Detection of SARS-CoV-2-RNA in post-mortem samples of human eyes.

PURPOSE: To detect SARS-CoV-2 RNA in post-mortem human eyes. Ocular symptoms are common in patients with COVID-19. In some cases, they can occur before the onset of respiratory and other symptoms. Accordingly, SARS-CoV-2 RNA has been detected in conjunctival samples and tear film of patients suffering from COVID-19. However, the detection and clinical relevance of intravitreal SARS-CoV-2 RNA still remain unclear due to so far contradictory reports in the literature. METHODS: In our study 20 patients with confirmed diagnosis of COVID-19 were evaluated post-mortem to assess the conjunctival and intraocular presence of SARS-CoV-2 RNA using sterile pulmonary and conjunctival swabs as well as intravitreal biopsies (IVB) via needle puncture. SARS-CoV-2 PCR and whole genome sequencing from the samples of the deceased patients were performed. Medical history and comorbidities of all subjects were recorded and analyzed for correlations with viral data. RESULTS: SARS-CoV-2 RNA was detected in 10 conjunctival (50%) and 6 vitreal (30%) samples. SARS-CoV-2 whole genome sequencing showed the distribution of cases largely reflecting the frequency of circulating lineages in the Munich area at the time of examination with no preponderance of specific variants. Especially there was no association between the presence of SARS-CoV-2 RNA in IVBs and infection with the variant of concern (VOC) alpha. Viral load in bronchial samples correlated positively with load in conjunctiva but not the vitreous. CONCLUSION: SARS-CoV-2 RNA can be detected post mortem in conjunctival tissues and IVBs. This is relevant to the planning of ophthalmologic surgical procedures in COVID-19 patients, such as pars plana vitrectomy or corneal transplantation. Furthermore, not only during surgery but also in an outpatient setting it is important to emphasize the need for personal protection in order to avoid infection and spreading of SARS-CoV-2. Prospective studies are needed, especially to determine the clinical relevance of conjunctival and intravitreal SARS-CoV-2 detection concerning intraocular affection in active COVID-19 state and in post-COVID syndrome.

Functional recovery after macula involving retinal detachment and its correlation with preoperative biomarkers in optical coherence tomography.

To introduce an ETDRS grid-based classification for macula involving retinal detachment (MIRD) with or without center (foveal) involvement and to identify biomarkers in preoperative optical coherence tomography (OCT) associated with a favorable postoperative functional outcome in eyes with center involving retinal detachment (CIRD). One hundred and two eyes of 102 consecutive patients (f/m: 35/67) with primary rhegmatogenous retinal detachment, preoperative evidence of MIRD (perifoveal involvement of ≤ 6.0 mm), and successful retinal surgery were included in this retrospective cohort study. Eyes were assigned to 5 grades of MIRD (G1-G5), based on the extent of detachment in the ETDRS grid. Eyes with a detached foveal status (CIRD) were assigned to G4 or G5. In CIRD, the following OCT biomarkers were quantified and correlated with mean BCVA (logMAR) at 3 months postsurgery, using univariate and multivariable regression models: grade of detachment, extent of intraretinal edema, height of foveal detachment, subretinal folds, and epiretinal membrane. Forty-one of 102 eyes (40.2%) presented with an attached foveal status, defined as either outer (G1: 11.8%) or inner (G2: 18.6%) macular involvement or fovea-threatening MIRD (G3: 9.8%). Sixty-one eyes (59.8%) showed CIRD (G4 or G5). Eyes with CIRD had significantly worse postoperative BCVA than eyes without foveal involvement (0.355 logMAR vs. 0.138 logMAR, p<0.001). If CIRD was limited to three outer ETDRS quadrants (G4), mean BCVA was better compared to CIRD involving all four ETDRS quadrants (G5) (0.254 logMAR vs. 0.522 logMAR, p<0.001). Reading ability (BCVA ≤ 0.4 logMAR) was restored in 97.6% of eyes with G1-G3 compared to 86.9% of eyes with G4 (p=0.072) and 52.4% of eyes with G5 (p<0.001). In multivariable regression analysis of eyes with CIRD, a lower grade of detachment (G4 vs. G5: p<0.05) and lower extent of cystoid edema (focal/none vs. wide: p<0.001) were both associated with better postoperative function. The functional outcome after MIRD may be worse in the presence of foveal involvement (CIRD), but a lower grade of detachment and the absence of intraretinal edema can predict a good recovery in spite of CIRD.

FUNCTIONAL AND MORPHOLOGICAL OUTCOMES OF THE INVERTED INTERNAL LIMITING MEMBRANE FLAP TECHNIQUE IN SMALL-SIZED AND MEDIUM-SIZED MACULAR HOLES <400 µm.

PURPOSE: To assess the effect of an internal limiting membrane flap (IF) in macular hole surgery on the best-corrected visual acuity (BCVA) and integrity of the ellipsoid zone (EZ) and external limiting membrane. METHODS: Patients were included who had successful surgery for macular hole <400 µm with or without an IF. Main outcome measures were BCVA and restoration of the external limiting membrane and EZ at 12 months. RESULTS: Sixty patients were included, 36 with conventional peeling and 24 with an IF. The best-corrected visual acuity improved from 0.74 (±0.30) logarithm of the minimum angle of resolution (20/110 Snellen) to 0.26 (±0.20) (20/36 Snellen) in patients without and from 0.77 (±0.32) logarithm of the minimum angle of resolution (20/118 Snellen) to 0.18 (±0.12) (20/30 Snellen) in patients with an IF, respectively. There was no difference in the integrity of the EZ and external limiting membrane in patients with or without an IF at either 3 (P = 0.58, P = 0.20), 6 (P = 0.81, P = 0.10), or 12 months (P = 0.60, P = 0.20) or in the BCVA at 3 (P = 0.24), 6 (P = 0.18) and 12 months (P = 0.11). In the multivariable model, only preoperative BCVA (P < 0.01), EZ integrity (P = 0.001), and age (P < 0.01) were associated with the post-operative BCVA. CONCLUSION: In patients undergoing surgery for macular hole <400 µm, the use of an IF did not affect the BCVA or the integrity of the EZ and external limiting membrane.

Corneal crosslinking (CXL) with 18-mW/cm2 irradiance and 5.4-J/cm2 radiant exposure-early postoperative safety.

PURPOSE: To investigate safety of accelerated corneal crosslinking during the first postoperative month. METHODS: In this retrospective study, 76 eyes of 60 patients with verified progressive keratectasia were enrolled in this study and followed for 1 month after accelerated CXL (18 mW/cm2 for 5 min, radiant exposure 5.4 J/cm2) (A-CXL(5*18)). Preoperatively, objective refraction, slit lamp inspection, and corneal tomography were performed. Early postoperative slit lamp examinations were performed on days 1 and 4. At 1 month, objective refraction, slit lamp inspection, and corneal tomography were performed. RESULTS: Gender distribution was m:f = 55:21, OD:OS was 40:36, and the average age was 26.5 ± 8.6 years at surgery. Only 71 of the 76 eyes completed the 1-month follow-up, indicating a dropout rate of 6.6%. In 7.0% (n = 5), sterile infiltrates were observed; 5.6% of eyes (n = 4) showed delayed epithelial healing (> 4 days) in 2.8% (n = 2); an infection occurred and in 1 eye (1.4%), a stromal scar was detected; no other complications, neither a loss of two or more Snellen lines at 1 month postoperatively, were observed. As a risk factor for sterile infiltrates, thin preoperative pachymetry could be identified (p = 0.027). CONCLUSIONS: This study revealed no difference in early postoperative safety between CXL using 18 mW/cm2 and standard corneal CXL. Thinner preoperative pachymetry could be identified predicting a higher rate of postoperative sterile infiltrates.

[Retinal Vascular Occlusion: Modern Therapeutic Approaches]. / Retinale Gefäßverschlüsse: Moderne Therapieansätze.

Retinal artery occlusion (RAO) should be evaluated as an emergency and can be seen as an ocular analogue to the cerebral apoplex. Both have the same arteriosclerotic risk factors, which are also responsible for cardiac, circulatory and cerebrovascular diseases. That is why an intensive interdisciplinary clarification is necessary to recognize possible comorbidities in time and, if necessary, to treat them. The current therapeutic possibilities of an acute RAO are very limited in their efficiency regarding visual improvement. Methods for systemic lysis cannot be recommended in routine care because of their significantly increased side-effect profile. However, there is a limited window of time of up to 6 hours after the onset of symptoms in which an intervention appears to be useful at all. On the other hand, the new therapeutic possibilities of retinal vein occlusions (RVO) led to marked visual improvements, especially due to the intravitreal application of anti-VEGF. Safety and efficiency of the individual anti-VEGF drugs are comparable according to clinical trials. Alternatively, the use of intravitreal steroids can be considered, whereby the side-effect profile should be carefully weighed. In the presence of retinal ischaemia, peripheral laser coagulation can have a stabilizing effect on visual acuity and prevents neovascularization. It is postulated that the combination of anti-VEGF and laser therapy might have a symbiotic effect.

[Intraoperative Optical Coherence Tomography in Vitreoretinal Surgery: Clinical Experiences and Future Developments]. / Die intraoperative optische Kohärenztomografie in der Netzhaut-Glaskörper-Chirurgie. Aktuelle Erfahrungen und Ausblick auf künftige Entwicklungsschritte.

PURPOSE: High resolution optical coherence tomography (OCT) enables better visualization of ophthalmic microstructures than conventional imaging. When using an ophthalmic microscope, integrated optical coherence tomography (iOCT) high resolution real time visualization is possible. METHODS: We report on the first 110 patients operated on using a microscope integrated OCT (iOCT) during surgical procedures for the treatment of various posterior segment pathologies. RESULTS: Microstructural changes that appeared during surgery were depicted precisely by iOCT, and the morphology visualized before and after each surgical step was used to help deciding how to adapt the surgical flow. The iOCT data and real-time imaging of retinal anatomy gives the surgeon the possibility of deploying patient- and operation-specific interventional procedures. DISCUSSION: To date, iOCT is only available in standing microscopes with no measurement or tracking features. Moreover, metal instruments currently obscure the scanned images. In the future, non-metal, transparent instruments (OCT-friendly surgical tools), tracking features, an autofocus and higher resolution could enable full and immediate intraoperative SD-OCT diagnostics in real time.

Microstructural morphology and visual acuity outcome in eyes with epiretinal membrane before, during, and after membrane peeling in intraoperative optical coherence tomography assisted macular surgery.

AIM: To measure the difference of intraoperative central macular thickness (CMT) before, during, and after membrane peeling and investigate the influence of intraoperative macular stretching on postoperative best corrected visual acuity (BCVA) outcome and postoperative CMT development. METHODS: A total of 59 eyes of 59 patients who underwent vitreoretinal surgery for epiretinal membrane was analyzed. Videos with intraoperative optical coherence tomography (OCT) were recorded. Difference of intraoperative CMT before, during, and after peeling was measured. Pre- and postoperatively obtained BCVA and spectral-domain OCT images were analyzed. RESULTS: Mean age of the patients was 70±8.13y (range 46-86y). Mean baseline BCVA was 0.49±0.27 logMAR (range 0.1-1.3). Three and six months postoperatively the mean BCVA was 0.36±0.25 (P=0.01 vs baseline) and 0.38±0.35 (P=0.08 vs baseline) logMAR respectively. Mean stretch of the macula during surgery was 29% from baseline (range 2%-159%). Intraoperative findings of macular stretching did not correlate with visual acuity outcome within 6mo after surgery (r=-0.06, P=0.72). However, extent of macular stretching during surgery significantly correlated with less reduction of CMT at the fovea centralis (r=-0.43, P<0.01) and 1 mm nasal and temporal from the fovea (r=-0.37, P=0.02 and r=-0.50, P<0.01 respectively) 3mo postoperatively. CONCLUSION: The extent of retinal stretching during membrane peeling may predict the development of postoperative central retinal thickness, though there is no correlation with visual acuity development within the first 6mo postoperatively.

iOCT-guided simulated subretinal injections: a comparison between manual and robot-assisted techniques in an ex-vivo porcine model.

The purpose of this study is to compare robot-assisted and manual subretinal injections in terms of successful subretinal blistering, reflux incidences and damage of the retinal pigment epithelium (RPE). Subretinal injection was simulated on 84 ex-vivo porcine eyes with half of the interventions being carried out manually and the other half by controlling a custom-built robot in a master-slave fashion. After pars plana vitrectomy (PPV), the retinal target spot was determined under a LUMERA 700 microscope with microscope-integrated intraoperative optical coherence tomography (iOCT) RESCAN 700 (Carl Zeiss Meditec, Germany). For injection, a 1 ml syringe filled with perfluorocarbon liquid (PFCL) was tipped with a 40-gauge metal cannula (Incyto Co., Ltd., South Korea). In one set of trials, the needle was attached to the robot's end joint and maneuvered robotically to the retinal target site. In another set of trials, approaching the retina was performed manually. Intraretinal cannula-tip depth was monitored continuously via iOCT. At sufficient depth, PFCL was injected into the subretinal space. iOCT images and fundus video recordings were used to evaluate the surgical outcome. Robotic injections showed more often successful subretinal blistering (73.7% vs. 61.8%, p > 0.05) and a significantly lower incidence of reflux (23.7% vs. 58.8%, p < 0.01). Although larger tip depths were achieved in successful manual trials, RPE penetration occurred in 10.5% of robotic but in 26.5% of manual cases (p > 0.05). In conclusion, significantly less reflux incidences were achieved with the use of a robot. Furthermore, RPE penetrations occurred less and successful blistering more frequently when performing robotic surgery.

Defining a Cutoff for Progression of Macular Holes.

Purpose: The purpose of this study was to determine a cutoff for progression of idiopathic full-thickness macular hole (MH) size. Methods: Retrospective analysis of consecutive patients waiting 4 weeks for MH surgery. Two observers performed 3 repeat sets of MH size measurements on optical coherence tomography (OCT) high-density radial scans taken at first presentation and 4 weeks later before surgery. Primary outcome was the definition of a cutoff for true enlargement of MH size versus measurement error. Secondary outcomes were risk factors for change in minimum linear diameter (MLD) size and best-corrected visual acuity (BCVA). Results: Fifty-one patients were included with a mean MH size of 334 µm (±179 µm; range 39 to 793 µm). The cutoff for an increase in MLD size calculated as the outer confidence limit for the 99.73% limits of agreement was 31 µm. This was independent of MH size. Using this cutoff, MLD size increased in 9/34 (26.5%) of patients without and in 14 of 17 (82.4%) of patients with vitreomacular traction (VMT; P < 0.001). Mean BCVA deteriorated in patients in whom the MH had progressed from 0.62 (±0.23) logMAR to 0.82 (±0.29; P < 0.001), whereas there was no significant change in BCVA in patients without MH progression (P = 0.25). In 31% (16/51) of patients, classification of their MHs (small ≤250 µm, medium 251-400 µm, and large >400 µm) changed over the 4-week period. Conclusions: Using a cutoff discriminates change from measurement error. A significant proportion of MHs progressed by 4 weeks, particularly in the presence of VMT. Translational Relevance: The established cutoff enables clinicians to differentiate true MH enlargement from measurement error.

Repeatability and Reproducibility of Macular Hole Size Measurements Using Optical Coherence Tomography.

The purpose of this study was to assess the repeatability and reproducibility of measuring the minimum linear diameter (MLD) of macular holes (MHs) using horizontal linear and radial scan modes in optical coherence tomography (OCT). Patients with concurrent sets of radial and horizontal linear OCT volume scans were included. The MLD was measured twice in both scan modes by six raters of three different experience levels (groups). Outcome measures were the reliability and repeatability of MLD measurements. Fifty patients were included. Mean MLD was 317.21(±170.63) µm in horizontal linear and 364.52 (±161.71) µm in radial mode, a difference of 47.31 (±26.48) µm (p < 0.001). In the radial scan mode, MLD was identified within 15° of the horizontal meridian in 27% and within 15° of the vertical meridian in 26.7%, with the remainder (46.3%) in oblique meridians. The intra-group coefficients of repeatability (CR) for horizontal linear mode were 23 µm, 33 µm and 45 µm, and for radial mode 25 µm, 44 µm and 57 µm for groups 1, 2 and 3, respectively. The inter-group CR, taking group 1 as reference standard for groups 2 and 3, were 74 µm and 71 µm for the linear mode, and 62 µm and 78 µm for radial mode. The radial mode provides good repeatability and reliability for measurement of MLD. In a majority of cases the MLD does not lie in the horizontal meridian and would be underestimated using a horizontal OCT mode.

Predictive Association of Pre-Operative Defect Areas in the Outer Retinal Layers With Visual Acuity in Macular Hole Surgery.

Purpose: The purpose of this study was to develop methods to model the external limiting membrane (ELM) and ellipsoid zone (EZ) within the elevated cuff surrounding a macular hole (MH) to determine if the predicted size of the defect in these layers after virtual flattening was associated with the actual postoperative defect and best-corrected visual acuity (BCVA). Methods: Patients were included who had undergone successful MH surgery. The defects in the ELM and EZ after virtual flattening were modeled using in-house software. Main outcomes were postoperative defects in ELM and EZ at 2 months and BCVA at 12 months. Results: Fifty-eight patients were included. BCVA improved from 0.87 (0.31) logMAR pre-operatively to 0.26 (0.21) at 12 months (P < 0.001). For both the ELM and EZ, the predicted virtually flattened pre-operative defects were associated with the actual postoperative defects at 2 months (R2 = 0.33, P < 0.01 and R2 = 0.50, P < 0.01, respectively). There was a significant association of BCVA at 12 months (adjusted R2 = 0.85) with the pre-operative modeled area of the defect in the ELM (P < 0.01) and to a lesser extent with the defect in the EZ (P < 0.01) and base of the MH (P < 0.01). Conclusions: Virtually flattening of the pre-operative defect in the ELM provides important predictive information of visual acuity. Incorporation of tools into commercially available optical coherence tomography (OCT) devices to facilitate such measurements would provide the clinician with important prognostic information. Translational Relevance: We have developed methodology that can potentially be used to predict the postoperative state of the outer retinal layers and the associated visual outcome in patients undergoing surgery for MH.

Clinical results with the light adjustable intraocular lens after cataract surgery.

PURPOSE: The accuracy of intraocular lens (IOL) calculation is limited by the variation of the measurement of corneal power, axial length, anterior chamber depth, and effective postoperative lens position. Therefore, IOL predictability is limited. The aim of this study was to evaluate the performance of the novel light adjustable lens (LAL, Calhoun Vision). METHODS: Ten eyes with cataracts (seven patients) were included. After standard phacoemulsification, the LAL was implanted. Two to 3 weeks after surgery, all IOL adjustments had been completed. Preoperatively, pre-adjustment, pre-lock-in, and 1 month post-lock-in, a full ophthalmic examination including objective (autorefraction) and subjective refraction (ie, manifest uncorrected visual acuity [UCVA] and manifest best spectacle-corrected visual acuity [BSCVA]) and topography were performed. RESULTS: All cataract surgeries were performed with no complications. Two weeks after surgery, the mean refraction was +0.78+/-0.79 diopters (D). After adjustment and lock-in, the refraction was -0.07+/-0.21 D. In 4 of 10 eyes, second adjustments were necessary. One month after surgery, all patients were within +/-0.50 D of the intended refraction. Preoperatively, the cylinder was 0.88+/-0.77 D, but was reduced after adjustments to 0.15+/-0.20 D. Mean UCVA was 1.02, and all eyes gained at least two lines on the Snellen visual acuity test (ie, BSCVA) after surgery. CONCLUSIONS: The LAL is a new IOL with the ability to correct up to 2.00 D of sphere and cylinder after implantation. Our first clinical results are promising and indicate effective safety and stability.

EpiLASIK with mitomycin C.

PURPOSE: Mitomycin C after photorefractive keratectomy (PRK) is used to reduce the development of haze and regression in higher intended corrections. The aim of this study was to investigate the safety, stability, and efficacy of EpiLASIK with mitomycin C. METHODS: Fifty eyes of 29 patients underwent EpiLASIK with the Gebauer EpiLift microkeratome. The mean preoperative spherical equivalent was -6.89 D (SD +/-0.63, range -6.0 to -8.0 D). After the laser ablation, mitomycin C 0.02% was applied for 30 seconds on a sterile filter paper. Preoperatively and 1, 3, 6, and 12 months after surgery, a full ophthalmic examination was performed. RESULTS: In 42 of 50 eyes, the bandage contact lens was removed at day 3. Twelve months after surgery, 96% of all eyes were within +/-1.0 D and 82% were within +/-0.5 D of intended correction. Five percent of all patients lost 1 line of best-corrected Snellen visual acuity, 42% were stable, and 56% gained 1 or more lines. In most patients, the cornea was clear during the whole follow-up, and in 10% only trace haze was visible. The uncorrected visual acuity was at least 1.0 in 86% of all patients, and all patients reached 0.5. CONCLUSIONS: EpiLASIK with mitomycin C with higher intended corrections seems to be an effective and safe procedure. With the application of mitomycin C, only minimal haze appears.

Machine Learning Techniques for Ophthalmic Data Processing: A Review.

Machine learning and especially deep learning techniques are dominating medical image and data analysis. This article reviews machine learning approaches proposed for diagnosing ophthalmic diseases during the last four years. Three diseases are addressed in this survey, namely diabetic retinopathy, age-related macular degeneration, and glaucoma. The review covers over 60 publications and 25 public datasets and challenges related to the detection, grading, and lesion segmentation of the three considered diseases. Each section provides a summary of the public datasets and challenges related to each pathology and the current methods that have been applied to the problem. Furthermore, the recent machine learning approaches used for retinal vessels segmentation, and methods of retinal layers and fluid segmentation are reviewed. Two main imaging modalities are considered in this survey, namely color fundus imaging, and optical coherence tomography. Machine learning approaches that use eye measurements and visual field data for glaucoma detection are also included in the survey. Finally, the authors provide their views, expectations and the limitations of the future of these techniques in the clinical practice.

Reducing the Number of Degrees of Freedom to Control an Eye Surgical Robot through Classification of Surgical Phases.

This paper introduces an optimized input device workflow to control an eye surgical robot in a simulated vitreoretinal environment. The input device is a joystick with four Degrees of Freedom (DOF) that controls a six DOFs robot. This aim is achieved through a segmentation plan for an eye surgeon. In this study, the different surgical phases are defined while each phase includes their specific number of DOFs. The segmentation plan is divided into four surgical phases: Phase I: Approach with three DOFs; Phase II: Introduction with three DOFs; Phase III: Aim with 3+1 DOFs; and Phase IV: Injection with one DOF. Taking these phases into consideration, an eye surgical robot with six DOFs could be controlled through a joystick with only four DOFs intuitively. In this work we show that reducing the number of DOFs will decrease the complexity of the surgery with a robotic platform.

Choriocapillaris Flow Density Negatively Correlates With Advancing Age on Spectral-Domain Optical Coherence Tomography Angiography.

BACKGROUND AND OBJECTIVE: To correlate subfoveal choriocapillaris (CC) flow density with age using spectral-domain optical coherence tomography angiography (SD-OCTA). PATIENTS AND METHODS: One hundred eighty-three eyes of 94 subjects (66 female, 28 male) were enrolled. Included were healthy subjects between the ages of 21 and 82 years without any history of vitreoretinal disease. Measurements were obtained with software from the OCT device. Significance was defined as a P value of less than .05. RESULTS: The mean age was 43.43 years ± 17.63 years. Correlation between decreasing CC flow density and increasing age was significant (P < .001), with a mean yearly flow decrease of 0.026%. Subfoveal choroidal thickness decreased with advancing age; however, this did not reach a level of significance (P = .069). CONCLUSION: There is a significantly negative correlation between CC flow density and advancing age in healthy subjects, analyzing direct extracted in-built software values from a commercial SD-OCTA device. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:302-308.].

Choriocapillary Blood Flow in Myopic Subjects Measured With OCT Angiography.

BACKGROUND AND OBJECTIVE: To investigate choriocapillary blood flow in myopic eyes using optical coherence tomography angiography. PATIENTS AND METHODS: Seventy-eight myopic and 79 age-matched healthy eyes were included in this study, with myopia defined as a spherical equivalent refraction (SER) between -1 diopters (D) and -6 D. Quantitative measurements of the choriocapillaris were obtained using the Avanti RTVue XR with AngioVue. Choroidal thickness (CT) was assessed using the single-line enhanced high-definition scan of the same device. RESULTS: CT correlated positively with SER (P = .017) and negatively with bulbus axial length (AL) (P = .180). Subfoveal choriocapillary blood flow did not show any significant correlation with any of the parameters SER, AL, or CT (P = .798, P = .269, and P = .820, respectively). The mean flow signal of the myopic group did not differ significantly from the mean flow signal of the emmetropic control group (P = .266). CONCLUSION: Choriocapillary blood flow seems to retain a constant level with increasing physiological myopia. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:e133-e139.].

Multiphoton-mediated corneal flap generation using the 80 MHz nanojoule femtosecond near-infrared laser.

PURPOSE: To evaluate whether corneal flaps can be generated by the 80 MHz near-infrared, intense nanojoule femtosecond laser based on multiphoton absorption. METHODS: A solid-state Ti:Sapphire femtosecond laser system was integrated in an inverted JenLab Femt-O-Cut laser scanning microscope. A diffraction-limited 40x objective was used to induce multiphoton ionization and plasma production. New Zealand albino rabbits and porcine eyes were used. Surgical outcomes were determined using frame and line scans with nanojoule pulses at a wavelength of 800 nm. RESULTS: Surgical performance was assessed by optical imaging, histology, and electron microscopy. No significant corneal turbidity was observed. Optical imaging and histological examinations detected virtually no perturbation in the surrounding tissue. Corneal flaps and stromal lenticules were generated. Wound repair of the unlifted flaps was observed up to 90 days postoperatively. CONCLUSIONS: Surgical results and follow-up studies confirm that this femtosecond laser at nanojoule pulse energy is able to generate corneal flaps precisely, without causing visible collateral damage to the surrounding tissue or overlying epithelium.

Epi-laser in situ keratomileusis: comparative evaluation of epithelial separation with 3 microkeratomes.

PURPOSE: To evaluate the cleavage plane, corneal cytoarchitecture, and cell vitality of separated corneal epithelial sheets created with 3 commonly used microkeratomes. SETTING: Laboratories of the Regensburg University Medical Center, Regensburg, Germany. METHODS: Mechanical separation of the epithelial layer in 10 porcine eyes and 2 human eyes was performed with 3 different microkeratomes (Amadeus II, Zyoptix XP, Epivision). Five of 10 porcine corneas and the 2 human corneas treated with each microkeratome were processed for histology, electron microscopy, and immunohistochemistry. In 5 of 10 porcine corneas, the corneal epithelial sheets were separated from the globe and cell vitality was assessed with the trypan blue dye vitality test. RESULTS: A reproducible epithelial separation with a smooth surface was achieved in all eyes. The cleavage plane was located between the lamina lucida and the lamina densa. Damage to epithelial cells was mainly limited to the cut margins. CONCLUSIONS: Mechanical separation of the epithelial sheet in epithelial laser in situ keratomileusis (epi-LASIK) was safe and reproducible with all evaluated microkeratomes. Immunohistochemistry and electron microscopy showed the cleavage plane in epi-LASIK was between the basal epithelium and the basement membrane at the level of the lamina lucida.

Multimodal imaging in acute retinal ischemia: spectral domain OCT, OCT-angiography and fundus autofluorescence.

AIM: To describe retinal findings of various imaging modalities in acute retinal ischemia. METHODS: Fluorescein angiography (FA), spectral domain optical coherence tomography (SD-OCT), OCT-angiography (OCT-A) and fundus autofluorescence (FAF) images of 13 patients (mean age 64y, range 28-86y) with acute retinal ischemia were evaluated. Six suffered from branch arterial occlusion, 2 had a central retinal artery occlusion, 2 had a combined arteriovenous occlusions, 1 patient had a retrobulbar arterial compression by an orbital haemangioma and 2 patients showed an ocular ischemic syndrome. RESULTS: All patients showed increased reflectivity and thickening of the ischemic retinal tissue. In 10 out of 13 patients SD-OCT revealed an additional highly reflective band located within or above the outer plexiform layer. Morphological characteristics were a decreasing intensity with distance from the fovea, partially segmental occurrence and manifestation limited in time. OCT-A showed a loss of flow signal in the superficial and deep capillary plexus at the affected areas. Reduced flow signal was detected underneath the regions with retinal edema. FAF showed areas of altered signal intensity at the posterior pole. The regions of decreased FAF signal corresponded to peri-venous regions. CONCLUSION: Multimodal imaging modalities in retinal ischemia yield characteristic findings and valuable diagnostic information. Conventional OCT identifies hyperreflectivity and thickening and a mid-retinal hyperreflective band is frequently observed. OCT-A examination reveals demarcation of the ischemic retinal area on the vascular level. FAF shows decreased fluorescence signal in areas of retinal edema often corresponding to peri-venous regions.