Therapeutic Keratopigmentation: Cosmetic and Functional Outcomes

Keratopigmentation (KTP), commonly called corneal tattooing, is an ophthalmic procedure that has the potential to be utilized for both therapeutic and cosmetic goals. Both the cosmetic and therapeutic (functional) aspects of KTP are beneficial to eyes that have been altered in appearance due to corneal opacifications (leukomas) and iris abnormalities caused by various pathologies. Using this technique, pigments are applied to the cornea to alter its cosmetic appearance or treat vision problems caused by iris abnormalities. The efficacy and safety of KTP have been enhanced by the development of micronized mineral pigments and advancements in surgical methods, particularly the use of modern technologies like femtosecond lasers [1‐4, 8, 11, 15]. KTP has shown encouraging results in treating patients with moderate-to-severe visual impairments by reducing light scattering and photophobia in subjects with aniridia or iris coloboma and in patients with symptomatic glare related to iris loss, atrophy, or trauma [2, 5‐7, 12, 13]. Moreover, KTP has even been applied for pure cosmetic purposes, allowing healthy individuals to voluntary change the visible color of their eyes [9].

This procedure has previously been reported to achieve high patient satisfaction in terms of both cosmetic and symptomatic relief, along with successful cosmetic and functional outcomes and minimal complications [8‐11, 14, 15]. KTP frequently eliminates the need for anterior chamber invading (intraocular) procedures in order to improve the cosmetic appearance of the eye, such as iris implants, iris reconstructive surgeries, and keratoplasty, bypassing their potential serious complications like endophthalmitis, increased intraocular pressure (IOP), and uveitis [11]. Historically, KTP has been used for managing disfiguring corneal opacities, and a thorough review of the procedure demonstrates its expanded clinical applications because of low complication rates and advancements in surgical techniques [12, 13].

KTP techniques have advanced significantly by innovation of automated pigment-delivering devices and evolution of femtosecond laser technology for creating intrastromal pockets, providing a range of methods for both cosmetic and functional purposes. These techniques are divided into two categories: superficial and intrastromal. Superficial manual keratopigmentation (SMK) and superficial automated keratopigmentation (SAK) are categories within the superficial KTP. Manual intrastromal keratopigmentation (MIK) and femtosecond laser-assisted intrastromal keratopigmentation (FIK or FAK) are the two subtypes of the intrastromal technique [14, 15]. Each technique has its own advantages and indications, but their overall goals are to improve the eye’s cosmetic appearance or treat functional impairments brought on by iris defects and corneal conditions. Technique selection usually takes into account the needs of each patient, the degree of corneal involvement, and the intended cosmetic result.

The aim of this study is to assess the safety and cosmetic and functional outcomes of KTP (SAK and FIK) using micronized mineral pigments (MMP) in patients with moderate-to-severe cosmetic or visual impairment who have visual symptoms, cosmetic complaints, or both.

A total of 85 eyes from 85 patients, including 48 males and 37 females, were reviewed. The mean age was 37.8 ± 14.25 years (range, 14–77 years). Visual acuity status of the eyes and causes of visual or cosmetic complaints are shown in Tables 1 and 2. All patients were unsatisfied with their eye appearance. Twenty-one patients experienced visual symptoms, including photophobia, glare, halos, and monocular diplopia, in addition to cosmetic concerns due to iris abnormalities. Patients were assigned to receive either superficial automated keratopigmentation (SAK) or femtosecond laser-assisted intrastromal keratopigmentation (FIK) based on pre-operative evaluations. Forty-six eyes underwent SAK, while 36 eyes received FIK. Three eyes underwent a combined SAK + FIK procedure. Additionally, 13 eyes required superficial keratectomy with 2% EDTA to remove calcified band keratopathy. The mean follow-up period was 13.06 ± 9.9 months (range, 6–53 months).

Results of the study demonstrates that superficial and intrastromal KTP with micronized mineral pigments (MMPs) are considered safe procedures if the selected technique matches the underlying pathology (based on pre-operative evaluations) and is done by an experienced surgeon.

The cornea can be colored by embedding coloring agents or reducing metallic salts in situ into the corneal stroma. Toxic reactions to the pigment, color fading, color change, and over- or underpigmentation are the main complications that come with these agents [16, 17]. Sirerol et al. evaluated the tolerance and biocompatibility of MMPs in an animal model (leghorn hens) and concluded that a good cosmetic appearance without any negative effects was displayed by central KTP [16]. Another in vitro study by Amesty et al. in an experimental animal model (New Zealand rabbits) reported the same results [17]. The findings indicate that MMPs are suitable for achieving successful KTP. Advantages of using MMPs are less foreign-body reaction in comparison to traditional tattoo inks and a wide range of available colors primarily or by mixing colors [16, 17].

No intra-operative complication occurred during the study. Except for one case, which developed bacterial keratitis, no eye developed serious post-operative complications necessitating aggressive treatment. The most common post-operative symptom was photophobia (28.2%), followed by tearing (23.5%), and pain (8.2%). Most cases with such symptoms were in the SAK group. Salini et al. found that the intrastromal needle puncture technique (ISNT) caused more watering and redness (p > 0.001) than the intrastromal pocket technique (ISPT), which was resolved in 70.4% of patients after 4 weeks [18]. Invading the most anterior parts of the cornea, including the epithelium, Bowman’s layer, and nerves during SAK, may lead to delayed epithelial healing, recurrent epithelial erosions, dry eye, and pain. This may explain the higher occurrence of postoperative symptoms in the SAK group. Moreover, the corneal conditions in the SAK group were mostly the ones where the corneal layers were previously damaged, causing the post-operative symptoms to be more frequent in the SAK group.

Post-operative complications were rare in the present study (9.4% in total) with the most common by 5.8%, which was filamentary keratitis. Post-operative symptoms were photophobia (light sensitivity) in 28.2%, tearing in 23.5%, and pain in 8.2%. Alio et al. reported the first cases of performing intrastromal KTP using MMPs in a case series including seven patients [8] and then studied and reported the outcomes of 234 eyes that received KTP with various techniques and reported the complication rate as 12.82% [15]. The most common complication of their study was light sensitivity (49% of complicated eyes), whereas the least ones were visual field limitation and magnetic resonance imaging (MRI), alterations that occurred in 4% and 2% of complicated eyes, respectively. Other reported complications were color fading, change in color (both 19% of complicated eyes), and neovascularization (7% of complicated eyes). The rate of pigment fading in our study was 20% of all eyes, which occurred, on average, 3.35 months after the initial procedure. Differences in study population regarding the underlying pathologies and differences in number of SAK and FIK procedures between the two studies are the reason for different post-operative complications and symptom rates. Yilmaz et al. studied 42 eyes that had colored corneal tattoos applied with an automated tattoo pen machine for aesthetic reasons but had no visual potential. They reviewed pre- and post-operative (day 1, week 1, months 1, 3, and 12) slit photos of the patients and by utilizing an online Color Code Finder program, they determined red, green, and blue (RGB) and hue, saturation, and lightness (HSL) values of the tattooed areas, like pupil and iris. They stated that the first month was when the majority of the fading happened. The black-colored pupil's L value increased after the first month at a lower rate than the brown- or green-colored iris. Light colors fade more quickly, according to these findings [19]. A case of pigment migration into the optical zone was observed in an FIK patient 5 years after the procedure, with eye rubbing suspected as the primary cause. Therefore, advising patients to avoid rubbing their eyes after KTP procedures would be a reasonable precaution.

The results of the present study seem to confirm previous reports concerning the use of superficial and intrastromal KTP as effective procedures providing good cosmetic outcomes [1, 5, 8, 11, 14, 15]. The observer’s reported cosmetic outcome was excellent or good in 91.8% of all study cases. Cosmetic outcome was excellent or good in 91.4%, 91.5%, and 100% in SAK, FIK, and SAK + FIK groups, respectively, according to the observer’s reported cosmetic outcome 6 months postoperatively. Al-Shymali et al. studied 130 cases and reported excellent or good cosmetic appearance evaluated by the observer in 98.5% of eyes that underwent superficial KTP [14]. Eighty percent of the patients in our study were highly satisfied or satisfied with their cosmetic outcome in general. The rate of patient’s cosmetic satisfaction was 73.9%, 86% and 100% in SAK, FIK, and SAK + FIK groups, respectively. Unsatisfied patients were the cases where pigment fading occurred during the follow-up period. Twelve eyes in the SAK group (26%) and five eyes in FIK group (13.8%) needed to repeat the initial procedure due to color fading. All patients were highly satisfied or satisfied after the second KTP procedure.

We may conclude that after undergoing their first or, at most, their second KTP procedure, 100% of the study participants were highly satisfied or satisfied with their cosmetic result. Alio et al. studied 40 patients who underwent superficial or interlamellar KTP and reported that eight cases needed a second KTP after 1 year of follow-up and 95% of patients’ reported cosmetic satisfaction [11]. Another study of 16 eyes underwent MSK and MIK reported mean patient satisfaction score of 4.18 ± 0.75 points (range, 3–5 points), with a 0–5 points satisfaction grading system [20]. Salini et al. reviewed 463 patients who underwent either intrastromal needle puncture technique (ISNT) or intrastromal pocket technique (ISPT) during 7 years and reported excellent levels of satisfaction in 375 (80.9%) patients and good satisfaction levels in 45 (9.7%) patients; 5.3% of patients in the ISNT group required a repeat of the procedure [18].

The study showed that superficial and intrastromal KTP are effective procedures in treating visual symptoms related to iris abnormalities, a procedure that is called functional or therapeutic KTP. Of 21 patients with visual symptoms due to iris abnormalities, 16 were treated by FIK, three were treated by SAK, and two were treated by SAK + FIK; 100% of patients were highly satisfied or satisfied with their functional outcome. Several studies have demonstrated the effectiveness of KTP in functional improvement of the eyes with iris abnormalities for various causes [1, 2, 5‐7, 21]. Alio et al. reported improvement of visual function-related symptoms by manual intralamellar KTP (MIK), SAK, and FIK (FAK) in 11 eyes with moderate-to-severe visual disabilities due to iris defects [5]. Another study conducted on 19 eyes that had significant visual impairment due to iris defects and underwent FIK (FAK) revealed that all patients experienced an improvement in their prior visual-related symptoms, and 94% of the eyes showed an improvement in their best-corrected Snellen visual acuity [3].

The current study is one of the largest reported retrospective consecutive studies of cosmetic and therapeutic KTP using MMPs by including 85 patients after Alio et al.'s work in 2017 [15], which included 234 patients. Thus, the results of this study confirm the previously reported findings regarding the cosmetic and therapeutic outcomes of KTP using MMPs.

The retrospective nature of the study, non-randomized and non-controlled cohorts, and small sample size are some of its limitations.

In conclusion, according to the results reported in this study, SAK and FIK using micronized mineral pigments are confirmed as safe and efficient therapeutic surgical techniques for managing cosmetic and functional disabilities caused by corneal opacities of a variety of etiologies and iris abnormalities causing functional disabilities.