Tattooing of cosmetically disfiguring corneal scars may be a valuable therapeutic alternative in a distinct group of patients. This group comprises patients in whom reconstructive surgical procedures either will not result in functional improvement or carry the risk of phthisis. Besides this, increasing difficulty in wearing a printed contact lens or a bulbar shell or the reluctant attitude of the patient towards repeated surgery (or enucleation) may be of importance. Out of the numerous modifications reported for corneal tattooing, it is not easy to choose the optimal one. While the ancient method of impregnation1 seems problematic due to rather unpredictable staining,4 there is sufficient evidence that lamellar keratectomy procedures give excellent results in terms of a homogeneous application of colour.5–8 On the other hand, many scars do not allow lamellar keratectomy owing to irregularity, thinning, or calcification. Taking into account the individual corneal changes of our patients, we decided to choose the dermatography-like manner of tattooing. According to literature, this approach has two theoretical problems. Firstly, because of the multiple incisions into the corneal stroma, and thereby an activation of phagocytosis, its results may not be of long duration.3,4 Secondly, it has been thought that the multiple lacerations of Bowman's layer might promote recurrent corneal erosions7—though, on the other hand, stromal micropuncture is known to be a treatment in case of recurrent erosions.9 Despite these objections, the staining in our patients was still satisfactory even after more than 4 years; recurrent erosions were not observed. A surgical difficulty inherent to this technique is the risk of accidental corneal perforation. Fortunately, we did not observe any sign of intraocular irritation in those of our cases, in whom this took place; and this phenomenon has also been reported by others.10 A further problem encountered in one of our patients (no 2, Table 1) was the inadvertent excision of corneal tissue. Although in this particular case we believe that the described problem occurred as a result of the presence of very fragile scar tissue, it has to be emphasised that the direction of the punctures must not be changed under any circumstances in order to avoid this risk.
As corneal tattooing is not a frequent procedure performed in our department, we looked for a staining agent that was easily available and storable, avoiding the necessity of developing individual formulas in differing shades. Besides anecdotal reports on accidental but well tolerated incorporation of ink into corneal stroma,11 Holth reported very satisfactory results by using commercially available and sterilised drawing ink in different shades without any toxic effects.3 Sekundo and co-workers recently supported this assessment of ink as a well tolerated staining agent in their histological evaluation of specimens up to 61 years after corneal tattooing.12 These inks obviously are superior to the ancient china ink, which is well known to cause substantial inflammation.2,13 Nevertheless, despite of these reports and our own observation of lack of local or systemic toxicity, the composition of the ink used is a crucial point. As chemical analysis was not carried out, we cannot exclude possible toxicity. Owing to the manufacturer's stated policy we were able to obtain only incomplete information regarding this issue. Generally, these inks contain 85% water and 10% pigments. Soot particles achieve a black shade, the addition of pigment blue 15 (heliogen blue) a blue shade. These pigments are water insoluble. Therefore, absorption and systemic toxicity may be excluded. We were not provided with any information about the pigments added for the brown shade.
Only sparse information is available regarding preservatives. Black ink does contain chlorocresol, which is of lower toxic potential than other phenols and is commonly used in creams, external disinfectants,14 and even ophthalmic preparations.15 For emulsification, non-ionic surfactants are added. These substances otherwise are widely used in cosmetics, drugs, and food.14 The same holds true for shellac and 1,6-hexanediol, which are added for moisturising: Shellac is used as coating for pills and tablets,14,16 while polyalcohols like 1,6-hexanediol are known to be ingredients of ripe fruit.16 In summary, we consider the components of this ink to be of little toxic potential. However, different products may vary considerably in their composition. Therefore, we do not recommend using another ink from the one described in the present study and would hesitate to perform this procedure in sighted eyes.
In conclusion, the following two factors enabled the simple performance of corneal tattooing: the application of a standardised staining agent, and the use of a needle readily available in any ophthalmic surgical department. While we did not observe any relevant complications, the described method achieved surprisingly good results, not only from our, but also the patients', point of view.