(1/337) Zernike representation of corneal topography height data after nonmechanical penetrating keratoplasty.
PURPOSE: To demonstrate a mathematical method for decomposition of discrete corneal topography height data into a set of Zernike polynomials and to demonstrate the clinical applicability of these computations in the postkeratoplasty cornea. METHODS: Fifty consecutive patients with either Fuchs' dystrophy (n = 20) or keratoconus (n = 30) were seen at 3 months, 6 months, and 1 year (before suture removal) and again after suture removal following nonmechanical trephination with the excimer laser. Patients were assessed using regular keratometry, corneal topography (TMS-1, simulated keratometry [SimK]), subjective refraction, and best-corrected visual acuity (VA) at each interval. A set of Zernike coefficients with radial degree 8 was calculated to fit two model surfaces: a complete representation (TOTAL) and a representation with parabolic terms only to define an approximate spherocylindrical surface (PARABOLIC). The root mean square error (RMS) was calculated comparing the corneal raw height data with TOTAL (TOTALRMS) and PARABOLIC (PARABOLICRMS). The cylinder of subjective refraction was correlated with the keratometric readings, the SimK, and the respective Zernike parameter. Visual acuity was correlated with the tilt components of the Zernike expansion. RESULTS: The measured corneal surface could be approximated by the composed surface 1 with TOTALRMS < or = 1.93 microm and by surface 2 with PARABOLICRMS < or = 3.66 microm. Mean keratometric reading after suture removal was 2.8+/-0.6 D. At all follow-up examinations, the SimK yielded higher values, whereas the keratometric reading and the refractive cylinder yielded lower values than the respective Zernike parameter. The correlation of the Zernike representation and the refractive cylinder (P = 0.02 at 3 months, P = 0.05 at 6 months and at 1 year, and P = 0.01 after suture removal) was much better than the correlation of the SimK and refractive cylinder (P = 0.3 at 3 months, P = 0.4 at 6 months, P = 0.2 at 1 year, and P = 0.1 after suture removal). Visual acuity increased from 0.23+/-0.10 at the 3-month evaluation to 0.54+/-0.19 after suture removal. After suture removal, there was a statistically significant inverse correlation between VA and tilt (P = 0.02 in patients with keratoconus and P = 0.05 in those with Fuchs' dystrophy). CONCLUSIONS: Zernike representation of corneal topography height data renders a reconstruction of clinically relevant corneal topography parameters with a marked reduction of redundance and a small error. Correlation of amount/axis of refractive cylinder with respective Zernike parameters is more accurate than with keratometry or respective SimK values of corneal topography analysis. (+info)
(2/337) Visual function after penetrating keratoplasty for keratoconus: a prospective longitudinal evaluation.
AIMS: To evaluate visual function and vision specific health status in patients undergoing penetrating keratoplasty for keratoconus. METHODS: A prospective longitudinal study measuring logMAR visual acuity, contrast sensitivity, disability glare, binocular visual field, stereoacuity, and subjective visual function (VF-14) was conducted on 18 patients with keratoconus undergoing penetrating keratoplasty (PK), including six patients who had already had PK in the fellow eye. Data were collected preoperatively and at 3, 9, and 18 months after surgery. RESULTS: Within 3 months of surgery there was significant improvement in aided visual acuity, contrast sensitivity, and stereoacuity (p<0.05); disability glare (p<0.05) no longer had a significant detrimental effect on these variables. VF-14 score improved significantly throughout the postoperative period (p<0.05). There was significant correlation of the VF-14 score with aided visual acuity, binocular visual field, and stereoacuity. Postoperative astigmatism (<4D v >4D) did not affect the VF-14 score significantly. CONCLUSIONS: There is substantial and rapid improvement in visual function and vision specific health status in keratoconic patients as a result of uncomplicated penetrating keratoplasty. (+info)
(3/337) Acute hydrops in the corneal ectasias: associated factors and outcomes.
PURPOSE: To identify factors associated with the development of hydrops and affecting its clinical outcome. METHODS: Chart review of all patients with acute hydrops seen by a referral cornea service during a 2.5-year period between June 1996 and December 1998. RESULTS: Twenty-one patients (22 eyes) with acute hydrops were seen. Nineteen patients had keratoconus, 2 had pellucid marginal degeneration, and 1 had keratoglobus. Twenty-one of 22 (95%) eyes had seasonal allergies and 20 of 22 (91%) eyes had allergy-associated eye-rubbing behavior. Six of 22 (27%) had a diagnosis of Down's syndrome. Six patients were able to identify a traumatic inciting event: vigorous eye rubbing in 4 and traumatic contact lens insertion in 2. The affected area ranged from 7% to 100% of the corneal surface area and was related to disease duration and final visual acuity. Proximity of the area of edema to the corneal limbus ranged from 0 to 2.3 mm and was also related to prognosis. Three serious complications were observed: a leak, an infectious keratitis, and an infectious keratitis and coincidental neovascular glaucoma. Various medical therapies did not differ significantly in their effect on outcome, and ultimately 4 (18%) of 22 patients underwent penetrating keratoplasty. Best-corrected visual acuity was equal to or better than prehydrops visual acuity in 5 of the 6 patients in whom prehydrops visual acuity was known, without corneal transplantation. CONCLUSIONS: Allergy and eye-rubbing appear to be important risk factors in the development of hydrops. Visual results are acceptable in some patients without surgery. Close observation allows for the early detection and treatment of complications such as perforation and infection. (+info)
(4/337) A novel locus for Leber congenital amaurosis (LCA4) with anterior keratoconus mapping to chromosome 17p13.
PURPOSE: A two-generation consanguineous Pakistani family with autosomal recessive Leber congenital amaurosis (LCA, MIM 204,000) and keratoconus was identified. All affected individuals have bilateral keratoconus and congenital pigmentary retinopathy. The goal of this study was to link the disease phenotype in this family. METHODS: Genomic DNA was amplified across the polymorphic microsatellite poly-CA regions identified by markers. Polymerase chain reaction (PCR) products were separated by nondenaturing polyacrylamide gel electrophoresis. Alleles were assigned to individuals, which allowed calculation of LOD scores using the Cyrillic and MLINK software program. The retinal guanylate cyclase (RETGC-1, GDB symbol GUC2D) and pigment epithelium-derived factor (PEDF) genes were analyzed by heteroduplex analysis and direct sequencing for mutations in diseased individuals. RESULTS: Based on a whole genome linkage analysis the first locus for this combined phenotype has been mapped to chromosome 17p13. Linkage analysis gave a two point LOD score of 3.21 for marker D17S829. Surrounding this marker is a region of homozygosity of 15.77 cM, between the markers D17S1866 and D17S960; however, the crossover for the marker D17S1529 refines the region to 10.77 cM within which the disease gene is predicted to lie. Mutation screening of the nearby RETGC-1 gene, which has been shown to be associated with LCA1, revealed no mutations in the affected individuals of this family. Similarly, another prime candidate in the region PEDF was also screened for mutations. The factor has been shown to be involved in the photoreceptor differentiation and neuronal survival. No mutations were found in this gene either. Furthermore, RETGC-1 was physically excluded from the critical disease region based on the existing physical map. CONCLUSIONS: It is therefore suggested that this combined phenotype maps to a new locus and is due to an as yet uncharacterized gene within the 17p13 chromosomal region. (+info)
(5/337) Graft failure in human donor corneas due to transmission of herpes simplex virus.
AIM: To report the clinical consequences of contamination of human donor corneas by herpes simplex virus (HSV) in organ culture. METHODS: Two patients without previous history of ocular HSV infection underwent penetrating keratoplasty (PK), one for keratoconus and the other for Fuchs' endothelial dystrophy. One patient suffered primary graft failure while the other developed a persistent epithelial defect, ultimately resulting in graft failure. Viral culture of swabs taken from both corneas during the early postoperative period was undertaken. The failed donor corneas were examined histopathologically by immunohistochemistry (IHC) for HSV-1 antigens, transmission electron microscopy (TEM), and by polymerase chain reaction (PCR) for HSV DNA. Both failed corneas were replaced within 6 weeks of the initial surgery. The records of the fellow donor corneas were also examined for evidence of infection. RESULTS: HSV was cultured from both corneas during the early postoperative period. Histology of both donor corneas demonstrated a thickened corneal stroma with widespread necrosis of keratocytes and loss of endothelial cells. IHC showed keratocytes positive with antibodies to HSV-1 antigens. TEM demonstrated HSV-like viral particles within degenerating keratocytes. PCR performed on the failed corneal grafts was positive for HSV-1 DNA, whereas PCR performed on the excised host corneal buttons was negative in both patients. Records of the fellow donor corneas showed that one cornea was successfully transplanted into another recipient after 18 days in organ culture, whilst the other was discarded because of extensive endothelial cell necrosis noted after 15 days in organ culture. CONCLUSION: HSV within a donor cornea may cause endothelial destruction in organ culture and both primary graft failure and ulcerative keratitis after transplantation. Endothelial necrosis of a donor cornea in culture also raises the possibility of HSV infection within the fellow cornea. (+info)
(6/337) 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. (+info)
(7/337) Corneal endothelial cell apoptosis in patients with Fuchs' dystrophy.
PURPOSE: To investigate whether apoptosis plays a notable role in degeneration of corneal endothelial cells in patients with Fuchs' dystrophy. METHODS: Forty-seven corneal buttons from 41 patients with Fuchs' dystrophy were studied. Nucleus labeling, transmission electron microscopy (TEM), and TdT-dUTP terminal nick-end labeling (TUNEL) were used to detect apoptosis. TEM and TUNEL were performed on sections of all 47 corneal buttons, and nucleus labeling was performed on the last 10 corneas. Seven human donor corneas, two corneal buttons from two patients with keratoconus, and one corneal button from a patient with interstitial keratitis were used as negative controls for detection of apoptotic endothelial cells. Negative controls were studied by means of nucleus labeling, TUNEL, and TEM. RESULTS: In the nucleus labeling assay, the average percentage of apoptotic endothelial cells was 2.65% in the Fuchs' dystrophy group (n = 10) and 0.23% in the control group (n = 10; P = 0.0003). In the TUNEL assay, labeling of some endothelial cells was observed on 42 of 47 corneas in the Fuchs' dystrophy group, whereas it was absent on most specimens of the control group. In TEM, most endothelial cell nuclei had a normal appearance, and apoptotic endothelial cells featuring condensed nucleus and decreased cell size could be observed exceptionally. Some apoptotic cells were found in the basal epithelial cell layer by means of nucleus labeling, TUNEL, and TEM in the Fuchs' dystrophy group but not in the control group. CONCLUSIONS: This study suggests that apoptosis plays an important role in endothelial cell degeneration in Fuchs' dystrophy. Because of a lack of conclusive evidence of increased endothelial apoptosis by TEM, further studies are needed to ascertain this finding. (+info)
(8/337) The paretic pupil: its incidence and aetiology after keratoplasty for keratoconus.
The present study reveals that pupillary abnormalities are common after keratoplasty for keratoconus and that, in addition to the fixed dilated pupils which we have found in 7.8 per cent. of eyes, varying degrees of partially dilated pupil frequently occur after operation. In our experience, glaucoma is not a sequel to the simple paretic pupil, a finding which confirms the results of the smaller series of Alberth and Schnitzler (1971); glaucoma thus seems to be no more a special complication of keratoplasty for keratoconus than it is of keratoplasty for any other corneal pathology. The paretic pupils can be explained on the basis of ischaemic atrophy of the sphincter pupillae muscle secondary to an iris strangulation phenomenon occurring during surgery in the manner we have discussed. The relative frequency of a dilated pupil, together with the common finding of focal iris atrophy after minimal surgical trauma to the iris in cases of keratoconus, forces one to conclude that the pathology in this condition is not confined to the cornea but probably extends to the iris and possibly to the scleral envelope as well. (+info)