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At least 1,423 records · Page 79Linked to original sources
PubMed2004

[Functional outcomes after penetrating keratoplasty in pseudoexfoliation syndrome (PEX)-keratopathy].

PURPOSE: Keratopathy in pseudoexfoliation syndrome (PEX-keratopathy) is a particular form of corneal endothelial decompensation, which requires a penetrating keratoplasty (PK) for visual rehabilitation at advanced states. The aim of this study was to evaluate the functional outcome and the development of intraocular pressure (IOP) after PK in patients with PEX-keratopathy depending on the presence of pre-existing glaucoma. PATIENTS AND METHODS: This retrospective study included 21 eyes of 21 patients (age 78.6 +/- 7.5 years) with a mean postoperative follow-up of 1.8 +/- 2.2 (median 2) years. The diagnosis of PEX-keratopathy was confirmed clinically as well as by electron microscopy. The recipient and donor trephinations were performed from the epithelial side using an 193 nm excimer laser (n = 11) or mechanically (n = 10). An iridotomy was performed routinely during PK. The postoperative treatment with topical steroid was standardized. RESULTS: Preoperatively, a secondary open-angle glaucoma (SOAG) with optic nerve damage was diagnosed in 11 patients (52 %). Topical antiglaucomatous treatment was needed in 81 % of patients with SOAG. Six weeks postoperatively, patients with SOAG showed a higher prevalence of increased intraocular pressure (IOP) and/or antiglaucomatous treatment compared to patients without SOAG (45 % vs. 20 %). Most of the mild-early intraocular pressure elevations were controlled in both groups during the follow-up. From one year post-PK, there was an increased need for topical antiglaucomatous treatment in both patient groups. In all eyes the IOP was controlled by topical antiglaucomatous treatment. Preoperatively, visual acuity was comparable in patients with and without SOAG (0.06 +/- 0.09 vs. 0.08 +/- 0.1, p = 0.7), but increased significantly more in patients without SOAG (0.38 +/- 0.1, median 0.4) than in patients with SOAG (0.2 +/- 0.1, median 0.2; p = 0.01) after PK. Visual acuity remained stable in both groups throughout the follow-up period. During follow-up only one eye developed an episode of reversible endothelial graft rejection 18 months postoperatively. An irreversible graft failure was seen in none of the patients. CONCLUSION: The functional outcome after PK in PEX-keratopathy seems to be strongly associated with pre-existing SOAG. Patients without SOAG may expect good visual rehabilitation without persistent postoperative IOP increases. However, patients should be followed-up for a prolonged period of time, because from 1 year following PK the need for topical antiglaucomatous treatment increased significantly.

Aged↗
PubMed2006

[Current state of mechanical corneal surgery - results of a questionnaire to members of the cornea section of the German Society of Ophthalmologists].

AIM: The aim of this study was to obtain an overview on the surgical and the perioperative management strategies involved in mechanical corneal surgery in Germany, Switzerland and Austria. METHOD: A questionnaire was sent to 60 ophthalmological hospitals. RESULTS: Within one year the responding centres (n = 48) performed 3171 penetrating and 166 lamellar keratoplasties, 224 limbal stem cell--and 817 amniotic-membrane transplantations. In high-risk cases, 33 % of the centres did not use HLA-matched grafts. Predominantly manual trephine systems were used. Of the responding institutions 96 % used 10.0 nylon sutures and 64 % used a double running anti-torque technique for normal-risk keratoplasty. In tectonic and high-risk keratoplasties, interrupted sutures were used predominantly (70 % and 56 %). Suture removal was performed between one month (first suture) and up to 36 months (last suture) postoperatively. CONCLUSIONS: Procedures considered to be standard--such as penetrating keratoplasty--are performed with numerous and significant technical variations. The likely influence of such variations on the long-term outcome should be further evaluated.

Cornea↗
PubMed1993

[Bone marrow involvement in Hodgkin's disease: MR tomography and chemical-shift imaging].

The ranking of magnetic resonance imaging (MRI) and chemical shift imaging (CSI) of the bone marrow was assessed in 30 patients in the initial staging of Hodgkin's disease or in the restaging after relapse. The results were compared with other staging procedures, especially trephine biopsies. Pathologic findings were divided into diffuse and focal lesions resulting in a better differentiation between malignant infiltrations and unspecific marrow reactions that are common in Hodgkin's disease. Diffuse changes were unspecific, a diffuse marrow infiltration could not be established in 7 patients. Focal lesions proved to be infiltrations in 6 of 7 patients; only in one case an unspecific marrow reaction was found on histology. CSI showed a pathological increase of the relative water signal in focal and diffuse marrow changes, and made no individual diagnostic contribution.

Adolescent↗
PubMed1999

[Transplant endothelium and measuring corneal thickness after non-high-risk keratoplasty with briefly or long-term preserved corneal donor tissue].

PURPOSE: The corneal endothelial cell density is essential for the pump function and the transparency of grafts after penetrating keratoplasty (PK). The purpose of this study was to assess corneal endothelial cell density after non-high-risk PK and to check for possible correlations with storage parameters of the donor corneas using two different storage methods. PATIENTS AND METHODS: Endothelial cell density (specular microscope EM 1100, TOMEY, Erlangen) and central corneal thickness (ultrasonic pachymetry SP-2000, TOMEY, Erlangen) were assessed 6 weeks, 3, 6, 9 months and one year postoperatively in 168 non-high-risk PKs. Short-term-preserved donor corneas were used in 89 patients, whereas in 79 patients organ-cultured corneas were used. The donor trephination was performed from the epithelial side using an artificial anterior chamber. The postoperative treatment with topical steroids was standardized. The mean donor post-mortem time was 9.6 +/- 8.0 hours for short-term-preserved and 17.6 +/- 10.5 hours for organ-cultured corneas (p < 0.0001). The storage time was 71 +/- 49 and 380 +/- 167 hours (p < 0.0001), respectively. RESULTS: Endothelial cell density did not differ significantly between the two storage methods (p > 0.05). At 6 weeks postoperatively, the mean endothelial cell density was 2042 +/- 675 cells/mm2 for short-term-preserved corneas and 1972 +/- 522 cells/mm2 for organ-cultured corneas (p = 0.7). Endothelial cell density did not decrease significantly (p > 0.05) within the observation period of 12 months in both groups (after 12 months: 1868 +/- 957 cells/mm2 and 1638 +/- 643 cells/mm2, respectively). The mean corneal thickness was 542 +/- 50 microns for short-term-preserved and 541 +/- 55 microns for organ-cultured corneas and remainded unchanged during the follow-up of 12 months (542 +/- 42 microns and 521 +/- 43 microns, respectively). Neither the group of short-term-preserved corneas nor organ-cultured corneas showed a significant correlation between endothelial cell density or central cornea thickness with post-mortem time or with storage time of the donor corneas at any postoperative stage (p > 0.1). CONCLUSION: During the first year after PK, only a small decrease in endothelial cell density was observed in comparison with the 6-weeks finding. The storage method does not seem to affect the short-term changes of endothelial cell density. Further long-term studies are necessary to assess the clinical relevance of these observations.

Adult↗
PubMed1997

[Fourier analysis as a mathematical model for evaluating and presenting postoperative corneal topography data after non-mechanical perforating keratoplasty].

BACKGROUND: Videokeratography has given the possibility to obtain information in curvature from a much larger region of the cornea than that covered by keratometry. Fourier analysis as a mathematical model can be used to represent real physical attributes of the cornea and to divide corneal topography in its basic components: the zero-frequency component as the mean ring power, the one-cycle component as a representation of decentration and the two-cycle component as a representation of regular corneal toricity. The purpose of this study was the reconstruction of the corneal refraction after penetrating keratoplasty with a small number of characteristic parameters and the evaluation of the time course of the fourier coefficients as indices for a regular astigmatic cornea in the postkeratoplasty period including suture removal. PATIENTS AND METHODS: Fourty patients (group 1: 20 primary dystrophies, group 2: 20 keratoconus) underwent nonmechanical trephination (excimer laser MEL60, Aesculap-Meditec, Heroldsberg, Germany) in penetrating keratoplasty. All procedures (7.5 mm in dystrophies, 8.0 mm in keratoconus, 8 orientation teeth, double-running 10-0 nylon suture) were performed by one surgeon. At a postoperative gate of 6 weeks, 6 months, before partial suture removal and after complete suture removal, corneal topography (TMS1, Tomey, Tennenlohe, Germany), keratometry, visual acuity and subjective refraction were assessed. Radial approximation with a 5th order polynomial fit of the refractive data on 25 non-centric rings of the TMS, within 256 hemimeridians was performed to get data at equally spaced concentric rings. Fast Fourier transformation of the data sets in the mid periphery (1.4-1.8 mm apical distance) was done to get DC-, one-cycle and two-cycle component. Fourier coefficients were correlated with keratometric readings, subjective refractive values and visual acuity. RESULTS: Spherical equivalent was fairly constant in the postoperative interval before suture removal. After suture removal, a corneal flattening of about 3 diopters occurred. The one-cycle component before suture removal tended to be higher in group 1 compared to group 2 before suture removal. This difference was statistically significant (p = 0.01) after suture removal. Comparing keratometry, calculated meridians by the Tomey software, two-cycle component of the fourier decomposition and subjective refraction, the best correlation (p = 0.02) was observed between two-cycle-component and the refractive cylinder in amplitude and axis after suture removal. Best corrected visual acuity was inversely correlated with the amount of energy of higher harmonics compared to the whole energy before (p = 0.04) and after (p = 0.01) suture removal. CONCLUSIONS: Fourier transformation renders reconstruction of corneal topography data with a marked data reduction and a small error. From fourier coefficients conclusions may be drawn concerning potential best-corrected visual acuity and amplitude/axis of subjective cylinder, even in corneas with severe local irregularities.

Adult↗
PubMed1992

[Technical problems in microsurgical processing of preserved donor tissue].

The microsurgical processing of longterm preserved tissue is still a problem for lamellar and perforating keratoplasties. Advantages of donor tissue cut with rotortrephines versus manual trephines are presented. Optimal possibilities of examination and storage of donor tissue are explained. A lamellar microkeratome, an artificial anterior chamber for corneoscleral discs and a refractive workbench for non-freeze modification are shown.

Corneal Transplantation↗
PubMed1992

[The unsolved problem of transplant astigmatism].

Irregularities of the trephine margins, donor/recipient thickness disparity and irregular suture technique are the important factors for high astigmatism after penetrating keratoplasty. A combined suture technique using eight interrupted 11-0 Mersilene sutures and a single continuous 10-0 nylon suture enables to control and to remedy the final postkeratoplasty astigmatism. In 35 patients with a corneal graft a final astigmatism of 2.9 diopters was reached after removal of the continuous suture and partial leaving in place of single interrupted Mersilene sutures.

Astigmatism↗
PubMed1992

[Corneal sensibility following epikeratophakia].

The postoperative rate of reinnervation following corneal surgery is widely considered to be a useful indicator of the healing process. This study reports the corneal sensitivity of 14 patients following epikeratophakia for different indications (myopia, aphakia and keratoconus) after time periods ranging from 7 to 104 weeks. All transplants were clear at the time of measurement. A newly developed aesthesiometer (using a low electric current for stimulation) was employed. Nine positions on the operated eye were chosen for the measurements, five locations of the non-operated fellow eye served as controls. On the operated eye the corneal sensitivity peripheral to the trephination were significantly reduced at the 9 and 12 o'clock positions as compared to the other eye. The 3 and 6 o'clock locations showed no significant difference. On the epikeratophakia lenticule the sensitivity was significantly reduced at all points, the center showing the largest difference (p less than 0.001). No correlation with age, sex or the indication for the procedure was observed. Although there was a trend of a positive correlation between the postoperative time period and the central corneal sensitivity, the follow-up was too short to reach significant levels. The nearly complete lack of corneal sensitivity, particularly in the center of the transplant is therefore well compatible with its long-time survival, even when the lenticule has been prepared with the cryolathe and lyophilized for transportation.

Adult↗
PubMed1986

[Effect of cyclosporin A, dexamethasone and various preservatives on epithelial wound healing in the denervated guinea pig cornea].

In order to examine a possible connection between punctate keratopathy following keratoplasty and the various drugs used in postoperative treatment, denervation was performed in white Pirbright guinea pigs by corneal trepanation with a 6 mm trephine to a depth of 0.25 mm. One week later an iodine gas applicator was used to produce erosion in the cornea, which had healed in the meantime. Until the erosions healed, the corneas were photographed four times daily after fluorescein staining; the negatives were enlarged by projection and the erosions measured planimetrically. The linear regression method was used to calculate a compensating straight line and thus the hourly epithelial wound-healing surface (mm2/h) for each eye. This was 0.76 mm2/h in control eyes. Dexamethasone 0.1%, benzalconium chloride 0.01%, and chlorobutanol 0.2% did not significantly inhibit wound healing, while Spersadex (dexamethasone 0.1% + benzalconium chloride 0.01%) and Totocortin (dexamethasone 0.1 + chlorobutanol 0.2%) did. Polyvinyl alcohol (1.4% without preservative) significantly delayed epithelial wound healing. Cyclosporin A 2% (in castor oil) had no influence on epithelial wound healing.

Animals↗
PubMed1999

Endoscopic neurosurgery "around the corner" with a rigid endoscope. Technical note.

Endoscopically "working around the corner" is presently restricted to the use of flexible endoscopes or an endoscope-assisted microneurosurgical (EAM) technique. In order to overcome the limitations of these solutions, endoscopic equipment and techniques were developed for "working around the corner" with rigid endoscopes. A steering insert with a 5 French working channel is capable of steering instruments around the corner by actively bending the guiding track and consecutively the instrument. A special fixation device enables strict axial rotation of the endoscope in the operating field. Endoscopic procedures "around the corner", including aqueductal stenting, pellucidotomy, third ventriculostomy and biopsy were performed in human cadavers. Special features of the used pediatric neuroendoscope system, i.e., reliable fixation, axial rotation, and controlled steering of instruments, increase the safety and reduce the surgical traumatization in selected cases, such as obstructive hydrocephalus due to a mass lesion in the posterior third ventricle, since endoscopic third ventriculostomy and biopsy can be performed through the same burr hole trephination. Limitations of this technique are given by the size of the foramen of Monro and the height of the third ventricle as well as by the bending angle of the instruments (40-50 degrees).

Biopsy↗
PubMed1984

[A new material in neurosurgery].

A new alcoholic prolamine solution is now available (ETHIBLOC, supplied by Ethicon, Norderstedt) which can be used in neurosurgery for a variety of purposes. This material hardens quickly in an aqueous medium. Animal experiments have not shown any damaging action on the brain, meninges, or bone. The excellent tolerance of the material was seen in a total of 22 patients operated on with the help of Ethibloc. It is particularly well suited for closing frontal CSF fistulas, incised frontal sinuses, and for rearranging or shunting in case of cerebral vascular deformities. It can also be used as a carrier of antibiotics in osteomyelitis, for covering up minor defects of the dura mater, for dura sealing, and for closing the bone after trephination. The preparation is transformed completely to connective tissue within a period of 40 to 90 days. New techniques of surgery are described which have become possible by the use of Ethibloc.

Animals↗
PubMed1984

[Filtering trepano-trabeculectomy with sponge-like scar].

Filtering trepanotrabeculectomy (TTE) is a modification of the operation after J. Fronimopoulos. A triangular scleral flap is created which is approximately one-half as thick as the sclera. Trepanation is performed with a 2 mm trephine. The scleral edge of the trepanation opening is heat-cauterized. Filtering TTE was performed on 36 eyes - 17 with glaucoma simplex, 16 with congestive glaucoma, and 3 with secondary glaucoma. Fifty percent of the eyes thus treated had narrow chamber angles. Regulation of IOP was achieved in 96% of the cases. Intraoperative and postoperative complications were rare, with the exception of choroidal detachment (13.8%). The fundamental requirement for regulation of IOP is a well-formed, active filtering bleb, developing as a result of the spongelike scar which is protected by the scleral flap. The scar creates a connection between the anterior chamber and the subconjunctival space.

Cautery↗
PubMed1983

[Results of sclera-laminating goniotrephination in neovascular glaucoma].

Sclera-laminating goniotrepanation is a modification of the Elliot-Fronimopoulos operation. In this procedure the scleral flap is removed, so that a shallow depression is formed in the sclera; this helps to prevent an ectatic bleb. No cicatrization of the trephine hole was observed in the authors' cases. The modification is only used by them in glaucoma cases with poor prognosis. Forty-six patients, 39 of whom were suffering from neovascular glaucoma associated with occlusion of the central retinal vein or diabetic retinopathy, underwent the operation and the results were followed up. As far as regulation of intraocular pressure and elimination of pain are concerned, the results were encouraging. Severe hemorrhage into the anterior chamber without spontaneous absorption only occurred in 2 cases.

Adult↗
PubMed1982

[An objective rapid testing method for viability of corneal endothelium after conservations (author's transl)].

An objective procedure for assessing damage to corneal endothelium is described; it is based on photometrical determination of the dye toluidine blue absorbed by damaged cells. This inexpensive quick test is suitable both for preoperative assessment of grafts and for checking procedures for cornea conversation. The use of the peripheral region of the endothelium enables the remaining central trephined portion in transplantations. When this procedure was used to conserve pig corneae in the moist chamber there was a slight increase in damage by the ninth day. By the 17th day all the endothelial cells were damaged.

Animals↗
PubMed1982

[Vitreous - loss less dangerous with the microstripper (author's transl)].

The author presents a simple surgical device which enables all ophthalmic surgeons to manage vitreous loss in cataract surgery or perforating injuries in a safer and simpler way, and with fewer postoperative complications. The instrumentarium has the following specifications: perfectly cutting vitrectomy microinstrument. Mechanical device for repeated use of the cutting edge of the trephine. The instrument set is ready for use less than 1 minute. The same instrument can be used for several other purposes in anterior and posterior segment surgery, especially for special problems in pars plana vitrectomy.

Cataract Extraction↗
PubMed1980

[Differential diagnosis of postoperative glaucoma following iridectomy and filtering procedures (author's transl)].

The various causes of elevated intraocular pressure following glaucoma surgery are described. One has to differentiate between failures after peripheral iridectomy (Table 1) and those following filtering interventions. The clinical picture of a postoperative narrow-angle glaucoma must be analyzed carefully; it may be due to pupillary block, plateau-iris syndrome or even to a ciliary block (malignant glaucoma). The failure of filtering procedures may be due to mechanisms blocking the trephination opening, cicatrization of the conjunctiva or a ciliary block. The diagnosis criteria of the different conditions and the respective therapeutic measures are outlined.

Diagnosis, Differential↗
PubMed2002

Wavelet analysis for corneal topographic surface characterization.

PURPOSE: To demonstrate a mathematical method for multiscalar decomposition of discrete corneal topography height data into a space-scale space using wavelet analysis techniques, and to demonstrate the clinical applicability of these computations in the postkeratoplasty cornea. METHODS: Fifty patients with either Fuchs' dystrophy (n = 20) or keratoconus (n = 30) were seen preoperatively, at 3 months, at 1 year (before suture removal) and again at 19 +/- 3 months (after suture removal) following nonmechanical trephination with an excimer laser for penetrating keratoplasty. Patients were assessed using corneal topography analysis (TMS-1), subjective refraction, and best-corrected visual acuity (VA) at each interval. Two-dimensional biorthogonal wavelets with the order 6.8 at the scales j = 1-4 revealed the following parameters: root-mean square (RMSDEV) and mean absolute (MEANDEV) deviation and maximum absolute height of the peaks or pitches (MAXPEAK) relative to the reference surface specified with the approximation component of scale j = 4. RMSDEV was correlated with the VA at various follow-up intervals. The multiscalar basis components: roughness, waviness and form were separated and recovered from the wavelet soft thresholding techniques. Peaks and pits within the three-dimensional corneal surface topography were detected and localized using the wavelet hard thresholding techniques. RESULTS: In patients with keratoconus, the RMSDEV and the MEANDEV increased from 4.31 +/- 1.25/5.98 +/- 1.88 microm preoperatively to the 3 months follow-up (4.98 +/- 1.41/6.92 +/- 2.16 microm) and thereafter decreased continuously to the end of the follow-up (1.87 +/- 0.63/2.63 +/- 1.07 microm), whereas in Fuchs' dystrophy the respective values started at a higher preoperative level (6.36 +/- 1.24/7.20 +/- 2.64 microm) and decreased continuously over time (2.73 +/- 1.10/3.71 +/- 1.05 microm after suture removal). In the keratoconus group, the MAXPEAK was increased at the 3 month postoperative exam (8.78 +/- 2.29 microm) when compared to the preoperative value (6.55 +/- 2.56 microm); however, it decreased again and returned to the preoperative level after one year (6.34 +/- 2.12 microm after suture removal). In Fuchs' dystrophy, the MAXPEAK was unchanged preoperatively (8.26 +/- 2.83 microm) to the 3 months follow-up, but decreased continuously to the end of the follow-up period (4.57 +/- 1.36 microm). The RMSDEV was significantly lower in keratoconus than in Fuchs' dystrophy preoperatively (P = 0.01) and after suture removal (P = 0.005) and correlated inversely with VA preoperatively (R = -0.53, P = 0.04/R = -0.69, P = 0.02), at the 1 year exam (R = -0.61, P = 0.02/R = -0.52, P = 0.05) and after suture removal (R = -0.73, P = 0.01/R = -0.66, P = 0.025) in keratoconus/Fuchs' dystrophy. CONCLUSIONS: The use of wavelet analysis can provide significant clinical information by separating the raw data into the parameters: "roughness", "waviness", "form" and various multiscalar peaks and pits. The RMSDEV, a quantitative measure for corneal irregularity, can be used as a new approach for the prediction of potential visual acuity after penetrating keratoplasty. The decomposition of the surface elevation into fundamental components is crucial for a subsequent mathematically based extraction of clinical parameters or for topography-based flying-spot ablation of irregular corneal astigmatism.

Aged↗
PubMed2002

Three-axis ellipsoidal fitting of videokeratoscopic height data after penetrating keratoplasty.

PURPOSE: After penetrating keratoplasty corneal topography tends to be irregular and the fitting of spectacle glasses or contact lenses may be difficult. The purpose of this study was to demonstrate a mathematical method for approximation of discrete corneal topography height data with an ellipsoid for better appreciation of the clinical outcome after PK. PATIENTS AND METHODS: In 50 eyes (30 keratoconus, 20 Fuchs' dystrophy) penetrating keratoplasty was performed using nonmechanical trephination with the excimer laser 193 nm. Main outcome measures were objective corneal astigmatism (regular keratometry, corneal topography (TMS-1)), subjective refraction and best-corrected visual acuity (VA) in a fixed postoperative gate 3 and 12 month postoperatively and after suture removal. An approximation algorithm was applied for fitting a general ellipsoidal surface (not rotationally symmetric) to raw corneal topography height data. A set of parameters (meridional power, axis and asphericity) were calculated. The root mean square error (RMS) was determined between raw topography power data and the ellipsoidal model surface within an apical distance of 3 mm. The cylinder of subjective refraction was correlated with the keratometric readings, the Simulated Keratometry (SimK) of the topography system and the respective parameters of the model surface. RESULTS: The amount of the SimK cylinder yielded higher values than keratometry and the ellipsoidal fit; subjective refraction yielded the lowest value at each follow-up interval. The ellipsoidal fit showed the best correlation to the refractive cylinder at all follow-up stages (p = 0.04 at 3, p = 0.01 at 12 months and p = 0.002 after suture removal). The axis of the best ellipsoidal fit showed a significant correlation with the axis of the refractive cylinder at all follow-up intervals (p = 0.02 at 3 months, p = 0.01 before suture removal and p = 0.002 after suture removal). The axis of the keratometric cylinder showed a mild correlation at all follow-up examinations (p = 0.05 at 3 months, p = 0.02 before suture removal and p = 0.04 after suture). The cylinder of the topographic modeling system, however, showed a significant correlation with the refractive cylinder axis only after suture removal (p = 0.04). The paracentral corneal power of SimK (45.9D at 3 months, 44.4D at 12 months and 43.0D after suture removal) exceeded the respective values of conventional keratometry (43.1D at 3 months, 42.9D at 12 months and 41.7D after suture removal) and the ellipsoidal fit (43.3D at 3 months, 43.0D at 12 months and 41.8D after suture removal). The corneal asphericity from the ellipsoidal fit reached an approximately spherical shape in radial direction (A = 1.0) in the initial time period after penetrating keratoplasty, remained stable before suture removal and decreased significantly (p = 0.02) to a final value of A = 0.86 indicating a (normal) prolate shape of the cornea. The approximation error between the raw corneal topography height data and the best ellipsoidal fit model surface was nearly unchanged before suture removal (1.8 +/- 0.7 microm at 3 months and 1.9 +/- 1.1 microm at 12 months, p = 0.30) and decreased significantly to the examination after suture removal (0.9 +/- 0.5 microm, p = 0.01). CONCLUSIONS: The approximation of corneal topography height data with an ellipsoidal model surface renders reconstruction of clinically relevant corneal topography parameters including corneal asphericity. Even in markedly irregular corneal surfaces, such as after PK, the correlation of amount/axis of refractive cylinder with the model surface parameters is more accurate than with respective SimK values of corneal topography analysis.

Adult↗