Grading or Classification for Cataracts

“Doc, how bad are my cataracts?” “How fast are my cataracts growing?” These are two questions I get asked by my patients daily. The majority of people believe that cataracts are a film that is growing over their eyes. This film needs to be removed to improve their vision.

What is a cataract? A cataract occurs when the lens behind the pupil, which focuses the light onto the retina, becomes cloudy or hazy. It is not a film growing over the eye. The term cataracts came from the term used for rapids in a river. When the water in a river starts to flow rapidly downstream, the water changes from clear to white. Before surgery was available to remove a cataract, the pupil would turn white as the cataract became severely advanced, or the term ripe was used. In the modern world, very few people let their cataracts advance to that level.

A cataract, in most cases, is an aging change that occurs in the lens over time. Epidemiological studies show that there are differences in the rates of cataract formation in different races. There is a genetic component in developing a cataract. Rarely is a child born with cataracts. In a previous study, it was found that there is a strong correlation between cataract formation and sun exposure or UV light. You can find numerous studies on cataracts at the National Eye Institute or other websites.

In a clinical setting, patients are not as interested in cataract grading. The grading of cataracts is necessary to document the cataract severity in the patient’s chart and for documentation in clinical studies. The grading system makes the results of the studies valid. There are several grading systems available in the United States, including the Lens Opacity Classification System (LOCS) or locs grade, locs i, locs ii, and locs iii; the Oxford Clinical Cataract Classification and Grading System; and the John Hopkins System.

classification of nuclear cataracts

Image source: Gao, X., Lin, S., & Wong, T. Y. (2015). Automatic feature learning to grade nuclear cataracts based on deep learning. p. 2

There are three common types of cataracts: nuclear cataracts, cortical cataracts, and posterior subcapsular cataracts. Each type of cataract can affect visual acuity in different ways and differ in the rate of progression. There are two major distinctions in cataract grading, which are immature cataracts and mature cataracts. As discussed earlier, a mature cataract, ripe cataract, or hypermature cataract is uncommon in the United States but may be very common in third-world countries where access to health care is limited. All nonwhite cataracts are immature cataracts. Less common types of cataracts are traumatic cataracts and congenital cataracts.

In clinical practice, the eye is examined with a slit lamp. A slit lamp evaluation is performed with a microscope. The human lens has three basic areas: the central nucleus and the outer cortex which are surrounded by a thin, clear capsule. Some people may have pure nuclear cataracts, cortical cataracts, or posterior subcapsular cataracts. If you are under age 55 and develop a cataract, there is a good chance you have a posterior subcapsular cataract. Posterior subcapsular cataracts are more common in younger people.

The grading scale of a nuclear cataract is based on nuclear color, nuclear opacity, or nuclear opalescence. The density of the cataract or lens hardness is graded as well. Slit examination of a nuclear sclerotic cataract (NS) has one to four levels.

A nuclear cataract is classically considered the aging type of cataract. It may take many years for this type of cataract to affect your vision. In many cases, it will make your eye more nearsighted. Nuclear cataracts cause increased lens density, which makes the eyes more nearsighted. You need to change your glass prescription and may not need surgery for many years.

The cortex of the lens is evaluated with the slit beam of the microscope and with retroillumination.

A cortical cataract is graded by the number of clock hours of cortical opacities or clouding of the cortex.

A cortical cataract may remain in the peripheral portion of the lens and not affect the vision for a long time.

A posterior cataract is located just underneath the posterior capsule. The severity of a posterior subcapsular cataract is graded by the percentage of the posterior capsule or lens that is covered by the opacity.

Posterior subcapsular cataracts usually affect your reading first and make your vision worse in bright lights or when car lights are shining into your eyes. The opacity may be located right in the center of your pupil, and when your pupil becomes smaller, the opacity blocks your vision. This type of cataract may affect your vision sooner.

You may have pure nuclear cataracts. You may have one type of cataract, two types of cataracts, or all three types of cataracts. Each type of cataract could be a different level of severity.

There is a newer type of abnormality found in the human lens today. This is called dysfunctional lens syndrome. There may be little visible cataract formation in the lens, but the patient is complaining of blurred vision as if they have a cataract. With new technology such as the iTrace instrument, any aberrations in the vision system can be detected. The iTrace instrument can show numerous aberrations in the lens that are causing the person’s visual symptoms. The dysfunctional lens is not focusing light onto the retina in the proper manner. Removing the dysfunctional lens will improve the vision, just like having a cataract removed.

Generally, a cataract progresses slowly over time. It may take early cataracts many years to progress to the point that they blur the vision. This is especially true for nuclear sclerotic cataracts. Posterior subcapsular cataracts may progress rapidly over a few months.

Patient having a Eye Laser Surgery
Image by Paul Diaconu from Pixabay

When should surgical intervention be considered? I get asked many times about when cataract surgery should be performed. Medicare has guidelines that most insurance companies follow as well. Generally, visual acuity is used as a guideline and you need to have worse than 20/40 vision. Other reasons for cataract surgery are limitations of lifestyle or quality-of-life issues, such as problems driving a car, especially at night; being unable to watch TV, read books, or work; or other limitations of lifestyle.

There is almost never a medical reason to have cataract surgery. If a doctor tells you you need cataract surgery, ask them why. Cataract surgery is nearly always an elective operation you are choosing to do because you are unhappy with the quality of your vision. Cataract surgery is not 100 percent risk-free. You need to consider the risk factors versus the benefits of having surgery. After cataract surgery, there are many times when the clear capsule surrounding the lens and holding the intraocular lens becomes cloudy. The posterior capsule is left intact and can become hazy after surgery. This can be fixed by a Yag laser that opens the cloudy posterior capsule.

Grading the lens gives the eye surgeon an idea about how the cataract is affecting a person’s vision. It will help in planning the surgery. Common complaints of cataracts are blurred vision, trouble seeing or driving at night due to decreased vision, halos around lights, glare, loss of color brightness, trouble reading, needing more light to see, a decrease in contrast sensitivity, and trouble seeing street signs.

As well as grading the lens for cataracts, you need a complete eye exam before having surgery. Small pupils that will not dilate make cataract surgery more difficult. The lens is located behind the iris and getting to the cataract will be more problematic. Smaller pupils may require iris hooks, a Malyugin ring, or a beaver pupil dilator to open the pupil to gain access to the cataract.

Cataract removal surgery is one of the most common surgeries performed in the United States, with more than 4 million surgeries performed annually. It is also one of the most successful operations performed as well.

Before seeing a doctor, write down a list of questions you may want to ask. You need to provide the doctor with a list of the current medications you are taking. You should closely follow all the instructions given to you. They will be usually provided on paper. Make sure you use your medication as prescribed.

Grading is useful in documenting the type and severity of the cataract. It helps with providing important data in clinical studies. Cataract surgery is a great operation and the doctor grading your cataract helps them design the surgical procedure you will have done.

Dr. James E. Croley III is a respected eye surgeon and a Christian. He is the author of two books, Believing is Seeing and The Blinding of America. Order copies for your family and friends today.

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