Hans Hoerauf

Slit-lamp-adapted optical coherence tomography of the anterior segment

Abstract · Purpose: To evaluate the diagnostic potential of a slit-lamp-adapted optical coherence tomography (OCT) system as an in vivo imaging device for routine clinical examination of the anterior segment of the eye. · Patients and methods: In a pilot study, healthy volunteers and patients with different pathologies of the anterior segment were examined with a slit-lamp-adapted OCT system using 100–200 axial scans with 100-Hz line-scan frequency. The scan length is variable up to 7 mm, and the axial depth is 1.5 mm in tissue. · Results: The slit-lamp-adapted OCT system allowed direct biomicroscopic imaging of the measured area. Anatomic structures and morphological changes anterior to the attenuating iris pigment epithelium could be visualized with high accuracy. Biometric analyses of the cornea, the chamber angle, the iris and secondary cataract were possible. Complete demonstration of the chamber angle was difficult due to the backscattering properties of the anterior part of the sclera and the consequent shadowing of the most peripheral part of the iris. · Conclusions: Slit-lamp-adapted OCT is a useful diagnostic tool which allows in vivo microscopic cross-sectional imaging of the anterior segment and precise measurement of ocular structures.

TREAT-AND-EXTEND REGIMENS WITH ANTI-VEGF AGENTS IN RETINAL DISEASES: A Literature Review and Consensus Recommendations.

Purpose: A review of treat-and-extend regimens (TERs) with intravitreal anti–vascular endothelial growth factor agents in retinal diseases. Methods: There is a lack of consensus on the definition and optimal application of TER in clinical practice. This article describes the supporting evidence and subsequent development of a generic algorithm for TER dosing with anti–vascular endothelial growth factor agents, considering factors such as criteria for extension. Results: A TER algorithm was developed; TER is defined as an individualized proactive dosing regimen usually initiated by monthly injections until a maximal clinical response is observed (frequently determined by optical coherence tomography), followed by increasing intervals between injections (and evaluations) depending on disease activity. The TER regimen has emerged as an effective approach to tailoring the dosing regimen and for reducing treatment burden (visits and injections) compared with fixed monthly dosing or monthly visits with optical coherence tomography–guided regimens (as-needed or pro re nata). It is also considered a suitable approach in many retinal diseases managed with intravitreal anti–vascular endothelial growth factor therapy, given that all eyes differ in the need for repeat injections. Conclusion: It is hoped that this practical review and TER algorithm will be of benefit to health care professionals interested in the management of retinal diseases.

Corneal Optical Coherence Tomography Before and Immediately After Excimer Laser Photorefractive Keratectomy

PURPOSE To investigate the representation of the corneal structure with optical coherence tomography before and immediately after excimer laser photorefractive keratectomy. METHODS Twenty-four eyes of 24 patients with myopia and myopic astigmatism were prospectively studied. The corneal thickness and the corneal profile were assessed with slit-lamp-adapted optical coherence tomography preoperatively and immediately after excimer laser photorefractive keratectomy. RESULTS The attempted mean spherical equivalent of the refractive corrections was -6.7 +/- 3.6 (mean +/- SD) diopters with a mean calculated stromal ablation depth of 91 +/- 38 microm. The corneal optical coherence tomography was reproducible in all patients, demonstrating a mean decrease of central corneal thickness after epithelial debridement and excimer laser photorefractive keratectomy of 118 +/- 45 microm. The comparison of the calculated stromal ablation depth and the corneal thickness changes determined by corneal optical coherence tomography revealed a significant linear relationship with a correlation coefficient of 0.88 (P <.001). The flattening of the corneal curvature was confirmed in all patients with the optical coherence tomography system and correlated with the attempted refractive correction (r =.82, P <.001). CONCLUSIONS The slit-lamp-adapted optical coherence tomography system presented in this study allowed noncontact, cross-sectional, and high-resolution imaging of the corneal configuration. This initial clinical evaluation demonstrated that corneal optical coherence tomography could be a promising diagnostic modality to monitor corneal changes of thickness and curvature before and after excimer laser photorefractive keratectomy.

New substances for intraocular tamponades: perfluorocarbon liquids, hydrofluorocarbon liquids and hydrofluorocarbon-oligomers in vitreoretinal surgery.

Abstract. Perfluorocarbon liquids (PFCLs) and heavy fluorocarbon liquids (HFCLs) are being increasingly used as soft tools during vitreoretinal surgery. However, since long-term intraocular tolerance is still unsatisfactory, at present complete removal at the end of surgery is recommended. With the aim to improve long-term intraocular compatibility and to enlarge the spectrum of clinical applications, modified HFCLs have been developed. HFCL-oligomers with a higher viscosity represent the latest perspective. All three groups of fluorocarbon liquids will be compared with respect to their physical and chemical properties, experimental and clinical results, and prospects for clinical applications. Common features of PFCLs, HFCLs and HFCL-oligomers are biological inertness, specific gravity higher than water, immiscibility with water or blood, and a high gas binding capacity. In PFCLs such as decalin, octane, or phenanthrene, all carbon atoms of the carbon backbone are completely fluorinated. In experimental and clinical use, emulsification, vascular changes and structural alterations of the retina have been described. By only partial replacement of hydrogen atoms by fluorine, the specific gravity of HFCLs is reduced, whereas lipophilic properties increase. Thus HFCLs are potential solvents for intraocular silicone oil remnants. However, after long-term application, side-effects are similar to those observed with PFCLs. Substances of this group, such as F6H6, F6H8, O44, and O62 are used intraoperatively and are currently being investigated for clinical long-term application. With the aim to avoid emulsification and to improve intraocular tolerance, we have developed HFCL-oligomers consisting of 2–4 HFCL molecules with increased viscosity. The oligomers were tolerated well in rabbit eyes for up to 4 months. In contrast to PFCLs or monomers, they did not emulsify nor show vascular alterations. ERGs returned to normal after removal of the oligomer from the eye. Histology of the retina showed mild alterations. Conclusion: according to physical properties, experimental intraocular compatibility and stability against emulsification, HFCL-oligomers are promising candidates for improved long-term tamponade of the lower retina. At present, indications for an application in human eyes have to be determined in clinical trials.

Preparation of autologous platelets for the ophthalmologic treatment of macular holes.

BACKGROUND: Platelet concentrates were recently used for ophthalmologic treatment of macular holes. This strategy was investigated to define standardized blood bank components.

Clinical findings on the use of long-term heavy tamponades (semifluorinated alkanes and their oligomers) in complicated retinal detachment surgery

Abstract Background. Heavy tamponades for pathologies in the lower part of the retina are a new development, and different tamponades have recently come into clinical use: semifluorinated alkanes (F6H6, F6H8) and their oligomers (OL62HV). Method. Nine patients had been operated on using F6H8 (n=5) and by OL62HV (n=4). In all cases the reasons for using the tamponades were complicated retinal detachments in the lower part. In three cases the use was primary and in six cases tamponades were used after reoperations. In all cases the endotamponade was removed within 6 weeks. Fluorescein angiography (FLA) was performed in the F6H8 group. Results. In the F6H8 group dispersion developed in two of the three aphacic patients. In two out of five cases soft epiretinal membranes and cellular material could be found between the substance and the lower periphery. In two membranes examined by light microscopy, cystic cells and amorphous material could be found. In one case (PDRP, aphacic) cyclophotocoagulation had to be performed because of persistent elevated IOP. FLA was unremarkable. In the OL62HV group, severe recurrent PVR reaction occurred in the lower periphery (2/4) and unusual precipitates were observed (4/4). In one case, after a normal postoperative period (VA 0.05 after 5 days) an extensive cellular reaction on the complete surface of the tamponade occurred. After 5 weeks VA was no light perception. During removal of the oligomer unusual adherent cellular components were found on the surface of the retina. The retina appeared necrotic, showed constricted retinal vessels and there was optic atrophy. Histologically, fluffy epiretinal material and a lens capsule obtained from one eye filled with OL62HV resembled the appearance with F6H8. Conclusion. Heavy endotamponades on the basis of semifluorinated alkanes can lead to an unusual biological reaction and need further investigation before clinical use.

Corneal shape changes after pars plana vitrectomy

Abstract · Background: The purpose of this prospective, controlled, clinical study was to investigate corneal shape changes due to pars plana vitrectomy (PPV) in patients with potential visual improvement postoperatively. · Methods: A total of 36 consecutive patients undergoing conventional PPV combined with or without macular surgery were studied. Sequential determinations of the corneal curvature by manual keratometry and corneal topography were performed preoperatively, during the first postoperative week, at 4 weeks and after 2–8 months (mean 4 months). · Results: The mean surgically induced keratometric astigmatism was 2.92±1.98 diopters (D) (P<0.0001) during the first postoperative week. After 4 weeks and 4 months the values decreased to 1.01±0.97 D and 0.67±0.43 D, respectively. Videokeratographic analysis confirmed significant curvature changes, with corneal steepening (P<0.008) which corresponded to the superonasal and temporal semimeridian, and flattening (P<0.008) along the inferior and inferonasal semimeridians. Corneal changes persisted in some cases for several weeks, partly in an asymmetric and irregular configuration. Shifts in axis to against-the-rule and oblique meridians were noted postoperatively with redistribution within preoperative values in 53% of the cases at 4 weeks after surgery. Subgroup analysis revealed that suture diameter, as well as the use of gas endotamponade, influenced the induced astigmatism. · Conclusion: A substantial increase of the corneal astigmatism and distinct shape changes can occur after PPV in the immediate postoperative period. Consecutive stabilization at preoperative values was observed after several weeks. The time course of the corneal curvature alterations should be considered in the postoperative management to detect refractive causes of inadequate visual acuity.

Delayed intraocular lens dislocation after neodymium:YAG capsulotomy.

Abstract A poly(methyl methacrylate) (PMMA) intraocular lens (IOL) disocated into the vitreous cavity in 2 patients after a neodymium:YAG (Nd:YAG) laser posterior capsulotomy. In Case 1, the capsulotomy was performed 19 months after extracapsular cataract extraction (ECCE) and sulcus fixation of an IOL. Six months later the IOL dislocated posteriorly. In Case 2, ECCE with intracapsular IOL implantation was followed 4 years later by an Nd:YAG capsulotomy; 6 months later the IOL dislocated into the vitreous cavity within this intact capsular bag. Different mechanlsms were responsible for the dislocation; in Case 1, radial tearing of the large capsular defect with IOL loosening and dislocation into the vitreous cavity; in Case 2, zonulysis and IOL dislocation within the intact capsular bag. A neodymium:YAG capsulotomy may cause delayed IOL dislocation into the vitreous cavity.

Secondary paracentral retinal holes following internal limiting membrane removal

Aim: To report on a new postoperative finding after delamination of the internal limiting membrane (ILM) for the treatment of different macular pathologies. Methods: Seven patients are described with paracentral retinal holes, all located temporally to the macula, which developed after pars plana vitrectomy and uncomplicated ILM removal for cystoid macular oedema (n = 3), macular pucker (n = 3), and macular hole (n = 1) with the use of indocyanine green (n = 4), trypan blue (n = 1), triamcinolone acetonide (n = 1), or without dye (n = 1). Conclusion: The use of dyes has been incriminated in causing iatrogenic damage to the retina. In this series, the new observation of retinal holes in the macular area is thought to be related to the removal of the ILM itself. The authors speculate that ILM delamination may cause a retinal weakening by Müller cell damage; this may be followed by a structural breakdown and, consequently, hole formation.

First Experimental and Clinical Results With Transscleral Optical Coherence Tomography

BACKGROUND AND OBJECTIVE To evaluate the potentials of optical coherence tomagraphy (OCT) using long wavelength to penetrate highly scattering tissues of the eye and visualize the anterior chamber angle and the ciliary body. METHODS OCT images were generated by an experimental prototype in enucleated porcine eyes using as light source a superluminiscent diode with a wavelength of 1310 nm and a scan frequency of 60 Hz. The number of lateral scans was variable in a range from 100 to 400. RESULTS Infrared OCT was able to penetrate the sclera. The anterior chamber angle could be visualized completely and the ciliary body could be identified. However, it was not possible to penetrate the highly reflective iris pigment epithelium. CONCLUSION The use of infrared OCT allows penetration of the sclera, thus, providing complete visualization of the anterior chamber angle and limited demonstration of the ciliary body. Because of its higher resolution, it may represent an interesting noninvasive alternative to ultrasound biomicroscopy.