Fig. 26.1
(a) Conjunctival nevus with cyst. (b) Anterior segment OCT presents thickening of the conjunctiva and intralesional cyst
Clinically, ocular surface squamous neoplasia (OSSN) presents as elevated, papillary, gelatinous, or leukoplakic lesions. Diagnosis of these lesions can sometimes be challenging, and the use of noninvasive methods such as anterior segment OCT and ultrasound biomicroscopy has proven very useful (Thomas et al. 2014). A small pilot study involving the uterine cervix demonstrated the ability of OCT to distinguish abnormal epithelium from normal epithelium in the examination of cervical tissue (Gallwas et al. 2011). Kieval et al. (2012) investigated the use of an ultrahigh-resolution OCT as an adjuvant diagnostic tool in distinguishing ocular surface squamous neoplasia and pterygia (Fig. 26.2) (Kieval et al. 2012). Preoperative ultrahigh-resolution OCT images demonstrated similarities to the histopathologic specimens. Thomas et al. utilizing ultrahigh-resolution OCT demonstrated that OSSN presents a thickened layer of the epithelium, often with an abrupt transition from normal to neoplastic tissue. Differences in the measured epithelial thickness on ultrahigh-resolution OCT between squamous cell carcinoma and pterygia were statistically significant. Shousha et al. evaluated pterygia and through ultrahigh-resolution OCT imaging observed normal-thickness epithelium and a highly hyperreflective layer between the epithelium and Bowman’s layer. Scleral lesions can be visualized partially by OCT (Shousha et al. 2013).
Fig. 26.2
(a) Ocular surface squamous neoplasia: clinical appearance. (b) Anterior segment OCT reveals thickened epithelium crossing the limbus from the conjunctiva to the cornea
26.3 Anterior Uveal Tumors
Imaging technologies for anterior segment tumor evaluation provide useful information with regard to tumor size, shape, internal features, and extension. Anterior segment OCT has proven to be an important tool for diagnosis and analysis (Fig 26.3). Ultrasound biomicroscopy (UBM) represents another well-established method of imaging (Hood et al. 2011). Few clinical studies compared the usefulness of OCT and UBM in the evaluation of ciliary body and iris tumors. Siahmed et al. observed that UBM provided a precise measurement and regular surveillance capabilities compared with OCT (Razzaq et al. 2011). Pavlin et al. published a series of patients with iris and ciliary body tumors that were evaluated with both UBM and OCT and described that UBM had a superior ability to penetrate larger, highly pigmented tumors and those located in the ciliary body (Pavlin et al. 2009). Bianciotto and coworkers also reported UBM as a superior method for imaging of anterior segment tumors, such as ciliary body and iris melanoma, since it enabled visualization of all tumor margins and fewer problems with posterior shadowing and presented better resolution (Bianciotto et al. 2011).
Fig. 26.3
(a) Pigmented iris melanocytoma. (b, c) Anterior segment OCT shows hyperreflectivity with shadowing and obscuration of the posterior margin
26.4 Intraocular Tumors
26.4.1 Retinal and Retinal Pigment Epithelial Tumors
26.4.1.1 Congenital Hypertrophy of the Retinal Pigment Epithelium
Congenital hypertrophy of the retinal pigment epithelium (CHRPE) presents as a pigmented lesion with benign behavior, rarely associated with visual symptoms. Usually it is unilateral but can occasionally be multifocal or grouped. Due to its peripheral location, OCT imaging is difficult but the typical appearance is of thickened RPE layer (Fig. 26.4). Shields and colleagues described overlying retinal thinning and photoreceptor loss in patients with CHRPE (Shields et al. 2006).
Fig. 26.4
(a) Fundus appearance of congenital hypertrophy of the retinal pigment epithelium (RPE). (b) OCT appearance of the thickened RPE layer
26.4.1.2 Combined Hamartoma of the Retina and Retinal Pigment Epithelium
Combined hamartoma of the retina and RPE presents as an elevated gray mass of the retina that blends with the surrounding retina and RPE without retinal detachment or vitreous inflammation. It is associated with preretinal fibrosis and traction on the adjacent retina. Spectral domain OCT reveals an elevated hyperreflective mass in the retina with mild attenuation of the retinal pigment epithelium and photoreceptor inner segment/outer segment junction and may be accompanied by a hyperreflective epiretinal membrane (Brue et al. 2013; Huot et al. 2009; Shields et al. 2005a). Schachat and associates from the Macula Society observed vascular tortuosity, vitreoretinal surface abnormalities, and pigmentation (Schachat et al. 1984).
26.4.1.3 Retinal Astrocytic Hamartoma
Retinal astrocytic hamartoma (astrocytoma) is a vascularized, benign, glial tumor of the retina that can be acquired or congenital. Acquired astrocytic hamartomas appear as yellow-white mass of the inner retina, lack calcification, and can be associated with macular edema, exudation, and retinal traction. Congenital astrocytic hamartomas acquire calcification and are associated with tuberous sclerosis. SD-OCT shows a thickened inner retina, some disorganization of the inner and outer retinal layers, and an intact RPE and choriocapillaris underlying the tumor (Fig. 26.5) (Kimoto et al. 2008). Calcified tumors have higher reflectivity.
Fig. 26.5
(a) Retinal astrocytic hamartoma. (b) Thickened inner retina with disorganization of the inner and outer retinal layers
26.4.1.4 Retinal Cavernous Hemangioma
Cavernous hemangioma is a benign retinal vascular tumor that presents as dark-red saccular aneurysms. It can be associated with vitreous hemorrhage, preretinal fibrosis, or vascular occlusion. OCT shows a lobulated inner retina with optically clear spaces representing the saccular aneurysms. The underlying RPE is intact and subretinal fluid is typically absent (Fig. 26.6) (Andrade et al. 2005; Shields et al. 2005c).
Fig 26.6
(a) Retina cavernous hemangioma. (b) Epiretinal membrane bridging over multiple cystic spaces within inner and outer retinal layers
26.4.1.5 Retinal Capillary Hemangioma
Retinal hemangioblastoma (capillary hemangioma) is an orange circumscribed vascular lesion with dilated feeding artery and draining vein that can affect any part of the ocular fundus. Small tumors appear as red dots or as retinal telangiectasia. They may occur sporadically or can be associated with Von Hippel-Lindau disease. The value of OCT evaluation of these lesions lies in identifying and monitoring retinal changes. OCT shows a hyperreflective lesion with little inner tumor detail, but is useful to detect associated macular edema, epiretinal membrane, and subretinal fluid (Shields et al. 2005c).
26.4.1.6 Retinal Vasoproliferative Tumor
Vasoproliferative tumors of the retina are usually unilateral, yellow-red colored, located in the inferotemporal periphery with minimally dilated or nondilated feeding artery and draining vein in contrast to hemangioblastoma. Associated changes are exudative retinal detachment, macular edema, retinal fibrosis, hyper- and hypopigmentation of the RPE, and cellular infiltrates in the vitreous. Due to its peripheral location, many vasoproliferative tumors cannot be imaged requiring advanced changes in the OCT scan length. Posterior lesions demonstrate retinal inner layer disorganization and posterior shadowing. Vision loss is usually due to epiretinal membrane or exudative macular detachment, and OCT is useful to identify these changes and follow up during treatment. Following successful ablation of the vasoproliferative tumor, regression of the associated retinal exudative changes occurs.
26.4.2 Optic Disk Melanocytoma
Optic disk melanocytoma (ODM) is a benign deeply pigmented lesion that usually occurs in the optic nerve head. Histological studies have shown malignant transformation into melanoma in 1–2 % of cases, which causes progressive growth and severe visual loss. ODM sometimes causes complications such as central retinal vascular obstruction. OCT images show an elevated dome-shaped mass with dense posterior shadowing and a gradual slope at the tumor margin. Shields et al. examined optic disk melanocytomas using time domain OCT and found typical features of a gradually sloped nodular elevation with a hyperreflective anterior surface and dense posterior shadowing portraying an optically empty mass (Fig. 26.7) (Saxena et al. 2010; Shields et al. 2008).
Fig. 26.7
(a) Optic disk melanocytoma. (b) The inner layers of the retina appear to be thickened with disorganization of outer layers. The RPE is intact with normal underlying choroid
26.4.3 Choroidal Tumors
26.4.3.1 Choroidal Nevus
Choroidal nevi are the most common intraocular tumors and usually do not cause visual symptoms. Nevi are pigmented round subretinal lesions, with smooth margins and frequently present with overlying drusen, measuring less than 5 mm in basal diameter and 1 mm in thickness. They are benign lesions but can undergo malignant transformation. Factors predictive of nevus transformation into melanoma are juxtapapillary location, orange pigment, thickness greater than 2 mm, the presence of subretinal fluid, and visual symptoms. OCT is able to detect retinal and anterior choroidal changes that include retinal thinning, retinal edema, subretinal fluid, RPE detachment, and drusen. The choroidal findings are limited to the anterior surface and include hyporeflectivity in most of the cases. OCT evaluation is more sensitive than clinical examination to detect retinal edema, subretinal fluid, retinal thinning, and RPE detachment. Also, it helps to determine the status of photoreceptor and to characterize retinal edema (cystoid versus non-cystoid). Drusen, which are clinically visible, are evidenced by OCT as small dome-shaped elevations at the level of Bruch’s membrane (Shields et al. 2005b).
26.4.3.2 Indeterminate Melanocytic Lesions
Indeterminate melanocytic lesions (IMLs) are pigmented choroidal lesions between 1 and 3 mm in thickness and present a diagnostic challenge. IML can correspond to a large nevus or a choroidal melanoma. OCT is able to detect some of the features predictive of growth such as thickness greater than 2 mm, presence of orange pigment and subretinal fluid, and absence of drusen. Singh and associates used spectral domain OCT to describe accumulation of subretinal deposits corresponding to orange pigment over a small IML that had not been observed with time domain OCT (Fig. 26.8) (Singh et al. 2010). Lesions less likely to grow present chronic retinal changes such as thinned retina with intraretinal cysts and RPE thickening. Hyperautofluorescence correlates to OCT findings of lipofuscin or subretinal fluid (Fig. 26.9) (Singh et al. 2010).
