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Glaucoma
Published in Ching-Yu Cheng, Tien Yin Wong, Ophthalmic Epidemiology, 2022
Zhi Da Soh, Victor Koh, Ching-Yu Cheng
Thinner central corneal thickness (CCT) may increase the risk of glaucoma partly due to under-estimation of IOP measurements.4 In addition, it may act as a biomarker for disease susceptibility, with thinner CCT being observed more in blacks as compared to whites.4
Chronic Hyperglycemia Impairs Vision, Hearing, and Sensory Function
Published in Robert Fried, Richard M. Carlton, Type 2 Diabetes, 2018
Robert Fried, Richard M. Carlton
A study reported in the Journal of Cataract and Refractive Surgery compared diabetic patients and healthy participants. It was found that the mean corneal hysteresis was 9.3 ± 1.4 (SD) mmHg in the control group and 10.7 ± 1.6 mmHg in the patients, and the mean corneal resistance factor was 9.6 ± 1.6 mmHg in the control group and 10.9 ± 1.7 mmHg in the diabetic group. Diabetic corneas were significantly thicker; the mean central corneal thickness was 530.3 ± 35.9 μm in the control group and 548.7 ± 33.0 μm in the diabetic group.
Low-coherence interferometry
Published in Pablo Artal, Handbook of Visual Optics, 2017
LCI biometry achieves a very high precision, both for the axial eye length and the anterior segment. While sub-μm precision can be achieved for central corneal thickness (Drexler et al. 1997b), precision figures on the order of 5–10 μm were reported for the anterior chamber depth, lens thickness, vitreous length, and axial eye length. Table 3.2 compares precision results obtained by repeated LCI and ultrasound measurements in 85 cataract eyes (Drexler et al. 1998b). As can be seen, the precision of LCI is an order of magnitude (or more) better than that of ultrasound biometry. By eliminating residual accommodation using cycloplegia, the precision of anterior chamber depth and lens thickness measurements could be further improved to values below 2 μm in healthy volunteers (Drexler et al. 1997b). In addition to standard biometry, the high precision and resolution of LCI enabled detailed studies of, for example, anterior chamber depth and lens thickness changes during accommodation (Drexler et al. 1997a), eye elongation during accommodation in emmetropes and myopes (Drexler et al. 1998b), and the lens–capsule distance in pseudophakic eyes (Findl et al. 1998).
Clinical Ocular Biomechanics: Where Are We after 20 Years of Progress?
Published in Current Eye Research, 2023
Phillip T. Yuhas, Cynthia J. Roberts
The association between the structural and the biomechanical parameters of the cornea and the incidence of and the progression of glaucoma are well established. Interest in the role that central corneal thickness (CCT) plays in the incidence of glaucoma started in 2002 when the Ocular Hypertension Treatment Study first reported that a thin central cornea is an independent risk factor for the conversion of ocular hypertension to open-angle glaucoma.59 Since then, other groups have replicated the importance of the CCT measurement when assessing an individual’s risk for developing open-angle glaucoma60,61 or risk for progression of preexisting disease.62,63 In contrast, population-based studies on patients from West Africa64 and from East Asia65 have found no difference in CCT between individuals with glaucoma and those without, calling into question the predictive role of CCT in the management of, or in the long-term prognosis of open-angle glaucoma.66 Therefore, it has been proposed that CCT, a structural feature of the eye, may be a proxy for biomechanical parameters that may be more directly related to the pathophysiology of glaucoma.
Effects of Ab Interno XEN Gel Implantation on Postural Intraocular Pressure Elevations
Published in Seminars in Ophthalmology, 2021
Alev Ozcelik Kose, Fehim Esen, Serhat Imamoglu, Nimet Yesim Ercalik, Hatice Tekcan, Suleyman Kugu
Another potential source of bias was that all patients in XEN gel implant group had cataract surgery, while only half of the patients had a history of cataract surgery at the time of examination in the other groups. It has recently been suggested that IOP fluctuations are slightly reduced after phacoemulsification cataract surgery.43 However, the changes induced by the cataract surgery were much smaller compared to the glaucoma surgeries evaluated in this study. We also did subgroup analyses between the pseudophakic patients in all groups to balance the influence of pseudophakia and confirmed that the positional increase in IOP was reduced by Xen gel implant. It is a common practice to evaluate positional IOP values at 5th minute of that subject in that particular position.24,25 There is no data in the literature whether this change persists in the following hours. The persistence of the positional IOP elevations is also an issue that needs to be studied in future studies. This study included only patients that had successful surgeries and successful long-term follow-ups. Because of this strict inclusion criteria, our study was able to evaluate the performance of each surgery without the biases induced by surgical complications. Central corneal thickness influences significantly the IOP measurements with GAT and rebound tonometry.44 Another strength of this study was that the patients in all groups were matched for central corneal thickness (Table 1).
Germany: Longitudinal analysis of intraocular pressure in healthy eyes
Published in Cogent Medicine, 2020
Bettina Hohberger, Marianna Lucio, Christian Y. Mardin, Robert Lämmer
A retrospective analysis of 112 healthy eyes of 112 subjects of the control group of the Erlangen Glaucoma Registry (EGR; ClinicalTrials.gov Identifier: NCT00494923; ISSN 2191-5008, CS-2011 (Hohberger et al., 2017)) was done. The EGR is an observational, longitudinal follow-up study with the aim of research on risk factors for glaucoma disease and glaucoma progression. In addition to glaucoma suspects and glaucoma patients, normal subjects were and are included as control subjects in order to get normal follow-up data. Normal subjects did not show any eye diseases or systemic disorder with ophthalmologic involvement. In a retrospective analysis, the normal subjects of the EGR were analyzed in respect to gender variations over time. As the 112 subjects represent the control group of the EGR, these subjects received the same morphometric and functional tests as glaucoma patients. All subjects underwent a complete ophthalmological examination, including slit-lamp biomicroscopy, funduscopy, papillometry, Spectralis Optical Coherence Tomography (Spectralis® OCT Version 1.9.10.0, Heidelberg Engineering, Heidelberg, Germany) and standard white-on-white full-field perimetry (Octopus 500, G1 protocol, Interzeag, Schlieren, Switzerland), respectively, during each visit. IOP was measured by GAT (Haag Streit, Koeniz, Switzerland, different examiners) in the morning in order to be uninfluential of circadian changes. Central corneal thickness was measured by central ultrasound pachymetry (Pachymeter SP-100, Tomey, Aichi, Japan).