![]() The macula is always in line with the center of the pupil. Notice that lens’s optical center and its focal point both lie on the same straight line (green). Here is a diagram that illustrates a plus lens creating a focal point. In order to properly position the focal point on the macula, we have to know:Ī lens’s focal point is always in line with its optical center. How Do We Get The Focal Point Onto The Macula? Here is how I will represent the macula in a cross-section diagram. Therefore: Light must focus on the macula for vision to be clear. Important Take-Home: The macula produces sharp vision, the rest of the retina does not. The rest of the retina senses light, but does not produce sharp vision. It is on that tiny little red spot that light must come to a focus for us to see clearly. It appears as a small red spot inside the eyes. The macula makes up a very small portion of the retina, but it is the only portion able to produce sharp vision. Most of the retina cannot produce sharp vision. The retina is the entire layer that lines the inside back portion of the eyes. What is the Difference Between the Retina and the Macula? The macula is a small red area on the retina that is able to produce very sharp vision. In reality, we don’t just want the focal point to be on the retina, we want it to be exactly on the macula. Light comes to a focus precisely on the retina. Now let’s focus in on the area of interest from the diagram above the focal point forming on the retina. In actuality, this is much closer to the real-life proportions of the lenses we work with. Side note: Compared to ray diagrams in The Optics of Vision course, you might think that I’ve drawn an absurdly large lens in this diagram. A minus lens diverges light slightly, then the cornea (a plus lens) converges the light to a focal point that is on the retina. For clear vision, the focal point has to be exactly on the the retina ( from lesson: Basic Eye Optics).Lenses create a focal point ( from lesson: Lens Power).To gain a deeper understanding let’s first review a few important points from previous lessons: Why Are Pupillary Distance and Pupil Height Measurements So Important? In this lesson, you will learn why are these measurements so important, as well as how they are used during the lens edging & mounting process. Get it right and your customers will love their new glasses, get it wrong and they will promptly be back to return their glasses. Measuring the correct pupillary distance and pupil heights for your customers is quintessential to proper optical dispensing.
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