Now go ahead and lay the lenses on top of each other and observe what the result is. So, our original prescription, -1.50 -2.00 x 045, actually yields a lens that has a prescription of a power of -1.50 at the 045 degree meridian and a -3.50 at the 135 degree meridian. With both of … Continued
Now you’re ready to place the cylinder power on the optical cross. Visualize the cylinder with the 180, 090, and 0 degrees. Remember that the degree you have been provided (045) is associated with the sphere power. For that reason, you can plug plano onto that meridian. You’ve already calculated the other principal meridian of … Continued
Plug the sphere power of the prescription into the sphere lens first. The sphere lens will include the 090 and 180 degree meridians, and when working with axis degrees that are outside these meridians, such as the prescription we’re working with now, you’ll need to include the 0 degrees on the opposite side of the … Continued
Click to download and print the course. To get the most out of this course, we recommend completing it in an environment free from distractions. Platform Instructions If you prefer to print the course and test questions, the PDF version is located below. Download & Print Courses are now broken down into Lessons. You can … Continued
+2.00 -1.50 x 090 The other meridian will always be exactly 90 degrees away. 90 degrees away from 90 degrees is 180 degrees. The power in this meridian will receive the cylinder power, -1.50. Now, visually imagine the lenses on top of each other. Combining the sphere lens and the cylindrical lens will result in … Continued
The Optical Cross This is a fundamental tool used by eye care professionals to represent the power of a lens along two principal meridians. It provides a visual way to understand and calculate the correction needed, and mastering the optical cross can help you interpret prescriptions more accurately. Visualizing a Prescription on an Optical Cross … Continued
Diabetic Retinopathy This is a complication of diabetes that affects the retina. High blood sugar levels can damage the tiny blood vessels in the retina, leading to leakage, swelling, or abnormal new vessel growth. In the early stage, called nonproliferative diabetic retinopathy, there may be no symptoms. As the disease worsens, the stage is considered … Continued
Ocular Conditions Affecting Vision Several eye conditions can impair vision, ranging from gradual changes to sudden, severe vision loss. A few of the common ocular conditions that impact visual health are: cataracts, glaucoma, diabetic retinopathy, and macular degeneration. Cataracts A cataract occurs when the eye’s natural lens becomes cloudy, preventing light from passing through clearly. … Continued
In compound astigmatism, both points of focus are located either in front of the retina, like in compound myopic astigmatism (CMA), or both are behind the retina, like in compound hyperopic astigmatism (CHA). As noted prior, the true powers will easily identify this type of astigmatism. CMA example: -2.00 -1.00 x 050; true powers are … Continued
Hyperopia Hyperopia, also commonly called farsightedness, is when the rays of light come to focus behind the retina. This is caused by either the cornea or lens curve shape being too flat (curvature hyperopia), or the eye is too short (axial hyperopia). In either case, the light focusing behind the retina causes blurred vision in … Continued
Refractive Errors The goal of the major ocular structures of the eye is to bring rays of light to a sharp focus on the retina. To elaborate even more, the goal is to bring rays of light to a sharp focus on the retina when the gaze is directed at optical infinity. Optical infinity is … Continued
Common Optic Nerve Disorders This visual pathway ensures that what we see is accurate, coordinated, and aligned between both eyes. Any disruption along this pathway, especially to the optic nerve, can cause significant vision problems or even permanent vision loss. Below are some of the most common disorders that impact the optic nerve. Optic Neuritis … Continued
Visual Pathway and Brain Processing The journey from light entering the eye to forming a clear image in your mind is a complex process involving many of the ocular structures described above. Now that we have covered these structures, let’s dive into the visual pathway. Light first enters the eye through the cornea, the window … Continued
Vitreous Humor The large space between the lens and the retina is filled with vitreous humor, a thick, gel-like substance that accounts for about 80% of the eye’s volume. It helps maintain the eye’s shape and removes debris that could interfere with light transmission if not removed. When debris becomes too large for the vitreous … Continued
Iris and Pupil Located behind the cornea and immediately in front of the lens, the iris is the colored part of the eye that controls how much light enters. It works like a camera aperture, adjusting the size of the pupil based on lighting conditions – expanding in dim light and constricting in bright light. … Continued
Cornea The cornea is like the window of the eye. It is the transparent outermost layer of the eye, responsible for focusing light and providing approximately 43 diopters of refractive power. The cornea consists of five distinct layers. The outermost layer is the epithelium, followed by Bowman’s Layer, the Stroma, Descemet’s Membrane, and finally, the … Continued
Certain prefixes are used to define phorias and tropias. As indicated in the table below, exo- means out, eso- means in, hyper- means up, and hypo- means down. So, looking at the examples provided, a right exophoria would be a tendency of the right eye to turn outward, whereas left esotropia would be a definite … Continued
Conjunctiva The conjunctiva is a thin, transparent layer of tissue that covers the front part of the eye (except the cornea) and lines the inside of the eyelids. This structure provides protection to the eye while keeping it lubricated by producing mucus and tears. The conjunctiva plays a role in immune defense through its immune … Continued
Exploring Ocular Anatomy and Visual Conditions Introduction Whether you’re new to the field or just brushing up, this course will give you a solid understanding of how the eye works and what can go wrong when things get a little blurry. We’ll explore the major parts of the eye, how they function together, and what … Continued
This assessment measures a vision professional’s knowledge of foundational topics important for the practice of opticianry. The candidate is assessed at an aggregate level and across 6 categories of knowledge. Categories Anatomy and Physiology Contact Lens Selling and Handling Instrumentation – Contact Lenses Instrumentation – Spectacles Optical Concepts and Principles Spectacles Selling and Handling The … Continued