SkinLab

View moves the camera only: drag to rotate, right-drag or two fingers to pan, scroll to zoom. Press pushes the skin with a fingertip and drags it. Scalpel incises to the cut depth, punch removes a cylinder of that depth, ablation has no depth limit. Laser treats a spot of the radius set below with an array of microcolumns. The wheel zooms whatever tool is selected.

Chemical reconstruction of skin scars: trichloroacetic acid put on the floor of a pitted scar with a wooden point. Click to dab it on a single pit, or hold and drag to paint it over an area; painted applications are laid close enough along the stroke to run together. Nothing is removed. The acid coagulates the protein in a small column where it stands, which frosts white, and over the following weeks that column is replaced by new collagen which lifts the floor. Depth and width follow the concentration, which is why the technique is used at strengths that would be reckless spread over a face. As with the laser, an application does nothing until the months after it are played out, so press Form scar. A course of sessions compounds.

Settings are those of a real device: pulse energy and zone density. Zone geometry follows the energy, using published measurements at 1550 nm, so depth runs from about 0.3 mm at low energy to beyond a millimetre at high, and width from 100 to 160 micrometres. A true microcolumn is well under one voxel wide, so the columns are carried as partial occupancy at the correct area fraction rather than drawn oversized: the pattern is a fine stipple, as it is on skin, and becomes visible as energy and density rise. Ablative vaporises a channel and leaves a ring of coagulated tissue around and below it; non-ablative leaves the coagulation zone alone without breaching the surface. Coagulated tissue becomes fresh collagen, and it is the coagulated volume that sets the remodelling dose, which is why carbon dioxide does more per pass than erbium glass at the same density. The array is anchored to the block, so sweeping the spot paints one continuous lattice; a second pass is offset by half a cell and interleaves with the first. Treating an existing scar also remodels it: over the three to six months after the pass it pales, releases some of its contraction, and its profile moves toward the level of the skin around it, so a raised scar flattens and a depressed one fills. One pass gives part of that, as in practice; repeat passes for more.

How far below the skin the depression settles, set when the healing run starts. A scar can be no deeper than the tissue that was lost, so on a shallow wound it stops at the floor of the wound whatever this says. Ice pick and boxcar scars sit at the deep end of this range, rolling scars at the shallow end.

The scar type applies to the next scar formed; scars that have already healed keep the type they formed with. Flat heals flush with the skin, hypertrophic raises a mound above it, atrophic leaves the wound filled short of the surface as a depression of the depth set below. Heals every open wound over a year: granulation advances from the walls, the scar contracts and pulls the surrounding skin in, a hypertrophic mound rises in proportion to depth, then the scar pales and partly flattens. Existing scar is kept and keeps maturing. Drag the slider to scrub.

Scar report scores the scars on the block in the terms the literature reports. Validate runs five scenarios against published behaviour and clears the block.

Fitzpatrick phototype. Melanin sits in the basal layer of the epidermis, so only the surface changes: the dermis and the fat beneath are the same whatever the type. Pigment is never laid down evenly, freckles show only on lightly pigmented skin, and a scar reads differently against each. Fresh scar looks darker and more violaceous the more pigmented the skin; a mature scar settles paler than its surroundings because it holds fewer melanocytes.

Scatters a field of atrophic acne scars and heals them out to a year in one run, so there is something to treat. The three sliders set the relative mix; leaving any of them at zero makes none of that type, so a field can be all ice pick or all rolling. Set them all to zero and severity decides the mix instead. Severity also deepens everything. They are placed in clusters rather than evenly, as they occur, and Undo removes the whole field.

Ice pick: a narrow opening running to a point, cut as a cone, 0.3 to 0.6 mm at the surface and 0.6 to 1.3 mm deep. Boxcar: round with sharp vertical edges and a flat floor, 0.9 to 2.0 mm across. Rolling: nothing is taken from the surface at all. A band of fibrous tissue is laid at the dermis to fat junction and the skin above it, which stays intact, is bound down to it. The dip is the pull of that band, which is why it is the one type subcision is aimed at.

Removes everything on one side of the plane so you can look at the layers in section. Drag the slider to sweep through the block.

Epidermis is drawn 0.3 mm thick (true 0.1 to 0.2) so it survives the voxel size; dermis 2.0 mm with an undulating base; fat 7.4 mm to the base of the block at 9.75 mm. The skin is held under anisotropic pretension along its tension lines (drawn faintly) with the block edges fixed: removing dermis lets the edges of a wound retract, and a contracting scar draws the surrounding skin inward. A fingertip loads an elastic membrane on a tissue foundation with published in vivo moduli: skin over fat about 30 kPa, bare fat 10 kPa, mature scar 120 kPa. The response is overdamped with a slow viscous creep and recovery, as skin shows under a Cutometer, so it does not bounce. Deformation fades with depth to the fixed base.