Intra-ocular calcifications can occur due to a variety of reasons. In cataract, the lovely lens gets calcified and the bright beautiful world becomes dark and dreadful. Cataract comes in various forms like; congenital, traumatic and senile. Asteroid Hyalosis (AH) occurs because of the accumulation of calcium soaps in vitreous of the eyes. Although it is asymptomatic and unilateral, it is seen more often in diabetic patients. Tumours of eye like retinoblastoma and optic nerve meningioma too are known to show calcifications. This review has focussed on imaging appearances of intra-ocular calcifications, a small process in a small organ that nevertheless has a wide impact on the entire organs.
Introduction
We all can enjoy the beauties of the world so long as our eyes are away from dreaded calcifications – their processes and determinants. But once calcification sets in any part of the eye; it is bound to make its presence felt.
The three main ways in which the intra-ocular calcifications manifest in our eyes are: Cataract, AH and Calcifications in tumours related to eye.
Cataract
A cataract is defined as an abnormal opacity of any portion of the lens, regardless of visual acuity. In some advanced cases of cataracts in which good fundus visualisation is not possible, an ultrasound examination provides better assessment of the posterior segment of the globe.
On ultrasound; a cataractous lens appears swollen than normal and it becomes echogenic due to calcification. Common causes of cataract are Congenital eg. TORCHeS infections [Table/Fig-1], Senile or Degenerative or Age related changes [Table/Fig-2] or a Post traumatic sequel as a result of dislocation [Table/Fig-3].
B Scan showing Bilateral Congenital Cataract
B Scan showing Bilateral Senile Cataract
B Scan showing Post traumatic dislocated Cataractous Lens
It is the primary cause of reversible blindness all over the world [1–3]. A number of factors stand in the way of treatment for cataract; prominent among them being emotional factors [4]. Ultrasonographic evaluations are often used in cataract campaigns and it is particularly indicated in cases in which the posterior pole cannot be examined through normal optometric methods.
Ultrasound is a non-invasive, painless imaging method that can be done at a doctor’s clinic on adults as well as children [5]. Ultrasonic evaluation of the posterior segment in patients with opacities is vital, to determine the most suitable type of surgery [6, 7].
Ultrasound not only diagnoses cataract, but it also reveals in the eye, abnormalities that could compromise the function of the eye after surgery. The most common of these abnormalities are vitreous opacities (12.1%), followed by retinal detachment (9.3%). The patients with these anomalies should not be considered for cataract surgery and they should be guided to adequate treatment for the detected disease. Thus, preoperative ultrasonography has a definitive role of in patients with dense cataracts [8–10].
Asteroid Hyalosis
AH is the occurrence of calcium soaps suspended in the vitreous of one or both eyes. Although invisible to the naked unaided eye, non-invasive Ocular Ultrasound and Fundoscopy can demonstrate them beautifully.
High spikes are seen on the A scan vector. On B scan imaging [11–20], normal posterior segment of eye appears clean and echo free [Table/Fig-4]. In presence of AH, discrete mobile points like bright echoes without any posterior acoustic shadowing [Table/Fig-4] and which have considerable after movements [Table/Fig-5] are seen in the vitreous. The media appears hazy on fundoscopy and AH is seen as shiny highly refractive bodies in the vitreous. Although the exact aetiology is unknown, it has been reported in 30 -70% of diabetics [11, 20].
On B scan, normal vitreous is echo free as seen in left eye, whereas the Asteroid Hyalosis is seen as bright echoes in vitreous in right eye
B Scan showing after movements of Asteroid Hyalosis following eye movement
Although it usually causes no severe visual disturbances, its health impacts can be considerable when it exists in association with other local abnormalities like cataract or degenerative changes.
Calcifications in Ocular Tumours
Retinoblastoma is a small round-cell tumour of neuroepithelial cell origin, and the commonest childhood intraocular malignancy [21, 22]. Approximately 200 cases are diagnosed per year in the United States. The average age at diagnosis is 18 months, with 80% of cases occurring before age of 3-4 years [21]. Approximately 30% of cases are bilateral and they are typically diagnosed earlier than unilateral cases. Lesions may be synchronous, metachronous, unifocal, or multifocal. Most (90%) new cases of retinoblastoma are sporadic and only 10% are inherited. Inherited retinoblastoma has an autosomal dominant pattern of inheritance, with 80-100% penetrance. Sporadic lesions usually result from spontaneous mutations [21].
Diagnosis is typically made by doing an ophthalmologic examination, being prompted by leukocoria or “white reflex” [21,23], which is seen in 60% of patients [23]. Leukocoria is associated with large tumours or total retinal detachment [21]. Until recently, imaging techniques have lacked resolution capabilities that could approach an ophthalmologic examination.
On high resolution ultrasound [Table/Fig-6], the tumour appears as an echogenic soft-tissue mass with various degrees of calcification [22]. MR imaging [Table/Fig-6] or CT best delineates the resulting intracranial spread [21]. Colour Doppler imaging can identify and monitor tumour viability.
USG and MRI showing calcifications in Retinoblastoma
On CT [Table/Fig-7], retinoblastoma is characterised by enhancing intermediate-density soft-tissue mass or masses, with varying degrees of calcification. Retinoblastoma contracts, calcifies, and becomes hypo vascular in response to therapy [24]. Treatment includes enucleation for unilateral disease and radiation therapy with or without enucleation for bilateral disease.
Coronal CT scan image showing calcifications in Retinoblastoma
Other tumours of eye like optic nerve meningiomas are also demonstrated on USG [Table/Fig-8] as well as on CT scans [Table/Fig-8] due to their calcifications [25, 26].
USG and CT images showing calcifications in Optic Nerve Meningioma
Impact of Intra-Ocular Calcification on The Health of The Individual
Cataract affects the visual acuity and it can lead to progressive blindness in cases of Senile Cataracts and to developmental blindness in cases of Congenital Cataracts. Traumatic Cataracts can lead to instantaneous blindness. Hence, all types of cataracts are best treated to preserve optimum function of the eyes.
Although, AH does not impair vision; nevertheless, its association with diabetes must prompt one to keep an adequate follow up for earliest detection and timely management of dreaded diabetes. Calcifications seen in tumours need to be treated, not as separate entities, but as part of the tumour treatment only, depending on the tumour staging.
In conclusion, intraocular calcifications are quite distressing but they are diagnosable with the available array of imaging modalities. Though they can be detected by routine methods, one must also know about some newer methods of diagnosis, like Energy dispersive X-ray spectroscopy and optical coherence tomography (OCT), which can even diagnose the calcification of hydrogel Intra Ocular Lens as well [27, 28]. Moreover, it must also be remembered that advances in technology have made ultrasound and MRI as accurate as CT scan for detection of calcifications. In MRI, a high-resolution gradient-echo T2-weighted sequence showed promising results regarding detection of calcifications and it has been shown to be more effective than spin-echo techniques [29,30].
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