Rupert Menapace

Partial coherence interferometry: a novel approach to biometry in cataract surgery

PURPOSE To compare biometry performed by an enhanced version of dual beam partial coherence interferometry and applanation ultrasound in a prospective study of 85 cataract eyes to improve refractive outcome of cataract surgery due to a more accurate calculation of intraocular lens power. METHODS The SRK II formula using ultrasound biometry data was employed. Three months after surgery, partial coherence interferometry biometry was repeated and refractive outcome was determined. Preoperative partial coherence interferometry biometry data were used to determine the refractive power of the intraocular lenses retrospectively and to calculate the possible refractive outcome. RESULTS Precision of partial coherence interferometry biometry was more than 10 times better than that of ultrasound. Therefore, the possible mean absolute error for postoperative refraction achieved with partial coherence interferometry biometry was 0.49 diopters (compared with 0.67 diopters with ultrasound biometry), resulting in an improvement of 27%. Axial eye length measured with the two techniques differed by a mean of 460 microm. The difference in lens thickness measured with partial coherence interferometry and ultrasound significantly correlated with cataract grade. A mean shortening of 120 microm of axial eye length following cataract surgery was also detected by partial coherence interferometry. CONCLUSIONS The enhanced version of partial coherence interferometry offers biometry with unprecedented precision (<10 microm) and resolution (approximately 12 microm), therefore improving the refractive outcome in cataract surgery. This noninvasive technique provides a high degree of comfort for the patient, with no need for local anesthesia or pupil dilation and minimized risk of corneal infection.

The capsular tension ring: designs, applications, and techniques

&NA; Originally, the open poly(methyl methacrylate) (PMMA) capsular tension ring (CTR) was designed to compensate for zonular defects or to stretch the posterior capsule in highly myopic eyes not receiving an intraocular lens (IOL). We address the variety of subsequent designs, applications, and techniques that have evolved. With pre‐existing or intraoperative zonular defects, a standard CTR may be inserted before or at any time during cataract removal to maintain or re‐establish an extended capsular diaphragm. For profound zonular dialysis or weakness, a CTR was designed for scleral fixation. Capsular tension rings with integrated tinted sector shields have been developed to compensate for sector iris colobomas or aniridia. The CTR has also been used as a measuring gauge for in vivo quantification of capsule dimensions and postoperative capsular shrinkage. The CTR has improved control during primary posterior capsulorhexis and prevented oval distortion along the lens axis postoperatively. During combined cataract and vitreous surgery, a CTR prevents capsule damage and provides undisturbed peripheral visualization before IOL implantation. Capsular tension rings may also influence capsule opacification formation. A special band‐shaped CTR with sharp edges was developed to inhibit lens epithelial cell migration and avoid capsulorhexis–optic contact.

Comparison of 4 methods for quantifying posterior capsule opacification.

Purpose: To compare the results of posterior capsule opacification (PCO) quantification and the repeatability of a fully automated analysis system (Automated Quantification of After‐Cataract [AQUA]) with that of 2 other quantification methods and subjective grading of PCO. A test set of digital retroillumination images of 100 eyes with PCO of varying degrees was used. Setting: Department of Ophthalmology, University of Vienna, Vienna, Austria. Methods: One hundred digital retroillumination images of eyes (100 patients) with PCO were selected to attain an even distribution from mild to severe cases. The images were evaluated by 4 methods: subjective grading by 4 experienced and 4 inexperienced examiners, the subjective Evaluation of Posterior Capsular Opacification (EPCO) system, posterior capsule opacification (POCO) software, and the AQUA system. Ten images were presented twice to assess the reproducibility of the analysis systems. Results: Subjective grading correlated best with the subjective EPCO system and the objective AQUA system (r = 0.94 and r = 0.93, respectively). The POCO system showed very early saturation and therefore a much weaker correlation (r = 0.73). The POCO scores reached the maximum of 100% in several minimal to mild PCO cases. The reproducibility of the AQUA software was perfect and that of the other analysis systems, comparably satisfactory. Conclusion: The objective AQUA score correlated well with subjective methods including the EPCO system. The POCO system, which assesses PCO area, did not adequately describe PCO intensity and includes a subjective step in the analysis process. The AQUA system could become an important tool for randomized masked trials of PCO inhibition.

Effect of a silicone intraocular lens with a sharp posterior optic edge on posterior capsule opacification

Purpose: To compare the inhibiting effect on posterior capsule opacification (PCO) of a silicone intraocular lens (IOL) with a sharp posterior optic edge (ClariFlex OptiEdge®, Advanced Medical Optics) and a silicone IOL with a round optic edge (PhacoFlex SI‐40, Advanced Medical Optics). Setting: Department of Ophthalmology, University of Vienna, Vienna, Austria. Methods: This prospective randomized patient‐ and examiner‐masked study comprised 104 eyes of 52 patients with bilateral age‐related cataract. All patients had cataract surgery in both eyes and received a sharp‐edged IOL in 1 eye and a round‐edged IOL in the other eye. Postoperative examinations were at 1 week, 1 and 6 months, and 1 year. Digital slitlamp and retroillumination images were taken of each eye. The amount of PCO was assessed subjectively at the slitlamp and objectively using Automated Quantification of After‐Cataract (AQUA) automated‐image analysis software. Results: The sharp‐edged IOL group had significantly less regeneratory and fibrotic PCO 1 month, 6 months, and 1 year after surgery. The mean AQUA PCO score (scale 0 to 10) was 0.71 in the sharp‐edged IOL group and 1.40 in the round‐edged IOL group (P<.001). The sharp‐edged IOL group had less peripheral fibrotic PCO. There was no significant difference between the 2 IOL groups in patient reports of edge glare. Conclusion: The sharp‐edged design of the ClariFlex OptiEdge silicone IOL led to significantly less PCO than the round‐edged PhacoFlex SI‐40 IOL 1 year postoperatively.

High precision biometry of pseudophakic eyes using partial coherence interferometry

Purpose: To investigate the applicability of the scanning version of dual‐beam partial coherence interferometry (PCI) for measuring the anterior segment and axial length of pseudophakic eyes in a clinical setting and to determine the achievable precision with this biometry technique. Setting: Department of Ophthalmology, Vienna General Hospital, and Institute of Medical Physics, University of Vienna, Austria. Methods: Partial coherence interferometry was performed in 39 pseudophakic eyes of 39 patients after implantation of a foldable acrylic intraocular lens (IOL). Results: Effective lens position (ELP), IOL thickness, and lens‐capsule distance (LCD) were determined with a precision of 2 to 3 &mgr;m; corneal thickness and axial eye length, with a precision of 0.8 and 5.0 &mgr;m, respectively. The mean ELP of the IOL was 4.093 mm ± 0.290 (SD). In 7 eyes (18%), a positive LCD of 68 ± 40 &mgr;m was detected with PCI. Mean corneal thickness was 526.4 ± 31.5 &mgr;m; mean IOL thickness, 791.5 &agr; 40.2 &mgr;m; and mean axial length, 23.388 ± 0.824 mm. Conclusion: The scanning version of PCI enables high precision (≤5 &mgr;m) and high resolution (∼12 Fun) biometry of pseudophakic eyes that is better than conventional ultrasound by a factor of more than 20. For the first time, positive LCD, a possible risk factor for posterior capsule opacification, could be detected and quantified. Furthermore, this technique offers a high degree of comfort for the patient since it is a noncontact method with no need for local anesthesia or pupil dilation and has a reduced risk of corneal infection.

Local tumor control and morbidity after one to three fractions of stereotactic external beam irradiation for uveal melanoma

BACKGROUND AND PURPOSE To evaluate prospectively local tumor control and morbidity after 1-3 fractions of stereotactic external beam irradiation (SEBI) in patients with uveal melanoma, unsuitable for ruthenium-106 brachytherapy or local resection. MATERIAL AND METHODS This phase I/II study includes 62 selected patients with uveal melanoma. The mean initial tumor height was 7.8+/-2.8 mm. With the Leskell gamma knife SEBI, 41 patients (66%) were irradiated with two equal fractions of 35, 30 or 25 Gy/fraction, 14 patients (22%) were treated with three fractions of 15 Gy each, and seven patients (11%) with small tumor volumes below 400 mm(3) were treated with one fraction of 45 Gy. The mean total dose was 54+/-8 Gy. The minimal follow-up period was 12 months, and the median follow-up was 28.3 months. Data on radiation-induced side-effects were analyzed with the Cox proportional hazards model for possible risk factors. RESULTS Local tumor control was achieved in 98% and tumor height reduction in 97%. The mean relative tumor volume reductions were 44, 60 and 72% after 12, 24 and 36 months, respectively. Seven patients developed metastases (11%). Secondary enucleation was performed in eight eyes (13%). Morbidity was significant in tumors exceeding 8 mm in initial height; it was comparable and acceptable in those smaller. In the stepwise multiple Cox model, tumor localization, height and volume, planning target volume (PTV), total dose and patient age were identified as the strongest risk factors for radiation-induced lens opacities, secondary glaucoma, uveitis, eyelash loss and exudative retinal detachment. In this model, the high-dose volume irradiated with more than 10 Gy/fraction was the strongest risk factor for radiation-induced uveitis. CONCLUSIONS Stereotactic external photon beam irradiation and a total dose of 45-70 Gy delivered in one to three fractions are highly effective at achieving local tumor control in uveal melanoma. Further clinical studies using smaller fraction doses, and consequent smaller high-dose volumes, are justified to optimize dose and fractionation. Fractionated stereotactic irradiation has a challenging potential as an eye-preserving treatment in uveal melanoma.

Dual-beam optical coherence tomography: signal identification for ophthalmologic diagnosis

The dual beam version of optical coherence topography can be used for noninvasive, high-resolution imaging of the human eye fundus, enabling in vivo visualization of retinal morphology as well as accurate quantification of the thickness profiles of its layers. Interferometric fundus signals-optical A-scans-and retinal tomograms of patients with glaucoma, diabetic retinopathy, and age-related macular degeneration are compared with those of healthy, normal subjects to elucidate the origin of the signal peaks detected and to investigate and interpret the retinal microstructures contained in the cross-sectional images.

Intraocular lens movement caused by ciliary muscle contraction

Purpose: To investigate intraocular lens (IOL) movement, measured as a change in anterior chamber depth (ACD) caused by pilocarpine‐induced ciliary muscle contraction. Setting: Department of Ophthalmology, University of Vienna, Vienna, Austria. Methods: In this prospective study, the ACD was measured using high‐precision, high‐resolution, dual‐beam partial coherence interferometry in 62 pseudophakic eyes of 55 patients under pilocarpine‐ and cyclopentolate‐induced ciliary muscle contraction and relaxation. The following were studied: 2 models of a ring‐haptic IOL (designed to accommodate), a plate‐haptic IOL, and 3 types of 3‐piece IOLs. Measurements were performed 3 months after surgery. Results: The ring‐haptic IOLs and plate‐haptic IOL showed a forward movement (ring haptic 43A, −116 &mgr;m; ring haptic 43E, −222 &mgr;m; plate haptic −162 &mgr;m). The 3‐piece IOLs showed no change in ACD except in 1 IOL type in which there was backward movement (156 &mgr;m). Conclusions: Pilocarpine‐induced ciliary muscle contraction caused forward movement of ring‐ and plate‐haptic IOLs that resulted in an estimated accommodative amplitude of less than 0.50 diopter in most cases. The accommodating ring‐haptic IOLs did not perform better than the conventional plate‐haptic IOL.

Prediction of pseudophakic capsular bag diameter based on biometric variables.

PURPOSE To measure the capsular bag diameter (CBDm) in vivo and calculate a regression formula for future preoperative prediction of capsular bag diameter (CBDp). SETTING Department of Ophthalmology, University of Vienna, Austria. METHODS This prospective study comprised 70 eyes having cataract surgery with implantation of an open capsular tension ring (CTR) (Morcher Type 14). Within the first postoperative days, the distance between the ends of the CTR were measured through a gonioscopy lens by adjusting the slit height. This distance was added to the known length of the CTR to calculate the capsular bag circumference and from this, the CBDm. The CBDm was correlated with axial eye length (AL), corneal power (P), preoperative anterior chamber depth and lens thickness, corneal diameter, and age. A stepwise multiple regression analysis was computed with CBDm as the dependent variable. RESULTS The mean CBDm was 10.37 mm +/- 0.25 (SD). A statistically significant negative correlation was found between CBDm and P (P < .0004; r2 = 0.16) and a positive correlation between CBDm and AL (P < .0226, r2 = 0.07). Stepwise multiple regression resulted in the following regression formula: CBDp = 3.44 to 0.056 x P + 0.713 x AL - 0.0135 x AL2 (P < .0001; r2 = 0.3145). Using this formula with the individual Ps and ALs, all 6 eyes with a large capsular bag diameter (CBDm > 10.7 mm) and 10 of 13 eyes with a small one (CBDm < 10.1 mm) were correctly classified. CONCLUSION The capsular bag diameter in vivo correlated negatively with corneal power (P) and positively with AL. The regression formula used may serve as a tool for preoperative identification of eyes with a very large or very small CBDm.

Cellular invasion on hydrogel and poly(methyl methacrylate) implants an in vivo study

ABSTRACT Over a two‐year postoperative period, cells on hydrogel (poly HEMA) and poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) were observed by specular microscopy. First small, round cells and fibroblast‐like cells and later epithelioid‐like cells and foreign‐body giant cells could be seen on both IOL types. In eyes with prolonged postoperative inflammation a greater number of cells was observed and the cells remained on the IOL surface for a longer period. We found fewer cell reactions on hydrogel IOLs during the postoperative period of our follow‐up. Foreign‐body giant cells were observed on only 9%. These cells were smaller than those on PMMA IOLs. This finding may suggest that poly HEMA demonstrates greater biocompatibility, with regard to this foreign‐body cell reaction, than PMMA. However, we found more pigment dispersion (50%) on the surface of hydrogel IOLs. These pigment deposits induced no cell reactions and there was less phagocytosis of the pigment debris. In 7% of the cases, dust‐like, white precipitates of uncertain origin were seen; in 5% amorphous debris was seen. Fine scratches caused by polishing during the manufacturing process were seen in some cases. The postoperative clinical signs for PMMA and hydrogel IOLs were similar.