Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Keratoconus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed2006

A new method for grading the severity of keratoconus: the Keratoconus Severity Score (KSS).

PURPOSE: To define a new method for grading severity of keratoconus, the Keratoconus Severity Score (KSS). METHODS: A rationale for grading keratoconus severity was developed using common clinical markers plus 2 corneal topographic indices, creating a 0 to 5 severity score. An initial test set of 1012 eyes, including normal eyes, eyes with abnormal corneal and topographic findings but not keratoconus, and eyes with keratoconus having a wide range of severity, was used to determine cutpoints for the KSS. Validation set 1, comprising data from 128 eyes, was assigned a KSS and compared with a clinician's ranking of severity termed the "gold standard" to determine if the scale fairly represented how a clinician would grade disease severity. kappa statistics, sensitivity, and specificity were calculated. A program was developed to automate the determination of the score. This was tested against a manual assignment of KSS in 2121 (validation set 2) eyes from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study, as well as normal eyes and abnormal eyes without keratoconus. Ten percent of eyes underwent repeat manual assignment of KSS to determine the variability of manual assignment of a score. RESULTS: From initial assessments, the KSS used 2 corneal topography indices: average corneal power and root mean square (RMS) error for higher-order Zernike terms derived from the first corneal surface wavefront. Clinical signs including Vogt striae, Fleischer rings, and corneal scarring were also included. Last, a manual interpretation of the map pattern was included. Validation set 1 yielded a kappa statistic of 0.904, with sensitivities ranging from 0.64 to 1.00 and specificities ranging from 0.93 to 0.98. The sensitivity and specificity for determining nonkeratoconus from keratoconus were both 1.00. Validation set 2 showed kappa statistics of 0.94 and 0.95 for right and left eyes, respectively. Test-retest analysis yielded kappa statistics of 0.84 and 0.83 for right and left eyes, respectively. CONCLUSION: A simple and reliable grading system for keratoconus was developed that can be largely automated. Such a grading scheme could be useful in genetic studies for a complex trait such as keratoconus requiring a quantitative measure of disease presence and severity.

Cornea↗
PubMed2006

The variable expression of keratoconus within monozygotic twins: dundee University Scottish Keratoconus Study (DUSKS).

INTRODUCTION: As part of a longitudinal observational prospective study (Dundee University Scottish Keratoconus Study, DUSKS) a caucasian female subject was identified with keratoconus affecting both corneas. Of interest was that the subject's mother was a monozygotic twin, however, the mother was reportedly unaffected by keratoconus, although her sister (the subject's aunt) had been diagnosed with keratoconus. METHOD: Computer video-keratoscopy (CVK) was undertaken was on this family to clarify this apparent discordance. RESULTS: CVK demonstrated the variable expression of the keratoconic phenotype, by identifying evidence of subclinical keratoconus in the 'unaffected' twin. CONCLUSION: So far only one set of monozygotic twins with keratoconus have been reported within the UK, this paper reports a second. Since CVK has been available the majority agree on concordance of keratoconus expression but not all, including this study. If monozygotic twin studies demonstrate heterogeneity of keratoconus this may at least explain the contradictory data that exists within the literature and why the inheritance pattern of keratoconus is still unclear in 2005.

Corneal Topography↗
PubMed2000

[Use of AutoTopograf TMS-3 keratoconus screening program for keratoconus detection].

PURPOSE: The purpose of this study was to investigate sensitivity of Klyce-Maeda and Smolek-Klyce methods in detection of early or suspect keratoconus by using AutoTopographer TMS-3 (Tomey). MATERIAL AND METHODS: At the First Department and Clinique of Ophthalmology, Silesian Medical School in Katowice, 175 eyes underwent ophthalmological examinations. There were 67 eyes with irregular astigmatism, 39 eyes with PRK decentration and 69 eyes with early or suspected keratoconus. The procedure was performed with the TMS-3 AutoTopographer (Tomey). During the study we investigated index definitions included in Keratoconus Screening Program. RESULTS: The examination showed the false positive results: in irregular astigmatism (KSI index in 31.3%, KPI index in 10.4%), in PRK decentration (KSI and KPS index in 18%). The results of analysis of keratoconus detection by Keratoconus Screening Program in early or suspected keratoconus were false negative (it means there were no keratoconus symptoms) in KCI index--24.6%, in KSI index--11.6% and KPI index--21.7%. CONCLUSION: To sum up, we can say that Keratoconus Screening Program is a good program for confirming diagnosis of early keratoconus in 80%, but it has to be assisted by a clinical examination.

Astigmatism↗
PubMed1997

[Quantitative topographic detection of keratoconus in the contralateral eye in clinically unilateral keratoconus. Apropos of 5 cases].

BACKGROUND: Keratoconus is generally bilateral and follows an asymmetrical course. The goal of this study was to evaluate efficiency of the automated topographic screening indices on early keratoconus by examination of the fellow eyes of clinically unilateral keratoconus. PATIENTS AND METHOD: We examined the fellow eyes of 5 cases of clinically unilateral keratoconus by videokeratography using TMS-1 Computed Anatomy device, which incorporates the keratoconus screening indices from Rabinowitz (K and I-S values) and Klyce/Maeda (KPI value and other quantitative induces as OSI, DSI and CSI). RESULTS: One case (number 1) had keratoconus detected by both Rabinowitz and Klyce/Maeda indices. Two cases (number 2 and 3) had normal keratoconus screening indices. Two cases (number 4 and 5) had keratoconus detected by Rabinowitz I-S value, with a 0% KPI value. CONCLUSIONS: Rabinowitz indices are sensitive with a poor specificity. The Klyce/Maeda indices are less sensitive but more specific. Both methods may be useful for keratoconus detection. The results must always be analysed in relation to a clinical observation of both eyes and the course of the topographic changes.

Adult↗
PubMed2004

[Accuracy of videokeratographic quantitative criteria for detection of keratoconus suspects in families with keratoconus].

AIM: We statistically assessed the videokeratographic data obtained from families with keratoconus in order to determine reliable criteria for detecting keratoconus suspects. MATERIAL AND METHODS: Fourteen keratoconus patients from 12 families were enlisted. We investigated 55 relatives (110 eyes). Standard videokeratographic data were obtained by screening 30 individuals (60 eyes) with clinically normal eyes, with no history of ocular disorders, contact lens wear, or keratoconus individuals in their family. Videokeratographic qualitative and quantitative analyses were performed on every subject. The videokeratographic threshold values obtained from the control group were used as a reference. RESULTS: Two criteria based on the Klyce/Maeda indices proved their statistical significance in detecting keratoconus suspects. When considering the significant criteria ascertained by the statistical analysis, building pedigrees favored the autosomal dominant mode of inheritance. Two of the pedigrees corresponded to either a recessive mode of transmission or the potential occurrence of a de novo mutation. CONCLUSION: We have determined videokeratographic criteria of statistical significance for detecting keratoconus suspects. The knowledge of the status of each member of families with keratoconus is a prerequisite to performing genetic linkage analyses, which may allow a precise locus linked with this disorder to be refined.

Adolescent↗
PubMed1993

[Fibrocyte reaction to interleukin 1 stimulation in keratoconus. Original title: Fibrocyte response to interleukin 1 stimulation in keratoconus].

BACKGROUND: The reduced mechanical strength of the tissues around a keratoconus and the ultrastructural disorganization of its matrix components are caused by proteolytic breakdown and incomplete repair. In most biochemical studies on this subject, reduced collagen content and increased collagenase and gelatinase activity have been reported. METHODS: Since interleukin-1 (IL-1) promotes secretion of prostaglandin E-2 (PG-E2 and collagenase, we were interested in the number of membrane receptors for these cytokines on keratoconus fibroblasts and determined the corresponding dissociation constant (kD). We also studied the kinetics of cyclo-oxygenase and the synthesis of PG-E2, IL-1 and collagen. We compared the data with data from normal human corneas. RESULTS: 1) There was a significant difference (P < 0.05) between the specific binding of [125I]-IL-1 in keratoconic and normal corneal cells. In keratoconus, the number of receptors was four times higher (7000 +/- 100 binding sites per cell) than in normal corneas (1540 +/- 100 binding sites per cell). However, there was little difference between the dissociation constants for keratoconic ([6.21 +/- 0.5] x 10(-11) and normal ([6.27 +/- 0.5] x 10(-11) corneal cells. 2) Under the study conditions, interleukin-1 was found neither in normal nor in keratoconic cornea. 3) Synthesis of PG-E2 without stimulation of cells by IL-1, which was observed in 8 corneas with and 8 without keratoconus, showed that keratoconus cells secrete ten times more PG-E2 than normal corneals cells. If IL-1 is added to the incubation medium, which contains [3H]-labeled arachidonic acid, PG-E2 synthesis increases more than in normal corneal cells. 4) After adding IL-1, the collagen concentration in keratoconus cells in culture was more pronounced than in normal corneal cells. CONCLUSIONS: It is still not known why the anomalies discussed above occur in keratoconus. The increase in IL-1 receptor expression and the high level of cyclooxygenase activity are very probably due to genetic causes, because they are observed even after 40 generations of cell cultures.

Cells, Cultured↗
PubMed1996

Biomicroscopic signs and disease severity in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group.

The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Survey represents the largest sample of clinic-based keratoconus patients to date. Data were collected at 38 clinical centers on 1,579 keratoconus patients. This article reports demographic variable, ages, self-reported ages at diagnosis, keratometry, slit-lamp findings, systemic disease, family history of keratoconus, and best spectacle-corrected and contact lens-corrected visual acuity of this sample group. The average age of this clinic-based sample group was 37 years (range 10-89 years), with 84% between 20 and 49 years old. Thirteen percent of patients had unilateral keratoconus, defined as unilateral corneal irregularity. More advanced disease (steeper average keratometric reading) was associated with a greater likelihood of Vogt's striae, Fleischer's ring, and/or corneal scarring. Fifty-eight percent of the eyes in this group of patients had > or = 20/40 visual acuity with manifest refraction. Penetrating keratoplasty was reported in 12.3% of eyes. This prospective survey identifies the associates between the presence of Vogt's striae, Fleischer's ring, and/or corneal scarring and increasing steepness, as measured by keratometry.

Adolescent↗
PubMed1998

Repeatability and agreement of two corneal-curvature assessments in keratoconus: keratometry and the first definite apical clearance lens (FDACL). CLEK Study Group. Collaborative Longitudinal Evaluation of Keratoconus.

PURPOSE: This study was conducted to determine the agreement and test-retest repeatability of two methods for measuring corneal curvature in keratoconus: keratometry and the First Definite Apical Clearance Lens (FDACL). Our interest in the FDACL procedure stems from the important contact lens-fitting information and documentation of disease progression provided by the FDACL trial lenses and observation of fluorescein patterns. METHODS: The Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is an observational study that has enrolled 1,209 keratoconus patients to characterize the progression of keratoconus, to determine factors associated with its progression, and to assess its impact on quality of life. Ten percent of the patients were randomly selected at baseline for a retest examination. The baseline examination, which included keratometry and FDACL, was repeated in this sample. The FDACL is the flattest lens in the standardized CLEK trial lens set that vaults the apex of the cone. FDACL provides an estimate of the sagittal height of the cone. RESULTS: The correlation of FDACL with the steep keratometric reading (r = 0.89; p = 0.0001) and the flat keratometric reading (r = 0.83; p = 0.0001) were high. Test-retest repeatability as measured by the intraclass correlation coefficient (ICC) was high: FDACL ICC, 0.97; steep keratometric reading ICC, 0.96; and flat keratometric reading ICC, 0.95. Test-retest repeatability of FDACL remained high in advanced disease. CONCLUSION: FDACL provides a repeatable new procedure for determining disease severity in keratoconus.

Adult↗
PubMed2000

Corneal scarring and vision in keratoconus: a baseline report from the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study.

PURPOSE: The multicenter Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study is a prospective, observational study of 1,209 keratoconus patients. We report on the correlation of corneal scarring with clinical and patient-reported variables at the baseline visit. METHODS: Patients completed a questionnaire on their vision, effect of glare, contact lens wear, and work-related issues. Clinical examination included high- and low-contrast visual acuity, refraction, assessment of corneal scarring by the clinician and by photography, and measurement of corneal curvature. The correlation of central corneal scarring with visual acuity and patient-reported variables was analyzed using multiple regression analysis and generalized estimating equations. RESULTS: High- and low-contrast visual acuity with habitual and optimal correction is reduced in scarred eyes. Multiple regression analyses controlling for age, contact lens wear, and disease severity show that central scarring is associated with poorer visual acuity and increased patient-reported symptoms of glare. Restrictions on day-to-day activities do not appear to be associated with corneal scarring above and beyond the effects of keratoconus alone. CONCLUSIONS: Corneal scarring in keratoconus is significantly associated with decreased high- and low-contrast visual acuity.

Cicatrix↗
PubMed1998

Visual acuity repeatability in keratoconus: impact on sample size. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group.

PURPOSE: The purpose of this paper is to determine the repeatability of visual acuity measurement in keratoconus and to describe the impact of measurement repeatability on sample size. METHODS: Approximately 10% of a 1209 patient sample in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study were selected randomly for a Repeat CLEK Study Visit. Patients were tested at the 15 CLEK Participating Clinics. The test-retest sample consisted of 1 34 keratoconus patients who met the entry criteria of the CLEK Study. High and low contrast Bailey-Lovie visual acuity was measured with the patient's habitual visual correction (entrance visual acuity monocularly and binocularly), and with the best correction monocularly (either the patient's rigid contact lens and over-refraction, or with a CLEK Study trial lens and appropriate over-refraction) at two visits separated by a median of 90 days (range 22 to 268 days). RESULTS: The mean absolute differences between the number of letters correct at the two visits ranged from a low of 3.24 +/- 3.1 for entrance high contrast binocular acuity to a high of 5.48 +/- 5.1 for best corrected low contrast monocular acuity. Intraclass correlation coefficients ranged from 0.757 to 0.853. The visual acuity score was somewhat higher at the Repeat Visit than at the Baseline Visit when the examiners were different between visits. CONCLUSIONS: Given the variable vision reported by keratoconus patients, visual acuity in this sample was very repeatable. Repeatability was slightly poorer when different examiners tested visual acuity at the Baseline and Repeat Visits.

Adolescent↗
PubMed2003

Bilateral keratoconus after LASIK in a keratoconus patient.

PURPOSE: To describe a case of bilateral keratoconus occurring after LASIK in a keratoconus suspect. METHOD: Case report. RESULTS: A 33-year-old male presented to our institution for evaluation of poor vision 4 years after undergoing bilateral LASIK for the treatment of compound myopic astigmatism. Corneal topography examination showed marked bilateral inferior steepening, and a slitlamp examination revealed classic signs of keratoconus. A review of his preoperative corneal topography showed bilateral inferior steepening, but no other clinical signs of keratoconus were noted at the time of the operation. CONCLUSIONS: A finding of inferior steepening on corneal topography examination should be regarded as a contraindication to the LASIK procedure.

Adult↗
PubMed1999

Rigid contact lens fitting relationships in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group.

PURPOSE: Although the influence of flat-fitting contact lenses on corneal scarring in keratoconus is frequently debated, the current standard of care with regard to the apical fitting relationship in keratoconus remains undocumented. METHODS: Patients were examined at baseline in the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study (N = 1209). Patients wearing a rigid contact lens in one or both eyes (N = 808) had their habitual rigid contact lenses analyzed, and the fluorescein patterns and base curves were compared to the first definite apical clearance lens (FDACL). The FDACL is the flattest lens in the CLEK Study trial lens set that exhibits an apical clearance fluorescein pattern. For patients wearing a rigid contact lens in both eyes, one eye was selected randomly for analysis. RESULTS: Twelve percent of the rigid contact lens-wearing eyes were wearing lenses fitted with apical clearance based upon the clinician's fluorescein pattern interpretation. The remainder (88%) was wearing lenses fitted with apical touch. For mild (steep keratometric reading <45 D) keratoconus corneas, the mean estimate of the base curve to cornea-fitting relationship was 1.18 D flat (SD +/- 1.84 D); moderate (steep keratometric reading: 45 to 52 D) corneas were fitted on average 2.38 D flat (SD +/- 2.56 D); and severe (steep keratometric reading > 52 D) corneas were fitted an average of 4.01 D flat (SD +/- 4.11 D). CONCLUSIONS: Despite the potential risk for corneal scarring imposed by flat-fitting rigid contact lenses, most CLEK Study patients wear flat-fitting lenses. Overall, rigid lenses were fitted an average of 2.86 D (SD +/- 3.31 D) flatter than the FDACL.

Contact Lenses↗
PubMed1988

Keratoconus. Evaluation of recent trends in the surgical and nonsurgical correction of keratoconus.

Recent focus on the optical correction for "contact lens failure" keratoconus patients has been in the use of epikeratoplasty as an alternative to penetrating keratoplasty. In a 2-year retrospective review of keratoconus patients, 33 were referred as "contact lens failures" and as such might be considered candidates for surgical intervention. Of these, 29 patients (average keratometry, 50.4; range, 43-73) were successfully refitted with contact lenses. All patients obtained wearing times of 12 hours and achieved a visual acuity of 20/40 or better, with 85% realizing 20/30 or better. The data suggest that with concerted effort most keratoconus patients may be successfully refitted despite initial contact lens failure.

Adolescent↗
PubMed1975

Keratoconus and the Ehlers-Danlos syndrome: a new aspect of keratoconus.

Hypermobility of the joints is a frequent finding in patients who have keratoconus. Twenty-two of 44 patients (50%) presenting in 1973 were found to have hypermobility of joints (mainly Ehlers-Danlos syndrome II or mitis type). The significance of this finding is discussed in relation to biochemical defects recently found in corneas with keratoconus. The hypothesis is presented that keratoconus is often a part of a generalized heritable disorder of connective tissue due to a biochemical defect causing a weakness in its structure.

Adolescent↗
PubMed1998

Repeatability of refraction and corrected visual acuity in keratoconus. The CLEK Study Group. Collaborative Longitudinal Evaluation of Keratoconus.

PURPOSE: The purpose of the test-retest phase of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study was to determine the repeatability of the various parts of the CLEK Study protocol. This paper presents the test-retest parameters of the refraction protocol. METHODS: We examined 138 CLEK Study-eligible patients on two occasions (median, 90 days; range, 22 to 268 days). All patients underwent subjective refraction on two occasions, and contact lens over-refractions were performed either over the patient's habitual rigid contact lenses or over a trial rigid contact lens equal in base curve to the steep keratometric reading in nonrigid contact lens wearers. RESULTS: Mean interoccasion differences +/- SD were -0.32 +/- 2.91 D and -0.17 +/- 1.39 D for subjective refraction sphere and cylinder power, respectively, and the mean absolute difference for subjective refraction cylinder axis was 18.1 +/- 20.2 degrees. The mean interoccasion difference +/- SD for high-contrast visual acuity with subjective refraction was 0.38 +/- 10.9 letters correct. Mean interoccasion differences +/- SD were -0.11 +/- 0.81 D and 0.02 +/- 0.67 D for contact lens over-refraction sphere and cylinder power, respectively, and the mean absolute difference for contact lens over-refraction cylinder axis was 11.6 +/- 9.9 degrees. The mean interoccasion difference +/- SD for visual acuity with contact lens over-refraction was 0.50 +/- 5.2 letters correct and 0.71 +/- 6.9 letters correct for high- and low-contrast visual acuity, respectively. CONCLUSIONS: The repeatability of subjective refraction in keratoconus patients is good but somewhat lower than that found in nondiseased eyes. Only 36% of our repeat measures of sphere power from subjective refraction fell within 0.50 D of each other, compared with more than 90% in studies of normal eyes.

Adult↗