Clinical Evidence of Decreased Iris Resistance in Patients With Keratoconus

Sadoughi, Mohammad Mehdi; Roshandel, Danial; Rezaei, Javad; Einollahi, Neda; Einollahi, Bahram

doi:10.1097/ico.0000000000000878

Cited by 3 publications

(2 citation statements)

References 17 publications

(16 reference statements)

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“…The AC model consisted of the cornea, sclera, lens, iris (consisting of the stroma, sphincter muscle and dilator muscle) and ciliary body. The model, created with SolidWorks (2022, Dassault Systèmes, Vélizy-Villacoublay, France), was designed based on literature values: cornea thickness of 0.50 mm, 14,15 cornea radius of curvature of 7.50 mm, 16 sclera radius of curvature of 12.00 mm 17 and only the anterior lens of radii of 1.4 mm and 5.00 mm (Figure 1A and 1B). The cornea and sclera were combined as a single tissue since the stiffness of the tissues was similar and far greater than the iris (essentially a rigid body).…”

Section: D Modelmentioning

confidence: 99%

Iris Morphological and Biomechanical Factors Influencing Angle Closure During Pupil Dilation

Tan,

Ng,

Tun

et al. 2024

Preprint

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Purpose: To use finite element (FE) analysis to assess what morphological and biomechanical factors of the iris and of the anterior chamber are more likely to influence angle narrowing during pupil dilation. Methods: The study consisted of 1,344 FE models comprising of the cornea, sclera, lens and iris (stroma, sphincter and dilator tissues) to simulate pupil dilation and to assess changes in angle. For each model, we varied the following parameters: anterior chamber depth (ACD = 2-4 mm) and width (ACW = 10-12 mm), iris convexity (IC = 0-0.3 mm), thickness (IT = 0.3-0.5 mm), stiffness (E = 4-24 kPa) and Poisson's ratio (nu = 0-0.3), and simulated pupil dilation. We evaluated for the change in anterior chamber angle (delta f) and the final dilated anterior chamber angles (angle f) from baseline to dilation for each parameter. Results: The final dilated AC angles decreased with a smaller ACD (angle f = 53.4 degrees +/- 12.3 degrees to 21.3 degrees +/- 14.9 degrees), smaller ACW (angle f = 48.2 degrees +/- 13.5 degrees to 26.2 degrees +/- 18.2 degrees), larger IT (angle f = 52.6 degrees +/- 12.3 degrees to 24.4 degrees +/- 15.1 degrees), larger IC (angle f = 45.0 degrees +/- 19.2 degrees to 33.9 degrees +/- 16.5 degrees), larger E (angle f = 40.3 degrees +/- 17.3 degrees to 37.4 degrees +/- 19.2 degrees) and larger nu (angle f = 42.7 degrees +/- 17.7 degrees to 34.2 degrees +/- 18.1 degrees). The change in AC angle increased with larger ACD (Delta angle = 9.37 degrees +/- 11.1 degrees to 15.4 degrees +/- 9.3 degrees), smaller ACW (Delta angle = 7.4 degrees +/- 6.8 degrees to 16.4 degrees +/- 11.5 degrees), larger IT (Delta angle = 5.3 degrees +/- 7.1 degrees to 19.3 degrees +/- 10.2 degrees), smaller IC (Delta angle = 5.4 degrees +/- 8.2 degrees to 19.5 degrees +/- 10.2 degrees), larger E (Delta angle = 10.9 degrees +/- 12.2 degrees to 13.1 degrees +/- 8.8 degrees) and larger nu (Delta angle = 8.1 degrees +/- 9.4 degrees to 16.6 degrees +/- 10.4 degrees). Conclusions: This parametric study offered valuable insights into the factors that could influence angle closure. The morphology of the iris (IT and IC) and its innate biomechanical behavior (E and nu) were crucial in influencing the way the iris deformed during dilation, and angle closure was further exacerbated by decreased AC biometry (ACD and ACW).

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Section: D Modelmentioning

confidence: 99%

Iris Morphological and Biomechanical Factors Influencing Angle Closure During Pupil Dilation

Tan,

Ng,

Tun

et al. 2024

Preprint

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“…Concerning corneal changes, increases in central epithelial thickness, breaks in Bowman's layer, and deformities of Descemet's are prevalent, 5 as well as dramatic changes in collagen fibrils at the apex of the cone 6 were previously described. In addition, many iris abnormalities have been described in keratoconus patients, such as lower tissue resistance during iridotomy, 7 decreases in iris thickness, 8 and iridoschisis. 9 …”

Section: Introductionmentioning

confidence: 99%

Are iris mammillations correlated with keratoconus?

Antunes-Foschini

Costa

Sousa

et al. 2019

American Journal of Ophthalmology Case Reports

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PurposeTo describe the presence of iris mammillations (IM) in keratoconus.DesignRetrospective case series and literature review.ObservationsThis is a retrospective case series of eight patients presenting with keratoconus and IM, who were examined between January 2016 and December 2017 in the ophthalmology outpatient clinic. They had a median age of 14 (11–30), and all had bilateral keratoconus and diffusely distributed IM. The IM had similar presentations and similar iris colors. None had relevant medical or family diseases associated with IM. Three eyes previously had penetrating keratoplasty. Four (31%) out of 13 eyes had mean keratometry (Km) > 55D, and 4 (31%) had the thinnest pachymetry between 300 and 400μm.Conclusions and importanceTo the best of our knowledge, this is the first time that IM was observed in association with keratoconus patients. The possibility that IM is an early finding in otherwise healthy patients may help to predict the future diagnosis of keratoconus. Future studies are needed to show the frequency and possible association between IM and a keratoconus prognosis. This may also demonstrate that there is a subgroup of patients with a distinct etiology of keratoconus.

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Clinical, Demographic, and Tomographic Aspects Related to Iris Mammillations Among Patients With Keratoconus: A Cross-Sectional Study

Antunes-Foschini

Costa

Menezes‐Filho

et al. 2020

Cornea

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Purpose: Iris mammillations (IM) were previously described in patients with keratoconus, but the clinical implications of this finding have never been studied. Our aim was to investigate demographic, tomographic, and clinical characteristics potentially associated with the presence of IM among patients with keratoconus. Methods: This was a cross-sectional study performed among patients with keratoconus in a public-affiliated university hospital. All patients under follow-up were considered eligible to participate in the study. Participants were evaluated by 2 trained ophthalmologists and submitted to corneal tomography (Pentacam). Selected demographic, clinical, and tomographic characteristics were assessed and compared among participants with IM (IM group) and without IM (No-IM group) using the Wilcoxon test or 2-tailed Fisher exact test, as appropriate. Results: The study population consisted of 106 subjects and 19 (17.9%) presented with IM. The median age and interquartile range were 18 years old (14–24) in the IM group and 20 years old (17–24) in the No-IM group (P = 0.135). The female proportion was 47.3% in the IM group and 52.8% in the No-IM group (P = 0.801). Median (interquartile ranges) pachymetric values of the right eyes were 498 (466–525) for the IM group and 459 (421–482) for the No-IM group (P = 0.005). For the left eyes, the values were 490 (456–523) in the IM group and 450 (418–485) in the No-IM group (P = 0.024). Conclusions: Subjects with keratoconus presenting with IM have thicker corneas than those without IM. Follow-up studies should be performed to evaluate the clinical implications of this finding.

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Clinical Evidence of Decreased Iris Resistance in Patients With Keratoconus

Abstract: Lower tissue resistance may be present in other ocular structures, such as iris, in patients with KC. Our findings supported a generalized abnormality in patients with KC rather than a localized corneal disease, at least in some cases.

Cited by 3 publications

References 17 publications

Iris Morphological and Biomechanical Factors Influencing Angle Closure During Pupil Dilation

Iris Morphological and Biomechanical Factors Influencing Angle Closure During Pupil Dilation

Are iris mammillations correlated with keratoconus?

Clinical, Demographic, and Tomographic Aspects Related to Iris Mammillations Among Patients With Keratoconus: A Cross-Sectional Study

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