Program instruccions

1. Fill in the data according to the eye characteristics (they can be obtained with PENTACAM, ORSCAM or similar) and the arcuate values. A guidance table for the arcuate values can be found below:

• If the posterior corneal radius is not available, a reference value of 6.8 mm can be used (standard value of GULLSTRAND's eye).
• The program covers corneal diameter values (WTW) from 11 mm to 12.5 mm.
• It is recommended for the incision depth value to be a 90% of the peripheral pachymetry. This value can be obtained with PENTACAM, ORSCAM or similar. If the peripheral pachymetry value is unknown, an approximate incision depth value might be calculated using the following equation:
• 0,9 * 1,44 * CENTRAL_PACHYMETRY
• The incision width value is set as 1 mm by default. However, it can be modified as needed.
• The program covers intraocular pressure values up to 25 mmHg. Any value larger than that limit will be set to this maximum limit.
• The program covers central pachymetry values as of 0.4 mm. Any value smaller than that limit will be set to this minimum limit.
• The program covers flat radius values up to 9.4 mm. Any value larger than that limit will be set to this maximum limit.
• The program covers steep radius values as of 7 mm. Any value smaller than that limit will be set to this minimum limit.
• The program covers posterior corneal radius values from 6.4 mm to 6.8 mm.

2. Press the compute button to start the calculation process (it constructs the corneal geometry, applies the desired incisions and deforms the corneal geometry).

Results

1. The first plot shows a corneal topography with an aside scale showing the corneal power’s maximum and minimum values. The difference between those two values is the astigmatism to be treated.

2. The second plot is the generated corneal geometry.

• Before proceeding with the corneal correction evaluation, you should check that the incision depth has not been excessive and, therefore, that has not produced any perforations.
• This can be checked by turning the geometry and verifying that the incisions are not shown in the rear face of the cornea. If that’s the case, the calculation must be repeated reducing the incision depth value (first section of this page).

3. The third plot is the tangential topography.

• Yellow-ish colors represent areas with more incurvation whereas colder colors represent areas with more flattening. Average values for incurvation and flattening are shown in the next plots.

4. The forth plot shows a blue line in the central area, representing the average power correction in the most curved axis. The arcuate will flatten the power value of this curved axis. The incision length value can be found on the left side of the screen, above the curvature value.

5. The fifth plot shows a blue line in the central area, representing the average power correction in the most flat axis. The arcuate will increase the power value of this flattened axis.

6. The combination of the 2 last two values (the average power correction in the most curved and flat axis) is the astigmatic correction for the arcuate.

• It is necessary to compare this values with the corneal astigmatic powers (minimum and maximum) from the first plot to check if there is an over-correction, under-correction or if the whole correction is valid. If disparate values are shown with respect to the target values, repeat the calculation adjusting the input data.