Biomedical subjects

Nhung X Nguyen

Publications and source records attributed to Nhung X Nguyen.

At least 19 recordsLinked to original sources

PubMed2006

Long-term refractive and visual outcome after penetrating keratoplasty only versus the triple procedure in Fuchs' dystrophy.

BACKGROUND: Long-term refractive and visual outcome after penetrating keratoplasty (PK) only and the triple procedure in eyes with Fuchs' endothelial dystrophy were assessed and compared. DESIGN: Retrospective, non-randomized, cross-sectional, clinical, single-centre study. METHODS: Ninety-two eyes of 87 patients were divided into two groups. Group 1 consisted of 28 eyes (mean age 62+/-13 years) that had undergone PK only and group 2 consisted of 64 eyes (mean age 69+/-10 years) that had undergone the triple procedure. Inclusion criteria were: (1) Fuchs' dystrophy, (2) central nonmechanical trephination, (3) double-running suturing technique and (4) availability of 'two-sutures-out' findings. In all eyes, a central trephination was performed (donor trephination from the epithelial side) using the 193-nm excimer laser along metal masks with eight 'orientation teeth/notches'. A double-running 10-0 nylon suture was applied in all eyes. Subjective refractometry (trial glasses), standard keratometry (Zeiss) and corneal topography analysis (TMS-1, Tomey) were performed in all eyes with 'two-sutures-in', 'one-suture-out', and 'two-sutures-out'. Main outcome measures included refractive cylinder, keratometric and topographic net astigmatism, keratometric and topographic central power, best-corrected visual acuity (BCVA), spherical equivalent (SE) of manifest refraction, surface regularity index (SRI), surface asymmetry index (SAI), and regularity of keratometry mires. RESULTS: The results were compared between the two groups (i.e. group 1 vs group 2) at various stages (i.e. 'two-sutures-in', 'one-suture-out', 'two-sutures-out'). Refractive cylinder in dioptres [D] was 2.5/2.0/2.5 vs 2.0/1.5/3.0, keratometric astigmatism [D] was 3.5/2.6/3.0 vs 3.5/3.1/3.5 and topographic astigmatism [D] was 3.9/4.1/4.9 vs 4.2/5.0/5.1. Keratometric central power [D] was 41.7/42.4/43.8 vs 41.5/41.9/43.3 and topographic central power [D] was 42.3/43.6/43.7 vs 42.6/41.8/44.3. BCVA was 0.5/0.6/0.6 vs 0.5/0.5/0.5. SE [D] was 0.0 /0.0/-0.5 vs -0.5/-0.5/-1.1. SRI was 1.5/1.1/1.0 vs 1.4/1.4/1.2 and SAI was 1.0/0.8/1.0 vs 1.3/1.2/1.0. The proportion of 'regular' and 'mildly irregular' keratometry mires was 44% / 69% / 68% vs 29% / 46% / 66%. The differences between the two groups did not reach statistical significance at any of the stages. CONCLUSIONS: Refractive and visual outcome after the triple procedure did not differ significantly from that after PK only. Therefore, we recommend the triple procedure in elderly patients with Fuchs' dystrophy and cataract to avoid delayed visual rehabilitation and a second surgical procedure.

Adult↗

PubMed2006

Surgery-related factors influencing corneal neovascularization after low-risk keratoplasty.

PURPOSE: To identify the speed of corneal neovascularization (CNV) after penetrating keratoplasty (PK) and to evaluate the influence of surgery-related factors on postkeratoplasty CNV in keratoconus patients. DESIGN: Prospective, longitudinal, observational, case series study. METHODS: All consecutive primary PKs performed for keratoconus by four experienced surgeons between January 1, 2000 and December 31, 2002 at our department were included (n=66 patients). Standardized corneal photographs taken preoperatively and at 6 weeks, 3, 6, 12, 18, and 24 months postoperatively were evaluated. Limbus suture distance (LSD), limbus graft distance (LGD), inner suture angle (ISA), and maximal extension of CNVs in digitized pictures with 100-fold magnification were measured at each of the 16 suture turning points at every timepoint. RESULTS: Forty-four (67%) out of 66 corneal grafts developed some degree of CNV after PK, most commonly from around the 12 o'clock position. The mean speed of CNV growth was 114 microm/month with the fastest growth occurring during the first six weeks after PK. There was an inverse correlation between CNV and LSD, LGD, and ISA (all P<.001). Ninety percent of all CNVs developed with LSD<406 microm and with LGD<1000 microm. Superior limbal localization between 11 and 1 o'clock is an independent risk factor for postoperative neovascularization, too (P<.001). CONCLUSIONS: Small LSD, small LGD, and narrow stitching with small ISA were identified as potentially modifiable surgical risk factors for CNV after PK. The speed of CNV outgrowth was most pronounced in the first weeks after PK making early postoperative controls for CNV growth and initiation of antiangiogenic treatment important.

Adolescent↗

PubMed2004

Accommodation after Nd: YAG capsulotomy in patients with accommodative posterior chamber lens 1CU.

PURPOSE: After initial encouraging results with the accommodative 1CU posterior chamber lens (PCIOL), we investigated the rate, the postoperative time point of posterior capsular opacification (PCO) necessitating YAG capsulotomy and the accommodative range after Nd: YAG capsulotomy in patients with 1CU-PCIOL. PATIENTS AND METHODS: This prospective clinical study included 65 patients who underwent phacoemulsification and implantation of the accommodative 1CU-PCIOL with postoperative follow-up from 3 to 24 months. Postoperative examination was performed 3, 6 and 12 months after surgery, then before and 6 weeks after Nd: YAG capsulotomy. Measurements included: the best corrected distance visual acuity, distance refraction, near visual acuity (Birkhauser charts in 35 cm) obtained with best distance correction, accommodative range measured by subjective near point with an accodommometer and defocusing with a visual acuity fall to 0.4. RESULTS: Both best corrected distance visual acuity (1.1+/-0.1) and near visual acuity with best distance correction (0.4+/-0.1) remained stable over the follow-up period until 12 months postoperatively. The accommodative range determined by near point was stable (mean 2.0+/-0.5 D). Also, the defocusing range remained stable over 12 months (1.8+/-0.4 D). A clinically relevant posterior capsule opacification with a significant decrease of visual acuity (0.4+/-0.2) and a need for Nd: YAG capsulotomy was diagnosed in 12 patients between 15 and 22 (mean 20+/-4, median 20) months postoperatively. All capsulotomies were performed without complication. Six weeks after capsulotomy, best corrected distance visual acuity was improved (1.1+/-0.1), near visual acuity with best distance correction was 0.4+/-0.1 and the accommodative range determined by near point was 1.95+/-0.6 D and by defocusing was 1.88+/-0.47 D. Six weeks after capsulotomy, measurements of the accommodative range did not show any statistical difference to the 12-month results before the occurrence of PCO (P>0.5). CONCLUSIONS: A clinically relevant PCO with a significant decrease of visual acuity necessitating Nd: YAG capsulotomy occurred mainly after 15 postoperative months in patients with 1CU. Our results indicate that Nd: YAG capsulotomy may not affect the accommodation ability of the 1CU. Nevertheless, long-term studies are needed to further analyze the accommodative properties.

Accommodation, Ocular↗

PubMed2004

Comparison of 6-month results of implantation of the 1CU accommodative intraocular lens with conventional intraocular lenses.

OBJECTIVE: To evaluate the clinical results of implantation of the new 1CU accommodative intraocular lens (IOL) in cataract patients and to compare results with those of conventional IOLs. DESIGN: Nonrandomized comparative trial. PARTICIPANTS: Twenty eyes of 20 patients (mean age = 65.8+/-13.3 years) in the 1CU group and 20 eyes of 20 patients (mean age = 67.4+/-11.6 years) in the control group. METHODS: All patients underwent phacoemulsification and IOL implantation. The 1CU accommodative lens was used in 20 eyes, and conventional IOLs (polymethyl methacrylate, hydrophilic or hydrophobic acrylate) were used in the control group. Patients were observed prospectively, and 6-month data were analyzed. MAIN OUTCOME MEASURES: Accommodative ranges determined by 3 different methods (near point, defocusing, and retinoscopy). Secondary outcome measures were (1) increase of anterior chamber depth after topical application of 1% cyclopentolate eyedrops and (2) distance-corrected near visual acuity with Birkhäuser reading charts at 35 cm. RESULTS: We observed a higher accommodative range with all 3 methods (mean = 1.83+/-0.49 vs. 1.16+/-0.27 diopters [D] [near point], 1.85+/-0.43 vs. 0.64+/-0.21 D [defocusing], and 0.98+/-0.55 vs. 0.17+/-0.22 D [retinoscopy]), a larger increase of anterior chamber depth after cyclopentolate eyedrops (mean = 0.42+/-0.18 vs. 0.11+/-0.06 mm), and better distance-corrected near visual acuity (median = 0.4 vs. 0.2) in the 1CU group relative to the control group. All differences between the 2 groups were statistically highly significant (P<0.001). CONCLUSIONS: In the present study, the 1CU accommodative IOL showed increased accommodative range and better near visual acuity than a control group with conventional IOLs. Further research is necessary to confirm these results in masked, randomized, prospective studies and to confirm further the accommodative power of this group of new IOLs.

Accommodation, Ocular↗

PubMed2004

Frequency-doubling perimetry in patients following penetrating keratoplasty.

PURPOSE: Perimetry using a frequency-doubling technique (FDT perimetry) is becoming established as a new diagnostic tool to detect early visual field losses. The aim of this study was to evaluate the diagnostic usefulness of an FDT perimetry protocol (C-20-5) in patients after penetrating keratoplasty (PK) and to assess whether this method is influenced by postoperative corneal topographic changes. METHODS: Thirty-six patients (age 40 +/- 13, median 41 years) following PK and 68 age-matched controls were included in this study. The postoperative interval was 21 +/- 19, median 14 months. Patients with preexisting glaucoma or any postoperative intraocular pressure elevation were excluded. The indications for PK were keratoconus in 82%, Fuchs dystrophy in 15%, and secondary bullous keratopathy in 3%. In 19 patients keratoplasty was performed in 1 eye. FDT perimetry was evaluated in both eyes to judge intraindividual variability. FDT perimetry was done using the screening strategy, which begins testing at the normal 5% probability level. If a stimulus is not detected, further targets are presented. FDT viewfinder and statistics software were used for case-wise recalculation of all missed localized probability levels. RESULTS: Neither mean overall FDT score (0.8 +/- 1.9, median 0.0 versus 0.9 +/-1.0, median 0.0) nor total test time (44 +/- 4.7, median 44 versus 44 +/- 4.2, median 42 seconds) showed significant differences between patients after PK and controls (P = 0.5). There was also no significant difference of mean FDT score between eyes after keratoplasty (0.8 +/- 1.9, median 0.00) and nonoperated contralateral eyes (0.9 +/- 2.0, median 0.00, P = 0.8) in the same patient. No significant correlation between FDT score and visual acuity as well as corneal keratometric astigmatism could be found in patients after PK and in normals (r < 0.2, P = 0.3). In patients after PK, FDT score and examination time were statistically independent of keratometric astigmatism (P = 0.7), topographic astigmatism (P = 0.4), spherical equivalent (P = 0.5), central corneal thickness (P = 0.7), and interval of postoperative follow-up (P = 0.6). CONCLUSIONS: Perimetry using the FDT protocol (C-20-5) seems to be feasible in patients after PK and does not depend on postoperative topographic changes of the cornea. This method allows valid information on visual field abnormality in patients after PK The results indicate that this method may be helpful as a supplement to detect early glaucomatous damage in patients after PK.

Adult↗

PubMed2003

Predictive donor factors for chronic endothelial cell loss after nonmechanical penetrating keratoplasty in a regression model.

PURPOSE: To assess the diagnosis-based impact of donor parameters and trephination diameter as predictive factors on corneal endothelial cell density with an exponential regression model after nonmechanical penetrating keratoplasty (PK). METHODS: Six hundred thirty-one eyes [291 keratoconus (group I, trephination diameter 8.0 mm); 202 Fuchs' dystrophies (group II, trephination diameter 7.5 mm)-84 PK only (IIa) and 118 triple procedures (IIb); and 138 pseudophakic bullous keratopathies (group III, trephination diameter 6.5-8.0 mm)] were included in this retrospective study. The time course of the endothelial cell density (specular microscope EM 1100, Tomey, Erlangen) after PK was assessed. Endothelial cell density was analyzed in a longitudinal manner considering at least three valid postoperative cell counts (follow-up 29+/-17 months) with an exponential regression model (minimizing the residuum between observed and predicted endothelial cell count). The following potentially predictive parameters were assessed: donor age (DA), post-mortem time (PM), storage time (ST) and trephination diameter (group III). RESULTS: In the exponential regression model endothelial cell count decreased in I/II/III by 3.1+/-24.2% / 12.6+/-20.2% (IIa: 8.9+/-17.3%, IIb: 14.8+/-22.0%) / 18.7+/-27.3% annually. PM ( P=0.16 / P=0.10 / P=0.25) and DA ( P=0.20, / P=0.12 / P=0.16) did not correlate with the cell loss, but ST ( P=0.04 / P=0.04 / P=0.02) showed a mild correlation, especially in short-term-stored corneas. In group III the trephination diameter ( P=0.01) correlated inversely with the cell loss. Between short-term-preserved and organ-cultured donor corneas there was no statistically significant difference in the cell loss in any group. CONCLUSIONS: The post-mortem time and the donor age is not associated with a chronic endothelial cell loss after keratoplasty, whereas a long storage time may exaggerate the endothelial cell loss. Between short-term-preserved and organ-cultured donor corneas there was no difference in the time gradient. In bullous keratopathy patients a larger trephination size reduces the chronic endothelial cell loss.

Adolescent↗

PubMed2003

Theoretical and measured pseudophakic accommodation after implantation of a new accommodative posterior chamber intraocular lens.

OBJECTIVE: To analyze different techniques of measuring accommodation after implantation of a new accommodative posterior chamber intraocular lens (PCIOL). METHODS: In this comparative, nonrandomized interventional study, we analyzed 15 eyes of 15 patients (aged 44-84 years) at 6 months after cataract surgery and PCIOL implantation (Akkommodative 1CU; HumanOptics AG, Erlangen, Germany) and compared these results with those of an age-matched control group (n = 15). We used the following methods to measure accommodation: dynamic measurement with objective (videorefractometry [PowerRefractor; PlusOptix, Erlangen] and streak retinoscopy) and subjective (subjective near point [push-up test and accommodometer] and defocusing) techniques, as well as static measurement of the change in anterior chamber depth (ACD) using the IOLMaster (Zeiss, Jena, Germany) after pharmacological stimulation using 2% pilocarpine eye drops. MAIN OUTCOME MEASURES: Theoretical accommodation calculated from the forward shift of the lens optics (decrease of ACD) using paraxial geometrical optics and measured accommodation amplitude. RESULTS: Accommodation amplitude (mean +/- SD; range; median) results after 6 months in the study and control groups were as follows: 1.00 +/- 0.44; 0.75-2.13; 1 diopter (D); and 0.35 +/- 0.26; 0.10-0.65; 0.25 D, respectively, using the PowerRefractor; 0.99 +/- 0.48; 0.13-2.00; 0.88 D; and 0.24 +/- 0.21; -0.13-0.75; 0.25 D, respectively, using retinoscopy; 1.6 +/- 0.55; 0.50-2.56; 1.7 D; and 0.42 +/- 0.25; 0.00-0.75; 0.50 D, respectively, using subjective near point; and 1.46 +/- 0.53; 1.00-2.50; 1.75 D; and 0.55 +/- 0.33; 0.25-0.87; 0.50 D, respectively, using defocusing. Anterior chamber depth decreased in the study and control groups as follows: 0.78 +/- 0.12; 0.49-1.91; 0.65 mm; and 0.16 +/- 0.09; 0.00-0.34; 0.18 mm, respectively, after applying 2% pilocarpine eyedrops, indicating an accommodation of 1.16 +/- 0.22; 0.72-1.88; 1.05 D vs 0.22 +/- 0.13; 0.00-0.47; 0.23 D (P =.001). CONCLUSIONS: Accommodation after implantation of a presumably accommodative PCIOL can be measured with clinical methods or derived from the biometric data of the eye and the measured ACD decrease using geometrical optics. For clinical purposes, pseudophakic accommodation should be assessed with a variety of different techniques, including subjective and objective measurements. The theoretical approach using geometrical optics may be an additional indicator for the accommodative response in patients with pseudophakic eyes and may allow a subdivision of the measured accommodation into true pseudophakic accommodation and pseudoaccommodation.

Accommodation, Ocular↗

PubMed2003

Combined use of frequency doubling perimetry and polarimetric measurements of retinal nerve fiber layer in glaucoma detection.

PURPOSE: The aim of this study was to evaluate the diagnostic usefulness of the combined use of frequency-doubling technology (FDT) perimetry and polarimetry of the retinal nerve fiber layer. DESIGN: Cross-sectional study. METHODS: Seventy ocular hypertensive patients (normal optic disk and standard perimetry, elevated intraocular pressure [>21 mm Hg]), 59 patients with "preperimetric" open-angle glaucoma (glaucomatous optic disk atrophy, elevated intraocular pressure [>21 mm Hg], no visual field defect in standard perimetry), 105 patients with "perimetric" open-angle glaucoma (glaucomatous optic disk atrophy and clearly marked visual field defect), and 73 control subjects had FDT screening (protocol: C-20-5) and polarimetric measurements (GDx). Criteria for exclusion: optic disks larger than 4 mm(2), media opacities, patients younger than 33 years or older than 66 years. None of the subjects had earlier FDT perimetry. One eye of each patient and control subject entered the statistical evaluation. Database and statistical software were used for case-wise recalculation of all missed localized probability levels to create a FDT screening score. RESULTS: At a predefined specificity of 94.5% in control eyes, discrimination between "perimetric" glaucoma and normal subjects is superior using the FDT perimetry (sensitivity = 84.8%) in comparison to polarimetry (sensitivity = 63.8%), whereas sensitivity is similar with both methods in "preperimetric" patients (GDx, FDT: 25.4%). In several cases, patients classified as glaucomatous by the GDx are not the same patients as identified by the FDT perimetry. Therefore, a two-dimensional discrimination analysis can increase correct positive classification. Using a linear combination of the present FDT screening score and polarimetry ("the number"), 92.4% of "perimetric" glaucoma eyes and 44.1% of "preperimetric" glaucoma eyes have been classified as glaucomatous. CONCLUSION: Joint usage of polarimetry and FDT perimetry indicate that a combination of different techniques which can uncover different glaucoma properties, might be helpful in early glaucoma detection.

Cross-Sectional Studies↗

PubMed2003

Measurement of accommodation after implantation of an accommodating posterior chamber intraocular lens.

PURPOSE: To analyze techniques of measuring accommodation after implantation of an accommodating posterior chamber intraocular lens (PC IOL). SETTING: Department of Ophthalmology and University Eye Hospital, University Erlangen-Nürnberg, Erlangen, Germany. METHODS: This prospective study analyzed 23 eyes of 23 patients (aged 41 to 87 years) after cataract surgery and PC IOL implantation (1 CU, HumanOptics) 4 weeks and 3 and 6 months after surgery. The results were compared to those in an age-matched control group (n = 20) 6 months after surgery. The following methods were used to measure accommodation: dynamic with objective techniques (PlusOptix PowerRefractor videorefractometry, streak retinoscopy) and subjective techniques (subjective near point [push-up test, accommodometer], defocusing); static with pharmacologic stimulation after pilocarpine 2% eyedrops directly (conventional refractometry); indirectly (change in the anterior chamber depth [ACD] with Zeiss IOLMaster). RESULTS: Results at 6 months, given as mean +/- SD (range), in the study and control groups, respectively, were as follows: near visual acuity (Birkhäuser reading charts at 35 cm) with distance correction, 0.32 +/- 0.11 (0.20 to 0.60) and 0.14 +/- 0.10 (0.05 to 0.30); accommodation amplitude (diopters) by PowerRefractor, 1.00 +/- 0.44 (0.75 to 2.13) and 0.35 +/- 0.26 (0.10 to 0.65), by retinoscopy, 0.99 +/- 0.48 (0.13 to 2.00) and 0.24 +/- 0.21 (-0.13 to +0.75), by subjective near point, 1.60 +/- 0.55 (0.50 to 2.56) and 0.42 +/- 0.25 (0.00 to 0.75), and by defocusing, 1.46 +/- 0.53 (1.00 to -2.50) and 0.55 +/- 0.33 (0.25 to 0.87). The mean ACD decrease (mm) was 0.78 +/- 0.12 (0.49 to 1.91) and 0.16 +/- 0.09 (0.00 to 0.34) after pilocarpine 2% eyedrops, indicating a mean accommodation of 1.40 D and 0.29 D, respectively, based on Gullstrand's model eye (P =.001). The lowest fluctuation between follow-ups was with the subjective near point and the defocusing techniques followed by ACD decrease with the IOLMaster. CONCLUSIONS: Accommodation after implantation of an accommodating PC IOL should be assessed with several techniques, including subjective and objective, to differentiate true pseudophakic accommodation from pseudoaccommodation. Researchers should be aware of the different variability and consistency of measurements with each technique over time.

Accommodation, Ocular↗

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

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

New glaucoma classification method based on standard Heidelberg Retina Tomograph parameters by bagging classification trees.

PURPOSE: In this article we propose and evaluate nonparametric tree classifiers that can handle non-normal data and a large number of possible predictors using the full set of standard Heidelberg Retina Tomograph measurements for classifying glaucoma. METHODS: The classifiers were trained and tested using standard Heidelberg Retina Tomograph parameters from examinations of 98 subjects with glaucoma and 98 normal subjects of the Erlangen Glaucoma Registry. All patients and control subjects were evaluated by 15 degrees -optic disc stereographs, Heidelberg Retina Tomograph measurements, standard computerized white-in-white perimetry, and 24-hour-intraocular pressure profiles. The subjects were matched by age and sex. Standard classification trees as well as bagged classification trees were used. The classification outcome of the trees was compared with the classification by two published linear discriminant functions based on Heidelberg Retina Tomograph variables with respect to their cross-validated misclassification error. RESULTS: The bagged classification tree had the lowest misclassification error estimate of 14.8% with a sensitivity of 81.6% at a specificity of 88.8%. The cross-validated error rates of the two linear discriminant function procedures were 20.4% (sensitivity 82.6%, specificity 76.7%) and 20.6% (sensitivity 81.4%, specificity 77.3%) for our set of observations. Bagged classification trees were able to reduce the misclassification error of glaucoma classification. CONCLUSIONS: Bagged classification trees promise to be a new and efficient approach for glaucoma classification using morphometric 2- and 3-dimensional data derived from the Heidelberg Retina Tomograph, taking into account all given variables.

Case-Control Studies↗

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

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

Corneal neovascularization after nonmechanical versus mechanical corneal trephination for non-high-risk keratoplasty.

PURPOSE: To analyze the influence of mechanical versus nonmechanical trephination of donor and host corneas on superficial, peripheral corneal neovascularization occurring after non-high-risk keratoplasty. METHODS: Patients of the prospective Erlangen non-high-risk keratoplasty study with standardized corneal photographs taken preoperatively and 1 year later were analyzed (n = 184). Slides of these photographs were projected (magnification x100) and corneal vessels graded in a standardized semiquantitative fashion into five categories with regard to limbus, sutures, and host-graft junction in each of 12 corneal sectors. Degree (total increase of grades in the 12 sectors) and maximal extent of corneal neovascularization (maximal centripetal extension of blood vessels) were analyzed. In 32 patients mechanical (17%) and in 152 nonmechanical trephination of host and donor tissue was performed (193-nm excimer laser, 83%). Statistical analysis was done using Fisher's exact and Mann-Whitney test. RESULTS: Corneal neovascularization within the first postoperative year was lower in the nonmechanical [73 of 152 (48%)] compared with mechanical trephination group [24 of 32 (75%); p< 0.01; Mann-Whitney test]. Maximal extent of neovascularization (i.e., vessels reaching the interface or growing beyond) was not yet significantly different between nonmechanical (8%) and mechanical (17%) trephination (p = 0.074). CONCLUSIONS: Nonmechanical trephination using the 193-nm excimer laser in non-high-risk keratoplasties might reduce corneal neovascularization occurring within the first postoperative year. This indicates that in the non-high-risk setting, development of postoperative corneal neovascularization may be affected by the trephination technique and subsequent wound-healing response.

Aged↗