Corneal stromal demarcation line after collagen cross-linking in corneal ectatic diseases: a review of the literature

Collagen cross-linking (CXL) is a relatively new conservative approach for progressive corneal ectasia, which is able to strengthen corneal tissue reforming new covalent bonds. Subjective and objective results following this method seem to be promising. In recent years, newer CXL protocols have been developed to perform more effective and less invasive procedures. The increasing diffusion of CXL in the corneal ectatic disease has increased the need to have actual indices regarding the efficacy of the treatment. Evaluation of demarcation line (DL), a transition zone between the cross-linked anterior corneal stroma and the untreated posterior corneal stroma, is considered a measurement of the depth of CXL treatment into the stroma. Some evidence in the literature emphasize that DL could be a measure of effectiveness of the CXL. On the contrary, some authors believe that the "the deeper, the better" principle is rather a simplistic approach for interpreting the clinical importance of the corneal stromal DL

Correlation between retinal function and microstructural foveal changes in intermediate age related macular degeneration

Purpose: To assess foveal microstructural changes influencing retinal sensitivity (RS) and fixation stability using microperimeter MP-1 in intermediate age-related macular degeneration (AMD). Methods: In this cross-sectional study, 22 eyes of 22 patients (mean age: 75 ± 9.02 years) with intermediate AMD were enrolled. Retinal sensitivity and bivariate contour ellipse area (BCEA) were obtained by microperimetry MP-1 (Humphrey 10-2 68-loci grid) under mesopic conditions. Drusen type, drusenoid pigment epithelial detachment, hyperreflective foci (HF), integrity of external limiting membrane (ELM), inner ellipsoid zone (ISel), RPE/Bruch’s mem- brane complex (RPE/B) and subfoveal choroidal thickness were analyzed in the foveal region and compared with RS and BCEA. Spearman’s rank correlation coefficient was used to evaluate the relationship between variables. Logistic regression analysis was also used to assess morphological predictor influencing RS or BCEA. Results: RS was strongly and inversely related with the presence of HF (r = −0.66, P = 0.001), integrity of ELM (r = −0.70, P < 0.001), ellipsoid zone (r = −0.45, P = 0.03). Instead, BCEA is positively related to the ellipsoid zone integrity (r = 0.45, P = 0.03). Logistic regression analysis confirmed that disruption of ISel influenced fixation stability (ExpB: 9.69, P = 0.04) but not RS. Instead, the presence of HF and disruption of ELM predicted RS reduction (ExpB: 0.55, P = 0.02 and ExpB: 0.29, P = 0.04, respectively). Conclusions: The integrity of ELM and the presence of HF are both predictors of RS. The ELM status may be con- sidered a new biomarker of retinal function together with HF. Instead, the integrity of ISel band seems to be a more selective predictor of BCEA than RS

Endothelin-1 Role in Human Eye: A Review

Endothelin is a potent vasoactive peptide occurring in three isotypes, ET-1, ET-2, and ET-3. Through its two main receptors, endothelin A and endothelin B, it is responsible for a variety of physiological functions, primarily blood flow control. Recent evidence from both human and animal models shows involvement of endothelin in diabetes, retinal circulation, and optic neuropathies. Increased circulating levels of endothelin-1 (ET-1) have been found in patients with diabetes, and a positive correlation between plasma ET-1 levels and microangiopathy in patients with type-2 diabetes has been demonstrated. In addition to its direct vasoconstrictor effects, enhanced levels of ET-1 may contribute to endothelial dysfunction through inhibitory effects on nitric oxide (NO) production. Experimental studies have shown that chronic ET-1 administration to the optic nerve immediately behind the globe causes neuronal damage, activation of astrocytes, the major glial cell in the anterior optic nerve, and upregulation of endothelin B receptors. This paper outlines the ubiquitous role of endothelin and its potential involvement in ophthalmology

Effect of corneal light scatter on vision: a review of the literature

The cornea is the transparent connective tissue window at the front of the eye. The physiological role of the cornea is to conduct external light into the eye, focus it, together with the lens, onto the retina, and to provide rigidity to the entire eyeball. Therefore, good vision requires maintenance of the transparency and proper refractive shape of the cornea. The surface structures irregularities can be associated with wavefront aberrations and scattering errors. Light scattering in the human cornea causes a reduction of visual quality. In fact, the cornea must be transparent and maintain a smooth and stable curvature since it contributes to the major part of the focusing power of the eye. In most cases, a simple examination of visual acuity cannot demonstrate the reduction of visual quality secondary light scattering. In fact, clinical techniques for examining the human cornea in vivo have greatly expanded over the last few decades. The measurement of corneal back scattering qualifies the degree of corneal transparency. The measurement of corneal forward-scattering quantifies the amount of visual impairment that is produced by the alteration of transparency. The aim of this study was to review scattering in the human cornea and methods of measuring it

Pathologic Myopia: Complications and Visual Rehabilitation

High myopia, defined as refractive error of at least −6.00D or an axial length of 26.5 mm or more, can induce many modifications in eye’s anatomy that can lead to complications. When high myopia is able to decrease best corrected visual acuity (BCVA) due to its complications, it is called pathologic myopia. Pathologic myopia is one of the major causes of blindness, and it represents a serious issue, since incidence of myopia and high myopia is constantly rising. For educational purposes, in this chapter, complications of pathologic myopia will be divided into anterior (when structures external to the globe or anterior to the ora serrata are involved, such as motility disturbances and cataract) and posterior (when structures posterior to the ora serrata are involved, such as lacquer cracks, chorioretinal atrophy, Fuchs maculopathy, myopic choroidal neovascularization, and retinal detachment). Many treatments are available for pathologic myopia complications depending on their type, such as vascular endothelial growth factor (anti-VEGF) injections and surgery. We will focus on visual rehabilitation interventions, such as visual biofeedback and visual aids that in many cases are the only chance that the ophthalmologist has in order to help patients suffering from pathologic myopia to use at their maximum their residual vision

Clinical pathogenesis of macular holes in patients affected by retinitis pigmentosa

Background. To define the main clinical mechanisms involved in the pathogenesis of macular holes (MH) in patients affected by Retinitis Pigmentosa (RP). Methods. 236 RP subjects were enrolled in this study and ophthalmologically examined according to a standard FIARP (Italian Federation of the RP Associations) protocol. The prevalence of posterior vitreous detachment (PVD) as well as all types of RP-related macular abnormalities - especially vitreoretinal interface alterations (VRIA), cystoid macular edema (CME), "bull's eye maculopathy" (BEM) and MH - was reported; statistical analyses and correlations were assessed by means of Student t test and Pearson X2. Results. VRIA and CME were observed in 26.15% and 9.45% of the cases respectively and resulted significantly associated with MH, since they were constantly present in 22 of the 25 eyes affected by MH (88%) (X2 = 50.4; p < 0.01). In particular, in 9 of these cases (40.9%) MH was correlated to both CME and VRIA, while in 11 (50%) and 2 (9.1%) eyes CME or, VRIA were present separately. A normal biomicroscopic macular appearance, PVD and BEM were found in 26.81%, 6.6% and 21.54% of the cases respectively. Conclusions. Further studies involving a larger number of patients are required to complete these preliminary results. However, the present investigation seem to confirm the data already reported in the literature, i.e. that pathogenesis of MH in RP is strictly correlated to the presence of VRIA, cellophane maculopathy and cystic foveal degeneration with CME

Microperimetric evaluation in patients with adult-onset foveomacular vitelliform dystrophy

INTRODUCTION: To compare mean best-corrected visual acuity (BCVA), retinal sensitivity (RS), and bivariate contour ellipse area (BCEA) in patients with adult-onset foveomacular vitelliform dystrophy (AOFVD) and healthy subjects (HSs), reporting also functional disease-related changes in the different stages of the AOFVD disease. MATERIALS AND METHODS: In this observational cross-sectional study, a total of 19 patients (30 eyes; 12 female and 7 male) with AOFVD were enrolled, and 30 patients (30 eyes; 16 female and 14 male) were recruited as age-matched control group (74.36 ± 9.17 years vs. 71.83 ± 6.99 years respectively, P= 0.11). All patients underwent a complete ophthalmologic examination, fundus autofluorescence and fluorescein angiography, spectral-domain optical coherence tomography and microperimetry (MP)-1 analysis. The data collection included mean BCVA, mean RS measured by means of MP-1, BCEA, and central retinal thickness. RESULTS: All the functional parameters (BCVA, RS, and BCEA) were significantly worse in AOFVD group than HS. Subgroup analysis showed that the most significant functional changes, quantified by mean BCVA, RS, and BCEA, were in the atrophic stage (P = 0.03, P= 0.01, and P= 0.001, respectively). All the functional parameters were well correlated in the different stages. CONCLUSIONS: This study further confirms the good visual prognosis in the AOFVD eyes. Fixation stability measurement using BCEA demonstrates good evaluation of visual performance integrating traditional functional parameters. It may also serve for further rehabilitative purposes in atrophic eyes

Deflazacort treatment of cystoid macular edema in patients affected by Retinitis Pigmentosa: a pilot study

Background. To investigate the efficacy of a long-term treatment with Deflazacort (DFZ), a third generation synthetic glucocorticoid, in patients affected by Retinitis Pigmentosa (RP) complicated by Cystoid Macular Edema (CME). Methods. A randomized group of 10 RP subjects were selected for this pilot study and treated with DFZ for one year according to a standard protocol. Far and near Best Corrected Visual Acuity (BCVA), fluorescein angiography (Heidelberg Retina Angiograph) and computerized perimetry (Humphrey Visual Field Analyzer) were statistically assessed. Results. Near visual acuities, fluorescein angiographic findings and perimetric data improved significantly (p < 0.01) while far BCVA varied only slightly (p < 0.05). No ocular or systemic side effects were recorded. Conclusions. Further case-control studies, also involving a larger number of patients, are required to confirm these preliminary results. However, the present investigation seem to suggest that DFZ could be effective in reducing fluorescein angiographic findings and improving perimetric data and near visual acuities in RP patients, even though the pathogenesis of CME remains poorly understood