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LENSOMETER.pptx
- 1. LENSOMETER Ms. Khushi Kansal Assistant Professor Department of Paramedical Sciences, Subharti Medical College SVSU
- 2. INTRODUCTION A lensometer (also known as a lensmeter, lens neutralizer, focimeter or vertometer) is an optical instrument used to measure the dioptric vertex power, optical center, cylindrical axis, and prism of a lens. The lensometer is useful for establishing and verifying a reference refractive prescription before an eye exam. It is a device to measure the refractive power of an unknown lens (spherical power, cylindrical power, axis and prism power).
- 3. Types: Manual and Automatic Manual
- 4. Manual Lensometer The manual lensometer is an instrument that utilizes a battery-powered, LED illumination system to measure the precise powers of the sphere, cylinder, axis, add, and prism of a lens manually. The two most common types of manual lensometer include the American Cross and European Dot. The American cross lensometer: This lensometer consists of a series of uniform lines located at right angles to one another. The lines can be rotated by 360 degrees to determine cylinder power. The triple thin lines are designated as the “sphere lines” and the single thick line is designated as the “cylinder lines”. The European dot lensometer: This lensometer consists of a series of uniform dots located at right angles to one another. The dots can be focused in a circular or oval pattern. A protractor grid is used to determine the cylinder axis.
- 18. Automatic lensometer An automated lensometer is an automatic instrument that measures repeatable, fast, and reliable lens prescriptions. It is relatively less accurate but easily operatable compared to a manual lensometer. The values of each measure are then displayed digitally and can be printed or recorded manually.