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PubMed2001

Incidence of keratoconus in subjects with vernal keratoconjunctivitis: a videokeratographic study.

PURPOSE: To detect the incidence of keratoconus by videography in patients with vernal keratoconjunctivitis (VKC) and to evaluate the clinical characteristics of VKC associated with keratoconus. DESIGN: a prospective, cross-sectional (prevalence) study. PARTICIPANTS: Eighty-two consecutive subjects with the diagnosis of VKC. METHODS: Both eyes of VKC subjects were investigated by videokeratography in comparison with slit-lamp biomicroscopy and keratometry. To detect keratoconus, corneal topography maps were examined with modified Robinowitz-McDonnell test. MAIN OUTCOME MEASURES: In this test, maps with central corneal power greater than 47.2 diopters and/or the inferosuperior asymmetry value greater than 1.4 were considered to have a keratoconus pattern. The findings of VKC were also recorded, RESULTS: The distribution of clinical forms of VKC were as follows: 46.34% mixed, 43.90% palpebral, and 9.76% limbal types. Twenty-six (31.7%) of 82 subjects had complications with keratopathy such as pseudo-genontoxon, punctate keratitis, and shield ulcer. Forty-four eyes (26.8%) were detected as keratoconus by quantitative evaluation of videokeratography maps. 14 eyes (8.5%) by biomicroscopy, and 30 eyes (18.3%) by keratometry. The increased incidence of keratoconus was associated with male gender, long-standing disease, mixed and palpebral forms, and advanced corneal lesions. CONCLUSIONS: The higher incidence of keratoconus in our study compared with the previous reports may result from early detection of mild keratoconus by interpretation of color-coded videokeratographic maps with a sensitive quantitative method.

Adolescent↗
PubMed1991

Keratoconus associated with floppy eyelid syndrome.

Floppy eyelid syndrome is a recently described entity, which characteristically involves overweight individuals. The characteristic findings are an upper lid that may be readily everted, tarsal laxity, and diffuse papillary conjunctival changes. The cause of floppy eyelid syndrome is believed to be a mechanical disorder due to the eversion of the lids while sleeping. The cause of keratoconus remains uncertain. There are strong proponents to a mechanical etiology for this disease. The authors report five cases of floppy eyelid syndrome with concomitant keratoconus. One patient with bilateral keratoconus had bilateral symmetric floppy eyelid syndrome. The other four patients had asymmetric keratoconus and floppy eyelid syndrome. In all four patients, the keratoconus was significantly worse in the eye with the more severe case of floppy eyelid syndrome. In addition, these four patients all gave a history of sleeping with their head facing predominantly on the side with the floppy eyelid syndrome and keratoconus. Two patients with keratoconus and floppy eyelid syndrome were able to undergo successful contact lens rehabilitation of their keratoconus after treatment of the floppy eyelid syndrome.

Adult↗
PubMed2004

[The relationship between keratoconus and axial myopia].

PURPOSE: To study the relationship between keratoconus and axial myopia. METHODS: We prospectively studied refraction and ocular biometry in 100 consecutive keratoconus eyes, and 100 emmetropic eyes. Biometric data (including posterior segment length) were obtained by A-scan ultrasound, Orbscan, and ultrasonic pachymetry. Biometric measurements were compared in both groups. RESULTS: Anterior chamber depth, posterior segment length and axial length were significantly different between the two groups (p<0.001). Axial length was significantly greater in the keratoconus group than in the emmetropic group (23.97 mm versus 23.21 mm, p<0.001). Posterior segment length was significantly greater in the keratoconus group than in the emmetropic group (16.54 mm versus 15.99 mm, p<0.001). In the keratoconus group, the posterior segment length and the subjective spherical equivalent were significantly correlated (rs=-0.45, p<0.001). CONCLUSION: The increase in posterior segment length in the keratoconus group and the correlation between posterior segment length and spherical equivalent in the keratoconus group suggest a statistical relationship between keratoconus and axial myopia.

Adolescent↗
PubMed2006

[Keratoconus: epidemiology, risk factors and diagnosis].

Keratoconus is a bilateral, non-inflammatory and progredient corneal ectasia with an incidence of approximately 1 per 2,000 in the general population. Within the second decade of life the cornea develops a conical shape, due to thinning of the corneal stroma with subsequent irregular astigmatism and myopia leading to marked impairment of vision. The most common presentation of the keratoconus is as a sporadic disorder, but it has long been recognized that a significant minority of patients exhibit a family history as an autosomal dominant mode of inheritance. Most investigators suggest complete penetrance of predisposing factors with variable phenotypic expression. In some patients heterozygous mutations in the VSX1 gene are described as the underlying gene defect. An association with Down syndrome, monosomia X (Turner syndrome), Leber's congenital amaurosis, mitral valve prolaps, collagenosis, retinitis pigmentosa and Marfan syndrome is described. The role of corneal cells in the pathogenesis of keratoconus is supported by the published reports of recurrence of keratoconus in eyes after penetrating keratoplasty due to graft repopulation by the recipient cells. Placido-based computeed videokeratographic corneal curvature mapping systems, linked with pachymetry, are useful for identifying overt and subclinical cases of keratoconus. Different indices may quantify the clinical features of keratoconus and may improve the classification. We compared videokeratometric data (Fourier series harmonic analysis and wavefront analysis) in eyes with keratoconus to answer the question of which parameters are useful for early diagnosis of keratoconus.

Comorbidity↗
PubMed1999

[Calculating the localization and dimension of the real pupil in keratoconus with ray tracing of corneal topography data].

BACKGROUND: It is crucial to center surgical procedures for optical indications on the pupil or the optical axis of the eye. In keratoconus the pupil appears to be dislocated due to optical aberrations of corneal topography. The purpose of this study was to evaluate the real pupil structure from the virtual image using exact raytracing techniques. PATIENTS AND METHODS: Eighty-eight patients with keratoconus (46 with mild and 42 with severe clinical signs) and a control group of 40 normal subjects were included in this study. Topographic height data were calculated from refraction data of a commercially available topographer (TMS-1) using a local approximation algorithm and a convex surface was modelled using a subdivision scheme. For the posterior corneal surface we postulated an aspherical surface with a central radius of curvature of 6.5 mm using Navarro's model eye. At the virtual pupil outline a bundle of parallel rays were intersected with the anterior and posterior corneal surface and refracted into the anterior chamber. The intersections of these rays with the pupil plane was defined as the real pupil outline. We assessed the amount and direction of pupil dislocation, the ratio between the virtual and real pupil size for each group and correlated these parameters with the central corneal power. RESULTS: The size of the virtual pupil exceeded the reference value of the real pupil in the normal group by 11%, in the group with mild keratoconus by 19% and in the group with severe keratoconus by 35%. The center of the virtual pupil was decentered 0.06 mm in the normal group, 0.49 in the group with mild keratoconus and 1.24 mm in the group with severe keratoconus. Whereas the direction of decentration was randomly in the normal group, we measured a preferred decentration to the inferior quadrants in mild keratoconus and a systematic decentration to the temporal inferior quadrant in severe keratoconus. Correlation of the optical dislocation did not correlate with central corneal power in any group. CONCLUSIONS: In keratoconic eyes the pupil outline is distorted and dislocated due to optical aberrations of the cornea. Exact raytracing technique allows the calculation of the real pupil outline from the virtual image and the topographic height of both corneal surfaces. Knowledge about the real pupil position may have an impact on adequate centration of keratorefractive surgery and penetrating keratoplasty.

Adult↗
PubMed2004

Keratoconus staging: a computer-assisted ultrabiomicroscopic method compared with videokeratographic analysis.

PURPOSE: The aim of this study was to introduce a new paradigm for keratoconus assessment, the keratoconus index (KI), generated from the ratio of peripheral corneal thickness (PCT) to the thinnest corneal thickness (TCT), and calculated by a computer-assisted procedure after ultrabiomicroscope (UBM) examination. Then we compared KI and the keratoconus severity index (KSI), obtained by videokeratography in patients with different stages of keratoconus. METHODS: We studied 60 eyes with different forms of keratoconus using the TMS-3 autotopographer, provided with a keratoconus screening program (using Smolek-Klyce methods) and the commercial version of the ultrasound biomicroscope (Paradigm UBM Plus Model P45) equipped with a 50-MHz probe, which was provided with our computer-assisted program. The proportion test Z and the correlation coefficient R were applied to the outcomes. RESULTS: The keratoconus severity index, KSI, obtained by color-coded videokeratographic maps, was in the range 95% to 32% (mean 52.22%). By means of UBM examination, we obtained 60 images and found values of TCT 0.278-0.592 mm and PCT 0.475-0.704 mm. Applying the computer-assisted method, we obtained values for KI of 1.112-2.159 (mean 1.428). CONCLUSIONS: KI is correlated as well as KSI with the severity of the keratoconus (R = 0.76, P < 0.0001). It can be used as a similar parameter to measure the evolution of the disease, on the basis of corneal thickness rather than the curvature.

Adult↗
PubMed2004

Keratoconus in Asian eyes at a tertiary eye care facility.

BACKGROUND: The purpose of this study was to assess the demographic variables, age at diagnosis, keratometry and slitlamp signs in keratoconus. METHODS: Thirty-one patients with 61 keratoconic eyes were selected provided they met one of two criteria: 1. They had an irregular corneal surface, Vogt's striae, Fleischer's ring or apical sub-epithelial corneal scarring characteristic of keratoconus; 2. Corneal topography revealed an average simulated keratometry of more than 45.2 D, central corneal power higher than 47.2 D or infero-superior asymmetry greater than 1.4 D. The main outcome measures were demographic variables, age at diagnosis, disease severity on keratometry and biomicroscopic signs. RESULTS: The patients' mean age at presentation was 20.2 +/- 6.4 years. Based on average keratometry values, 67.2 per cent of eyes had severe and 32.8 per cent had moderate keratoconus. Eyes with severe keratoconus presented at a younger average age (18.8 +/- 5.35 years) than moderate keratoconus (23.69 +/- 8.07 years). Thirty-eight eyes (92.5 per cent) with severe and 13 eyes (65 per cent) with moderate keratoconus demonstrated biomicroscopic signs of keratoconus. Twenty eyes (32.7 per cent) demonstrated apical sub-epithelial cornea scarring and 95 per cent of these eyes had severe keratoconus. CONCLUSIONS: The majority of keratoconic eyes in Asian-Indian patients demonstrate the severe stage of the disease by the second decade.

Adolescent↗
PubMed1989

Association between keratoconus and atopy.

Sixty-seven patients with keratoconus were classified according to atopic status. Keratoconus patients with and without atopy did not differ significantly with regard to sex, age of onset, or rate of keratoplasty, but patients with very high IgE levels were more prone to graft rejection. Atopy was less common in patients with unilateral keratoconus, and keratoconus occurred more frequently on the side of the dominant hand. There was a significantly lower frequency of HLA B7 in the keratoconus group than in the controls. No abnormalities of essential fatty acid metabolism were found in keratoconus patients with or without atopy. There was no social class bias in the group. The study included a brother and sister with keratoconus and atopy, and a non-atopic patient whose identical twin did not have keratoconus.

Asthma↗
PubMed2000

Atopy and keratoconus: a multivariate analysis.

BACKGROUND/AIMS: The primary goal of this study was to determine if atopy is a risk factor for keratoconus. Other potential risk factors were also studied and included age, sex, race, eye rubbing, mitral valve prolapse, handedness, collagen vascular disease, ocular trauma, pigmentary retinopathy, Marfan's syndrome, Down's syndrome, and a history of contact lens wear. METHODS: A case-control study was designed (n=120) with incident cases assembled from the years 1985-99. Controls were chosen from the same person-time experience as cases and were picked from a source population with multiple outcomes ensuring that none was knowingly related to any of the potential exposures being studied. Atopy was defined based on the UK working group 1994 definition (at least 4/6 criteria = complete, 3/6 criteria = incomplete, and at least 1/6 criteria = partial). Keratoconus was defined based on clinical criteria and previously published I-S values. Multiple logistic regression was used in the analysis to obtain the odds ratios as the measure of association. RESULTS: In the univariate associations, there was an association between keratoconus and atopy as well as eye rubbing and family history of keratoconus. However, in the multivariate analysis, only eye rubbing was still a significant predictor of keratoconus (odds ratio = 6.31 p = 0.001). CONCLUSIONS: This study supports the hypothesis that the most significant cause of keratoconus is eye rubbing. Atopy may contribute to keratoconus but most probably via eye rubbing associated with the itch of atopy. No other variable measured was significantly associated with the aetiology of keratoconus.

Adult↗
PubMed2002

The expression of protein betaig-h3 inducible by transforming growth factor-beta in keratoconus and normal cornea.

OBJECTIVE: To observe the expression of a protein inducible by transforming growth factor-beta (betaig-h3) in normal cornea and keratoconus and discuss the effects of extracellular matrix on keratoconus. METHODS: In situ hybridization method was used to detect the expression of betaig-h3 in the cornea. The cDNA library was screened with human betaig-h3 cDNA probe to orient betaig-h3 mRNA in cells. The level of betaig-h3 was detected in normal cornea and keratoconus. RESULTS: betaig-h3 mainly expressed in the stroma in normal cornea and keratoconus. The positive expression decreased along with the increase of severity of the keratoconus. The negative expression was seen in severe lesions of keratoconus. The strong positive expression was seen at the interface area between the normal and the lesion of keratoconus. CONCLUSION: The decreasing of the level of betaig-h3 causes the diminution of corneal steadiness that is related to the formation of keratoconus.

Cornea↗
PubMed1992

Synchrotron x-ray diffraction studies of keratoconus corneal stroma.

The aim of this study was to determine any differences in the collagen molecular and fibrillar packing, or the arrangement of the proteoglycans along the fibril axis, in the stroma of keratoconus and control corneas. High and low-angle x-ray diffraction patterns from the fibrillar and molecular packing of collagen in keratoconus and control corneas were obtained using a synchrotron radiation source. The results indicate no difference in interfibrillar spacing between keratoconus and control corneas at normal physiological hydration, or over a range of hydrations (H = 1-11). This unambiguously demonstrates that the thinning of the stroma that occurs in keratoconus is not a result of closer packing of the collagen fibrils in the stroma. Intermolecular spacings were shown to be significantly (P less than 0.001) lower in keratoconus corneas at normal physiological hydration and over a range of hydrations (H = 1-11). Meridional patterns from the axial distribution of electron density along the collagen fibrils were obtained from untreated control and keratoconus corneas and from the corneas after their proteoglycans were stained with cupromeronic blue. Analysis of the integrated intensities of the first nine orders of these reflections show there is a difference in the staining behavior of collagen-associated proteoglycans in control and keratoconus corneas. Determination of the electron density vectors along the collagen fibrils of cupromeronic blue-stained corneas by the use of Patterson functions indicates that the keratoconus corneal stroma has a specific, ordered proteoglycan that is present in lower numbers along the collagen fibrils, and that it stains less with cupromeronic blue or is in a more disordered arrangement than in the controls.

Adult↗
PubMed2006

Molecular changes in selected epithelial proteins in human keratoconus corneas compared to normal corneas.

PURPOSE: The purpose of the study was to determine molecular changes in selected epithelial proteins in human keratoconus (KC) corneas compared to normal corneas. METHODS: Two-dimensional (2-D) gel electrophoretic profiles of epithelial cell proteins from normal and keratoconus corneas were compared, and the selected protein spots that showed either up- or downregulation were identified. The desired spots were identified after trypsin digestion and mass spectrometric analysis. Based on the results, two proteins, alpha-enolase and beta-actin, were further analyzed by immunohistochemical and western blot methods, using respective antibodies. To determine the presence of mRNA of the two proteins in the epithelial cells, RT-PCR studies were performed. RESULTS: On comparison of the 2-D gel electrophoretic protein profiles, two protein spots were identified in normal corneas that were either absent or present at lower levels in keratoconus corneas. The two spots were determined to be alpha-enolase (48 kDa) and beta-actin (42 kDa) by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), and ES-MS/MS mass spectrometric methods. Immunohistochemical analysis revealed that alpha-enolase and beta-actin were present at extremely low levels in the epithelial superficial and wing cells of the keratoconus corneas compared to these cells of normal corneas. 2-D gel electrophoresis followed by western blot analysis revealed relatively greater degradation of the two proteins in the keratoconus corneas compared to normal corneas. RT-PCR analysis showed the mRNA expression of the two proteins in the epithelial cells of both normal and keratoconus corneas. CONCLUSIONS: The results showed relatively low or negligible levels of alpha-enolase and beta-actin in the wing and superficial epithelial cells of keratoconus corneas compared to normal corneas. This was attributed to relatively greater degradation of the two proteins in keratoconus corneas compared to normal corneas.

Actins↗
PubMed1990

[Quantitative analysis of collagen fiber in keratoconus].

In order to identify the direct pathogenic factors involved in the stromal thinning of keratoconus, quantitative analysis of keratocytes, collagen fibers and collagen lamellae in keratoconus cornea was performed histologically by light and electron microscopy. Both normal and keratoconus corneas showed a similar cell density of keratocytes in the central stroma, therefore the total number of keratocytes in keratoconus cornea might be smaller than that of controls, because of the thinning of stroma in the keratoconus. The collagen lamellae in keratoconus corneas showed a significant decrease in number compared with controls. There was a direct relationship between the stromal thickness and number of collagen lamellae. On the other hand, there was no statistical significance between normal and keratoconus corneas in terms of the thickness of collagen lamellae. These results suggest that the thinning of the cornea in keratoconus might occur as the result of a defect of some collagen lamellae due to a disorganization during the process of collagen lamellae formation.

Adolescent↗
PubMed1994

Keratoconus and contact lens-induced corneal warpage analysis using the keratomorphic diagram.

PURPOSE: Videokeratography of early keratoconus may be difficult to distinguish from contact lens-induced corneal warpage, even by experienced examiners. Furthermore, topographic irregularity may be judged inconsistently if quantitative standards are not applied. Quantitative measures based on videokeratographic data were developed and evaluated to determine if improved corneal topographic classification can be achieved. METHODS: The Corneal Irregularity Coefficient (CIC) and Corneal Power Coefficient (CPC) were derived from multiple measures of mean corneal power and its variance for 207 videokeratographs of normal, warped, keratoconus, and keratoconus-suspect corneas. CIC was plotted against CPC, creating a distribution of points representing all maps that tended to be grouped according to surface conditions (the Keratomorphic Diagram). Normal, steep, abnormal, and warped zones were defined by CIC and CPC cutoff values chosen to distinguish normal from keratoconus corneas graphically. RESULTS: Seventy of 76 normal corneas were grouped in the normal zone and 6 in the steep zone; 84 of 84 keratoconus corneas were grouped in the abnormal zone; 35 of 35 contact lens-induced warpage cases were grouped in the warped zone; and 10 of 12 keratoconus-suspect corneas were grouped in the warped zone, with 2 in the abnormal zone. Serially plotted data of keratoconus progression and warpage regression demonstrated that the vector displacement of CIC and CPC values may provide a potentially useful means of distinguishing contact lens-induced warpage from keratoconus-suspect corneas. CONCLUSION: The Keratomorphic Diagram aids in classifying and comparing corneal shape by plotting indices along axes with easily recalled scales. The diagram may become a useful tool to assess presurgical corneal surface instability and postoperative progression of corneal shape change due to healing.

Contact Lenses↗
PubMed1993

Modification of prostaglandin E2 and collagen synthesis in keratoconus fibroblasts, associated with an increase of interleukin 1 alpha receptor number.

Keratoconus, a bilateral corneal disease, is characterized by modifications in corneal shape and thinning of the stroma. It affects young people. From a biochemical point of view, a decrease in collagen content, probably due to the high collagenase activity, has been reported. In these experiments, we have studied the membrane receptors for interleukin 1 alpha, and the corresponding dissociation constant (KD). We also investigated synthesis of prostaglandin E2 (PGE2) and collagen, as well as kinetics of cyclooxygenase. Data from normal human corneas and from keratoconus were compared. Fibroblasts from keratoconus proved to bear four fold more IL1 binding sites than those from normal cornea, with similar KD. Both types of cells synthesize prostaglandin E2, even if IL1 is not added to the medium, but the keratoconus cells produce ten times more than the normal cornea cells. When the cells are stimulated with IL1, synthesis of PGE2 strongly increases and the amounts produced by keratoconus cells are always higher than those of the normal cornea cells. Kinetics of the cyclooxygenase show that Vmax. is 10 times higher in keratoconus than in normal cornea cells; Km's are the same. The amounts of collagen synthesized by keratoconus cells are slightly lower than those of normal cornea cells. Addition of IL1 to the cultures enhances synthesis of collagenase by the cells and decreases collagen found in the culture media. The drop of collagen is more important in keratoconus than in normal cornea cell cultures.

Cells, Cultured↗
PubMed1997

[Keratoconus, changes in corneal topography and allergy. Study of 3 groups of patients].

PURPOSE: To study the relation between keratoconus and atopy based on allergic prick tests, and the association of infraclinical keratoconus with atopy compared to "normal eyes". Simultaneously corneal topographic modifications have been researched to patients presenting an ocular atopy versus normal patients. MATERIAL AND METHOD: A videokeratoscope has been used for the selection of 22 keratoconic patients, 17 infraclinical keratoconic subjects and 22 patients with no ocular abnormality. Incidence of allergic phenomenon was assessed with two tests (Prick test, lacrymal total IgE dose). The videokeratoscopy was also performed in the research of corneal modifications in a group of 45 patients with an ocular atopy. RESULTS: The results of allergologic tests (positives Prick tests) showed a statistical significant difference between the keratoconus group (63.6%) and respectively the infraclinical keratoconus group (23.5%) and the normal eyes group (22.7%). No videotopographic picture of keratoconus and infraclinical keratoconus has been noted in patients with ocular atopy. CONCLUSION: Keratoconus is related to allergy. In this study, no association of allergy with infraclinical keratoconus was found. Further more, no videotopographic changes was observed in ocular allergic cases.

Adolescent↗
PubMed1997

Current keratoconus detection methods compared with a neural network approach.

PURPOSE: Four videokeratographic methods for keratoconus detection were compared with a neural network approach. METHODS: A classification neural network for keratoconus screening was designed to detect the presence of keratoconus (KC) or keratoconus suspects (KCS); a separate cone severity network graded the severity of conelike topography patterns consistent with KC or KCS. Three hundred TMS-1 examinations (Tomey) were randomly divided into training and test sets. Ten topographic indexes were network inputs. Nine categories were used: normal, astigmatism, KC, KCS, contact lens-induced warpage, pellucid marginal degeneration, photorefractive keratectomy, radial keratotomy, and penetrating keratoplasty. KC was subdivided into KC1 (mild), KC2 (moderate), and KC3 (advanced). There were three outputs for the classification network (KC, KCS, and OTHER); target output values of 0 = OTHER, 0.25 = KCS, 0.5 = KC1, 0.75 = KC2, and 1.0 = KC3 were used for the severity network. RESULTS: The best-trained classification network had 100% accuracy, specificity, and sensitivity for the test set. The severity network had mean outputs (+/-standard deviation) of OTHER = 0.02+/-0.02, KCS = 0.21+/-0.05, KC1 = 0.52+/-0.17, KC2 = 0.74+/-0.12, and KC3 = 0.91+/-0.15. The severity network output for all categories was well correlated to the keratoconus prediction index (R = 0.892, P < 0.0001). The classification network had an overall accuracy and specificity significantly better (P < or = 0.005) than the Klyce/Maeda keratoconus index (KCI) test, the Rabinowitz test (K & I-S), and simulated keratometry (average Sim K). However, there were no significant differences in keratoconus sensitivity between the classification network, KCI, and K & I-S. The sensitivity and specificity of average Sim K were significantly worse than those of the other tests. The classification network had significantly better sensitivity (P < 0.001) and specificity (P = 0.025) for KCS detection than the K & I-S. CONCLUSIONS: The neural networks completely distinguished KC from KCS and from topographies that resembled KC. The network approach equaled the sensitivity of currently used tests for keratoconus detection and outperformed them in terms of accuracy and specificity.

Cornea↗
PubMed1998

Expression of degradative enzymes and protease inhibitors in corneas with keratoconus.

PURPOSE: Keratoconus is characterized by thinning and scarring of the central region of the cornea. Previous research showed that, in corneas obtained from patients with keratoconus, lysosomal enzyme activities are elevated, whereas levels of protease inhibitors such as alpha1-proteinase inhibitor are reduced. This study was undertaken to examine further the expression of a spectrum of proteolytic enzymes and protease inhibitors. METHODS: Corneal buttons were collected from patients with keratoconus, healthy subjects, and patients with other corneal diseases. Immunohistochemical staining was performed on paraffin sections. Enzymatic assays and western blot analysis were carried out for cathepsins B and G. In addition, an in situ zymography procedure was used to examine the gelatin- and casein-digesting activities in corneas with keratoconus. RESULTS: An enhanced staining was found with antibodies to cathepsins B and G. Enzymatic assays and western blotting confirmed that the levels of these two enzymes were elevated in corneas with keratoconus. No alteration was noted with any of the matrix metalloproteinase (MMP) family members and other enzymes and inhibitors examined, although in situ zymography did indicate an increase in net gelatin- and casein-digesting activities in corneas with keratoconus. These activities were mostly abolished by inhibitors for serine and cysteine proteinases, but not by those for MMPs and aspartic proteinases. CONCLUSIONS: Levels of cathepsins B and G are increased in corneas with keratoconus. These enzymes may contribute to the heightened in situ gelatin- and casein-digesting activities, leading to abnormalities in keratoconus.

Adolescent↗