By Pratiksha Baliga
Published 7:18 PM EST, Wed April 7, 2021
The vitreous humour is a highly hydrated gel-like substance that provides structural support to the eyeball while providing a clear unobstructed path for light to reach the retina. It comes with hindrance to the forward oxygen diffusion from the retinal blood supply to the anterior segment of the eye where it can cause oxidative damage to the lens. It is an extracellular matrix composed of collagen fibrils with the carbohydrate polymer hyaluronan also called hyaluronic acid, serving as the major component between the fibrils. With age, it may partially liquefy as a result of hyaluronan breakdown associated with oxidative stress. Once liquefied the vitreous does not reform significantly. Opacities may form in the clear vitreous as a result of developmental abnormalities, injury, or diseases. Developmental opacities are present from birth and are remnants of the hyaloid system located in Cloquet’s canal.
Degenerative opacities are associated with inflammatory debris, often appear after ocular inflammation, ocular hemorrhage, posterior vitreous detachment, or vitreous hemorrhage.
One of such commonly observed degenerative opacities is Asteroid Hyalosis, a condition of the eye involving small white opacities of asteroid bodies or calcium fat globules in the vitreous humour. The asteroid bodies are chemically made up of calcium-pyrophosphates and phospholipids. These bodies remain attached to the collagen fibrils of the eye and move only with the movement of the collagen framework. The condition is considered to be degenerative as it is associated with increasing age usually 55 years and more commonly in males than females.
It occurs in only up to 0.2% of people under 55 years of age, while the prevalence in those 75 years or older is 2%-3%.
Fig: Asteroid Hyalosis
Fig: The yellow particles of Asteroid Hyalosis are seen over the optic nerve, which obscures the retina but vision is unaffected
Symptoms, Diagnosis, and Causes
It’s mostly asymptomatic and it does not affect the patients’ vision. It starts with the appearance of small yellow-white spots in the visual field of the patient, usually noticed during an eye examination by a specialist. The spots are very tiny and often hard to see unless observed closely under proper lightning. The white particles are composed of calcium hence to ease the eye examination the patient’s pupils are dilated using an instrument called a slit lamp. A special dye called fluorescein is applied with the administration of eye drops to dilate pupils to see the eye structures. In Asteroid Hyalosis asteroid particles would be visible through the slit beam.
Fig: Asteroid Particles in the vitreous cavity using Slit beam
Method of eye scanning can also be used called optical coherence tomography which will allow the eye specialist to visualize the retina layers in the back of the eye to create a cross-sectional retinal image. It can help provide an accurate anatomic diagnosis.
Fig: Optical coherence tomography appearance of Asteroid Hyalosis
Another method is Fluorescein Angiography which makes use of filters to reduce interference from the calcium bodies and makes diagnosis easier. However, this technique has limited ability to diagnose subtle abnormalities and often produces poor quality images. The requirement of high technical skill for handling the instrument is another challenge.
Fig: Fluorescein Angiography in Asteroid Hyalosis
Research believes that Asteroid Hyalosis is not associated with any particular eye disease but probably can be considered a side effect of certain eye procedures. The exact cause is unknown but it is believed that its association is with health conditions majorly diabetes mellitus. Patients with diabetes mellitus experience vitreous degeneration characterized by precocious liquefaction and posterior vitreous detachment. Biochemical studies have detected that hyperglycemia alters vitreous collagen, changes that might be responsible for the observed vitreous degeneration might cause asteroid hyalosis. It is considered to be unilateral but if it persists with health conditions like diabetes mellitus it should be bilateral because each eye is equally exposed to hyperglycemia.
The overall relationship between diabetes mellitus and asteroid hyalosis is further complicated by suggesting that asteroid hyalosis may arrest the process of vitreous collapse or eye contraction with proliferative diabetic retinopathy.
Asteroid Hyalosis doesn’t require any treatment unless it starts affecting a patient’s eye vision with being blurry/floaters or one has underlying conditions making your eye more vulnerable to damage such as diabetic retinopathy the vitreous humour can be surgically removed and replaced, a procedure of vitrectomy can be performed.
Fig: Procedure of Vitrectomy
The diagnosis and management of Asteroid Hyalosis are essential and should be done with utmost care. The associated health conditions, with the most common ones being diabetes mellitus, hypertension, and hyperlipidemia should be managed by interprofessional team communication with endocrinologists and general physicians along with optometrists, ophthalmologists, ophthalmology nurses, and operating room nurses. The nurses should be involved in the patient’s education and their follow-up, informing the ophthalmologist in case of any issue.
Pratiksha Baliga, Youth Medical Journal 2021
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