BackgroundThe accommodation has considerable interactions with the pupil response, vergence response and binocularity. The transformation of visual reception processing and the changes of the binocular cooperation during the presbyopia development are still poorly studied. So, the regularities of visual system violation in the presbyopia formation need to be characterized. This study aims to reveal the transformation of visual reception processing and to determine the role of disturbances in binocular interactions in presbyopia formation.MethodsThis study included 60 people with emmetropic refraction, uncorrected distance visual acuity 1.0 or higher (decimal scale), normal color perception, without concomitant ophthalmopathology. The first group consisted of 30 people (from 18 to 27 years old) without presbyopia, the second cohort comprised 30 patients (from 45 to 55 years old) with presbyopia. The eyeball anatomy and optics were evaluated using ultrasound biomicroscopy, aberrometry, and pupillometry. The functional state of the visual system was investigated under monocular and binocular conditions. The registration of the disparate fusional reflex limits was performed by the original technic using a diploptic device which facilitated investigation of the binocular interaction under natural conditions without the accommodation response, but with the different vergence load. The disparate fusional reflex was analyzed using the proximal and distal fusion borders, and the convergence and divergence fusion borders. The calculation of the area of binocularity field was performed in cm2.ResultsThe presbyopia formation is characterized by a change in an intraocular anatomy, optics, visual processing, and binocularity. The processes of binocular interaction inhibition make a significant contribution to the misalignment of the visual perception. The modification of the proximal, distal and convergence fusion borders was determined. It was revealed that 87% of the presbyopic patients had binocularity shortage, whereas the reduction of binocularity field area in extreme grade was seen in 6% of cases.ConclusionsThe presbyopia formation is accompanied by a significant reorganization of the visual system activity and by the creation of the new visual processing interactions. These data may be useful in presbyopia surgery.
Taking into account the constant increase in patients with age-related cataracts after radial keratotomy, a careful analysis of both the optical and anatomical properties of the cornea with the examination of the posterior surface is of particular importance.Aim. To analyze the optical properties of the posterior surface of the cornea in patients after anterior radial keratotomy. Materials and methods. An examination of 24 patients (48 eyes) with age-related cataracts of varying degrees of density, myopia and the presence of a previous anterior radial keratotomy or radial-tangential keratotomy in history. The average age of patients was 59.5 years (from 47 to 68), there were 19 women and 5 men.Results. The radius of curvature of the anterior surface in patients after anterior radial keratotomy was 9.45 ± 0.91 mm on average along the meridians, which is significantly more in comparison with these indices in control patients – 7.70 ± 0.19 mm (p = 0.0001). The ratio of the radii of the posterior cornea curvature to the anterior radius on average along the meridians in patients after anterior radial keratotomy was 1.07 ± 0.70, and in control patients – 1.20 ± 0.02 (p = 0.0001). The keratometric index in patients after anterior radial keratotomy was 1.3538 ± 0.0239, and in the control group – 1.3372 ± 0.0003 (p = 0.23).Conclusion. In patients after anterior radial keratotomy, keratometry of the posterior surface of the cornea is significantly higher than in the control. The ratio of the radius of curvature of the posterior cornea to the radius of curvature of the anterior cornea varies significantly after anterior radial keratotomy, which is due to a more pronounced flattening of the posterior cornea. The standard keratometric index (1.3375) is invalid for patients after anterior radial keratotomy and must be calculated individually for each patient when deciding on the operative treatment of cataracts.
Purpose. To assess the long-term results of presbyopia correction in patients with primary cataract depending on type of implantable IOLs.Material and methods. A profound study of visual functions and assessment of visual quality of 90patients (mean age 63.3±1.2years) with partial cataracts and presbyopia. The studies were conducted before surgery and in late post-operative period after bilateral cataract phacoemulsification with implantation of different models IOLs that provide a high visual acuity in distance and at close range. Results. Bilateral implantation of monofocal IOLs for monovision principle leads to a significant increase in far visual acuity of leading the eye and near visual acuity of slave eye. However, patients need long-term adaptation to artificial anisometropia. As a result of bilateral implantation of accommodating IOLs a significant improvement in visual acuity at distance and near occurs. Surgical treatment provides best visual quality of patients up to 6 months after surgery. In period from 12 to 24months after surgery, there was a decrease of visual functions as a result of fibrosis of capsular bag. The correction of presbyopia by creating a multifocal optical system as a result of bilateral multifocal refractive IOL implantation leads to a stable improvement of visual acuity at far and close distance. But thus the contrast sensitivity deteriorates, especially in low- and high-frequency ranges.Conclusion. Intraocular correction of presbyopia is a highly effective method of treatment, allowing obtaining high visual acuity in distance and at close range. However, the results depend on chosen strategy of intraocular correction.
Aim. To identify patterns of structural and functional interrelationship in the eye in presbyopia formation. Methods. 60 patients with emmetropia without eye diseases in two age groups: from 18 to 30 years old and from 45 to 60 years old were examined. In addition to the standard ophthalmic examinations the following methods were used: assessment the pupil size in different lighting conditions, examination of the anterior and middle segment of the eye by means of ultrasound biomicroscopy and using a rotating Scheimpflug camera («Pentacam»). Results. Patients with presbyopia showed lens enlargement with simultaneous shortening of anterior portion of Zinn ligament, reduction of anterior chamber depth and volume, decrease of an adjunction angle between the iris and the cornea, ciliary body thickness reduction, and the increased distance between trabeculae and the crown of the ciliary body. The most pronounced decrease of the thickness of the ciliary body, length of the Zinn ligament and the increase of distance between trabeculae and ciliary processes were noted in the horizontal plane with a maximum change in the internal segment. The spatial deformation of the posterior chamber and changes of the anterior chamber angle were more pronounced in the lower and outer quadrants. Pearson’s correlation analysis revealed the vanishing of a significant number of correlations, characteristic for the physiologically properly formed eye with a proportionate refraction and the appearance of new relationships, directed to preserve the normal physiology of intraocular fluid, and stability of visual image receiving. Conclusion. Presbyopia development is characterized by a set of structural and functional changes, the spatial transformation of the eyeball that must be considered when performing surgical interventions in patients with presbyopia.
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