Sagittal height differences of disposable soft contact lenses

Giovanzana, Stefano; Ţălu, Ştefan; Nicoară, Simona Delia

doi:10.1007/s10792-019-01206-5

Cited by 5 publications

(7 citation statements)

References 12 publications

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“…A topography map can be used to determine if the astigmatic component of the refractive error is corneal, if it is regular or irregular and how far it extends to the peripheral cornea. This information will help to determine whether a soft toric or rigid corneal lens would be best suited, in addition to the correct diameter size and peripheral curve for rigid corneal lenses [294][295][296]. Corneal topography alone does not inform soft lens fit as this is dependent on the sagittal height of the cornea and lens (see sections 5.1.2 and 5.1.3); however it is required for base curve selection for rigid corneal lens types, especially with complex corneal shapes [297].…”

Section: Corneal Shapementioning

confidence: 99%

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BCLA CLEAR - Evidence-based contact lens practice

Wolffsohn

Dumbleton

Huntjens

et al. 2021

Contact Lens and Anterior Eye

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Section: Corneal Shapementioning

confidence: 99%

“…3). The sag of commercial mass produced lenses ranges from 3450 to 3907 μm [294] and the sagittal height of the healthy cornea has been found to be 3180 μm (range 2740− 3750 μm) or at a chord length of 15 mm, 3740 μm (range 3230− 4100 μm) [324].…”

Section: Modelling Of Lens Movementmentioning

confidence: 99%

BCLA CLEAR - Evidence-based contact lens practice

Wolffsohn

Dumbleton

Huntjens

et al. 2021

Contact Lens and Anterior Eye

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“…Therefore, the overall sagittal height should be measured at a chord length equal to the overall contact lens diameter, which seems to be useful for initial and customised soft and scleral contact lens selection. 2,[4][5][6] The selection of the optimal rear base curve of a soft contact lens does not correlate with the central keratometry values. While including corneal topography better predicts the fit of a soft contact lens, it is still not reliable enough to enable accurate selection of the first base curve.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9][10][11] Therefore, it is suggested that understanding the overall sagittal height of the anterior eye and the sagittal depth of a soft contact lens will better support the fitting process for soft contact lenses. 4,12 In scleral lens fitting, the sagittal depth of the scleral lens must exceed the sagittal height of the anterior surface at the same chord diameter. 2 To vault the cornea, it has been suggested to estimate the sagittal depth of the first scleral lens in the fitting process by adding a certain amount to the corneal sagittal height data measured at a 10-mm chord using a corneal topographer.…”

Section: Introductionmentioning

confidence: 99%

Prediction of anterior ocular surface sagittal heights using Placido‐based corneal topography in healthy eyes

Bandlitz

Lagodny

Kurz

et al. 2022

Ophthalmic Physiologic Optic

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Purpose To investigate the validity of Placido‐based corneal topography parameters to predict corneoscleral sagittal heights measured by Fourier‐based profilometry at various diameters. Methods Minimal (Minsag), maximal (Maxsag) sagittal height, toricity (Maxsag − Minsag) and axis of the flattest meridian (Minsag) of 36 subjects (mean age 25.4 SD ± 3.2 years; 21 female) were measured using the Eye Surface Profiler and analysed for diameters (chord length) of 8 to 16 mm (in 2‐mm intervals). Furthermore, corneal central radii, corneal astigmatism, eccentricity and diameter were measured using the Keratograph 5 M. Results Using multiple linear regression analysis, the best equation for predicting the sagittal heights for 8 mm (r2 = 0.95), and 10 mm (r2 = 0.93) diameters included corneal central radii and eccentricity. The best equation for predicting sagittal heights for 12 mm (r2 = 0.86), 14 mm (r2 = 0.78) and 16 mm (r2 = 0.65) diameters included corneal central radii, eccentricity and corneal diameter. Corneal astigmatism was significantly correlated with sagittal height toricity for 8 and 10 mm diameters (r2 = 0.50 and 0.29; p < 0.01), while no correlation was observed for 12, 14 and 16 mm diameters (p = 0.18 to p = 0.76). The axis of the flattest corneal meridian measured by Placido‐based topography was significantly correlated with the axis of the flattest meridian measured by Fourier‐based profilometry for 8, 10 and 12 mm diameters (r2 = 0.17 to 0.44; p < 0.05), while there was no correlation for 14 and 16 mm diameters (p = 0.48 and p = 0.75). For a typical soft contact lens diameter of 14 mm, 78% of the variance could be determined with a corneal topographer and 68% with keratometry and corneal diameter measurement. Conclusions The combination of corneal central radii, eccentricity and corneal diameter measured by Placido‐based topography is a valid predictor of the corneoscleral sagittal height in healthy eyes. Scleral toricity and axis of the flattest meridian seem to be independent from Placido‐based corneal parameters and requires additional measuring tools.

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“…The evaluation of 3‐D surface microtexture of CLs at a micro/nano level (Giovanzana, Ţălu, & Nicoară, 2020; Ţălu, 2013; Ţălu, Stępień, & Caglayan, 2015) have been dedicated in last decade based on new modern mathematical tools (Ţălu, 2012b; Ţălu, Bramowicz, Kulesza, Fiorillo, & Giovanzana, 2017; Ţălu & Stach, 2014).…”

Section: Introductionmentioning

confidence: 99%

Advanced morphological analysis of siloxane‐hydrogel contact lenses

Ţălu

2021

Microscopy Res & Technique

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The purpose of this work is to provide a better understanding of three‐dimensional (3‐D) surface texture of siloxane‐hydrogel contact lenses (CLs) using atomic force microscopy (AFM) and stereometric analysis. The 3‐D surface texture characterization of unworn/worn siloxane‐hydrogel CLs made of Filcon V (I FDA group) was performed with stereometric analysis. The atomic force microscopy (AFM) measurements of surface roughness and micromorphology of CLs were made using a Nanoscope V MultiMode (Bruker) in intermittent‐contact mode, in air, on square areas of 5 × 5 μm. Stereometric study of 3‐D surface texture was made according with ISO 25178‐2:2012 for CLrins (taken from the blister and rinsed with deionized water); CLss (preserved for 12 hr in saline solution and rinsed with deionized water); CLworn‐smooth (worn for 8 hr and presenting the smooth type morphology), and CLworn‐sharp (worn for 8 hr and presenting the sharp‐type morphology). The 3‐D surface texture of siloxane‐hydrogel CLs was found to have specific morphological characteristics. Statistical parameters revealed local geometrical and morphological spatial structures at nanometer scale attributed to the specific interactions at the CLs surface. Before wear, the surface micromorphology of Filcon V CLs is regular with uniformly distributed microasperities and relatively small heights (Sq = 0.6 nm). After 12 hr in saline, it is found that the micromorphology changes relatively easily, but retaining the main morphological characteristics (Sq = 1.2 nm). After 8 hr of wear, there are two typical micromorphologies: smooth type, characterized by gutter structures and isolated microasperities (Sq = 2.5 nm), while the sharp type has an appearance with compactly arranged microasperities of hill type flanked by compactly arranged microregions of valley type (Sq = 2.2 nm). Surface statistical parameters allow manufacturers in developing the next generation of CLs with improved surface texture while improving biocompatibility and minimizing the impact of the material on corneal physiology. Furthermore, the micro‐elastohydrodynamic lubrication due to surface texture at a nanometer scale between the back surface of the CL with the corneal surface and the front surface of the CL with the under‐surface of the eyelid can be deeper and more nuanced to understand in light of modern tribological theories.

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Sagittal height differences of disposable soft contact lenses

Cited by 5 publications

References 12 publications

BCLA CLEAR - Evidence-based contact lens practice

BCLA CLEAR - Evidence-based contact lens practice

Prediction of anterior ocular surface sagittal heights using Placido‐based corneal topography in healthy eyes

Advanced morphological analysis of siloxane‐hydrogel contact lenses

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