Introduction

Corneal keloids were initially described by Szokalski in 1865 [1, 2], as an uncommon ocular condition. These lesions are characterized by single, elevated, white growths on the cornea, often exhibiting a glossy appearance, resulting from abnormal wound healing processes [3]. They may vary in vascularity and thickness and typically exhibit well-defined borders. Keloids can manifest at any age, ranging from congenital cases to those occurring later in life. While most cases are associated with corneal trauma or disease [4,5,6], there are documented instances of primary corneal keloids in individuals without such antecedents, often appearing months to years after an inciting event.

Diagnosis is confirmed through biopsy and histopathological examination, revealing hyperplastic changes in the corneal epithelium and abundant, irregularly arranged collagen bundles along with activated fibroblasts in the stroma [1, 3, 7]. Surgical intervention is often required for clinically significant cases affecting vision; however, the outcomes of such procedures vary considerably from case to case [3]. We present a comprehensive analysis of the clinical characteristics, surgical management outcomes, and histopathological findings related to a corneal keloid developed in a patient with a history of ocular trauma, corneal decompensation, and an endothelial transplant.

Case presentation

A 35-year-old male with a five-year history of vision loss in the right eye (RE) was referred to the Cornea Department at Instituto de Oftalmología Conde de Valenciana. The patient had a prior ocular trauma to the same eye that required an Ahmed glaucoma valve (AGV) implantation for intraocular pressure (IOP) management. Subsequently, the eye experienced corneal decompensation one year after valve implantation, leading to the performance of Descemet’s Stripping Automated Endothelial Keratoplasty (DSAEK) with repositioning of the shunt tube. Initially, the patient reported good visual acuity (VA) for two years post-procedure; however, he then began to develop a small central opacity accompanied with loss of vision, which progressively worsened over the subsequent two years. Ophthalmological examination revealed a best-corrected visual acuity (BCVA) of Hand movement in the RE and 20/20 in the left eye (LE). Furthermore, there was a well-circumscribed elevated white opaque lesion involving the central corneal surface of the RE (Fig. 1). Anterior segment optical coherence tomography (AS-OCT) was performed, revealing a lesion on the cornea that was separated from the corneal epithelium by a distinct plane. However, detailed visualization was limited due to posterior shadowing of the lesion. Ultrasound biomicroscopy (UBM) showed a hyperechoic lesion extending from the corneal surface to the superficial stromal layer, measuring 1300 μm in thickness (Fig. 1). Additionally, an increased central corneal thickness of 770 μm was noted. While the UBM lacked detail due to posterior shadowing, the DSAEK graft was discernible with poor definition. No abnormal findings were identified in the posterior segment by ocular B-mode ultrasonography (US). Based on the patient’s clinical history, slit lamp examination, and UBM findings, the presumptive diagnosis of corneal keloid was established.

Fig. 1
figure 1

A, B. Clinical photographs showing a well-circumscribed elevated white opaque lesion involving the central corneal surface on the RE. C, D UBM showed a hyperechoic lesion extending from the corneal surface to the superficial stromal layer, measuring 1300 μm with an increased central corneal thickness of 770 μm. DSAEK graft was discernible with poor definition

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Superficial keratectomy was performed on the RE. Major portion of the lesion was detached from Bowman’s layer; however, a small portion infiltrated the stroma, resulting in corneal scarring and fibrosis (Fig. 2). The excised mass was immersed in formalin and subsequently submitted for a comprehensive pathological examination. After the procedure, the BCVA improved to 20/1600. However, 3 months later, the patient underwent a penetrating keratoplasty (PKP) to rehabilitate this eye.

Fig. 2
figure 2

A, B. Post superficial keratectomy intervention, the cornea showed remnants of fibrosis

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Histopathological examination of the excised corneal sample revealed variations in the thickness of the surface epithelium, alternating areas of hyperplasia or irregular acanthosis with areas of decreased number of layers. Numerous cells in the basal layer showed intracytoplasmic edema with the formation of small epithelial bullae. The Bowman layer showed discontinuity throughout much of its extent. The stroma presented variations in thickness, irregularity in the arrangement of the lamellae, numerous reactive keratocytes alternating with thick bands of collagen arranged in an irregular and disorganized manner, more evident with Masson’s trichrome staining (Fig. 3). Congo red staining was negative, ruling out the presence of amyloid. Descemet’s membrane and endothelial cell layer were not identified. There was no adhesion of the uveal tissue to the posterior surface of the cornea.

Fig. 3
figure 3

A, B. Marked irregularity in the thickness of the epithelium, complete disruption of Bowman’s layer and stroma with loss of the normal laminar pattern, erratic collagen bundles interspersed with some keratocytes (A. H&E and B Masson’s trichrome, original magnification 10x)

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Discussion

Corneal keloids exhibit similarities with skin keloids, likely stemming from excessive production of collagen by activated corneal fibroblasts [8, 9]. Unlike hypertrophic scars, which are confined to the area of the original injury, keloids have the potential to extend beyond the initial lesion, spreading across significant portions of the corneal surface, and they are frequently noted to recur [9]. While existing reports do not suggest a direct correlation between a predisposition for corneal keloid development and skin keloids [10], recent cases have reported corneal scarring after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) in Caucasian patients with a history of skin keloid formation [11, 12]. Moreover, keloids have been documented following superficial keratectomy (SK) in patients without known risk factors [13]. However, they are significantly less common than skin keloids and are often associated with ocular trauma, a history of penetrating or non-penetrating surgery, or, in some cases, rare diseases such as Lowe’s syndrome and Rubinstein–Taybi syndrome [1, 14,15,16]. Corneal keloids have been reported more frequently in men [7]. In our case, the patient, a male, had a history of trauma necessitating a valve implant procedure, which led to endothelial failure, requiring endothelial transplantation.

Diagnosing corneal keloids can be challenging due to various terms used interchangeably, including corneal fibroma, myofibroma, and hypertrophic scars. Additionally, it can be easily mistaken for other conditions such as corneal dermoid tumors, ocular surface squamous neoplasia, Salzmann’s nodular degeneration, limbal dermoid, sclerocornea, Peters anomaly, myxomas, congenital glaucoma with corneal edema, metabolic diseases like mucopolysaccharidosis and mucolipidoses, and corneal inclusion cysts [4, 8, 10, 17, 18]. A definitive diagnosis of corneal keloids fundamentally requires a biopsy and histopathological examination, revealing dysplasia of the corneal epithelium and hyperplasia of collagen fibers [4,5,6, 13]. Bowman’s layer is usually disrupted or absent [7].

Pathogenesis of this uncommon ophthalmic disorder remains unclear. Trauma and intraocular surgeries are well-established predisposing factors for keloid development. It is well-established that keloids can manifest several months or even years following these surgeries. Additionally, any of these events, individually or in combination, might serve as the source of the keloid. There have been reports of congenital corneal keloids without a history of ocular injury or trauma, no history of chronic inflammation, or a family history of fibrovascular proliferative disease [1, 10]. This proliferation may induce an inflammatory response in the corneal stroma, serving as a stimulus for the expansion of the fibrotic process beyond the limits of the corneal injury, a characteristic feature of corneal keloids [13, 19]. In our case, a male patient had a history of trauma that required a valve implantation, leading to corneal decompensation necessitating endothelial transplantation. Although the keloid didn’t appear until 2 years after the endothelial transplant, and it is difficult to determine the exact cause. We hypothesize that fibroblasts were activated following the DSAEK and tube valve repositioning. However, the keloid might also result from the initial trauma and subsequent surgeries.

Successful management of corneal keloids involves various surgical techniques, including superficial keratectomy, lamellar excision, lamellar keratoplasty, or penetrating keratoplasty, with favorable outcomes reported in several studies [3]. Recurrence of corneal keloids post-superficial keratectomy, photorefractive keratectomy, and penetrating keratoplasty has been observed [3, 13, 20]. Recently, successful management of corneal keloids with deep anterior lamellar keratoplasty was reported, highlighting the importance of removing the entire stroma to prevent recurrent corneal stromal opacification. Additional treatments post-surgery may include the use of amniotic membrane, corticosteroids, mast cell stabilizers, cyclosporine, laser therapy, and cryotherapy [12, 21]. The choice of treatment depends on factors such as lesion depth, surface area, and surrounding corneal conditions, with penetrating keratoplasty being recommended in cases with extensive corneal damage and endothelial dysfunction. Additionally, sclerokeratoplasty has emerged as a successful alternative procedure, particularly in cases where conventional keratoplasty is not feasible due to extensive corneal damage. In our patient, we observed endothelial dysfunction following the SK, leading us to perform a PKP.

In summary, corneal keloids should be considered in cases of corneal lesions characterized by a dense, white, glistening, and bulging appearance, which may or may not be vascularized. These lesions often arise following surgical procedures, corneal insults, or trauma and can manifest months or even years after the initial injury. While surgical intervention is a common treatment approach, it carries an inherent risk of recurrence.