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Quizzes > Health & Medicine

Landolt C Test Online: Check Your Visual Acuity

Quick, free visual acuity test online. Instant results.

Editorial: Review CompletedCreated By: Sara Haj-HassanUpdated Aug 24, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper cut art eye chart glasses magnifying glass on coral backdrop quiz visual acuity challenge

This Landolt C test online helps you check your visual acuity by choosing where the C is open. Finish in minutes, see your score, and practice more with our eye test online quiz, try a fun eyesight test challenge, or push yourself with a pilot vision test.

What does "20/20" vision mean?
Seeing at 40 feet what a person with normal vision sees at 20 feet.
Seeing at 20 feet what a person with normal vision sees at 20 feet.
Seeing at 20 feet what a person with normal vision sees at 40 feet.
Seeing at 20 feet what a person with perfect vision sees at 20 feet.
A Snellen fraction of 20/20 indicates that you see at 20 feet what an average person with normal vision sees at 20 feet. It's considered the standard for normal visual acuity under high-contrast conditions. If your vision is worse than 20/20, you require corrective lenses or further testing. .
Which chart is most commonly used for measuring distance visual acuity?
Snellen chart
Humphrey visual field analyzer
Ishihara chart
Amsler grid
The Snellen chart, developed in 1862, uses rows of letters or symbols to measure distance visual acuity. It remains the international standard for screening distance vision. Other charts like the Ishihara test for color vision and the Amsler grid for macular function serve different purposes. .
What does a Snellen fraction of 20/40 indicate?
You can see at 40 feet what a person with normal vision sees at 20 feet.
You see at 20 feet what a person with perfect vision sees at 20 feet.
You must be at 20 feet to see what a person with normal vision sees at 40 feet.
You see at 40 feet what a person with normal vision sees at 40 feet.
A 20/40 result means your visual acuity is below average; you must be twice as close as a person with normal vision to see the same detail. This level of acuity often qualifies someone for corrective lenses. It does not indicate blindness but suggests a refractive error. .
Which part of the eye is primarily responsible for focusing light onto the retina?
Cornea
Optic nerve
Lens
Iris
The cornea provides about two-thirds of the eye's total focusing power by bending incoming light onto the lens and retina. While the lens fine-tunes focus (accommodation), the cornea's fixed curvature is the major refractive element. Damage to the cornea can significantly impair vision. Learn about corneal function.
When distant objects appear blurry but near objects are clear, this condition is called?
Myopia
Astigmatism
Hyperopia
Presbyopia
Myopia, or nearsightedness, occurs when the eye is too long or the cornea too curved, causing distant images to focus in front of the retina. As a result, distant objects appear blurred while near vision remains clear. Spectacles or contact lenses with negative diopters correct this by shifting the focal point onto the retina. .
What unit is used to measure the refractive power of lenses in the eye?
Candela
Radian
Diopter
Lumen
A diopter (D) measures the optical power of a lens, defined as the reciprocal of the focal length in meters. Eyeglass prescriptions specify diopters to correct nearsightedness or farsightedness. A higher absolute diopter value indicates stronger refractive correction. .
How often is it generally recommended for adults with no vision issues to have an eye examination?
Every six months
Every five years
Only when vision changes
Every two years
Regular eye exams every two years help detect changes in vision and early signs of ocular diseases. Even without symptoms, conditions like glaucoma or macular degeneration can develop. Your eye care professional may recommend more frequent visits based on risk factors. .
Which region of the retina has the highest concentration of cone photoreceptors for sharp central vision?
Peripheral retina
Fovea
Optic disc
Macular periphery
The fovea is a small pit in the center of the macula containing only cone cells, which provide the highest visual acuity and color discrimination. It is responsible for tasks such as reading and recognizing faces. Damage to the fovea severely impacts fine detail vision. .
What is the visual acuity level for better-than-normal vision, such as 20/15?
Seeing at 20 feet what a person with normal vision sees at 15 feet.
Seeing at 15 feet what a person with normal vision sees at 20 feet.
Seeing at 20 feet what a person with perfect vision sees at 20 feet.
Seeing at 20 feet what a person with impaired vision sees at 15 feet.
A 20/15 Snellen result means you can see at 20 feet what a standard observer has to be at 15 feet to see. This indicates sharper-than-average visual acuity. Athletes and pilots often aim for this level of vision. .
Which photoreceptor cells are responsible for color vision and detailed central vision?
Ganglion cells
Rods
Cones
Bipolar cells
Cones are photoreceptors concentrated in the fovea that mediate high-acuity color vision. There are three types - red, green, and blue cones - each sensitive to different wavelengths. Rods, by contrast, function in low-light conditions but do not detect color. Photoreceptor function.
What term describes difficulty focusing on nearby objects due to age-related loss of lens elasticity?
Presbyopia
Myopia
Hyperopia
Astigmatism
Presbyopia is an age-related condition where the crystalline lens loses flexibility, reducing near focusing ability. It typically becomes noticeable in the early to mid-40s. Reading glasses or multifocal lenses correct presbyopia by adding positive diopters. .
At what standardized distance is the Snellen eye chart typically viewed during a vision test?
3 meters
10 feet
6 meters
20 feet
In imperial units, the Snellen chart is read at 20 feet; in metric systems, it is often calibrated for 6 meters, which is almost equivalent to 20 feet. This distance ensures that the chart's optotypes pierce through the eye's relaxed focal state. Shorter distances require mirrors or scaled charts. .
What does the acronym "LogMAR" stand for in visual acuity measurement?
Logarithm of Maximum Angular Response
Logarithm of the Minimum Angle of Resolution
Logarithmic Measurement of Angular Radius
Linear Measurement of Aqueous Refractive
LogMAR stands for the Logarithm of the Minimum Angle of Resolution and provides a linear scale for visual acuity. Each 0.1 logMAR step represents a one-line change on standard charts. Unlike Snellen fractions, LogMAR is equally spaced and more suitable for research. .
How does a Landolt C chart differ from a traditional Snellen chart?
It uses numbers instead of letters.
It presents colored shapes to test color vision.
It monitors eye movements in low light.
It uses rings with a single gap oriented in different directions.
The Landolt C chart uses ring optotypes with gaps pointing in various directions to assess acuity without requiring letter recognition. It's often used in international testing to avoid language bias. Participants identify the gap orientation instead of naming letters. .
What is the primary purpose of using a pinhole occluder when measuring visual acuity?
To reduce the effect of refractive errors and improve clarity.
To dilate the pupil for better light entry.
To test peripheral vision.
To measure intraocular pressure.
A pinhole occluder allows only central light rays to enter the eye, bypassing peripheral refractive errors. If vision improves through the pinhole, uncorrected refractive error is likely the main cause of reduced acuity. Lack of improvement suggests other ocular pathology. .
According to US standards, what Snellen visual acuity is classified as legal blindness?
20/400
20/100
20/40
20/200
In the United States, legal blindness is defined as best-corrected visual acuity of 20/200 or worse in the better-seeing eye. Individuals at this level qualify for disability benefits and certain social services. The definition may vary slightly by country. .
What is the recommended luminance level for a standard visual acuity chart under photopic conditions?
100 candela per square meter (cd/m²)
85 candela per square meter (cd/m²)
50 candela per square meter (cd/m²)
10 candela per square meter (cd/m²)
Standard photopic chart testing requires a luminance of around 85 cd/m² to ensure consistent contrast and visibility. Too low or too high luminance can alter measured acuity. Clinical guidelines by ophthalmic societies recommend checking chart illumination regularly. .
Which chart is commonly used to assess near visual acuity?
Jaeger chart
Snellen chart
Landolt C chart
Ishihara chart
The Jaeger chart consists of paragraphs of text in various font sizes and is used to measure near acuity at reading distance. Patients read the smallest text they can comfortably. Snellen and Landolt C charts evaluate distance acuity, while Ishihara tests color vision. .
Which ophthalmic device is primarily used for subjective refinement of an eyeglass prescription during an eye exam?
Jackson cross-cylinder
Retinoscope
Autorefractor
Phoropter
A phoropter holds multiple lenses that the patient compares in a subjective refraction process to determine the best corrective prescription. Autorefractors and retinoscopes provide objective measures but require phoropter refinement. The Jackson cross-cylinder is a lens used within the phoropter for astigmatism testing. .
Why is monocular testing of visual acuity important?
It improves overall binocular acuity.
It tests color discrimination under low light.
It measures depth perception more accurately.
It isolates each eye's performance and detects interocular differences.
Testing each eye separately reveals differences that binocular testing can mask. Monocular acuity helps identify amblyopia, ocular pathology, and the need for asymmetric prescriptions. It also establishes baseline performance for each eye. .
Which ocular condition would most directly reduce contrast sensitivity without necessarily affecting high-contrast visual acuity?
Refractive myopia
Conjunctivitis
Blepharitis
Early cataract (lens opacity)
Early lens opacities scatter light and reduce contrast sensitivity before high-contrast acuity is affected. Cataracts often present with glare and difficulty in low-contrast settings. Myopia mainly alters focus without significant scatter. .
Which assessment is specifically designed to measure contrast sensitivity?
Amsler grid
Ishihara plates
Snellen chart
Pelli-Robson chart
The Pelli-Robson chart displays letters at decreasing contrast rather than size. It quantifies contrast sensitivity, which is critical for real-world tasks like night driving. Snellen measures size thresholds, while Ishihara and Amsler assess color and macular function, respectively. .
Which visual pathway is primarily associated with processing high-acuity, color vision information?
Koniocellular pathway
Parvocellular pathway
Magnocellular pathway
Retinotectal pathway
The parvocellular pathway carries high-resolution color and form information from cone photoreceptors to the visual cortex. The magnocellular pathway transmits motion and low-contrast signals. Koniocellular cells have diverse functions, and retinotectal contributes to reflexive eye movements. .
What is the typical size of each letter stroke on the 20/20 line of a Snellen chart in terms of visual angle?
Half a degree
Five minutes of arc
One minute of arc
Two degrees
Each stroke width on the 20/20 line subtends exactly one minute of arc at the standardized testing distance. Five minutes of arc is the overall height of the optotype. These precise angular measures allow consistent acuity testing across settings. .
How is the Minimum Angle of Resolution (MAR) calculated from a Snellen fraction?
Denominator divided by numerator
Numerator plus denominator
Numerator divided by denominator
Denominator minus numerator
MAR equals the Snellen denominator divided by the numerator, giving the size of the smallest resolvable angle in minutes of arc. For example, 20/40 yields a MAR of 2. This metric underlies the LogMAR conversion. .
What is the LogMAR value corresponding to a Snellen acuity of 20/40?
0.200
0.301
0.500
-0.301
LogMAR is calculated as log10(MAR). For 20/40, MAR=40/20=2, so LogMAR=log10(2)=0.301. Positive values indicate worse-than-normal acuity, while negative values indicate better acuity. .
If a patient's visual acuity improves by two or more lines when using a pinhole, what does this suggest?
Presence of uncorrected refractive error
Correlation to neurological disorder
Optic nerve atrophy
Macular degeneration
Significant improvement with a pinhole indicates that refractive error (myopia, hyperopia, or astigmatism) is limiting visual acuity. Ocular pathologies like macular degeneration do not typically improve with pinhole testing. This helps differentiate refractive vs. organic causes. .
At approximately what wavelength of light are rod photoreceptors most sensitive?
450 nm
498 nm
555 nm
650 nm
Rods peak in sensitivity around 498 nm, in the blue-green portion of the spectrum. This scotopic peak explains why night vision favors those wavelengths. Cones peak at longer wavelengths around 560 nm. .
On the 20/100 line of a Snellen chart, what is the Minimum Angle of Resolution (MAR) in minutes of arc?
0.5
5
1
20
MAR equals the denominator divided by numerator: 100/20=5 minutes of arc. This means each optotype stroke subtends 5?. Lower MAR values correspond to better acuity. .
In LogMAR notation, do lower scores represent better or worse visual acuity?
Better visual acuity
Only color vision
Worse visual acuity
Unchanged acuity
Lower LogMAR values (including negative) indicate better visual performance. A LogMAR of 0 equals 20/20, negative values are superior, and positive values are inferior. This linear scale is advantageous for statistical analysis. .
Which eye disease is characterized by degeneration of the central retina leading to loss of central vision?
Age-related macular degeneration
Retinitis pigmentosa
Glaucoma
Diabetic retinopathy
Age-related macular degeneration (AMD) affects the macula, the central retina, causing central vision loss while peripheral vision remains. It's the leading cause of vision impairment in older adults. Early detection and treatment can slow progression. .
How frequently should a calibrated digital visual acuity display be checked for accuracy?
Only at installation
Every five years
At least once a year
Every month
Clinical guidelines recommend annual calibration of digital acuity displays to maintain chart luminance and optotype size accuracy. Frequent checks prevent measurement drift over time. More frequent calibration may be needed in high-use settings. .
Which factor is most critical for accurate Snellen acuity measurement in a clinical setting?
Ambient temperature
Patient's height
Proper chart luminance
Examiner's position
Consistent chart luminance ensures correct contrast for optotype recognition. Too little or too much light can artificially worsen or improve measured acuity. Other factors like test distance and patient posture are important but secondary to luminance. .
For pediatric visual acuity testing, which symbol-based chart is commonly used?
Ishihara plates
Snellen letters chart
Lea symbols chart
Landolt C chart
The Lea symbols chart uses easily recognized shapes (circle, square, house, apple) suitable for young children who cannot read letters. It maintains standard optotype sizes and spacing, enabling reliable acuity assessment. .
How does reducing pupil size (down to about 2 mm) affect visual acuity?
Has no impact on acuity.
Significantly worsens refractive error.
Eliminates chromatic aberration completely.
Increases depth of focus but can introduce diffraction effects.
A smaller pupil increases depth of focus, reducing defocus blur, but diffraction at very small apertures can degrade image quality. The trade-off depends on pupil diameter and lighting. Ideal acuity often occurs at intermediate pupil sizes. .
How many optotypes are there typically on each line of a standard Snellen chart?
Three
Four
Six
Five
Standard Snellen charts have five optotypes per line to balance statistical reliability and testing time. Consistent item count per line ensures equal scoring weight. Some research charts use different counts for LogMAR, but Snellen maintains five. .
Which type of higher-order aberration, often quantified by Zernike coefficients, most commonly degrades best-corrected visual acuity?
Coma
Spherical aberration
Trefoil
Chromatic aberration
Spherical aberration, where peripheral rays focus at different points than central rays, often limits peak visual performance even after refractive correction. Wavefront-guided procedures target this aberration to enhance acuity. Chromatic aberration and coma also affect vision but are less impactful in optimized optics. .
What is meant by the "crowding phenomenon" in visual acuity testing?
Color desaturation in peripheral vision.
Difficulty in identifying an optotype when flanked closely by adjacent optotypes.
Reduced acuity in low-light conditions.
Glare-related loss of contrast.
Crowding refers to the reduction in letter recognition accuracy when optotypes are too close together, common in young children and amblyopia patients. Spacing optotypes farther apart reduces this effect and yields more accurate acuity. .
In the MNREAD reading acuity test, what term describes the smallest print size at which maximum reading speed is achieved?
Maximum print size
Threshold print size
Critical print size
Functional print size
Critical print size in the MNREAD test is the smallest font at which the reader maintains their peak reading speed. Below this size, speed declines due to acuity limits. This metric guides magnification needs in low-vision rehabilitation. .
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Study Outcomes

  1. Understand Visual Acuity Fundamentals -

    Learn how online tests of visual acuity measure the sharpness of your sight and what standard benchmarks like 20/20 vision represent. This knowledge forms the basis for interpreting any eye quiz or vision test quiz result.

  2. Perform Self-Guided Eye Assessments -

    Discover how to complete an interactive eye test quiz accurately at home, from distance letter charts to contrast sensitivity checks. You'll gain confidence in using online tools to gauge your vision health.

  3. Interpret Vision Test Quiz Results -

    Analyze your quiz outcomes to understand what your scores reveal about your visual strengths and weaknesses. You'll know how to differentiate normal variation from indicators of concern.

  4. Apply Diagnostic Positions Test Techniques -

    Gain practical experience with the diagnostic positions test to evaluate your eye movement and muscle coordination. This skill helps you recognize signs of ocular misalignment or nerve issues.

  5. Identify When to Seek Professional Care -

    Learn which quiz results and symptoms suggest it's time for a comprehensive eye exam. You'll be able to determine when to consult an optometrist or ophthalmologist for further evaluation.

  6. Establish Ongoing Vision Monitoring -

    Develop a routine for regular self-checks using free eye test quiz resources, ensuring you track any changes in your sight over time. This proactive approach supports long-term eye health management.

Cheat Sheet

  1. Snellen Chart Acuity Basics -

    The Snellen chart is the foundation for most online tests of visual acuity, presenting ratios like 20/20 to indicate clear sight at standard distances. Use the mnemonic "20/20 is clear" to remember that if you read the 20/20 line at 20 ft, your vision matches the normal standard. For instance, 20/40 vision means you see at 20 ft what someone with normal vision sees at 40 ft.

  2. LogMAR Scale for Precision -

    The Logarithm of the Minimum Angle of Resolution (LogMAR) converts Snellen fractions into a logarithmic scale, calculated as logMAR = log10(MAR). This metric is often used in research journals and high-precision eye quiz diagnostics because equal steps on the chart represent equal changes in acuity. In a vision test quiz, a 0.0 LogMAR corresponds to 20/20 vision, while positive values indicate poorer sight.

  3. Pinhole Test for Refractive Error -

    In an eye test quiz or clinical check, placing a small aperture (around 1.2 mm) in front of the eye can reduce blur from refractive errors by blocking peripheral light rays. If clarity improves through the pinhole, it signals uncorrected myopia or hyperopia. Think "pin - hole clears the goal" to recall that a clearer view suggests a need for corrective lenses.

  4. Diagnostic Positions Test (H-Test) -

    The diagnostic positions test gently assesses all six extraocular muscles using an "H" or cross pattern, revealing muscle imbalances or nerve palsies. Each gaze direction checks a specific muscle pair, ensuring coordinated eye movement and ruling out diplopia. Incorporate this step into a comprehensive eye quiz for a quick check of ocular motility.

  5. Amsler Grid for Central Vision -

    The Amsler grid is a key tool in many vision test quizzes to detect macular degeneration or central scotomas; patients report any waviness or missing squares when focusing on the central dot. Use a simple 10×10 grid at reading distance and note distortions for early AMD screening. Remember "Amsler Alert" to flag any grid irregularities promptly.

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