Background and History of Cataract Surgery
Cataract is a pathological process that is characterized by the clouding of the lens in the eye which leads to a decreased vision. The word cataract comes from a Greek word that means waterfall. The surgery of this pathology has been developed through centuries. The use of diverse techniques in different cultures has been varying from “needling” used from 29 BC to the “couching” technique used until 1748 when the first cataract extraction was done.
Modern cataract surgery with implantation of a lens inside the eye was developed in the mid-20th century by Dr. Harold Ridley who used inner eye lenses of polymethyl methacrylate. The phacoemulsification, a method that uses ultrasonic vibrations to tear up a cataract into small particles was performed in 1967 by Charles Kelman. The first silicone implant was collocated inside the eye in 1978 by Kai-Yi Zhou. Patricia Bath in 1967 invented a revolutionary technology, the laserphaco. This procedure set a milestone for this type of surgery.
Globally, different researches have been shown that more than 50% of people over the age of 60 have developed cataracts.
The lens of the eye or crystalline is a special transparent structure located behind the iris. It is composed of 4 layers: capsule, subcapsular epithelium, cortex, and nucleus.
Cataracts are usually a result of the aging process produced by changes in the protein structures causing opacity in the natural lens of the eyes. Sometimes the diagnosis of congenital cataract can be done after birth. Other causes have been studied such as severe trauma, some types of eye surgery, or inflammation of the eye. Less frequent cataracts are secondary to an excessive ultraviolet light exposure, ionizing radiation exposure, diabetes mellitus, and toxics habits. Moreover, it has been demonstrated that certain medications such as statins and phenothiazines can produce opacity of the crystalline.
How is cataract diagnosed?
The diagnosis of cataracts is based on the clinical manifestations and the exhaustive physical examination performed by an ophthalmologist. Patients with cataract usually complain about some visual changes such as blurred vision, difficulty with glare, dull colour vision, increased short-sightedness, frequent changes in eyeglass prescription, and occasionally double vision (diplopia) affecting one eye only.
Indications of cataract surgery
The surgery will not be necessary until normal vision becomes impaired. Surgery is highly recommended for a patient with significant vision loss and symptoms. A prior refractive surgery is not considered as a contraindication for this surgery.
Contraindications of cataract surgery
There are absolute and relative contraindications for cataract surgery.
The absolute contraindications are:
- Ophthalmic herpes zoster.
- Dendritic ulcers.
- Diabetic retinopathy
- Retinal detachment.
- Severe glaucoma
- Gross nystagmus
The relative contraindications are
- Recurrent erosion syndrome
- Corneal scarring
- Peripheral retinal degeneration
- Severe blepharitis.
Details of the cataract surgery procedure and different available techniques
The pre-operative treatment with the use of topical medications produces better outcomes. Topical non-steroidal anti-inflammatory agents are needed with the aim to keep the eye dilated during the surgical procedure. The use of antibiotics before the operation prevent the development of infections during the post-operatory period. Fluoroquinolones are the election class of antibiotics for this procedure.
The standard cataract surgical procedure is performed in a hospital or in an outpatient surgery center. The surgery only takes a few minutes. The patient after the surgery is able to go home.
There are three basic techniques for cataract surgery:
- Phacoemulsification: It is the most performed cataract surgery. It can usually be completed in a short period of time with minimal sedation. Local anaesthesia is used. Usually, the stitches are not needed nor is an eye patch after surgery. It is not performed using a laser, but a femto-second laser sometimes is needed with the aim to open the anterior capsule.
- Extracapsular cataract surgery: It is the indicated surgical technique in patients with advanced cataracts or when the first technique is not possible to be performed. Usually, it includes a larger incision and requires sutures to close the larger wound. The visual recovery is slower. The application of an eye patch is common after surgery.
- Intracapsular cataract surgery: This technique is uncommon because it needs a large incision in the eye. The entire lens is removed by the specialist as well as the capsule. The intraocular lenses are placed in front of the iris in a different location.
After the surgery, the implantation of the artificial lens is needed to replace the natural lens. A variety of intraocular lens are available including:
- Monofocal lenses: these are the most commonly implanted lenses, with equal power in all regions. They can provide high-quality distance vision
- Toric lenses: Toric lenses have more power in one specific axis. Their main objective is to correct astigmatism.
- Multifocal lenses: Multifocal intraocular lenses are one of the latest advancements in lens technology. These lenses have regions with different power allowing patients to see well at all distances.
Possible complications and risks of cataract surgery
This type of surgery has a favourable outcome, but there is a risk to develop some complications such as endophthalmitis, inflammation, retinal detachment, glaucoma, haemorrhage, and failure to improve vision.
Endophthalmitis is considered a severe ocular infection. Different studies have been demonstrated that this infection is produced by Staphylococcus and Streptococcus. It usually develops during the first week after surgery. It is characterized by symptoms such as pain in the eye, redness, loss of vision, redness or swelling of other structures of the eye, and a yellow/green discharge.
The retinal detachment is another complication with high incidence. A hole is developed in the retina. After that, the retina separates from the normal tissue with a consequent permanent loss of vision.
Cataract surgery is an outpatient procedure. Following surgery, the patient needs to be assessed by the specialist within the first few days and after the first few weeks post-operation. During this period, the patient will have to use eye drops to prevent infection and reduce inflammation. The patient can return to work in a few days. Once the vision has stabilized, the ophthalmologist will indicate glasses if needed. The type of intraocular lens implanted will determine the type of glasses required for optimal vision.