This article is for informational purposes only and does not diagnose any conditions
Cataracts generally develop slowly, so symptoms are often gradual, and people may not notice or recognize vision changes until the lens has become quite cloudy and vision is moderately impaired. As cataracts continue to develop, symptoms such as blurry vision or difficulty with night vision can get progressively worse.
An estimated 24.4 million people over the age of 40 in the United States have a cataract in either eye and this number is estimated to rise to 30.1 million by 2020.  By the age of 75, approximately half of all Americans have cataracts.
The human lens is a structure in the eye that focuses light from the outside world onto the retina. Normally, the human lens is clear, allowing rays of light from the outside world to focus on the retina located at the back of the eye. The retina then converts this light to electrical energy that it sends through the optic nerve to the brain. If the lens becomes cloudy, the light from the outside world can get dispersed and the lens does not focus the light properly onto the retina, causing people to begin to notice problems with their vision. This clouding of the lens is known as a cataract.
A normal lens is composed generally of water and proteins. If changes to these proteins or lens fibers occur, a cataract can start to develop or ‘grow’. Often, cataract formation is described as an aggregation (clumping) of the proteins within the eye’s lens. The degree of vision loss depends on where in the lens the cloudiness is located and the size of the cloudy area.
Most people are familiar with cataracts in older people, but cataracts can also occur in infants and children. Cataracts can occur at any age if there is significant trauma to the eye, or if a person has medical conditions which predisposes them to cataracts (such as diabetes). Certain medications can also cause cataracts (such as steroids).
Cataracts can develop in one or both eyes. If they develop in both eyes, one eye can have a worse cataract than the fellow eye. They can also develop at different times.
Cataracts generally develop slowly, so symptoms are often gradual, and people may not notice or recognize vision changes until the lens has become quite cloudy and vision is moderately impaired. As the cataract becomes more developed, symptoms will get progressively worse.
What are the symptoms of a cataract?
Symptoms of a cataract may include:
Cloudy, blurry or hazy vision
Colors appear faded or reduced in intensity or less vibrant
Vision seems to have a yellow or brownish shade, or it becomes difficult to identify colors like blue and purple
Need for brighter light for reading and other activities
Increased sensitivity to glare from lights, lamps, or oncoming headlights when driving at night
Presence of halos around lights (e.g., halos from headlights from oncoming cars at night)
Increased difficulty seeing at night
Frequent changes in refractive error (changes to glasses or contact lens prescription)
Double vision in one eye (monocular diplopia)
In photograph pupil appears glowing or white, rather than normal ‘red-eye’ (children and infants)
Sometimes, individuals can develop “second sight.” Second sight is a phenomenon that occurs usually with less progressed cataracts where a person can actually see better, especially with near or up-close vision. Because of the way the early cataract changes its focus of light on the retina, an individual may actually experience a temporary improvement in their near vision.
The symptoms of cataracts may also be signs of other eye-related problems, so it is always important to be examined by an eye care professional.
Symptoms of Cataract May Depend on the Type and Location
The types of symptoms experienced and rate at which they occur may be dependent on the type of cataract and where it is located.
CATARACTS ARE NOT ALWAYS UNIFORM, AND THERE ARE MANY TYPES OF CATARACTS.
Nuclear cataract – clouding of the nucleus, located in the very center of the lens. People typically experience darkening of their vision or it is appearing yellow or brownish. Some people have reported a temporary improvement in their ability to see things at near (objects at two feet or less, or with activities such as reading or knitting) without reading glasses when nuclear cataracts first develop. As discussed above, this phenomenon is referred to as “second sight” and unfortunately, the improvement disappears as the cataract worsens and becomes more developed. If you notice an improvement in your ability to read or perform near activities without using reading glasses, you should consult your eye care professional. Often this improvement in near vision, is accompanied by a worsening of distance vision.
Cortical cataract – clouding of the layer of the lens that surrounds the nucleus. These types of cataracts have a wedge or a spoke-like appearance.
Posterior subcapsular cataract – clouding of the furthest back, outer layer of the lens (under the lens capsule). Posterior subcapsular cataracts usually develop more rapidly and tend to occur in younger people.
How do eye care professionals detect a cataract?
Ophthalmologists or optometrists will perform a comprehensive (thorough) examination of your eyes. For this examination, your eyes may be dilated, meaning that they will put eye drops in your eyes that will widen your pupils. Dilated pupils may make your eyes very sensitive to light and cause vision to be blurred for several hours afterward. It is often recommended to bring someone to drive you home after having your eyes dilated.
ASSESSMENTS MAY INCLUDE:
Visual acuity test. This eye chart test measures how well (clarity and sharpness) you see at various distances and what power of lens is required for you to see best (glasses or contact lens prescription). Each eye will be tested individually. You will be shown a series of letters of different sizes to determine the smallest letters you are able to see clearly.
Dilated Slit-lamp eye exam. Dilating drops are placed in the eyes to widen, or dilate, your pupils. The ophthalmologist will examine the structures of the eye, including the cornea (front surface of the eye), lens (clear center of the eye, in front of the pupil), the iris (colored part of the eye), and the retina (the back part of the eye). The slit-lamp is a special microscope that allows for very detailed and close-up views of the eye structures and makes it easier to detect any abnormalities.
Ophthalmoscope Retinal exam. When eyes are dilated, the pupils are opened wide, allowing for easier views to the inside and back of the eye. The ophthalmologist will use an ophthalmoscope or slit-lamp to inspect for signs of cataract, and also examine they eyes for any other eye conditions.
Tonometry. A measurement of the pressure inside the eye. Eye drops are put in the eyes to numb them and then the front of the eye is gently touched with a small device. During a tonometry test it is important to try to keep relaxed and breath normally because holding our breath may interfere with accurate results.
Other assessments to evaluate the overall health and structure of the eye
How does eye trauma cause a cataract?
Following a blunt or penetrating trauma to the eye can cause a traumatic cataract can occur. A cataract will form because the injury caused a disruption to the lens fibers in the eye. Cataracts are estimated to occur in up to 65% of eye trauma cases.  A traumatic cataract can develop immediately after an eye injury or even years after an injury.
Can you see a cataract in a photograph?
It is not uncommon for a cataract in a child or infant to be detected as an abnormality noticed in a photograph that has been taken of them. Sometimes, when a photo is taken and the person is looking directly at the camera, the flash will light up the healthy retina at the back of the eye causing their pupils to look red in the photo (red eye). This is called a “red reflex.” If the pupils of both eyes in the photo appear red it is a good indication that the lens of the eye is nice and clear because nothing is blocking the flash of light from reaching the retina.
If one eye has a normal red-reflex and the other appears white, yellow or black it can be considered to be an "abnormal red-reflex". This can be a concerning sign for the presence of an eye condition, which should be diagnosed by a pediatric ophthalmologist. If an abnormal red-reflex is noticed in a photograph, it is important to bring that photograph to your child’s pediatrician or appointment with the ophthalmologist.
It is important to keep in mind that most abnormal red-reflexes are caused by refractive error, meaning near or far sightedness, so the abnormal red reflex is usually due to the shape of the eye, not necessarily a cataract.
Assessing a red-reflex in an image may not always produce accurate information and the photograph should be assessed by an eye care professional. Factors that may influence the accuracy of red-reflex in a photograph include:
Whether the child is looking directly toward the camera lens
Whether the camera flash is on and the background is dimly lit
Whether the red-eye reduction function on the camera is turned off
Refractive error (near sightedness or far sightedness)
Do Cataracts affect Quality of life?
Cataracts are one of the main causes of decreased vision in older people and because of the increasing vision loss, a decrease in quality of life and increase in depressive symptoms has been observed. Specifically, people experience difficulties in performing daily activities, and loss of independence and self-esteem. Cataracts negatively affect a person’s independence by impairing their driving abilities and confidence.
Fortunately, these symptoms have been shown to markedly improve following cataract surgery. 
 Hall, T., McGwin, G., & Owsley,C. (2005). Effect of cataract surgery on cognitive function in older adults. Journal of the American Geriatrics Society, 53(12), 2140-2144. https://www.ncbi.nlm.nih.gov/pubmed/16398899
 Insler MS, Helm CJ (1989) Traumatic cataract management in penetrating ocular injury. CLAO J 15: 78-81. https://www.ncbi.nlm.nih.gov/pubmed/2917402
 The Eye Diseases Prevalence Research Group. (2004, April). Prevalence of cataract and pseudophakia/aphakia among adults in the united states [nei statistics and data]. https://www.ncbi.nlm.nih.gov/pubmed/15078665
 Wood, J. & Carberry, T. (2006). Bilateral cataract surgery and driving performance. British Journal of Ophthalmology, 90, 1277-1280. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1857457/