Managing a Case of a Congenital Cystic Eyeball: Case Report with Review of Literature

A congenital cystic eyeball is an extremely rare condition, with only 52 cases reported in the literature to date. An orbital cyst replaces the eyeball which occurs due to the complete or partial failure in invagination of the primary optic vesicle during the fourth week of gestation. We discuss a case of a congenital cystic eyeball in a 14-year-old female who presented to us for a cosmetic blemish due to a large swelling in the right eyelid with the absence of a right eyeball since birth. She underwent removal of the cyst followed by an orbital implant and later prosthesis. Diagnosis of the congenital cystic eyeball was made based on the clinical and ultrasound B-scan features, intraoperative findings, and histopathology report. This article adds one more case to the existing literature on the congenital cystic eyeball. Orbital implant with prosthesis after excision of the cyst provided definitive diagnosis and a good cosmetic outcome in our case.


Introduction
The congenital cystic eyeball (CCE) was first reported by Taylor and Collins in 1906 [1] and later explained in detail by Mann in 1939 [2]. Mann also coined the term "anophthalmos with cyst" for the congenital cystic eyeball [3]. A complete or partial failure in invagination of primary optic vesicle leads to the development of congenital cystic eyeball [4,5]. Noninvagination of the optic vesicle takes place in the middle of 2 mm and 7 mm phases of the embryonic development which usually occurs during the fourth week of gestation. The cyst which replaces the eye is formed due to the failure of the anterior primary optic vesicle to involute. It should be differentiated from microphthalmos with cyst which occurs due to the failure of fetal fissure closure at 7-14 mm phase, presents as a cyst in the anterior and inferior part of the orbital cavity, and is associated with a microphthalmic colobomatous eye. Cases of CCE are remarkably rare. To date, only 52 cases of congenital cystic eyeball have been reported in the literature [5][6][7][8][9][10][11][12]. We discuss a case of a congenital cystic eyeball in a 14-year female and also describe the clinical features, diagnostic tools, differentials, and the management approach for such cases through an extensive literature review. A 14-year female presented with a complaint of cosmetic disfigurement caused by a large swelling in the right eye (RE) since birth which was gradually increasing with her age. The patient was aware of no vision from that eye. There was no history of perinatal complications or consanguineous marriage. On examination, the vision in RE was no perception of light (NPL) whereas the vision in the left eye (LE) was 1/60 on the Snellen distant visual acuity chart. RE examination revealed a large cystic swelling predominantly in the lower eyelid but no visible eyeball in the palpebral aperture ( Figure 1). The swelling was single, soft, smooth, bluish-tinged, nontender, nonpulsatile, and brilliantly transilluminating ( Figure 1(b)). The bony orbital rim was normal. Examination of the LE suggested a microcornea, inferior corneal scar, iris coloboma, and chorioretinal coloboma involving the optic disc and macula ( Figure 1). The patient underwent B-scan ultrasonography (USG) which demonstrated a large cyst in the right bony orbit with no evidence of a well-formed eyeball. Typically, a stump of the optic nerve-like structure was seen in the posterior aspect of the cyst (Figure 1(c)). A provisional diagnosis of CCE was made based on the clinical and radiological findings. Pediatrician consultation was done, and neuroimaging was performed to rule out systemic associations especially intracranial abnormalities, which was normal. The patient and her parents were counseled regarding the nil visual prognosis and were advised for surgery. The patient had the cyst removed and an orbital ball implant and a conformer placed, and inferior fornix was reconstructed using sutures. The cyst was sent for histopathological examination which revealed an irregular cyst lined externally by a connective tissue layer and internally by glial tissues (Figure 1(d)) without a histologically identifiable eyeball, which confirmed the diagnosis of the congenital cystic eyeball. She was prescribed an ocular prosthesis after 6 weeks of surgery.

Discussion
A congenital cystic eyeball occurs because of a developmental anomaly occurring during the third week of embryogenesis. An arrest in the invagination of the primary optic vesicles during the 2 mm-7 mm stage is attributed to this rare congenital anomaly [5]. Though the etiology of CCE is unknown, some authors have related it to an inflammatory cause due to the presence of inflammatory cells in the histopathological picture of the cystic eyeball [5].
Cases are usually unilateral, although few bilateral cases have been described in the literature. A case of bilateral congenital cystic eyeball was reported by Sacks and Linderberg. In two cases reported by Hayashi et al., one had bilateral involvement although the nature of the lesion was not established [13]. The patients usually present with a swelling in the eyelid of the involved eye since birth. However, the cyst may not be evident at birth in some cases. Such patients present with an absence of the eyeball and later with a cystic swelling when the cyst progressively enlarges due to the continuous production of fluid into the cyst probably from the neuroglial tissues. This fluid can be dark viscous, serosanguineous, or proteinaceous [13,14], but the fluids usually have similar biochemical properties as the serum [15].

Case Reports in Ophthalmological Medicine
Diagnostic workup for a case of CCE starts from the examination of the eyes and orbits and extends to the whole body to rule out systemic associations which may be lifethreatening. In infants, the cyst can be examined properly using eyelid retractors, such as Desmarre's, to look for the presence of a microphthalmic eye which is the most important differential diagnosis. Where congenital cystic eyeballs have the complete absence of a globe, microphthalmos with cyst usually has a small eyeball and the cyst is attached to the sclera or choroid [11,16]. Incomplete closure of the fetal cleft leads to microphthalmos with cyst which often has coloboma of uveal tissue, lens, and retina. Cysts are generally placed in the inferior orbit. Inversely, a congenital cystic eyeball typically causes the upper eyelid to bulge, and there is the presence of a pedicle. However, there are some exceptions where the lower eyelid bulges in a congenital cystic eyeball [13,17]. In our case, the cyst was located in the inferior part of the orbital cavity presenting as a swelling in the lower eyelid.
The fellow eye in our case had microcornea with an inferior corneal scar and, iris, and fundal coloboma. As anophthalmos and microphthalmos (with or without cyst) and uveal coloboma-all are congenital abnormalities occurring due to the failure of invagination of optic vesicle at various stages of development of ocular structures, these are often found in association. Tucker et al. found abnormal second eye in 21% cases of unilateral anophthalmos without a cyst [18]. Although the data with anophthalmos with cyst is limited, we can take reference from the largest case series of anophthalmos with cyst by McClean et al. [19]. In their case series of 34 cases of orbital cysts associated with anophthalmos or microphthalmos, they have described 14 cases of anophthalmos with cyst wherein 5 cases were unilateral with fellow eye normal, 3 cases had microphthalmos in fellow eye with or without uveal coloboma, 3 cases had anophthalmos without a cyst in fellow eye, and the remaining 3 had bilateral anophthalmos with cyst. There were 2 cases described in the case series where the fellow eye had both microphthalmos and uveal coloboma similar to our case. Similarly, Hayashi et al. [13] reported a case of congenital cystic eyeball with microphthalmos in the fellow eye. Hence, our case report is rarer in view of involvement of fellow eye with microphthalmos and uveal coloboma.
Radiological investigations such as B-scan ultrasonography (USG), computed tomography (CT) scan, or magnetic resonance imaging (MRI) form the logical next step in the diagnosis of CCE. B-scan USG is usually readily available at the ophthalmology outpatient department and gives valuable information about the cyst, absence or presence of an eyeball, and an associated optic nerve-like stump. Cysts may be replaced partially or even completely by neuroglial tissues [20]. Baghdassarian et al. found a 2 mm round structure posteriorly, resembling an optic nerve at the posterior aspect of a cyst [21]. We also found a small round stump of an optic nerve-like structure at the posterior part of the cyst in our case on B-scan USG. Studies have revealed the presence of patent optic stalk [22]; however, there have been reports of nonpatent [23] or even absence of a posterior stalk [13]. Reports with CT scan or MRI frequently reveals a cystic mass in the orbital cavity which might be unilateral [24] or bilateral [20,25]. Microphthalmos and any optic nerve stalks will also be evident on CT or MRI. Usually, extraocular muscles are absent and cystic mass probably has a soft tissue component depending upon the amount of glial proliferation [4,25].
The mainstay of management of the congenital cystic eyeball is excision of the cyst followed by an orbital implant. Morselli et al. reported a case of the congenital cystic eyeball where they followed up the case serially from 20 weeks of gestation till birth [26]. The case was managed by a multidisciplinary team of ophthalmologists, plastic surgeons, pediatricians, and neurosurgeons. Guthoff et al. reported a congenital cystic eye in a 1-month healthy infant, where during excision of the mass, yellow serous fluid was released [27]. A spherical silicone orbital implant was inserted. The optic nerve was not identified in this study. Holland et al. removed the cyst in a case of the congenital cystic eyeball and replaced it with a bioceramic implant [12]. Our case, an early teenage girl, underwent excision of the orbital cyst with an orbital implant and conformer by an oculofacial plastic surgeon. After 6 weeks, an ocular prosthesis was prescribed for cosmetic rehabilitation.
An irregularly shaped cyst with a connective tissue layer externally and an inner neuroglial tissue layer is the common histopathological picture in CCE. There is no presence of epithelial linings of cysts in the CCE and microphthalmos with cyst, and thus, they are similar in histopathology [28]. However, the absence of a small developed eyeball and the lack of surface ectodermal elements are the main features for differentiating CCE from microphthalmos with a cyst. Our case had features suggestive of CCE without an identifiable eyeball on histopathology.
Although CCE usually does not have associated nonocular abnormalities, some bilateral congenital cystic eyes [17,29] and unilateral congenital cystic eye [28] with nonocular anomalies have also been reported. Some of these may have intracranial abnormalities such as agenesis of the corpus callosum, midbrain deformity, and basal encephalocele [4,13]. Furthermore, grey matter heterotopias with corpus callosum agenesis have also been illustrated in MRI [7]. Studies have described the presence of intracranial abnormalities in CCE which required ventriculoperitoneal shunting [4,11,25,29,30]. Hence, cases of microphthalmia and anophthalmia with or without a cyst need radiological investigation especially neuroimaging to rule out systemic associations such as intracranial abnormalities. Ragge et al. in their review of management of anophthalmia and microphthalmia have described the frequent association with ocular abnormalities and infrequently with nonocular abnormalities such as CHARGE syndrome [31]. Similarly, Das et al. have recently reported a case of congenital cystic eyeball with associated intracranial abnormalities in a 15-day-old girl [32]. A full list of cases reported till date is shown in Table 1 which demonstrates the frequency and the type of the ocular and systemic associations. Our case was reviewed by a pediatrician before the surgery which revealed no neurological abnormality. Studies to date have 3 Case Reports in Ophthalmological Medicine       [4,13,17,30]. Clinical assessment and radiological investigations aid in the confirmation of the diagnosis of CCE. However, a definitive diagnosis can only be made through histopathology. Removal of the cyst followed by an orbital implant, conformer, and later on ocular prosthesis seems to be the appropriate management approach for CCE.

Data Availability
No datasets were generated or analyzed during the current study.

Consent
Written informed consent was obtained from the patient's legal guardian for the publication of this case report and any accompanying images. A copy of the written consent is available for review by the editor-in-chief of this journal.