Прогнозирование рефракционного сдвига при выполнении фототерапевтической кератэктомии на примере пациента с субэпителиальной муциновой дистрофией роговицы (клинический случай)

Abstract

Purpose. To present the treatment results of a patient with subepithelial mucinous corneal dystrophy by phototherapeutic keratectomy (PTK) using the excimer-laser system WaveLight EX500 (Alcon, USA) taking into account the induced myopic refractive shift. Material and methods. Patient S., 67 years old, with subepithelial mucinous corneal dystrophy and compound hyperopic astigmatism of both eyes. To determine the possibility of surgical treatment, in addition to the general ophthalmological examination, there were performed: optical coherence tomography (OCT) of the cornea to evaluate the total corneal thickness and the opacity depth; Corneal topography to evaluate total corneal refractive power and maximal anterior refractive power. FTK calculations were made basing on OCT data considering clinical refraction. The follow-up period was 3 months. Results. As a result of treatment, the corneal transparency of both eyes was restored. The ablation of the left eye corneal stroma with the standard PTK protocol to a 90-micron depth caused an increase in the patient’s refractive power by 3.87 D in spherical equivalent, which led to excessive myopic refraction. When performing PTK on the right eye, decrease of the ablation depth to 80-micron, as well as the two-stage formation of the anterior corneal profile with the formation of its wider «base» and a smaller optical zone diameter led to less refractive power increase of 2.62 D in spherical equivalent, which caused an emmetropic refraction in this case. Conclusion. The presented clinical case shows that various protocols for PTK implementation in patients with superficial corneal opacities can make it possible to not only achieve corneal transparency, but also to control the refractive shift and to define the final clinical refraction. Keywords: corneal dystrophy, phototherapeutic keratectomy (PTK), refractive surgery.