Journal of Cytology
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SYMPOSIUM ON OPHTHALMIC CYTOLOGY Table of Contents   
Year : 2007  |  Volume : 24  |  Issue : 1  |  Page : 19-21
Imaging in ophthalmic lesions


Department of CT, EKO X-Ray and Imaging Institute, Kolkata, West Bengal, India

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Keywords: Imaging, eye

How to cite this article:
Kundu B. Imaging in ophthalmic lesions. J Cytol 2007;24:19-21

How to cite this URL:
Kundu B. Imaging in ophthalmic lesions. J Cytol [serial online] 2007 [cited 2020 Sep 18];24:19-21. Available from: http://www.jcytol.org/text.asp?2007/24/1/19/42085



   Imaging in Ophthalmic Lesions Top


Orbital imaging has been through many transitions in the past several years, though magnetic resonance imaging (MRI) studies have improved soft tissue contrast, complementary studies including computed tomography (CT) scans, plain films, conventional angiography and ultrasonography all have their place in diagnosis of orbital pathology.

The orbit is one of the areas of the body where MRI has not supplanted CT as the clear choice for diagnostic imaging evaluation. [1] Firstly, because of the presence of superb natural contrast provided by retrobulbar fat, bony orbit and sinus air and any lesion that may be present can be seen on CT. Secondly, the inherent sensitivity of MRI to globe and eyelid motion. Since, the advent of MDCT (multi-detector CT) particularly with 16 and 64 slice CT scanners, CT has become isotopic imaging, that means multi-axial imaging is now possible like MRI without changing the patient's position. Use of surface coil MR imaging provide better contrast between orbital lesions and the adjacent normal structures, as compared with high resolution CT. [2] CT guided fine needle aspiration cytology (FNAC) is perhaps, one of the greatest boons in establishing a proper and accurate diagnosis.

The orbit can be divided into four distinct anatomic areas for the purposes of creating limited differential diagnosis by anatomic region: [1],[3] 1) Globe. 2) Optic nerve and sheath, 3) Conal-intraconal space and 4) Extraconal space


   Lesions of the Globe Top


Microphthalmia: A congenital underdevelopment of acquired diminution of the globe. Congenital microphthalmus is seen on CT as a small globe associated with small poorly developed orbit. In developmental microphthalmia CT shows a shrunken and calcified globe. [4]

Macrophthalmia: Enlargement of the globe - commonly due to a result of juvenile glaucoma or myopia.

Coloboma: Congenital defect in the globe, usually at the point of insertion of the optic nerve. CT or MRI usually shows a small globe with a cystic out-pouching of the vitreous at the site of attachment of the optic nerve to the globe.

Coat's Disease: Leukoria unilaterally in a 6 to 8 years old boy. The symptoms develop when the retina detaches with loss of central vision. Pathologically, it is a congenital vascular malformation of the retina characterized by multiple telangiectatic vessels. CT shows increased density in part or all of the vitreous of the globe, normal globe size and lack of calcification.

Sclerosing Endophthalmitis or Larval Granulomatosis: 2 to 8-year-old child, infected by playing in soil contaminated by dog excrement. Pathologically - ingestion of the ova of Toxocara canis results in uveitis or more generalized endophthalmitis. CT or MRI demonstrates dense vitreous without a discrete mass - calcification is not present.

Retinoblastoma: Most common tumour of the globe in childhood, usually younger than 3 years. 60% are unilateral and 40% bilateral. CT is preferred because of its sensitivity to calcification. Calcification may be clumped or punctate. MRI helps to delineate the extra-ocular extent of tumour. Tumour may spread along the optic nerve to the orbital apex and intracranial space.

Uveal Melanoma: Occurs in adults (50-70 years of age) - unilateral. 85% arise from the choroid, 9% from the ciliary body and 6% from the iris. Ultrasound diagnosis is so confidently made; CT or MRI is not routinely used in the work up of this tumour. CT shows a characteristic "mushroom cloud" appearance of the soft tissue mass. MRI shows a bright or high signal in T1 images. [5]

Ocular Metastasis: Only 50% of patients have a known primary tumour.

Ocular Degenerative Changes: Cataract, retinal detachment and disc drusen. Retinal detachment is well demonstrated by ultrasound and MRI as well as sometimes by CT as a 'V' or a 'sunset sign'.


   Lesions of the Optic Nerve-Sheath Top
[6]

Hypoplasia of the Optic Nerve: Septo-optic dysplasia is demonstrated excellently by MRI. The syndrome consists of bilateral or unilateral optic nerve hypoplasia with absence of the septum pellucidum, dysplasia of the third ventricle, hypothalamic hypopituitarism and growth hormone deficiency.

Lesions of optic chiasm and optic pathway: The resolution of MR scans is similar or superior to CT, and sagittal views are most useful in evaluating lesions in this location. [7]

Optic Neuritis: In adults is usually a harbinger of multiple sclerosis. CT is not so sensitive - occasionally shows thickening of the optic nerve. MRI is the modality of choice, specially T2 images and fat suppressed gadolinium contrast enhanced studies. [8]

Optic Nerve Gliomas: It is a childhood disease presenting within the first 10 years of life in 75% of cases. Histologically it is most commonly pilocytic astrocytoma.

Optic Nerve Sheath Meningioma: Tumour of middle aged women. Tumour arises from meningo­endothelial cells of the arachnoid layer. Because the optic nerve carries all three leptomeningeal layers with it to the globe, it can occur anywhere along this tract.


   Lesions in the Conal and Intraconal Space Top
[3]

Inflammatory Pseudotumour: It is the most common cause of an intra-orbital mass lesion in an adult. Radiologically, involves retrobulbar fat (76%), extra-ocular muscles (57%), optic nerve (38%), uveal­scleral area (33%) and lacrimal gland (5%). The two principal types are tumifactive (diffuse involvement of conal and intraconal structures) and myositic (involving the extra-ocular muscles). CT demonstrates unilateral enhancing mass involving single extra-ocular muscle including tendinous insertions (myositic type) associated with or without proptosis. [11] MRI features are the same.

Thyroid Ophthalmopathy: It is the most common cause of unilateral or bilateral proptosis in the adults. Bilateral involvement is seen in 80% cases. The characteristic findings on CT or MRI are enlargement of extra-ocular muscles with sparing of the tendinous attachments to the globe. The inferior, medial, lateral and superior rectus muscles are involved in descending order of frequency. [12]

Carotid-Cavernous Fistula: CT or MRI reveals enlargement of the superior ophthalmic vein and extra­ocular muscles. MRI shows signal void in the ipsilateral cavernous sinus.

Venous Varix: Contrast enhanced CT shows the varix as a lobulated, densely enhancing intraconal structure that enlarges with Valsalva maneuver. MRI shows the same except that documentation of the flow characteristics of blood within the lesion is better.

Superior Ophthalmic Vein Thrombosis: CT shows an enlarged superior ophthalmic vein with an enhancing rim and hypodense central clot. The ipsilateral cavernous sinus is usually also enlarged. MRI shows this much better.

Cavernous Haemangioma: Usually affects adults (20-40 years of age). CT shows a sharply defined intraconal soft tissue density mass that often spares the orbital apex. Uniform homogenous contrast enhancement is seen. Deformity of bony orbit due to erosion may be noted but bone destruction never occurs. MRI better delineates the relationship of the lesion to the optic nerve and the extra-ocular muscles.

Capillary Haemangioma: Seen in children of age less than one year. CT shows an enhancing mass spanning the conal-intraconal space and the extraconal space. The mass is usually not well outlined, and may have irregular margins, suggesting a malignant cause.

Lymphangioma: Infant or young child with proptosis. Contrast enhanced CT reveals a multiloculated, lobular, rim enhancing mass, which may be intraconal, conal or extraconal. MRI may reveal haematoma of different duration within the lesion.

Lymphoma: Seen in middle-aged patients (average age 50 years). It is the third most common cause of proptosis after orbital pseudotumour and cavernous haemangioma. CT /MRI show a spectrum of findings ranging from well defined to diffuse infiltration of the intraconal space. They can be bilateral.


   Lesions of the Extraconal Space Top


Pseudotumour of the Lacrimal Gland: Could be unilateral or even bilateral - swelling of the lacrimal glands. CT/MRI show enlarged lacrimal glands, which respond greatly to steroids. [13]

Epidermoid or Dermoid Tumours: CT/MRI demonstrates well-defined cystic masses, sometimes containing fluid density / intensity, fat and / or solid tissue as well as sometimes calcification is seen on CT.

Bony Lesions Like Fibrous Dysplasia / Paget's Disease: Better demonstrated and diagnosed by CT scan.[Table 1]

 
   References Top

1.Harnsberger HR. State of the art orbital imaging. Semin Ultrasound CT MR 1988; 9: 379 - 483.  Back to cited text no. 1  [PUBMED]  
2.Bilaniuk LT, Schenck HF, Zimmerman RA, et al. Ocular and orbital lesions-surface coil MR Imaging. Radiology 1985; 156:669-74.  Back to cited text no. 2    
3.Armington WG, Bilaniuk LT. The radiologic evaluation of the orbit-conal and intraconal lesions. Semin Ultrasound CT MR 1988; 9:455-73.  Back to cited text no. 3  [PUBMED]  
4.Char DH, Unsold R, Sobel DF, et al. Ocular and orbital pathology. In: Newtown TH, Hasso AN, Dillon WP, editors. Computed tomography of the head and neck, 1st ed. New York: Raven Press; 1988. p. 9.1-9.64.  Back to cited text no. 4    
5.Mafee MF, Peyman GA, Grisolano JE, et al. Malignant uveal melanomas and simulating lesions-MR imaging evaluation. Radiology 1986; 160: 773-80.  Back to cited text no. 5  [PUBMED]  [FULLTEXT]
6.Peyster RG, Hoover ED, Hershey BL, et al. High resolution CT of lesions of the optic nerve. AJR 1983; 140:869- 74.  Back to cited text no. 6  [PUBMED]  [FULLTEXT]
7.Albert A, Lee BC, Saint- Louis, et al. MRI of the optic chiasm and the optic pathways, AJNR 1986; 7:255- 8.  Back to cited text no. 7    
8.Levine HL, Ferris EJ. The neuroradiologic evaluation of "opitc neuritis." AJR 1975; 125: 702-16.  Back to cited text no. 8    
9.Cohn EM. Optic nerve sheath meningioma-neuroradioligic findings. J Clin Neuro Opthalmol 1983; 3:85-9.  Back to cited text no. 9    
10.Swenson SA, Forbes GS. Radiologic evaluation of tumours of the optic nerve . AJNR 1982; 3:319 -26.  Back to cited text no. 10    
11.Flanders AE, Mafee MF, Rao VM, et al. CT characteristics of orbital psedotumours and other inflammatory processes. J Comput Assit Tomogr 1989; 13:40-7.  Back to cited text no. 11    
12.Hoston N, Sander B, Cordes M, et al. Grave's ophthalmopathy: MR imaging of the orbits. Radiology 1989;172:759 - 62.  Back to cited text no. 12    
13.Lloyd GA. Lacrimal gland tumours-the role of CT and conventional radiology. Br J Radiol 1981; 54:1034-8.  Back to cited text no. 13  [PUBMED]  

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Correspondence Address:
B Kundu
Department of CT, EKO X-Ray and Imaging Institute, 54, J.L. Nehru Road, Kolkata, West Bengal - 700071
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0970-9371.42085

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