Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)最新文献

{"title":"Multifocal contact lens design, not addition power, affects accommodation responses in young adult myopes.","authors":"Kate L Gifford,&nbsp;Katrina L Schmid,&nbsp;Josh M Collins,&nbsp;Clare B Maher,&nbsp;Riya Makan,&nbsp;Evonne Nguyen,&nbsp;Gemma B Parmenter,&nbsp;Bronte M Rolls,&nbsp;Xinyue S Zhang,&nbsp;David A Atchison","doi":"10.1111/opo.12892","DOIUrl":"https://doi.org/10.1111/opo.12892","url":null,"abstract":"<p><strong>Purpose: </strong>Prolonged nearwork has been implicated in myopia progression. Accommodation responses of young-adult myopes wearing different multifocal contact lenses were compared.</p><p><strong>Methods: </strong>Twenty adults, 18-25 years, with myopia (spherical equivalent refraction -0.50 to -5.50 D, mean -2.1 ± 1.6 D) wore five lens types in random order: Proclear single vision distance (SV), MiSight concentric dual-focus +2.00 D Add (MS), Biofinity aspheric centre distance +1.50 D Add (CD1) and +2.50 D Add (CD2) (all Coopervision), and NaturalVue aspheric (Visioneering Technologies) (NVue). Using a Grand-Seiko WAN-5500 autorefractor with binocular correction and viewing right eye accommodative responses were measured after a 10 min adaptation period at 4.0, 1.0, 0.5, 0.33 and 0.25 m distances. Dynamic measurements were taken for 4 s at 6 Hz. Accommodative stimuli and responses were referenced to 4 m (i.e., refraction differences between 4 m and nearer distances). Accommodation lags and refraction instabilities (standard deviations of dynamic responses) were determined. For comparison, results were obtained for an absolute presbyopic eye, where trial lenses counteracted the accommodation stimulus.</p><p><strong>Results: </strong>For SV and MS, accommodation responses were similar to the stimulus values. For aspheric lenses CD1, CD2 and NVue, accommodation responses were approximately 1.0 D lower across the stimulus range than with SV and MS, and rates of change were approximately 0.84 D per 1 D stimulus change. MS produced greater refraction instabilities than other lenses. For the presbyope, changes in refraction matched the trial lenses, indicating that corrections due to measurement through the different lenses were not needed.</p><p><strong>Conclusion: </strong>Reductions in accommodation response occurred in young myopes wearing aspheric multifocal contact lenses independent of the labelled 'add' power. The concentric dual-focus MS lens produced minimal lags but had greater instability than the other lenses. The results indicate that the mechanism of multifocal contact lenses slowing myopia progression is unlikely to be through relaxing accommodation, at least in young adults.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1346-1354"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39483060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A validated finite element model to reproduce Helmholtz's theory of accommodation: a powerful tool to investigate presbyopia.","authors":"Iulen Cabeza-Gil,&nbsp;Jorge Grasa,&nbsp;Begoña Calvo","doi":"10.1111/opo.12876","DOIUrl":"https://doi.org/10.1111/opo.12876","url":null,"abstract":"<p><strong>Purpose: </strong>To reproduce human in vivo accommodation numerically. For that purpose, a finite element model specific for a 29-year-old subject was designed. Once the proposed numerical model was validated, the decrease in accommodative amplitude with age was simulated according to data available in the literature.</p><p><strong>Methods: </strong>In contrast with previous studies, the non-accommodated eye condition was the reference configuration. Consequently, two aspects were specifically highlighted: contraction of the ciliary muscle, which was simulated by a continuum electro-mechanical model and incorporation of initial lens capsule stresses, which allowed the lens to become accommodated after releasing the resting zonular tension.</p><p><strong>Results: </strong>The morphological changes and contraction of the ciliary muscle were calibrated accurately according to the experimental data from the literature. All dynamic optical and biometric lens measurements validated the model. With the proposed numerical model, presbyopia was successfully simulated.</p><p><strong>Conclusions: </strong>The most widespread theory of accommodation, proposed by Helmholtz, was simulated accurately. Assuming the same initial stresses in the lens capsule over time, stiffening of the lens nucleus is the main cause of presbyopia.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1241-1253"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/opo.12876","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39370227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reappraisal of the historical myopia epidemic in native Arctic communities.","authors":"Jos J Rozema,&nbsp;Charles Boulet,&nbsp;Yuval Cohen,&nbsp;William K Stell,&nbsp;Luciano Iribarren,&nbsp;Ger H M B van Rens,&nbsp;Rafael Iribarren","doi":"10.1111/opo.12879","DOIUrl":"https://doi.org/10.1111/opo.12879","url":null,"abstract":"<p><strong>Purpose: </strong>This study was developed to explain the extraordinary rise in myopia prevalence beginning after 1950 in Indigenous Arctic communities considering recent findings about the risk factors for school myopia development. Myopia prevalence changed drastically from a historical low of less than 3% to more than 50% in new generations of young adults following the Second World War. At that time, this increase was attributed to concurrent alterations in the environment and way of life which occurred in an aggressive programme of de-culturalization and re-acculturation through residential school programmes that introduced mental, emotional and physical stressors. However, the predominant idea that myopia was genetic in nature won the discussion of the day, and research in the area of environmental changes was dismissed. There may have also been an association between myopia progression and the introduction of extreme mental, emotional and physical stressors at the time.</p><p><strong>Recent findings: </strong>Since 1978, animal models of myopia have demonstrated that myopiagenesis has a strong environmental component. Furthermore, multiple studies in human populations have shown since 2005 how myopia could be produced by a combination of limited exposure to the outdoors and heavy emphasis on academic subjects associated with intense reading habits. This new knowledge was applied in the present study to unravel the causes of the historical myopia epidemics in Inuit communities.</p><p><strong>Summary: </strong>After reviewing the available published data on myopia prevalence in circumpolar Inuit populations in the 20th century, the most likely causes for the Inuit myopia epidemic were the combination of increased near work (from almost none to daily reading) and the move from a mostly outdoor to a much more indoor way of life, exacerbated by fewer hours of sunshine during waking hours, the lower illuminance in the Arctic and the extreme psychophysical stress due to the conditions in the Residential Schools.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1332-1345"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/opo.12879","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39426372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing optimal colour and illumination to facilitate reading: an analysis of print size.","authors":"Elliott Morrice,&nbsp;Caitlin Murphy,&nbsp;Vanessa Soldano,&nbsp;Cynthia Addona,&nbsp;Walter Wittich,&nbsp;Aaron P Johnson","doi":"10.1111/opo.12885","DOIUrl":"https://doi.org/10.1111/opo.12885","url":null,"abstract":"<p><strong>Purpose: </strong>This study examined how optimal colour/illumination conditions and the efficacy of the iPad, LuxIQ and Smart Bulb varied as a function of print size in younger, older and visually impaired adults.</p><p><strong>Methods: </strong>Participants with visual impairments and simulated low vision (SLV) read the MNRead using the iPad, LuxIQ and Smart Bulb.</p><p><strong>Results: </strong>In the impairment condition at 1.20 logMAR, the iPad (M = 9.49, 95% CI [3.18, 19.42]) and LuxIQ (M = 15.95, 95% CI [9.54, 24.86]) improved the reading speeds. At 0.80 logMAR (SLV), all devices improved reading speeds of older adults (iPad (M = 28.70, 95% CI [14.65, 42.51]); LuxIQ (M = 49.63, 95% CI [30.04, 69.68]); Smart Bulb (M = 23.11, 95% CI [3.33, 42.11])), but in younger adults only the LuxIQ (M = 13.04, 95% CI [3.21, 21.27]) did so. In the impairment condition, the iPad (M = 5.54, 95% CI [0.31, 12.13]) and LuxIQ (M = 13.90, 95% CI [7.88, 23.49]) improved reading speeds. In the SLV condition, age was a significant predictor of reading speed at 1.20 logMAR (F_3,164  = 10.74, p < 0.001, Adj. R²  = 0.16). At 0.80 logMAR, age and luminance, but not colour, were significant predictors (F_3,164  = 52.52, p < 0.001, Adj. R²  = 0.49). In the impairment condition, both age and lux were significant predictors of reading speed at 1.20 (F_3,85  = 7.14, p < 0.001, Adj. R²  = 0.20) and 0.80 logMAR (F_3,85  = 7.97, p < 0.001, Adj. R²  = 0.22), but colour was not.</p><p><strong>Conclusions: </strong>Light source effectiveness and optimal colour/illumination vary as a function of print size. It appears that print size is the most important factor for improving reading speed. As print size decreases, luminance becomes crucial, and only at the smallest print sizes does the effect of colour become useful.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1209-1221"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39437357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Greater axial elongation associated with low accommodative lag: new insights on accommodative lag theory for myopia.","authors":"Swapnil Thakur,&nbsp;Pavan K Verkicharla","doi":"10.1111/opo.12893","DOIUrl":"https://doi.org/10.1111/opo.12893","url":null,"abstract":"<p><strong>Purpose: </strong>We aimed to test the accommodative lag and mechanical tension theories for myopia by assessing the influence of the lag of accommodation on axial elongation by using three different near targets that are known to influence the accommodative response differently.</p><p><strong>Methods: </strong>Forty-two young adults were recruited for the study. Axial length was measured using a non-contact biometer, before and immediately after a 15 minute visual task, with one of the three near targets placed 20 cm from the eye: reading text from a paper, reading text from a smartphone and watching a video on a smartphone. The accommodative response was determined using an open-field autorefractor while the participants viewed the near target monocularly.</p><p><strong>Results: </strong>Lag of accommodation was significantly different for the three tasks: watching a video (mean ± standard error of the mean [SEM] 0.92 ± 0.10 D); reading text on the smartphone (0.59 ± 0.08 D); and reading text on paper (0.24 ± 0.09 D). There was a significant (p < 0.05) increase in axial length after reading text from a paper (10.5 ± 1.9 µm after 15-min) and reading text from a smartphone (5.2 ± 2.7 µm), but not after watching a video on a smartphone (-0.5 ± 1.7 µm, p = 0.47). Vitreous chamber depth increased significantly more with the reading tasks compared with watching a video (reading text from a paper and smartphone: 33.9 ± 4 µm and 31.7 ± 4 µm vs. watching a video on a smartphone: 14.6 ± 5 µm, p = 0.001).</p><p><strong>Conclusion: </strong>Greater changes in axial length associated with the low lag of accommodation failed to support the theory that lag of accommodation during visual tasks could be the trigger for axial elongation. Reading on paper and smartphone at the closest reading distance may stimulate high accommodative demand and axial elongation as a consequence, possibly due to increased \"ciliary muscle tension\" during accommodation.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1355-1362"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39453344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The impact of spectacle lenses for myopia control on visual functions.","authors":"Yi Gao,&nbsp;Ee Woon Lim,&nbsp;Adeline Yang,&nbsp;Björn Drobe,&nbsp;Mark A Bullimore","doi":"10.1111/opo.12878","DOIUrl":"https://doi.org/10.1111/opo.12878","url":null,"abstract":"<p><strong>Purpose: </strong>Spectacle lenses containing multiple small peripheral elements have been developed for myopia control in children. It is important that their effect on vision be quantified by (i) fixation through the peripheral portion, thereby using foveal vision and (ii) by fixation through the central portion and presentation of peripheral targets.</p><p><strong>Methods: </strong>The above approaches were used in five studies to evaluate two novel spectacle lens designs: spectacle lenses with Highly Aspherical Lenslets (HAL) and Slightly Aspherical Lenslets (SAL). A single vision lens served as a control. Visually normal adults participated in each study. The first two studies had subjects fixate through the periphery of the lenses. High and low (10%) contrast visual acuity was measured with the Freiburg Vision Test and reading speed for high and low contrast words measured with a sentence generator. The other three studies assessed peripheral vision while subjects fixated through the central portion of the lens. Peripheral contrast sensitivity was measured using two cycles per degree drifting Gabor stimuli. Peripheral motion perception was further evaluated using random dot stimuli. Finally, attention was measured using an established test of useful field of view with three levels of complexity.</p><p><strong>Results: </strong>The periphery of the HAL lens significantly reduced low contrast visual acuity, but not high contrast visual acuity, while the effect of the SAL lens was not significant for either. Neither test lens affected reading speed for high contrast words, but the HAL lens significantly affected performance for low contrast words. Neither test lens affected peripheral motion perception or useful field of view.</p><p><strong>Conclusions: </strong>Low contrast visual acuity and reading was slightly reduced while high contrast visual acuity was unaffected when fixating through the periphery of the novel lens designs. None of the peripheral measures of vision was affected by the novel lens designs.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1320-1331"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/opo.12878","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39421851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wide-field choroidal thickness and vascularity index in myopes and emmetropes.","authors":"Negareh Yazdani,&nbsp;Asieh Ehsaei,&nbsp;Hosein Hoseini-Yazdi,&nbsp;Nasser Shoeibi,&nbsp;David Alonso-Caneiro,&nbsp;Michael J Collins","doi":"10.1111/opo.12875","DOIUrl":"https://doi.org/10.1111/opo.12875","url":null,"abstract":"<p><strong>Purpose: </strong>To study regional variations in choroidal thickness (CT), luminal thickness and stromal thickness of the choroid, and choroidal vascularity index (CVI) in low myopic and emmetropic eyes using wide-field optical coherence tomography (OCT).</p><p><strong>Methods: </strong>Sixty-nine healthy young adults between 20 and 38 years of age participated in this study, including 40 low myopes (mean ± SD spherical equivalent (MSE) refractive error: -3.00 ± 1.39 D, range: -6.00 to -0.62 D) and 29 emmetropes (MSE: -0.05 ± 0.09 D, range: -0.25 to +0.12 D). Wide-field CT, luminal thickness, stromal thickness and CVI were measured across five eccentricities (fovea, parafovea, perifovea; near-periphery and periphery) and four quadrants (nasal, temporal, inferior and superior), in vertical and horizontal meridians, while controlling for a range of extraneous factors potentially influencing the CT. Custom-written software was used to segment and binarize the OCT images.</p><p><strong>Results: </strong>Wide-field CT, luminal thickness and stromal thickness, averaged across all participants, exhibited significant topographical variation, with the foveal (379 ± 8 µm, 200 ± 4 µm, 179 ± 4 µm, respectively) and peripheral (275 ± 8 µm, 161 ± 4 µm, 114 ± 4 µm, respectively) regions presenting the thickest and thinnest regions (all p < 0.001). Wide-field CVI showed a progressively higher percentage (greater vascularity) with increasing eccentricity from the fovea towards the periphery (p < 0.001). Macular CT and stromal choroidal thickness were significantly thinner in myopes compared to emmetropes (p < 0.05). Myopes (55.7 ± 0.3%) showed a slightly higher CVI compared with emmetropes (54.4 ± 0.4%) (p < 0.05).</p><p><strong>Conclusions: </strong>Low myopia in young adults was associated with significant choroidal thinning across the macular, but not extramacular regions, with this decrease in choroidal thickness mostly attributed to thinning in the stromal component of the choroid, rather than the luminal (vascular) component.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1308-1319"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/opo.12875","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39391064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corneal power values for use with keratoprostheses and intraocular lenses.","authors":"Michael J Simpson","doi":"10.1111/opo.12886","DOIUrl":"https://doi.org/10.1111/opo.12886","url":null,"abstract":"<p><strong>Purpose: </strong>To specify a keratoprosthesis (KPro) power value for use with an intraocular lens (IOL).</p><p><strong>Methods: </strong>Raytracing software was used to determine the imaging properties of both the natural cornea and conceptual KPro designs, and IOL power calculation methods were reviewed. Traditional calculations use 'thick lens' models for the overall eye, while also using 'thin lens' approximations for the cornea and IOL. The power of the natural cornea acts approximately at the apex, although this is unlikely to be the case for a KPro. The IOL location is determined using an empirical adjustment that is calculated from clinical results for natural eyes.</p><p><strong>Results: </strong>The use of a KPro has a similar optical effect to corneal refractive surgery, where the cornea no longer matches the original eye. A modification of the 'double-K' calculation method can be used by specifying the KPro effective power at the original corneal apex, but still estimating the postoperative IOL location using the original corneal power. The KPro power is measured by assembling the KPro with fluid and a window to simulate the way it is used, recording the best focus power at room temperature with a 3 mm diameter aperture, rescaling to the in situ power at 35°C using refractive index changes, and then rescaling again to the power expected relative to the original corneal apex. When expressed as a K value, a keratometer refractive index of 1.332 is proposed. If necessary, clinical results may be used later to make empirical adjustments to the calculation method.</p><p><strong>Conclusions: </strong>A KPro power can be specified relative to the expected location of the original corneal apex using a keratometer index of 1.332. A double-K calculation can then be used to determine the correct KPro and IOL power values for a pseudophakic eye.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1285-1291"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/opo.12886","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39425626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computer monitor pixellation and Landolt C visual acuity.","authors":"Andrew Carkeet,&nbsp;Lucas Lister,&nbsp;Yee Teng Goh","doi":"10.1111/opo.12882","DOIUrl":"https://doi.org/10.1111/opo.12882","url":null,"abstract":"<p><strong>Purpose: </strong>To investigate the effects of computer monitor pixel density on Landolt C visual acuity measurements and to provide appropriate pixel density recommendations for Landolt C vision chart design.</p><p><strong>Methods: </strong>Participants were 10 healthy observers aged 18-31 years (mean 21.7 ± 3.6). Logarithmic progression charts were used, consisting of eight rows of five Landolt C optotypes ranging from -0.40 logMAR to 0.30 logMAR. Monitor pixel angular subtense varied from 0.10 min arc to 1.97 min arc, achieved by changing the chart test distance. Testing took place with two filtering conditions: unfiltered optotypes, (pixels rendered either black or white) and anti-aliased optotypes with pixel luminance averaged for a pixel square and rendered as grey levels.</p><p><strong>Results: </strong>Each participant's acuity versus pixel size data sets were fitted by a nonlinear relationship with acuity equal to an asymptotic threshold visual acuity (VA_as ) for small pixel sizes below a critical pixel size (P_crit ). For pixel sizes larger than P_crit  there was a linear relationship between acuity thresholds and pixel size. For anti-aliased Landolt Cs, mean P_crit  was 1.23 min, and for unfiltered Landolt Cs average P_crit was 0.65 min. For anti-aliased LandoltCs, P_crit  was 2.01xVA_as , and for unfiltered Landolt Cs P_crit  was 1.05xVA_as .</p><p><strong>Conclusion: </strong>These results are quantitatively very similar to previous research on pixellation and Sloan optotype acuity. We have demonstrated that spatially filtering Landolt C optotypes acts as anti-aliasing, to make them more robust to the degradation effects of pixellation. Previous recommendations for maximum pixel size on Sloan letter vision charts can be applied safely to Landolt C charts.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1176-1182"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/opo.12882","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39426374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intra-session repeatability of anterior chamber depth across the chamber width using Pentacam Scheimpflug imaging in healthy subjects.","authors":"Jack Phu,&nbsp;Janelle Tong,&nbsp;Michael Kalloniatis","doi":"10.1111/opo.12880","DOIUrl":"https://doi.org/10.1111/opo.12880","url":null,"abstract":"<p><strong>Purpose: </strong>Despite the importance of anterior chamber depth (ACD) measurements in disease and ageing, the repeatability and their threshold for change is not known. Our purpose was to determine the intra-session repeatability of Pentacam Scheimpflug photography for measuring the ACD across the chamber width in healthy subjects and thus inform expected limits of normality.</p><p><strong>Methods: </strong>Pentacam Scheimpflug photography was used to obtain ACD measurements at 57 points across the central 8mm of the chamber width from one randomly selected eye of 130 healthy (normal vision and no ocular diseases, except age-normal cataracts) subjects (median age 58.0 years, interquartile range 46.3-63.0 years; 48 males, 82 females). Intra-session ACD measurements were compared. Univariate and multivariate linear regression was performed to identify categorical and continuous variables demonstrating a significant relationship with ACD and its repeatability.</p><p><strong>Results: </strong>Bland-Altman analyses showed no directional or depth-dependent bias in the difference between the first and second tests (mean bias -0.003 mm, 95% limits of agreement -0.115 to +0.109 mm). Multivariate analysis found gender to be a significant factor (p < 0.0001), but not age (p = 0.69) nor ethnicity (p = 0.65), although the model fit was poor (R²  = 0.004). There were no regional differences in repeatability measures found in males, but six locations in the superior aspect in females were found to be significantly different in their repeatability characteristics. Tolerance limits used to calculate the number of step sizes between <20 and >60-year-old age groups found 8.1-11.5 steps for females, and 7.5-9.2 steps for males.</p><p><strong>Conclusions: </strong>Scheimpflug imaging using the Pentacam has excellent intra-session repeatability. Only gender appeared to affect repeatability characteristics, manifesting with a greater number of meaningful steps of change between two extremes of age range in females compared to males, which provides guidance for identifying clinically significant and measurable change between tests.</p>","PeriodicalId":520731,"journal":{"name":"Ophthalmic & physiological optics : the journal of the British College of Ophthalmic Opticians (Optometrists)","volume":" ","pages":"1273-1284"},"PeriodicalIF":2.9,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1111/opo.12880","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"39391909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}