Inside the eyes, we have a natural lens of high positive power (about 18 diopters): the crystalline lens. This lens refracts light rays and focuses them on the retina and helps us to see. The crystalline lens must be transparent.
A cataract is a partial or total clouding of the lens. The opacity causes light to be scattered inside the eye and it does not reach the retina clearly or cannot be focused on the retina, creating blurred images.
There are many different types of cataracts. The most frequent are nuclear cataracts, where the opacity is in the center of the lens, it can also affect the cortex or only a part of it and there can be subcapsular cataracts (especially in patients treated with corticosteroids).
The degree of visual impairment depends on the degree of opacity of the crystalline lens and its location in relation to the visual axis (pupillary area), so that very small cataracts centered on the optical axis are very disabling and other larger but peripheral cataracts do not produce such a great loss of visual acuity.
Apart from the loss of visual acuity (less vision), cataracts can also cause problems in appreciating colors and changes in contrast perception. It is very common for a cataract patient to say that he or she sees colors much more “vividly”.
It is the leading cause of visual impairment in the world and in developed countries, it is the most operated pathology. Due to the increase in life expectancy and the aging of the population, its prevalence is on the rise.
What causes cataracts?
The causes that can lead to cataracts range from aging, a trauma that the patient may have suffered, ultraviolet radiation from the sun, genetic prevalence, skin diseases, the consumption of some drugs or some medications.
- Age: this is the most common cause. Lens proteins denature and degrade over time, this process is accelerated by diseases such as diabetes and hypertension. Environmental factors such as toxins, ultraviolet (UV) radiation have a cumulative effect over time.
- Trauma: Trauma can cause the lens tissues to become inflamed and whitish in color, and if the trauma is severe it can damage other structures of the eye such as the cornea, iris or retina.
- Radiation: UV radiation, specifically UV-B, has been shown to cause cataracts and the use of sunglasses from an early age slows the development of cataracts later in life.
Electric shocks can also cause cataracts. Infrared radiation associated with heat sources can cause cataracts, as can lasers. - Genetics: Genetics is an important factor in the development of cataracts. There are genetic diseases associated with cataracts such as: cat’s meow syndrome, Down syndrome, Turner syndrome, Edward syndrome, etc.
- Skin diseases: skin and lens have the same embryological origin and can be affected by the same diseases.
- Drug use: tobacco smoking has shown a two-fold increase in the development of some type of cataract. Alcohol does not appear to be implicated in cataract development.
- Medications: the clearest example is corticosteroids, which increase the probability of developing cataracts, specifically posterior subcapsular cataracts.
What treatments are available?
The only existing treatment for cataract is surgical, there is no medical treatment.
The surgery performed by specialists in Ophthalmology is most of the time ambulatory, that is to say, it does not require hospital admission. Anesthesia is usually topical, peribulbar anesthesia is rarely necessary and more rarely general anesthesia.
When cataract surgery is performed, a lens is implanted inside the eye to replace the refractive power of the opacified crystalline lens. There are many types of lenses, but they can be divided into two:
- The “normal” ones, which are used for distance vision and glasses are necessary for near vision.
- Progressive (multifocal, trifocal, bifocal…), which are used for “all distances”. It is very important to know that not all patients can be fitted with this type of lens.
When are cataracts operated?
Cataracts are operated when they produce a loss or disorder of vision that prevents the patient from leading a normal and usual life. Therefore, it depends on the visual needs of each individual.