[Morphologic Corneal Changes after Crosslinking for Keratoconus]. / Morphologische Hornhautveränderungen nach Crosslinking bei Keratokonus.

Keratoconus is a relatively common (1 : 2000) bilateral disease leading to a change in biochemical and biomechanical corneal structure as well as thinning and ectasia. For more than 10 years, crosslinking has been a therapeutic option in cases of progression. Using riboflavin and UVA-radiation, the anterior corneal stroma (300 µm) gets stiffened by crosslinking of collagen fibers. When protocols and limitations are adhered, the procedure is described to be effective and of low-risk. This review gives an overview about physiologic and pathologic changes in keratoconic corneas before and after crosslinking. Based on histopathologic examination, the current knowledge in published literature is reviewed and is complemented by our own investigations.

[Iatrogenic Keratectasia: A Review]. / Iatrogene Keratektasie - eine Übersicht.

Iatrogenic corneal ectasia is a rare complication but also one of the most feared situations that can occur after uneventful corneal laser surgery. Ectatic changes can occur as early as 1 week or can be delayed up to several years after LASIK. The actual incidence of ectasia is undetermined, an incidence rate of 0.04 to almost 2.8 % has been reported. Ectasia is most common following LASIK; however, cases have been reported following PRK and other corneal refractive procedures. Keratectasia shows progressive myopia, irregular astigmatism, ghosting, fluctuating vision and problems with scotopic vision. The progression leads to severe loss of corrected visual acuity. Risk factors are thin corneas < 500 µm, a pathological corneal topography, a residual stromal bed < 300 µm, high myopia > 8 D, young (female) age < 25 years, atopic dermatitis, allergies, family history for keratokonus and collagen diseases and retreatments. Treatment of choice is a cross-linking with riboflavin/UVA light with contact lenses. In severe cases a penetrating or a deep anterior lamellar graft is necessary.

[Surgical treatment of neovascular glaucoma]. / Operative Therapie des Neovaskularisationsglaukoms.

PURPOSE: The neovascular glaucoma is one of the leading causes for an enucleation. The cyclocryocoagulation, the peripheral retinal cryocoagulation and the intravitreal injection of bevacizumab as combined therapy aim at the reduction of the intraocular pressure and of neovascularisation. MATERIALS AND METHODS: This study follows up 135 patients with neovascular glaucoma who underwent the above-mentioned combined therapy consisting of cyclocryocoagulation, peripheral retinal cryocoagulation and intravitreal injection of bevacizumab. RESULTS: The most common causes of neovascular glaucoma in our study are diabetic retinopathy and central retinal vein occlusion. The intraocular pressure was 37.4 mmHg (± 15.8) mmHg preoperatively under maximum antiglaucomatous therapy and was reduced to 19.0 (± 8.5) mmHg direct postoperatively. In the long-term intraocular pressure remained within the normal range in 93.33 % of patients. A successful reduction of the local antiglaucomatous drops of 1.9 substances to 1.7 substances was observed after 3 months. The oral intake of acetazolamide was also statistically significantly reduced. 47.37 % of the patients were normotensive without local therapy and only 3 patients were still on acetazolamide even after 1 year. The most serious complication was a phthisis bulbi in 1.5 % of patients. Overall 98.5 % of patients remained free of pain and maintained visual acuity after the end of the follow-up. CONCLUSION: Long-term pressure regulation and freedom from pain were successfully achieved. For decompensated neovascular glaucoma with poor vision and painful bulb, the combination of retinal cryocoagulation and intravitreal application of bevacizumab is an important therapeutic option.

[Influence of corneal transparency on the quality of topographies]. / Einfluss der hornhauttransparenz auf die qualität von topografien.

Corneal topographs that measure the anterior and posterior corneal surface with optical methods need a clear cornea for precise measurements. Opacities cause artifacts in the corneal thickness (with measurements usually being too thin) and corneal curvatures. This is important to know as certain pathologies may repeatedly cause similar artifacts. This is highly relevant after a corneal cross-linking, Lasek or PRK, as these procedures cause typical artifacts that can easily be misinterpreted.

[One-year results after Cypass implantation]. / 1-Jahres-Ergebnisse nach Cypass-Implantation.

BACKGROUND: The Cypass Microstent (Transcend Medical, Menlo Park, CA, USA) is a biocompatible polyamide implant that is implanted in the suprachoroidal space and improves the flow of the aqueous humour via the uveoscleral pathway. MATERIAL AND METHODS: In a retrospective clinical study 162 patients (220 eyes) with an average age of 71.8 (±14.2) years with a mild to moderate glaucoma were treated with a Cypass implant. In the study three groups of patients (group 1, group 2 and group 3) were formed. Group 1 included patients with pseudophakia who received a Cypass implant, group 2 consisted of patients with a Cypass implant combined with phacoemulsification and implantation of an intraocular lens (Phako/HKL) and group 3 included patients who had had multiple eye surgeries before the Cypass implantation. The follow-up period of the study was 1 year. RESULTS: The mean preoperative intraocular pressure (IOP) in group 1 was 20.0 (±8.4) mm Hg and in group 2 was 20.8 (±8.7) mm Hg. The mean IOP fell to 17.7 (±7.1) mm Hg in group 1 (pressure reduction: 11.7%, p < 0.05) and in group 2 to 18.0 (±7.0) mm Hg (pressure reduction: 13.4%, p > 0.05) 12 months postoperatively. The decrease of IOP in group 3 after 1 year was 11.2%. In 20.5% of the cases (45 eyes), additional operative pressure reducing interventions was performed because the target pressure was not achieved. CONCLUSION: After 1 year patients in group 2 showed a significantly similar reduction in pressure as group 1. Additionally, both groups showed a reduction in the number of locally applied antiglaucoma agents. The reduction of the IOP in group 3 was not significant after 12 months, in contrast to the other two groups.

[Collagen crosslinking with riboflavin and UVA-light in keratoconus]. / Kollagen-Crosslinking mit Riboflavin und UVA-Licht beim Keratokonus.

Reduced corneal mechanical stability in keratoconus and similar corneal diseases can be treated by photooxidative crosslinking of the corneal collagen. This method is currently undergoing clinical evaluation worldwide. To achieve high absorption of the irradiation energy in the cornea, riboflavin at a concentration of 0.1% and UVA light at a wavelength of 370 nm corresponding to the relative maximum of absorption of riboflavin (vitamin B2) is used. These therapeutic parameters were experimentally tested and have been proven clinically. Current data demonstrate that the therapeutic crosslinking procedure is safe when the important theoretical and clinical parameters are observed, and that progression of keratoconus can be prevented. In all, 80% of the published cases show a decrease in corneal curvature of about 2 D, which leads not only to stabilisation but also to an increase in visual acuity.

[Enzymatic evidence of the depth dependence of stiffening on riboflavin/UVA treated corneas]. / Enzymatischer Nachweis der Tiefenabhängigkeit der Vernetzungswirkung von Riboflavin/UVA an der Hornhaut.

PURPOSE: It has been shown that the treatment of keratoconus with riboflavin/ultraviolet A (UVA) causes significant stiffening of the cornea due to cross-linking. The aim of this study was to evaluate how deep the mechanical stabilization after collagen cross-linking could be shown biochemically. METHOD: Ten out of 20 enucleated porcine eyes were treated with riboflavin as a photosensitizer and UVA (370 nm, 3 mW/cm2, 30 min). The other 10 eyes served as controls. With a Microkeratom device, two flaps with a thickness of 200 microm and a diameter of 8 mm were cut off from each eye and put in a collagenase solution (NaCl plus collagenase A, 1:1). The surfaces of the flaps were measured digitally every day to characterize the dissolving behavior. RESULTS: The resistance (regarding corneal collagen against enzymatic digestion) of the treated superficial flaps was considerably higher (p=0.001) compared to those that were cut secondarily and to the control flaps. But even the flaps from deeper layers showed a significant increase in resistance (p=0.02) compared with the untreated flaps. The half-life of the surfaces of the treated superficial flaps was 220 h; of those cut secondarily, it was 80 h. Both untreated flaps had a half-life of 50 h. CONCLUSIONS: The biochemical study showed that the treatment of the cornea with riboflavin/UVA leads to significant collagen cross-linking not only in the anterior slice of 200 microm but also in the following 200 microm. This locally limited cross-linking effect may be explained by the absorption behavior for UVA of the riboflavin-treated cornea; 65% of UVA irradiation is absorbed in the first 200 microm and only 25-30% in the next 200 microm. Therefore, deeper-lying structures and especially the endothelium are not affected.

[Severe Aspergillus endophthalmitis occurring after liver transplantation in an 8-month-old baby]. / Aspergillus-Endophthalmitis nach Lebertransplantation bei einem Säugling.

Immunosuppressed patients and transplant patients bear an increased risk for invasive aspergillosis and Aspergillus endophthalmitis. An 8-month-old boy developed severe unilateral panuveitis after liver transplantation. Bronchopulmonary infiltrates were present, but a pulmonary Aspergillus infection was not confirmed. An enucleation was performed in order to prevent a life-threatening disseminated Aspergillus infection.

[Complications and postoperative therapeutic strategies in cross-linking]. / Komplikationen und postoperative Therapiestrategien beim Crosslinking.

CLINICAL ISSUE: The reduced corneal mechanical stability in keratoconus and similar collagen diseases can lead to a progressive and irregular corneal shape and decrease of visual acuity. DIAGNOSTICS: A progression of keratectatic diseases can be shown with corneal topography. TREATMENT: Keratoconus can be treated by photo-oxidative cross-linking of the corneal collagen. In order to achieve a high absorption of irradiation energy in the cornea, riboflavin at a concentration of 0.1% and UVA light at a wavelength of 370 nm corresponding to the relative maximum absorption of riboflavin (vitamin B2) are used. Evidence for corneal cross-linking are the increase of biomechanical stiffness, the increased resistance against enzymatic degradation, a higher shrinkage temperature, a lower swelling rate and an increased diameter of collagen fibers. The currently available data demonstrate that the therapeutic cross-linking procedure is safe when respecting the important theoretical and clinical parameters and that a progression of the keratoconus can be avoided. In 80% of cases an average levelling of the curvature of approximately 2 dpt can be achieved, which leads not only to stabilization but also to an increase in visual acuity of approximately 1.2 lines. ASSESSMENT: In a Cochrane review from 2015 publications about complications and results were reviewed. Complication rates ranged from 1-10% depending on the initial situation, comorbidities and stage of the keratoconus. The most important complications are early epithelial wound healing problems as well as extremely rare perforations. PRACTICAL RECOMMENDATIONS: Corneal cross-linking is a well-established and safe procedure but is not free of complications.

[Juvenile idiopathic epiretinal membrane]. / Juvenile idiopathische epiretinale Membran.

Idiopathic epiretinal membrane (iERM) is very rare in adolescent patients. The pathogenesis remains unclear although the role of hyalocytes is of major importance. The clinical features in young patients are different from those in older patients. We describe a case of iERM in a 15-year-old girl who presented with metamorphopsia of the right eye. This case report presents the basis for the decision for surgical treatment as well as the clinical features at follow-up examination 9 months after surgery.

[Low grade endophthalmitis caused by P. acnes : Case report]. / Low-grade-Endophthalmitis verursacht durch P. acnes : Eine Kasuistik.

Low grade endophthalmitis is usually a chronic indolent inflammation that may be misdiagnosed as noninfectious uveitis. Therefore, this form of endophthalmitis is often unsuccessfully treated with corticosteroids. We describe the case of a patient with low grade endophthalmitis caused by Propionibacterium acnes after cataract surgery. This case report presents the difficulties in establishing the diagnosis of this form of endophthalmitis as well as the benefits of a combined operative therapy with pars plana vitrectomy, intravitreal antibiotics and posterior capsulectomy for successful treatment in such cases.

[Glaucoma diagnostics and corneal thickness]. / Glaukomdiagnostik und Hornhautdicke.

In recent years the role of pachymetry in the correction of applanation tonometry values was controversially disputed. At the present time it is undoubtedly proven that central corneal thickness affects the accuracy of applanation tonometry. The dimension of this influence is 1 mmHg of pressure per 25 microm of change in corneal thickness. It is important to remember that Goldmann and Schmidt calibrated the applanation tonometer according to the central corneal thickness of their population by using the optical method. Therefore, it is first necessary to determine the corneal thickness for each examiner and his methods. The linear correction formula should be used only in the range of corneal thickness in which the formula was determined. The correction according to Orssengo and Pye and further developments in tonometry may offer alternatives for better estimation of intraocular pressure.

[The German Acanthamoeba keratitis register: Initial results of a multicenter study]. / Das Deutsche Akanthamöbenkeratitis-Register : Erste Ergebnisse einer multizentrischen Erhebung.

BACKGROUND AND PURPOSE: In September 2011 the cornea section of the German Ophthalmological Society (DOG) established the first German Acanthamoeba keratitis registry. The data of this multicenter survey are being collected, compiled and evaluated at the Department of Ophthalmology at the Saarland University. The aim of this article is to present an intermediate report. PATIENTS AND METHODS: Data from 172 eyes with Acanthamoeba keratitis were collected during the last 10 years. For this interim report we actually evaluated 121 eyes (60.2 % female patients, average age 41.3 years) and collected the following data: date of onset of symptoms, date and method of diagnosis, initial diagnosis, anamnestic data, clinical symptoms and signs at diagnosis and during follow-up, conservative and surgical therapy. Criteria for inclusion in the Acanthamoeba registry was the established diagnosis of an Acanthamoeba keratitis with at least one of the methods described in this article. RESULTS: Acanthamoeba keratitis could be histologically proven in 55.3 % of the cases, via PCR in 25.6 %, with confocal microscopy in 20.4 % and using in vitro cultivation in 15.5 %. Clinical symptoms and signs in Acanthamoeba keratitis were pain in 67.0 %, ring infiltrates in 53.4 %, pseudodendritiform epitheliopathy in 11.7 % and keratoneuritis in 5.8 %. In 47.6 % of the cases the initial diagnosis was herpes simplex virus keratitis followed by bacterial keratitis in 25.2 % and fungal keratitis in 3.9 %. Acanthamoeba keratitis was the correct initial diagnosis in only 23.2 % of cases. The average time period between first symptoms and diagnosis was 2.8 ± 4.0 months (range 0-23 months). A triple therapy with Brolene® Lavasept® and antibiotic eye drops at least 5 ×/day was used in 54.5 % of eyes (n = 66). Penetrating keratoplasty was performed in 40.4 %, in 18 cases in combination with cryotherapy of the cornea. The mean graft diameter was 7.9 ± 1.1 mm (range 3.5-11.0 mm). The final visual acuity (Snellen visual acuity chart at 5 m) was comparable in the two groups of eyes with (5/40 ± 5/25) and without (5/32 ± 5/25) keratoplasty. CONCLUSION: Acanthamoeba keratitis is a rare and often very late diagnosed disease and two thirds of the cases were initially misdiagnosed. The early recognition of the typical symptoms is crucial for the prognosis of the disease. All ophthalmological departments in Germany are invited to submit further data of all confirmed cases (berthold.seitz@uks.eu), whether retrospectively or prospectively in order to generate an adequate standardized diagnostic and therapeutic approach for this potentially devastating disease.

Mechanical stability of the cornea after radial keratotomy and photorefractive keratectomy.

BACKGROUND: Corneal refractive surgical procedures alter the shape and structure of the tissue, possibly compromising its mechanical stability. METHODS: One or both eyes of 87 subjects were studied: 26 of these 87 had been treated for myopia by excimer laser ablation and 36 by radial keratotomy; 25 without previous corneal surgery functioned as controls. Corneal topography was evaluated by TMS-1 videophotokeratography before and after 180 degrees tilting of the patient, and the pressure-induced ring-wise changes in spherical equivalent power (axial power) were calculated. Changes in corneal shape also were evaluated by computing the instantaneous radius of curvature. The intraocular pressure was measured before and after tilting by a hand-held applanation tonometer. RESULTS: The mean intraocular pressure increased from 13.9 +/- 2.3 mm Hg before tilting to 30.0 +/- 3.8 mm Hg during tilting. In the control eyes, the mean power of the central cornea during tilting decreased 0.187 +/- 0.045 diopters (D) (p < .05); in the excimer-laser-ablated eyes, 0.038 +/- 0.056 D (not statistically significant); and in those treated with radial keratotomy, 0.523 +/- 0.054 D (p < .01). After radial keratotomy, the cornea steepened outside the clear zone in response to pressure loading, whereas it did not change significantly in the laser-ablated or control eyes. CONCLUSIONS: Pressure-induced deformation of normal and excimer laser-ablated human cornea is small, whereas radially incised corneas have significantly decreased mechanical stability.

Vacuum fixation of corneal lenticules for refractive surgery.

Using the rotating lamellar keratome, a simplified method for nonfreeze shaping of corneal tissue was developed. A set of refractive molding forms was designed for a standardized lenticule diameter. The fixation of the lenticule was achieved by a system of suction holes. A mechanical fixation ring was not required, as the total shearing force exerted by the rotating blade is neutralized even by a low suction setting. Different surface properties (polished, matt, rough) were compared, showing an influence of the surface structure on friction and thus lenticule fixation. With our optimized molding form, the lenticule is safely retained at a suction of 2.5 m H2O.

Corneal sensation after cataract and refractive surgery.

Most surgical procedures involving the anterior segment of the eye disrupt the normal organization of corneal innervation. Since denervation of the cornea results in impaired epithelial wound healing, increased epithelial permeability, decreased epithelial metabolic activity, and loss of cytoskeletal structures associated with cellular adhesion, it is important to identify the factors that determine the extent of neural regeneration. Mechanisms of corneal nerve damage and studies of corneal nerve fiber loss and reinnervation after cataract and refractive surgery--epikeratophakia, cryokeratomileusis, keratomileusis in situ, photorefractive keratectomy, laser in situ keratomileusis, and phacoemulsification--are reviewed and the decrease in corneal sensitivity, as a measure of corneal destruction and corneal metabolism, after these surgical procedures is compared.

[Experiences with "reversed tip and snip" phacoemulsification]. / Erfahrungen mit der "Reversed Tip and Snip"-Phakoemulsifikation.

UNLABELLED: The endothelial cell count after phacoemulsification serves as a sensitive indicator for the level of corneal traumatization caused by different phacoemulsification techniques concerning the used phacotime and phacoenergy/s. PATIENTS: In a prospective and randomized study, the "reversed tip and snip" technique and the "divide and conquer" technique were performed in groups of 30 patients each. The corneal endothelial cell count was measured preoperatively as well as 4 weeks and 3 months postoperatively. In a second study the phacotime and phacoenergy used/second and the endothelial cell loss were compared between patients 1-30 and 31-60 who were operated on with the "reversed tip and snip" technique, demonstrating the learning curve of this technique. RESULTS: The endothelial cell count showed significant (P < 0.001) reduction by about 10% after the "reversed tip and snip" technique and by about 15% after the "divide and conquer" technique. The latter produced significantly greater cell loss. The phacotime (mean: 22-17) and phacoenergy/s (mean: 23-16) were reduced significantly (P < 0.05) when patients 1-30 were compared with 31-60. CONCLUSION: The "reversed tip and snip" phacoemulsification technique produces less endothelial cell loss than the "divide and conquer" technique. There is a short learning curve by using the "reversed tip and snip" technique.

[Effect of corneal hydration and dehydration of donor tissue on the precision of the thickness in lamellar refractive keratoplasty]. / Einfluss der Hornhautquellung und Entquellung des Spendergewebes auf die Dickenpräzision bei der lamellären refraktiven Keratoplastik.

The influence of corneal hydration on the precision of plano lamellas and on the precision of lenticles modified with a "non-freeze" technique was studied in pig eyes. Ten pig eyes were dissected with a rotating lamellar microkeratome, and the discs were measured with a mechanical pachymeter. The hydration of the discs was measured in BSS and in dextran solution. A total of 160 corneal discs with different degrees of hydration were modified with a "non-freeze" technique on concave anf convex vacuum cylinders and measured with a photokeratoscope TMS. The discs increased in thickness within 3 h becoming 1.7 times as thick in BSS and 1.2 times as thick in dextran. After refractive dissection minor modifications were achieved with higher precision than were larger corrections. However, we achieved an undercorrection after all refractive dissections. Plano-discs for refractive modification should be taken from dehydrated corneoscleral discs or from intact eyes. Owing to mechanical factors during cutting and tissue hydration undercorrection of the intended change was observed.

[Cyclocryocoagulation in treatment of special types of glaucoma]. / Zyklokryokoagulation bei der Behandlung spezieller Glaukomformen.

In this retrospective study, we examine the efficiency of cyclocryocoagulation in eyes with secondary and congenital glaucoma. We studied 137 eyes with advanced, inadequately controlled glaucoma, which were operated from 1984 to 1993. Besides the intraocular pressure (IOP), we assessed the effect on the visual acuity and the optic nerve. We also compared the efficiency of two different cryomethods (CO2/N2 cyclocryocoagulation). Fifty eyes were cyclocryocoagulated with CO2 and 87 with N2. After a period of 6 months, 90 eyes were regulated (IOP between 7 and 21 mm Hg). At this time the mean IOP was 16 mmHg, whereas it had been 40 mm Hg before the cyclocryocoagulation. Serious complications like a phthisis bulbi were seen in only 18 eyes. Five eyes became blind despite therapy because of an absolute glaucoma. Concerning the different types of glaucoma, the neovascular glaucoma was the most difficult type to regulate. We obtained better and more lasting results with N2 cyclocryocoagulation (68% regulation) than with CO2 cyclocryocoagulation (62% regulation). Thus, cyclocryocoagulation represents a good method for the treatment of advanced, inadequately controlled glaucoma eyes when other methods have failed.

[Precision of lenticular thickness in relation to full stroma corneal thickness. Experimental results with the lamellar microkeratome]. / Lentikeldickenpräzision in Abhängigkeit von den Gewebeausgangsdicken. Experimentelle Ergebnisse mit dem lamellären Mikrokeratom.

In this study 150 pig corneas and 20 human corneas were dissected with an automatic rotating microkeratome for lamellar grafting. The cornea thickness varied between 0.507 mm and 0.829 with an average 0.66 mm. The aim of this investigation was to show the influence of corneal thickness, the chosen diameter and spacing on the precision of cutting lenticles. We did ten series: the pig corneas were dissected at three different intervals of 0.15, 0.25, 0.35 mm and diameters of 9 and 6mm. The human corneas were cut at intervals of 0.4 mm and 0.25 mm and with diameter of 9 and 7 mm. Although the pig corneas were fresh, the intraocular pressure was too low. It was raised with an injection of physiological salt solution to a predefined level. The rotating speed of the trephine blade, the speed of blade advancement and lubrication fluid were kept constant. Ultrasound pachymetry was performed on the center of the corneas before cutting had on the lenticles afterward. We showed that a thick corneal diameter had a negative influence, i.e., the greater the diameter, the lesser the precision; the same was true for the corneal thickness. On the other hand, the intervals had just the opposite effect: the closer they were, the better the correlation. The human eye results were different in quantity but not in tendency, with less striking effects. The average variation for pig corneas was 22% and for human eyes 8%. The best results were received with a large interval, a small diameter, and a normal corneal thickness in human eyes.