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

Diagnostic Aspects and Retinal Imaging in Ocular Toxocariasis: A Case Report from Italy

Toxocara canis is a nematode parasite, commonly found in dogs. This roundworm parasite can invade the eye, causing visual impairment. Toxocara should be considered as a possible causative agent of posterior and diffuse uveitis, and it could be considered in the differential diagnosis of retinoblastoma. Ocular manifestations vary from severe endophthalmitis to silent incidental findings on a routine examination. We report a case of ocular toxocariasis in a 24-year-old Asiatic female that presented to us complaining of visual impairment. Fundoscopic examination revealed a posterior pole granuloma and exudative retinal detachment along with exudates. Presentation, clinical findings, morphological changes, and treatment are discussed. The enzyme-linked immunosorbent assay serology for Toxocara canis was performed, demonstrating the positivity for IgG and IgE. Treatment with the antihelminthic albendazole was initiated. Fluorescein angiography (FA; HRA 2, Heidelberg engineering) and optical coherence tomography (OCT; Spectralis, Heidelberg tomography) were performed, and results have been reported

Ocular Effects of Niacin: A Review of the Literature

Cystoid macular edema is a condition that involves the macula, caused by an accumulation of extracellular fluid in the macular region with secondary formation of multiple cystic spaces. This condition is provoked by a variety of pathological conditions such as intraocular inflammation, central or branch retinal vein occlusion, diabetic retinopathy and most commonly following cataract extraction, hereditary retinal dystrophies, and topical or systemic assumption of drugs. Niacin is a vitamin preparation usually used for the treatment of lipid disorders. The treatment with niacin, alone or in combination with other lipid-lowering agents, significantly reduces total mortality and coronary events and slows down the progression of and induces the regression of coronary atherosclerosis. Several cases of niacin-induced cystoid macular edema have been reported with different dosages

Fixation improvement through biofeedback rehabilitation in Stargardt disease

Stargardt disease is the most common hereditary macular degeneration in juveniles. It is characterized by macular dystrophy associated with loss of central vision in the first or second decade of life, a "beaten-metal" appearance in the fovea or parafoveal region, yellowish flecks around the macula or in posterior area of the retina, progressive atrophy of the bilateral foveal retinal pigment epithelium, and the "dark choroid" sign on fundus fluorescein angiography in most cases. We report a case of Stargardt disease in a 26-year-old Caucasian female submitted to rehabilitative training with microperimetry MP-1 to find a new preferred retinal locus (PRL) and to train her to better her quality of life. Best corrected visual acuity, mean retinal sensitivity, fixation, bivariate contour ellipse area, and speed reading were evaluated before and after the training and results were discussed

Corneal collagen cross-linking followed by phacoemulsification with IOL implantation for progressive keratoconus associated with high myopia and cataract

PURPOSE: To evaluate the visual and topographic outcomes of a two-stage approach treatment for progressive keratoconus (KC) associated with high myopia and cataract. METHODS: Two patients, a 50-year-old man and a 54-year-old woman with high myopia (spherical equivalent greater than -10D), cataract, and progressive KC with poor spectacle-corrected vision and contact lens intolerance underwent a 2-stage approach treatment: first corneal collagen cross-linking (CXL) followed after at least 6 months by phacoemulsification with intraocular lens (IOL) implantation in both eyes. RESULTS: In both patients after a mean follow-up of 3.5 years (from 2 to 4) uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and corneal topography pattern improved in both eyes, and the patients were satisfied with the visual improvement and happy with tolerable glasses. CONCLUSION: This 2-stage approach reported no complications and was effective in improving visual acuity and corneal patterns in patients with high myopia, cataract, and progressive KC

Diagnostic Aspects and Retinal Imaging in Ocular Toxocariasis:

Copyright © 2012 Onelia Verallo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Toxocara canis is a nematode parasite, commonly found in dogs. This roundworm parasite can invade the eye, causing visual impairment. Toxocara should be considered as a possible causative agent of posterior and diffuse uveitis, and it could be considered in the differential diagnosis of retinoblastoma. Ocular manifestations vary from severe endophthalmitis to silent incidental findings on a routine examination. We report a case of ocular toxocariasis in a 24-year-old Asiatic female that presented to us complaining of visual impairment. Fundoscopic examination revealed a posterior pole granuloma and exudative retinal detachment along with exudates. Presentation, clinical findings, morphological changes, and treatment are discussed. The enzyme-linked immunosorbent assay serology for Toxocara canis was performed, demonstrating the positivity for IgG and IgE. Treatment with the antihelminthic albendazole was initiated. Fluorescein angiography (FA; HRA 2, Heidelberg engineering) and optical coherence tomography (OCT; Spectralis, Heidelberg tomography) were performed, and results have been reported. 1

Long term results of no-alcohol laser epithelial keratomileusis and photorefractive keratectomy for myopia

<b>RESULTS:</b> Twenty-one eyes and 22 eyes completed follow-up of 60mo in LASEK and PRK group respectively. Manifest refraction at 60mo follow-up was -0.01 and 0.26 in LASEK and PRK group respectively. In the LASEK group mean UDVA and mean CDVA after 60mo were 20/22 and 20/20 respectively (<i>P</i>&gt;0.01). In the PRK group mean UDVA and mean CDVA at 60mo follow-up were 20/20 and 20/20 after 60mo (<i>P</i>&gt;0.01). The efficacy indexes were 0.87 and 0.95, and the safety indexes were 1.25 and 1.4 respectively for LASEK group and PRK group.<b>CONCLUSION:</b>Both standard PRK and no-alcohol LASEK offer safe and effective correction of low-moderate myopia in the long term without any statistically significant difference between the two groups

Cystoid Macular Edema Induced by Low Doses of Nicotinic Acid

Cystoid macular edema (CME) is a condition that involves the macula, causing painless vision loss. In this paper, we report a case of niacin-induced bilateral cystoid macular edema (CME) in a middle-age woman taking low dose of niacin (18 mg of nicotinic acid). Optical coherence tomography (OCT) showed retinal thickening and cystoid spaces in both eyes, whereas fluorescein angiography (FA; HRA 2, Heidelberg Engineering) revealed the absence of fluorescein leakage also in later phases. Four weeks after discontinuation of therapy there were a complete disappearance of macular edema at funduscopic examination and an improvement of visual acuity in both eyes. Furthermore OCT showed a normal retinal profile in both eyes. In our opinion considering the wide availability of niacin, medical monitoring and periodical examination should be considered during niacin administration. To our knowledge, this is the first report in the literature that described the very low-dose niacin-induced bilateral niacin maculopathy

New trends in visual rehabilitation with MP-1 microperimeter biofeedback: optic neural dysfunction

The aim of this study was to evaluate the efficacy of visual rehabilitation with MP-1 microperimeter biofeedback in advanced optic neural dysfunction due to glaucoma, and to precisely characterize fixation stability and location in affected patients. Ten patients (18 eyes) with advanced glaucoma were submitted to a rehabilitation protocol that consisted of: a 25-item questionnaire (National Eye Institute Visual Functioning Que stionnaire); measurement of visual acuity; a reading speed test; microperimetry with fixation study, retinal sensitivity and the bivariate contour ellipse area (BCEA). The rehabilitation program consisted of 10 training sessions of 10 minutes per eye performed over a period of one week and was repeated at four months, eight months, and one year. Statistical analysis was performed using the Student’s t-test and Spearman correlation; p values less than 0.05 were considered statistically significant. In 13 eyes fixation changed from unstable to relatively unstable while its location changed from predominantly eccentric to predominantly central. In five eyes, fixation changed from relatively unstable to stable with a change of location from poor central fixation to predominantly central fixation. Mean retinal sensitivity changed from 7.43±8.28 dB to 8.33±9.04 dB (p0.05); reading speed improved from a mean value of 31.4±4.3 words/minute to 55.6±3.2 words/minute at the end of the training (p<0.05). The BCEA changed from 0.94±0.39 deg2 to 0.86±0.46 deg2 (p=0.76). Rehabilitation with MP-1 biofeedback in patients with advanced glaucoma is a useful means of improving these patients’ fixation stability, reading speed and quality of life

Corneal collagen cross-linking for keratectasia after Laser in situ keratomileusis: a review of the literature

The aim was to review the published literature on corneal collagen cross-linking. The emphasis was on the seminal publications, systemic reviews, meta-analyses and randomized controlled trials. Where such an evidence did not exist, selective large series cohort studies, case controlled studies and case series with follow-up preferably greater than 12 months were included. Riboflavin/Ultraviolet A (UVA) corneal collagen cross-linking appears to be the first treatment modality to halt the progression of keratoconus and other corneal ectatic disorders with improvement in visual, keratometric and topographic parameters documented by most investigators. Its precise mechanism of action at a molecular level is as yet not fully determined. Follow-up is limited to 4–6 years at present but suggests continued stability and improvement in corneal shape with time. Most published data are with epithelium-off techniques. Epithelium-on studies suggest some efficacy but less than with the epithelium-off procedures and long-term data are not currently available. The use of Riboflavin/UVA CXL for the management of infectious and non-infectious keratitis appears very promising. Its use in the management of bullous keratopathy is equivocal. Investigation of other methodologies for CXL are under investigation