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reported only 16 cases in the literature from 1971 to 2001. Once intrastromal progression of the epithelium within these lesions obscures the visual axis, surgical intervention is required. Known surgical methods include simple cyst aspiration and drainage, cyst wall excision, washing of the cyst cavity with distilled water or balanced salt solution, chemical and electrical cautery, cryotherapy, and lamellar or penetrating keratoplasty.
Unfortunately, surgery may induce negative visual consequences, and recurrence of these cysts is common.
Here, we report a case of an intrastromal corneal cyst after corneal laceration suturing surgery that was treated with deep anterior lamellar keratoplasty (DALK).
Case Report
A 25-year-old male was referred to our hospital complaining of mildly decreased visual acuity in his left eye. Ten years earlier he had suffered ocular trauma in his left eye from an awl (a small pointed tool used for piercing holes) and underwent corneal laceration suturing at a local hospital. His medical records showed a corneal opacity in the injured eye. During the previous 6 years, he had noticed a slow progressive growth of corneal opacity in the centre of this eye. He had no history of other diseases or medication use.
Ocular Examination
His visual acuity was 0.04 in the left eye. Anterior segment assessment, including slit-lamp biomicroscopy, anterior segment optical coherence tomography (AS-OCT; Visante; Carl Zeiss Meditec, Jena, Germany), and in vivo confocal microscopy (Heidelberg Retina Tomograph II with Rostock Cornea Module; Heidelberg Engineering, Dossenheim, Germany), was performed.
Slit-lamp biomicroscopy showed an avascular, cream-colored cystic lesion located in the centre of the left cornea, which extended from the anterior to deep stroma. The lesion was 6 mm in diameter, presenting a hypopyon-like appearance in the superior part of the cyst (Fig. 1). Some irregular small cysts (about 2 mm in diameter) with anterior adhesion of the iris could be seen at the 5 o’clock corneal limbus, which communicated with the central cyst. The pupil was not round because of a direction shift at the 5 o’clock corneal limbus.
Fig. 1Preoperative slit-lamp photograph showing an avascular, cream-colored cystic lesion in the left cornea extending from the anterior to deep stroma. Irregular small cysts can be seen at the 5 o’clock limbus, as well as anterior adhesion of the iris and communication with the central cyst.
AS-OCT revealed that the cyst cavity extended almost to the Descemet’s membrane (Fig. 2). In vivo confocal microscopy showed that the epithelium, anterior stroma layer, and endothelium of the corneal lesion were normal; a large number of Langerhans cells were observed in the subepithelial nerve fibre layer, and a scar was found in the posterior stromal layer (Fig. 3).
Fig. 2Anterior segment optical coherence tomography showing extension of the corneal cyst cavity near the Descemet’s membrane.
Fig. 3Corneal confocal microscopy of the left eye showing (A) normal epithelium of corneal lesion, (B) coarse subepithelial nerve fibre structure and a large number of Langerhans cells, (C) normal anterior stroma layer, (D) posterior stromal layer scar formation, (E) no pathogens, and (F) no abnormalities in the corneal endothelium of the peripheral transparent region.
We therefore made a diagnosis of an epithelial inclusion cyst secondary to epithelial infiltration of the stroma. Considering the location of this large corneal cyst and the potential influence on central visual acuity, we performed DALK for this patient.
Surgical Treatment
DALK was successfully performed by removing the corneal stroma of the involved eye and transplanting a donor button. The donor corneal button was from a donor eye preserved in the eye bank at our hospital. The cyst at the limbal margin was punctured by a 21-gauge needle. We carefully aspirated 0.1 mL of an opaque viscous fluid for pathological analysis.
The patient’s cornea was partially trephined with an 8.0-mm trephine. Then we dissected the corneal stroma layer by layer until the Descemet’s membrane was exposed. The remaining cyst cavity in the temporal rim of the cornea was drained and irrigated with balanced salt solution, and its wall curetted mechanically. The irregular small cysts at the 5 o’clock corneal limbus did not enter the anterior chamber. The donor corneal button (the same size as the removed endodermis) was sutured into the recipient bed using 10-0 nylon sutures and attached well to the recipient cornea. After the procedure, an antibiotic–steroid ointment was administrated, and the eye was patched and shielded.
Microscopy of the aspirate showed edematous epithelial cells together with a small amount of cell debris. Histology of the corneal lesions showed a distribution of monolayer and stratified epithelial cells in the corneal stroma, forming a cavity.
Figure 4 shows a histological section of the corneal lesion, which contributed to the pathological diagnosis of intrastromal corneal epithelial implantation cysts.
Fig. 4Pathological examination showing the distribution of monolayer and stratified epithelial cells in the corneal stroma to form a cavity.
After the surgery, minimal stromal haze and a little intrastromal blood were noted, temporally indicating an uneventful recovery for this patient. Two weeks after surgery, his best corrected visual acuity in the left eye was improved to 0.3 (Fig. 5). Follow-up at 6 months postsurgery showed no recurrence of the cyst, and the patient’s visual acuity remained stable.
Fig. 5Observation of the left eye under slit-lamp 2 weeks after deep anterior lamellar keratoplasty. Minimal stromal haze and little blood intrastromal are noted.
Intrastromal epithelial corneal cysts are very rare and mainly affect young people. Because of the obvious lesion, the intrastromal epithelial cyst is usually noted first by the patients or their parents.
Most lesions are unilateral, cream-white or yellow-white, and oval or circular (rarely loculated). Other lesions may contain aggregation of epithelial debris in the lower portion of the cyst, resulting in a pseudohypopyon. In our case, we observed the degenerated epithelial debris from the aspirated cyst contents under a microscope.
Trauma and developmental causes have been proposed in the pathogenesis of corneal cysts; the former seems more plausible. A specific traumatic event is believed to lead to the introduction of epithelial cells into the corneal stroma in about 50% of cases.
Then the seeded epithelial cells proliferate to form a cleavage plane in the collagen meshwork of the stroma. The gradual expansion eventually leads to the formation of a corneal cyst, as shown in our case.
With regard to treatment options, it is recommended that corneal cysts not affecting vision be treated conservatively, whereas corneal cysts that threaten the visual axis require surgical intervention. A simple drainage procedure or aspiration can be performed, but recurrence is common.
Excision of the anterior cyst wall can reduce the recurrence of cyst, independent of whether cytodestructive treatment is performed with chemical agents.
In our case, DALK was required as the lesions extended to the deep corneal stroma located in the centre of the cornea and a significant portion of the visual axis. The procedure retained the patient’s corneal Descemet’s membrane and endothelium, which is helpful for reducing the incidence of rejection and operative complications. The 6-month follow-up showed no recurrence of this disease in the patient’s left eye. To the best of our knowledge, this is the first case of an intrastromal epithelial cyst successfully treated with DALK. Zare et al. described the planning of DALK in the case of a 10-year-old girl with an intrastromal corneal cyst, but penetrating keratoplasty was performed because of a major perforation of the posterior corneal lamella.
Another report described a case of an anterior chamber epithelial cyst occurring after uncomplicated DALK that was treated with a tissue-sparing surgical technique.
Although DALK is associated with long-term follow-up and use of local eye drops, it is advisable to use keratoplasty in refractory corneal cysts with deep stromal extension and visual axis involvement to both eradicate the cyst and achieve a better visual outcome.
Disclosure
The authors have no proprietary or commercial interest in any materials discussed in this article.
Acknowledgement
The patient kindly consented to publication of the included images.
References
Bischler V.
Un cas de kyste congenital sclerocorneen [in German].
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