Knowledge Base
2. Linking EyeSpace to your topographer

1. Bespoke Alignment Fit Quick-Start guide

8. Bespoke Alignment Fit Charl Laas

The EyeSpace Bespoke lens is a daily wear Rigid Gas Permeable lens and is available with the following parameters:

To start the design process start EyeSpace and follow these steps:

Select your Patient

A. Import your topography maps from your Medmont E300 topographer, Oculus topographer or Oculus Pentacam and then search for the patient by entering their name or surname.

or

B. Click on the menu option to import Medmont or EyeSpace export files, alternatively, you can create a patient and then enter corneal data manually to create a reference map.

  1. Manually import either EyeSpace (.eye) or Medmont E300 (.mxf) export files into EyeSpace.
  2. Create a new patient.
  3. Manually enter Corneal Data.
  4. Log out of your EyeSpace account.
  5. Exit EyeSpace.

Lens Design

  1. Select either the right or left design button.
  2. Select the topography map you want to use.
  3. Click ‘New Lens’.

The ‘New Lens’ window will open. Select the Bespoke icon and enter the HVID. The 'Refraction Type' dropdown box offers two options, 'Spectacle Rx' and 'Refraction Over Lens'. Typically you will use the 'Spectacle Rx' option when fitting regular corneas and the 'Refraction Over Lens' option when fitting irregular corneas or refitting from an old lens.

A. Spectacle Rx option:

  1. Select the Bespoke lens design.
  2. Enter HVID.
  3. Select the 'Spectacle Rx' option and enter the spectacle prescription. This is the preferred option where the cornea has a regular shape.
  4. Click ‘Done’.

B. Refraction Over Lens option:

  1. Select the Bespoke lens design.
  2. Enter HVID.
  3. Select the 'Refraction Over Lens' option'. This is the preferred option when fitting post refractive surgery and irregular corneas and a diagnostic trial set is available.
  4. Enter the Back Optic Zone Radius (BOZR) of the diagnostic trail lens in block R1 and R2.
  5. For rotationally symmetric/spherical lens designs, the R1 and R2 values will be the same.
  6. For back toric trial lenses, enter the flat BOZR in block R1, the steep BOZR in block R2 and the axis rotation of the flat BOZR on the eye in the block labelled 'Stab'.
  7. Enter the diagnostic lens back vertex power (BVP).
  8. Enter the over-refraction power as measured with a trial frame, followed by the correct vertex distance (VD) in millimeters. The correct VD is important for prescriptions above 4.00D.
  9. Click ‘Done’.

Lens Design Page

The lens design page is divided into three main sections:

The lens navigation menu shows a list of all the captured topography maps and lens designs for that particular patient.

Topography Map

  1. Left click on the topography map to view the topographical data.
  2. Left click on the drop-down list to switch the display to either a Tangential, Axial, Corneal Height or Elevation map and Placido disc (Medmont E300 only).

Lens Design

  1. Left click on the lens design to view the design page.
  2. Right click on the lens design to duplicate or delete the design.

B. Corneal, refractive and lens design data

  1. Corneal data.
  2. Spectacle prescription / diagnostic lens and over refraction data.
  3. Basic lens design parameters consisting of BOZR, AC and Lens diameter. These values are automatically calculated by EyeSpace based on the imported topography data, and given spectacle prescription and HVID.
  4. Advanced lens design parameters, allowing manual override of the BOZD, AC eccentricity, Edge Width, and Edge Radius of the lens.

5 After adjusting basic or advanced design parameters use the ‘Optimize AC’ button to automatically adjust the AC in order to restore the ideal lens-to-cornea fitting relationship.

  1. After adjusting any of the lens parameters, use the ‘Apply’ button to resimulate the lens design without optimising the AC.
  2. Once the design is complete, use the ‘Add to Cart’ button to place the lens order in the shopping cart.

C. Simulation section

At the top of the simulation section, five tabs are available providing more in-depth information regarding the lens design and lens-to-cornea fitting relationship.

A. Simulation

  1. By default shows the tear film profile of the horizontal meridian or the meridian specified by clicking on the NaFl lens simulation shown in the bottom half of the simulation screen (see point 6).
  2. Shows the tear film profile with a 90-degree angle in respect to the meridian shown above.
  3. Lens simulation which correlates with the NaFl pattern as observed when the lens is placed on the eye.
  4. The blue areas represent the area of lens bearing on the cornea.
  5. The average central Tear Film Thickness (cTFT).
  6. Shows the specific tear film thickness under the lens at the point of click. Clicking on this point will also change the meridian used for the tear film cross-section by drawing a line from where you have clicked through the centre of the cornea and then plotting that cross section (see Point 1).

B. Tilt and Position

The tilt, position, and stabilisation controls are now available in a separate tab. As before, adjusting these values does not change the lens parameters. Aim for equal lens bearing (blue zones) over the horizontal meridian, or a three-point touch, in the alignment curve zone.

  1. Unchecked, EyeSpace will automatically calculate the tilt of the lens. As a practitioner, you can decide if the tilt looks realistic, and in case it is not, manually change the tilt value.
  2. The tilt buttons show the principal meridians of the lens. Clicking on the tilt buttons will change the tilt value by 0.05 increments/decrements.

C. Optical Analysis

The optical analysis tab helps to visualise the optics of the cornea, tear lens system, and the final lens power. The plot shows the power of each element in air along each corneal meridian.

  1. The Ocular Refraction power (OR) shows the patient's contact lens prescription (vertexed spectacle prescription). For example, a patient with spectacle prescription -3.00D and vertex distance 12.0 mm will have an ocular refraction -2.90D.
  2. Tear power is the power of the tear lens formed between the cornea and the posterior surface of the contact lens.
  3. Ideal BVP is the ideal back surface power of the lens required to correct the patient's refractive error. This needs to take into account the tear power and is simply the ocular refraction minus the tear power.

D. Lens Schematic

  1. Lens sagittal height graph.
  2. Lens information (sagittal height, radius of curvature, and angle) at a given chord in the four quadrants of the lens.

E. Notes

Journal for clinical notes regarding the lens design and fit.

Ordering

Clicking the ‘Add to Cart’ button will display a dialogue to confirm the back vertex power of the lens. EyeSpace will automatically calculate the recommended values, which can be modified if clinically necessary.

  1. Back Vertex Power (BVP) is the power of the lens in air. EyeSpace automatically calculates the ideal BVP of the lens, and you will not need to make adjustments to this value unless troubleshooting is required.
  2. Shows the Residual Astigmatism as calculated with the lens on the eye. EyeSpace will automatically determine if a Bitoric or Compensated Bitoric design is required. You can override this option by selecting or deselecting the 'Supply as Spherical Power Effect (Compensated Bitoric)' checkbox option. If the residual astigmatism is more than -0.75Dc the visual acuity of the patient will be compromised. Revisit the corneal data, spectacle prescription and lens design for accuracy and if the residual astigmatism is still present rather place the order under review to allow your lens consultant to assist you with the fit.
  3. Places the final order in the shopping cart.
  4. Cancels the order, but will NOT delete the lens design data

Fit Example

When the lens is first designed, review and determine if the lens design is satisfactory, in most cases, when good topographic data is used, and the HVID is measured accurately, little if any tweaking of the lens parameters is required. Look at the cross-section and NaFl simulation to review the Central Tear Film Thickness (cTFT) and alignment curve angle. In some cases, the lens needs to be tilted to equalise the pressure under the alignment curve as in the example below.

Navigate to the Tilt and Position Page and click on the tilt button opposite from the unequal 'blue' pressure zone to tilt that section of the lens closer to cornea. Remember the aim is to balance the 'blue pressure' equally over the horizontal meridian under the alignment curve zone

Notice, the 'Lens Tilt' selection box is now ticked, indicating you manually adjusted the lens tilt. By clicking the round tilt buttons the lens tilt will increase or decrease by 5 micron increments. You can adjust the lens tilt by smaller or larger increments simply by manually entering the desired value.

By tilting the lens no lens parameters changed, only the lens simulation. However, tilting the lens can alter the ideal lens-to-cornea fitting relationship as in the example below. Tilting the lens decreased the cTFT causing central bearing which is not acceptable and will lead to central staining and lens decentration. The ideal cTFT for the Bespoke Alignment Fit GP lens is between 2 to 10 microns.

The Bespoke Alignment Fit lens parameters require adjustment to restore the ideal lens-to-cornea fit relationship. Steepening the BOZR will increase the sagittal height of the lens and therefore increase the cTFT. In reverse flattening the BOZR will decrease the sagittal height of the lens and therefore decrease the cTFT.

To increase the cTFT for the example above, steepen the BOZR by 0.05mm, from 8.10 mm to 8.05 mm. With the new BOZR entered, click the 'Optimize AC' button.

The Alignment Curve controls the lens-corneal angle of bearing and is essential to centre the lens over the horizontal meridian and allow vertical movement when blinking. The lens-corneal angle of bearing can be best visualised and assessed by the cross section tear layer profile of the alignment curve. The ideal fit is one where the lens-corneal angle is slightly negative (downward sloping) towards the edge in the horizontal meridian and in alignment or slightly flat in the vertical meridian to assist with the lens movement and lid attachment.

By clicking on the 'Optimize AC' button, EyeSpace will recalculate the alignment curve parameters to best match the entered BOZR and restore the ideal lens-to-cornea fitting relationship.

In the example above, the new lens design with the optimised cTFT is simulated in the lens design page. With the design complete, you can go ahead and click 'Add to Cart' to place the lens design in the shopping cart.