Types of refractive errors and methods for their diagnosis

2020 ◽  
pp. 30-36
Author(s):  
Olga Lemzyakova
Keyword(s):  
Optical System ◽  
Contact Lenses ◽  
Vision Impairment ◽  
Refractive Errors ◽  
Vision Correction ◽  
Light Rays ◽  
Different Types ◽  
Almost All ◽  
Degrees Of Severity ◽  
The Brain

Refraction of the eye means its ability to bend (refract) light in its own optical system. In a normal state, which is called emmetropia, light rays passing through the optical system of the eye focus on the retina, from where the impulse is transmitted to the visual cortex of the brain and is analyzed there. A person sees equally well both in the distance and near in this situation. However, very often, refractive errors develop as a result of various types of influences. Myopia, or short-sightedness, occurs when the light rays are focused in front of the retina as a result of passing through the optical system of the eye. In this case, a person will clearly distinguish close objects and have difficulties in seeing distant objects. On the opposite side is development of farsightedness (hypermetropia), in which the focusing of light rays occurs behind the retina — such a person sees distant objects clearly, but outlines of closer objects are out of focus. Near vision impairment in old age is a natural process called presbyopia, it develops due to the lens thickening. Both myopia and hypermetropia can have different degrees of severity. The variant, when different refractive errors are observed in different eyes, is called anisometropia. In the same case, if different types of refraction are observed in the same eye, it is astigmatism, and most often it is a congenital pathology. Almost all of the above mentioned refractive errors require correction with spectacles or use of contact lenses. Recently, people are increasingly resorting to the methods of surgical vision correction.

scholarly journals OKVision® Onefit™ Mini-Scleral Lenses Fitting Guide

The Eye ◽  
2019 ◽  
Vol 127 (2019-3) ◽  
pp. 47-52
Author(s):  
Elena Belousova
Keyword(s):  
Visual Acuity ◽  
Medical Practice ◽  
Optical System ◽  
Direct Contact ◽  
Oxygen Permeability ◽  
Contact Lenses ◽  
Polymer Materials ◽  
Corneal Surface ◽  
Visual Functions ◽  
Vision Correction

Corneal topography has been widely used in medical practice over recent years and it has helped to detect keratectasias of various genesis more often and in the earlier stages. The emergence of the new polymer materials with high oxygen permeability made it possible to wear scleral contact lenses safely, that also resulted in their popularization. Scleral gas permeable lenses are an effective method of vision correction not only for various ectasias, but also for ametropia, presbyopia and other refractive pathologies. Scleral contact lenses do not directly touch the cornea and the limbus area, whereas tear firm under the lens physically smoothes out all of the existing defects and irregularities of the corneal surface, thus creating a ”cornea-tear-lens“ unified optical system. As a result, visual acuity increases significantly. In addition, scleral lenses ensure excellent comfort starting from the first minutes of wearing due to a larger diameter, no direct contact with the cornea and relatively low mobility. Scleral lenses ensure high visual functions and comfort owing to their specific self-supporting design, which is rested on the sclera. Selection and fitting of scleral contact lenses is simple and can be mastered by any ophthalmologist

Use of orthokeratology contact lenses in the treatment of progressive myopia

2020 ◽  
pp. 18-22
Author(s):  
Mariya Olenich
Keyword(s):  
Visual Acuity ◽  
Children And Adolescents ◽  
Optical System ◽  
Contact Lenses ◽  
Spherical Aberration ◽  
Soft Contact ◽  
Soft Contact Lenses ◽  
Vision Correction ◽  
Progressive Myopia ◽  
Biomechanical Changes

Orthokeratology is a method of non-surgical correction of refraction, which is based on the principle of biomechanical changes in the curvature of the cornea under the influence of «reverse geometry». This method was developed more than 50 years ago, however, it became widely used only in the early 2000s. The basis of this method is the use of special orthokeratology lenses that patients wear during the night. Peculiarity of these lenses is the ability to change curvature of the cornea, resulting in a flattening of its central part and thickening of the paracentral and peripheral sections, which leads to the formation of positive spherical aberration of the optical system. Such changes in the cornea resulting from partial desquamation of keratocytes and changes in their shape during 7–8 hours of influence during the night, lead to the normalization of refraction, which persists for the next 24 hours. Most often this method of vision correction is used in children and adolescents, since it allows not only to optimize visual acuity for a certain period of time, but also to stop the progression of myopia. Another indication for the correction of vision using orthokeratology lenses includes active sports and situations that exclude the possibility of wearing glasses or soft contact lenses.

scholarly journals Cancer Trends in Iraq 2000–2016

2021 ◽  
Vol 36 (1) ◽  
pp. e219-e219
Author(s):  
Ashraf MA. Hussain ◽  
Riyadh K. Lafta
Keyword(s):  
Control Measure ◽  
Incidence Rates ◽  
Disease Rate ◽  
Cancer Occurrence ◽  
Different Types ◽  
Cancer Trends ◽  
Almost All ◽  
Two Peaks ◽  
The Impact ◽  
The Brain

Objectives: Precise and quantitative assessment of the trend of cancer burden enables policymakers and health managers to prioritize diseases and allocate resources better. This infers what caused a decrease or increase in the rate of cancer occurrence, and if it denotes timing of implementation of a control measure, it presents the impact on the disease rate. This study’s objective was to evaluate trends in child and adult cancer in Iraq from 2000 onwards. Methods: We used the registries of the Iraqi Ministry of Health that were gathered from all governorates from 2000–2016. Data were presented as incidence rates to depict the trends of different types of cancers distributed by age, gender, and governorates. Results: Breast cancer witnessed a significant increase with predominance in females. Lung cancer rate increased significantly from 4.08 to 5.60/100 000 (p = 0.038), affecting males more than females. The brain cancer trend showed a bimodal pattern (two peaks in 2004 and 2011) with no significant trend change (p = 0.788). Both genders were similarly affected. The trend of stomach and colorectal cancer showed an accelerated increase after 2007. Conclusions: Almost all cancers (particularly lung and gastrointestinal) showed constantly raising trends, especially after 2007. Only cervical and laryngeal cancer had a decreasing trend. Most cancers were predominant in males.

scholarly journals Relative Proportion Of Different Types Of Refractive Errors In Subjects Seeking Laser Vision Correction

2018 ◽  
Vol 12 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Talal A. Althomali
Keyword(s):  
Saudi Arabia ◽  
Relative Proportion ◽  
Refractive Errors ◽  
Spherical Equivalent ◽  
Vision Correction ◽  
Manifest Refraction ◽  
Different Types ◽  
Laser Vision ◽  
Refractive Correction ◽  
Work Up

Background:Refractive errors are a form of optical defect affecting more than 2.3 billion people worldwide. As refractive errors are a major contributor of mild to moderate vision impairment, assessment of their relative proportion would be helpful in the strategic planning of health programs.Purpose:To determine the pattern of the relative proportion of types of refractive errors among the adult candidates seeking laser assisted refractive correction in a private clinic setting in Saudi Arabia.Methods:The clinical charts of 687 patients (1374 eyes) with mean age 27.6 ± 7.5 years who desired laser vision correction and underwent a pre-LASIK work-up were reviewed retrospectively. Refractive errors were classified as myopia, hyperopia and astigmatism. Manifest refraction spherical equivalent (MRSE) was applied to define refractive errors.Outcome Measures:Distribution percentage of different types of refractive errors; myopia, hyperopia and astigmatism.Results:The mean spherical equivalent for 1374 eyes was -3.11 ± 2.88 D. Of the total 1374 eyes, 91.8% (n = 1262) eyes had myopia, 4.7% (n = 65) eyes had hyperopia and 3.4% (n = 47) had emmetropia with astigmatism. Distribution percentage of astigmatism (cylinder error of ≥ 0.50 D) was 78.5% (1078/1374 eyes); of which % 69.1% (994/1374) had low to moderate astigmatism and 9.4% (129/1374) had high astigmatism.Conclusion and Relevance:Of the adult candidates seeking laser refractive correction in a private setting in Saudi Arabia, myopia represented greatest burden with more than 90% myopic eyes, compared to hyperopia in nearly 5% eyes. Astigmatism was present in more than 78% eyes.

scholarly journals Contact Lenses in Pediatric Ophthalmological Practice

2020 ◽  
Vol 17 (1) ◽  
pp. 32-41
Author(s):  
E. Yu. Markova ◽  
E. A. Perfilyeva
Keyword(s):  
Traditional Method ◽  
Contact Lenses ◽  
Young Patients ◽  
Stereoscopic Vision ◽  
Psychological Characteristics ◽  
Refractive Errors ◽  
Vision Correction ◽  
Complex Process ◽  
Medical Indications ◽  
Selection Of

Last years, the problem of using contact lenses (CL) in pediatric ophthalmic practice has become more important. It is associated with an increasing need for contact vision correction in children and with the improvement of its capabilities in relation to pediatric ophthalmic practice. Currently, the indication for contact lenses use in children are the same as for the adults (with certain specific and limitations). But there are also a number of specific indications in children’s practice. The article provides an overview of the domestic and foreign literature data (periodicals and monographs) relating to various aspects of the use of contact lenses in pediatric ophthalmic practice. The contact lenses use for medical indications has a number of advantages over another more traditional method of vision correction — glasses. Rational correction of the most common refractive error — myopia with the help of CL helps normalize accommodation, convergence, reduce the risk of complications associated with the myopia’s progression, helps to slow down the processes of eyeball’s elongation by reducing the peripheral defocus, and during the period of functional formation of the visual organ (up to 15 years) helps to form binocular and stereoscopic vision. Uncorrected ametropia (especially high degrees) in childhood leads to maladaptation of visual perception. Rational correction of refractive errors with CL allows children to adapt to environmental conditions better, have higher indicators of health and psychological comfort among peers in comparison with children wearing glasses. The mode of wearing lenses depends on the purpose of correction, age, type of lens and material, tolerance of correction, manipulation skills, and other factors. The ophthalmologist determines the mode of wearing individually in each case. Modern materials and the use of one-day MCL can reduce the risk of complications. Selection of contact lenses for young children is a complex process and requires joint efforts of the ophthalmologist and parents. The examination algorithm for the CL’s selection is identical to the selection of lenses for adult patients, but contains the use of some additional tests aimed at assessing accommodation and binocular vision. In the process of selecting contact lenses for children, the ophthalmologist may face two main problems: the inability to determine the exact parameters of the cornea and manipulative difficulties associated with the anatomical and psychological characteristics of young patients.

Dual stain kit for the microscopic gram classification of ocular infection bacteria

1993 ◽  
Vol 51 ◽  
pp. 248-249
Author(s):  
Jacob S. Hanker ◽  
Dale N. Holdren ◽  
Kenneth L. Cohen ◽  
Beverly L. Giammara
Keyword(s):  
Contact Lenses ◽  
Ocular Infection ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Gram Staining ◽  
Ocular Infections ◽  
Different Types ◽  
Culture Positive ◽  
Increased Susceptibility

Keratitis and conjunctivitis (infections of the cornea or conjunctiva) are ocular infections caused by various bacteria, fungi, viruses or parasites; bacteria, however, are usually prominent. Systemic conditions such as alcoholism, diabetes, debilitating disease, AIDS and immunosuppressive therapy can lead to increased susceptibility but trauma and contact lens use are very important factors. Gram-negative bacteria are most frequently cultured in these situations and Pseudomonas aeruginosa is most usually isolated from culture-positive ulcers of patients using contact lenses. Smears for staining can be obtained with a special swab or spatula and Gram staining frequently guides choice of a therapeutic rinse prior to the report of the culture results upon which specific antibiotic therapy is based. In some cases staining of the direct smear may be diagnostic in situations where the culture will not grow. In these cases different types of stains occasionally assist in guiding therapy.

“Where is Dementia?” A Systematic Literature Review Exploring Neuroanatomical Aspects of Dementia

2017 ◽  
Vol 2 (15) ◽  
pp. 9-23 ◽  
Author(s):  
Chorong Oh ◽  
Leonard LaPointe
Keyword(s):  
English Language ◽  
Signs And Symptoms ◽  
Behavioral Symptoms ◽  
Journal Articles ◽  
People With Dementia ◽  
Different Types ◽  
Precise Diagnosis ◽  
Physical Changes ◽  
The Brain ◽  
Language Literature

Dementia is a condition caused by and associated with separate physical changes in the brain. The signs and symptoms of dementia are very similar across the diverse types, and it is difficult to diagnose the category by behavioral symptoms alone. Diagnostic criteria have relied on a constellation of signs and symptoms, but it is critical to understand the neuroanatomical differences among the dementias for a more precise diagnosis and subsequent management. With this regard, this review aims to explore the neuroanatomical aspects of dementia to better understand the nature of distinctive subtypes, signs, and symptoms. This is a review of English language literature published from 1996 to the present day of peer-reviewed academic and medical journal articles that report on older people with dementia. This review examines typical neuroanatomical aspects of dementia and reinforces the importance of a thorough understanding of the neuroanatomical characteristics of the different types of dementia and the differential diagnosis of them.

The Acute Effect of Alcohol on Various Memory Processes

2010 ◽  
Vol 24 (4) ◽  
pp. 249-252 ◽  
Author(s):  
Márk Molnár ◽  
Roland Boha ◽  
Balázs Czigler ◽  
Zsófia Anna Gaál
Keyword(s):  
Low Dose ◽  
Short Term Memory ◽  
Acute Effect ◽  
Long Term Memory ◽  
Term Memory ◽  
Memory Processes ◽  
Different Types ◽  
The Brain ◽  
Legal Consequences

This review surveys relevant and recent data of the pertinent literature regarding the acute effect of alcohol on various kinds of memory processes with special emphasis on working memory. The characteristics of different types of long-term memory (LTM) and short-term memory (STM) processes are summarized with an attempt to relate these to various structures in the brain. LTM is typically impaired by chronic alcohol intake but according to some data a single dose of ethanol may have long lasting effects if administered at a critically important age. The most commonly seen deleterious acute effect of alcohol to STM appears following large doses of ethanol in conditions of “binge drinking” causing the “blackout” phenomenon. However, with the application of various techniques and well-structured behavioral paradigms it is possible to detect, albeit occasionally, subtle changes of cognitive processes even as a result of a low dose of alcohol. These data may be important for the consideration of legal consequences of low-dose ethanol intake in conditions such as driving, etc.

Clinical manifestations and diagnosis of keratoconus. Treatment of iatrogenic keratoconus

2020 ◽  
pp. 37-42
Author(s):  
Fedor Ermolyuk
Keyword(s):  
Research Methods ◽  
Contact Lenses ◽  
Correct Diagnosis ◽  
Clinical Manifestations ◽  
Refractive Errors ◽  
Dry Eyes ◽  
Advanced Stages ◽  
Dystrophic Disease ◽  
Iatrogenic Origin ◽  
Binocular Diplopia

Keratoconus is a dystrophic disease of the cornea, when it is thinned with the formation of a conus-like protrusion (protrusion of the cornea). This disease belongs to the group of keratectasia, it has a multifactorial nature and occurs in approximately 25 % of all corneal pathologies. The disease can be either primary, which is based on dystrophic changes in the cornea, or secondary, which develops against the background of prenatal keratitis. Keratoconus of iatrogenic origin, which develops as a result of refractive eye microsurgery, has become widespread during the last 20 years. Most often primary keratoconus manifests during puberty, progresses to 30–40 years, after which its development slows down. An early clinical manifestation of this corneal pathology is a progressive decrease in visual acuity, development of double vision (binocular diplopia) with the development of a strong headache against this background. Monocular polyopia — images and symbols with multiple contours — develops subsequently. Severe dry eyes, itching, photophobia appear in advanced stages. Diagnosis of keratoconus in some cases can be a significant difficulty, since the use of conventional research methods only allow to suspect refractive errors in the form of myopia or astigmatism. It is necessary to take into account the impossibility of correcting visual impairment using conventional methods — glasses or contact lenses — to make correct diagnosis. As a rule, diagnosis of keratoconus requires use of expanded spectrum of instrumental research methods.

Ligand and Structure-based Modeling of Passive Diffusion through the Blood-Brain Barrier

2018 ◽  
Vol 25 (9) ◽  
pp. 1073-1089 ◽  
Author(s):  
Santiago Vilar ◽  
Eduardo Sobarzo-Sanchez ◽  
Lourdes Santana ◽  
Eugenio Uriarte
Keyword(s):  
Blood Brain Barrier ◽  
In Silico ◽  
Passive Diffusion ◽  
Brain Barrier ◽  
Barrier Permeability ◽  
Blood Brain Barrier Permeability ◽  
Blood Brain ◽  
Brain Barrier Permeability ◽  
Different Types ◽  
The Brain

Background: Blood-brain barrier transport is an important process to be considered in drug candidates. The blood-brain barrier protects the brain from toxicological agents and, therefore, also establishes a restrictive mechanism for the delivery of drugs into the brain. Although there are different and complex mechanisms implicated in drug transport, in this review we focused on the prediction of passive diffusion through the blood-brain barrier. Methods: We elaborated on ligand-based and structure-based models that have been described to predict the blood-brain barrier permeability. Results: Multiple 2D and 3D QSPR/QSAR models and integrative approaches have been published to establish quantitative and qualitative relationships with the blood-brain barrier permeability. We explained different types of descriptors that correlate with passive diffusion along with data analysis methods. Moreover, we discussed the applicability of other types of molecular structure-based simulations, such as molecular dynamics, and their implications in the prediction of passive diffusion. Challenges and limitations of experimental measurements of permeability and in silico predictive methods were also described. Conclusion: Improvements in the prediction of blood-brain barrier permeability from different types of in silico models are crucial to optimize the process of Central Nervous System drug discovery and development.

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