The Effect of Optical Defocus on the Choroidal Thickness: A Review

The choroid is a heavily vascularized tissue located between the retina and sclera and plays a primary role in ocular metabolism. It has recently been suggested that the choroid has the ability to change its thickness and secretion of growth factors. This may play an important role during visual development by adjusting retinal position during growth to support emmetropisation; however, the mechanism by which changes in choroidal thickness (ChT) occur is unclear. This relationship becomes an interesting topic in the clinical field, although conflicting evidence found that these changes in the choroidal thickness may not be associated with the development of refractive errors. Many reports have investigated the changes in the choroid and related factors that affect the ChT. Thus, this review will summarize the current literature related to choroidal thickness in different refractive error groups, determine the factors that influence the thickness of the choroid, and discuss in detail the relationship between the changes in the ChT and ocular elongation, and therefore, the effect of optical defocus on ChT and the development of the refractive error.

Defocused image restoration method based on micro-nano scale

An image adaptive noise reduction enhancement algorithm based on NSCT is proposed to perform image restoration preprocessing on the defocused image obtained under the microscope. Defocused images acquired under micro-nano scale optical microscopy, usually with inconspicuous details, edges and contours, affect the accuracy of subsequent observation tasks. Due to its multi-scale and multi-directionality, the NSCT transform has superior transform functions and can obtain more textures and edges of images. Combined with the characteristics of micro-nanoscale optical defocus images, the NSCT inverse transform is performed on all sub-bands to reconstruct the image. Finally, the experimental results of the standard 500nm scale grid, conductive probe and triangular probe show that the proposed algorithm has a better image enhancement effect and significantly improves the quality of out-of-focus images.

Genome-wide analysis of retinal transcriptome reveals common genetic network underlying perception of contrast and optical defocus detection

Background Refractive eye development is regulated by optical defocus in a process of emmetropization. Excessive exposure to negative optical defocus often leads to the development of myopia. However, it is still largely unknown how optical defocus is detected by the retina. Methods Here, we used genome-wide RNA-sequencing to conduct analysis of the retinal gene expression network underlying contrast perception and refractive eye development. Results We report that the genetic network subserving contrast perception plays an important role in optical defocus detection and emmetropization. Our results demonstrate an interaction between contrast perception, the retinal circadian clock pathway and the signaling pathway underlying optical defocus detection. We also observe that the relative majority of genes causing human myopia are involved in the processing of optical defocus. Conclusions Together, our results support the hypothesis that optical defocus is perceived by the retina using contrast as a proxy and provide new insights into molecular signaling underlying refractive eye development.

Comparison of contrast sensitivity in myopic patients using spectacle and contact lens correction

Aim: To compare the contrast sensitivity in different categories of myopia using two different optical correction spectacles and contact lens correction. Methods: This cross-sectional study in design was conducted from August 2018 to May 2019 at the Ophthalmology Department of Madinah Teaching Hospital Faisalabad.45 subjects corrected with spectacles lenses and contact lenses all had corrected visual acuity of 6/9 or better were studied.The extent of myopia determined the three groups. All individuals were subjected to spectacles and Contact lens correction using slitlamp for anterior eye examination and for the fundus examination. The assessment of visual acuity was carried out by the Snellen vision Chart at 6m distance and contrastssensitivity was tested by Pelli- Robson chart. Results: Results showed a significant relationship between contrast sensitivity and type of optical correction. There were significant results of the independent t-test for spectacle and contact lenses 0.00 (p<0.005). However, the mean contrast sensitivity was better for all the three groupswith contact lens correction as compared to spectacle lens correction.Contact lenses provide better contrast sensitivity than spectacle lenses. Conclusion: Comparison between contact lens and spectacle correction was done and better quality contact lenses reduce optical defocus and give better results of contrast sensitivity. Results also concluded that loss of contrast sensitivity will be interpreted as early loss of retinal functions in severe myopes. Keywords: Myopia, Contrast sensitivity, Spectacle lens, Contact lens

The Characteristics of Visual Function and Intervention in Deprivation Amblyopia in Limbal Dermoid Children After Keratoplasty: A Pilot Study of Adopting Flank-Mask Perceptual Learning

BackgroundTo compare visual acuity and CSF improvement with perceptual learning versus part-time patching in limbal dermoid children after keratoplasty.MethodsAll children in the limbal dermoid and normal group underwent visual acuity and CSF evaluation, and the normal group wore the optical defocus to simulate the corresponding visual acuity of the limbal dermoid group. Among the limbal dermoid children, 9 underwent perceptual learning(PL), and 8 underwent part-time patching for 6 months and were followed for 6 months to evaluate visual acuity and CSF.ResultsRegarding CSF, the area under log CSF (AULCSF) and the cutoff spatial frequency (cutoff SF) were obviously reduced in the limbal dermoid group compared with the optical defocus group and normal viewing group (1.29±0.27 vs 0.40±0.05 vs 0.70±0.05, and 5.38±0.75 vs 8.81±0.74 vs 14.81±0.89, all p value <0.05). Following PL, visual acuity increased from 0.63±0.11 to 0.32±0.09 (P=0.04) . Contrast sensitivity increased mainly in the low special frequencies as AULCSF improved from 0.49±0.15 to 0.73±0.18 (P=0.32), 0.78±0.21 (P=0.28), 0.80±0.19 (P=0.22) and 1.06±0.20 (P=0.04) from baseline to the 6th month in the PL group, while it remained unchanged in the part-time patching group.ConclusionsChildren suffering from limbal dermoid with amblyopia exhibited CSF deficits and perceptual learning was found to improve VA and CSF in the amblyopic eye better than patching.Trial registrationThe study was registered at clinicaltrials.gov (PRS, ID NCT03447041).

Additive effect of atropine eye drops and short-term retinal defocus on choroidal thickness in children with myopia

Atropine eye drops and myopic retinal defocus each slow progression of myopia (short-sight). They also cause thickening of the choroid, and it has been suggested that the thickening is a precursor for reduced eye growth and slowed myopia progression. We investigated whether choroidal thickening due to optical defocus would add to thickening due to atropine when both were applied simultaneously. Addition would suggest that combining the two clinical treatments may improve efficacy of myopia control. We studied 20 children receiving 0.3% atropine daily for myopia control, over a period of 6 months. We imposed short periods of retinal defocus (1 h of myopic or hyperopic defocus (± 2.00D)) both before, and after 1 week and 3 and 6 months of atropine treatment. Prior to atropine, myopic or hyperopic defocus caused significantly thicker or thinner choroids respectively (± 12 µm, p < 0.001). After one week of atropine alone, thickness had increased (+ 21 µm; SD 17 µm; p < 0.001), and it increased further (by + 13 µm; SD 6 µm; p < 0.001) when exposed to myopic defocus. Atropine abolished choroidal thinning in response to hyperopic defocus. These effects remained the same after 3 and 6 months of atropine treatment. Our results show that additive effects of atropine and optical defocus are present at the level of the choroid, and suggest that combining optical and pharmaceutical treatments is likely to enhance efficacy of clinical myopia control.

Genome-wide analysis of retinal transcriptome reveals common genetic network underlying perception of contrast and optical defocus detection

SUMMARYRefractive eye development is regulated by optical defocus in a process of emmetropization. Excessive exposure to negative optical defocus often leads to the development of myopia. However, it is still largely unknown how optical defocus is detected by the retina. Here, we used genome-wide RNA-sequencing (RNA-seq) to conduct analysis of the retinal genetic networks underlying contrast perception and refractive eye development. We report that the genetic network subserving contrast perception plays an important role in optical defocus detection and emmetropization. Our results demonstrate an interaction between contrast perception, the retinal circadian clock pathway and the signaling pathway underlying optical defocus detection. We also observe that the relative majority of genes causing human myopia are involved in the processing of optical defocus. Together, our results support the hypothesis that optical defocus is perceived by the retina using contrast as a proxy and provide new insights into molecular signaling underlying refractive eye development.