OCT de segmento intermedio / Intermediate segment OCT

No disponible

Extralenticular and lenticular aspects of accommodation and presbyopia in human versus monkey eyes.

PURPOSE: To determine if the accommodative forward movements of the vitreous zonule and lens equator occur in the human eye, as they do in the rhesus monkey eye; to investigate the connection between the vitreous zonule posterior insertion zone and the posterior lens equator; and to determine which components-muscle apex width, lens thickness, lens equator position, vitreous zonule, circumlental space, and/or other intraocular dimensions, including those stated in the objectives above-are most important in predicting accommodative amplitude and presbyopia. METHODS: Accommodation was induced pharmacologically in 12 visually normal human subjects (ages 19-65 years) and by midbrain electrical stimulation in 11 rhesus monkeys (ages 6-27 years). Ultrasound biomicroscopy imaged the entire ciliary body, anterior and posterior lens surfaces, and the zonule. Relevant distances were measured in the resting and accommodated eyes. Stepwise regression analysis determined which variables were the most important predictors. RESULTS: The human vitreous zonule and lens equator move forward (anteriorly) during accommodation, and their movements decline with age, as in the monkey. Over all ages studied, age could explain accommodative amplitude, but not as well as accommodative lens thickening and resting muscle apex thickness did together. Accommodative change in distances between the vitreous zonule insertion zone and the posterior lens equator or muscle apex were important for predicting accommodative lens thickening. CONCLUSIONS: Our findings quantify the movements of the zonule and ciliary muscle during accommodation, and identify their age-related changes that could impact the optical change that occurs during accommodation and IOL function.

Accommodative movements of the vitreous membrane, choroid, and sclera in young and presbyopic human and nonhuman primate eyes.

PURPOSE: We report, for the first time to our knowledge, dynamic movements of the vitreous membrane and peripheral choroid during accommodation, and age-related changes in the anterior sclera. METHODS: We studied 11 rhesus monkeys (ages 6-27 years) and 12 human subjects (ages 19-65 years). Accommodation was induced pharmacologically in human subjects and by central electrical stimulation in the monkeys. Ultrasound biomicroscopy, endoscopy, and contrast agents were used to image various intraocular structures. RESULTS: In the monkey, the anterior hyaloid membrane bows backward during accommodation in proportion to accommodative amplitude and lens thickening. A cleft exists between the pars plicata region and the anterior hyaloid membrane, and the cleft width increases during accommodation from 0.79 ± 0.01 mm to 1.01 ± 0.02 mm in young eyes (n = 2, P < 0.005), as fluid from the anterior chamber flows around the lens equator toward the cleft. In the older eyes the cleft width was 0.30 ± 0.19 mm, which during accommodation increased to 0.45 ± 0.20 mm (n = 2). During accommodation the ciliary muscle moved forward by approximately 1.0 mm, pulling forward the choroid, retina, vitreous zonule, and the neighboring vitreous interconnected with the vitreous zonule. Among the humans, in the older eyes the scleral contour bowed inward in the region of the limbus, compared to the young eyes. CONCLUSIONS: The monkey anterior hyaloid bends posteriorly during accommodation in proportion to accommodative amplitude and the sclera bows inward with increasing age in both species. Future descriptions of the accommodative mechanism, and approaches to presbyopia therapy, may need to incorporate these findings.

New concepts in accommodation and presbyopia / Novos conceitos em acomodação e presbiopia

The authors conducted a review of classical and conflicting theories of accommodation and presbyopia. They make a critical comparison with the findings of magnetic resonance imaging (MRI) that have been developed in recent decades. Based on these studies, formulates a new approach on the subject, shifting the focus of the discussion of the lens to the posterior pole of the eye.

Os autores revisaram as teorias clássicas e conflitantes sobre acomodação e presbiopia. E as compararam criticamente com os achados de imagem por ressonância magnética (MRI) que têm se desenvolvido nas últimas décadas. Baseado nestes estudos, formulam uma nova abordagem sobre o tema, mudando o foco da discussão do cristalino para o polo posterior do olho.

Anterior ciliary sclerotomy using collagen T-shaped implants for treatment of presbyopia.

We assessed the long-term clinical outcomes and evaluate the safety, efficacy and stability of anterior ciliary sclerotomy with collagen T-shaped implants in 19 patients. The study revealed that anterior ciliary sclerotomy with collagen T-shaped implants for the treatment of presbyopia is a safe procedure, but the effect is temporary and diminishes with time.

[Involutional changes in the human eye accommodative apparatus as evidenced by ultrasound biometry and biomicroscopy].

The paper presents the results of studying involutional changes in the accommodative apparatus of the eye in presbyopia by ultrasound biometry and biomicroscopy. Persons aged 40-70 years who had presbyopia and emmetropic refraction and without concomitant eye disease were examined. In addition to routine studies, all the examinees underwent ultrasound biomicroscopy and ultrasound biometry. The age-related lenticular enlargement was established to be accompanied by a considerable reduction in the orbicular space of the posterior chamber of the eye to the extent of its transformation to a slotted space. The presbyopic patients were found to have a significantly diminished tone in the middle and posterior portions of the lenticular ligamentous apparatus to the extent of its sag, with the altered direction of their passage between the crystalline lenticular equator and the ciliary body crown, i. e. from meridional to radial. The revealed significant age-related topographic and anatomic changes in the orbicular portion of the posterior chamber of eye and in ligamentous tone, which are associated with the involutional increase in the size of the crystalline lens point to the great importance of decreasing the working accommodation distance in the development of presbyopia.

Ultrasound biomicroscopy of the aging rhesus monkey ciliary region.

Ultrasound biomicroscopy of the living rhesus monkey ocular ciliary region was undertaken to identify age-dependent changes that might relate to the progression of presbyopia. Monkeys were anesthetized and pharmacologically cyclopleged, the eyelids were held open with a lid speculum, and sutures were placed beneath the medial and lateral rectus muscles. Ultrasound biomicroscopy imaging of the nasal and temporal quadrants of the eye were performed, and the live images were recorded to videotape. Subsequent image analysis was performed to obtain objective morphometric measurements of the ciliary body region. The ciliary body inner radius of curvature, outer radius of curvature, inner arc length, area, thickness, perimeter, zonular fiber length, and circumlental space were measured. Zonular space was calculated. The circumlental space decreased with increasing age in the temporal quadrant. The other morphologic measurements were not significantly correlated with age or body weight. Most morphologic measurements were significantly different comparing temporal vs. nasal quadrants. Bifurcation of the posterior zonular fibers was frequently observed. Although temporal circumlental space was the only measurement found to change with age, ultrasound biomicroscopy of the living rhesus ciliary region did identify distinct nasal vs. temporal asymmetries, which may reflect anatomical requirements for convergence-associated accommodation.

[Ultrasound biomicroscopy imaging of accommodative configuration changes in the presbyopic ciliary body]. / Ultraschallbiomikroskopische Darstellung der akkommodativen Konfigurationsänderungen des presbyopen Ziliarkörpers.

Direct observation of the position of the ciliary body was possible only in cases of gross anatomic, and probably also functional, abnormalities. Utilizing the 50 MHz ultrasound biomicroscope, we investigated the profile changes of the ciliary body in ten eyes of ten patients, ranging in age from 54 to 86 years while they were ocusing on a target at a distance and afterwards on an object up close. After electronic image processing of ten single video pictures from each accommodative status, a summarized picture for every accommodative status was obtained. In seven of ten cases, during accommodation a remarkable shift of the ciliary body was observed anterior to the iris and in the direction of the lens equatore, while the iridociliary body contact zone became wider in five of the ten eyes. Ultrasound biomicroscopy allows visualization of the dynamics of the accommodative process. As the human ciliary body does not lose its contractility in the senium, the loss of accommodation in presbyopia is mainly caused by age-related changes of the lens and capsula.

Contraction of a perifoveal epiretinal membrane simulating a macular hole.

Four patients observed for a three- to four-year period had a hole in an epiretinal membrane overlying the macula that mimicked a macular hole. In two patients the clinical appearance remained essentially constant. In one, the epiretinal membrane contracted further, reducing the apparent macular hole to a slit and causing the typical appearance of a macular pucker. In the fourth patient, the epiretinal membrane peeled spontaneously causing the apparent hole to disappear. None of the patients had static perimetric findings that suggested a true macular hole. All of the patients had normal or nearly normal visual acuity when first seen. This was maintained except in the patient who suffered further membrane contraction. Fluorescein angiography demonstrated a slight fluorescence in the base of the hole in three of the four patients; however, it was not as pronounced as one sees in true macular holes. Lamellar macular holes characteristically show no fluorescence in the area of the hole.