- Hypermetropia is a condition in which distant objects are seen clearly, but nearby objects appear blurred.
- The near point shifts beyond 25 cm, making close-up tasks like reading difficult.
- The image of nearby objects forms behind the retina.
- Causes include reduced curvature of the lens or cornea and shortening of the eyeball.
- It is corrected using a convex lens of positive power, which converges light rays to focus the image on the retina.
Topics
Gravitation
- Concept of Gravitation
- Force and Motion
- Centripetal Force
- Kepler’s Laws
- Law of Orbit or Kepler's First Law
- Law of Areas or Kepler's Second Law
- Law of Periods or Kepler's Third Law
- Newton's Universal Law of Gravitation
- Uniform Circular Motion (UCM)
- Earth’s Gravitational Force
- Earth’s Gravitational Acceleration
- Mass and Weight
- Gravitational Waves
- Free Fall
- Gravitational Potential Energy
- Escape Velocity
- Weightlessness in Space
Periodic Classification of Elements
- Classification of Elements
- Dobereiner’s Triads
- Newland's Law of Octaves
- Mendeleev’s Periodic Table
- Insights into Mendeleev’s Periodic Table
- Modern Periodic Law
- The Modern Periodic Table
- Structure of the Modern Periodic Table
- Modern Periodic Table and Electronic Configuration of Elements
- Groups and Electronic Configuration
- Periods and Electronic Configuration
- Periodic Trends in the Modern Periodic Table
- Atomic Size
- Metallic and Non-metallic Characters
- Gradation in Halogen Family
Chemical Reactions and Equations
- Chemical Reaction
- Chemical Equations
- Balancing Chemical Equation
- Types of Chemical Reactions > Combination Reaction
- Types of Chemical Reactions > Decomposition Reaction
- Types of Chemical Reactions > Single Displacement Reaction
- Types of Chemical Reactions > Double Displacement Reaction
- Endothermic and Exothermic Processes
- Rate of Chemical Reaction
- Factors Affecting the Rate of a Chemical Reaction
- Chemical Properties of Carbon Compounds > Oxidation
- Chemical Properties of Carbon Compounds > Reduction
- Corrosion of Metals
- Rancidity
Effects of Electric Current
- Electric Circuit
- Heating Effect of Electric Current
- Introduction to Magnetic Effect of Current
- Right-hand Thumb Rule
- Applications of Biot-Savart's Law > Magnetic Field at the Axis of a Circular Current-carrying Loop
- Applications of Ampere’s Circuital Law > Magnetic Field of a Long Straight Solenoid
- Force on a Current-Carrying Conductor Placed in a Uniform Magnetic Field
- Fleming’s Left Hand Rule
- Electric Motor
- Electromagnetic Induction
- Galvanometer
- Faraday's Laws of Electromagnetic Induction
- Fleming’s Right Hand Rule
- Alternating current (AC) and Direct Current (DC)
- Electric Generator
Heat
Refraction of Light
Lenses
- Concept of Lenses
- Images Formed by Convex Lenses
- Images Formed by Concave Lenses
- Sign Convention
- Lens Formula
- Magnification
- Power of a Lens
- Combination of Lenses
- Defects of Vision and Their Corrections > Myopia
- Defects of Vision and Their Corrections > Hypermetropia
- Defects of Vision and Their Corrections > Presbyopia
- Apparent Size of an Object
- Use of Concave Lenses
- Use of Convex Lenses
- Persistence of Vision
Metallurgy
- Physical Properties of Metals
- Physical Properties of Non-metal
- Chemical Properties of Metal
- Reactions of Metals
- Reactivity Series of Metals
- Chemical Properties of Non-metal
- Ionic Compounds
- Metallurgy
- Basic Principles of Metallurgy > Concentration of Ores
- Basic Principles of Metallurgy > Extraction of Metals
- Basic Principles of Metallurgy > Refining of Metals
- Corrosion of Metals
- Prevention of Corrosion
Carbon Compounds
- Bonds in Carbon Compounds
- Carbon: A Versatile Element
- Hydrocarbons
- Straight chains, Branched chains, and Rings of Carbon atoms
- Functional Groups in Carbon Compounds
- Homologous Series
- Nomenclature
- Chemical Properties of Carbon Compounds > Combustion
- Chemical Properties of Carbon Compounds > Oxidation
- Chemical Properties of Carbon Compounds > Addition Reaction
- Chemical Properties of Carbon Compounds > Substitution Reaction
- Ethanol
- Ethanoic Acid
- Macromolecules and Polymers
Space Missions
School of Elements
The Magic of Chemical Reactions
- Chemical Equations
- Types of Chemical Reactions > Combination Reaction
- Types of Chemical Reactions > Decomposition Reaction
- Types of Chemical Reactions > Single Displacement Reaction
- Types of Chemical Reactions > Double Displacement Reaction
- Chemical Properties of Carbon Compounds > Oxidation
- Types of Double Displacement: Neutralization Reaction
The Acid Base Chemistry
- Properties of Acids > Physical Properties
- The pH Scale
- Acids, Bases and Their Reactivity
- Acid or a Base in a Water Solution
- Preparation and Uses of Baking Soda
- Preparation and Uses of Bleaching Powder
- Preparation and Uses of Washing Soda
- Preparation and Uses of Plaster of Paris
- Chemicals from Common Salt - Soap as a Salt
The Electric Spark
All about Electromagnetism
- Magnetic force
- Bar Magnet and Solenoid Analogy
- Right-hand Thumb Rule
- Applications of Biot-Savart's Law > Magnetic Field at the Axis of a Circular Current-carrying Loop
- Applications of Ampere’s Circuital Law > Magnetic Field of a Long Straight Solenoid
- Force on a Current-Carrying Conductor Placed in a Uniform Magnetic Field
- Electric Motor
- Electromagnetic Induction
- A.C. Generator
- Simple D.C. Motor
- Household Electrical Circuits
Wonders of Light 1
Wonders of Light 2
Striving for better Environment 1
- Abatement of Pollution
- Sustainable Use of Resources
- Key Points: Hypermetropia
Maharashtra State Board: Class 10
Hypermetropia and Its Causes
Hypermetropia (Hyperopia), also known as farsightedness, is a common vision defect where a person can see distant objects clearly, but nearby objects appear blurry. This occurs because light rays focus behind the retina instead of directly on it. It is common in newborn babies due to small eyeball size but often corrects itself as the eyeball grows.
Farsightedness
Hypermetropia occurs due to structural abnormalities in the eye that prevent proper light focusing.
Structural Causes:
- Shortened eyeball → Light focuses behind the retina, causing blurred vision.
- Flattened cornea or lens → Reduces the converging power of the eye, preventing proper focus.
- Increased focal length of the eye lens → Leads to improper light convergence.
- Stiffening of ciliary muscles → Reduces the ability of the eye to adjust its focus.
Maharashtra State Board: Class 10
Types and Symptoms of Hypermetropia
- Simple Hypermetropia: It is the most common type. Includes axial hypermetropia (short eyeball) and curvature hypermetropia (flat cornea/lens).
- Pathological Hypermetropia: It is caused by congenital (birth-related) or acquired conditions. Includes senile (age-related), positional, aphakic (absence of lens), and consecutive hypermetropia.
- Functional Hypermetropia: Occurs due to third cranial nerve palsy or internal ophthalmoplegia, causing paralysis of accommodation.
Hypermetropia is categorised based on severity (lens power required for correction):
| Severity | Power (Diopters, D) |
|---|---|
| Low | Up to +2 D |
| Moderate | +2.2 to +5 D |
| High | More than +5 D |
Symptoms of Hypermetropia:
- Blurred vision while focusing on close objects.
- Eye strain and fatigue while reading or working on screens.
- Headaches, particularly in the forehead region.
- Difficulty in adjusting focus, causing discomfort in switching from distant to near objects.
- Double vision in severe cases due to excessive eye strain.
Maharashtra State Board: Class 10
Hypermetropia Correction and Treatment
A. Spectacles and Contact Lenses
- Convex lenses (positive power lenses) are used to converge incoming light rays before they reach the eye lens.
- The eye lens then further converges them, forming a sharp image on the retina.
- Glasses and contact lenses are the most common correction methods.
B. Surgical Treatments for Hypermetropia
- Photorefractive Keratectomy (PRK): It removes a small portion of the cornea to improve refraction. May cause temporary corneal haze and astigmatism.
- Laser Epithelial Keratomileusis (LASEK): It is similar to PRK but uses alcohol to loosen the corneal surface before reshaping it.
- Laser-Assisted In Situ Keratomileusis (LASIK): It reshapes the cornea to correct the refractive error, eliminating the need for glasses or contact lenses.
CBSE: Class 10
Maharashtra State Board: Class 10
Maharashtra State Board: Class 10
