Nott retinoscopy is a technique similar to MEM (Monocular Estimated Method). In Nott retinoscopy, a fixation card (typically 6/6 in size) is positioned 40 cm away from the patient’s eyes. The card can be held by the patient or mounted on a measurement scale. The subject is instructed to view the target binocularly using their … Read more
MEM is a dynamic retinoscopy technique involves the use of a retinoscope with a series of cards attached to its head using magnets, such as the Welch Allyn retinoscope. These cards have a central aperture that helps the examiner align their viewing axis with the subject’s visual axis. The cards contain targets, such as printed … Read more
Static Retinoscopy In static retinoscopy, the patient is instructed to focus on a distant target positioned 6 meters away, which is considered to be at optical infinity. The reason for using 6 meters as the standard distance for retinoscopy is that when light rays come from a source situated 6 meters away, they are typically … Read more
Glass: Crown glass , barium , flint glass , titanium oxide glass, lanthanum crown glass
The tear film is a complex mixture of substances that are produced by various sources on the surface of the eye, such as the lacrimal gland, accessory lacrimal glands, meibomian glands, and goblet cells. This film covers the surface of the eye, which includes the corneal and conjunctival epithelia, serving as a barrier between these … Read more
Optical properties: The optical properties of ophthalmic lenses encompass their unique characteristics that enable them to accurately refract and focus light, resulting in clear and precise vision. Mechanical properties: The mechanical properties of ophthalmic lenses encompass their physical attributes, including durability, flexibility, and resistance to impact or breakage, ensuring they can withstand everyday use and … Read more
Aberration refers to the inability of a lens to create a perfect image of an object, resulting in imperfections in the formation of images within an optical system.
When a patient needs separate vision correction for both distance and near vision, they can opt for lenses that integrate these corrections into two distinct areas on each lens. Each area possesses its own focal properties tailored for specific distances. Bifocals, as their name implies, consist of two distinct lenses with different focal points, accommodating … Read more
Progressive addition lenses are single-piece lenses that feature a smooth transition in curvature across the lens surface. The curvature gradually increases from the upper distance portion to the lower near portion. Unlike bifocal or trifocal lenses, progressive lenses offer a seamless solution for individuals with presbyopia, providing optimal dioptric power for all distances. This ensures … Read more
Accommodative convergence/ Accommodation ratio also known as AC/A ratio, is a measurement of changes in accommodative convergence in prism diopters induced when the patient exert or relax 1 diopter of accommodation. Changes in the accommodation are either evoked by placing plus lens which relaxes accommodation or by minus which activate accommodation or when a person … Read more