How to detect cataracts

You’ve finally arrived.

Undergrad, MCAT, medical school, Step 1. Red eye flights as you interviewed for residency. The stress of early January match when all your friends were relaxing on radi-holiday. Then the elation of match! Your early retirement from med school!

And now you are here, walking into clinic on your first day of ophthalmology residency. You pick up the chart outside the door: Cataract evaluation. Simple as that…find it, fix it, right?

Not so fast. What type? What grade? What tests? Does the patient meet indications?

This framework will provide the high level overview.

Cataract Type

There are 3 primary types of cataracts that represent 99% of the cataracts that you will encounter in clinic. Sure, kids will have congenital cataracts, and certain medications or systemic conditions will result in special cataracts, but these are not important to know at this point.

Cataracts types are defined by where the opacities exist within the lens and graded by how severe the opacities are at that location.

  1. Nuclear sclerotic cataract(NS) – Cloudiness of the nucleus, the central portion of the lens.
  2. Cortical spoking cataract (CS) – Swelling of the cortex causing spoke/wedge-like peripheral cloudiness.
  3. Posterior subcapsularcataract (PSC) – Opacity in the posterior capsule of the lens, often seen in younger individuals, steroid users, and diabetics. All else being equal, these are usually the most visually significant.

How to detect cataracts

Cataract Grading

Now that you know the types, how do you communicate their severity to others? This is a poorly defined topic. Some clinicians go with their gut feel. Others use visual acuity as a rough guide.

Cataract grading is important because patients will often give a very nebulous complaint about their vision getting worse, and it will be your job to figure out why. A cataract is often the cause, and only an accurate prior grading can help you determine whether the cataract has actually changed since the last visit. If it hasn’t, then you need to look for other causes of vision loss. Having a reliable grading system helps immensely.

In addition, surgical complication rates in training programs are high (up to 5% of cases vs. 0.2% post-training), and it is important to weigh the risk of surgery versus the potential benefit. For example, if a patient has both a cataract and macular degeneration, they may not actually benefit from surgery if the cataract is mild (Grades 1-2+). Knowing how much you would expect a cataract to affect vision helps you determine whether cataract surgery is worth the risk.

Finally, most programs aim to have third year residents hang out primarily in the operating room. They often won’t personally evaluate every patient before surgery. As a junior resident, you need to be able to accurately convey the characteristics of a cataract to your seniors so that they can determine the approach, plan which cases should go to less or more experienced residents, and anticipate surgical complications.

In 2002, The WHO published a simplified cataract grading scale. These images are directly from that paper:

Nuclear sclerotic (NS)

Best graded with slit beam at 30 to 45 degree angle to the cataract. In an early cataract, you will see that the central nucleus is actually more clear than the anterior and posterior embryonic layers of the lens:

How to detect cataracts

NS tr or 1+: Nucleus clearer than anterior/posterior sections
NS 2+: Nucleus equal to the anterior/posterior sections (same opacity level throughout)
NS 3+ Nucleus denser than anterior/posterior sections
NS 4+ Brunescent: Cataract completely opaque/brown

Cortical spoking (CS)

Best graded while visualizing with retroillumination. It may be difficult to retroilluminate if there is a concurrent NS cataract. By WHO criteria, think of the lens as a pizza and sum up the area of the peripheral spoke like opacities.

How to detect cataracts

CS 1+: ⅛ to ¼ of the total area
CS 2+: ¼ to ½ of the total area
CS 3+: ½ or more of the total area

Posterior subcapsular cataract (PSC)

Also best graded while visualizing with retroillumination. Like CS, PSC may be difficult to retroilluminate if there is a dense concurrent NS cataract.WHO criteria, graded on vertical height (in mm)

How to detect cataracts

PSC 1+: 1 mm to 2 mm
PSC 2+: 2 mm to 3 mm
PSC 3+: >3 mm

These basic measurements are combined into a cataract grade. You can have multiple types of cataracts at once and this can be written as the following:

OD: 2+ NS, 2+ CS, 1+ PSC
OS: 2+ NS, 1+ CS

Visual acuity

Beyond the cataract grade, there is a minimum visual acuity that is generally indicated for surgery. This varies from one training program to the next, and it is used to weigh the benefit of surgery vs. the high complication rate of residents. Some attendings in practice will do cataract surgery on 20/30, 20/25, and even 20/20 eyes if glare or nighttime symptoms exist! This is NOT our goal in training as our complication rates may be up to 50x higher than those of a veteran surgeon.

In most residency training programs, we aim for vision worse than 20/40 to 20/50 as a prerequisite for cataract surgery, along with symptomatically decreased vision. This vision can result from a combination of the above cataract types. It’s also important to rule out retinal and corneal etiologies of decreased vision before starting preop testing to maximize your chances of improving visual acuity postoperatively.

Once we determine that a patient needs surgery, we are ready for pre-op testing.


Treatment of cataracts is surgical. Although there are rumblings every few years about eyedrops which dissolve cataracts, there are not yet any evidence-based treatments except surgery. The most commonly performed cataract operation is phacoemulsification. Newer methods augment phacoemulsification with femtosecond laser, but these do not drastically change the underlying procedure.

Practice grading cataracts below, then click here to learn how to do pre-op testing and post-op evaluations.

How to detect cataracts

Cataracts are the leading cause of vision impairment, especially in seniors. According to the American Academy of Ophthalmology, cataracts affect approximately 25 million Americans age 40 and older. And by age 75, approximately half of all Americans have cataracts.

In older adults, the eye’s crystalline lens yellows and begins to harden, resulting in blurry vision, dull color perception, and difficulty seeing at night. Cataracts worsen over time, so it’s important to understand the stages of cataract progression in order to treat symptoms early and slow or even stop the progression of cataracts.

An ophthalmologist can provide you with an accurate cataract diagnosis and help you plan an appropriate course of treatment.

What is a Cataract?

As we age, the clear natural lenses of the eye begin to harden and yellow, becoming cloudy. This now opaque area over the lens is called a cataract. Cataracts prevent light rays from passing through the lens, which makes it difficult to see. You can develop a cataract in one or both eyes, but you can’t have more than one cataract per eye and cataracts cannot spread from one eye to the other.

What are the Symptoms of Cataracts?

Cataracts range in terms of severity, and the correct treatment depends on the degree of progression and type of cataracts you have. Early cataract detection signs include:

  • Cloudy Vision – One of the most obvious signs of early-stage cataracts is the appearance of noticeable fuzzy spots in your field of vision. These spots typically start out as fairly small aberrations, but over time they will worsen, making daily activities harder than they were before. If you experience sudden and persistent cloudy vision, see an eye doctor as soon as possible before your vision gets any worse.
  • Difficulty Seeing at Night – Patients with early-stage cataracts also report gradual worsening of nighttime vision. Cataracts often causes sufferer’s vision to darken or dim, and may also lead to slight tinges of brown or yellow. These early changes may not be noticeable during the day when there’s enough light to compensate for dimming vision, but they can be immediately noticeable at night.
  • Increased Light Sensitivity – For people with emerging cataracts issues, discomfort with bright lights will become increasingly noticeable and problematic. Consult your eye doctor if bright lights cause you to squint or close your eyes, or if you develop sudden headaches from flashes of bright light.
  • Appearance of Halos and Glare – As the eye lens hardens and becomes cloudy, cataracts sufferers may notice the appearance of halos and glare in their field of vision. Light passing through cataracts is diffracted, causing glare and ringlets around bright sources of light. These may be difficult to notice during the day, but can be immediately noticeable at night.
  • Eye Examination Results – In the earliest stages of cataracts, a person may have difficulty noticing changes to their vision. That’s why regular eye examinations are strongly recommended for older adults. Ophthalmologists can detect the presence of cataracts before sufferers report any noticeable vision problems.

How to Slow Down Cataract Progression

Small cataracts do not always develop quickly, so patients and their families usually have plenty of time to consider options and discuss treatment and/or prevention with an ophthalmologist. Some may stop progressing altogether after a certain point, but cataracts never go away on their own, and if they continue to grow they can cause blindness if left untreated.How to detect cataracts

Although cataracts are not reversible, there are some things you can do that may help slow down the progression of cataracts. Just be sure to speak with an eye doctor first to determine if cataract surgery is needed or recommended before your symptoms get worse.

  • Switch to an “eye healthy” diet that includes leafy greens, nuts, whole grains, citrus fruits, and cold-water fish rich in omega-3 fatty acids.
  • Wear sunglasses or a brimmed hat outside during the day to protect your eyes from sun exposure, which may speed up the progression of cataracts.
  • Talk to your eye doctor if you take eye drops to treat dry eyes or arthritic flare-up in the eyes, as some eye drops may speed up the progression of cataracts.
  • Ask about side effects of any prescribed medications that may speed up cataract progression.
  • Undergo regular eye examinations to track the progression of cataracts and adjust your course of treatment as necessary before the symptoms become more problematic.

Learn More About Cataract Surgery

If you think you have cataracts, you may be interested in learning about cataract surgery. Although surgery is not required for early-stage cataracts, it can help you avoid worsening vision problems and may even reduce or eliminate your need to wear glasses and contact lenses.

Download your free guide to learn more about cataract surgery, including how much cataract surgery costs, what’s covered by insurance, and how to determine if you’re a good candidate for surgery.