The Biomechanics of Keratoconus and Rigid Contact Lenses

McMonnies, Charles W.

doi:10.1097/01.icl.0000146321.56815.75

Cited by 47 publications

(38 citation statements)

References 79 publications

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“…Of course, pathologic thinning of the cornea is known to be associated with corneal shape change with increases in IOP. 23 However, as discussed later, healthy corneas appear to be stabilized against significant changes by stress-stiffening mechanisms. Diurnal variations in corneal tissue elasticity suggest that for intrasubject comparisons, it is important to take measurements at approximately the same time of day.…”

Section: Corneal Thickness Differences Between Subjectsmentioning

confidence: 97%

“…26 It is possible that these effects would be greater for eyes with corneas thinned by refractive surgery 26 or thinning diseases. 23,27 The phasing of diurnal IOP changes is prolonged for several hours and provides a steady state of distending force and a greater chance of response to low IOP increments. Global expansion may be expected to correspond with morning peaks of IOP.…”

Section: The Interaction Between Scleral and Corneal Responses To Intmentioning

confidence: 99%

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Corneal Curvature Stability With Increased Intraocular Pressure

McMonnies

Boneham

2007

Eye &Amp; Contact Lens: Science &Amp; Clinical Practice

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Corneal shape and refraction were found to show only minor evidence of instability under conditions of IOP loading. The small number and minor degree of corneal changes recorded under IOP loading suggest that under these conditions of measurement, corneal stability may be the result of stress stiffening. However, mechanisms for corneal shape changes that depend on limbal and scleral rigidity may also contribute to corneal shape stability.

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Section: Corneal Thickness Differences Between Subjectsmentioning

confidence: 97%

Section: The Interaction Between Scleral and Corneal Responses To Intmentioning

confidence: 99%

Corneal Curvature Stability With Increased Intraocular Pressure

McMonnies

Boneham

2007

Eye &Amp; Contact Lens: Science &Amp; Clinical Practice

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“…It has been reported in the literature that progression of keratoconus is related to age and microtraumas, but not related to gender, laterality or familial history. 6,7,28 There have been differences in the criteria used to determine the progression of keratoconus in the literature. O'Brart et al recommended crosslinking therapy when there was a one-unit regression in corrected and uncorrected visual acuity, an increase in refractive and corneal astigmatism and an increase in keratometry and conical apex strength by 0.75D in 12-24 months.…”

Section: Discussionmentioning

confidence: 99%

“…[1][2][3][4][5] Microtraumas which cause chronic irritation like using rigid contact lenses and rubbing eyes are the most important predisposing factors leading to progression of the disease. 6,7 As keratoconus progresses, the corneal stroma becomes thinner and the cornea changes into a more conical shape. The resultant irregular astigmatism and high myopia reduce vision.…”

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confidence: 99%

Progression of Keratoconus in Turkish Adult Patients

Novruzlu¹,

Yüksel²,

Bi̇lgi̇han³

2016

Turkiye Klinikleri J Ophthalmol

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A AB BS S T TR RA AC CT T O Ob bj je ec ct ti iv ve e: : To evaluate progression of keratoconus in adult patients diagnosed as keratoconus and to compare it with the disease progression in pediatric patients reported in the literature. M Ma at te er ri ia al l a an nd d M Me et th ho od ds s: : Five hundred and forty-seven patients diagnosed as keratoconus were reviewed retrospectively and 143 eyes of 106 adult patients were included into the study. The patients were assigned into two groups: Group I was aged 18-24 years and Group II was aged over 24 years. Data about age, best corrected visual acuity (BCVA) with glasses, spherical equivalents (SE), corneal thickness, simulated mean kerotometry (SimK) and follow-up periods were collected. The patients having progression in keratoconus were recommended a treatment with corneal collagen cross-linking. R Re es su ul lt ts s: : The mean age of the patients was 21.34±1.75 years and 30.26±5.10 years in Group I and Group II respectively. The mean follow-up period was 11.96±7.24 months in Group I and 15.44±12.6 months in Group II. The rate of the progression was 25.6% and 23.1% in Group I and Group II respectively, though there was not a significant difference (p=0.549). The rate of the progression was 24.4% in the adults recently diagnosed as keratoconus at the end of a mean follow-up period of 12.74±10.60 months. C Co on nc cl lu us si io on n: : About one fourth of the adult patients required cross-linking therapy during a one-year follow-up and 75% of the adult patients with keratoconus did not have disease progression at the end of a one-year follow-up. Before adults recently diagnosed as keratoconus are advised to have cross-linking therapy, they should be given an anti-allergic treatment and followed for the disease progression.K Ke ey y W Wo or rd ds s: : Keratoconus; corneal surgery, laser Ö ÖZ ZE ET T A Am ma aç ç: : Keratokonus tanısı konulan erişkin hastalarda keratokonus progresyonunu değerlen-dirmek ve literatürde bildirilen çocuk hastalarla karşılaştırmak. G Ge er re eç ç v ve e Y Yö ön nt te em ml le er r: : Keratokonus tanısı alan 547 hasta retrospektif olarak incelendi, 106 hastanın 143 gözü çalışmaya dahil edildi. Çalışmada hastalar iki gruba ayrıldı. 1. grup 18-24 yaş, 2. grup 24 yaş üzeri olacak şekilde oluştu-ruldu. Hastaların dosyalarından, yaş, gözlükle en iyi görme keskinliği (EİDGK), sferik eşdeğer (SE), korneal kalınlık, ortalama simüle keratometri (SimK) ve takip süreleri not edildi. Keratokonusta progresyon görülen hastalara korneal çapraz bağlama tedavisi yapıldı. B Bu ul lg gu ul la ar r: : Hastaların ortalama yaşı, Grup 1 ve Grup 2'de sırasıyla 21,34±1,75 yıl ve 30,26±5,10 yıl idi. Grup 1'de takip süresi 11,96±7,24 ay, Grup 2'de 12,74±10,60 ay idi. Progresyon oranı, Grup 1 ve Grup 2'de sırasıyla %25,6 ve %23,1 idi (p=0,549). Erişkinlerde ortalama 12,74±10,60 ay sonunda progresyon oranı %24,4 idi. S So on nu uç ç: : Ortalama 1 yıl sonunda tüm erişkinlerin 1/4'ünde korneal çapraz-bağlama tedavisi ihtiyacı olmaktadır ve 3/4'ünde keratakonus ...

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“…HKCFBs were seeded at 6-well Bioflex ® plates (Flexcell Int. Corp., Hillsborough, NC, USA) with an initial density of 5x10 5 /well. When the cultured cells became confluent, the cells were serum starved using DMEM/F12 with 0.1% FBS for 24 h. After 24 h, the media was replaced with FBS-free media (DMEM/F12) and treated with IL-6 (R&D Systems, Minneapolis, MN, USA) at a final concentration of 0, 12.5, 25 or 50 ng/ml.…”

Section: Methodsmentioning

confidence: 99%

Induction of MMP-1 and −3 by cyclical mechanical stretch is mediated by IL-6 in cultured fibroblasts of keratoconus

Du¹,

Chen²,

Li³

et al. 2017

Molecular Medicine Reports

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Abstract. In order to understand the effect of mechanical stretch on corneal extracellular matrix remodeling, human keratoconus fibroblasts (HKCFBs) were subjected to cyclic stretch in vitro and the expression of matrix metalloproteinases (MMPs), tissue inhibitor of metalloproteinases (TIMPs), and inflammatory cytokines were evaluated. HKCFBs were seeded into a flexible membrane base and subjected to a cyclic stretch regimen of 10% equibiaxial stretch at a stretching frequency of 1 Hz for 6 h using a Flexcell tension unit. An antibody directed against interleukin-6 (IL-6 Ab) was used to investigate the roles of IL-6 on mechanical stretch mediated regulation of MMP in HKCFBs. Culture supernatants were assayed using an enzyme-linked immunosorbent assay for MMP-1 and -3, TIMP-1 and -2, and IL-6. Total RNA from the cells was extracted, and quantitative polymerase chain reaction was used to determine mRNA for MMP-1 and -3, TIMP-1 and -2, and IL-6. In stretched cells, levels of MMP-1 and -3 demonstrated an increase compared with unstretched cells, but levels of TIMP-1, and -2 revealed a decrease. Mechanical stretch significantly increased the mRNA expression and protein synthesis of IL-6 compared with unstretched cells. IL-6 induced MMP-1 and -3 expression, whereas no significant effects were observed in levels of TIMP-1 and -2 compared with the untreated control groups. Additionally, the IL-6 Ab markedly inhibited the stretch-induced increase in MMP-1 and -3 in culture supernatants in a dose-dependent manner. No significant differences in TIMP-1 and -2 protein levels were detected between stretched cells treated with IL-6 Ab and stretched cells without IL-6 Ab treatment. These results indicate that cyclical mechanical stretch augments IL-6 production and MMP expression, and reduces levels of TIMP in HKCFBs. Thus, it is suggested that IL-6 mediates the stretch-induced MMP expression.

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The Biomechanics of Keratoconus and Rigid Contact Lenses

Cited by 47 publications

References 79 publications

Corneal Curvature Stability With Increased Intraocular Pressure

Corneal Curvature Stability With Increased Intraocular Pressure

Progression of Keratoconus in Turkish Adult Patients

Induction of MMP-1 and −3 by cyclical mechanical stretch is mediated by IL-6 in cultured fibroblasts of keratoconus

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