Neurological Implications
John William Yee in The Neurological Treatment for Nearsightedness and Related Vision Problems, 2019
There are neurological relationships between the different muscles of an eye that became nearsighted. If it is within the myopic model, the relationships can be verified by ortho C. When an ortho C lens reverses the crystalline lens’ bulged shape by relaxing the oblique muscles, it exemplifies the first myopic relationship. When it also reverses the eyeball’s elongated shape by relaxing the oblique muscles, it exemplifies the second myopic relationship. When it synchronizes the crystalline lens to the change in the shape of the eyeball, it demonstrates the third myopic relationship. And when it synchronizes the right and left eye, it demonstrates the fourth myopic relationship. Neurology also plays a vital role in how the normal eye functions. There is a developmental relationship between the crystalline lens and the eyeball during childhood development and adult postdevelopment in the normal or emmetropic eye. Developmental factors determine the shape of the crystalline lens in relation to the eyeball, and postdevelopmental factors determine the shape of the eyeball in relation to the lens. When the emmetropic eye brings day-to-day objects into focus, it activates a different neurological message. The eyeball does not change its shape to bring about near and distant focusing. The crystalline lens carries out that task. With sudden changes in focus from near to far and vice versa, only the ciliary muscle is flexible enough to facilitate the immediate changes. When immediate focusing is required, the lens acts independently. It is evident in mild myopia when the crystalline lens assumes a bulged shape first before the sclera starts to elongate to alleviate the stress incurred by the ciliary muscle. On my website, however, I asked the following question: if the existing model for accommodation only involves the crystalline lens, then how did the eye become elongated? You need another model to explain it. The following are proposed theories of the myopic model.
Contrast adaptation
Pablo Artal in Handbook of Visual Optics, 2017
It is interesting that the amplitudes of contrast adaptation vary among the different refractive groups. “Late onset myopes” (myopia developed during school years in early adolescence) show the largest amplitudes (i.e., Cufflin et al. 2007). It is unclear whether the larger amplitude of adaptation is the result of more defocused retinal images in myopia or whether it was there already before myopia developed but generated more tolerance to defocus and could therefore have stimulated its development. It is well established that poor retinal image contrast triggers the development of deprivation myopia in both animal models and humans although it has not been resolved until today why positive defocus has a strong inhibitory effect on axial eye growth (i.e., Wallman and Winawer 2004). For these reasons, Wallman suggested already in 1996 that the level of contrast adaptation (which changes with retinal image defocus) might represent a retinal error signal for the control of axial eye growth and myopia although it can only provide a unidirectional growth stimulus (Wallman and Schaeffel, 1996). The problem of emmetropization is that defocus of the retinal image varies rapidly over time depending on viewing distance and the level of accommodation. Therefore, momentary “measurements” of defocus cannot provide useful information for the control of axial eye growth. An integrator with long time constant is needed. A candidate would be the level of contrast adaptation that changes only slowly with the level of image sharpness. It can be observed in the chicken model of myopia that defocus imposed by spectacle lenses increases CS, by shifting the level of contrast adaptation (Diether et al. 2001; Figure 21.17). Drugs that inhibit myopia development after intravitreal injection (i.e., atropine) also increase CS (Diether and Schaeffel 1999), suggesting a retinal mechanism. A possible biochemical mediator might be dopamine. Its release from dopaminergic amacrine cells is stimulated by atropine (Schwahn et al. 2000) and reduced when image contrast is poor (Feldkaemper et al. 1999). It is known for long that myopia development goes along with low retinal dopamine levels (Stone et al. 1989) and that intravitreal application of dopamine agonists can inhibit myopia development perhaps because they compensate for the drop in dopamine release.
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
For example optic and auditory information is decomposed into elements by the RETINA and COCHLEA respectively. See also: spatial frequency channels; hearing theoriesfourth ventriclesee ventriclesfoveaThe central region of the RETINA is the area with the highest density of PHOTORECEPTORS. In humans the region exclusively contains CONES and lacks the RODS associated with scotopic vision (vision at low light levels). The region is marked by a yellowish pigment that lends the fovea the alternative name of MACULA LUTEA. The cone-rich region contains a pit or 'fovea' which is about 5 in diameter, with a central region (the fovea centralis or FOVEOLA) subtending 1 approximately, containing the smallest diameter photoreceptors in the eye. Behaviourally, the fovea is the area with the highest visual ACUITY and is the region of the retina that an observer turns towards an object in order to inspect it. In normal vision it is the part of the eye that is used for fixation or foveation (see FIXATION POINT). DAVID W.HEELEYfoveola (fovea centralis)see fixation point; foveafragile X syndromeA chromosome abnormality in which the X chromosome is, literally, fragile, and can break into two separate parts (see CHROMOSOME ABNORMALITIES; CHROMO SOMES). After DOWN SYNDROME, it is the most frequent chromosome abnormality. It is caused by a single defective gene, possessed by as many as one in 260 women. Estimates suggest that some 1 in 2000 boys and 1 in 4000 girls are affected by it. In both male and female cases, fragile X tends to produce individuals with the following typical features: large underdeveloped ears, long thin faces, broad noses; males also tend to have enlarged testicles. Females may show no outward features of fragile X but their children may still be at risk of inheriting the disorder.
The Relation of Neutrophil to Lymphocyte Ratio and Platelet to Lymphocyte Ratio with High Axial Myopia
Published in Ocular Immunology and Inflammation, 2020
Erel Icel, Turgay Ucak, Yücel Karakurt, Hayati Yilmaz, Nurdan Gamze Tasli, Adem Turk
Purpose: To investigate the relation between high axial myopia and neutrophil to lymphocyte ratio (NLR) and platelet to lymphocyte ratio (PLR) values. Methods: Seventy-nine cases were enrolled, 50 myopic and 29 emmetropic. All participants were assigned into three groups: Group I (high myopia with no retinal involvement), Group II (high myopia with retinal involvement) and Group III (control). NLR and PLR values calculated from blood tests were compared among the groups. Results: Mean NLR levels were 2.23 ± 0.78 in Group I, 2.36 ± 1.06 in Group II, and 1.57 ± 0.33 in Group III. Mean PLR levels were 114.62 ± 23.21 in Group I, 145.16 ± 52.36 in Group II, and 91.42 ± 18.73 in Group III. NLR and PLR values in the high myopia groups were significantly higher than in the control group. Conclusion: NLR and PLR values in cases with high axial myopia were higher than in the emmetropic group. Higher inflammation in the degenerative myopic group in particular may be related to pathological chorioretinal changes.
Does transient increase in axial length during accommodation attenuate with age?
Published in Clinical and Experimental Optometry, 2017
Deborah S Laughton, Amy L Sheppard, Edward A H Mallen, Scott A Read, Leon N Davies
BackgroundThe aim was to profile transient accommodative axial length changes from early adulthood to advanced presbyopia and to determine whether any differences exist between the responses of myopic and emmetropic individuals. MethodsOcular biometry was measured by the LenStar biometer (Haag‐Streit, Switzerland) in response to zero, 3.00 and 4.50 D accommodative stimuli in 35 emmetropes and 37 myopes, aged 18 to 60 years. All results were corrected to reduce errors arising from the increase in crystalline lens thickness with accommodation. Accommodative responses were measured sequentially by the WAM 5500 Auto Ref/Keratometer (Grand Seiko, Hiroshima, Japan). ResultsAxial length increased significantly with accommodation (p
The Prevalence of Open-Angle Glaucoma by Age in Myopia: The Korea National Health and Nutrition Examination Survey
Published in Current Eye Research, 2017
Seong Hee Shim, Kyung Rim Sung, Joon Mo Kim, Hyun Tae Kim, Jinho Jeong, Chan Yun Kim, Mi Yeon Lee, Ki Ho Park
Purpose: To investigate the prevalence of open-angle glaucoma (OAG) in myopia by age. Materials and methods: A cross-sectional study using a stratified, multistage, probability cluster survey. Participants in the Korean National Health and Nutrition Examination Survey between 2010 and 2011 were included. A standardized protocol was used to interview every participant and perform comprehensive ophthalmic examinations. Glaucoma was diagnosed according to the International Society of Geographical and Epidemiological Ophthalmology (ISGEO) criteria. Results: After adjusting for age and sex, there was a positive correlation between OAG prevalence and increasing myopic refractive error except in participants with hyperopia. Younger participants with higher myopic refractive error had higher OAG prevalence than older participants with lower myopic refractive error. Participants with high myopia (OR 3.90, 95% confidence interval (CI) 2.30–6.59) had significantly greater age- and sex-adjusted odd ratios (ORs) than did those with emmetropia who were younger than 60 years. Conclusions: These data suggest that OAG develops earlier in participants with high myopia than in others. There was a high prevalence of OAG in participants with high myopia, even in those 19–29 years of age. Therefore, OAG screening should be performed earlier in participants with high myopia than is suggested by traditional guidelines.