Pupil measurement glasses12/6/2023 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. If the measurement is 6.4cm then your PD will be 64.Measuring the correct pupillary distance and pupil heights for your customers is quintessential to proper optical dispensing. If you have a reading of 6cm then type in our prescription page a PD distance of 60. Take off your glasses and measure the distance between the two markings. You will now have two lines directly in front of you whilst wearing your spectacles.Ask your friend to stand opposite you and mark on your lenses the position of your pupils with a non-permanent marker. Put your glasses on so that they are comfortable and steady.Please see the diagram above to help you further.Īsking a friend to help you using your current glasses Your friend will then read off the measurement to the centre of your left pupil. Ask your friend to close their left eye and for you to look directly into their right eye. ![]() Ask your friend to slide the ruler so that the zero value is in the centre of your right pupil and to keep the ruler very steady across your forehead.
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