Biometry 4% Flashcards
(52 cards)
What is used to calculate IOL power?
Axial length
K power(k curvature)
AC depth
White to White
Lens Constant (aka A constant
The distance from the front of the eye to the macula is—
Axial length in 100ths of mm
The measurement of K diameter
white to white
A number assigned to an IOL by the implant manufacturer depending on where the IOL sits in the capsular bag
Lens Constant (A constant)
Some designed to sit more posteriorly and some anteriorly.
Dr. can customize their IOL calculations based on _____
outcomes
All surgeons use the same generic IOL calculations. After a surgeon as performs a certain amount of cases they can do a retrorespective analysis of their refractive outcomes and make adjustments to these IOL calculations to customize them to their particular sx technique. This is called……..
Surgeons factor
What IOL calculation formulas are used for short eyes?
Hoffer Q
Haigis (multi-Variable Formula)
What IOL calculation formulas are used for longer eyes?
SRKT
Holladay II (multi-variable formula)
Which IOL calculation formulas are considered the most accurate? Why are they considered more accurate?
Haigis
Holladay II
Olsen
Barrett Universal II
(Because they use multi-variable formulas that take into account many different structures in the eye not just axial length and K readings)
What are the 3 main methods of A-scans?
Contact (ultrasound)
Immersion
Optical coherence (LASER light)
This method of Ascan uses ultrasound, there is no K compression, very accurate, uses Prager shell filled with BSS, requires training and skill.
Immersion
Ascan method that is not considered good enough anymore because K compression inevitable so it will always give a shorter axial length than any other method of Acan. Uses Topical anesthetic and is susceptible to operator error
Contact (ultrasound)
This method of Ascan uses LASER light
Optical Coherence (IOL Master)
What is the main advantage of ultrasound over LASER light Ascan?
Ultrasound can measure through dense media such a CAT or K opacification, LASER light can not.
These Ascan methods use Laser (not ultrasound), considered Good Standard, is non contact, no anesthetic needed, no risk of patient-patient contamination, very precise, Most accurate K’s, easy to operate, need good tear film, and intraocular lens calc software included.
IOL master and Lenstar
What do the peaks on the amplitude scan graph represent?
From left to right:
PCAPRS
probe, cornea, anterior lens, posterior lens, retina, sclera
IOL Master and Lenstar is also sometimes referred to as—-
Partial Coherence Inferometry
“Optical Biometry”
IOL and Lenstar uses _____to let you know accuracy of measurements.
Traffic Light Indicators (Red for bad, green for good)
IOL and Lenstar can measure through many types of media and eyes such as—-
Measures aphakic, silicone, and phakic eyes
IOL Master and Lenstar may have difficulty measuring through —-
very dense CATS and other media opacities due to using light beams
An Ascan is a ____measurement of the eye.
linear
An Ascan is a _____dimensional scan
1
An Ascan has scans in how many dimensions?
1
A Bscan measures in how many dimensions?
2
