White to White IOLMaster, IOL Master, Intraocular Lens Calculations Zeiss IOLMaster
Carl Zeiss Meditec IOLMaster, White to White IOL Master, Intraocular Lens Calculations Zeiss IOLMaster Eye Cataract Surgery Eyes
W key, or Space (only when leaving [ACG] mode), or the appropriate button above. This optional
function is part of Software Option A and serves to measure the horizontal iris
corneal diameter and the position of the visual axis relative to the center of the iris.
The WTW is used for two applications:
In the first application, the Holladay 2 formula requires WTW as measuring
parameter in order to calculate the power of the intraocular lens.
The second application is for sulcus-supported intraocular lenses (especially for refractive surgery). As the "sulcus diameter (SD)" is not accessible (except by using ultrasound microscopy), the formula SD=WTW+1mm is often used here to find the suitable outer diameter of the IOL.
The position of the visual axis relative to the iris is still displayed. It
is advisable to know the position of the visual axis, e.g., prior to refractive
corneal surgery, in order to avoid any refractive surprises.
Note:
Align the instrument and make sure that the iris structures,
or the edge of the pupil, appear to be optimally focused. Confirm that
the patient is able to see the yellow fixation point and is looking straight at
it. If the patient fails to fixate properly, the visual axis will be out of
alignment, which may result in measurement errors.
Start the measurement using:
Pushbutton on joystick or
Foot switch
The iris is imaged and its center determined. The WTW result presents the horizontal diameter of the circle segments visible on the screen as lying around the iris.
The image is evaluated by locating and determining the transition from the conjunctiva
(white) to the cornea (colored iris).
Beside the WTW value, the deviation of the visual axis from the center of the iris is displayed. The respective values are given in millimeters with reference to a Cartesian coordinate system, the origin of which is assumed to be in the found center of the iris. If the visual axis is above the iris center, the Y value will be positive; if it is below, values are negative. X values left of the center are negative; those right of the center are positive.
After you released the measurement on the joystick, one image of the eye is displayed. After having checked for the correct detection of the iris, you must confirm the obtained results. Only then can the data be printed and saved.
Printout of the WTW image is possible in the WTW mode via Patient > Print current WTW images, or by pressing CTRL + P. The WTW measurement may be repeated if desired.
Note:
If the room lighting is inadequate, the software may fail to detect the iris or the fixation point sufficiently well. It is advisable to keep extraneous light away from the instrument front panel and the examined eye. You will obtain the best results with the examination room slightly darkened.
Measurement of the other eye:
The system registers automatically which eye is being measured (OD or OS).
All existing measured values of this patient are kept in memory and may be recalled when needed.
The measurement of the other eye is to be performed analogously to the previously measured eye.
Note: After every changeover to the other eye, the Overview Mode is automatically activated for coarse alignment of the instrument.
Aligning the instrument to the patient:
The two red ring marks on the side rails of the headrest serve for coarse vertical adjustment of the patient. The patient's eyes should be level with these marks.
In overview mode align the instrument to the patient's eye using the joystick. Vertical adjustment is by turning the control knob.
Ask the patient to look directly at the yellow fixation light in the middle. Focus on the iris, not on the peripheral points. Adequate room lighting will facilitate detection of iris structures. Avoid directly exposing the measurement eye and the front of the instrument panel to extraneous light.
Particularly take care that the visible right and left edge of the iris is not disturbed by reflections from lamps or windows. If the iris structure is not discernible, focus on the edge of either iris or pupil.
Adjust the instrument-to-patient distance until the six peripheral measuring light spots appear focused and are symmetrical with the cross hairs (centered), and the iris structures or the edge of the pupil appears optimally focused. After the image has been taken, the operator should check if the software correctly detected the edge of the iris. If the circle segments drawn in the image do not define the iris correctly, discard the result. Click on OK to confirm the results and save the data.
Note:
Only in ALM mode is the fixation light RED ;
otherwise it is always YELLOW .
Please check back at regular intervals for updates. Zeiss IOL Master
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A small study published in 2002 found lead exposure to be a risk factor; another study in December 2004, of 795 men age 60 and older, came to a similar conclusion. But larger studies are needed to confirm whether lead can definitely put you at risk, and if so, whether the risk is from a one-time dose at a particular time in life or from chronic exposure over years. Cataract treatment when symptoms begin to appear, you may be able to improve your vision for a while using new glasses, strong bifocals, magnification, appropriate lighting or other visual aids. Think about surgery when your cataracts have progressed enough to seriously impair your vision and affect your daily life. Many people consider poor vision an inevitable fact of aging, but Expert witness cataract eye surgery is a simple, relatively painless procedure to regain vision. Expert witness cataract eye surgery is very successful in restoring vision. 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Greater than 95% of those patients now enjoy improved vision. State-of-the-art Expert witness cataract eye surgery is now a safe, effective, and comfortable procedure performed almost exclusively on an outpatient basis. Most cataract surgeries are now performed using microscopic size incisions, advanced ultrasonic equipment to fragment cataracts into tiny fragments, and foldable intraocular lenses (lens implants) to maintain small incision size. Expert witness.
Note:
Align the instrument and make sure that the iris structures,
or the edge of the pupil, appear to be optimally focused. Confirm that
the patient is able to see the yellow 
fixation point and is looking straight at
it. If the patient fails to fixate properly, the visual axis will be out of
alignment, which may result in measurement errors.
;
otherwise it is always YELLOW 