Management of an intrastromal corneal epithelial cyst, from simple drainage to keratoplasty.

It is believed that the first stage in pathogenesis of a corneal epithelial cyst is the displacement of epithelial cells into corneal stroma. The subsequent proliferation of these epithelial cells may form an intrastromal cyst that is outlined by squamous epithelium. Trauma and developmental causes have been proposed in the pathogenesis of corneal cysts, of which the former seems more plausible.[1-3] In approximately 50% of the reported cases a specific traumatic event was present by which epithelial cells were introduced into corneal stroma.[4] Even in cases without noticeable history of corneal trauma, an undetected minor injury in the past can be considered.[5] These rare lesions may sometimes present as a corneoscleral cyst. Corneal cysts may occur in a wide range of age, from birth to late adulthood.[1-5]

Generally, surgical intervention is indicated in the case of visual loss, threatened visual axis and progressive cyst enlargement. Otherwise, a conservative management is preferred. There is no specific agreement which surgical approach leads to the best outcome. Moreover, a major challenge of surgical management of corneal cysts is their frequent recurrence after the operation. Several surgical intervention have been suggested, including simple cyst aspiration and drainage, cyst wall excision, treating of cyst cavity by distilled water or balanced salt solution, chemical and electrical cautery, cryotherapy, and lamellar or penetrating keratoplasty.[1-8] Also, chemical solutions have been suggested for the destruction of epithelial cells including 10% acetic acid, 1% iodine, cocaine, 20% trichloroacetic acid, and 96% ethanol.[9] Herein, we present a case of a large intrastromal corneal epithelial cyst that has been successfully treated after multiple surgical interventions.

A 10-year-old girl presented with the chief complaint of appearance of cornea in her left eye since 4 months of age. Patient had no history of ocular surgery and/or trauma. Her family history was unremarkable. At first examination, her best-spectacle corrected visual acuity (BSCVA) was 20/20 bilaterally. Slit-lamp biomicroscopy revealed a vascular, creamy colored, cystic lesion in temporal half of the left cornea – extending from limbus to the pupil margin – with anterior to deep stromal involvement. At that time, the lesion was 5 and 8 mm in diameter [Figure 1a]. Other findings of ocular examination were otherwise unremarkable. Because the corneal cyst had threatened patient's visual axis, surgical intervention was planned. In the first operation, cyst was drained, debrided, and its wall was curetted mechanically through a 2.0 mm partial-thickness limbal incision. Cytological examination of cyst fluid revealed numerous epithelial cells.

Figure 1

Slit-photo shows a vascular, creamy-colored cystic lesion in the temporal half of the left cornea with stromal involvement at first presentation (a) and before keratoplasty (b), anterior segment OCT showed extension of the corneal cyst cavity to near the descemet membrane (c), slit photograph of the cornea 2 weeks (d) and 9 months (e) after penetrating keratoplas

Twenty-one months after the first operation, we noticed recurrence of the cyst for which a second surgery, simple drainage, was done. But, the cyst did not show satisfactory regression and during 2-year follow-up, it gradually enlarged and involved temporal half of visual axis. Diameters of the cyst increased to 6 × 10 mm [Figure 1b]. The anterior segment OCT (AS-OCT; Visante, Carl Zeiss Meditec) revealed extension of the cyst cavity to near the descemet membrane [Figure 1c]. Due to decrease in BSCVA (20/50 Snellen scale and refraction of plano –2.5 × 160 diopter), extension of cyst cavity into deep cornea (adjacent to descemet membrane) and involvement of visual axis, lamellar keratoplasty was planned. Patient's cornea was partially trephined (350 μm) with a disposable 8 mm Hessburg-Barron vacuum trephine (Jedmed, St. Louis, MO). Then, we tried to dissect anterior corneal stroma “layer by layer.”. But due to a major perforation of posterior corneal lamella, the operation technique was converted to penetrating keratoplasty (PKP). Donor's cornea was cut from endothelial side with a 8.5 mm Hessburg-Barron punch and sutured to recipient's cornea with sixteen interrupted 10–0 nylon sutures. Anterior and posterior walls of the remaining cyst cavity in temporal rim of the cornea were opposed by four 10–0 Prolen sutures [Figure 1d].

Nine months after the operation, no recurrence was noticed [Figure 1e] and BSCVA of the left eye improved to 20/30 with refraction of plano –5 × 110. Patient's visual acuity remained stable without recurrence of the cyst during the 20 months follow-up period.

Intrastromal corneal epithelial cysts are rare lesions. Pathogenesis of corneal epithelial cyst includes displacement of epithelial cells into corneal stroma and subsequent proliferation of these cells. Probably due to greater turnover of surface epithelium in children than adults, majority of reported cases had occurred in children.[1-3] In rare instances, cyst may disappear spontaneously, probably by spontaneous drainage into anterior chamber.[5] In most cases, cysts are single and have round to oval configuration. Some cysts have solid dense creamy-white materials like in our case. Other ones may contain aggregation of epithelial debris in lower portion of the cyst resulting in a pseudohypopyon.[14] If visual axis is threatened or involved by a corneal epithelial cyst or cyst progressively enlarges, surgical intervention may be required. Simple drainage procedure or aspiration can be performed but in near all cases, cysts recur within short time.[2310] Excision of the anterior cyst wall with or without destruction of epithelial cells by chemical agents can reduce the recurrence rate.[39]

Cytodestruction with chemical agents can be combined with suturing of cyst cavity or excision of its interior wall. In advanced cases, especially when lesions extend to deep corneal stroma and involve significant portion of visual axis, lamellar or penetrating keratoplasty may be required.[67] Our case had recurrence after the first two operations. Cytodestruction with chemical agents may probably resolve the cyst. But in case of visual axis involvement like our case, remaining opacity after cytodestruction can limit vision restoration. Also, risk of penetration of chemical agent into anterior chamber is present when cyst extends to deep stroma. Therefore, we decided to perform lamellar keratoplasty. But due to extension of cyst wall to near descemet membrane, posterior corneal stroma perforated during lamellar dissection and surgery was converted to penetrating keratoplasty. Cyst formation in anterior chamber was reported after penetrating keratoplasty.[8] Therefore, surgeons should destroy epithelial cells before penetrating keratoplasty with massive irrigation or cryotherapy.[10] In our case, because majority of the cyst wall was removed before entry to anterior chamber and remaining corneal bed was irrigated massively and repeatedly during lamellar dissection, probably no epithelial cells had entered to anterior chamber. We had no recurrence of cyst in cornea and anterior chamber up to 20 months postoperatively.

Although lamellar or penetrating keratoplasty are associated with several disadvantages and necessitate long term follow ups, it is advisable to use keratoplasty in refractory corneal cysts with deep stromal extension and/or visual axis involvement to both eradicate the cyst and achieve better visual outcome.