Ocular Shape Research Articles

Dynamic changes in ocular shape during human development and its implications for retina fovea formation.

The human fovea is known for its distinctive pit-like appearance, which results from the displacement of retinal layers superficial to the photoreceptors cells. The photoreceptors are found at high density within the foveal region but not the surrounding retina. Efforts to elucidate the mechanisms responsible for these unique features have ruled out cell death as an explanation for pit formation and changes in cell proliferation as the cause of increased photoreceptor density. These findings have led to speculation that mechanical forces acting within and on the retina during development underly the formation of foveal architecture. Here we review eye morphogenesis and retinal remodeling in human embryonic development. Our meta-analysis of the literature suggests that fovea formation is a protracted process involving dynamic changes in ocular shape that start early and continue throughout most of human embryonic development. From these observations, we propose a new model for fovea development.

Effect of the macular shape on hole findings in idiopathic macular hole differs depending on the stage of the macular hole

This study aimed to investigate the relationship between macular shape and idiopathic macular hole (MH) findings using an objective method. We present retrospective observational case series on patients with MH. The shape of the macular area was quantified using quadratic equations, and the ocular shape (OS) index was calculated. The correlation between the OS index and macular hole findings for each stage was evaluated. Pearson's correlation coefficient showed a significant correlation between the OS index and horizontal hole diameter (p = 0.044), bottom diameter (p = 0.006), and vertical bottom diameter (p = 0.024) in stage 2. For stage 4, there was a negative and significant correlation between the OS index and age (p = 0.037), and horizontal (p = 0.021) and vertical (p = 0.027) bottom diameter. Multiple regression analysis showed that the horizontal (p = 0.0070) and vertical (p = 0.031) bottom diameter and OS index were independently and positively correlated in stage 2. In stage 4, the OS index was independently and negatively correlated with the horizontal (p = 0.037) and vertical (p = 0.048) bottom diameter. The ocular shape of the macula affects MH findings, and its impact depends on its stage.

Assessment of Ocular Deformation in Pathologic Myopia Using 3-Dimensional Magnetic Resonance Imaging

Ocular deformation in pathologic myopia can affect the entire globe. However, few studies have investigated the equatorial pattern of ocular shape. In addition, the correlation between equatorial and posterior morphology needs to be further explored. To assess global ocular deformation in pathologic myopia. This hospital-based, cross-sectional study included 180 pathologic myopic eyes with atrophic maculopathy grading C2 (diffuse chorioretinal atrophy) or more from 180 participants who underwent comprehensive ophthalmic examination, including high-resolution 3-dimensional magnetic resonance imaging. In addition, 10 nonpathologic myopic eyes of 10 participants were set as the control group. According to the cross-sectional view of equator, equatorial shape was classified as round, rectangular, pyriform (noncircular and more protruded in 1 direction), vertical-elliptical, or horizontal-elliptical; according to the nasal and inferior views, the posterior shape was categorized as spheroidal, conical, bulb-shaped, ellipsoidal, multidistorted, and barrel-shaped. Equatorial circularity and ocular sphericity were used to quantitatively assess the morphological variability of the equatorial and posterior regions, respectively. The association between ocular morphology and ocular parameters and myopic maculopathy was also investigated. The mean (SD) age of 180 participants with pathologic myopia was 55.14 (10.74) years, 127 were female (70.6%), and the mean (SD) axial length of studied eyes was 30.22 (2.25) mm. The predominant equatorial shape was pyriform (66 eyes [36.7%]), followed by round (45 eyes [25.0%]). The predominant posterior shape was bulb-shaped (97 eyes [52.2%]), followed by multidistorted (46 eyes [24.7%]). Equatorial circularity and equatorial shapes were correlated (r = -0.469; 95% CI, -0.584 to -0.346; P < .001) and ocular sphericity was correlated with posterior shapes (r = -0.533; 95% CI, -0.627 to -0.427; P < .001). In eyes with a vertical-elliptical equator, equatorial circularity and ocular sphericity were positively linearly correlated (R2 = 0.246; 95% CI, 0.050-0.496; P = .002) and the prevalence of inferior staphyloma was higher (27.8%; P = .04). Eyes with a horizontal-elliptical equator have the most horizontally oriented axis of corneal flat keratometry (median, 43.55 [interquartile range, 43.84] degrees; P = .01) and tended to present with multidistorted posterior shape (21.7%; P = .04). These findings suggest ocular deformation is common in pathologic myopia and can affect the entire eye, including the equatorial and posterior regions. The morphological classification may enhance the understanding of the diverse patterns of ocular shape in pathologic myopia.

Ocular geometry in adults born extremely, very and moderately preterm with and without retinopathy of prematurity: results from the Gutenberg Prematurity Eye Study

Background/aimsTo evaluate whether anterior segment anatomy and axial length are associated with prematurity and perinatal factors in adults.MethodsThe Gutenberg Prematurity Eye Study examined adults born preterm and term aged 18–52...

Ultrawide field, distortion-corrected ocular shape estimation with MHz optical coherence tomography (OCT).

Ocular deformation may be associated with biomechanical alterations in the structures of the eye, especially the cornea and sclera in conditions such as keratoconus, congenital glaucoma, and pathological myopia. Here, we propose a method to estimate ocular shape using an ultra-wide field MHz swept-source optical coherence tomography (SS-OCT) with a Fourier Domain Mode-Locked (FDML) laser and distortion correction of the images. The ocular biometrics for distortion correction was collected by an IOLMaster 700, and localized Gaussian curvature was proposed to quantify the ocular curvature covering a field-of-view up to 65°×62°. We achieved repeatable curvature shape measurements (intraclass coefficient = 0.88 ± 0.06) and demonstrated its applicability in a pilot study with individuals (N = 11) with various degrees of myopia.

The Correlations between Horizontal and Vertical Peripheral Refractions and Human Eye Shape Using Magnetic Resonance Imaging in Highly Myopic Eyes.

The aim of this study was to determine the relationship between relative peripheral refraction and retinal shape by 2-D magnetic resonance imaging in high myopes. Thirty-five young adults aged 20 to 30 years participated in this study with 16 high myopes (spherical equivalent < −6.00 D) and 19 emmetropes (+0.50 to −0.50 D). An open field autorefractor was used to measure refractions from the center out to 60° in the horizontal meridian and out to around 20° in the vertical meridian, with a step of 3 degrees. Axial length was measured by using A-scan ultrasonography. In addition, images of axial, sagittal, and tangential sections were obtained using 2-D magnetic resonance imaging. The highly myopic group had a significantly relative peripheral hyperopic refraction and showed a prolate ocular shape compared to the emmetropic group. The highly myopic group had relative peripheral hyperopic refraction and showed a prolate ocular form. Significant differences in the ratios of height/axial (1.01 ± 0.02 vs. 0.94 ± 0.03) and width/axial (0.99 ± 0.17 vs. 0.93 ± 0.04) were found from the MRI images between the emmetropic and the highly myopic eyes (p < 0.001). There was a negative correlation between the retina’s curvature and relative peripheral refraction for both temporal (Pearson r = −0.459; p < 0.01) and nasal (Pearson r = −0.277; p = 0.011) retina. For the highly myopic eyes, the amount of peripheral hyperopic defocus is correlated to its ocular shape deformation. This could be the first study investigating the relationship between peripheral refraction and ocular dimension in high myopes, and it is hoped to provide useful knowledge of how the development of myopia changes human eye shape.

Ocular elongation and retraction in foveated reptiles.

Pronounced asymmetric changes in ocular globe size during eye development have been observed in a number of species ranging from humans to lizards. In contrast, largely symmetric changes in globe size have been described for other species like rodents. We propose that asymmetric changes in the three-dimensional structure of the developing eye correlate with the types of retinal remodeling needed to produce areas of high photoreceptor density. To test this idea, we systematically examined three-dimensional aspects of globe size as a function of eye development in the bifoveated brown anole, Anolis sagrei. During embryonic development, the anole eye undergoes dynamic changes in ocular shape. Initially spherical, the eye elongates in the presumptive foveal regions of the retina and then proceeds through a period of retraction that returns the eye to its spherical shape. During this period of retraction, pit formation and photoreceptor cell packing are observed. We found a similar pattern of elongation and retraction associated with the single fovea of the veiled chameleon, Chamaeleo calyptratus. These results, together with those reported for other foveated species, support the idea that areas of high photoreceptor packing occur in regions where the ocular globe asymmetrically elongates and retracts during development.

Morphological prediction of glaucoma by quantitative analyses of ocular shape and volume using 3-dimensional T2-weighted MR images

Elongated axial length of the eye increases the morbidity of glaucoma. Myopia also associates with elongated axial length, and such ellipsoid shape of the eyeball strongly contributes its pathogenesis. Morphological features of the eyeballs, which could be important factors for developing glaucoma, have not been well described. The aim of this study was to investigate the three-dimensional (3D) topographic features of glaucomatous eyeballs with/without myopia to evaluate the potential of those features for predicting glaucoma. Using a 3.0-tesla MRI, volume-isotropic turbo-spin-echo acquisition T2-weighted images were obtained from 55 patients with glaucoma and 22 controls to delineate the eyeballs. Eyeball volumes, axial lengths and transverse lengths were semi-automatically calculated and compared between four groups: normal, myopia, glaucoma, and glaucoma with myopia. Both glaucoma and myopia increased the eyeball volume compared to the normal eyes. An increased anisotropy ratio (axial/transversus length) was observed in myopic eyes compared to normal, whereas in the glaucomatous eyes, with or without myopia, no increase in anisotropy ratio was observed. Increasing volume of eyes can be caused by myopia and glaucoma. Myopic eyes were ellipsoid in shape, but there was less anisotropy and a near-spherical shape in glaucomatous eyes, even in glaucomatous myopic eyes.

Ocular size and shape in lens-induced Myopization in young Guinea pigs

BackgroundLens-induced myopization in guinea pigs has been used as model for the process of myopization in humans. It has not been explored yet whether the change in globe shape in eyes undergoing myopization is similar in experimental myopia in guinea pigs and in clinical myopia in patients.MethodsThe study included 70 guinea pigs (age:2–3 weeks) equally divided into a study group with lens-induced myopization for 5 weeks, and a control group wearing goggles with no refractive power. The globe diameters were measured using a microcaliper after enucleation.ResultsThe horizontal globe diameter (9.19 ± 0.15 mm versus 9.15 ± 0.18 mm; P = 0.25) and vertical globe diameter (9.02 ± 0.11 mm versus 8.99 ± 0.14 mm; P = 0.29) did not differ significantly between the study group and control group. The sagittal diameter was significantly longer in the study group (8.96 ± 0.15 mm versus 8.84 ± 0.14 mm; P = 0.001). While the vertical and horizontal globe diameters were correlated with each other in a ratio of approximately 1:1 (non-standardized regression coefficient B:0.94;95% confidence interval (CI):0.73,1.15), the steepness of the regression lines of the associations of both diameters with the sagittal diameter were flatter (horizontal to sagittal diameter: B: 0.64; 95% CI: 0.44,0.83; vertical to sagittal diameter:B:0.55;95% CI:0.41,0.69). Correspondingly, the ratios of horizontal-to-sagittal globe diameter and of vertical-to-sagittal globe diameter decreased (P < 0.001) with longer sagittal diameter.ConclusionsFor each mm axial elongation in young guinea pigs the horizontal globe diameter increased by 0.64 mm (95%CI:0.44,0.83) and the vertical diameter by 0.55 mm (95% CI:0.41,0.69), indicating that the globe enlargement occurred predominantly in the sagittal direction. Axial elongation in guinea pigs led to a similar relative change in ocular shape as in humans.

Systematic Analysis of Transcriptomic Profile of the Effects of Low Dose Atropine Treatment on Scleral Fibroblasts using Next-Generation Sequencing and Bioinformatics.

This study has two novel findings: it is not only the first to deduct potential genes involved in scleral growth repression upon atropine instillation from a prevention point of view, but also the first to demonstrate that only slight changes in scleral gene expression were found after atropine treatment as side effects and safety reasons of the eye drops are of concern. The sclera determines the final ocular shape and size, constituting of scleral fibroblasts as the principal cell type and the major regulator of extracellular matrix. The aim of our study was to identify differentially expressed genes and microRNA regulations in atropine-treated scleral fibroblasts that are potentially involved in preventing the onset of excessive ocular growth using next-generation sequencing and bioinformatics approaches. Differentially expressed genes were functionally enriched in anti-remodeling effects, comprising of structural changes of extracellular matrix and metabolic pathways involving cell differentiation. Significant canonical pathways were correlated to inhibition of melatonin degradation, which was compatible with our clinical practice as atropine eye drops are instilled at night. Validation of the dysregulated genes with previous eye growth-related arrays and through microRNA-mRNA interaction predictions revealed the association of hsa-miR-2682-5p-KCNJ5 and hsa-miR-2682-5p-PRLR with scleral anti-remodeling and circadian rhythmicity. Our findings present new insights into understanding the anti-myopic effects of atropine, which may assist in prevention of myopia development.

Advances in Whole-Eye Optical Coherence Tomography Imaging.

Contemporary anterior segment and retinal optical coherence tomography (OCT) systems only image their particular designated region of the eye and cannot image both areas of the eye at the same time. This separation is due to the differences in optical system design needed to properly image the front or back of the eye and also due to limitations in the imaging depth of current commercial OCT systems. More recently, research and commercial OCT systems capable of "whole-eye" imaging have been described. These whole-eye OCT systems enable applications such as ocular biometry for cataract surgery, ocular shape analysis for myopia, and others. Further, these whole-eye OCT systems allow us to image the eye as an integrated whole rather than as separate, independent divisions.

The Effects of Severe Myopia on the Properties of Sampling Units in Peripheral Retina.

Poor peripheral visual acuity in myopia may reflect, in part, photoreceptor misalignment with the exit pupil of the eye. We speculate that if such misalignment causes sufficient visual deprivation and/or disrupts retinal feedback processes, it may influence eye growth itself. It is known that myopic eyes have a reduced peripheral resolution acuity relative to emmetropic eyes, though it remains unclear how mechanical stretching of the retina in myopia impacts on peripheral visual performance. Our aim was to determine how retinal stretching affects the properties of sampling units in peripheral vision. Three-dimensional magnetic resonance imaging provided a depiction in vivo of ocular shape, allowing the inter-eye ratio of retinal image surface areas and the relative alignment of surfaces to be determined in our observer, who was unique in having severe myopia in the right eye (~21 D) but only modest myopia in the left (~3 D). Visual performance was assessed for the detection and direction discrimination of drifting sinusoids positioned 40° in the temporal retina. Applying the sampling theorem to our measures, we estimated the density and cut-off frequency of the underlying sampling units. The retinal image surface area of the right eye was 40% larger than that of the left and was rotated 8.9° anticlockwise relative to the left eye's image surface. In agreement with a linear stretch model of myopia, the sampling density of the right eye was reduced by approximately the same ratio as that predicted from the inter-eye MRI data, namely, 1.18. However, the cut-off frequency (cycles/mm) of the right eye was approximately half that of the left, a reduction that cannot be explained solely by a linear areal expansion of retinal sampling units. Poor peripheral acuity in severe myopia may be caused, at least in part, by receptoral misalignment with the exit pupil.

Methodology of the ZOC-BHVI High Myopia Cohort Study: The Onset and Progression of Myopic Pathologies and Associated Risk Factors in Highly Myopic Chinese

ABSTRACTPurpose: The increasing prevalence of high myopia and its associated pathologies has raised challenges to ophthalmic services. This project aims to explore the onset and progression of myopic pathologies in highly myopic eyes through a prospective research cohort established in South China.Methods: Patients with high myopia (sphere ≤ −6.00 D) visiting the optometric clinic of Zhongshan Ophthalmic Center (ZOC) were invited to participate in the baseline examinations and follow-up visit over a 10-year period. People having secondary myopia, history of any refractive surgery, significant ocular media opacity, or other severe health problems were excluded. The measurements included visual acuity, ocular biometry, visual function, cycloplegic refraction, fundus imaging, ocular shape by MRI, blood tests and questionnaires.Results: A total of 890 participants completed the baseline examinations, with a mean age at baseline of 22.7 ± 12.4 years. The mean spherical equivalent at baseline was 10.13 ± 3.65 D, and the mean axial length (AL) was 27.52 ± 1.63 mm. The older subjects tended to have more severe myopia and longer ALs.Conclusion: The study will provide new knowledge on the relationship between high myopia and pathological changes such as myopic macular degeneration and staphyloma.

Three-Dimensional Eye Shape, Myopic Maculopathy, and Visual Acuity: The Zhongshan Ophthalmic Center–Brien Holden Vision Institute High Myopia Cohort Study

To investigate the relationship among eye shape, myopic maculopathy, and visual acuity in highly myopic eyes using 3-dimensional (3D) magnetic resonance imaging (MRI). Observational case series. The study included 190 eyes of 95 participants with bilateral high myopia from the Zhongshan Ophthalmic Center-Brien Holden Vision Institute High Myopia Cohort Study, with spherical power ≤-6.00 diopters (D) in both eyes. The participants underwent best-corrected visual acuity (BCVA), fundus photography, cycloplegic refraction, and ocular biometry. Posterior staphyloma was identified with 3D MRI, and ocular shapes were categorized into spheroidal, ellipsoidal, conical, nasally distorted, temporally distorted, and barrel shapes according to the inferior view from T2-weighted 3D MRI (Achieva 3.0T; Philips Medical Systems, Best, the Netherlands). Myopic maculopathy was graded as C0 to C4 according to the International Photographic Classification and Grading System using fundus photography. The statistical significance of the differences in distribution of myopic maculopathy and BCVA in eyes with different ocular shapes was determined using Pearson's chi-square tests. Distributions of myopic maculopathy and BCVA in relation to different eye shapes. The mean spherical equivalent and axial length were-11.74±4.10 D and 28.18±1.73 mm in the right eyes, respectively. The same ocular shapes were observed in both eyes in 69 participants (72.6%). The predominant shape was spheroidal (53.7%), followed by nasally distorted and conical types (both 14.7%). C2 and above myopic maculopathy was observed in all barrel-shaped eyes, in 75% temporally distorted eyes, and in 71.4% nasally distorted and conical eyes. In eyes with posterior staphyloma (n= 22), 18 (81.8%) had C2 and above myopic maculopathy compared with 40 eyes (54.8%) without posterior staphyloma (n= 73). Eyes with temporal and nasal distortion, and eyes with staphyloma were more likely to have BCVA <20/40. Not all highly myopic eyes are deformed. Spheroid was the predominant ocular shape in this series of young patients with high myopia bilaterally. Barrel-shaped and temporally distorted eyes present significant myopic maculopathy, whereas eyes with posterior staphyloma display more severe chorioretinal atrophy. Eyes of more deformed shapes tend to have more severe myopic maculopathy and worse BCVA.

B-mode ocular ultrasound findings in adults with refractive errors at Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria

Objective: To ascertain the relationship between B-mode ocular ultrasound findings and standard autorefraction results of participants with refractive errors, with the aim of using B-mode ultrasound as a complementary technique to determine the refractive state of the eye. Materials and Methods: The study population consisted of 255 adult patients with refractive errors, aged 18–40 years. The ocular dimensions were measured using MINDRAY DC-7.0 real-time ultrasound machine with frequency probe of 5 and 7–12 MHz. The ocular shapes and other biometric measurements were then correlated with the results of the standard autorefraction. Results: The sensitivity for prolate ocular shape corresponding with myopia/astigmatism was 88.6%, whereas that of oblate ocular shape corresponding with hyperopia/astigmatism was 87.4%. The Pearson’s correlation coefficient between right axial length and right spherical equivalent was negatively strong at −0.79 (P Conclusion: Real-time B-mode ocular ultrasound has a high sensitivity in determining ocular shape, which corresponded well with the refractive state of the participants’ eyes. Axial length (AL) was found to correlate strongly with spherical equivalent, and, thus, a regression equation can be used to predict the spherical equivalent from the AL measurements.

Morphological and clinical characteristics of myopic posterior staphyloma in Caucasians.

We aimed to study the morphological characteristics of myopic posterior staphyloma in Caucasians and to evaluate the correlation between posterior staphyloma, myopic macular lesions and visual acuity. Ninety eyes of 67 consecutive patients affected by high myopia associated with posterior staphyloma were recruited between January 2012 and December 2013. Posterior staphyloma was classified according to Curtin's criteria. Every patient underwent fundoscopic examination and best corrected visual acuity measurement (BCVA). A and B-scan ultrasound (US), high-resolution, three-dimensional magnetic resonance image (MRI), optical coherence tomography (OCT), fundus autofluorescence (FAF), red free (RF) and color fundus photography studies were performed. The mean age was 64.4 ± 9.48years (range: 41-82). The mean BCVA was 0.7 ± 0.5 logMAR (range: 0-2). The mean axial length was 29.92 ± 2.39 millimeters (range: 24.25-36.53). The authors found four types of posterior staphyloma according to Curtin's classification: I, II, IV and IX. Significant prevalence of posterior staphyloma in female sex was observed (p = 0.0235). Significant correlation between the depth and the diameters of posterior staphyloma was demonstrated (p < 0.0001). Significant association between posterior staphyloma type and tomographic foveal patterns (p = 0.0230) was highlighted. Posterior staphyloma type I was more frequently associated with peripapillary atrophy and less with macular atrophy compared to type II and IX (p = 0.0169). The prevalence of macular atrophy was more than double in posterior staphyloma type II (33.3%) in comparison to posterior staphyloma type I (12.5%). This study confirms that the type I and II are the most common types of posterior staphyloma, as already highlighted in the literature. A significant association between the type of posterior staphyloma and the MRI ocular shape pattern, the OCT patterns of macular profile and the location of chorioretinal atrophy was highlighted. The correlation between the depth and the width of posterior staphyloma has demonstrated that the deeper the staphyloma, the wider it was. The deepest area of the posterior staphyloma was characterized by a greater thinning of the sclera and by a higher prevalence of chorioretinal atrophy compared to the other parts of the eye. More studies are necessary to support our findings and to add more information on the natural evolution of posterior staphyloma and on its associated complications.

Effect of ocular shape and vascular geometry on retinal hemodynamics: a computational model.

A computational model for retinal hemodynamics accounting for ocular curvature is presented. The model combines (i) a hierarchical Darcy model for the flow through small arterioles, capillaries and small venules in the retinal tissue, where blood vessels of different size are comprised in different hierarchical levels of a porous medium; and (ii) a one-dimensional network model for the blood flow through retinal arterioles and venules of larger size. The non-planar ocular shape is included by (i) defining the hierarchical Darcy flow model on a two-dimensional curved surface embedded in the three-dimensional space; and (ii) mapping the simplified one-dimensional network model onto the curved surface. The model is solved numerically using a finite element method in which spatial domain and hierarchical levels are discretized separately. For the finite element method, we use an exterior calculus-based implementation which permits an easier treatment of non-planar domains. Numerical solutions are verified against suitably constructed analytical solutions. Numerical experiments are performed to investigate how retinal hemodynamics is influenced by the ocular shape (sphere, oblate spheroid, prolate spheroid and barrel are compared) and vascular architecture (four vascular arcs and a branching vascular tree are compared). The model predictions show that changes in ocular shape induce non-uniform alterations of blood pressure and velocity in the retina. In particular, we found that (i) the temporal region is affected the least by changes in ocular shape, and (ii) the barrel shape departs the most from the hemispherical reference geometry in terms of associated pressure and velocity distributions in the retinal microvasculature. These results support the clinical hypothesis that alterations in ocular shape, such as those occurring in myopic eyes, might be associated with pathological alterations in retinal hemodynamics.

The influence of end of day silicone hydrogel daily disposable contact lens fit on ocular comfort, physiology and lens wettability

To quantify the end-of-day silicone-hydrogel daily disposable contact lens fit and its influence of on ocular comfort, physiology and lens wettability. Thirty-nine subjects (22.1±3.5 years) were randomised to wear each of 3 silicone-hydrogel daily-disposable contact lenses (narafilcon A, delefilcon A and filcon II 3), bilaterally, for one week. Lens fit was assessed objectively using a digital video slit-lamp at 8, 12 and 16h after lens insertion. Hyperaemia, non-invasive tear break-up time, tear meniscus height and comfort were also evaluated at these timepoints, while corneal and conjunctival staining were assessed on lens removal. Lens fit assessments were not different between brands (P>0.05), with the exception of the movement at blink where narafilcon A was more mobile. Overall, lag reduced but push-up speed increased from 8 to 12h (P<0.05), but remained stable from 12 to 16h (P>0.05). Movement-on-blink was unaffected by wear-time (F=0.403, P=0.670). A more mobile lens fit with one brand did not indicate that person would have a more mobile fit with another brand (r=-0.06 to 0.63). Lens fit was not correlated with comfort, ocular physiology or lens wettability (P>0.01). Among the lenses tested, objective lens fit changed between 8h and 12h of lens wear. The weak correlation in individual lens fit between brands indicates that fit is dependent on more than ocular shape. Consequently, substitution of a different lens brand with similar parameters will not necessarily provide comparable lens fit.

End of day silicone hydrogel daily disposable contact lens fit

Purpose: To quantify the end-of-day silicone-hydrogel daily disposable contact lens fit and its influence of on ocular comfort, physiology and lens wettability. Method: Thirty-nine subjects (22.1±3.5 years) were randomised to wear each of three silicone-hydrogel daily-disposable contact lenses (narafilcon A, delefilcon A and filcon II 3), bilaterally, for oneweek. Lens fit was assessed objectively using a digital video slit-lamp at 8, 12 and 16h after lens insertion. Hyperaemia, noninvasive tearbreak-up time, tearmeniscusheight andcomfortwere also evaluated at these timepoints, while corneal and conjunctival staining were assessed on lens removal. Results: Lens fit assessments were not statistically significantly different between brands (p>0.05), with the exception of the movement at blink; narafilcon A lenses moved further on blink (0.41±0.34mm) than delefilcon A (0.33±0.21mm; p=0.030) and filcon II 3 (0.33±0.25mm; p=0.044) lenses. Overall, lag reduced from 8 to 12h (77±52% vs 69±31%; p=0.046), but remained stable from 8 to 16h (71±31%; p=0.231). Pushup recovery speed increased from 8 to 12h (0.61±0.41mm/s vs 0.76±0.47mm/s; p=0.004), but remained stable from 8 to 16h (0.73±0.40mm; p=0.621). Movement-on-blink was unaffected by wear-time (0.34±0.24mm 8h; 0.35±0.28mm 12h; 0.36±0.28mm 16h; F=0.403, p=0.670). A more mobile lens fit with one brand did not indicate that personwould have amoremobile fitwith another brand (r = 0.060.63). Lens fit was not correlated with comfort, ocular physiology or lens wettability (p>0.01). Conclusions: Among the lenses tested, objective lens fit changed between 8h and 12h of lens wear. The weak correlation in individual lens fit between brands indicates that fit is dependent on more than ocular shape. Consequently, substitution of a different lens brand with similar parameters will not necessarily provide comparable lens fit. Additional studies should be done to further assess the clinical implications of fit.

Automated retinal topographic maps measured with magnetic resonance imaging.

Recent studies on ocular shape have raised increased interest in the peripheral characteristics of the eye, as it potentially triggers changes in the central vision. Current techniques are, however, not capable of accurately measuring the three-dimensional shape of the retina. We describe a new magnetic resonance imaging (MRI)-based method to obtain the retinal shape with high precision and use it to assess if differences in retinal shape could explain previously described trends in peripheral refraction. Twenty-one healthy subjects were examined using high-field ocular MRI. The resulting data were automatically segmented and processed to calculate the retinal topographic map. We validated the method against partial coherence interferometry and assessed the reproducibility for four subjects. The retinal topographic maps describe the retinal shape with subpixel reproducibility (SD between sessions = 0.11 mm). Comparison with partial coherence interferometry showed a mean difference of 0.08 mm, 95% confidence interval -0.39 to 0.55 mm, with a standard deviation of 0.23 mm. The data give a possible geometric explanation for the previously described trend in myopic eyes toward relatively hyperopic refraction in the periphery, with full three-dimensional information. The retinal maps furthermore show small, submillimeter, irregularities that could have an important influence on the subjects' peripheral vision. The possibility to quantitatively characterize the full three-dimensional retinal shape by MRI offers new ophthalmologic possibilities, such as quantitative geometric description of staphyloma. It could in addition be used as a validation technique, independent of standard optical methods, to measure the peripheral retinal shape.