Moatasem El-Husseiny

Anatomy-Based DMEK-Wetlab in Homburg/Saar – Novel aspects of donor preparation and host maneuvers to teach Descemet Membrane Endothelial Keratoplasty

Use of Descemet Membrane Endothelial Keratoplasty (DMEK) has been limited because of problems with donor preparation, i.e. tearing of the Descemet membrane and difficulties in unfolding the Endothelium‐Descemet‐Membrane‐Layer (EDML) in the anterior chamber (AC). The purpose of this work was to describe a novel approach to teaching anatomy‐based donor and recipient preparation in a DMEK‐Wetlab. We teach successful mono‐manual donor preparation of human corneas in organ culture not suitable for transplantation, including peripheral markers for orientation. We also teach safe recipient preparation in a freshly‐enucleated pig eye in organ culture preservation medium for atraumatic introduction of the EDML roll into the AC, reliable orientation of the EDML during surgery, and stepwise unfolding within the AC. Twenty‐two candidates in the 1. Homburg Cornea Curriculum HCC 2015 who practiced both preparations using three human donor corneas and three pig eyes assessed the procedure as follows: (1) overall grade of the Wetlab 1.4 (median 1, range 1 to 2 ‐ on a scale from 1 (excellent) to 6 (terrible); (2) most participants and tutors stated that the Wetlab is most effective for colleagues who have some previous experience with corneal microsurgery. Our novel anatomy‐based approach to simulating donor preparation and graft implantation for DMEK seems to meet the expectations and requirements of colleagues with previous experience in corneal microsurgery and will help to reduce the rate of complications for incipient DMEK surgeons in the future. Clin. Anat. 31:16–27, 2018.

Ghost-image analysis in phakic intraocular lenses with central hole as a potential cause of dysphotopsia.

Purpose To analyse the optical effect of an artificial hole in the optic centre of posterior chamber phakic intraocular lenses. Setting Institute of Experimental Ophthalmology, Saarland University, Homburg/Saar, Germany. Design Experimental simulation study. Methods Four eye models with an ametropia of −4 D, −8 D, +4 D, and +8 D were created in the ray tracing software ASAP. Refractive correction of these models was implemented with a model of an Implantable Collamer Lens (ICL). Each eye was set up twice with 1 eye receiving a conventional ICL without a central hole and the second an ICL with a central hole. Ray bundles were traced for lateral visual field angles from 0 to 60 degrees in steps of 1 degree. Ray propagation and retinal illumination were then compared between the 2 ICL models. Results All eye models showed ghost images originating from the anterior surface of the ICL. Eye models with the ICL with central hole showed additional light spots in the peripheral areas of the retina originating from reflections at the cylindrical wall of the central hole in the ICL. The average intensity of ghost images in the temporal retinal hemisphere was between 30 and 40 dB less than the maximum intensity of the primary image. Conclusion A central hole within a posterior chamber phakic intraocular lens may cause stray light and ghost images (positive dysphotopsia) although the on‐axis visual quality of the eye with the ICL is mostly unaffected. Financial Disclosure The authors have no financial interest in any of the material presented in this paper.

Effect of Biometric Characteristics on the Change of Biomechanical Properties of the Human Cornea due to Cataract Surgery

Purpose. To determine the impact of biometric characteristics on changes of biomechanical properties of the human cornea due to standard cataract surgery using biomechanical analysis. Patients and Methods. This prospective consecutive cross-sectional study comprised 54 eyes with cataract in stages I or II that underwent phacoemulsification and IOL implantation. CH, CRF, IOPg, and IOPcc intraocular pressure were measured by biomechanical analysis preoperatively and at 1 month postoperatively. Changes (Δ) were calculated as preoperative value versus postoperative value. Biometrical data were extracted from TMS-5 (CSI and SAI), IOLMaster (AL), and EM-3000 (CCT and ECC) preoperatively. Results. The average values of the changes were ΔCH = −0.45 ± 1.27 mmHg, ΔCRF = −0.88 ± 1.1 mmHg, ΔIOPg = −1.58 ± 3.15 mmHg, and ΔIOPcc = −1.45 ± 3.93 mmHg. The higher the CSI the smaller the decrease in CH (r = 0.302, P = 0.028). The higher the CCT the larger the decrease in CRF (r = −0.371, P = 0.013). The higher the AL the smaller the decrease in IOPg (r = 0.417, P = 0.005). The higher the AL, SAI, and EEC the smaller the decrease in IOPcc (r = 0.351, P = 0.001; r = −0.478, P < 0.001; r = 0.339, P = 0.013). Conclusions. Corneal biomechanical properties were affected by comprehensive factors after cataract surgery, including corneal endothelium properties, biometry, and geometrical characteristics.

Histological and Biochemical Findings in Membranous Cataract

Background: In this report we present a patient with unilateral membranous cataract and describe the histological and biochemical findings accompanying this rare condition. Methods: The patient underwent an uneventful cataract extraction. Aqueous humor (20 µl) was aspirated from the anterior chamber intraoperatively and processed for fibroblast growth factor (FGF) and epidermal growth factor (EGF) using an immunoassay method (ELISA). The lens material was subjected to histological examination. Results: The patient had increased levels of FGF and EGF in the aqueous humor, as measured by ELISA. Histological examination of the lens material showed a marked fibrous metaplasia and thickening of the anterior lens capsule, while the lens epithelial cells were transformed to active myofibroblasts which generated a fibrous matrix of collagen lamellae. Unfortunately, visual function was not restored postoperatively due to underlying amblyopia. Conclusions: Our histological and biochemical findings suggest that FGF and EGF may play a key role in the formation of membranous cataract, and therefore their impact on lens physiology should be further investigated.

Penetrating Keratoplasty for Keratoconus – Excimer Versus Femtosecond Laser Trephination

Background: In case of keratoconus, rigid gas-permeable contact lenses as the correction method of first choice allow for a good visual acuity for quite some time. In a severe stage of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no more tolerated. In case of existing contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis. Methods: In case of advanced keratoconus – especially after corneal hydrops due to rupture of Descemet’s membrane – penetrating keratoplasty (PKP) still is the surgical method of first choice. Noncontact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and those with repeat grafts in case of “keratoconus recurrences” due to small grafts with thin host cornea. For donor trephination from the epithelial side, an artificial chamber is used. Wound closure is achieved with a double running cross-stitch suture according to Hoffmann. Graft size is adapted individually depending on corneal size („as large as possible – as small as necessary“). Limbal centration will be preferred intraoperatively due to optical displacement of the pupil. During the last 10 years femtosecond laser trephination has been introduced from the USA as a potentially advantageous approach. Results: Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient centration, reduces “vertical tilt” and “horizontal torsion” of the graft in the recipient bed, thus resulting in significantly less “all-sutures-out” keratometric astigmatism (2.8 vs. 5.7 D), higher regularity of the topography (SRI 0.80 vs. 0.98) and better visual acuity (0.80 vs. 0.63) in contrast to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP. Refractive outcomes of femtosecond laser keratoplasty, however, resemble that of the motor trephine. Conclusions: In contrast to the undisputed clinical advantages of excimer laser keratoplasty with orientation teeth/notches in keratoconus, the major disadvantage of femtosecond laser application is still the necessity of suction and applanation of the cone during trephination with intraoperative pitfalls and high postoperative astigmatism.

The Penetrating Keratoplasty (PKP): A Century of Success

Besides routine postoperative follow-up, the prophylaxis of complications in penetrating keratoplasty (PKP) includes special preoperative and intraoperative aspects. Preoperative prophylaxis consists of the therapy of systemic diseases and eyelid abnormalities, determining individual optimal graft size, avoiding PKP in cases of uncontrolled intraocular pressure, avoiding PKP in cases of acute corneal hydrops, pretreatment of vascularized cornea, amniotic membrane transplantation before PKP in cases of ulcerative keratitis, quality-controlled organ-cultured transplants, and preoperative counseling by the microsurgeon to ensure patient compliance. Intraoperative prophylaxis consists of controlled arterial hypotension and complete relaxation during general anesthesia and application of a Flieringa ring in aphakic vitrectomized eyes. Precautions for intraoperative prophylaxis of astigmatism must be followed. A measurable improvement seems to be possible using the technique of nonmechanical trephination of patient and donor from the epithelial side using the excimer laser but not the femtosecond laser. Graft size should be adjusted individually (“as large as possible, as small as necessary”). Limbal centration should be preferred over pupil centration (especially in keratoconus). In addition to the situation-specific diagnosis and preoperative planning, the critical selection of the donor tissue, and the minimally invasive microsurgical technique, it is especially the indication-dependent close-meshed follow-up which plays an important role in the long-term success of penetrating keratoplasty. In the follow-up process, the repeated emphatic sensitization of the patient to alarming subjective symptoms and the informed involvement of the ophthalmologist in private practice providing the follow-up treatment must be considered of crucial importance. “Treat them and street them” is certainly not the motto to follow!

Excimer versus Femtosecond Laser Assisted Penetrating Keratoplasty in Keratoconus and Fuchs Dystrophy: Intraoperative Pitfalls

Purpose. To assess the intraoperative results comparing two non-mechanical laser assisted penetrating keratoplasty approaches in keratoconus and Fuchs dystrophy. Patients and Methods. 68 patients (age 18 to 87 years) with keratoconus or Fuchs dystrophy were randomly distributed to 4 groups. 35 eyes with keratoconus and 33 eyes with Fuchs dystrophy were treated with either excimer laser ([Exc] groups I and II) or femtosecond laser-assisted ([FLAK] groups III and IV) penetrating keratoplasty. Main intraoperative outcome measures included intraoperative decentration, need for additional interrupted sutures, alignment of orientation markers, and intraocular positive pressure (vis a tergo). Results. Intraoperative recipient decentration occurred in 4 eyes of groups III/IV but in none of groups I/II. Additional interrupted sutures were not necessary in groups I/II but in 5 eyes of groups III/IV. Orientation markers were all aligned in groups I/II but were partly misaligned in 8 eyes of groups III/IV. Intraocular positive pressure grade was recognized in 12 eyes of groups I/II and in 19 eyes of groups III/IV. In particular, in group III, severe vis a tergo occurred in 8 eyes. Conclusions. Intraoperative decentration, misalignment of the donor in the recipient bed, and need for additional interrupted sutures as well as high percentage of severe intraocular positive pressure were predominantly present in the femtosecond laser in keratoconus eyes.

Asymmetry between Left and Right Eyes in Keratoconus Patients Increases with the Severity of the Worse Eye

ABSTRACT Purpose: To evaluate whether the inter-eye asymmetry of keratoconus (KC) patients is different from a healthy control group and to investigate how asymmetry changes with increasing severity of the disease. Methods: In this retrospective study, we included both eyes of 350 patients with KC (age 35 ± 13 years) and 68 candidates planned for refractive surgery (control group, age 37 ± 11 years). Inclusion criteria for the KC group were keratoconus in at least one eye with Pentacam Topographical Keratoconus Classification (TKC) of at least 0.5. Patients eligible for refractive surgery in both eyes were included in the control group. Corneal tomography as well as Ocular Response Analyzer measurements were compared between both groups. Subgroup analysis was performed with respect to the TKC staging. Asymmetry was provided as worse eye (defined by higher TKC) minus fellow eye. Results: In the KC group, both eyes showed the same TKC staging in 30.6%, a difference of one stage in 34.0% and of two stages in 24.6% of the patients. The inter-eye asymmetry in the keratoconus group was significantly larger than that in the control group. Corneal power showed an asymmetry of 3.8 ± 4.0 D in keratoconus eyes versus 0.22 ± 0.17 D in the control group. Central corneal thickness (CCT) asymmetry was 34 ± 30 µm versus 6 ± 5 µm, respectively. The Keratoconus Match Index showed an asymmetry of 0.40 ± 0.35 versus 0.15 ± 0.14. The difference between both eyes increased with increasing TKC of the worse eye. Conclusions: Inter-eye asymmetry is larger in keratoconus than in normal eyes, and it increases with keratoconus severity in the worse eye.

Complications and Management in Laser Transplant Surgery

Laser application without direct visual control of the operation area. Stop of power supply will stop procedure. Hyposphagma due to suction. Centration is difficult – especially in advanced keratoconus. Scars will impair incision, manual completion even with spatula or even scissors necessary. Difficult trephination and false lamellar cut depth in edematous corneas. Laser-Eye-Tracking system not feasible because of very high repetition rate and comparatively tiny focus. Not eye safe, because visible or near-IR laser must produce plasma via non-linear processes, otherwise potential deposition of laser energy on the retina. Deformation of the cornea during suction and applanation (recipient) resulting in not round (e.g., oval or pear shaped) and incongruent host incisions – FSL trephination not feasible for pathological curvatures of the cornea. Even after maximal suture adjustments, Placido disk application at the end of surgery will sometimes give you still elliptical or even irregular projections on the graft after FSL trephination in keratoconus – due to geometric mismatch. High and irregular astigmatism after suture removal – especially in advanced keratoconus. Problem of achieving the correct plane of the side cut in tophat or mushroom configurations, e.g., if an edematous donor has to prepared for a thinned keratoconus cornea. Often femtosecond laser is not placed in the sterile Operating Room. Therefore, either tissue bridges have to be intentionally left in place or even temporary interrupted sutures were placed after laser action to avoid expulsive hemorrhage during transportation from the laser suite to the operating room.

Effect of biometric characteristics on biomechanical properties of the cornea in cataract patient.

AIM To determine the impact of biometric characteristics on the biomechanical properties of the human cornea using the ocular response analyzer (ORA) and standard comprehensive ophthalmic examinations before and after standard phacoemulsification. METHODS This study comprised 54 eyes with cataract with significant lens opacification in stages I or II that underwent phacoemulsification (2.8 mm incision). Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated intraocular pressure (IOPcc) were measured by ORA preoperatively and at 1mo postoperatively. Biometric characteristics were derived from corneal topography [TMS-5, anterior equivalent (EQTMS) and cylindric (CYLTMS) power], corneal tomography [Casia, anterior and posterior equivalent (EQaCASIC, EQpCASIA) and cylindric (CYLaCASIA, CYLpCASIA) power], keratometry [IOLMaster, anterior equivalent (EQIOL) and cylindric (CYLIOL) power] and autorefractor [anterior equivalent (EQAR)]. Results from ORA were analyzed and correlated with those from all other examinations taken at the same time point. RESULTS Preoperatively, CH correlated with EQpCASIA and CYLpCASIA only (P=0.001, P=0.002). Postoperatively, IOPg and IOPcc correlated with all equivalent powers (EQTMS, EQIOL, EQAR, EQaCASIA and EQpCASIA) (P=0.001, P=0.007, P=0.001, P=0.015, P=0.03 for IOPg and P<0.001, P=0.003, P<0.001, P=0.009, P=0.014 for IOPcc). CH correlated postoperatively with EQaCASIA and EQpCASIC only (P=0.021, P=0.022). CONCLUSION Biometric characteristics may significantly affect biomechanical properties of the cornea in terms of CH, IOPcc and IOPg before, but even more after cataract surgery.