ABSTRACT
PURPOSE: To study peculiarities of intraocular pressure (IOP) measurement by different methods in patients with changes in corneal biomechanical properties. MATERIAL AND METHODS: The study enrolled 154 patients (290 eyes) divided into 3 groups according to the condition of their corneas in terms of biomechanical properties. Group I consisted of 84 patients (168 eyes) with conditionally 'normal' cornea and corneal thickness ranging from 470 to 660 µm. Group II included 44 patients (70 eyes) with keratokonus. Group III consisted of 26 patients (52 eyes) after LASIK. IOP pressure was measured in each patient by pneumotonometry, Maklakov tonometry, and dynamic bidirectional pneumo-applanation of the cornea. Biomechanical properties were evaluated with dynamic pneumo-impression method. RESULTS: The study revealed that in patients of groups I and III, corneal biomechanics affected indices of corneal compensated IOP and Maklakov's IOP to a lesser extent, as opposed to measurements of Goldman tonometry and pneumotonometry. In group II, Maklakov's tonometry had less IOP measurement inaccuracies in comparison to other evaluated methods due to larger applanation surface. CONCLUSION: Changes in biomechanical properties of the cornea can complicate interpretation of the results of different methods of IOP measurement. Accurate determination of IOP requires consideration of biomechanical properties of the cornea, as well as anamnesis data on past corneal diseases or keratorefractive surgeries.
Subject(s)
Intraocular Pressure , Tonometry, Ocular , Biomechanical Phenomena , Cornea , Humans , ManometryABSTRACT
AIM: To analyze changes in various biometric parameters after vitrectomy. MATERIAL AND METHODS: A total of 50 patients (50 eyes) were followed up. All of them underwent vitrectomy for idiopathic epiretinal fibrosis and macular hole. In addition to the standard ophthalmic examination, we performed a combined ultrasound study and ultrasound biomicroscopy before and after the surgery (at 2-3 weeks and 6 months). Variation statistics was applied to assess the results using the SPSS Statistica 20 software. RESULTS: According to ultrasound biomicroscopy, the following parameters increased: anterior chamber depth, trabecular-ciliary process distance, posterior chamber maximal depth and volume, and fiber length within the zonule of Zinn. In the late postoperative period (6 months after the surgery), there was an increase in lens volume and anterior-posterior ocular axis by the average of 0.15±0.04 mm. Against this background, clinical refraction shifted toward myopia by the average of 0.68±0.05 diopters in the early postoperative period and 1.7±0.15 diopters at 6 months. CONCLUSION: With the help of modern ultrasound examinations we have identified biometric changes in the anterior segment of vitrectomized eyes. We have also established a myopic shift of clinical refraction, which is most likely to be due to the increase in axial eye length and lenticular changes.
Subject(s)
Biometry/methods , Postoperative Complications , Vitrectomy/adverse effects , Vitreoretinopathy, Proliferative/surgery , Adult , Aged , Biomechanical Phenomena , Eye/diagnostic imaging , Eye/pathology , Female , Humans , Male , Middle Aged , Organ Size , Postoperative Complications/diagnosis , Postoperative Complications/physiopathology , Postoperative Complications/prevention & control , Reproducibility of Results , Ultrasonography/methods , Vitrectomy/methodsABSTRACT
The article describes the potential effects of vitrectomy on clinical refraction, refraction of the cornea and its biomechanical parameters, the state of the lens, intraocular pressure, and biometric parameters of the anterior eye segment.
