Correlation between diurnal variation of intraocular pressure, ocular pulse amplitude and corneal structural properties

Villas-Bôas, Flávia Silva; Doi, L. M.; Sousa, A. K.; Melo, Luiz Alberto S.

doi:10.1590/s0004-27492009000300004

Cited by 13 publications

(5 citation statements)

References 23 publications

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“…The area of greatest load-dependent steepening in the preoperative simulation of the eye that developed ectasia emerged near the region where postoperative steepening ultimately manifested clinically. In contrast, the preoperative model of the eye that did not develop post-LASIK ectasia demonstrated mild flattening in response to IOP elevation (consistent with prior studies on IOP dependence in normal eyes 33–35 ). These observations provide early proof of concept for differentiation of case-specific risk and represent an important step toward establishing ranges for normal and abnormal/high-risk strains and stresses in larger, population-based finite element studies.…”

Section: Discussionsupporting

confidence: 83%

Computational Biomechanical Analysis of Asymmetric Ectasia Risk in Unilateral Post-LASIK Ectasia

Vahdati¹,

Seven²,

Mysore³

et al. 2016

J Refract Surg

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Purpose To develop a computational approach to corneal biomechanical risk analysis in refractive surgery and to investigate its utility in an enigmatic case of unilateral ectasia after bilateral LASIK. Methods Preoperative corneal elevation datasets from both eyes of a patient who developed unilateral post-LASIK ectasia were used to construct geometrically patient-specific, microstructurally motivated finite element models. Models were assessed before and after implementation of case-specific treatment parameters for interocular differences in corneal geometry and strain behavior under physiological loading conditions. Results Standard clinical predictors of post-LASIK ectasia risk were similar for the affected and contralateral eyes, and no risk factor asymmetry was identified in tomographic screening that included posterior corneal elevation analysis. However, differences in the magnitude and distribution of strain and stress were observed that are consistent with greater predisposition to biomechanical instability in the affected eye. Load testing with simulated intraocular pressure increases provoked opposite trends in curvature change in the preoperative models representing affected and unaffected eyes, with steepening in the ectatic eye and flattening in the clinically stable eye. Conclusions Patient-specific computational analyses revealed differences in intrinsic biomechanical behaviors that may predispose a cornea to instability after refractive surgery. Strain and stress analyses elucidated differential risk not ascertained with current refractive surgery screening paradigms. This pilot study illustrates a risk analysis approach that implicitly considers the entire corneal three-dimensional geometry and can be performed a priori in a screening setting.

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Section: Discussionsupporting

confidence: 83%

Computational Biomechanical Analysis of Asymmetric Ectasia Risk in Unilateral Post-LASIK Ectasia

Vahdati¹,

Seven²,

Mysore³

et al. 2016

J Refract Surg

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Section: Discussionmentioning

confidence: 99%

“…Previous studies have characterized intra-day diurnal (day-time hours) and circadian (24-hour) CCT variation (measured by ultrasonic pachymetry) in healthy subjects 15-20 as well as in subjects with suspected 21 or established glaucoma. 20 In all of these studies, mean CCT values of the respective samples were compared across time points, precluding evaluation of CCT variation within individuals as reported in the current study. Studies evaluating diurnal CCT variation have reported no significant changes throughout the day in eyes of healthy subjects 18-20 or subjects with suspected glaucoma, 21 but one study revealed a small but significant 12 micron increase in CCT between 0900 and 1700 hours in glaucomatous eyes.…”

Section: Discussionmentioning

confidence: 99%

“…20 In all of these studies, mean CCT values of the respective samples were compared across time points, precluding evaluation of CCT variation within individuals as reported in the current study. Studies evaluating diurnal CCT variation have reported no significant changes throughout the day in eyes of healthy subjects 18-20 or subjects with suspected glaucoma, 21 but one study revealed a small but significant 12 micron increase in CCT between 0900 and 1700 hours in glaucomatous eyes. 20 In contrast, our data demonstrated that both healthy and glaucomatous eyes manifested an average CCT variation of 21 microns over a 12-hour period, with approximately 12% of eyes manifesting a 12-hour CCT variation in excess of 30 microns.…”

Section: Discussionmentioning

confidence: 99%

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Reproducibility of Central Corneal Thickness Measurements in Healthy and Glaucomatous Eyes

Realini

Gurka

Weinreb³

2017

Journal of Glaucoma

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Purpose To characterize intra- and inter-day variation in central corneal thickness (CCT) in healthy and glaucomatous subjects. Methods In this prospective cohort study, 40 healthy subjects and 42 subjects with primary open-angle glaucoma underwent CCT measurements by ultrasonic pachymetry on five days over one year: first at baseline, then at one week and one, six and twelve months after baseline. On one visit, CCT was measured every two hours from 0800 to 2000. Intra-day CCT variance was compared with inter-day CCT variance. Results Mean CCT at all visits and time points ranged from 561-574 microns in healthy eyes and from 548-563 microns in glaucomatous eyes. The mean intra-day CCT range (highest minus lowest readings) was 21 ± 10 microns in healthy participants and 21 ± 10 microns in glaucoma patients. The mean inter-day CCT range was 27 ± 13 microns in healthy participants and 24 ± 14 microns in glaucoma patients. Within-subject variance was significantly larger among the inter-day CCT measurements than the intra-day CCT measurements in both healthy subjects and glaucoma patients (P<0.0001 for both) demonstrating that measurements taken on separate days are more different than measurements taken on the same day. Inter-day CCT differences of 30 microns or greater were seen in 27.7% of normal subjects and 30% of glaucoma patients. Conclusions CCT measurements exhibit intra-day and inter-day variation, with the latter being significantly greater than the former. A single CCT assessment inadequately characterizes CCT and may impact risk assessment in patients with suspect and/or diagnosed glaucoma.

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“…[12] Merenje CCT-a ultrazvučnim pahimetrom pokazalo je značajne varijacije u različitim delovima dana. [13,14,15,16,17] Stoga -smo se trudili, da bi izbegli uticaj unutar dne vne promenjlivosti, da sva merenja budu obavljena u isto doba dana. Kod Kim Y. H. u studiji je bila mala, ali značajna razlika između merenja koje je obavlјalo više osoba (x= 6.9 μm, DISKUSIJA SD= 10.9 μm; p <0.001).…”

Section: Statističke Metodeunclassified

The influence of phacoemulsification on corneal oedema in patients with glaucoma

Bogosavljević¹,

Marjanović²,

Gašić³

et al. 2019

Praxis medica

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Uvod: Dijagnoza glaukoma se bazira na sagledavanju više faktora, kao što su povišen intraokularni pritisak (IOP), oštećenje optičkog diska i specifični defekt odnosno ispad vidnog polјa. Evaluacija integriteta endotela rožnjače i praćenje kornealne debljine je nezaobilazno u toku preoperativne pripreme za fakoemulzifikaciju. Ovi podaci su od velikog značaja za kasniji tretman i praćenje ranih i kasnih postoperativnih komplikacija. Cilj ovog istraživanja je bio da se ustanovi centralna debljina rožnjače neposredno pre i posle operacije katarakte kod pacijenata sa primarnim glaukomom (sa otvorenim i zatvorenim uglom), a upoređujući ih sa pacijentima koji nemaju dijagnostikovan glaukom. Materijal i metode: Prospektivnom studijom obuhvaćeno je ukupno 159 ispitanika kojima je izvršena operacija katarakte metodom fakoemulzifikacije sa implantacijom intraokularnog sočiva u zadnju komoru na Klinici za Očne bolesti, u Kliničkom centru Srbije u Beogradu tokom 2017. i 2018. godine. Pacijenti su u preoperativnoj pripremi razvrstani u dve grupe. Prvu grupu sa primarnim glaukomom činilo je 71 ispitanik, od toga sa glaukomom otvorenog ugla 41, a sa glaukomom zatvorenog ugla 30. Drugu grupu su činili osobe koje nisu imali dijagnostikovan glaukom, njih 88. Centralna debljina rožnjače je merena uz pomoć ultrazvučnog pahimetra. Merenja su bila izvršena pre operacije, 24 časa, 10 i 30 dana nakon operacije, vodeći računa o tome da sva budu obavljena u isto doba dana. Rezultati: Između pacijenata bez glaukoma (BG), primarnog glaukoma otvorenog ugla (POAG) i primarnog glaukoma za-2 tvorenog ugla (PACG), postoji statistički značajna razlika medijana godina starosti (χ = 10,102; DF=2; p=0, 006). Između 2 posmatranih grupa bilo je statistički značajne razlike u vrednostima izmerenih preoperativno (χ = 10,265; DF=2; p=0,006). Između posmatranih grupa nije bilo statistički značajne razlike u vrednostima izmerenih u prvom postoperativnom danu 2 2 (χ = 4,364; DF=2; p=0,099), kao ni u desetom postoperativnom danu (χ = 3,250; DF=2; p=0,197), i 30 dana nakon operacije 2 (χ = 1,427; DF=2; p=0,490). U svakoj od grupa pojedinačno uočena je pojava edema odn. veoma statistički značajna razlika u prvom i desetom postoperativnom danu. Statistički značajna razlika prisutna je i 30 dana nakon operacije, ali daleko manja u odnosu na rani postoperativni period. Zaključak: Na osnovu dobijenih vrednosti u ovoj prospektivnoj studiji, procenjujemo da praćenje kornealne debljine ima obavezno mesto u observaciji pacijenata nakon operacije katarakte. Utvrdili smo da nema razlike u preoperativnom merenju samo između grupa bez glaukoma i glaukoma sa otvorenim uglom. Merenja obavljena u prvom, desetom u tridesetom danu se ne razlikuju po grupama, ali je primećena restitucija edema u tridesetom danu kod svih posmatranih grupa.

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Correlation between diurnal variation of intraocular pressure, ocular pulse amplitude and corneal structural properties

Cited by 13 publications

References 23 publications

Computational Biomechanical Analysis of Asymmetric Ectasia Risk in Unilateral Post-LASIK Ectasia

Computational Biomechanical Analysis of Asymmetric Ectasia Risk in Unilateral Post-LASIK Ectasia

Reproducibility of Central Corneal Thickness Measurements in Healthy and Glaucomatous Eyes

The influence of phacoemulsification on corneal oedema in patients with glaucoma

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