Intrastromal corneal ring segments: how successful is the surgical treatment of keratoconus?

This review evaluates the outcomes of intrastromal corneal ring segment (ICRS) implantation for the treatment of keratoconus considering a new grading system based on the preoperative visual impairment of the patient. Additionally, a five-year follow-up analysis of patients with stable and progressive keratoconus is performed in order to assess the long term stability of the surgical procedure. Corrected distance visual acuity decreased statistically significantly in patients with mild keratoconus (P < 0.01) but statistically significantly increased in all other grades (P < 0.05). The improvement in visual acuity and the decrease of keratometric and aberrometric values were stable throughout a long period of time in patients with stable keratoconus. In patients with progressive form keratoconus, a significant improvement was found immediately after the procedure, however clinically relevant regression greater than 3 D was observed at the end of the follow up period

The importance of parameter choice in modelling dynamics of the eye lens

The lens provides refractive power to the eye and is capable of altering ocular focus in response to visual demand. This capacity diminishes with age. Current biomedical technologies, which seek to design an implant lens capable of replicating the function of the biological lens, are unable as yet to provide such an implant with the requisite optical quality or ability to change the focussing power of the eye. This is because the mechanism of altering focus, termed accommodation, is not fully understood and seemingly conflicting theories require experimental support which is difficult to obtain from the living eye. This investigation presents finite element models of the eye lens based on data from human lenses aged 16 and 35 years that consider the influence of various modelling parameters, including material properties, a wide range of angles of force application and capsular thickness. Results from axisymmetric models show that the anterior and posterior zonules may have a greater impact on shape change than the equatorial zonule and that choice of capsular thickness values can influence the results from modelled simulations

Lens stem cells may reside outside the lens capsule: an hypothesis

In this paper, we consider the ocular lens in the context of contemporary developments in biological ideas. We attempt to reconcile lens biology with stem cell concepts and a dearth of lens tumors

Vitrectomy and internal limiting membrane peeling for macular folds secondary to hypotony in myopes

Jeroni Nadal,1&ndash;3 Elisa Carreras,2,3 Maria Isabel Canut,1&ndash;3 Rafael I Barraquer1&ndash;3 1Centro de Oftalmologia Barraquer, 2Universitat Aut&ograve;noma de Barcelona, 3Instituto Barraquer, Barcelona, Spain Background: Hypotony maculopathy (HM) changes may persist, and visual acuity remains poor, despite normalization of intraocular pressure (IOP). The aim of this study was to evaluate the visual and anatomical results of pars plana vitrectomy (PPV), internal limiting membrane (ILM) peeling, and 20% SF6 gas tamponade in five myopic patients with HM.Methods: This retrospective interventional study was conducted at the Barraquer Center of Ophthalmology, a tertiary care center in Barcelona, Spain, and included five eyes from five consecutive patients (aged 55.4&plusmn;13.1 years) with HM caused by different conditions.&nbsp;All the patients were treated with 23-gauge PPV, ILM peeling, and 20% SF6 gas tamponade. Preoperative and postoperative evaluation was performed using anterior and posterior biomicroscopy and best corrected visual acuity (BCVA) by logMAR charts.Results: Before surgery, median spherical equivalent was -13.1 (range -7, -19) diopters of myopia.&nbsp;Preoperatively, four cases presented IOP &lt;6.5 mmHg for 3 (range 2&ndash;8) weeks. In three of these four cases, IOP &gt;6.5 mmHg was achieved over 16 (range 16&ndash;28) weeks, without resolution of HM; increased IOP was not achieved in the remaining case treated 2 weeks after diagnosis of HM. One case presented IOP &gt;6.5 mmHg with HM for 28 weeks before surgery.&nbsp;Preoperative BCVA was 0.7 (range 0.26&ndash;2.3) logMAR, and 0.6 (range 0.3&ndash;0.7) logMAR and 0.5 (range 0.2&ndash;1) logMAR, respectively, at 4 and 12 months after surgery.&nbsp;There was no statistically significant difference between preoperative and postoperative BCVA. Hyperpigmentation lines in the macular area were observed in three cases with hypotony. These lines progressed after surgery despite resolution of the retinal folds in the three cases, and BCVA decreased in parallel in two of these cases.Conclusion: PPV with ILM peeling followed by gas tamponade is a good alternative for the treatment of HM in myopic patients. However, persistent choroidal folds may compromise BCVA. We therefore recommend initiating treatment as early as possible. Keywords: hypotony maculopathy, retinal pigment epithelial hyperpigmentation, macular folds, retinal pigment epithelium, vitrectom

Equatorial wrinkles in the human lens capsule

Equatorial wrinkles, or crenations, have been previously observed around the equator in coronal images of the human ocular lens. However, wrinkles are typically not apparent when the lens is viewed from saggital directions. In the current paper, the existence and geometry of these wrinkles is shown to be consistent with a mechanical model of the isolated lens, in which the capsule is held in a state of residual tension by a spatially uniform internal pressure. The occurrence of equatorial wrinkles is therefore seen to be a mechanical consequence of the spheroidal shape of the lens capsule and an excess intralenticular pressure. New observations are made, on post mortem lenses, on the geometric arrangement of these equatorial wrinkles. These observations indicate a well-defined pattern in which wrinkles exists along meridional lines in the equatorial regions of the lens. A preliminary 'puncture test' is used to demonstrate that the residual stresses within the capsule in the equatorial region of the lens are broadly consistent with the proposed mechanical model of the lens capsule. It is suggested that the presence of equatorial wrinkles may have an influence on the mechanical performance of the capsule during the accommodation process

Equatorial wrinkles in the human lens capsule

Equatorial wrinkles, or crenations, have been previously observed around the equator in coronal images of the human ocular lens. However, wrinkles are typically not apparent when the lens is viewed from saggital directions. In the current paper, the existence and geometry of these wrinkles is shown to be consistent with a mechanical model of the isolated lens, in which the capsule is held in a state of residual tension by a spatially uniform internal pressure. The occurrence of equatorial wrinkles is therefore seen to be a mechanical consequence of the spheroidal shape of the lens capsule and an excess intralenticular pressure. New observations are made, on post mortem lenses, on the geometric arrangement of these equatorial wrinkles. These observations indicate a well-defined pattern in which wrinkles exists along meridional lines in the equatorial regions of the lens. A preliminary 'puncture test' is used to demonstrate that the residual stresses within the capsule in the equatorial region of the lens are broadly consistent with the proposed mechanical model of the lens capsule. It is suggested that the presence of equatorial wrinkles may have an influence on the mechanical performance of the capsule during the accommodation process

Autologous platelet concentrate in surgery for macular detachment associated with congenital optic disc pit

Jeroni Nadal,1,2 Marta S Figueroa,3 Elisa Carreras,2,4 Patricia Pujol,2,4 Maria Isabel Canut,2,4,5 Rafael Ignacio Barraquer2,6 1Vitreoretinal Surgery Department at Centro de Oftalmolog&iacute;a Barraquer, 2Universitat aut&oacute;noma de Barcelona, Barcelona, 3Vissum Madrid, Madrid, 4Instituto Barraquer, 5Glaucoma Department at Centro de Oftalmolog&iacute;a Barraquer, 6Cornea and Cataract Surgery Department at&nbsp;Centro de Oftalmolog&iacute;a Barraquer, Barcelona, Spain Purpose: To evaluate the anatomical and functional results obtained with pars plana vitrectomy (PPV) plus autologous platelet concentrate (APC) as a treatment for macular detachment associated with optic disc pit (ODP).Methods: We performed a prospective interventional study of 19 eyes of 19 consecutive patients with posterior macular detachment due to ODP. All patients underwent PPV, posterior hyaloid peeling, fluid&ndash;air exchange, injection of 0.05 mL of APC over the ODP and 15% perfluoropropane (C3F8) endotamponade. Postoperative measures included face-up positioning for 2 hours and then avoidance of the face-up position during the ensuing 10 days. All patients underwent complete ophthalmologic examination and optical coherence tomography preoperatively at 1&nbsp;month, 3 months, 6 months, 9 months, and 12 months postoperatively and then annually. Outcome measures were best corrected visual acuity (BCVA) by logMAR, improvement of quality of vision, macular attachment, and resolution of intraretinal schisis-like separation.Results: Preoperatively, the median BCVA was 0.70 (range: 0.30&ndash;1.70) and all patients showed improved visual acuity after surgery; BCVA was 0.22 (range: 0.07&ndash;0.52) at 12 months follow-up. All patients showed complete reabsorption of intraretinal fluid (median time: 3.5&nbsp;months [range: 2&ndash;8 months]) and macular attachment at the end of follow-up (median: 60&nbsp;months [range: 12&ndash;144&nbsp;months]), with stable or improved visual acuity. No reoperations were needed and no major adverse events were recorded.Conclusion: For macular detachment associated with ODP, the combination of PPV, posterior hyaloid peeling, APC, and C3F8 tamponade is a highly effective alternative technique with stable anatomical and functional results. Keywords: macular detachment, optic disc pit, maculopathy, retinoschisis, pars plana vitrectomy, autologous platelet concentrat

Deformations and ruptures in human lenses with cortical cataract subjected to ex vivo simulated accommodation

Purpose: Human cortical opacities are most commonly accompanied by changes in lens fiber structure in the equatorial region at the lens nucleus–cortex interface. Cortex and nucleus have different elastic properties, which change with age. We therefore subjected ex vivo lenses to simulated accommodation and studied the internal deformations to better understand the mechanism of cortical cataract formation. Methods: Nine human donor lenses (33–88 years old) were tested using a bespoke radial stretching device for anterior eye segments. Seven of the lenses exhibited cortical cataracts. The other two lenses, without cataract, were used as controls. Frontal and cross-sectional images of the lens obtained during stretching facilitated measurements on equatorial lens diameter and central lens thickness in the stretched and unstretched states. Results: Stretching caused the lens equatorial diameter to increase in all cases. Conversely, the lens central thickness showed no systematic variation during stretching. For four of the lenses with cortical cataract, ruptures were observed during stretching at the nucleus–cortex boundary adjacent to the cortical cataracts. Ruptures were not observed in the control lenses or in the three other lenses with cortical cataract. Conclusions: Internal ruptures can occur in aged ex vivo lenses subjected to simulated disaccommodation. These ruptures occur at the nucleus–cortex interface; at this location, a significant stiffness discontinuity is expected to develop with age. It is hypothesized that ruptures occur in in vivo lenses during accommodation—or attempted accommodation

Anterior lens capsule strains during simulated accommodation in porcine eyes

Experimental protocols have been developed to measure the spatial variation of the mechanical strains induced in the lens capsule during ex vivo lens stretching. The paper describes the application of these protocols to porcine lenses. The deformations and mechanical strains developed in the anterior capsule during each experiment were determined using full field digital image correlation techniques, by means of a speckle pattern applied to the lens surface. Several speckling techniques and illumination methods were assessed before a suitable combination was found. Additional data on the cross section shape of the anterior lens surface were obtained by Scheimpflug photography, to provide a means of correcting for lens curvature effects in the determination of the strains developed in the plane of the capsule. The capsule strains in porcine lenses exhibit non-linear behaviour, and hysteresis during loading and unloading. Peripheral regions experience higher magnitude strains than regions near the lens pole. The paper demonstrates the successful application of a procedure to make direct measurements of capsule strains simultaneously with ex vivo radial lens stretching. This experimental technique is applicable to future investigations on the mechanical characteristics of human lenses