Grandpa Norman had cataracts, Grandma Joan had cataracts, your mom is booked in for cataract surgery next week, and we all know about Uncle Chester who got struck by lightning and somehow survived but developed cataracts within the month. In all likelihood, you know at least one person who has cataracts, or who had cataracts, so cataracts must be a pretty common occurrence. But what causes them, exactly?
What is a Cataract?
Approximately 3.7 million cataract operations are performed each year in the United States, making cataract surgery the most common surgical procedure of them all. This is no surprise given that the main cause of a cataract (spoiler alert) is older age.
A cataract is a haziness or clouding of the lens inside the eye, also known as the crystalline lens. This opacification can present in various patterns and areas of the lens, ranging for bicycle spoke-like spears radiating from the edge of the lens, to a dense white dot on the surface, to a yellowish-brown haze in the lens’ center, to even blue sparkles dotted throughout the lens. In other words, anything in the crystalline lens that isn’t transparent is a cataract.
The symptoms of a cataract depend on the type, the location, how progressed it is, and even how attuned to your vision you are. The most commonly reported visual disturbances are blurry or cloudy vision, increased sensitivity to glare, decreased contrast sensitivity (being able to pick details against a background), frequent changes to your eyeglass or contact lens prescription, and for some, altered color vision. Cataracts tend to form in both eyes around the same time, though can develop at asymmetrical rates.
Causes of a Cataract
There are several possible underlying causes of a cataract. If you paid no heed to the earlier spoiler alert, you’d know that the most common one is age.
Age-related cataracts, also known flatteringly as senile cataracts, account for the majority of cataracts. In other words, if you live long enough, you can expect to develop some degree of cataract. (However, this doesn’t necessarily mean you will need surgery for it).
The theory behind an age-related cataract is the accumulation of oxidative stress over time. Radiation of ultraviolet wavelengths can disrupt DNA of the cells in the lens, as well as inducing the formation of what’s known as reactive oxygen species (ROS). These ROS contribute to cell damage and aging, causing the lens fibers to lose their transparency, and ultimately, results in opacification and an age-related cataract.
Traumatic cataracts are those that occur due to an eye injury, which may either be blunt or penetrating (pierces the eye). Examples of a blunt eye injury include being hit by a fist or ball, while a penetrating eye injury can be from a shard of glass or a sharp stick. Other sources of injury to the eye can include electric shocks, infrared radiation, and chemical injury.
If you’ve suffered an eye injury, you probably have other symptoms to deal with more immediately, such as bleeding, pain, or a facial fracture. There are also other parts of the eye that can be damaged from trauma that may need more urgent attention, such as a retinal detachment. A cataract caused by trauma can grow within weeks of the injury while others are not apparent until months or years later.
Other medical conditions
The list of other diseases associated with cataracts is extensive. They include hereditary disorders including retinitis pigmentosa, Leber’s congenital amaurosis, gyrate atrophy, and Stickler syndrome. Cataracts can also be associated with systemic diseases such as diabetes, myotonic dystrophy, atopic dermatitis, neurofibromatosis type 2, hypocalcemia, and kidney impairment.
If your eyes glazed over reading the above paragraph until you came across «diabetes», and then glazed over again as you read through the rest of the medical jargon, you’re probably not the only one. Fortunately, given that over 37 million US residents are estimated to have diabetes, it makes sense to focus on diabetic cataracts.
Amongst other diabetes-related eye conditions, having diabetes is associated with the formation of what’s sometimes called a sugar cataract. Cataract is five times more likely in an individual with diabetes, and is also more likely to develop at a younger age. There are a few different theories for how diabetes causes cataract. One is that metabolism of excess glucose in the body causes the crystalline lens to draw in water, disrupting and damaging its cells. Another theory is increased oxidative stress from elevated glucose levels in the fluids of the eye, while a third theory is a possible autoimmune response from the body that induces the cataract, particularly in type 1 diabetes.
It is possible for babies to be born with cataracts, either in one or both eyes, or to develop one within the first year of life. These are called congenital cataracts. Congenital cataracts may be linked to an infection of the mother during pregnancy, a family history of congenital cataracts, and can also be more likely in premature babies. Infections that can cause congenital cataracts include chickenpox, cytomegalovirus, herpes, rubella, and toxoplasmosis.
Any white glint or reflection in the pupil of a child’s eye (the opening in the middle of the colored iris) should be assessed promptly as this is often the first tell-tale sign of a cataract. If there is a significant cataract found that is impacting vision, surgery is usually performed relatively soon to give the best chances of that eye developing normal connections with the visual areas of the brain.
An iatrogenic cataract is one that is induced by another medical procedure or treatment. Unfortunately, cataracts can be a side effect of several other medically-necessary procedures. Fortunately, typically all that’s needed to sort that out is a quick cataract operation later.
Common procedures and treatments associated with the later formation of a cataract include:
- Surgery to repair a retinal detachment
- Steroid medications, including eyedrops, inhalers, and tablets
- Radiation therapy for cancer
The exact underlying mechanisms may vary, but in essence, the cataracts develop after these treatments or procedures because of disruption or damage to the fibers in the crystalline lens, causing them to lose their transparency.
Other Risk Factors for Cataracts
You can’t do too much about getting older, but you can take steps to avoid eye injuries or keep your diabetes under tight control, in order to prolong your cataract-free sight.
In addition to those cataract causes, researchers have found other factors that can increase your risk of early cataract development. These include:
- Excessive alcohol intake
- Too much fun in the sun (without sunglasses)
- High blood pressure (hypertension)
- Nearsightedness (myopia)
Fortunately, though a prevalent condition, cataracts are more or less benign and present no threat of permanent blindness. Management of cataracts is fairly straightforward with a surgical procedure that often takes no more than 20 to 30 minutes per eye. If you do end up developing significant cataracts into older age, take it as a blessing – you’ve lived long enough to have them!
← Back to Investigación y Publicaciones