Any clouding in the normal eye Lens is called Cataract. Cataract is one of the common causes for blurry vision. The prevalence of cataract increases with age in a way that cataract surgery is one of the most common surgeries in the world. According to the world health organisation , cataract is the most common cause for reversible blindness in the world. The prevalence of cataract is higher in poor-nutrition, low-income , low social status and lower education societies. Cataract is bilateral in most cases but the intensity of cataract progression differs in eyes. In general cataract develops slowly and it's not like it destroys the vision abruptly.
What causes cataract?
Cataracts have a direct link with aging and are seen in older people. Some genetic factors are associated with cataracts as well. Other causes such as diabetes,long term use of corticosteroids medications and also previous eye surgeries have an effect on cataract development. Destruction and alteration in proteins and disruption in order and connection of the lens fibers and water absorption causes the lens to become opaque. The amount of proteins,vitamin C and potassium decreases and the amount of sodium and calcium increases in the lens. There is some evidence showing that Cataract is more prevalent in places where the sun stays longer and the UV radiation is more intense .the most important preventable risk factor is smoking.
What are the types of cataract?
It is classified based on the location of the lens opacity to three types of nuclear,cortical and posterior subcapsular or a combination of these three and other type of cataract which is present at birth is called congenital cataract .
- involvement of the central zone of the lens (nuclear) : this type of cataract first manifests itself with myopia and improved vision for reading but overtime the lens becomes cloudy and one's vision gets impaired .the lens gradually turns to yellow and brown and when this happens it becomes difficult for one to differentiate between colours .
- involvement of lens edges (cortical) : in this case white streaks opacities form on the outside edge of the lens.These opacities progress inward on the lens to the center and prevent light from passing through the retina and forming correct image.
- involvement of the backside of the lens ( posterior subcapsular area) : an opacity forms in the back of the lens and often to the right side of the light path .This type of cataract reduces the ability of reading and creates halo around the light source specially at nights. This type of cataract usually developes faster than other types of cataract.
- congenital cataract: it means that the baby is born with cataract disease or it develops very quickly in childhood. It might be genetic or caused by a variety of intraocular infections or trauma.
Cataract is not visible to normal people unless the cortical opacity of the lens is complete in which the eye pupil seems white. Usually the severity of cataract is proportional to vision impairment but in cases such as posterior subcapsular type the vision impairment is more severe than cataract.
What are the symptoms of cataract?
The most important and common complaint of a patient with cataracts is the gradual loss of vision. Light diffusion and scattering light vision , seeing halos around objects and diplopia in one eye might be another complaints of patients. Those suffering from cataract become sensitive to light and need more light to read and see in the environment. Most adults with cataracts complain of vision impairment when driving at night or vision loss. If cataract is nuclear type the optical power increases and eye becomes nearsighted. The feeling of a person with a cataract is like looking around over an opaque glass. Usually The vision decreases gradually, but in patients with one-eyed cataract , they may not notice their disease and whenever the eyes get examined alone, they will suddenly notice a decrease in vision. People with cataracts have repeatedly reported a history of eye lens and contact lens replacements.
What the causes of cataracts?
- trauma injury
- eye diseases
- general diseases
- using medications
The necessity of cataract surgery :
Do I need cataract surgery?
- Whenever the visual impairment caused by the opacity of the lens is such extent to effect one's daily life and activity ,one should have the surgery. The most important criterion for cataract surgery ia the amount of vision in which one requires.
- better visualisation of the eye and possibility of treating retinal lesions :
- In diabetic patients in which lens opacity prevents examinations and interventions to the posterior parts of the eye ,cataract surgery is necessary to remove the opacity of the visual pathway to maintain the treatment to the posterior side.
- formation of Glaucoma as a result of cataract
- intraocular inflammation
What's the procedure of cataract surgery?
Nowadays, due to the surgical microscope, threading of yarns, the suture needle and the scalpels, also the use of the phaco machine as well as the use of intraocular contact lenses a revoultion has been made in cataract surgery. All of these advanced facilities and methods of cataract surgery are now available in Iran. Depending on patient's physical and mental condition, cataract surgery can be performed with local or general anesthesia.
Intracapsular cataract extraction :
In this method, a large incision is made in the limbus and the lens is completely removed with the capsule. However, this procedure is less commonly performed due to the replacement of more efficient methods.
Extracapsular cataract extraction:
In this method, a smaller incision is made and only one part of the anterior portion of the capsule is removed in a round shape.Then the lens core and lens cortex is removed. In this method the posterior capsule and even a part of the anterior capsule will remain in the form of a sac and the artificial lens is inserted into the eye. This type of surgery is more suitable because of its lesser postoperative complications.
In this type of procedure the incision is also much smaller and is about millimeters, and the neclus in the capsular bag of the eye is emulsified and aspirated out of eye using phaco machine that vibrates ultrasonic frequency and by using a low power headpiece. The benefit of this procedure in comparison with the surgery is the very small incision in which does not even require stitches, and the eye after surgery is stable and requires much less recovery.
Postoperative care of cataract surgery
Recent progress in cataract surgery in Iran and worldwide have resulted in better surgery results and shorter postoperative recovery and most operations are performed on an outpatient basis. Attempts to prevent infection should begin before surgery and continue for some time after. Inflammation caused by cataract surgery is usually controlled by corticosteroid drops.
What are the complications of cataract surgery?
These complications include during operation and postoperative complications.
During operation complications
- Posterior capsule rupture and extrusion of the vitreous fluid and lens collapse into the vitreous space
- iris injury
- corneal edema due to the damage of corneal cells
- severe bleeding of choroid origin
Postoperative complications of cataract surgery
- Endophthalmitis: it's a serious complication of intraocular surgeries. The most common cause is infectious factors at the edge of the eyelids and conjunctiva. Endophthalmitis should be suspected in case of any pain, inflammation or vision loss and medication intervention or surgery should be performed to control it.
- retinal detachment which is rare in extracapsular and phaco procedures
- permanent corneal edema as a result of corneal cells damage during operation
- opacity of posterior capsule
Types of cataract surgical lenses
Depending on the condition ,these lenses are placed in the anterior or posterior chamber (more commonly). Posterior chamber lenses include a variety of hard and soft lenses.
Hard lens: made of polymethyl methacrylate
Soft lens: singel focus lens, multi focal lens,hydrophilic or hydrophobic lens , acrylic ,silicon or hydrogel lens