What nearsighted vision looks like −3.00 D

What Each Number Looks Like

The number on your prescription represents diopters of sphere (SPH). In China, Taiwan, and Hong Kong, people commonly describe this number by multiplying the diopters by 100, referring to units called 度 (dù).

Every nearsighted prescription has a specific optical far point. This is the farthest distance at which your eyes can form a sharp image without corrective lenses. You can calculate your far point in centimeters by dividing 100 by the absolute value of your sphere power: far point = 100 / |SPH|. Beyond this distance, light focuses in front of your retina instead of directly on it, creating blur.

The chart acuity below is a rough estimate from a formula published by Smith (1991), which links blur to pupil size and the size of the error. Real vision varies a lot from person to person.

−1.00 Diopters (100 度)

• Far point: 100 cm (about 3 feet).
• Everyday vision: A phone screen at 30 cm is sharp. A laptop display at 60 cm is completely clear. A person sitting across a table at 1 meter is right at the edge of your clear focus, so their face is recognizable. Beyond 1 meter, distance blur begins. Street signs down the block and bus numbers look soft.
• Estimated chart acuity: With an average indoor pupil of 4 mm, estimated uncorrected acuity is roughly 20/48–20/69. Under dimmer conditions at night with a 6 mm pupil, acuity drops to about 20/69–20/102.

See −1.00 in the simulator

−2.00 Diopters (200 度)

• Far point: 50 cm (about 20 inches).
• Everyday vision: Your phone at 30 cm is comfortable to read. At 60 cm, text on a computer monitor starts to lose sharpness. A face across a table at 1 meter is noticeably blurred, making subtle facial expressions hard to read. Television screens across a room, road markings, and highway exit signs appear smeared.
• Estimated chart acuity: Indoors with a 4 mm pupil, estimated acuity is roughly 20/88–20/133. In low light with a 6 mm pupil, acuity drops to approximately 20/132–20/199.

See −2.00 in the simulator

−3.00 Diopters (300 度)

• Far point: 33 cm (about 13 inches).
• Everyday vision: A phone held at a standard 30 cm distance remains clear. If you lean back from your desk, a laptop at 60 cm blurs considerably. A person sitting 1 meter away across a table is an indistinct shape. Street signs, store names across the street, and subtitles on a television screen are illegible without lenses.
• Estimated chart acuity: Indoors with a 4 mm pupil, estimated acuity is roughly 20/132–20/199.

See −3.00 in the simulator

−4.00 Diopters (400 度)

• Far point: 25 cm (about 10 inches).
• Everyday vision: You must hold a phone within 25 cm of your face to see small text cleanly. A laptop at 60 cm is completely out of focus. People across a room become blurry silhouettes without distinct features. Outdoor streetlights and signs appear as broad patches of color.
• Estimated chart acuity: Indoors with a 4 mm pupil, estimated acuity is roughly 20/176–20/266. At this level, resolving the large top line on a standard eye chart is difficult.

See −4.00 in the simulator

−5.00 Diopters (500 度)

• Far point: 20 cm (about 8 inches).
• Everyday vision: Your clear zone is limited to 20 cm from your face. Reading requires pulling books and screens closer than usual. A laptop at 60 cm is a diffuse blur. A face at 1 meter has no defined eyes or mouth. Moving around an unfamiliar space without glasses feels confusing.
• Estimated chart acuity: Beyond −4.00, visual acuity drops past 20/200. The big letter E at the top of a standard eye chart is already blurry.

See −5.00 in the simulator

−6.00 Diopters (600 度)

• Far point: 16.7 cm (under 7 inches).
• Everyday vision: Sharp focus ends just past the length of your hand. A phone held at chest level is unreadable without squinting. At 60 cm, your computer screen is a generalized field of glow. People across a room cannot be recognized by their faces alone.
• Estimated chart acuity: The big E at the top of the chart is illegible.

See −6.00 in the simulator

−8.00 Diopters (800 度)

• Far point: 12.5 cm (about 5 inches).
• Everyday vision: Clear sight exists only within five inches of your eyes. Holding a phone at an ordinary reading distance produces severe blur. Laptops, faces across a table, and street signs dissolve into overlapping circles of light and color. You depend heavily on contrast, bright colors, and movement to identify your surroundings.
• Estimated chart acuity: Well past the big E at the top of the chart.

See −8.00 in the simulator

−10.00 Diopters (1000 度)

• Far point: 10 cm (about 4 inches).
• Everyday vision:Focus is confined to the area directly in front of your nose. Everything beyond arm's length loses its structural edges. Faces across a table become soft patches of skin tone without individual features. Navigating an unfamiliar room without corrective lenses requires memory, touch, and general environmental outlines.
• Estimated chart acuity: Well past the big E at the top of the chart.

See −10.00 in the simulator

Why It Is Worse at Night

Many people notice their vision feels considerably more blurred after sunset. This happens because pupil size changes based on lighting. Watson and Yellott (2012) showed that ambient light level is the primary factor determining pupil size.

In bright daylight, your pupil constricts to a small aperture, often 2 to 3 mm. This acts like a pinhole camera, narrowing the incoming rays of light and reducing the size of the blur circle on your retina. In darkness, your pupil widens to let in more light, often reaching 6 mm or more. As the pupil dilates, the blur circle created by your uncorrected nearsightedness expands proportionally. The larger blur circle causes oncoming headlights, streetlights, and traffic signals to spread into broad halos.

Why Holding Things Closer Helps

If you are nearsighted, moving an object toward your face brings it within your far point. Because your eye focuses light too strongly for distant objects, it requires light rays that diverge from a nearby source to land cleanly on your retina. Once an object sits inside your far point, your eye can form a sharp image without any optical correction.

This distance adjustment stops working if you also have astigmatism. Astigmatism occurs when your eye has different optical powers along different meridians, like the surface of an oval ball rather than a round sphere. Instead of having a single far point, an eye with astigmatism has two different focal distances along different axes. Moving a phone closer may sharpen the vertical edges of letters while the horizontal edges remain blurred. You can explore how uneven curvature affects vision on our astigmatism simulator.

What the Simulator Leaves Out

This simulator models geometric optical defocus, but your actual experience of vision includes additional biological factors:

• Depth of focus: Real human eyes have natural optical aberrations and a small inherent depth of focus. For mild prescriptions, your everyday clarity may be slightly better than a pure geometric blur calculation suggests.
• Neural adaptation: People who live without correction for extended periods often adapt to the blur. The visual cortex learns to extract shapes, edges, and meaning from softened retinal images.
• Eye health: The tool illustrates only optical focus error. It does not reflect retinal health, corneal clarity, glaucoma, cataracts, dry eye, or other physiological conditions.

This simulation is designed solely for educational comparison and visual learning. It is not an eye examination, does not measure your prescription, and does not provide medical advice. Schedule an appointment with an optometrist or ophthalmologist for professional eye care and comprehensive vision evaluations.

Questions

Sources

• Smith G. Relation between spherical refractive error and visual acuity. Optom Vis Sci. 1991;68(8):591-598. doi:10.1097/00006324-199108000-00004
• Watson AB, Yellott JI. A unified formula for light-adapted pupil size. J Vis. 2012;12(10):12. doi:10.1167/12.10.12