The skin on the eyelid is the thinnest on the body. Also there is hardly any sub-cutaneous fat within the eyelid particularly near the lid margin, obviously these factors mean it is essential to select the precise needle depth and hand pressure for the eyeliner procedure.
As you can see it is crucial for technicians to have a clear understanding of anatomy of the eyelid and its key structures. Tattooing over the lachrymal drainage ducts or puncta could potentially lead to impairment or closure of the lachrymal drainage apparatus resulting in chronic tear overflow problems.
Overworking the skin due to excessive pressure, excessive passes over the same area of skin, using incorrect angle for the specific needle can all result in excessive trauma and bruising.
During an eyeliner procedure it is common for small flecks of pigment to splash into the eye, this is far more likely with the use of coil machines and rotary pens, tattooing with the eye open, overfilling the needle tip, or due to the use of watery pigments. If pigment is left in contact with the eye surface for too long or if the client/patient rubs the eye when pigment is still present it can result in corneal abrasions. Rinsing the eye gently with saline will clear any pigment.