13/12/2017
CATARACT
Cataract is the term used to describe a clouding of the lens of the eye.
The lens is a transparent oval shaped structure located near the front of the eye. Light, entering the eye through the cornea, passes through the lens and strikes the retina, and the optic nerve transmits this light signal to the brain. The lens is suspended from the ciliary body by a series of fibres, and is bathed in the fluid of the anterior chamber to the front, and the vitreous body to the rear.
The lens can be stretched by the muscles of the ciliary body and this alters the focal length and allows objects at different distances to be seen clearly.
The lens consists of three layers, an outer sac or envelope, a frontal epithelial layer and the body of the lens. All of these layers are made of transparent fluid filled cells.
The lens is normally a crystal clear structure allowing the uninterrupted passage of light.
Any damage to the cells of the lens caused by trauma, radiation, UV light, drugs or systemic diseases can result in a loss of transparency and impaired vision.
Cataracts are most often associated with ageing, and it is thought that this may be due to degeneration or loss of the frontal epithelial cells with consequent reduction in the generation of new fibre cells and the exchange of fluid and nutrients with the existing fibre cells. Fibre cells deprived of nutrients and fluid undergo degenerative changes, including the deposition of clumps of protein. These degenerative changes result in a gradual clouding of the lens which affects light transmission and interferes with vision.
Senile cataracts have been associated with a number of systemic conditions including hypertension, cardiovascular disease, diabetes, allergies and cholelithiasis.
SIGNS & SYMPTOMS
- Patients usually present with a gradual blurring of vision, fading or yellowing of colours and poor night vision. .
- They may also complain of glare from bright light, sunlight or headlights or see haloes surrounding light globes or street lights.
- In some cases patients with cataracts experience changes in the lens which alter the focus and this can temporarily improve short sight.
Conditions with Similar Symptoms
• Age related macular degeneration
•Retinal detachment
•Keratitis
•Uveitis
•Tumor
INVESTIGATIONS
Optometry to determine visual acuity, contrast sensitivity etc
Slit lamp examination for evidence of lens changes
CT or MRI scan if cataract not detected
TREATMENT.
Although a number of medications including aldose reductase inhibitors and sorbitol lowering agents are under investigation for the treatment of cataracts, none of these medications are of proven efficacy.
Current treatment consists of surgical removal of the defective lens and replacement with an artificial plastic lens. This is a relatively simple procedure which is done under local anaesthetic.
A small incision is made in the cornea and a probe is inserted through the incision into the defective lens. The probe uses ultrasonic waves to break up and emulsify the cells of the lens and this material is then sucked out through the probe. A replacement lens is then inserted through the incision in the cornea. The replacement lenses are made of soft pliable plastic and are folded so that they can fit through the small incision in the cornea. There are a number of different types of lens available which can correct a variety of vision problems, resulting in significantly improved vision for most cataract patients.
Patient Management
After surgery, patient should avoid heavy lifting or straining to prevent increased intraocular pressure.
Refer all Cients with Cataract to Eye Specialits.