In-Depth Notes on Electromagnetic Radiation, Eye Anatomy, and Vision

Different forms of energy are present in electromagnetic radiation.
Electromagnetic spectrum ranges from ultraviolet (UV) at high energy (around 350 nm) to infrared (IR) at low energy (up to 750 nm).
Visible Spectrum: The spectrum of light that can be detected by the human eye, ranging from violet (350 nm) to red (750 nm).
The visible spectrum is perceived through cone cells in the retina, specifically three types: red, green, and blue cones.

Color perception involves the combination of inputs from three cone types:
- Red cones detect red wavelengths.
- Green cones detect green wavelengths.
- Blue cones detect blue wavelengths.
The varying intensity of activation of these cones leads to the perception of different colors (ROYGBIV: Red, Orange, Yellow, Green, Blue, Indigo, Violet).

The curved shape of the cornea is essential for proper light refraction; flat surfaces would not refract light efficiently.
Light travels through different mediums (air to water) causing it to bend towards the normal (midline).
Refraction: The bending of light as it passes from one medium to another.
The cornea and lens work together to focus light onto the retina.

Visual Acuity: Sharpness of vision, measured as the ability to see an object clearly at a specific distance, usually assessed during eye tests.
20/20 vision means the ability to see a standard size letter from 20 feet away.
Myopia: Nearsightedness; able to see near objects clearly but distant ones are blurry.
Hyperopia: Farsightedness; able to see distant objects clearly but near ones are blurry.
Legally Blind: Defined as having 20/200 vision or worse.

Diopter (D): A unit of measurement for the optical power of lenses.
A negative diopter indicates a concave lens for myopia; a positive diopter indicates a convex lens for hyperopia.
Using a prescription, one can determine the necessary power for clear vision at varying distances.

Convex Lens: Positive lens that converges light, used for hyperopic patients.
Concave Lens: Negative lens that diverges light, used for myopic patients.
Bifocals and Trifocals: Lenses designed for people who require different prescriptions for distance and near vision.

Glaucoma: Increased intraocular pressure that can damage the optic nerve, leading to vision loss. Commonly affects African Americans.
Cataracts: Clouding of the lens, age-related and common in all individuals over time.
Macular Degeneration: Loss of central vision, primarily affecting older adults; smoking increases risk.
Diabetic Retinopathy: Damage to the blood vessels in the retina due to diabetes; a leading cause of blindness.