Biomedical subjects

Achim Langenbucher

Publications and source records attributed to Achim Langenbucher.

At least 55 records · Page 3Linked to original sources

PubMed2003

Stability of refraction, accommodation, and lens position after implantation of the 1CU accommodating posterior chamber intraocular lens.

PURPOSE: To investigate stability of refraction, anterior chamber depth (ACD), and accommodation up to 12 months after implantation of the 1CU accommodating posterior chamber intraocular lens (PC IOL). SETTING: Department of Ophthalmology, University Erlangen-Nürnberg, Erlangen, Germany. METHODS: In a prospective study, 15 eyes of 15 patients (mean age 62.2 years +/- 13.4 [SD] [range 44 to 86 years]) had phacoemulsification and PC IOL implantation. Distance refraction, accommodative range measured by the near point with an accommodometer, ACD measured with the IOLMaster (Carl Zeiss Meditec), and near visual acuity with best distance correction (Birkhäuser charts at 35 cm) were determined after 3, 6, and 12 months and analyzed for signs of systematic changes. RESULTS: After 3, 6, and 12 months, the mean distance refraction was -0.28 +/- 0.54 diopters (D), -0.29 +/- 0.52 D, and -0.21 +/- 0.54 D, respectively; the mean accommodative range, 1.93 +/- 0.47 D, 1.85 +/- 0.62 D, and 2.02 +/- 0.38 D, respectively; the mean ACD without pharmacological induction of ciliary muscle contraction, 4.40 +/- 0.44 mm, 4.35 +/- 0.50 mm, 4.25 +/- 0.53 mm, respectively; and the mean near visual acuity with best distance correction, 0.41 +/- 0.15, 0.37 +/- 0.12, and 0.39 +/- 0.11, respectively. There were no statistically significant changes in any measurement during the follow-up (P>.1). CONCLUSIONS: Refraction, ACD, and accommodative range remained stable without indication of a systemic trend toward myopia, hyperopia, PC IOL dislocation, or regression of accommodative properties. The 1CU accommodating PC IOL provided stable refraction, accommodation, and PC IOL position for up to 1 year.

Accommodation, Ocular↗

PubMed2003

Cardinal points and image-object magnification with an accommodative lens implant (1 CU).

UNLABELLED: A simple mathematical method for the determination of the cardinal points of pseudophakic eyes after implantation of an accommodative intraocular lens [posterior chamber intraocular lenses (PCIOL)] is presented. The purpose of this study was to explore the changes during pseudophakic accommodation (PAC) in (1). the positions of the cardinal points, (2). the distance of the object conjugate with the retina, and (3). the image-object magnification. These theoretical accommodation data are compared with clinical measurements. METHODS AND PATIENTS: Using biometrical measurements of the axial length, equivalent power of the cornea and the anterior chamber depth (ACD) in the non-accommodated state we used linear geometric optics for determination of the cardinal points and object distance as well as lateral magnification (the ratio of image to object size). With the measurement of ACD decrease (following pharmacological stimulation of the ciliary muscle with 2% pilocarpine eye drops) we determined the changes of the cardinal points and magnification to assess PAC amplitude from the shortening of the object distance. Calculated values of PAC amplitude were compared with the respective measured values derived from amplitude measures by accommodometer, defocusing and streak retinoscopy. We analysed the results of a prospective study on 35 eyes of 28 patients after cataract surgery (target refraction: -0.2 D) and accommodative PCIOL implantation (1 CU, Human Optics AG, Erlangen, Germany) 3 months after surgery. RESULTS: After pilocarpine eye drops, ACD (mean +/- S.D., range; median) decreased by 0.88 +/- 0.48 mm (0.51-1.91; 0.66). Distance of the in-focus object decreased from the non-accommodated state (-5.62 +/- 1.83 m, -25 to -1.1; -4.83 m) to the accommodated state (ACD decrease) (-0.81 +/- 0.21, -2.11 to -0.65; -0.79 m). For a theoretical ACD decrease of 1.0 mm (the intrinsic limitation of the PCIOL design) it was -0.59 +/- 0.28, -1.31 to -0.51; -0.63 m and resulted in an objective accommodative response of 1.49 +/- 0.16, 1.21-1.81; 1.46 D, depending on the actual geometry of the individual eye. On average, magnification as induced by PAC in contrast to that induced by adequate spectacle addition differed by only about 1%. Accommodation measured with defocusing and the accommodometer correlated significantly with the theoretical value based on IOLMaster measurement of ACD decrease (r = 0.752, p = 0.005 and r = 0.676, p = 0.02). Likewise, accommodation measured with streak retinoscopy correlated weakly with the theoretical value based on IOLMaster ACD decrease (r = 0.465, p = 0.05). CONCLUSIONS: Using geometrical optics, PAC can be derived from the biometric data of the eye and the measured ACD decrease. This approach may be an additional indicator for the accommodative response in pseudophakic patients and may allow a subdivision of the measured accommodation into true PAC and pseudoaccommodation, for example, because of increased depth of focus induced by pupillary constriction.

Accommodation, Ocular↗

PubMed2003

Computerized calculation scheme for bitoric eikonic intraocular lenses.

Despite full correction of the corneal astigmatism with toric intraocular lenses, the retinal image is distorted and the lateral image-object magnification is different in different meridians. The purpose of this study is to describe an iteration strategy for tracing an axial pencil of rays through the 'optical system eye' containing astigmatic refractive surfaces with their axes at random to calculate a thick bitoric lens implant which eliminates image distortion. The capabilities of this computing scheme are demonstrated with two clinical examples. We present a mathematically straightforward computer-based strategy for the calculation of thick bitoric eikonic lens implants. The iteration algorithm is initialized with a spherical front and a toric back surface and stepwise decreases the image distortion by adding cylinder lenses to the front lens surface corrected by the toric lens back surface. Total magnification can be modulated by varying the front-to-back surface power of the thick lens.

Algorithms↗

PubMed2003

Computerised calculation scheme for ocular magnification with the Zeiss telecentric fundus camera.

Littmann (1982) described a method to determine the magnification of the eye in order to relate the size of a retinal feature to its measured image size on a telecentric fundus camera film. This required information only about ametropia and corneal curvature. Several other methods have been reported since then which consider other biometric data to enhance the accuracy of this classical method. The purpose of this study is to describe a numerical calculation scheme to determine the magnification q of the eye in two cardinal meridians using paraxial raytracing. Our calculation scheme is based on ametropia, keratometry, as well as biometric data such as axial length, anterior chamber depth and thickness of the crystalline lens. It is described step-by-step in order (1) to determine the refractive powers of both surfaces of the crystalline lens, which are not directly measurable in vivo, (2) to derive the retinal image conjugate to a circular object using paraxial raytracing, (3) to fit an ellipse to the retinal image, (4) to determine the secondary principal points (Gaussian length) separately for both cardinal meridians and (5) to calculate the ocular magnification q. The power of the crystalline lens is estimated to compensate for the spherocylindrical refraction at the spectacle plane and the corneal refraction with an astigmatic component thus creating a sharp image focused at the retinal plane. The capabilities of this computing scheme are demonstrated with five clinical examples and are related to the respective values of the classical Littmann formula as well as to enhanced methods described by Bennett (1988), Bennett et al. (1994) and Garway-Heath et al. (1998).

Anterior Chamber↗

PubMed2003

[Assessment of the optical image quality of the eye using raytracing technique of corneal topography data].

BACKGROUND: Optical aberrations in the optical system may downgrade image quality and cannot be fully compensated by spherocylindrical glasses. The subjectively evaluated visual acuity may be significantly reduced. The purpose of this study was to calculate the image forming properties of the eye using a spotlight source or alternatively extended objects. METHODS: A convex and first derivative continuous (C1) surface from the rough height data of the anterior corneal surface (TMS-1, Tomey, Erlangen) or the anterior and posterior corneal surface (Orbscan, Orbtec, USA) was calculated by means of an interpolating subdivision scheme (modified Butterfly algorithm). The characteristics of the residual refractive surfaces were used according to Navarro's eye model. The focal distance was calculated from the exact raytracing calculation (Snellius' law) of the point-spread function by minimising the variance of the point-spread function. The diffraction property of the aperture stop was implemented with a transmission characteristic according to a radially symmetrical Bessel function within the entrance pupil. The algorithm was realised with a C code on the LINUX platform and applied to a normal eye (example 1, TMS-1), an eye with severe keratoconus (example 2, TMS-1) and an eye with corneal scars (example 3, Orbscan). RESULTS: The focal distance in example 1 (22.5 mm, 22.6 mm, and 22.8 mm) increased with the pupil diameter (2 mm, 3 mm, and 5 mm). The variance of the approximately radially symmetrical point-spread function in the focal plane attained a minimum value with a pupil size of 3 mm (0.164, 0.104, and 0.230). In example 2, the focal distance changed inconclusively (21.1 mm, 21.0 mm, and 21.3 mm) with the pupil size (2 mm, 3 mm, and 5 mm). The variance of the markedly asymmetrical point-spread function in the focal plane was systematically higher compared to the values of example 1 and reached a minimum value with a pupil size of 3 mm (0.255, 0.224, and 0.371). The imaging of the sinus-modulated pattern is anisotropic due to the asymmetry of the point-spread function. In example 3, the focal distance (22.3 mm, 22.3 mm, and 22.5 mm) did not change systematically with the pupil size (2 mm, 3 mm, and 5 mm). The variance of the nearly radially symmetrical point-spread function changed only marginally between pupil sizes of 2 mm and 3 mm (0.231, 0.239, and 0.338). CONCLUSIONS: Raytracing of corneal topography height data based on refined eye models with the option of auto-focussing has the potential to trace the optical resolution of the eye for arbitrary objects. Further studies on contrast sensitivity and the conversion of the real image to a perceived image by the retina and brain are required for complete modeling of subjective visual acuity.

Adult↗

PubMed2003

[Cataract and keratoplasty--simultaneous or sequential surgery?].

BACKGROUND AND PURPOSE: Since the introduction of the triple procedure (simultaneous penetrating keratoplasty [PK], extracapsular cataract extraction [CE] and implantation of a posterior chamber intraocular lens [PCIOL]) in the mid-seventies, there is an ongoing discussion among corneal surgeons concerning the best approach for combined corneal disease and cataract. METHODS: Besides the classical triple procedure (1), two alternative microsurgical approaches are feasible: (2) CE + PCIOL prior to PK and (3) CE + PCIOL after PK. For the refractive results after TRIPLE some intraoperative details are crucial: Trephination of recipient and donor from the epithelial side without major oversize (Guided Trephine System or Nonmechanical Excimer Laser Trephination) should preserve the preoperative corneal curvature. Graft and the PCIOL placed in the bag after continuous curvilinear capsulorhexis should be centered along the optical axis. If possible, performing the capsulorhexis under controlled intraocular pressure conditions prior to trephination may help to minimise the risk of capsular ruptures. RESULTS: The major advantage of the TRIPLE is the faster visual rehabilitation and less efforts for the mostly elderly patients. However, two intraocular interventions with approach (2) and (3) bear an increased risk of infection and suprachoroidal haemorrhage. Approach (2) requires a cornea that is still transparent enough to perform cataract surgery, and the risk of intraocular pressure rise after PK seems to be increased. Approach (3) has the potential of a simultaneous reduction of astigmatism during CE (appropriate location of the incision, simultaneous refractive keratotomies or implantation of a toric PCIOL). Disadvantages may include the loss of graft endothelial cells and the theoretically increased risk of immunological allograft reactions. After TRIPLE, major deviations from target refraction have been reported. However, individual multiple regression analysis may help to minimise this problem with appropriate methods of trephination. Since suture removal after PK may result in major individual changes of the corneal curvature, IOL power calculation for approach (3) requires all sutures to be removed at the time of CE. However, even after complete suture removal the abnormal proportions between anterior and posterior curvatures and/or the irregular topographies after PK may be responsible for marked IOL power miscalculations in the individual case. CONCLUSIONS: The postulated better refractive outcome and better uncorrected visual acuity after the sequential approach is opposed by a markedly delayed visual rehabilitation. For this reason, we consider the TRIPLE procedure including CE via open sky in general anesthesia as the method of choice for combined lens and corneal opacities. Because of the often rapidly progressive nuclear cataracts after PK, we recommend the simultaneous approach in elderly patients with Fuchs' dystrophy even with incipient lens opacities.

Aged↗

PubMed2003

[Impact of intracameral pressure on donor cut angles in nonmechanical Er:YAG laser trephination for penetrating keratoplasty].

BACKGROUND AND PURPOSE: Congruent cut surfaces are a predisposition for good apposition of donor and recipient during penetrating keratoplasty (PK). The purpose of this study was to assess the impact of the intracameral pressure during nonmechanical donor trephination from the epithelial side on the cut angles for experimental human PK. METHODS: With a Q-switched 2.94 micro m Er : YAG laser a 6 mm sized corneal donor trephination was performed subtotally in 30 human corneas using an artificial anterior chamber device allowing different intracameral pressures (10, 20, and 40 mm Hg). The cut angles were measured immediately after the trephination by ultrasound biomicroscopy (UBM) at four quadrants: between trephination cut and corneal epithelium (angle 1 = A1-UBM) and between trephination cut and horizontal plane (angle 2 = A2-UBM). The positions of the measures were marked, the corneas were fixed in a buffered 10 % paraformaldehyde solution, and the same positions were analyzed by histology. The histological cuts were digitized, the images printed, and the cut angles measured in paper (A1-histology). RESULTS: Mean angles were 111.6 degrees /113.5 degrees /126.6 degrees (A1-UBM), 88.4 degrees /93.5 degrees /101.8 degrees (A2-UBM) and 120.4 degrees /125.1 degrees /119.3 degrees (A1-histology) with 10/20/40 mm Hg, respectively. The A2-UBM showed a significant increase of divergence with increasing intracameral pressure (p < 0.03). For A1-UBM cut angles with 10 and 20 mm Hg were significantly smaller compared to those with 40 mm Hg (p < 0.002), but there was no difference of divergence between 10 and 20 mm Hg. The A1-histology cut angle showed no correlation with intracameral pressure (p > 0.09). CONCLUSIONS: Increasing intracameral pressure using an artificial anterior chamber during donor trephination from the epithelial side for nonmechanical PK using Er : YAG laser results in increasing divergence of cut angles. This may disturb the congruence of the cut angles in donor-recipient apposition. To achieve standardised cut angles for a good donor recipient apposition, similar normotonic intracameral pressures for donor and recipient trephination should be attempted. The UBM has the potential to analyse the cut angle immediately after subtotal trephination preserving the attempted intracameral pressure in the artificial anterior chamber. Histological analysis of the cut angles seems to lack methodological validity.

Anterior Chamber↗

PubMed2003

[In-vivo measurement of autofluorescence in the parapapillary atrophic zone of optic discs with and without glaucomatous atrophy].

BACKGROUND: To assess the level of autofluorescence (lipofuscin) of atrophic parapapillary zones in different stages of glaucomatous optic disc atrophy. METHODS: Controlled cross-sectional prospective analysis of 79 consecutive eyes (15 normals as controls, 26 with ocular hypertension, 38 with primary open angle glaucoma). Eyes with retinal diseases or retinal pigment epithelial pathologies were excluded. The confocal scanning laser ophthalmoscope (HRA, Heidelberg Retina Angiograph) was used after lipofuscin excitation with argon blue laser (488 nm) to detect parapapillary autofluorescence in a spectrum above 500 nm. Size, extension of the parapapillary autofluorescent area and its mean distance to the optic nerve head were measured using the HRA standard software. Additional optic nerve head photographs taken with the 15 degrees Zeiss telecentric fundus camera (30 degrees camera with 2 x magnifier) were examined by two experienced ophthalmologists to determine the stage of glaucomatous optic disc atrophy (stages 0 to 4). RESULTS: Very small autofluorescent areas were found in vital discs (optic nerve glaucoma stage 0) in the parapapillary atrophic area (0.08 +/- 0.12 mm (2)) in contrast to glaucomatous discs in stage 1 (0.24 +/- 0.26 mm (2)) and stages 2, 3 and 4 (0.59 +/- 1.29 mm (2), logistic regression analysis r = 0.71; P = 0.029). The circular extension of the autofluorescent area correlated borderlined with the stage of the glaucomatous disc atrophy (higher glaucoma stages: r = 0.82; P = 0.09). The autofluorescent area was larger in OHT than in controls (0.11 mm (2) vs. 0.04 mm (2), P < 0.03). The circular extension of the autofluorescent area was longer in OHT than in controls (0.5 mm vs. 1.15 mm, P < 0.04). CONCLUSIONS: As a sign of pronounced lipofuscin accumulation in the parapapillary atrophic zone higher degrees of fundus autofluorescence can be detected in OHT and manifest primary open angle glaucoma in contrast to normals. The lipofuscin accumulation is correlated with the stage of progression of glaucoma and the stage of optic disc atrophy. The detection of active parapapillary autofluorescent areas especially in OHT may offer the ophthalmologist an important tool for early diagnosis.

Adult↗

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

[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↗