Plan the channel and implant together
Choose the tissue preparation method and nomogram before setting channel geometry. Segment width, thickness and arc length interact with the channel’s diameter, width and depth. A channel designed for one implant system should not be paired casually with a different tissue size.
Both femtosecond-assisted and manual channels are described in CAIRS teaching. Dr Gunn uses a femtosecond laser for precise channel production. His all-femto approach also uses the laser to cut the donor implant, which is a separate step explained in Making the implant.
A manual channel option
The Rumex / LWVI CAIRS treatment set includes corneal marking and fixation tools, a depth-adjustable diamond knife, a vacuum stabilisation guide, CAIRS dissectors and insertion instruments. It supports manual channel creation and implantation without a femtosecond channel laser.
The recipient channel method and donor implant preparation remain separate choices. Select the manual technique’s incision depth, tissue plane and dissector geometry through training in that workflow.
Get radius and diameter right
The inner and outer channel sizes are diameters. The width of the channel is the radial distance between those circles:
With a 6 mm inner diameter and an 8 mm outer diameter, the radial channel width is 1 mm, because (8 − 6) ÷ 2 = 1. It is not 2 mm. The same relationship applies when calculating the width of a ring cut from donor tissue.
Record diameters in millimetres and tissue thickness or channel depth in micrometres. Confirm whether each field on your particular laser asks for a diameter, radius, width or depth.
Set the centre and depth deliberately
Identify the planned centre and axis from the clinical assessment and tomography. Maintain that reference through corneal marking and docking, and account for cyclotorsion. The Awwad CLEAR three-blade marker transfers the centration and axis references before laser docking. See its photo and marking demonstration in Instruments.
Read the pachymetry along the entire channel zone. A single central thickness value cannot describe the stromal cover around the full arc. In the femto-CAIRS wet-lab teaching, a channel at approximately 50% of local corneal thickness is discussed; the final depth must be chosen for the eye, tissue and technique.
Manual dissection has its own incision-depth and tissue-plane considerations. Train in that method before applying it, and use its technique-specific parameters rather than copying femtosecond channel settings.
Give the tissue room to pass
The channel needs enough clearance for the intended implant and its hydration state. The wet-lab example pairs a 1.0 mm-wide implant with a 1.5 mm-wide channel. This illustrates the clearance principle; select the final dimensions from your chosen nomogram and surgical plan.
A tighter channel can make insertion more difficult. A wider channel changes how the tissue lies within it. Consider those effects together with the tissue volume, rather than choosing width simply to make the next manoeuvre easier.
Place the incisions around the insertion plan
Plan access for the segment or segments you will insert, including which direction you will push or pull. Check the incision locations, segment start and end points, intended gaps and instrument access on the exported plan.
Once the channel has been made, identify the intended plane and confirm that the passage is open before advancing the implant. If there is unexpected resistance, reassess the plane and channel opening before continuing. A separator and the directional pushers and pullers are described on the Instruments page.
Check the plan before the cut
- Centre and axis, with the marking reference clear.
- Inner diameter, outer diameter and calculated radial width.
- Depth against pachymetry around the planned arc.
- Incisions and segment positions, including orientation and intended gaps.
- Agreement between the CAIRSPlan export, implant specification and device entry.
Teaching and further reading
Adapted from Dr David Gunn’s first-case, Ridley Lecture and LWVI wet-lab teaching, including his radius-versus-diameter teaching point. The geometry follows the CAIRSPlan planning framework.