Optician Works Lens and Prescriptions Review Questions and Answers
7 views 0 purchase
Course
American board of opticianry
Institution
American Board Of Opticianry
What are single vision spheres used to correct?They are used to correct simple myopia and hyperopia. Since the front surface and the back surface of the lens are uniform in shape (although not curvature) the light rays entering it will all bend the same way and gather at a single point just like th...
Optician Works Lens and Pres criptions Review Questions an d Answers What are single vision spheres used to correct? ✅They are used to correct simple myopia and hyperopia. Since the front surface and the back surface of the lens are uniform in shape (although not curvature) the light rays entering it will all bend the same way and gather at a single point just like the ra ys of light through a spherical cornea. How does a single vision sphere look when viewed through a lensometer ✅When viewed through a lensometer, these lenses will produce a single focal point How do the rays of light bend in a single vision sphere lens? ✅Since the front surface and the back surface of the lens are uniform in shape (although not curvature) the light rays entering it will all bend the same way and gather at a single point just like the rays of light through a spherical cornea. What are single vision sphero cylinder lenses with power in some meridians and no power in others used to correct? ✅Single vision sphero -cylinder lenses with power in some meridians and no power in others are used to correct simple myopic astigmatism, and simple hyperopic astigmatism. When viewed through a lensometer, sphero -cylinder lenses will produce two separate focal points. Since the front surface is uniform in shape but the back surface of the lens contains two different curves some of the light rays entering it will bend more th an others. What are Single vision sphero -cylinder lenses with power in all meridians used to correct?✅Single vision sphero -cylinder lenses with power in all meridians are used to correct compound myopic astigmatism, compound hyperopic astigmatism, and mixed astigmatism. When viewed through a lensometer, what does a sphero cylindrical lens look like?✅When viewed through a lensometer, sphero -cylinder lenses will produce two separate focal points. Since the front surface is uniform in shape but the back surface of the lens contains two different curves some of the light rays entering it will bend more than others. What are lined bifocals used for? ✅Lined bi -focals are used to correct all the refractive errors plus the error or condition of presbyopia. These lenses will have two (bi) distinct areas of clear vision. These lenses have either a clear distance viewing area with no power (for emmetropes), a spherical distance viewing area, or a sphero -cylinder distance viewing area combined with the insertion of a segment that gives the wearer additional plus power or a reduced minus power that allows them to read and view objects at approximately 16 inches or "at near". What makes a lens a bi focal? ✅These lenses will have two (bi) distinct areas of clear vision. What types of distance viewing area can be placed in a bifocal? ✅These lenses have either - a clear distance viewing area with no power (for emmetropes) - a spherical distance viewing area (for myopes) or a sphero -cylinder distance viewing area (for astigmatics) combined with the insertion of a segment that gives the wearer additional plus power or a reduced minus power that allows them to read and view objects at approximately 16 inches or "at near". What is considered the "near" distance? ✅Approximately 16 inches What is an ST 25, 28, 35, 45? ✅ST 25, 28, 35, 45 bi -focals: ST stands for straight top, and the number indicates the width across the add segment. They will also be called Flat Tops or be marked FT. What is another term for ST bifocals? ✅They will also be called Flat Tops or be marked FT. - Rarely will you see the term D segment named for the D like shape they have when viewed from the side. Some describe the "half -moon" shape Which straight top bifocal is the industry standard ✅- ST 28s are the current industry standard for ST bi -focals. - ST 25s are available, but are no longer an industry standard, and should be replaced with ST 28s. When do you use an ST 35? ✅ST 35s are used when the patient is already wearing them and feels they need them. When do you use an ST 45? ✅ST 45s can be used to wean patients off Executives which are not recommended but it is best that you use ST 35's instead. What is a trifocal for? ✅Lined tri -focals are used to correct all refractive errors plus the error or condition of presbyopia. These lenses will have three (tri) distinct areas of clear vision. These lenses have either a clear distance area with no power (for emmetropes), a spherical distance viewing area, or a sphero -cylinder distance viewing area combined with the insertion of a added segments that gives the wearer additional plus power. Then an added segment that allows them to read and view objects at approximately 15 - 20 inches (near). A tri -focal lens has three distinct viewing areas that can be seen with the naked eye.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller twishfrancis. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $8.99. You're not tied to anything after your purchase.
