Spark ImageWise 42

AS – OCT features in a case of limbal dermoid

Dr. Ravi Daberao , Dr. Prabhat Nangia, Dr. Sarang Lambat, Dr. Vinay Nangia 
Suraj Eye Institute, 559, New Colony, Sadar, Nagpur- 440001.

Case Description:
A male, 17 years of age, presented to us with chief complaint of a mass in the right eye since birth which was very gradually increasing in size and shape. There was no associated redness, pain or foreign body sensation. He had no history of trauma, infection, discharge, watering, diplopia or bulging of eyes. There was no history of any systemic illness. There was no history of significant weight loss, chemotherapy, radiation exposure or any intraocular surgery. His best corrected visual acuity (BCVA) was 6/9, N6 in the right eye (RE) and 6/6, N6 in the left eye (LE) with a correction of +1.25 DC × 100 degrees in RE and -0.75 DS in LE. The anterior segment examination of right eye showed an ovoid, well-defined mass which was firm in consistency, non-tender and non-mobile, at the temporal limbus encroaching over cornea. There was presence of hair follicles and cilia over the mass along with keratinized skin-like epithelial surface. LE anterior segment was normal. The intra ocular pressure was 15 mmHg in both eyes (BE). Fundus examination in BE was within normal limits.

Fig. 1 and 2: Right eye anterior segment examination showed ovoid, nodular, well defined mass at the temporal limbus which was encroaching over cornea. There was presence of hair follicles and cilia (blue arrow) over the mass with keratinized skin-like epithelial surface.
Fig.3 Right eye AS-OCT horizontal scan passing through mass lesion showed significant hyper reflectivity (white arrow), cilia (red arrow) with back shadowing involving 50% of corneal stroma (yellow arrow). Ocular surface squamous cell neoplasia (OSSN) was ruled out as it was not causing epithelial thickening which is typical feature of OSSN on OCT imaging. 

Diagnosis of right eye limbal dermoid was made. Patient was advised to undergo right eye dermoid cyst excision with corneal tattooing with amniotic membrane grafting using fibrin glue for cosmetic correction. After the surgery, close follow up was done along with AS-OCT imaging.

Fig.4 Right eye anterior segment examination on follow up day 1 showed amniotic membrane in place (blue arrow), tattoo pigment (yellow arrow), bandage contact lens (green arrow) but minimal conjunctival retraction noted (orange arrow).
 
Fig.5 Right eye anterior segment examination on follow up after 2 weeks showed amniotic membrane in place (blue arrow), tattoo pigment (yellow arrow) and bandage contact lens (green arrow).
Fig.6 Right eye anterior segment examination on follow up after 3 weeks showed amniotic membrane in place (blue arrow), tattoo pigment (yellow arrow)
Fig.7 Right eye AS-OCT horizontal line scan passing through the excised area on follow up after 3 weeks showed significant back shadowing because of corneal tattooing (white arrow), hypertrophic conjunctival tissue (yellow arrow) and remnant of dermoid (red arrow) .

Sample which was sent for histopathology showed epidermis of normal thickness and dermis containing coarse collagen fibres, hair follicles, sebaceous glands, vascular channels and adipose tissue which was consistent with diagnosis of dermolipoma.

Fig.8 (a) and (b) Histopathological specimen of lesion showed thin superficial stratified squamous epithelium (red arrow), pilosebaceous unit (green arrow), collection of lobules of benign adipocytes below the thin squamous epithelial linings (blue arrow), collagen fibres (black arrow) and vascular channels (pink arrow).

Discussion:
          Our patient came to us with typical features of limbal dermoid which was present since birth. We advised AS-OCT which is a noninvasive, high-resolution imaging technique to try to determine the extent of dermoid and its possible depth in the corneal stroma. AS-OCT showed a typical feature of hyperreflectivity with back shadowing because of the mass lesion without epithelial thickening. With AS-OCT, lateral boundaries were determined but due to local shadowing artifact, the posterior limit was uncertain. AS-OCT also helps in finding the extent of mass lesion in the corneal stroma before surgical excision.
           This was a small relatively asymptomatic grade 1 limbal dermoid. So initially, we advised clinical observation. However the patient was young, parents wanted a surgical correction for cosmesis. We also considered astigmatism present in the right eye. The patient was advised to undergo right eye dermoid cyst excision with corneal tattooing and amniotic membrane grafting using fibrin glue. AS-OCT imaging was also helpful in keeping close follow-up of the patient for any remnant of mass and corneal thinning.
           A limbal dermoid is a congenital benign choristoma, which comprises tissues of ectodermal and mesodermal origins. It consists of overgrowths of epidermal appendages, connective tissues, skin, fat, sweat glands, lacrimal glands, and neurologic tissues located partly over the cornea and partly over the sclera. It occurs most commonly in the inferotemporal quadrant as a solitary lesion but occasionally occurs as multiple lesions. It presents as an elevated yellow or white round mass overlying both the cornea and conjunctiva. The growth rate is very slow or even stationary.
          The novel use of AS-OCT intraoperatively in the excision of the limbal dermoid helps in complete excision of the mass while preventing excessive corneal thinning thereby reducing the risk of corneal perforation. In case of inadvertent corneal thinning intraoperatively tectonic support in the form of corneal patch grafting may be required.

Readwise:

1.     Pirouzian A. Management of pediatric corneal limbal dermoids. Clin Ophthalmol. 2013;7:607-614. doi:10.2147/OPTH.S38663.

2.     Zhong J, Deng Y, Zhang P, Li S, Huang H, Wang B, Zhang H, Peng L, Yang R, Xu J, Yuan J. New Grading System for Limbal Dermoid: A Retrospective Analysis of 261 Cases Over a 10-Year Period. Cornea. 2018 Jan;37(1):66-71. doi: 10.1097/ICO.0000000000001429.

3.     Cauduro RS, Ferraz CD, Morales MS, Garcia PN, Lopes YC, Souza PH, Allemann N. Application of anterior segment optical coherence tomography in pediatric ophthalmology. Journal of Ophthalmology. 2012 Aug 1;2012. https://doi.org/10.1155/2012/313120.

Correspondence
Dr. Prabhat Nangia
DNB, FICO, FMRF, FAICO
Consultant
Department of Cornea and Ocular surface
Suraj Eye Institute
Nagpur
Email – education@surajeye.org

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