Myopia, commonly known as nearsightedness, is a vision condition where distant objects appear blurry while close objects remain clear. This happens because the light entering the eye focuses in front of the retina instead of directly on it. One of the key characteristics of myopia is its far point, which determines how far a person can see clearly without corrective lenses.
Understanding the far point of a myopic eye is crucial for diagnosing and managing nearsightedness. This topic explains what the far point is, how it affects vision, and how myopia can be corrected.
What Is the Far Point?
✔ Definition:
The far point is the maximum distance at which a person with myopia can see objects clearly without glasses or contact lenses.
✔ Key Features of the Far Point in Myopia:
- In a normal eye, the far point is at infinity, meaning a person can see distant objects clearly.
- In a myopic eye, the far point is finite and closer to the person, depending on the severity of myopia.
For example, if a person has a far point of 50 cm, they can see objects clearly only up to 50 cm. Anything beyond that distance appears blurry.
Why Does the Far Point Change in Myopia?
Myopia occurs due to improper focusing of light on the retina. The main causes include:
✔ Elongated Eyeball:
- The axial length (front-to-back length of the eye) is longer than normal.
- Light rays focus before reaching the retina, causing distant objects to appear blurry.
✔ Increased Corneal Curvature:
- The cornea is too curved, increasing the refractive power.
- This bends light too much, making it focus in front of the retina.
✔ Lens Abnormalities:
- The lens may be too thick or have excessive curvature, leading to incorrect light refraction.
These structural changes shift the far point closer to the person, limiting their ability to see distant objects.
How to Measure the Far Point in Myopia?
✔ Step 1: Remove Glasses or Contact Lenses
- The test should be performed without corrective lenses.
✔ Step 2: Identify the Blurry Point
- Look at a distant object and slowly bring it closer.
- The point where the object first appears clear and sharp is the far point.
✔ Step 3: Measure the Distance
- Use a ruler or measuring tape to determine how far the object is from the eyes.
- This measurement represents the far point distance in centimeters or meters.
For example:
- If a person’s far point is 20 cm, they have high myopia.
- If their far point is 1 meter, they have mild myopia.
Types of Myopia Based on the Far Point
Myopia severity is classified based on diopters (D), which measure the refractive error of the eye:
| Degree of Myopia | Diopters (D) | Far Point Distance |
|---|---|---|
| Mild Myopia | -0.25D to -3.00D | Beyond 1 meter |
| Moderate Myopia | -3.00D to -6.00D | 30 cm to 1 meter |
| High Myopia | -6.00D and beyond | Less than 30 cm |
The more negative the diopter value, the closer the far point, meaning worse distance vision.
How Does the Far Point Affect Daily Life?
✔ Challenges Faced by Myopic Individuals
- Blurry distant vision (difficulty seeing road signs, whiteboards, or TV screens).
- Strained vision when trying to focus on far objects.
- Frequent squinting to improve clarity.
✔ Benefits of Knowing Your Far Point
- Helps optometrists determine the correct lens prescription.
- Allows early detection of worsening myopia.
- Helps individuals understand their visual limitations and when to seek corrective lenses.
How to Correct Myopia and Adjust the Far Point?
1. Glasses and Contact Lenses
✔ Concave lenses (negative power lenses) are prescribed to shift the far point back to infinity.
✔ The strength of the lens is calculated based on the diopter measurement.
2. Refractive Surgery (LASIK, PRK, SMILE)
✔ These procedures reshape the cornea to correct the focusing issue.
✔ Effective for mild to severe myopia, permanently adjusting the far point.
3. Orthokeratology (Ortho-K)
✔ Special rigid contact lenses worn overnight to temporarily reshape the cornea.
✔ Reduces myopia progression and improves the far point during the day.
4. Lifestyle Changes and Myopia Control
✔ Limit screen time to reduce eye strain.
✔ Spend more time outdoors, as natural light may slow myopia progression.
✔ Follow the 20-20-20 rule (look at something 20 feet away for 20 seconds every 20 minutes).
Myopia Progression and Far Point Changes
Myopia often progresses during childhood and teenage years. The far point gradually gets closer, meaning vision worsens over time.
✔ Why does myopia progress?
- Increased near work activities (excessive reading, screen time).
- Genetics (if parents are myopic, children are more likely to develop myopia).
- Lack of outdoor activity and exposure to natural light.
✔ How to slow down myopia progression?
- Regular eye checkups to monitor changes in the far point.
- Using myopia control lenses (like atropine eye drops or specialized contact lenses).
Interesting Facts About Myopia and the Far Point
✔ The shortest far point recorded in extreme myopia cases is just 5 cm!
✔ In space, astronauts experience temporary vision changes, affecting their far point due to microgravity.
✔ The highest recorded myopia was over -30.00D, meaning the far point was just a few centimeters from the eyes.
The far point of a myopic eye is the maximum distance at which a person can see clearly without corrective lenses. Unlike individuals with normal vision, whose far point is at infinity, people with myopia have a far point that is much closer due to improper light focusing in front of the retina.
Understanding the far point helps in diagnosing myopia, prescribing the right corrective lenses, and managing myopia progression. With the right glasses, contact lenses, surgery, or lifestyle changes, myopia can be controlled, allowing individuals to see clearly at all distances.
If you experience blurry distant vision, consult an eye specialist to determine your far point and explore the best options for correction.