A.D. Semyonov, A.V.Doga, G.F.Kachalina,
K.Okuyama, I.A.Alisov, N.A.Semyonova
Specific Features of Clinical Course in Photoastigmatic Refractive Keratectomy with the “Profil-500″at Different Terms Postoperatively
The work analyzes the clinical course of PARK performed using the “Profil-500″ in 250 eyes with compound myopic astigmatism to 5.0D with myopia to 10.0D. Operation was done through transepithelial access. ln all cases complete epithelialization of the cornea was recorded within 24－48h. By 6－12 months postoperatively and until 3years of follow－up the cornea of eyes operated on was comPletely transparent in 91.2％ of cases; opacities of 0.5－1 degree Were found in 8.8％ of cases which did not affect final refractive result.
Numerous studies investigating the condition of the cornea at different terms after photorefractive keratectomy(PRK) and photoastigmatic refractive Keratectomy(PARK) indicate tnat tne corneal syndrome is the typical feature of clinical course in the early postoperative period of these excimerlaser interventions in myopia and myopic astigmatism. The degree of syn drome indetermined by the type and area of erosion surface，time and period of cornea epithelialization，and condition of corneal epithelium anu stroma by the moment of completing epithelialization. Many authors consider the above facts to play an important role in the further development of subepithelial fibroplasia which forms corneal opacities of different degrree leading to unpredictable regression of postoperative refractive result[1,3,6,9,12,13]
Notably, from literature, the techniques of PRK and PARK with different foreign excimer laser devices are performed with preliminary scarification of the corneal epithelium [4,5,7,8]. Thus, it’s necessary to stress that the device “Profil-500″ elaborated at the Center of Laser Surgery of the Eye Microsurgery Complex, like all previous Profil models of several generations ,allows transepithelial correction of myopia and myopic astigmatism i.e., without preliminary scarification of epithelium.
The objective of the work is to study clinical course of the postoperative period after transepithelial PARK with “Profil-500″ on the basis of postoperative results.
Material and methods
PARK was performed in 250 eye sof 131 patients aged 18 to 45 years with compound myopic astigmatism to 5.OD with myopia to 1O.OD. The follow－up was 3 years.
In all cases the operation was performed by transepithelial method, i.e., with subsequent evaporation of epithelium, Bowman’s membrane and superficial layers of the corneal stroma. The operation lasted not more than 1.5 min. No intraoperative complications were recorded．
Biomicroscopy of the anterior sector in eyes operated on was performed using slit-lamp(“opton”,Germany). To evaluate tne pattern and duration of corneal epithelialization and find defects in it, we used fluorescein probe according to routine method with the
use of 1% fluorescein solution.
We evaluated in the postoperative period(a) the degree of corneal syndrome and subepithelial fibroplasia according to the classification developed at the Eye microsurgery Complex(Kornilovsky I.M.,1995) [2]; (b) degree of corneal opacities according to the world numeric classification accepted in excimer laser practice.
Results and discussion
In most eyes operated on (184eyes-73.6%)，irrespective of the degree of initial astigmatism and sphere equivalent(SE)，We found epithelial form of corneal syndrome manifested by minimal involvement of corneal stromal layers adjacent to ablation zone. In these cases ablation zone was completely covered with epithelium within 24－36h postoperatively; edema of superficial corneal stromal layeres adjacent to intervention zone was rather mild or almost absent. Photophobia and lacrimation disappeared 1-2 days postoperatively as a rule. In 66 eyes(26.4%) stromal type of the corneal syndrome was recorded which was accompanied by moderate edema of all stromal layers in ablation zone. Notablv, in these eves the initial SE varied from 8.25 to 15.0 D, being more than 10.0 D on average. This required the removal of great volume of tissue and, thus, the use of greater energy and pulse number for photochemical evaporation of the cornea. Complete epithelialization in these eyes was recorded 36-48 h postoperatively; stromal edema gradually decreased with epithelialization and almost disappeared by day 5-7 postoperatively. Notably, we found no cases of mixed type of the corneal syndrome consisting in longer epithelialization to 72 and more hours postoperatively and pronounced stromal edema of entire ablation zone with signs of descemetitis. This was confirmed by fluorescein probe allowing detailed evaluation of corneal epithelialization and exclusion of uneven and chaotic epithelialization with poorly fixed and mobile epithelium. Thus, uncomplicated postoperative course after transepithelial PARK was recorded in almost all cases By day 5-7 postoperatively the anterior eye sector was calm, the cornea was smooth, bright and transparent. Only in some cases biomicroscopy revealed slightly thickened epithelial layer of the cornea with mild subep ithelial opalescence; its intensification accompanied by appearance of whitish inclusions in the cornea are considered to be the first signs of development of subep ithelial fibroplasia [2]. We analyzed clinical course of transepithelial PARK at different terms of postoperative period and recorded no visible signs of fibroplasia(degree 0) in 136(54.4%) eyes from the first days after surgery and during the whole follow-up to 3 years. As a rule, SE in these cases did not exceed 8.5 D. In 92(36.8%)eyes 8-14 days postpperatively and irrespective of the value of initial refraction, reversible form of subepithelial fibroplasia was recorded. Its symptoms intensified during 1-3 months postoperatively and gradually disappeared by 6-12 months postoperatvely. From our viewpoint, timely and correct topical corticosteroid and resolving therapy affected the rate of fibroplasia regression that in agreement with data of other authors[10, 11] Partially reversible type of fibroplasia was recorded in 22(8.8%) eyes. Average SE was higher tnan 10.0 D ln these eyes. Due to medication (corticosteroid and resolving therapy) only delicate and spotty opacities of 0.5-1 degree remained at tne periphery and in tne center of ablation zone by 6-l2 months after PARK which almost did not affect postoperative visual acuity and did not cause its decrease as compared to that with glasses preoperatively.
We found irreversible subepithelial fibroplasia with signs of pronounced fibrosis in the corneal stroma and accompanied by significant decrease of refractive effect in none of the cases. This data correlate with results of clinical observations at the Center of Laser Surgery of Eye Microsurgery Complex analyzing 40,000 PRK and indicating that this type of fibroplasia is rather rare and its occurrence is not more than 1.4% of cases. The degree of manifestation of postoperative corneal opacities in ablation zone is presented in Table.
Thus, 6-12 months after PARK and during the further follow-up until 3 years corneal opacities caused by subePithelial fibroplasia were recorded in only 8.8% of cases. Transepithelial access in PARK technique using “Profil-500″ allows significant degrease of degree and duration of corneal syndrome and decreases 1.5-2 times the period of complete epithelialization of the cornea that, in turn, sharply reduces the degree of subepithelial fibroplasia in postoperative period and significantly increases the percentage of high and stable refractive results.
