Understanding Visual Acuity and Why it’s Important

What is Visual Acuity?

Visual acuity measures the eye's ability to distinguish shapes and detailed objects at a given distance. Your acuity of vision is essential to detecting vision changes or impairments, as well as managing the overall health of your eyes.

There are four types of visual acuity, each being a threshold of which spatial dimension is measured. There have been many different ideas about how to define and measure visual acuity, but they can be defined by the following:

• Minimum (detectable) visible acuity: The detection of the presence or absence of an object.
• Minimum (separable) resolvable acuity: The small separation between two objects or features.
• Minimum recognisable acuity: The identification or recognition of a feature.
• Minimum discriminable acuity: A change in orientation, position, or size in a feature.

Everybody’s visual acuity is different and can change over time. There are, however, specific vision problems that can impact your ability to see sharply.

Impact on Visual Acuity From Vision Problems

Several vision problems can impact visual acuity. For example, visual impairments like myopia (nearsightedness), hyperopia (farsightedness), presbyopia, and astigmatism can all have symptoms such as blurred vision, double vision, vision field loss, and even flickering or flashes of light.

All these vision impairments can be detected through a professional eye test and then treated with visual aids, such as glasses and contact lenses, or laser eye surgery.

Anatomy of Sharp Vision

The entire anatomy of your eye is responsible for your acuity of vision. Basically, the role of your eye is to convert light into electrical signals called nerve impulses, which are then converted into images of our surroundings.

There are a few key anatomical parts of the eye that play an important role in visual acuity, specifically:

• Cornea: a clear covering on the front of the eye that transmits and focuses light entering the eye - this impacts sharpness and clarity of vision.

• Ciliary muscles: a circular muscle located behind the iris that relaxes and tightens to enable the eye lens to change shape for focusing.

• Macula: an area in the centre of the retina responsible for your central vision (what you see ahead of you). The macula contains special light-sensitive cells that naturally deteriorate as we age.

• Fovea: a small part of the macula that provides the sharp central vision needed for activities like reading or driving.

Understanding a Visual Acuity Test and Measurements

When it comes to a visual acuity check, you can undergo a visual acuity test with your ophthalmologist.

One test to determine visual acuity is the Snellen chart. The chart consists of 11 lines of block letters (of different sizes) that a patient reads from a distance of six metres. It has been used for over 100 years and was developed by Dutch ophthalmologist, Herman Snellen, in 1862.

Another visual acuity test is the Landolt ring (also known as Landolt C), a chart that measures the smallest gap a patient can resolve. The Landolt ring can be presented in isolation or surrounded by crowding bars.

When it comes to actually understanding vision test results like these, your ophthalmologist will measure and record your visual acuity using the 20/20 system (expressed by decimals or percentages). For example, visual acuity can be expressed as 0.8 (80%), 1.0 (100%), or 1.2 (120%). 1.0 means average vision and 2.0 is the highest possible value which indicates very sharp vision.

Visual Acuity vs. Diopters

It’s important to note that there is a difference between visual acuity measurements and diopter values. Visual acuity measures the sharpness of vision, while diopter values indicate the refractive power (strength) of the eyes. Your eyes' diopter values will inform what type of visual aid is best for you and, alternatively, if you’re eligible for laser eye surgery.

Factors Affecting Visual Acuity

Besides vision problems like nearsightedness and farsightedness, there are other factors that influence visual acuity, including:

• The size and shape of the eye and pupil
• Health-related issues such as cataracts, glaucoma or diabetes
• Prolonged stress and eyestrain
• Age-related macular degeneration

Sometimes, you can be born with certain vision problems like astigmatism or amblyopia (also known as ‘lazy eye’) which impact your visual acuity. Other times, eye injuries, your age, and even specific medical conditions can cause it to change.

Improving Vision

It’s important to schedule regular eye tests as they can successfully identify any refractive errors or issues with your visual acuity.

In certain cases, you may have to wear contact lenses or glasses. Your ophthalmologist will conduct an eye examination and determine your specific diopter values for each eye. Based on this, your lenses will be developed (or re-adjusted).

Another great option is laser eye surgery. At betterview, we offer Trans-PRK and Femto-LASIK laser eye treatments. After a free, 30-minute initial appointment at our shop, the ophthalmologist will confirm whether you’re suitable for laser eye surgery and help you get started if you’re interested.

Schedule your eye exam today for clearer vision tomorrow!

Laser eye surgery is a successful way to address various vision problems and improve your visual acuity altogether.

If you’re interested in booking an appointment with our team - don’t hesitate! Click here to schedule an appointment and kickstart your journey to 20/20 vision with betterview.