Dioptric Ocular and Image Types

Dioptric Ocular

• A diopter separates two mediums.
• Light rays follow Snell's Law.
• Natural light is a superposition of electromagnetic waves.
• Light travels in straight lines in a homogenous medium.

Approximation of Equations

• Approximation for ray from object at infinity
• Light rays from an object at infinity converge on a point on one side of the surface.

Power of a Diopter

• Power is the reciprocal of the focal length in meters.
• A diopter's power is calculated using P = 1/f , where f is the focal length.

Types of Images

• Real image: image formed where light rays physically converge.
• Virtual image: image where light rays appear to converge, but do not actually intersect.

Eye Definitions

• Emmetropic eye: normal eye, with image focused on the retina.
• Myopic eye: eyeball too long, image focuses in front of the retina.
• Hyperopic eye: eyeball too short, image focuses behind the retina.
• Astigmatic eye: irregular curvature of the cornea, causing distortion of the image.

Eye Conditions (Myopia)

• Myopia is defined as an eye condition where light rays focus in front of the retina, making distant objects appear blurry.
• Myopia can be axial (longer eyeball) or refractive (increased cornea/lens power).
• Myopia is often corrected with concave lenses.

Eye Conditions (Hyperopia)

• Hyperopia is defined as an eye condition where light rays focus behind the retina, causing distant objects to be blurry.
• Hyperopia can be refractive (reduced cornea/lens power) or axial (shorter eyeball).
• Hyperopia is often corrected with convex lenses.

Corneal Astigmatism

• Astigmatism is a refractive error where the cornea or lens has an irregular shape, causing light to focus at multiple points, resulting in blurry vision, especially in images in different orientations.
• Astigmatism can be regular or irregular; regular astigmatism has a predictable shape, with parallel refractive curves.