Dataset Information

The relation between disease asymmetry and severity in keratoconus.

ABSTRACT:

Background/aim

Keratoconus is described as a bilateral, asymmetric, non-inflammatory corneal ectasia. The purpose of the study was to examine the relation between disease asymmetry and severity in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study cohort.

Methods

Analyses included 1037 keratoconus patients from the CLEK Study baseline examination visit, none of whom had undergone corneal surgery in either eye. Disease asymmetry was determined by taking the difference between eyes for continuous variables. For categorical variables, asymmetry was categorised by whether the variable was present in neither, one, or both eyes. Disease severity was defined using the first definite apical clearance lens (FDACL) technique (a rigid contact lens to measure corneal curvature) from the worse (steeper) eye. Statistical analyses included Pearson's correlation coefficients (continuous variables) and analysis of variance (categorical variables).

Results

There were generally weak correlations between asymmetry and severity for low contrast habitual visual acuity (r = 0.12, p = 0.0003), high contrast habitual visual acuity (r = 0.14, p<0.0001), low contrast best corrected visual acuity (r = 0.21, p<0.0001), and high contrast best corrected visual acuity (r = 0.29, p<0.0001). Asymmetry in refractive error was more moderately correlated with disease severity (r = 0.41, p<0.0001), as was asymmetry in the flat (r = 0.61, p<0.0001) and steep keratometric readings (r = 0.54, p<0.0001). The average FDACL was significantly steeper in patients who had one eye with Vogt's striae, Fleischer's ring, or corneal scarring compared with the average FDACL when neither eye had these findings.

Conclusion

Keratoconus patients with more severe disease are also more asymmetric in their disease status.

SUBMITTER: Nichols JJ

PROVIDER: S-EPMC1772171 | biostudies-literature | 2004 Jun

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The relation between disease asymmetry and severity in keratoconus.

Nichols J J JJ Steger-May K K Edrington T B TB Zadnik K K

The British journal of ophthalmology 20040601 6

<h4>Background/aim</h4>Keratoconus is described as a bilateral, asymmetric, non-inflammatory corneal ectasia. The purpose of the study was to examine the relation between disease asymmetry and severity in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study cohort.<h4>Methods</h4>Analyses included 1037 keratoconus patients from the CLEK Study baseline examination visit, none of whom had undergone corneal surgery in either eye. Disease asymmetry was determined by taking the diffe ...[more]

PMID: 15148213

Similar Datasets

Project description:BACKGROUND:Progressive keratoconus can lead to severely impaired vision, but there is currently no consensus on the definition of progressive disease. Errors in the measurement of the parameters commonly used to establish progressive disease were evaluated in an attempt to determine the limits at which a true change in the values can be detected. The possible association between measurement error and disease severity was also investigated to evaluate the need for limits based on disease severity. METHODS:Sixty-one eyes were studied in 61 patients with keratoconus. Four replicate measurements were made in each patient using a Scheimpflug-based tomographic system (denoted the PC) and an auto-keratometer (denoted the AK). The repeatability coefficient, i.e., the level below which differences between two measurements are found in 95% of paired observations, was calculated. Patients were further divided into three groups based on disease severity (parameter magnitude). RESULTS:Increasing magnitude of all the keratometric parameters investigated was significantly associated with increasing measurement errors, and thus worse repeatability. The maximum keratometry value (Kmax) was the least repeatable parameter (1.23 D, 95% CI 1.11-1.35 D) and showed the strongest association between parameter magnitude and measurement error. The repeatability coefficient ranged between 0.32 and 1.62 D, depending on disease severity. The most repeatable parameter was the flattest central keratometry value (K1), measured with the PC (0.51 D, 95% CI 0.46-0.56 D) and the AK (0.54 D, 95% CI 0.48-0.59 D). K1 showed the weakest association between parameter magnitude and measurement error. The repeatability coefficient for K1 ranged between 0.40 and 0.54 D when using the PC, and between 0.34 and 0.70 D when using the AK in the three groups. CONCLUSIONS:The association between the magnitude of the keratometric parameters and their measurement errors suggests that limits should be based on disease severity to ensure reliable detection of progressive keratoconus. Further studies are, however, required.

Project description:ObjectiveThe study aimed to evaluate the character of corneal stiffness parameter at the first applanation (SP-A1) in normal and keratoconus eyes and explore the association between SP-A1 and keratoconus severity indicators.MethodsA total of 351 normal and 351 keratoconus eyes were included in the current study. Keratoconus was diagnosed according to the corneal topography map and slit-lamp examination. The severity of keratoconus was classified to mild (steep keratometry (Ks) < 48D), moderate (48 ≤ Ks < 55D), and severe (Ks ≥ 55D). The SP-A1 was measured using the Corvis ST software. The correlation analyses and receiver operating characteristic (ROC) curve were performed in the current analysis.ResultsThe SP-A1 values of keratoconus were lower than that of normal eyes (72.11 (57.02, 83.08) mmHg/mm vs 110.89 (100.45, 122.47) mmHg/mm, P < 0.001). With the severity of keratoconus increasing, the SP-A1 decreased and the value of SP-A1 was 79.54 (70.30, 90.93) mmHg/mm, 65.11 (53.14, 77.46) mmHg/mm, and 47.59 (37.50, 62.14) mmHg/mm in mild, moderate, and severe keratoconus eyes, respectively (P < 0.001). The negative association between SP-A1 and Ks was found in mild, moderate, and severe keratoconus eyes (r mild = -0.171, r moderate = -0.317, r severe = -0.288, all P < 0.05). A positive association between SP-A1 and the thinnest corneal thickness (TCT) was found in all eyes (rnormal = 0.687, r mild = 0.519, r moderate = 0.488, r severe = 0.382, all P < 0.05). SP-A1 was found to be statistically positively associated with intraocular pressure (IOP), biomechanical corrected IOP (bIOP), time from the initiation of air puff until the first applanation (A1T), corneal velocity at the second applanation (A2V), and negatively associated with deformation amplitude (DA), peak distance (PD), corneal velocity at the first applanation (A1V), time from the initiation of air puff until the second applanation (A2T), and DA Ratio Max [2 mm] both in normal and keratoconus eyes (all P < 0.05). The ROC analysis indicated that the AUC (95% CI) of SP-A1 was 0.952 (0.934-0.967) and 0.930 (0.904-0.951) in detecting keratoconus eyes and mild keratoconus eyes from normal eyes, respectively.ConclusionsThe SP-A1 value decreased while the keratoconus severity increased. It was lower in keratoconus than that in normal eyes and could be helpful in identifying keratoconus eyes from normal eyes. Further researches would be warranted to expand the clinical utility of SP-A1.

Project description:PurposeKeratoconus (KC) is characterized by progressive vision loss due to corneal thinning and structural abnormalities. It is hypothesized that KC is caused by deregulated collagen levels and collagen fibril-maturating enzyme lysyl oxidase (LOX). Further, it is currently not understood whether the gene expression deregulated by the corneal epithelium influences KC pathogenesis. We studied (i) the expressions of the LOX, collagen I (COL IA1), collagen IV (COL IVA1), MMP9, and IL6 genes in KC corneal epithelia, (ii) validated their expression levels in patient tissues, and (iii) correlated expression levels with KC disease severity. The primary goal of this study was to evaluate the importance of these genes in the progression of KC.MethodsWe analyzed the gene expression levels of the key proteins LOX, collagens (COL IA1 and COL IVA1), MMP9, and IL6 in debrided corneal epithelia from a large cohort of KC patients (90 eyes) and compared them to control patients (52 eyes) without KC. We measured the total LOX activity in the tears of KC patients compared to controls. We also correlated the protein expression levels of LOX and collagens by immunohistochemistry (IHC) in primary tissues from KC patients (27 eyes) undergoing keratoplasty compared to healthy donor corneas (15 eyes).ResultsWe observed a significant reduction in LOX transcript levels in KC corneal epithelia, and LOX activity in KC tears correlated with disease severity. Collagen transcripts were also reduced in KC while MMP9 transcript levels were upregulated and correlated with disease severity. IL6 was moderately increased in KC patients. IHC demonstrated a reduction in the protein expression levels of LOX in the epithelium and collagen IV in the basement membrane of KC patients compared to healthy donor corneas.ConclusionsThe data demonstrates that the structural deformity of the KC cornea may be dependent on reduced expressions of collagens and LOX, as well as on MMP9 elevated by the corneal epithelium.

Dataset Information

The relation between disease asymmetry and severity in keratoconus.

Background/aim

Methods

Results

Conclusion

Publications

The relation between disease asymmetry and severity in keratoconus.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets