Biomedical subjects

Berthold Seitz

Publications and source records attributed to Berthold Seitz.

At least 73 records · Page 4Linked to original sources

PubMed2003

[Current State of Corneal Pathology in Germany: Results of a Survey Conducted Among Members of the Cornea Section of the German Ophthalmological Society (DOG)].

BACKGROUND: The current situation of corneal pathology is widely unknown. Especially, there are no data available how corneal tissue is processed after penetrating keratoplasty. MATERIAL AND METHODS: In November 2002 a questionnaire with 15 questions was sent to all registered members of the cornea section of the German Ophthalmological Society (DOG) ( www.sektionkornea.org ) via email. Only one answer per eye clinic was allowed. RESULTS: Answers were obtained from 40 eye hospitals in which 3070 penetrating keratoplasties had been performed in 2001. 90 % of the surgeons believe that ophthalmopathological investigations of excised corneal specimens are always or at least in some cases important, and 80 % examine 75 to 100 % of all corneal buttons. However, the corneoscleral rim is investigated only exceptionally. 45 % of all corneal buttons are examined by a pathologist within the hospital while 33 % of the corneal specimens are investigated by an ophthalmopathologist in an ophthalmopathological laboratory. In most cases the hospital itself has to bear the cost. Clinics with a high number of corneal transplantations do not differ from the average regarding the fate of corneal buttons. Morphological investigations and publications concerning the cornea are more frequent when an ophthalmopathological laboratory is available in the hospital. CONCLUSIONS: For most eye hospitals performing keratoplasties, the histopathological examination of excised corneal buttons is very important. It is carried out to a large extent by pathologists, but specialised ophthalmopathological laboratories are consulted when a profound expertise is needed. Thus, this survey is an argument for the preservation of these laboratories too. Based on the obtained data and on several comments by the section members initiatives to intensify histopathological investigations of excised corneal specimens should be undertaken.

Attitude of Health Personnel↗

PubMed2003

Annular crystalline keratopathy in association with immunoglobulin therapy for pyoderma gangrenosum.

PURPOSE: To report on a patient with a clinical presentation of annular crystalline keratopathy after immunoglobulin therapy for pyoderma gangrenosum. METHODS: Case report of a 6-year-old boy with biopsy-proven history of pyoderma gangrenosum who had undergone several cycles of systemic immunoglobulin therapy. The literature on ocular manifestations associated with pyoderma gangrenosum was reviewed. RESULTS: One year after the last cycle, the patient complained of the sudden onset of photophobia. Slit-lamp biomicroscopy revealed bilateral symmetric crystalline deposits in an annular region of the cornea. Because visual acuity was not reduced, specific therapy was not initiated. Symptoms could be reduced by the prescription of medical edged filter lenses. CONCLUSIONS: Annular crystalline corneal deposits may be associated with immunoglobulin therapy or represent a hitherto unknown ocular complication of pyoderma gangrenosum.

Child↗

PubMed2003

Penetrating keratoplasty for endothelial decompensation in eyes with buphthalmos.

PURPOSE: To evaluate the prognosis and complications of penetrating keratoplasty (PKP) for corneal decompensation in eyes with buphthalmos and to analyze the risk factors for graft failure. PATIENTS AND METHODS: Clinical records of 13 adult and three pediatric patients who underwent PKP for endothelial decompensation with a previous diagnosis of congenital glaucoma of a total of 3,663 corneal transplantations performed in our department between January 1987 and December 2001 were reviewed retrospectively. During the study period, a total of 33 PKPs was performed in 20 eyes with buphthalmos. The median age of the patients at the time of PKP was 39 years (range, 3 to 72). All patients had a history of intraocular surgery, including multiple glaucoma surgeries, cataract extraction, and PKP. The impact of pre-, intra-, and postoperative factors on graft failure and duration of graft clarity was analyzed. RESULTS: Fifty-five percent (11/20) of the eyes received only one graft, 25% (5/20) received two, and 20% (4/20) received three grafts. During a mean follow-up of 87.2 months (range, 4.5-72), graft failure occurred in 18 of 33 grafts (54%). Seven (7/18, 39%) had immunologic graft rejection, and 11 (11/18, 61%) had nonimmunologic graft failure. At the end of the follow-up, 75% (15/20) of the eyes had clear grafts. Duration of graft clarity was found to be significantly shorter in regrafts compared with that of primary grafts (27.0 +/- 27.7 versus 56.4 +/- 41.0 months, p= 0.02). After PKP, intraocular pressure (IOP) was uncontrolled in 12 (12/33, 36%) grafts. Nine of 20 eyes (45%) required an average of 3.2 cyclodestructive procedures per eye for pharmacologically resistant elevated IOP. The final postoperative vision improved in 70% (14/20) of the eyes and the best visual acuity postoperatively (75% > or =20/400) was significantly better than the preoperative visual acuity (25% > or =20/400, p= 0.0001). CONCLUSIONS: Endothelial decompensation due to congenital glaucoma is a very rare indication for PKP. The incidence of graft failure is high, and nonimmunologic reasons are the leading causes of graft failure in this high-risk population. Visual acuity can be significantly improved but is usually still very limited by advanced glaucomatous optic nerve damage and amblyopia. Efficient control of IOP before and after PKP is mandatory in eyes with buphthalmos to avoid graft failure and progress of glaucomatous optic nerve atrophy.

Adolescent↗

PubMed2003

Impact of preoperative corneal curvature on the outcome of penetrating keratoplasty in keratoconus.

PURPOSE: To assess the impact of the patient's preoperative corneal curvature on the refractive outcome after penetrating keratoplasty (PK) in keratoconus before and after suture removal. PATIENTS AND METHODS: In this retrospective cross-sectional clinical study, 236 keratoconus patients (mean age 37 +/- 11 years) were divided into four groups based on their preoperative keratometric (K-) readings: group 1, <50 diopters (D) (n = 24); group 2, <60 D (n = 52); group 3, > or =60 D (n = 101); group 4, irregular corneal shape with unmeasurable K-reading (n = 59). An 8.0/8.1-mm central round PK was performed using 193 nm Meditec excimer laser trephination along metal masks with eight "orientation teeth/notches." A 16-bite double running cross-stitch suture was applied in all cases. Postoperative examinations were performed before removal of the first suture (ie, 12 months) and after removal of the second suture (ie, 18 months). The outcome measures included central power (C-power), keratometric astigmatism (AST), surface regularity index (SRI), surface asymmetry index (SAI), spherical equivalent (SEQ), refractive cylinder (Cyl), and best corrected visual acuity (BCVA). In addition, the regularity of Zeiss keratometry mires was classified semiquantitatively (0, regular; 1, mildly irregular; 2, moderately irregular; 3, unmeasurable). RESULTS Before/after suture removal, median C-power was 43.4/43.3 D; AST was 3.0/3.0 D; SAI was 0.6/0.6; SRI was 0.9/0.9; Cyl was 2.5/2.5 D; BCVA was 0.7/0.7. After suture removal, the percentage of regular keratometry mires increased from 37% to 61%. Comparisons among the four groups revealed no significant differences for any parameters tested either before or after suture removal. CONCLUSIONS With laser trephination and a double running suture, the refractive and visual outcome of PK for keratoconus seems to be independent on the patient's preoperative corneal curvature or irregularity. Suture removal did not effect an increase of corneal astigmatism but did increase the proportion of regular keratometry mires. Thus, our policy of not performing PK in keratoconus eyes before the patient becomes contact lens intolerant is well supported.

Adolescent↗

PubMed2003

Q-Switched 2.94-microm Er:YAG laser trephination with convergent and divergent cut angles for penetrating keratoplasty.

PURPOSE: To study the morphologic properties of perpendicular (P), convergent (C), and divergent (D) cut angles using different speeds of rotations during donor and recipient nonmechanical trephination for experimental penetrating keratoplasty. METHODS: With a Q-switched 2.94-microm Er:YAG laser corneal trephination was performed in 150 enucleated porcine eyes using ceramic open masks with 8 "orientation teeth/notches" and an automated globe rotation device allowing different cut angles [0 degree (P), 10 and 20 degrees (C and D)] toward the optical axis and variation of the rotation speed [3, 7, and 11 rotations per minute (rpm)]. The regularity of the cut (I, regular; II, slightly irregular; III, irregular) was assessed by light microscopy. The area of thermal damage and the number and size of "spikes" in the stroma at the superficial, intermediate and deep level of the excision were analyzed using digital images and the Optimas image processing software. RESULTS: The regularity of the cut was classified as I in 42%/22% of donor/recipient and as II in 41%/56%, respectively. The thermal damage was least expressed with D20 degree cut angle and donor mask (P < 0.01). With all cut angles and speeds of rotation, thermal damage at the deep level of excision was significantly smaller (P < 0.01). With different speeds of donor rotations, the thermal damage showed no significant difference. With recipient trephination, the thermal damage at the deep level was greatest with 7 rpm (P < 0.01). The number and size of spikes of thermal damage with donor and recipient masks were significantly smaller in the deep stroma (P < 0.01). CONCLUSIONS: Q-switched Er:YAG laser trephination with appropriate settings results in low thermal damage zones at the cut margin. Different cut angles and speeds of trephination may affect the cut performance and quality of the excision. In our study, low rotation speed and divergent donor cut angles showed the best results. The cut quality and the small thermal damage with the Q-switched 2.94-microm Er:YAG laser seem to be tolerable for corneal trephination. Therefore, this modality may be a low-cost, easy-to-handle alternative for nonmechanical corneal transplantation in humans.

Cornea↗

PubMed2002

Risk factors for corneal allograft rejection: intermediate results of a prospective normal-risk keratoplasty study.

PURPOSE: To analyze the incidence of and possible risk factors for endothelial corneal allograft rejection in a well-defined population following penetrating normal-risk keratoplasty. METHODS: Since 1996 a longitudinal prospective study has been conducted to analyze the results of normal-risk penetrating keratoplasty. All patients underwent a standardized protocol of follow-up treatment and examinations in our institution. Diagnosis of corneal endothelial rejection was based on slit-lamp biomicroscopy and laser flare photometry. Data were analyzed using a proportional hazard model for censored data (Cox model), and Kaplan-Meier survival curves. The following parameters were analyzed: age, gender, atopic dermatitis, dry eye symptoms of the recipient; surgeon, graft diameter, post-mortem time, storage time and graft preservation method; and duration of postoperative epithelial defects. RESULTS: Between 1996 and May 2001, 397 patients were recruited and followed with a median follow-up of 18 months. Episodes of endothelial graft rejection were observed in 22 patients (5.5%; 18 eyes with acute diffuse episodes and 4 eyes with chronic focal rejection episodes). In addition, 12 eyes (3%) showed isolated small keratic precipitates ("graft rejection suspects"). All but one graft regained clarity after topical and systemic steroid treatment. Most episodes occurred 11-18 months postoperatively. The percentage of grafts without any episode of endothelial allograft rejection was 95% after 12 months, 89% after 18 months, and 86.5% after 24 months. The following factors were associated with graft rejection: atopic dermatitis (P=0.021), clinically manifest tear insufficiency (P=0.007), and short duration of graft storage (P=0.008). No significant correlation was detected for the remainder of the analyzed factors (P>0.05). CONCLUSION: The incidence of episodes of corneal endothelial allograft rejection following normal-risk keratoplasty was 13.5% within the first two postoperative years. However, the frequency of irreversible immunologic graft failure (3 per thousand) was lower than reported in the literature. Patients should be regularly followed up for at least 18 months postoperatively. Patients with underlying atopic dermatitis or dry eyes should receive special ophthalmological care.

Corneal Diseases↗

PubMed2002

Corneal endothelial cell loss after nonmechanical penetrating keratoplasty depends on diagnosis: a regression analysis.

PURPOSE: To assess the impact of diagnosis on corneal endothelial cell loss after nonmechanical penetrating keratoplasty (PK) with regression models. METHODS: Five hundred eighty-nine eyes [273 with keratoconus (group I; PK only), 187 with Fuchs' endothelial dystrophy (group II; 77 PK only and 110 triple procedures) and 129 with bullous keratopathy (group III; 115 pseudophakic and 14 aphakic eyes)] were included in this prospective study. The time course of the endothelial cell density after PK was assessed by specular microscopy. Endothelial cell density was analyzed in cross-sectional fashion at 6 and 24 months follow-up and in longitudinal manner (follow-up 2.4+/-1.8 years) with linear and exponential regression models (minimizing the residuum between observed and predicted endothelial cell count). Donor age, post-mortem time, storage time and ratio of organ-cultured to short-term-preserved donor corneas did not differ significantly between groups of patients. RESULTS: In a cross section, endothelial cell density in group I / group II / group III decreased from 1,959+/-499 / 1,524+/-528 / 1,526+/-670 cells/mm(2)to 1,617+/-553 / 1,222+/-520 / 1,063+/-384 cells/mm(2) (P=0.06 / 0.04 / 0.005). Endothelial cell count was significantly higher in group I than in group II (P=0.048) and significantly higher in group II than in group III (P=0.01) at 24 months. In the linear regression model, cell count decreased in group I / group II / group III by 136+/-465 / 241+/-374 / 421+/-484 cells annually. In the exponential regression model, cell count decreased in group I / group II / group III by 2.9+/-28.0% / 11.2+/-21.8% / 19.3+/-29.4% annually. Cell loss was highly significantly lower in group I than in group II ( P<0.0001) and highly significantly lower in group II than in group III (P<0.0001). CONCLUSION: Endothelial cell loss seems to be least pronounced after PK in keratoconus (2.9%), followed by Fuchs' dystrophy (11.2%) and bullous keratopathy (19.3%). These differences between diagnoses indicate migration of endothelial cells along a density gradient after PK.

Adolescent↗

PubMed2002

Temporal contrast sensitivity using full-field flicker test (Erlangen flicker test) in patients after penetrating keratoplasty.

BACKGROUND: The purpose of this study was to evaluate the feasibility of temporal contrast sensitivity testing using full-field flicker stimulation in patients after penetrating keratoplasty (PK) and to assess whether this method is influenced by postoperative corneal topographic changes. METHODS: Forty-five patients (age 46.5+/-14.2, median 47 years) who had undergone PK and 194 age-matched controls were included in this study. The postoperative interval was 11.8+/-10.2 months (median 9 months). Patients with pre-existing glaucoma or any postoperative intraocular pressure elevation were excluded. The indications for PK were keratoconus in 54% of cases, Fuchs' dystrophy in 38% and stromal dystrophies in 8%. Temporal contrast sensitivity was determined with sinusoidal flickering light (37.1 Hz) of constant mean photopic luminance (10 cd/m(2)) presented in a full-field bowl with an increasing threshold strategy. RESULTS: Mean temporal contrast sensitivity did not differ between patients after PK (1.49+/-0.13, range 1.26-1.78, confidence interval 1.45-1.53) and controls (1.55+/-0.17, range 1.16-1.98, confidence interval 1.47-1.51). No significant correlation between temporal contrast sensitivity and visual acuity could be found in patients after PK or in normals ( r<0.2, P=0.3). In patients after PK, temporal contrast sensitivity was statistically independent of keratometric astigmatism ( r=0.3, P=0.7), topographic astigmatism ( r=0.3, P=0.4), spherical equivalent ( r=0.07, P=0.7), central corneal thickness ( r=-0.06, P=0.7) and time since operation ( r=-0.07, P=0.6). CONCLUSIONS: Temporal contrast sensitivity using full-field flicker stimulation seems to be feasible in patients after PK and does not depend on topographic changes of the cornea. The results indicate that the full-field flicker test may be helpful as a supplementary means of detecting early glaucoma caused by ocular hypertension in patients after PK.

Adult↗

PubMed2002

Corneal endothelial cell density and pachymetry measured by contact and noncontact specular microscopy.

PURPOSE: To determine the endothelial cell density and thickness of normal human and postkeratoplasty corneas with contact specular microscopy and to compare these measurements with those obtained by noncontact specular microscopy. SETTING: Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. METHODS: The central corneal endothelial cell density and thickness were determined in 65 healthy eyes of 39 patients with a mean age of 71 years +/- 12 (SD) and in 50 corneal grafts of 41 patients with a mean age 53 +/- 17 years using noncontact (Topcon SP-2000P, Topcon Corp.) and contact (EM-1000, Tomey) specular microscopes. Appropriate conversion factors were used for accurate cell count comparison. RESULTS: The mean cell count of the normal corneas was 2445 +/- 425 cells/mm(2) measured by noncontact specular microscopy and 2471 +/- 393 cells/mm(2) measured by contact specular microscopy (P =.70). After penetrating keratoplasty, the mean cell density was 1610 +/- 499 cells/mm(2) and 1584 +/- 469 cells/mm(2), respectively (P =.88). Significantly lower thickness was measured with the noncontact specular microscope than by contact pachymetry in normal eyes (543 +/- 46 micro m and 642 +/- 42 micro m, respectively) and postkeratoplasty eyes (538 +/- 61 micro m and 627 +/- 48 micro m, respectively) (P <.0001). CONCLUSION: To determine endothelial cell density, contact and noncontact specular microscopy may be used interchangeably. However, for the combined measurement of endothelial cell density and pachymetry, the use of the same specular microscope is recommended for long-term patient follow-up.

Adult↗

PubMed2002

Short-term blood-aqueous barrier breakdown after implantation of the 1CU accommodative posterior chamber intraocular lens.

PURPOSE: To quantify intraocular inflammation after phacoemulsification with implantation of an accommodative posterior chamber intraocular lens (IOL). SETTING: Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany. METHODS: Twenty cataractous eyes of 20 patients without preexisting blood-aqueous barrier (BAB) deficiencies or previous intraocular surgery were included in this study. The mean age of the patients was 64.6 years +/- 16.0 (SD). A single surgeon performed phacoemulsification through a superior sclerocorneal tunnel incision and implantation of a 1CU IOL (HumanOptics AG) though a 3.2 mm incision. The haptics of the single-piece acrylic 1CU lens are designed for anterior optic movement following ciliary muscle contraction. The postoperative treatment was standardized. Postoperative BAB breakdown was quantified by laser flare photometry (FC-1000, Kowa) at 1 day, 1 and 4 weeks, and 3 and 6 months. RESULTS: The mean aqueous flare was 6.3 photons/ms +/- 3.0 (SD) (range 4.0 to 12.2 photons/ms) 1 day postoperatively, with 64% of patients having normal aqueous flare values (<8.0 photons/ms). One week after surgery, the mean aqueous flare was 5.3 +/- 2.8 photons/ms (range 2.0 to 10.5 photons/ms). Four weeks postoperatively, aqueous flare was normal in all patients and remained stable below the normal limit for up to 6 months (mean 3.3 +/- 1.2 months; range 2.0 to 5.4 months). The number of aqueous cells did not increase at any follow-up and was normal in all eyes. No postoperative complications such as fibrin formation, synechias, macrophages on the IOL optic, or endophthalmitis were observed. CONCLUSIONS: Phacoemulsification with implantation of the 1CU accommodative IOL led to minimal and short-lasting BAB alteration. No signs of persistent inflammation or pigment dispersion were detected.

Accommodation, Ocular↗

PubMed2002

[Impact of cataract surgery on intraocular pressure after filtering operation due to primary open angle glaucoma and secondary glaucoma in pseudoexfoliation syndrome].

PURPOSE: To analyse the impact of cataract surgery after filtering operation on the intraocular pressure (IOP) due to primary open angle glaucoma (pOAG) versus secondary open angle glaucoma in pseudoexfoliation syndrome (PEX). The regulation of IOP was evaluated on the basis of criteria of advanced glaucoma intervention study (AGIS). PATIENTS AND METHODS: Retrospectively 95 eyes of 95 patients (53 x pOAG, 36 x clear cornea approach [group 1] and 17 x corneoscleral tunnel [group 2]; 42 x PEX, 30 x clear cornea approach [group 3] and 12 x corneoscleral tunnel [group 4]) were included. The IOP and antiglaucomatous eye drops were analysed before filtering operation, before cataract surgery and on average 33 months after cataract surgery. RESULTS: In all groups there was a significant reduction of IOP after filtering operation by 8.7 mm Hg on average and no significant difference of IOP before and after cataract surgery. At no time there was a significant difference in IOP between the four subgroups. According to criteria of the AGIS study 34 % of group 1, 29 % of group 2, 36 % of group 3 and 17 % of group 4 had an IOP lower than 14 mm Hg before cataract surgery. After cataract surgery only 31 % of group 1, 18 % of group 2, 13 % of group 3 and 8 % of group 4 met this criterion. CONCLUSION: On first glance sequential cataract surgery after filtering operation seems to have no clinically relevant impact on the IOP, neither with regard to the type of glaucoma nor in respect of the approach for cataract surgery. However, if IOP is evaluated based on the criteria of the AGIS, primary open angle glaucoma with clear cornea approach appears to yield superior results in contrast to secondary open angle glaucoma in pseudoexfoliation syndrome with corneoscleral tunnel concerning the regulation of intraocular pressure.

Aged↗

PubMed2002

[Pterygoid corneal dystrophy].

BACKGROUND: Pterygia are characterised by progressive growth of fibrovascular tissue over the nasal limbus towards the corneal center with the loss of Bowman's layer. We report on three patients with bilateral symmetrical affection of the nasal and temporal limbus in one family. PATIENTS: A 81-year-old female, her 61-year-old son and her 37-year-old grandson presented with a familiar form of pterygium-like corneal changes. Remarkable was the bilateral symmetrical affection with involvement of the nasal and temporal limbus. Both male patients had multiple excisions (including lamellar keratoplasty) but suffered from persistent recurrences, which led to sustained reduction of the visual acuity. Histological examination revealed typical elastoid degeneration of collagen fibres. CONCLUSION: We assume autosomal dominant heredity with varying expression for this "pterygoid corneal dystrophy". It does not seem to differ histologically from normal pterygia, but recurrences appear to be more frequent and more aggressive.

Adult↗

PubMed2002

[Pitfalls of IOL power prediction after photorefractive keratectomy for high myopia -- case report, practical recommendations and literature review].

BACKGROUND AND PURPOSE: Published experience with eyes after keratorefractive correction of myopia indicates that insertion of the average keratometric readings into standard IOL power predictive formulas will frequently result in substantial undercorrection and postoperative hyperopic refraction or anisometropia after cataract surgery depending on the amount of myopia corrected previously. The purpose of this paper is to discuss the accentuated differences of various approaches to minimize IOL power miscalculations by describing a case report of a patient with excessive myopia as well as a review of the literature. PATIENT AND METHODS: A 50-year old lady presented for cataract surgery on her left eye after having PRK seven years ago elsewhere (refraction - 25.5 - 3.0/20 degrees, central keratometric power 43.0 diopters [D]). Central power before cataract extraction was measured to be 35.5 D (Zeiss Keratometer) and 36.5 D (TMS-1 topography analysis) and refraction was - 3.0 D (before onset of index myopia). Orbscan slit scanning topography analysis displayed an anterior surface power of 36.8 D and a posterior surface power of - 9.3 D. Total axial length was 31.93 mm (optical biometry using Zeiss IOL-Master). The contralateral eye after PRK suffering from a comparable excessive myopia had required an exchange of the IOL implant because of intolerable anisohyperopia of + 6.0 D after primary cataract extraction elsewhere. RESULTS: Corrected corneal power values for the left eye were calculated as follows: (1) spherical equivalent (SEQ) change at spectacle plane 19.0 D, (2) SEQ change at corneal plane 26.2 D, (3) separate consideration of anterior and posterior curvature 27.5 D, (4) consideration of the IOL power misprediction on the fellow eye 29.5 D, (5) subtraction of 24 % of the SEQ change at the spectacle plane from the actually measured keratometry value 29.7 D, (6) clinical estimate from regression analysis performed earlier 30.5 D, (7) change of anterior surface power 34.5 D. Deciding for a presumably "real" corneal power of 28.0 D the Haigis formula was used to aim for - 2.0 D since the patient preferred to read uncorrected. Thus, a 21.0 D IOL was implanted uneventfully in the capsular bag. The stable refraction postoperatively was - 3.5 - 1.0/20 degrees and visual acuity increased to 20/30. Therefore, the "real" power of that cornea must have been around 30 D. CONCLUSIONS: After corneal refractive surgery, various techniques to determine the current corneal power should be compared and the value around which results tend to cluster should be relied on to avoid hyperopia after cataract surgery with lens implantation. In those cases where keratometry and refraction before PRK/LASIK are available, the gold standard is still to subtract the change of the SEQ at the corneal plane from the preoperative central keratometric power, although in the present case report the subtraction of 24 % of the SEQ change at the spectacle plane from the measured corneal power value seemed to produce the best result. Pure subtraction of the SEQ change at the spectacle plane from the corneal power value before refractive surgery has to be avoided in eyes with excessive myopia. The most reliable corrected power value should be inserted in more than one modern third-generation formula (such as Haigis, Hoffer Q, Holladay 2, SRK/T) and the highest power IOL should be implanted. In all instances, the cataract surgeon has to make sure that the corrected K-reading is not wrongly re-converted within the IOL power calculation formula used.

Corneal Topography↗

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↗

PubMed2002

Long-term follow-up of intraocular pressure after penetrating keratoplasty for keratoconus and Fuchs' dystrophy: comparison of mechanical and Excimer laser trephination.

PURPOSE: In the literature, the incidence of "secondary glaucoma" after penetrating keratoplasty (PK) is reported to range from 10% to 42%, depending on the diagnosis and the complexity of surgery. The purpose of this study was to assess the impact of the trephination method and simultaneous cataract surgery on the early and long-term intraocular pressure (IOP) after PK in eyes without previous surgery and glaucoma. METHODS: Inclusion criteria for this prospective, randomized, longitudinal clinical study were (1) one surgeon (G.O.H.N.), (2) primary central PK, (3) Fuchs' dystrophy (7.5/7.6 mm) or keratoconus (8.0/8.1 mm), and (4) 16-bite double running diagonal suture. Exclusion criteria were (1) previous intraocular surgery, (2) preoperative glaucoma, and (3) postoperative trauma or endophthalmitis. In 170 patients (mean age, 51 +/- 18 years), PK was performed with use of either a 193-nm excimer laser (Excimer patients) along metal masks with eight orientation teeth/notches (50 keratoconus, 32 Fuchs') or motor trephination (Control patients; 53 keratoconus, 35 Fuchs'). In 27% of Excimer patients and 29% of Control patients a triple procedure was performed. The perioperative systemic acetazolamide application and the postoperative topical steroid therapy were standardized. RESULTS: Maximal IOP during the first week after PK was 15.7 +/- 3.6 mm Hg (7% > 21; maximum, 28) in the Excimer group and 16.2 +/- 3.5 mm Hg (7% > 21; maximum, 30) in the Control group. During a mean follow-up of 3.4 +/- 1.3 years (maximal, 6.0), an IOP >21 mm Hg and/or application of topical antiglaucomatous medication was documented in 9% of Excimer patients versus 15% of Control patients (p = 0.32), in 15% of Fuchs' dystrophy versus 11% of keratoconus cases (p = 0.41), and in 11% of PK-only versus 15% of triple-procedure cases (p = 0.68). The IOP elevation started an average of 3.7 +/- 2.8 months (1 week to 9 months) after PK and ended an average of 6.5 +/- 3.1 months (6 weeks to 12 months) after PK. Mean maximal IOP during follow-up was 16.6 +/- 3.5 mm Hg (12-38) in the Excimer group and 17.2 +/- 3.2 mm Hg (12-30) in the Control group. Only one patient, who had undergone a triple procedure for Fuchs' dystrophy and had an elevated IOP, needed topical medication, from 32 months after PK to the end of follow-up. Glaucomatous optic disc damage was clinically detected in none of the patients. CONCLUSIONS: Temporary secondary ocular hypertension after PK is rare in eyes with keratoconus or Fuchs' dystrophy without previous surgery. There was no detectable impact from the trephination method, the diagnosis, or simultaneous cataract surgery. With meticulous microsurgical technique, careful suturing, and peripheral iridotomy, the development of secondary glaucoma with disc cupping seems to be the exception.

Adolescent↗

PubMed2002

Changes of posterior corneal astigmatism and tilt after myopic laser in situ keratomileusis.

PURPOSE: The purpose of this study was to assess the changes of posterior corneal astigmatism and tilt after laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness. METHODS: This prospective nonrandomized (self-controlled) comparative trial included 57 eyes from 14 females and 15 males, whose mean age (+/- standard deviation [SD]) at the time of surgery was 33 +/- 9 years (range, 19-53), with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (D). All LASIK procedures were accomplished with the Keratom II Coherent-Schwind excimer laser and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit-scanning corneal topography analysis, and pachymetry were performed before and 3 months after LASIK for myopia (n= 35; -1.00 to -15.50 D [mean, -4.75 +/- 3.07]) or myopic astigmatism (n= 22; sphere, 0.00 to -9.75 D [mean, -4.75 +/- 2.36]; cylinder, -0.75 to -3.50 D [-1.68 +/- 0.86]). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters for detection of asymmetric mechanical deformation of the cornea were derived. Posterior corneal astigmatism and tilt before and after LASIK were compared, and changes in these variables were correlated with the SEQ change (DeltaSEQ) and the residual corneal bed thickness (RBT). RESULTS: The RBT after LASIK ranged from 186 to 373 (mean, 280 +/- 42) microm. Overall, astigmatism (0.19 +/- 0.07 D/0.22 +/- 0.13 D; p= 0.80) and tilt (3.58 +/- 0.35 degrees /3.65 +/- 0.48 degrees; p= 0.61) did not change significantly by 3 months after LASIK. In eyes with RBT < or =250 microm, the average change in astigmatism (0.05 +/- 0.11 versus 0.01 +/- 0.13 D; p= 0.46) and tilt (0.21 +/- 0.45 degrees versus 0.04 +/- 0.55 degrees; p= 0.30) was not greater than in eyes with RBT > 250 microm. Change in astigmatism (p= 0.19) and tilt (p= 0.56) did not correlate with the RBT during LASIK. CONCLUSIONS: Zernike decomposition of topographic height data discloses that no significant asymmetric mechanical deformation of the posterior corneal curvature occurs after myopic LASIK. Further studies with long-term follow-up are needed to clarify whether this symmetry of the posterior corneal surface can indeed be preserved over time after LASIK if the RBT is < 250 microm.

Adult↗

PubMed2002

Superficial corneal effects of experimental nonmechanical penetrating keratoplasty using a Q-switched Er:YAG laser.

PURPOSE: To assess thermal effects of Q-switched Er:YAG laser trephination to corneal epithelium and superficial stroma using different mask types and materials for experimental penetrating keratoplasty. METHODS: Laser trephination was performed in 20 freshly-enucleated porcine eyes (repetition rate 5 Hz, pulse energy 65 mJ, spot size 0.7 mm). We used flat, open-metal and ceramic masks for donor and recipient trephination placed directly onto the corneal surface. Main outcome measures as assessed by light microscopy after PAS staining of 8-microm paraffin sections included: extension of tissue thermal damage at the cut edge in the superficial and basal epithelial layers, the basement membrane and subepithelial stroma, and depth and width of epithelial/stromal involvement in the area of the donor mask contact. RESULTS: The thermal damage in the superficial epithelium was more pronounced in donor (mean extension 61.6 +/- 15.6 microm) than in recipient (29.4 +/- 24.9 microm, p= 0.05) trephination. In donor trephination, thermal damage zone of the superficial epithelial layer was significantly smaller with ceramic than with metal masks (21.0 +/- 23.0 versus 61.6 +/- 15.6 microm, p= 0.014). In contrast, differences at basal epithelial layer (p= 0.44), basement membrane (p= 0.79), and subepithelial stroma (p= 0.2) were not statistically significant. Superficial donor involvement of the cornea adjacent to the paracentral donor mask contact zone was seen neither with ceramic nor with metal masks. CONCLUSION: Superficial corneal alterations adjacent to the mask-cornea contact zone may be minimized by using the Er:YAG laser in a Q-switched mode. Ceramic masks, in contrast to metal masks, further reduce superficial thermal alterations at the cut edge.

Animals↗