Some degree of pigment migration invariably follows cryosurgery of the retina. Immediately upon thawing, pigment granules lysed from the pigment epithelium of the choroid may migrate through the retinal tear and into the vitreous. Pigment migration may also occur through the subretinal fluid to form a deposit behind the macula, or a pigmented line representing the farthest advance of the retinal separation. Pigment deposited in the foveal area may impair macular function. The important difference between cryopexy and diathermy applications to the choroid is the apparent absence of coagulation of the tissue proteins in the cryosurgical lesion. The complications of pigment migration are perhaps the most serious observed with the cryosurgical method.
Sudarsky RD, Yannuzzi LA. Cryomarcation Line and Pigment Migration After Retinal Cryosurgery. Arch Ophthalmol. 1970;83(4):395-401. doi:10.1001/archopht.1970.00990030395002