Dr. Bibhuti B. Kashyap, K16832, Dr. Shorya Vardhan Azad, Dr.
Vinod Kumar, Dr. Rohan Chawla
ABSTRACT
Purpose: To study the features of choroidal osteoma with or without neovascularisation with the help of swept source OCT and OCT angiography
Methods: This was a cross sectional observational study of 16 eyes of 11 patients with choroidal osteoma.Tumour characteristics and associated integrity of retinal layers, presence of subretinal fluid,focal choroidal excavations,tumordepth,deossification,choroidal vasculature status,choroidalneovascular membrane(CNVM) morphology and visibility of bony trabeculae were evaluated with the help of swept source OCT and OCT angiography.
Results:All eyes had a single lesion with 4 small (<3DD), 3 medium(>3DD – <5DD) and 9 large(>5DD). All small and medium lesions were at the macula or near the arcades. Larger lesions were all peripapillary.Areas of deossification were present in all medium and larger lesions.Most of the lesions had more than 50 % of its area deossified. On OCT, inner retinal integrity was maintained in 8 out of 16 cases. Outer retinal integrity was maintained in 3 out of 16 cases.Common alterations observed were presence of a lesion/tumor (16/16), increased signal transmission to choroid (11/16) and choroidal neovascular membrane (6/16).Tumor surface was either convex (5/16) or irregular (11/16). Internal tumor reflectivity pattern most commonly noted was lamellar pattern(13/16) and hypo reflective spaces with hyper reflective dots (spongy pattern) within the tumor (3/16).
Conclusions:With the help of SSOCT AND OCTA,in-depth morphological details of choroidal osteomas closer to histopathology can be easily obtained in vivo
Keywords: Choroidal osteoma,Swept source OCT, OCT angiography,Ossification,deossification,Choroidal neovascular membrane,Internal reflectivity
SWEPT SOURCE OCT AND OCT ANGIOGRAPHY FEATURES OF CHOROIDAL OSTEOMA WITH OR WITHOUT NEOVASCULARISATION.
Introduction
Choroidal osteoma(CO) is a benign ossifying tumor of the choroid.1It is mostly unilateral, affecting young females who may remain asymptomatic until development of a complication following tumor evolution.2 Classically fundus reveals an orange yellow, slightly elevated lesion, located near the disc or at macula.3 Although its diagnosis is purely clinical, tumor characteristics such as location, size, evolution and complications have been understood and described thus far by clinical examination and occasionally by histopathology.3,4Arrival of swept source OCT (SS-OCT) has helped us understand such choroidal conditions with subtle imaging clues at par with histological sections owing to its ultra high resolution images.7
Herein, we present a large case series of CO of various sizes, at different point in time of their natural history imaged on SS-OCT and describe their characteristics.
Methods
We reviewed recordsof all patients diagnosed as CO who were examined on SS-OCT at our tertiary eye care center in northern India. All patients underwent systemic and ophthalmic examination inclusive of visual acuity, intraocular pressure (IOP), slit lamp examination, fundus examination and ultrasound (US). All cases were examined with SS-OCT (DRI OCT-1; Topcon, Tokyo, Japan) which has a wavelength tunable laser centered at 1,050 nm and tissue imaging depth of 2.6 mm. SS-OCT images of all patients were analyzed for integrity of retinal and choroidal layersas well as tumor characteristics.
Results
A total of 11 patients with 16 eyes were analyzed. Seven of 11 patients were females, with 5having bilateral involvement. Mean age of presentation was approximately 26 years (16-40 years). All eyes had a single lesion with 4 small (<3DD), 3 medium(>3DD – <5DD) and 9 large(>5DD). All small and medium lesions were at the macula or near the arcades. Larger lesions were all peripapillary, extending around the disc with 5 present around the superior border, 1 at inferior and 3 uniformly all around it. Areas of deossification seen as yellowish whitish discoloration were present in all medium and larger lesions (12/12). These areas were present at the center of the lesion with ossified areas peripherally. Most of the lesions had more than 50 % of its area deossified(10/12). Bleed present at or near the fovea was noted in 3 cases.
On OCT, inner retinal integrity was maintained in 8 out of 16 cases. Outer retinal integrity was maintained in 3 out of 16 cases. Choroidal changes were present in all cases (16/16). Common alterations observed were presence of a lesion/tumor (16/16), increased signal transmission to choroid (11/16) and choroidal neovascular membrane (6/16). The tumor mostly did not span the whole depth of the choroid (13/16). Tumor surface was either convex (5/16) or irregular (11/16). Internal tumor reflectivity pattern most commonly noted was hyper reflective lines of granularity with interspersed hyporeflective lines (lamellar pattern) (13/16). Hypo reflective spaces with hype reflective dots (spongy pattern) within the tumor was seen in 3/16 cases. Hypo reflective spaces without hyper reflective dots (area of osteoclastic activity) was present in 12/16. Another peculiar finding was the presence of approximation of the RPE to the sclera with absence/thinning of choroid leading to ditch or trench formation (4/16).
According to lesion size, small lesions showed no area of deossification (4/4), had normal inner retinal layers (4/4), tumor surface was convex (4/4) and internal reflectivity was lamellar pattern (4/4). Medium lesions had deossified area covering more than 50% (3/3), inner retinal layers having cystic spaces (1/3) with intraretinal fluid (2/3), outer retinal layers showing loss of photoreceptors along with RPE (3/3), choroidal neovascular membrane (2/3), irregular tumor contour (3/3) andlamellar internal reflectivity (3/3). Larger lesions had deossified area greater than 50% in all but one (8/9), inner retinal layers having cystic spaces (5/8) with intraretinal fluid (3/8), outer retinal layers showing photoreceptor loss along with RPE atrophy (9/9), choroidal neovascular membrane (4/9), irregular tumor contour (9/9) and lamellar internal reflectivity (6/9).
Discussion
Although, benign, choroidal osteoma does undergo evolutionary changes during the course of its existence.5Recent study by shields et al, described OCT features of choroidal osteoma with help of EDI, giving us an insight into tumor morphology such as bonelamellae, cement lines, Haversian canals, Volkmanncanals, and trabeculae.6 In our study we divided lesions according to their size and presence of deossification, the two main clinical clues in practice till now signifying tumor age.8,9 Firstly, according to tumor size we found small lesions to be asymptomatic and were picked up incidentally. None of the patients showed any signs of deossification clinically. OnSS-OCT, these tumors did not occupy the entire choroid with sparing of the outer choroidal vessels and the overlying CC as described on histology in earlier studies.1 Tumor substance showed a tightly packed granular reflectivity with few horizontal hyper-reflective lamellae. Tumor surface was biconvex with no overlying retinal layer/RPE disruptions. As the tumor size increased to medium, deossification was seen in most cases. On SS-OCT, area of choroidal involvement increased with subsequent compression/atrophy of the CC. The outer choroidal vasculature was however preserved in most cases. Tumor substance showed similar reflectivity pattern as small lesions with addition of hyporeflective spaces (osteoclastic activity) present in the deossified area. Tumor surface was irregular in all cases with disruptions of the RPE/photoreceptors. Inner retinal changes were seen in cases with CNVM. In larger tumors, deossification was seen in all cases except one, covering most of the tumor area. SS-OCT revealed the tumor to be involving most of the choroid. Tumor substance showed similar reflectivity pattern as medium lesions with greater osteoclastic activity owing to greater area of deossification. Three cases showed hyporeflective areas with hypereflective dots, sign of spongy bone as described by previous studies.10However, granular hyperreflectivity with lamellae were more common than spongy pattern in our study, contrasting to what was observed in the aforementioned study.Tumor surface was irregular with total loss of retinal layers/RPE. Comparing these findings to the study by shields et al, we were unable to identify any vertical and horizontal channels found in the tumor, which they described as Haversian and Volkmann canals.7 However, our study did echo similar tumor reflectivity patterns, with lamellar pattern being more common than the spongy pattern
Choroidal neovascular membrane was absent in ossified tumors (0/4) and chances of its presence grew with greater deossification (6/12). Type 1 CNV was most commonly observed.Swept-source OCT angiography (SS-OCTA) additionally revealed a superficial lacy network of interconnected new vessels seen in the region of the CNVM, which were thick and dilated.Also, a deeper layer of thin vessels arranged in a “medusa head appearance” was seen in the region of the tumor.A connection between these group of vessels could also be deciphered at atleast 2 junctions.Multiple feeder vessels make such CNVMs poor candidates for the traditional laser therapy. Findings can be masked in FA due to mottled hyperfluoresence related to the choroidal osteoma. SS-OCTA is more informative, than standard SD-OCTA due to superior image quality. Fifty percent of these CNV’s presented as bleeds near the fovea.
To conclude, SS-OCT and SS-OCTA are helpful in assessing tumor attributes and predicting the different timelines in tumor evolution.
DISCLOSURES
Funding/support: This research did not receive any specific grant from funding agencies in the public, commercial, or not for project sectors.
Conflict of interest: None of the authors has conflict of interest with this submission.
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