques aimed at altering the apparent color of the eye, especially artificial iris implantation, which has led to severe cases of blindness and other complications.[42] Nevertheless, it must be stressed that current literature suggests that KTP, especially femtosecond-assisted KTP, is a “safe and relatively uncomplicated surgical method.”[1] Most KTP patients have a very safe surgery and are satisfied with the result.[35] In normal-seeing eyes, most patients retain an unaltered visual acuity after undergoing femtosecond-assisted KTP.[30] In normal-sighted eyes undergoing KTP for strictly cosmetic reasons, patient satisfaction is around 92.5%.[18]

Although pain, glare, and dry eyes are common symptoms following femtosecond-assisted KTP, approximately 50% of these symptoms resolve within 48 hours post-surgery. For those who continue to experience symptoms after this period, the average duration is about 7 days.[43]

A frequent criticism voiced by ophthalmologists is the concern that examining the eye or performing surgeries, such as cataract surgery, after FLAAK may be impossible. However, a recent article by Alafaleq et al.[28] demonstrates that ocular examination of the retinal periphery and the iridocorneal angle is indeed feasible and relatively unhindered [Fig. 6]. Additionally, cataract surgery has been successfully conducted following FLAAK, utilizing a central 5-mm diameter FLAAK pupil. For further insights, please refer to the video link: https://youtu.be/QklbE4oXw6A?si=K13SxwVAWj4zPJWo.

Figure 6.

Photograph demonstrating the feasibility of performing gonioscopy in patients who have undergone femtosecond-assisted keratopigmentation

A study by Yilmaz et al.[44] compared the conjunctival microbiota of patients who had undergone corneal tattoo by a superficial automated KTP technique and compared it to normal control subjects and to subjects with corneal leucoma without tattoo. No statistically significant differences were detected in conjunctival microbiota between the groups, suggesting that corneal tattoo does not increase the risk of infections during or after the procedure.

An important consideration associated with the FLAAK surgery is the need for a touch-up procedure at a later date. In a study by Alió et al.[31] including seven patients who underwent purely cosmetic KTP, a total of four cases (57.1%) required a color retouch “to improve the outcome, in three cases upon patients’ request and in one case upon recommendation by the surgeon.” Similarly, D’Oria[18] reported that 35.4% of eyes required at least one color reintervention, with 5.1% necessitating three color touch-ups. Both articles indicate that all patients were satisfied with the aesthetic results following the touch-up procedures.

Another complication that may be encountered is the migration of pigment into the pupillary zone, with a consequent decrease in vision quality. Cronin et al.[45] reported the case of a 45-year-old woman with a history of retinal atrophy and inferior iris coloboma, who underwent superficial manual KTP using a No. 75 beaver blade along with brown, grey, green, and white dyes in 1983. In 2010, she was referred for a decrease in visual acuity, which was later determined to be due to pigment migration into the 4-mm central clear zone. The patient subsequently underwent phototherapeutic keratectomy and a new dye application, resulting in an improvement in her symptoms.

A paper by Bromeo and Lim-Bon-Siong[46] reported a case of corneal melting related to a previously blind patient who underwent superficial manual KTP using a “carbon-based ink.” Histopathology of excised cornea demonstrated an “ulcerative type of keratitis with massive infiltration of polymorphonuclear leukocytes.” Many kinds of pigments have been used in the published literature and appear to be mostly safe. Nevertheless, it should be stressed that ideally, all pigments used should be last-generation ones, with proven biocompatibility.

To the best of our knowledge, only one complication has been described to date in FLAAK.[18] The patient, whose ocular history was positive for a history of previous LASIK surgery, developed bilateral and progressive corneal ectasia with a 1-diopter (D) increase in maximum keratometry after 6 months. The patient was successfully treated with standard epithelium-off corneal collagen cross-linking (CXL). The patient was stable throughout the 2 years of follow-up after the CXL procedure.

Alternatives to KTP

Currently, there are other two surgical techniques suggested to change the apparent color of the eyes.

Cosmetic iris implants have been used for functional, traumatic, or congenital iris deficiencies with good results.[47] In well-selected cases, these implants can greatly improve glare disability and improve quality of life.[48] Nevertheless, the off-label use of this kind of implant in phakic, normal eyes has proven to be extremely dangerous and unsafe. Potential complications are sight-threatening and include corneal decompensation, intraocular pressure elevation, uveitis, and hyphema.[49] Anderson et al.[50] reported two cases of patients who underwent NewColorIris implantation in Panama, later suffering from multiple complications, including severe endothelial cell loss, bullies keratopathy, anterior uveitis, and hyphema. In a rather large study by Ghaffari et al.,[51] the most common necessary surgeries to remedy sequelae after artificial iris implantation were cosmetic iris removal (79.2%), cataract extraction (29.2%), corneal transplantation (29.2%), and glaucoma surgery (16.7%). Nowadays, most surgeons agree that purely cosmetic iris implants have no role in current Ophthalmology.

Another surgical option is depigmentation of the iris by use of a frequency-doubled 532-nm Nd: YAG laser. Initial animal studies[52] suggested this approach to be safe and effective, with only mild transient inflammatory signs after surgery. This same laser was used to manage a case of congenital sectorial heterochromia in an otherwise healthy 22-year-old patient.[53] The patient received two sessions of laser treatment, each one composed of 100 shots per day for 3 days straight, followed by a rest period of 1 month. The spot size used was 400 μm, with an energy level of 0.5 J. After two complete sessions (600 shots in total), the color difference was found to disappear, achieving a solid eye color. The only complication was mild anterior uveitis which resolved after 3 days. A paper by Grimaldos-Ruiz[54] evaluated laser iris depigmentation in 1176 eyes, finding a satisfaction of 95%, with the only complication being mild anterior iritis in 25% of patients.

A number of recent papers have described complications with laser iris depigmentation. Ferrari[55] reported the case of a patient who suffered iris perforation secondary to Nd: YAG laser iris depigmentation. Ning et al.[56] reported a case of “bilateral secondary pigment dispersion syndrome following laser burns to the irises for cosmetic purposes.” A case of secondary pigmentary glaucoma in a young patient after laser iris depigmentation for aesthetic reasons has also been reported by British authors.[57] Finally, a case of laser-induced maculopathy after iris depigmentation has been reported by Flores-Marquez et al.[58]

So far, the primary concern regarding laser iris depigmentation is the limited amount of evidence available to support its safety. This technique appears to be performed in only a few countries, yet most surgeons have not published any studies, and many of the protocols remain confidential. As a result, it is impossible to assert whether this technique is safe or to determine the optimal nomograms for treatment. Until more information becomes available and surgeons are more transparent about their methods and outcomes, laser iris depigmentation will continue to be viewed as an underground procedure that is difficult to trust.

Conclusions

KTP represents a safe and effective surgical intervention for various clinical scenarios. Recently, femtosecond-assisted KTP has gained prominence, particularly for strictly cosmetic purposes among patients seeking to change the apparent color of their eyes. Despite some controversy, studies have shown femtosecond-assisted KTP to be a very safe procedure with a benign safety profile and high levels of patient satisfaction. This surgery can be a viable option for normally sighted patients seeking a cosmetic enhancement of their eyes. At present, there is a lack of long-term evaluation studies assessing the outcomes of KTP. This is likely attributable to the relative novelty of the technique, particularly in cases performed for strictly cosmetic purposes. It is essential that future studies address this gap in the literature by systematically evaluating the long-term safety, stability, and patient satisfaction associated with KTP. Such evidence will be crucial for informing clinical guidelines and ethical considerations, especially as the demand for cosmetic eye procedures continues to grow.

Disclaimer

The authors wish to disclose that this article was reviewed for grammar and clarity using ChatGPT version 4o. The content was entirely written by the research team, and artificial intelligence was employed solely for the purpose of language refinement. The final version has been carefully reviewed and approved by all authors to ensure the accuracy and integrity of the information presented.

Conflicts of interest

FF is a pioneer of the Femotosecond assisted keratopigmentation procedure. He is a major shareholder in the Neoris company. He is the owner of two related patents: WO2018224791 - devices and method for preparing and carrying out corneal tattoos and WO2018122537 - Surgical Hand Instrument.

Funding Statement

Nil.