ROUB Study Guide - Actual

ROUB Study Guide - Actual Questions and Answers 100% Verified If your biometry instrument has one pseudophakic eye-type setting, what is the only IOL material that can accurately be measured? Answer- Polymethyl methacrylate (PMMA) If a gain setting is increased in order to obtain a 100% tall retina and sclera echo, what type of cataract is being evaluated? Answer- A dense cataract What transducer frequency is generally used for a biometry A-scan probe? Answer- 10 MHz What is the velocity of a biometer that only uses an average velocity to measure the entire axial length? Answer- 1550 m/sec What is one of the most important features of a biometer? Answer- Display screen What are the velocity settings for a phakic eye? Answer- 1532 m/sec for the aqueous; 1641 m/sec for the lens; and, 1532 m/sec for the vitreous cavity What should the examiner do to reduce the presence of a reverberation echo created by a dense cataract? Answer- Reduce the gain What is the term for the electronic calipers that measure the distance between two or more anatomic interfaces? Answer- Gates Of the following settings on the biometer (gain, gates, A-scan probe frequency, eye type, and screen brightness), which cannot be changed by the examiner? Answer- A- scan probe frequency What is the proper sound velocity used to measure the distance between the anterior and posterior lens interfaces in a phakic eye? Answer- 1641 m/sec When performing immersion biometry, which gate in relation to the initial spike represents the cornea? Answer- Corneal gate is to the right of the initial spike What is the possible cause for a biometry instrument to indicate an unusually short measurement of a pseudophakic eye with a PMMA implant? Answer- Multiple signal of the echo with improper identification of the retina What biometer setting changes the degree of echo amplification? Answer- Gain 1 / 2

What is the term for the relative strength or amplitude of an echo displayed on a biometer? Answer- Reflectivity When measuring an eye that has no crystalline lens, the instrument should be set on which eye type? Answer- Aphakic What is the term for the "markers" or "cursors" displayed on the screen of a biometry instrument that provide electronic measurements of distance between two or more acoustic interfaces? Answer- Gates What is the term for the capacity of an ultrasound instrument to display two or more interfaces that are very anatomically close to one another as separate echoes?Answer- Resolution How does increasing the gain setting on the biometer affect the display echo? Answer- It increases the amount of amplification of the echo What is the range of ophthalmic biometry frequencies? Answer- 8-12 MHz How is the resolution affected when the gain is set at maximum? Answer- The resolution is less A non-focused sound beam is always utilized by which type of scan? Answer- Diagnostic A-scan What scan is used to obtain a two-dimensional image of the globe? Answer- Diagnostic B-scan What is the term for a one-dimensional amplitude scan? Answer- A-scan The strength of an echo is dependent on what three factors? Answer- Gain, difference in density, and proper alignment What type of scan uses Prager or scleral shells? Answer- Immersion A-scan How often should the filter of a biometry instrument be vacuumed? Answer- Once a month Measurement of axial length of the eye, thickness of an extraocular muscle, and tumor height are all within the definition of what term? Answer- Biometry What is the leading cause of an unplanned, post-operative refractive error? Answer- An error in the measurement of axial length An error of 0.1 mm in the axial length measurement can result in a post-operative refraction error of how many diopters? Answer- 0.25D

• / 2