Placeholder Image

Subtitles section Play video

  • This is Video 8 on

  • employing the Medmont E300 Corneal Topographers, Contact

  • Lens Module.

  • Lets open up a patient file,

  • select a Topography.

  • Click on 'Home',

  • and then,

  • 'Contact Lens'.

  • When you first start out select the manufacturers that are available from

  • North America, (or your Country)

  • you'll note

  • the boxes presently checked are all the manufacturers available

  • from North America

  • that have put their Contact Lenses designs into Medmont Studio.

  • You can click 'Ok'.

  • You won't have to open up this manufactures icon

  • unless a new manufacturer has been added

  • to a recent

  • release of the Medmont Studio software.

  • Otherwise you're just going to enter the patient's RX if it isn't

  • already entered in the patient file, so on the main window

  • where you enter patient information, if you

  • punch in your

  • patient Spectacle RX it automatically comes up in the contact lens design

  • window.

  • Next let's select

  • the

  • specific lens we want to fit on this eye.

  • Let's design for this patient a simple Multi Curve that we can get from any

  • lab in the world.

  • Say 'Okay'.

  • The software will then drop a theoretical contact lens on top of your

  • patients eye, and it

  • will

  • default the Base Curve generally very close to Flat K.

  • You will

  • manipulate the

  • contact lens parameters

  • to produce

  • the best possible

  • Fluorescein pattern.

  • And we start

  • by first determining

  • Visible Iris Diameter,

  • and we click on 'Annotate',

  • and then ,Ruler',

  • and

  • measure

  • Visible Iris Diameter.

  • We are getting a

  • close to 12 Millimeter

  • HVID.

  • We'll select to delete that annotation and you can do that by, right-clicking,

  • and then deleting.

  • Next let's pick up the contact lens,

  • and place it some more near the,

  • Geometric Center.

  • So ignore the Placido, and center the contact lens

  • in relationship

  • with the Sclera.

  • So looking at the white of the eye

  • around here

  • and placing your contact lens as it appears centered, not

  • to the Placido Rings that you can see

  • just outside of the lens, but more so

  • to the Iris or

  • Limbus.

  • Next

  • lets choose the lens diameter that we would prefer.

  • In this case we fit the patient with a 9.5.

  • 'Apply'. And

  • click your cursor in the center

  • and measure the Tear Film Clearance, or 'TFC' along the right hand side

  • here.

  • It's indicated to be 24 Microns.

  • For Fluorescein to be seen by

  • the human eye

  • it must be

  • in excess of 20 Microns.

  • In other words, for us to see Fluorescein behind our Slit Lamp,

  • we must have a

  • thickness of Tear Layer

  • and density of Fluorescein Molecules

  • somewhere in the neighborhood of 20 or more Microns.

  • If you want to see a nice even central Fluorescein Pattern

  • on your actual fit

  • you must have a Tear Film

  • Clearance at the Apex of at least

  • 20 Microns.

  • With 24 Microns

  • that would be comfortable, we are looking for somewhere between 20 to

  • 25 on a normal eye.

  • Next

  • take this white axis line and find the point on the graph

  • where the lens seems to land

  • on opposing sides,

  • and it appears

  • that on our , With the Rule Corneal Astigma,

  • this lens lands

  • very close to nine o'clock,

  • and again on its opposing

  • side at three o'clock,

  • so we have Apical Clearance of approximately 24 Microns

  • down to touch

  • at nine o'clock, you see the dotted section of the line here corresponding

  • with the dotted

  • section on the graph,

  • solid section of the line here corresponding

  • solid section there.

  • So we have our

  • 24 Microns Apical Clearance

  • heading down to three o'clock we have our touch

  • and then our edge lift,

  • our Apical Clearance

  • toward nine o'clock,

  • with our edge lift.

  • So this is

  • and ideal relationship to keep the lens on lateral center.

  • Then we take our axis line and drag it to the Vertical Meridian and we can see

  • that this patient has a fair amount of Tear Layer Clearance

  • heading toward twelve

  • and heading toward six o'clock,

  • dotted section of the line here corresponding with the dotted section of

  • the line here,

  • solid section of the line there corresponding with solid section here. If

  • we click our cursor at the edge of the inner pink circle which is

  • the, Optic Zone Junction.

  • we're showing 41 Microns heading North,

  • and

  • 85 Microns heading South, or inferior.

  • This is a

  • significant amount of Inferior Clearance and would likely cause

  • the lens to tilt and rock across the Vertical Meridian because there is

  • excessive

  • lift of the lens at twelve and six o'clock.

  • This is a Fluorescein pattern of the actual lens on eye

  • designed from our Medmont,

  • and you can see that

  • this contact lens

  • has an acceptable level of Apical Clearance.

  • Fluorescein can just be seen under the center of the contact lens, so this is

  • good, we have landing at nine o'clock and landing at three o'clock

  • with a healthy edge lift on both sides.

  • The problem however; is the

  • significant Inferior Lift,

  • and Superior Lift, that's causing the lens to tilt and also

  • ride high.

  • This patient needs a Toric GP Lens.

  • So let's go back to our contact lens and try to better designed it from our Medmont

  • software.

  • Click on 'Display' to bring up the, 'Edit' box again,

  • and select

  • 'Toric'.

  • Now we create two

  • Meridians of Curvature,

  • and 'Apply' that.

  • The same rules apply to the,

  • Toric Contact Lens.

  • We want to create a lens that lands at three and nine o'clock,

  • and lifts at twelve and six o'clock.

  • Presently our contact lens is

  • not landing across the Horizontal Meridian, the Horizontal Meridian,

  • you can also see is our Flat Meridian by that blue line.

  • So let's steepen the Base Curve along the Flat Meridian

  • by a half Diopter step.

  • On the Vertical Meridian,

  • we appear to be very near to bearing or definite bearing at, twelve and six.

  • We want our contact lens to lift so it can freely move with each blink

  • and create a good Tear Pump.

  • So let's

  • flatten the lens across the Steep Meridian

  • so that our contact lens will

  • be able to move with each blink. And

  • click 'Apply'.

  • Now we have a lens that lands at

  • three and nine o'clock

  • and along the Vertical Meridian it lifts

  • at twelve and six o'clock.

  • This would be ideal for a good RGP fit.

  • The last thing that one might do is adjust the, Optic Zone Size,

  • to soften its Peripheral Landing. Notice this narrow,

  • Point of Bearing,

  • and a very steep angle as the lens comes back toward the Cornea and touches.

  • Lets increase the Peripheral Curve Width,

  • reduce the, Optic Zone Size, slightly

  • and see what that does to those Points of Bearing. When we apply

  • notice how you shallow out

  • how that lens comes back towards the Cornea,

  • and creates a much wider

  • softer Area of Bearing.

  • Now here's the actual lens that was fit

  • by these same parameters,

  • and you notice

  • you've got virtually 360 Degrees of alignment, but

  • appears to be a very thin channel

  • at twelve and six o'clock which would allow the lands to freely

  • move

  • with each blink.

  • So the Tear Film definitely shows

  • what appears to be bearing at

  • three and nine o'clock and then

  • that bearing thins out throughout twelve and six o'clock to allow for the lens

  • to freely move

  • in the Vertical Meridian.

  • And we also have much better centration then we had

  • with the Spherical GP Lens.

  • This concludes

  • the section on Using the Contact Lens Module in your Medmont E300

  • Corneal Topographer

This is Video 8 on

Subtitles and vocabulary

Click the word to look it up Click the word to find further inforamtion about it