The opacification of the normal transparent lens is called cataract. The Latin word ‘cataracta’ means ‘waterfall’. Imagine trying to peer through a sheet of falling water or through a frosted or fogged-up window. Development of Cataract varies from person to person but as a general rule, most cataracts develop slowly over a period of time. A cataract can take months or even years to reach a point where it adversely affects vision.
Causes of cataract
Age-related cataract
The cataract occurs as a result of the natural aging process of lens fibres which become opaque over a period of time.
Traumatic cataract
- Due to a direct penetrating injury.
- Concussion- Electric shock and lightning.
- Ionizing radiation done as treatment for ocular tumors.
- Surgical trauma
Metabolic cataract: Defect in body metabolism
- Diabetes
- Galactosaemia -inborn error of metabolism
- Calcium disorders
Steroid-induced cataract
This occurs as a result of excess intake of oral steroid or putting steroid drops in the eye.
Secondary cataract
Here, cataract develops as a result of some other primary ocular disease such as chronic eye inflammation or glaucoma.
History of Cataract treatment
The earliest surgery treatment was started in India, by Maharshi Sushruta. It was known as ‘couching’, where the cataractous lens was dislocated backward into the bottom of the eye and out of visual axis.
This procedure was performed for more than two thousand years until the mid-eighteenth century. Great progress in cataract surgery has been made in recent years with the introduction of micro-surgical instruments, microscope and modern surgical techniques like phacoemulsification, which has made couching obsolete.
In the early stages of cataract development, all that is needed to correct your vision with glasses is a change in prescription. As the cataract develops and begins to affect your lifestyle, it needs to be removed. Cataract surgery, the most commonly performed operation, is safe and effective in 95% patients with enhancement in vision.
Methods of evaluation of cataracts:
Visual acuity: Checking vision of both eyes unaided and aided with glasses and pin-hole vision to know the improvement as well as to get the general idea about the macular function of the eyes. This will help in prognostic evaluation of visual recovery after cataract surgery.
Intra ocular pressure: If intra-ocular pressure increases as a secondary to cataract surgery is needed to prevent further complications.
Slit-lamp examination: To know the type of cataract along with its opacity, morphology and etiology or any associated ocular pathology.
Direct and indirect ophthalmoscopy: for complete retinal evaluation. Dense cataract will prevent retinal evaluation and such cases need B-scan for retinal evaluation.
A-scan biometry: To calculate the AL and IOL power for implantation in cases of mature cataract the posterior segment of the eye is evaluated.
Optical biometry: this is an advanced non contact method to measure IOL power. It is patient friendly and highly precise
Treatment Options Available For Cataract
Extra Capsular Cataract Extraction (ECCE): is a conventional technique.
- ECCE requires an incision of 10-12mm
- The doctor removes the clouded lens in one piece.
- Multiple stitches are required.
- Doctor implants a non-foldable lens.
Phacoemulsification – A Micro Incision Cataract Surgery
Phacoemulsification is latest technology in Cataract surgery. It is a micro-incisional stitch less operation where cataract is emulsified by ultra sound energy, liquefied & sucked through the phacoemulsifier probe. A foldable intra- ocular lens is then implanted in the eye permanently.
Vision restoration is possible in a short period of time & is least traumatic with early rehabilitation & recuperation.
Advantages
- It is Stitchless. Hence healing is very fast.
- It is done under Topical anaesthesia (by putting drops.) So no need to patch the eye except in special circumstances
- Vision correction for far & near is possible
- Patient can get back to work in the shortest possible time
During cataract surgery, the natural lens of the eye that has turned opaque is removed, resulting in loss of focusing power of the eye. This situation would be parallel to clicking a photograph without a camera lens–the picture would be extremely blurred. When the natural lens of the eye is removed an artificial implant is placed in the eye.
Intraocular Lens
An intraocular lens (IOL) implant is a synthetic, artificial lens placed inside the eye that replaces the natural lens which is surgically removed usually as a part of cataract surgery.
Monofocal intraocular lens can be used to give clear point focus either at a distance or close up, but one can choose only one focal point.
Multifocal IOLs are popular as they allow correction of vision for both far & near distance.
Trifocal IOLs provides excellent vision not only for near and far, but also for intermediate distances, especially for people who have routine usage of computers.
Apodized Diffractive Multifocal IOL
Gradual diffractive steps on the IOL implant that create a smooth transition between focal points. The IOL bends incoming light to the multiple focal points to increase vision in differing light situations.
Accomodative IOL
Crystalens and Trulign Toric currently are the only US-FDA -approved intraocular lenses (IOLs) that use a method called accommodation, enabling sharper vision at multiple distances for people who have undergone cataract surgery.
An accommodating IOL shifts position with the action of eye muscles and movement to improve eyesight.
Toric IOL for astigmatism
This is a monofocal IOL with astigmatism correction built into the lens.
- Astigmatism: This eye condition distorts or blurs the ability to see both near and distant objects. With astigmatism the cornea (the clear front window of the eye) is not round and smooth (like a basketball), but instead is curved like a football. People with significant degrees of astigmatism are usually most satisfied with toric IOLs.
- People who want to reduce (or possibly eliminate) the need for eyeglasses may opt for an additional treatment called limbal relaxing incisions, which may be done at the same time as cataract surgery or separately. These small incisions allow the cornea’s shape to be rounder or more symmetrical.
Protective IOL filters
IOLs include filters to protect the eye’s retina from exposure to UV and other potentially damaging light radiation. The eye doctor selects the filters that will provide appropriate protection for the patient’s specific needs.
Other important cataract lens replacement considerations
- In some cases, after healing completely from the cataract lens surgery, some people may need further correction to achieve the best vision possible. Their ophthalmologist may recommend additional surgery to exchange an IOL for another type, implant an additional IOL, or make limbal relaxing incisions in the cornea. Other laser refractive surgery may be recommended in some cases.
- People who have had refractive surgery such as LASIK need to be carefully evaluated before getting IOLs because the ability to calculate the correct IOL prescription may be affected by the previous refractive surgery.
