Correcting peripheral refractive errors with ophthalmic lenses

2000 ◽  
Author(s):  
George Smith ◽  
David A. Atchison
Keyword(s):  
Refractive Errors

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.

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.

Outdoor Activities and Myopia on Junior High School Student in Rural Area of Bali

2018 ◽  
Vol 44 (1) ◽  
pp. 30
Author(s):  
Ni Made Ari Suryathi ◽  
I Putu Budhiastra ◽  
Ariesanti Tri Handayani
Keyword(s):  
High School ◽  
High School Students ◽  
Rural Area ◽  
Junior High School ◽  
Junior High ◽  
Positive Impact ◽  
Natural Habitat ◽  
Capital City ◽  
Refractive Errors ◽  
Outdoor Activities

Introduction and Aims. Refractive errors such as miopia, hyperopia and astigmatism in teenagers are common in Asian country nowadays. Gadget usage also influence the prevalence and incidence of refractive errors specially for miopia and astigmatism. Outdoor activities have positive impact to prevent miopia. The aim of this study is to report the role of outdoor activities as unique school program that could prevent refractive errors in Junior High School in rural area of Bali Method. This is analytic descriptive study with cross sectional approach of 231 Pekutatan II Junior High School students taken in December 2016. This school located in rural area; 35,3 km from Jembarana and 60,5 km from Denpasar, the capital city of Bali. The area of the school is about 1500 m2, where 70% of the land are still vacant to natural habitat and this school had their own garden area that being organized by the students themselves after school hours. This school do not have computer extra curriculum as well. Result. From 231 students there were only 14 students that have refractive errors consist of 5 boys and 9 girls, mostly aged 15 years. Six students (2%) were diagnosed as myopia and 8 students (3.4%) were diagnosed as compound astigmatism myopia. The length of gadget usage in this school were 1.66 hours and outdoor activities time were 4.78 hours per day. The hereditary factors of refractive errors were noted in 12 students (5 %). Outdoor activities associated with refractive errors in this study (p = 0.03). While time using gadget does not have an association with the refractive errors (p = 0.38). Conclusion. Rural area where the outdoor activities are still common have protective effect to prevalence of refractive errors in teenager.

PREVALENCE OF REFRACTIVE ERRORS IN RURAL AND URBAN SCHOOL CHILDREN – A CROSS SECTIONAL STUDY.

2017 ◽  
Vol 5 (3) ◽  
pp. 554-557
Author(s):  
Dr.R.Priyadarsini M.D ◽  
◽  
Dr.K.Kanchana M.D ◽  
Dr.P.Shanmugapriya M.D ◽  
Dr.Malaiarasi M.D.
Keyword(s):  
School Children ◽  
Urban School ◽  
Cross Sectional Study ◽  
Refractive Errors ◽  
Sectional Study ◽  
Cross Sectional ◽  
Rural And Urban

Ocular higher-order aberrations in patients with various refractive errors

2017 ◽  
Vol 21 (3) ◽  
pp. 177-183
Author(s):  
Eman Morad ◽  
Mohamed Abd_ Elateef ◽  
Mohammad Mousa ◽  
Ismael Abdelatif
Keyword(s):  
Higher Order ◽  
Refractive Errors ◽  
Higher Order Aberrations

scholarly journals Epidemiological Findings of Refractive Errors and Amblyopia among the Schoolchildren in Hatta Region of the United Arab Emirates

2021 ◽  
pp. 1-7
Author(s):  
Salam Chettian Kandi ◽  
Hayat Ahmad Khan
Keyword(s):  
Visual Acuity ◽  
Visual Field ◽  
United Arab Emirates ◽  
Refractive Error ◽  
Screening Program ◽  
Low Vision ◽  
Refractive Errors ◽  
Vision Screening ◽  
Screening Programs ◽  
School Based

<b><i>Introduction:</i></b> Uncorrected refractive errors and amblyopia pose a major problem affecting schoolchildren. We had previously observed that many schoolchildren in the Hatta region presented to the ophthalmology clinic with uncorrected refractive errors and amblyopia, which led us to undertake this research. As per the WHO, the term “visual impairment” can be “low vision” or “blindness.” Based on the presenting vision, “low vision” is defined for children who have vision of &#x3c;6/18 to 3/60 or having visual field loss to &#x3c;20° in the better-seeing eye. Children defined to have “blindness” have presenting vision of &#x3c;3/60 or corresponding visual field of &#x3c;10°. <b><i>Purpose:</i></b> To estimate the magnitude of uncorrected refractive errors and amblyopia among the schoolchildren aged 6–19 years and to assess the efficacy of school-based refractive error screening programs in the Hatta region of the United Arab Emirates. <b><i>Methods:</i></b> An epidemiological, cross-sectional, descriptive study was conducted on the entire student population studying in the government schools of the region. Those who failed the Snellen visual acuity chart test and those who were wearing spectacles were evaluated comprehensively by the researcher in the Department of Ophthalmology of the Hatta Hospital. Data were entered in the Refractive Error Study in School Children (RESC) eye examination form recommended by the WHO, and were later transferred to Excel sheets and analyzed by SPSS. <b><i>Results:</i></b> 1,591 students were screened and evaluated from the end of 2016 to mid-2017. About 21.37% (<i>n</i> = 340) had impaired vision with 20.9% (<i>n</i> = 333) refractive errors, of which 58% were uncorrected. Among the refractive error group, 19% (64 subjects) had amblyopia (4% of total students). The incidence of low vision was 9.5% and blindness was 0.38%. Low vision was found to be 9.5% and blindness 0.38%, taking in to account presenting visual acuity rather than best-corrected visual acuity for defining low vision and blindness. <b><i>Conclusion:</i></b> A significant number of students were detected to have uncorrected refractive errors among the vision impaired group (59%, <i>n</i> = 197) despite a school-based vision screening program in place. Seventy-eight percent of the amblyopia cases (<i>n</i> = 50) were found to be in the 11–19 years age group. Noncompliance with optical corrections was the reason for the high number of cases. A rigorous vision screening program and refractive services, complimented with awareness among parents and teachers, are recommended.

Effect of defocus combined with rotation on the optical performance of trifocal toric IOLs

2021 ◽  
pp. 112067212110021
Author(s):  
Javier Ruiz-Alcocer ◽  
Irene Martínez-Alberquilla ◽  
Amalia Lorente-Velázquez ◽  
José F Alfonso ◽  
David Madrid-Costa
Keyword(s):  
Visual Quality ◽  
Optical Quality ◽  
Refractive Errors ◽  
Focal Points ◽  
Modulation Transfer ◽  
Optical Analysis ◽  
Toric Intraocular Lens ◽  
Toric Iols ◽  
Reference Situation

Purpose: To objectively analyze the optical quality of the FineVision Toric intraocular lens (IOL) with two cylinder powers when different combinations of rotations and residual refractive errors are induced. Methods: This study assessed the FineVision Toric IOL with two different cylinder powers: 1.5 and 3.0 diopters (D). Three different rotation positions were considered: centered, 5° and 10° rotated. An optical bench (PMTF) was used for optical analysis. The optical quality of the IOLs was calculated by the modulation transfer function (MTF) at five different focal points (0.0, 0.25, 0.50, 0.75, and 1.00 D). Results: The MTF averaged value of the reference situation was 38.58 and 37.74 for 1.5 and 3.0 D of cylinder, respectively. For the 1.5 D cylinder, the combination of 5° of rotation with a defocus of 0.25, 0.50, 0.75, and 1.0 D induced a decrease on the MTF of 12.39, 19.94, 23.43, 24.23 units, respectively. When induced rotation was 10°, the MTF decrease was 17.26, 23.40, 24.33, 24.48 units, respectively. For the 3.0 D cylinder, the combination of 5° with 0.25, 0.50, 0.75, and 1.0 D of defocus, induced a decrease on the MTF of 12.51, 18.97, 22.36, 22.48 units, respectively. When induced rotation was 10°, the MTF decrease was: 18.42, 21.57, 23.08, and 23.61 units, respectively. Conclusion: For both FineVision Toric IOLs there is a certain optical tolerance to rotations up to 5° or residual refractive errors up to 0.25 D. Situations over these limits and their combination would affect the visual quality of patients implanted with these trifocal toric IOLs.

scholarly journals An evaluation of the NR-1000F Auto Refractometer in high refractive errors.

1987 ◽  
Vol 71 (9) ◽  
pp. 682-684 ◽  
Author(s):  
B. K. Nayak ◽  
S. Ghose ◽  
J. P. Singh
Keyword(s):  
Refractive Errors

scholarly journals Toxic anterior segment syndrome following phakic posterior chamber IOL: a rarity

2018 ◽  
Vol 11 (1) ◽  
pp. bcr-2018-225806 ◽  
Author(s):  
Archita Singh ◽  
Noopur Gupta ◽  
Vinod Kumar ◽  
Radhika Tandon
Keyword(s):  
Intensive Therapy ◽  
Anterior Segment ◽  
Secondary Glaucoma ◽  
Sterile Inflammation ◽  
Posterior Chamber ◽  
Refractive Errors ◽  
Corneal Decompensation ◽  
Toxic Anterior Segment Syndrome ◽  
Idiosyncratic Response ◽  
Posterior Chamber Iol

Implantable collamer lenses (ICL) have gained popularity for correction of myopia where kerato-refractive procedures are not indicated as in cases of high myopic refractive errors. Toxic anterior segment syndrome (TASS) is a very uncommonly reported postoperative complication following ICL implantation. A young patient developed severe corneal oedema and anterior segment inflammation on the first day after ICL implantation. Analysing retrospectively, possible idiosyncratic response to intracameral pilocarpine was considered as a cause for TASS. Prompt and intensive therapy with oral and topical potent steroids was visually rewarding. TASS, though a sterile inflammation can have catastrophic sequelae such as corneal decompensation and secondary glaucoma. Hence, timely identification and management is important.

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