FREE ABO Ametropia/Ophthalmic Optics Questions and Answers
What theory explains why moving a plus lens away from the eye reduces its effective power?
According to the effective Focal Length (EFL) Principle, a lens's effective power varies with the distance it is from the eye. Because the focal length of plus lenses rises when the lens is moved away from the eye, the effective power of the lens decreases.
How does the peripheral lens distortion of spectacles change when aspheric lens designs are used?
In glasses, aspheric lens esigns are utilized to lessen peripheral dstotion. Contrary to spherical lenses, which minimize distortion and offer a broader, clearer field of vision, especially with higher prescriptions, these lenses feature curvatures that alter from the center to the edge.
What effect does an ophthalmic lens material's Abbe value have on its optical performance?
A lens material's dispersive power is measured by its Abbe value; higher values indicate less light dispersion into constituent colors, which lowers chromatic aberration. Higher abbe value materials provide for sharper, more color-accurate vision.
What is the primary purpose of putting an anti-reflective (R) coating to ophthalmic lenses in terms of lens coatings?
Applying an anti-reflective (AR) coating to ophthalmic lenses is primarily done to decrease reflections, thereby increasing light transmission through the lens. This reduces glare and improves vision. It is especially useful in low light and for cutting down on nighttime glare from headlights and computer screens.
What does the "index of refraction" mean when choosing materials for ophthalmic lenses in individuals with high refractive errors?
The amount that a lens material bends light depends on its index of refraction. By choosing a lens material with a greater index of refraction, patients with high refractive defects can have lenses that are lighter, thinner, more aesthetically beautiful, and more comfortable without sacrificing the lens's optical power.
What is the function of the "add power" in bifocal lenses?
In bifocal lenses, the term "add power" describes the extra magnification that is added to the bottom portion of the lens to help with near vision tasks. This is required for presbyopic patients whose lens flexibility has changed with age, making it impossible for them to focus or adjust for close work.
Which optical trait is the main distinguishing factor between an emmetropic and a myopic eye?
Blurred distance vision is a result of a myopic (nearsighted) eye's capacity to focus light rays in front of the retina rather than directly on it. A cornea that is excessively curved relative to the length of the eye or a longer axial length of the eye may be the cause of this disorder.
What is the impact of a lens's increased base curve on its optical power in ophthalmic optics?
The curvature of a lens's front surface is referred to as its base curve. A lens's optical power increases as its base curve is increased since this produces a steeper curvature, which strengthens the lens's ability to bend light rays.
What effect do variations in vertex distance have on a high-minus lens's effective power?
The effective power of high-minus lenses decreases when the vertex distance—the separation between the lens's rear surface and cornea—increases. This is due to the fact that light rays must travel a greater distance to reach the retina, which lessens the lens's converging
Which of the following mistakes will a four-point touch test miss?
What is the main way that astigmatism affects the retinal image quality?
Astigmatism is a refractive error caused by an irregular curvature of the cornea or lens, leading to light being focused at multiple points within the eye, either in front of or behind the retina, or both. This results in a distortion of the retinal image, affecting both horizontal and vertical lines, and can cause blurred or distorted vision at all distances.