Journal ArticleDOI
Improvements on Littmann's method of determining the size of retinal features by fundus photography.
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TLDR
Three new methods of determining Littmann's factor q become available: simply reducing the axial length by a constant 1 · 82 mm; constructing a personalized schematic eye, given additional data; and ray tracing through this eye to extend calculations to peripheral retinal areas.Abstract:
Littmann's formula relating the size of a retinal feature to its measured image size on a telecentric fundus camera film is widely used. It requires only the corneal radius, ametropia, and Littmann's factor q obtained from nomograms or tables. These procedures are here computerized for practitioners' convenience. Basic optical principles are discussed, showing q to be a constant fraction of the theoretical ocular dimension k′, the distance from the eye's second principal point to the retina. If the eye's axial length is known, three new methods of determining q become available: (a) simply reducing the axial length by a constant 1 · 82 mm; (b) constructing a personalized schematic eye, given additional data; (c) ray tracing through this eye to extend calculations to peripheral retinal areas. Results of all these evaluations for 12 subjects of known ocular dimensions are presented for comparison. Method (a), the simplest, is arguably the most reliable. It shows good agreement with Littmann's supplementary procedure when the eye's axial length is known.read more
Citations
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Early detection of cone photoreceptor cell loss in retinitis pigmentosa using adaptive optics scanning laser ophthalmoscopy.
Shunji Nakatake,Yusuke Murakami,Jun Funatsu,Yoshito Koyanagi,Masato Akiyama,Yukihide Momozawa,Tatsuro Ishibashi,Koh Hei Sonoda,Yasuhiro Ikeda +8 more
TL;DR: In RP, cone photoreceptor cell loss occurred in the parafoveal region with a preserved EZ/IZ or visual sensitivity and AO-SLO may be a useful modality to detect early changes of cone photoresceptor cells in RP patients.
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Cone Dystrophy in Patient with Homozygous RP1L1 Mutation
Sachiko Kikuchi,Shuhei Kameya,Kiyoko Gocho,Said El Shamieh,Said El Shamieh,Said El Shamieh,Keiichiro Akeo,Yuko Sugawara,Kunihiko Yamaki,Christina Zeitz,Christina Zeitz,Christina Zeitz,Isabelle Audo,Hiroshi Takahashi +13 more
TL;DR: The findings indicate that a homozygous p.S1210P exchange in the RP1L1 gene can cause cone dystrophy.
Journal ArticleDOI
Optic disc-fovea distance and myopia progression in school children: the Beijing Children Eye Study.
TL;DR: To assess changes in the optic disc–fovea distance (DFD) with progressing myopia in school children, a large number of children are screened for myopia and the distance between their eyes is measured.
DissertationDOI
Learning and teaching in English : a case study of higher education in Libya
TL;DR: This thesis sets out the multiple and contradictory challenges that all parties experience in the learning and use of English as a tool of instruction inside Libyan universities and shows then how the challenges evident in the teaching and learning of English are carried into a professional field.
Journal ArticleDOI
High-Resolution Imaging by Adaptive Optics Scanning Laser Ophthalmoscopy Reveals Two Morphologically Distinct Types of Retinal Hard Exudates
Muneo Yamaguchi,Shintaro Nakao,Yoshihiro Kaizu,Yoshiyuki Kobayashi,Takahito Nakama,Mitsuru Arima,Shigeo Yoshida,Yuji Oshima,Atsunobu Takeda,Yasuhiro Ikeda,Shizuo Mukai,Tatsuro Ishibashi,Koh Hei Sonoda +12 more
TL;DR: High resolution imaging using AO-SLO enables morphological classification of retinal hard exudates into two types, which could not be distinguished either on fundus examination or by spectral domain optical coherence tomography (SD-OCT).
References
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Journal ArticleDOI
Determination of the real size of an object on the fundus of the living eye
TL;DR: A method is described which allows the real diameter of an object on the fundus to be determined by means of a system of curves which are the result of trigonometrical calculations and which give an approximate value.
Book
Clinical Visual Optics
TL;DR: The eye's optical system visual acuity and contrast sensitivity spherical ametropia astigmatism subjective refraction accommodation and near vision ocular motility and binocularVision convergence anomalies of binocular vision - heterophoria and heterotropia stereopsis and the stereoscope.
Journal ArticleDOI
Determining the true size of an object on the fundus of the living eye
TL;DR: The result was represented by curves which enable factors used in calculating the true diameter to be determined, but instead of the curves a quadratic equation is used to produce the same factors.
Journal ArticleDOI
A method of determining the equivalent powers of the eye and its crystalline lens without resort to phakometry
TL;DR: If the positions of the principal points of the crystalline lens are conjectured, its equivalent power and that of the eye can be calculated as described from ocular dioptrics.