Biomechanics of Incisional Surgery

FABIO A GUARNIERI

Corneal Biomechanics and Refractive Surgery

Springer

Año: 2014; p. 33 - 56

Cornea is the main responsi ble of the refraction of the eye. Its str uctural prope rties 6 are change d in Refra ctive Surgery [ 1 ], a techniq ue used in ophthalmol ogy to 7 modify the ref ractive properties of the optical syst em of the eye. It is used in the 8 correct ion of several ametropi as like myop ia, astigmat ism, and hyper metropia . 9 Among the different proce dures, radial keratotom y, photo refractive kera tectomy, 10 and keratomi leusis are common ly used in clinical prac tice. Radia l keratotom y [ 2 ]is 11 based on diamond knife relaxi ng incisi ons along the cornea, with maximum d epth, 12 but witho ut perforati on. The refractive change is reac hed by means of the action of 13 the intrao cular pressure over the relaxed cornea, b y steepeni ng whe re the thi ckness 14 is smaller (at the incisions) and by flattening the uncut central zone to corr ect 15 myop ia 1 (Fig . 3.1). 16 The calcul ation of the incisions is under taken com monly by means of nomo-17 grams or tables from previous exper ience. Some techniques involve the use of 18 closed equatio ns based o n simpl e mode ls. These techniq ues can leave the patient 19 with significa nt o vercorrect ion and undercorr ection [ 3 ? 6 ] sinc e they do not con-20 templat e the com plexity of the cornea (irregula r topog raphy, anisotropy, viscoel as-21 ticity, etc.) nor the overall struct ure (sclera, ocular mus cles, optical nerve and 22 eyelids effects, etc .). 23 Mech anical engi neering princi ples may be used to obtain a mathem atical mode l 24 of the corne a and provide h elp in the study of the corneal biom echanics, as well as 25 predict its behavior .