Outcomes of Scleral Buckling After Failed Pneumatic Retinopexy

Purpose: To assess the visual and anatomic outcomes of eyes that had secondary scleral buckle (SB) surgery after unsuccessful pneumatic retinopexy (PR) for rhegmatogenous retinal detachment (RRD). Methods: A retrospective study, performed over a 12-year period, comprised patients who had secondary SB procedures after failed primary PR. Clinical parameters (eg, best-corrected visual acuity [BCVA], lens status, macula status, details of RRD and subretinal fluid) were assessed at presentation, before additional procedures, and at follow-up (6 months, 1 year, and last visit). Statistical comparisons were made using Brown-Forsythe and Welch analysis-of-variance tests, with significance levels set at P < .05. Results: Fifty-four eyes with adequate follow-up were included. Forty-four (81.5%) of 54 eyes had successful retinal reattachment with secondary SB alone. The remaining eyes had subsequent pars plana vitrectomy (PPV). Patients presenting with macula-on RRD who had successful secondary SB had no statistically significant change in BCVA from baseline (mean final, 0.23 ± 0.25 logMAR [Snellen 20/34]; P = .999). There was a statistically significant improvement in BCVA in patients presenting with macula-off RRD who had successful secondary SB (mean final, 0.32 ± 0.36 logMAR [20/42]; P < .001 and mean change, -1.06 ± 0.85 logMAR). Ten patients presenting with macula-off RRD who had failed secondary SB had a significant improvement in the final BCVA (mean final, 0.22 ± 0.28 logMAR [20/33]; P = .044), despite the need for an additional PPV to achieve reattachment. Conclusions: Secondary SB remains a good option for RRD repair after unsuccessful PR and may avoid the need for PPV.

Challenges in Diagnosing Extruded Hydrogel Scleral Buckle Mimicking an Orbital Abscess: A Case Report

In this case report, we present an unusual complication linked to a hydrogel explant in a 72-year-old male presenting to the emergency department with persistent left eye pain, redness, and discharge for one month. The patient had a history of retinal detachment in 1989, which was managed with scleral buckle surgery and gas injection. Initial examination revealed an extruding scleral buckle in the superior temporal region, along with signs of an infection. CT scans revealed a 1.9 × 1.2 × 3.8 cm abscess accompanied by preseptal cellulitis. This case report highlights the importance of how hydrogel scleral buckle explants may mimic the presentation and symptoms of an abscess as a long-term complication. Nevertheless, there have been several reports of long-term issues associated with the expansion of the hydrophilic hydrogel material. This case report further illustrates how complications linked to hydrogel explants can resemble abscess symptoms, underscoring the significance of accurate diagnosis and appropriate management.

Forward Light Scattering of First to Third Generation Vitreous Body Replacement Hydrogels after Surgical Application Compared to Conventional Silicone Oils and Vitreous Body

To treat certain vitreoretinal diseases, the vitreous body, a hydrogel composed of mostly collagen and hyaluronic acid, must be removed. After vitrectomy surgery, the vitreous cavity is filled with an endotamponade. Previously, pre-clinical hydrogel-based vitreous body substitutes either made from uncrosslinked monomers (1st generation), preformed crosslinked polymers (2nd generation), or in situ gelating polymers (3rd generation) have been developed. Forward light scattering is a measure of Stray light induced by optical media, when increased, causing visual disturbance and glare. During pinhole surgery, the hydrogels are injected into the vitreous cavity through a small 23G-cannula. The aim of this study was to assess if and to what extent forward light scattering is induced by vitreous body replacement hydrogels and if Stray light differs between different generations of vitreous body hydrogel replacements due to the different gelation mechanisms and fragmentation during injection. A modified C-Quant setup was used to objectively determine forward light scattering. In this study, we found that the 1st and 3rd generation vitreous body replacements show very low stray light levels even after injection (2.8 +/- 0.4 deg2/sr and 0.2 +/- 0.2 deg2/sr, respectively) as gel fragmentation and generation of interfaces is circumvented. The 2nd generation preformed hydrogels showed a permanent increase in stray light after injection that will most likely lead to symptoms such as glare when used in patients (11.9 +/- 0.9 deg2/sr). Stray light of the 2nd generation hydrogels was 3- and 2-fold increased compared to juvenile and aged vitreous bodies, respectively. In conclusion, this significant downside in the forward light scattering of the 2nd generation hydrogels should be kept in mind when developing vitreous body replacement strategies, as any source of stray light should be minimized in patients with retinal comorbidities.

Theoretical error analysis of spotlight-based instrument localization for retinal surgery

Retinal surgery is widely considered to be a complicated and challenging task even for specialists. Image-guided robot-assisted intervention is among the novel and promising solutions that may enhance human capabilities therein. In this paper, we demonstrate the possibility of using spotlights for 5D guidance of a microsurgical instrument. The theoretical basis of the localization for the instrument based on the projection of a single spotlight is analyzed to deduce the position and orientation of the spotlight source. The usage of multiple spotlights is also proposed to check the possibility of further improvements for the performance boundaries. The proposed method is verified within a high-fidelity simulation environment using the 3D creation suite Blender. Experimental results show that the average positioning error is 0.029 mm using a single spotlight and 0.025 mm with three spotlights, respectively, while the rotational errors are 0.124 and 0.101, which shows the application to be promising in instrument localization for retinal surgery.

INTRACTABLE PAIN AND DIPLOPIA AFTER SCLERAL BUCKLE SURGERY

PURPOSE

To report a case of early postoperative scleral buckle slippage because of the dehiscence of scleral belt loop tunnels.

METHOD

Case report.

RESULTS

A 54-year-old woman presented with painful diplopia after a combination pars plana vitrectomy and scleral buckling procedure. Ocular movements were limited. Forced duction testing was restricted in all directions. Anterior slippage of the silicone band was suggested on computed tomography (CT) scans and was confirmed with surgical exploration. During surgery, it was found that thin-roofed scleral belt loop tunnels were dehisced in three quadrants leading to anterior slippage of the buckle. The displaced buckle was removed. Diplopia and pain resolved, and ocular motility improved immediately afterward. The retina remained attached at six months follow-up. A supplemental video summarizes the surgical findings and postoperative results.

CONCLUSION

Spontaneous dehiscence of scleral belt loops may occur in thinly dissected scleral tunnels. Painful eye movement, diplopia, and a positive forced duction test should raise suspicion about a displaced scleral buckle. A CT scan may help with the diagnosis. Early diagnosis and immediate surgical intervention are needed to minimize patient discomfort and to improve long-term ocular motility.

Force-based Control for Safe Robot-assisted Retinal Interventions: In Vivo Evaluation in Animal Studies

In recent years, robotic assistance in vitreoretinal surgery has moved from a benchtop environment to the operating rooms. Emerging robotic systems improve tool manoeuvrability and provide precise tool motions in a constrained intraocular environment and reduce/remove hand tremor. However, often due to their stiff and bulky mechanical structure, they diminish the perception of tool-to-sclera (scleral) forces, on which the surgeon relies, for eyeball manipulation. In this paper we measure these scleral forces and actively control the robot to keep them under a predefined threshold. Scleral forces are measured using a Fiber Bragg Grating (FBG) based force sensing instrument in an in vivo rabbit eye model in manual, cooperative robotic assistance with no scleral force control (NC), adaptive scleral force norm control (ANC) and adaptive scleral force component control (ACC) methods. To the best of our knowledge, this is the first time that the scleral forces are measured in an in vivo eye model during robot assisted vitreoretinal procedures. An experienced retinal surgeon repeated an intraocular tool manipulation (ITM) task 10 times in four in vivo rabbit eyes and a phantom eyeball, for a total of 50 repetitions in each control mode. Statistical analysis shows that the ANC and ACC control schemes restrict the duration of the undesired scleral forces to 4.41% and 14.53% as compared to 43.30% and 35.28% in manual and NC cases, respectively during the in vivo studies. These results show that the active robot control schemes can maintain applied scleral forces below a desired threshold during robot-assisted vitreoretinal surgery. The scleral forces measurements in this study may enable a better understanding of tool-to-sclera interactions during vitreoretinal surgery and the proposed control strategies could be extended to other microsurgery and robot-assisted interventions.

The Impact of the COVID-19 Pandemic and Lockdown on Macular Hole Surgery Provision and Surgical Outcomes: A Single-Centre Experience

Purpose: We aimed to report the impact of the COVID-19 pandemic and related health policies and restrictions on the provision and efficacy of macular hole (MH) surgery. Methods: We carried out a retrospective cohort study. Two MH patient cohorts, those treated during the COVID-19 pandemic (12 months) and the pre-COVID-19 period (12 months before the lockdown) were reviewed and compared. Patient characteristics, time to consultation and surgery, MH size, baseline and postoperative visual acuity (VA) and failure rate were recorded and analysed. Results: A reduction of 43% in MH surgery occurred during the COVID-19 period (93 eyes vs. 53 eyes). Mean time to consultation and time to surgery increased significantly (52.7 days vs. 86.3 days, p < 0.01 and 51.3 days vs. 83.6 days, p = 0.01, respectively), while mean baseline and postoperative vision was significantly lower in the COVID-19 group (0.75 LogMAR vs. 0.63 LogMAR, p < 0.01 and 0.61 LogMAR vs. 0.44 LogMAR, p < 0.01, respectively). The median MH size was significantly larger in the COVID-19 group (296 μm vs. 365 μm, p = 0.016), and the failure rate increased from 7.6% to 15.4% (odds ratio 2.2 (95% CI: 0.72−6.8)). Conclusions: Our findings suggest the COVID-19 pandemic caused a significant reduction in MH surgery, increased waiting times and led to poorer surgical outcomes. For future pandemics, better strategies are required that allow semi-elective and elective surgery to continue in a timely fashion. Health providers should preserve the delivery of ophthalmological care, with enhanced encouragement to seek medical help for acute symptoms.

Optimization-based Concurrent Control of a High Dexterity Robot for Vitreoretinal Surgery

Vitreoretinal surgery requires dexterity and force sensitivity from the clinician. A system to cooperatively control an integrated surgical robot for high dexterity manipulation within the eye's vitreous space was developed and validated in simulation. The system is composed of a 2 degrees of freedom (DoF) snake-like continuum manipulator that is attached to the end-effector of a 5-DoF rigid robot arm. It is capable of receiving position and orientation commands from a 5-DoF input device in real-time, as well as following pre-planned trajectories. The manipulator is moved to each target pose in real-time, using an optimization method to calculate the inverse kinematics solution. Constraints on the position and orientation ensure the target pose does not harm the patient within the vitreous space, enabling the robot to safely assist the clinician with vitreoretinal surgery when operating in real-time. The simulation demonstrates the system's feasibility and benefits over the existing non-dexterous system.

Whitish Outer Retinal Spots in Retinal Detachment: Longitudinal Follow-up, Multimodal Imaging, and Clinical Utility

PURPOSE

To characterize the poorly understood phenomenon of whitish outer retinal spots that occasionally appear in retinal detachment (RD) DESIGN: Retrospective, consecutive case series SUBJECTS: Patients with RDs that had ophthalmoscopically-visible whitish outer retinal spots METHODS: All RDs with whitish outer retinal spots identified by one examiner over a 4-year interval were identified, and records were retrospectively reviewed.

MAIN OUTCOME MEASURES

Clinical and surgical observations, photography, and OCT RESULTS: Whitish outer retinal spots were visualized in 51 occurrences of RD: 45 in rhegmatogenous RDs (RRDs), 5 in tractional RDs (TRDs), and 1 in exudative RD (ERD). In RRDs the spots usually formed an arcuate band located between the causative retinal break and attached retina. However, 6 RRDs had spots located between a peripheral gutter of subretinal fluid (SRF) and attached retina. In 11 eyes, the spots were observed to appear over time and/or propagate to areas of detached retina more distal to the break. The spots corresponded to hyperreflective foci in the ellipsoid/interdigitation layers on OCT. The spots were isofluorescent on fluorescein angiography. The average duration of symptoms prior to surgical repair was 27.7 days. In 7 of 23 eyes surgically repaired by the author, the distribution of the spots assisted in localizing an occult retinal break. The spots sometimes appeared or persisted in areas of residual SRF but invariably resolved after retinal reattachment.

CONCLUSIONS

Whitish outer retinal spots can occur in all types of RD, not just RRDs. Observation of the spots can help to date an RD as subacute and should prompt surgery. Because the spots occur in distributions that reflect the path of spread of subretinal fluid, their position can be used to localize causative retinal breaks.

Improved Integrated Robotic Intraocular Snake

Retinal surgery can be performed only by surgeons possessing advanced surgical skills because of the small, confined intraocular space, and the restricted free motion of instruments in contact with the sclera. Snake-like robots could be essential for use in retinal surgery to overcome this problem. Such robots can approach from suitable directions and operate delicate tissues when performing retinal vein cannulation, epiretinal membrane peeling and so on. In this study, we propose an improved integrated robotic intraocular snake (I²RIS), which is a new version of our previous IRIS. This update focuses on the dexterous distal unit design and the drive unit design. The proposed dexterous distal unit consists of small elements with reduced contact stress. The proposed drive unit includes a new wire drive mechanism where the drive pulley is mounted at a right angle relative to the actuation direction (also, relative to the conventional direction). A geometric analysis and mechanical design show that the proposed drive mechanism is simpler and easier to assemble and yields higher accuracy than the conventional drive mechanism. Furthermore, considering clinical use, the instrument of the I²RIS is detachable from the motor unit for cleaning, sterilization, and attachment of various surgical tools. Weighing merely 31.3 g, the proposed mechanism is only one third of the weight of the conventional IRIS. The basic functions and effectiveness of the proposed mechanism are verified by experiments on 5:1 scaled-up models of the dexterous distal unit and actual-size models of the instrument and motor units.

Montgomery and informed consent during Covid-19: Pneumatic retinopexy versus pars plana vitrectomy or scleral buckling for retinal detachment repair

Recent reports suggest that the use of an outpatient-based procedure (pneumatic retinopexy, PR) for retinal detachment repair should be encouraged within the UK, especially in light of Covid-19 and possible restrictions/competing demands on access to operating theatres. It is therefore essential that patients receive comprehensive information about the risks and benefits of this approach compared with a formal surgical repair either by pars plana vitrectomy (PPV) and/or scleral buckling (SB). We report a retrospective case series of retinal detachments (RD) satisfying the strict selection criteria for PR but who were managed with formal surgery. Single-operation success rate for PPV/SB at six months follow-up was 93.8% in our study, higher than published primary success rates for PR (60-80%). When counselling patients for possible PR, the ease, speed and potentially reduced co-morbidity of an outpatient-based procedure needs to be balanced against its significantly higher failure rate in comparison with primary PPV/SB.

Improved Integrated Robotic Intraocular Snake: Analyses of the Kinematics and Drive Mechanism of the Dexterous Distal Unit

Retinal surgery can be performed only by surgeons possessing advanced surgical skills because of the small, confined intraocular space, and the restricted free motion of the instruments in contact with the sclera. Snake-like robots may be essential for use in retinal surgery to overcome this problem. Such robots can approach the target site from suitable directions and operate on delicate tissues during retinal vein cannulation, epiretinal membrane peeling, and so on. We propose an improved integrated robotic intraocular snake (I2RIS), which is a new version of our previous IRIS. This study focused on the analyses of the kinematics and drive mechanism of the dexterous distal unit. This unit consists of small elements with reduced contact stress achieved by changing wire-hole positions. The kinematic analysis of the dexterous distal unit shows that it is possible to control the bending angle and direction of the unit by using two pairs of drive wires. The proposed drive mechanism includes a new pull-and-release wire mechanism in which the drive pulley is mounted at a right angle relative to the actuation direction (also, relative to the conventional direction). Analysis of the drive mechanism shows that compared to the previous drive mechanism, the proposed mechanism is simpler and easier to assemble and yields higher accuracy and resolution. Furthermore, considering clinical use, the instrument of the I2RIS is detachable from the motor unit easily for cleaning, sterilization, and attachment of various surgical tools. Analyses of the kinematics and drive mechanism and the basic functions of the proposed mechanism were verified experimentally on actual-size prototypes of the instrument and motor units.

Lightweight Learning-Based Automatic Segmentation of Subretinal Blebs on Microscope-Integrated Optical Coherence Tomography Images

PURPOSE

Subretinal injections of therapeutics are commonly used to treat ocular diseases. Accurate dosing of therapeutics at target locations is crucial but difficult to achieve using subretinal injections due to leakage, and there is no method available to measure the volume of therapeutics successfully administered to the subretinal location during surgery. Here, we introduce the first automatic method for quantifying the volume of subretinal blebs, using porcine eyes injected with Ringer's lactate solution as samples.

DESIGN

Ex vivo animal study.

METHODS

Microscope-integrated optical coherence tomography was used to obtain 3D visualization of subretinal blebs in porcine eyes at Duke Eye Center. Two different injection phases were imaged and analyzed in 15 eyes (30 volumes), selected from a total of 37 eyes. The inclusion/exclusion criteria were set independently from the algorithm-development and testing team. A novel lightweight, deep learning-based algorithm was designed to segment subretinal bleb boundaries. A cross-validation method was used to avoid selection bias. An ensemble-classifier strategy was applied to generate final results for the test dataset.

RESULTS

The algorithm performs notably better than 4 other state-of-the-art deep learning-based segmentation methods, achieving an F1 score of 93.86 ± 1.17% and 96.90 ± 0.59% on the independent test data for entry and full blebs, respectively.

CONCLUSION

The proposed algorithm accurately segmented the volumetric boundaries of Ringer's lactate solution delivered into the subretinal space of porcine eyes with robust performance and real-time speed. This is the first step for future applications in computer-guided delivery of therapeutics into the subretinal space in human subjects.

Evolving trends in strabismus following retinal surgery: is there still a role for botulinum toxin?

Purpose Ocular motility disturbances following retinal detachment surgery are well documented, resulting in ocular misalignment and disabling diplopia. Interestingly, there has been a downward trend over the last decade across the United Kingdom with the evolution of refined vitrectomy techniques and instrumentation. We aim to report our updated experience on factors influencing botulinum toxin outcomes in view of the trend toward vitrectomy. Methods The Moorfields strabismus service carried out a follow-up retrospective study of all subjects that received botulinum toxin for retinal surgery-related strabismus at our center over an eleven-year period. All new onset constant or intermittent strabismus following retinal detachment surgery were included. Botulinum toxin response was stratified to good and poor. Results 32 patients fulfilled our criteria, with a mean follow-up of 20 months. The majority were vitrectomised eyes (62%), presented with diplopia (60%) and exotropia (66%). All isolated and combined vertical deviations (18%) were noted among cryobuckled eyes only. Baseline largest mean horizontal deviation was 49 and 51 prism diopters (PD) among the good and poor responders, respectively. A statistically and clinically significant reduction in the horizontal angle of deviation was noted among the good (p < .0001) responders, requiring a mean of six injections, in comparison to the poor responders (p = .03). Of the good responders, five patients (16%) with decompensated phorias regained fusion control. A small number of complications (15%) were noted, the most marked being intractable diplopia in a good responder (3%) with failure to fuse. Conclusions Botulinum toxin is a useful treatment modality, particularly when surgical options are limited. It can restore binocularity in patients with preexisting fusion potential. Ocular cosmesis can be achieved but requires ongoing injections. Barriers to fusion restoration include multiple retinal surgeries, persistent macula pathology and central-peripheral retinal rivalry. This highlights the need for rigorous baseline macula assessment to allow a tailored approach when considering botulinum toxin therapy for strabismus.

Loss of retinal tension and permanent decrease in retinal function: a new porcine model of rhegmatogenous retinal detachment

PURPOSE

Permanent loss of visual function after rhegmatogenous retinal detachment can occur despite successful surgical reattachment in humans. New treatment modalities could be explored in a detachment model with loss of retinal function. In previous porcine models, retinal function has returned after reattachment, regardless of height and duration of detachment. Difference in retinal tension between the models and the disease might explain these different outcomes. This study investigates, for the first time in an in vivo porcine model, another characteristic of rhegmatogenous retinal detachment - the loss of retinal tension.

METHODS

Left eyes (n = 12) of 3-month-old domestic pigs were included. Baseline multifocal electroretinogram (mfERG) and a fundus photograph were obtained following anaesthesia (isoflurane). The pigs were vitrectomized, saline was injected subretinally, and the RPE was removed. The eyes were evaluated at 2, 4 and 6 weeks after surgery. Four eyes were enucleated at each evaluation for histologic examinations.

RESULTS

A retinal detachment structurally resembling rhegmatogenous retinal detachment was induced in 11 out of 12 pigs. MfERG amplitudes were significantly decreased despite partial reattachment four and 6 weeks after detachment. The retinal thickness decreased with 27%, the inner nuclear layer degenerated, Müller cells hypertrophied, and outer segments were lost. In the ganglion cell layer, cellularity increased and there was cytoplasmic staining with Cyclin D1. Vimentin and GFAP staining for glial cells increased. After 2 weeks of detachment, the ganglion cells had lost their nucleus and nucleolus.

CONCLUSIONS

Loss of retinal tension in the detached retina seems to induce permanent damage with loss of retinal function. Death of ganglion cells, observed as soon as 2 weeks after detachment, explains the permanent loss of retinal function. The new model enables investigations of time-relationship between retinal detachment and lasting damage in addition to exploration of novel treatment modalities.

Postoperative Analgesic Efficacy of Sub-Tenon's Block with Levobupivacaine in Retinal Surgery under General Anesthesia

Background:

Vitreoretinal surgery is associated with undesirable intraoperative and postoperative complications including pain, postoperative nausea and vomiting, and oculocardiac reflex (OCR). Systemic analgesics have side effects and are contraindicated in some cases. We hypothesized that the preoperative sub-Tenon's injection of levobupivacaine with general anesthesia would decrease postoperative pain and intraocular pressure as well as the incidence of complication.

Methods:

Eighty patients who were presented for vitreoretinal surgery, aged 30–60 years, were enrolled in the study. General anesthesia was administrated to all patients; then, they were randomized into two equal groups (40 each) – Group I: patients received 5 mL placebo solution for sub-Tenon's block and Group II: patients received 4 mL levobupivacaine 0.5% in 1 mL saline for sub-Tenon's block. Postoperative pain was evaluated using a verbal pain scale. Surgeon satisfaction, postoperative analgesic consumption, and perioperative hemodynamics were also reported.

Results:

Verbal rating pain scores were significantly lower at the first 6 h postoperative in Group II (sub-Tenon's levobupivacaine) compared to Group I (sub-Tenon's placebo). First analgesic rescue time and total dose of analgesic consumption were significantly reduced in Group II compared to Group I. There was a lower incidence of OCR with sub-Tenon's levobupivacaine (Group II), also surgeon satisfaction was significantly superior in the same group.

Conclusion:

The combination of general anesthesia with sub-Tenon's block using levobupivacaine in retinal surgery patients reduces pain scores after surgery; total analgesia requirement also decreases the incidence of OCR.

Treatment of recurrent myopic macular hole using membrane of plasma rich in growth factors

Purpose

To describe the case of a patient with a recurrent large myopic macular hole (MH), who was successfully treated with a plasma rich in growth factors (PRGF) membrane.

Case Report

A 71-year-old patient presented a myopic MH in his right eye. One month later, pars plana vitrectomy with internal limiting membrane (ILM) peeling was performed, achieving closure of the MH. Three months later a recurrence was observed (700 µm) without visual acuity (VA) improvement. A new surgery was carried out placing an autologous PRGF-membrane into the MH, and performing a fluid-gas exchange at the end of the surgery. After two months of follow-up, the MH was completely closed, obtaining the anatomic recovery of the foveal depression, and improving the VA to 0.1. No adverse reactions were associated with the use of PRGF and there were no new recurrences of the MH in a follow-up period of six months.

Conclusion

The use of PRGF-membrane can be used as adjunctive therapy in the surgical repair of recurrent large myopic MHs, thus improving anatomic and visual outcomes.

Missed retinal breaks in rhegmatogenous retinal detachment

AIM

To evaluate the causes and associations of missed retinal breaks (MRBs) and posterior vitreous detachment (PVD) in patients with rhegmatogenous retinal detachment (RRD).

METHODS

Case sheets of patients undergoing vitreo retinal surgery for RRD at a tertiary eye care centre were evaluated retrospectively. Out of the 378 records screened, 253 were included for analysis of MRBs and 191 patients were included for analysis of PVD, depending on the inclusion criteria. Features of RRD and retinal breaks noted on examination were compared to the status of MRBs and PVD detected during surgery for possible associations.

RESULTS

Overall, 27% patients had MRBs. Retinal holes were commonly missed in patients with lattice degeneration while missed retinal tears were associated with presence of complete PVD. Patients operated for cataract surgery were significantly associated with MRBs (P=0.033) with the odds of missing a retinal break being 1.91 as compared to patients with natural lens. Advanced proliferative vitreo retinopathy (PVR) and retinal bullae were the most common reasons for missing a retinal break during examination. PVD was present in 52% of the cases and was wrongly assessed in 16%. Retinal bullae, pseudophakia/aphakia, myopia, and horse shoe retinal tears were strongly associated with presence of PVD. Traumatic RRDs were rarely associated with PVD.

CONCLUSION

Pseudophakic patients, and patients with retinal bullae or advanced PVR should be carefully screened for MRBs. Though Weiss ring is a good indicator of PVD, it may still be over diagnosed in some cases. PVD is associated with retinal bullae and pseudophakia, and inversely with traumatic RRD.

David Kasner, MD, and the Road to Pars Plana Vitrectomy

David Kasner, MD (1927-2001), used his extensive dissections of eye bank eyes and experiences in teaching cataract surgery to resident physicians to realize that excision of vitreous when present in the anterior chamber of eyes undergoing cataract surgery was preferable to prior intraoperative procedures. Noting that eyes tolerated his maneuvers, he then performed planned subtotal open-sky vitrectomies; first on a traumatized eye in 1961, then on two eyes of patients with amyloidosis (1966-1967). The success of these operations was noted by others, most particularly Robert Machemer, MD. Kasner's work directly led to further surgical developments, including closed pars plana vitrectomy.

Localized RPE Removal with a Novel Instrument Aided by Viscoelastics in Rabbits

PURPOSE

We developed a surgical method for localized and atraumatic removal of the retinal pigment epithelium (RPE) with a novel instrument.

METHODS

Bleb retinal detachments (bRD) were raised with balanced salt solution (BSS) following vitrectomy in 27 rabbits. The RPE was scraped with 3 loop variants (polypropylene [PP], 0.1 mm; PP, 0.06 mm; metal, 0.1 mm) of a custom-made instrument. Stabilization of bRDs with BSS or various concentrations (0.1%-0.5%) of hyaluronic acid (HA) was video analyzed. Perfusion-fixed samples of scraped areas and controls were studied by light and transmission electron microscopy.

RESULTS

The bRDs were sufficiently stabilized by ≥0.25% HA. Using the PP 0.1 mm loop with a single forward/backward stroke, an area of ca. 2.5 × 1.5 mm was nearly devoid of RPE, yet did show occasional Bruch's membrane (BM) defects combined with choriocapillaris hemorrhages in 13% of the bRDs. A single scrape with PP 0.06 mm resulted in unsatisfactory RPE denudement, while repeated scraping maneuvers caused more BM defects and hemorrhages. The metal loop resulted in incomplete RPE removal and massive intraoperative subretinal hemorrhages. Histologically, intact photoreceptor outer segments (POS) were observed above the RPE wounds in bRDs. Controls with bRDs alone showed an intact RPE monolayer with microvilli, with few engulfed remains of POS.

CONCLUSIONS

Localized removal of RPE in HA stabilized bRD can be achieved by a PP 0.1 mm loop instrument.

TRANSLATIONAL RELEVANCE

Removal of degenerated RPE may aid RPE cell replacement strategies.

Use of a new intra-ocular spectral domain optical coherence tomography in vitreoretinal surgery

PURPOSE

To describe the use of a novel intra-ocular side-scanning probe enabling the acquisition of spectral-domain optical coherence tomography (SD-OCT) images during surgery in a series of patients with complex forms of retinal detachment.

METHODS

A 23-gauge, side-scanning SD-OCT probe (C7 System; LightLab Imaging, Inc/St Jude Medical, St. Paul, MN, USA) in a 20-gauge catheter, was used to acquire the intra-operative OCT images in seven patients with vitreoretinal diseases. Twenty-five gauge pars plana vitrectomy (PPV) was performed in every patient in a standard fashion. After enlarging the temporal sclerotomy to a 20-gauge port, all the patients were scanned with intra-ocular side-scanning SD-OCT, during different steps of the surgery based on surgeon needs. Scans were recorded real time and directly evaluated on a screen during surgery. Optical coherence tomography (OCT) scans were judged beneficial when they would recognize structures otherwise not seen on biomicroscopy.

RESULTS

The intra-ocular SD-OCT has been helpful in acquiring extra information during vitreoretinal surgery such as the detection of the presence of otherwise invisible membranes (epiretinal membrane, subretinal membrane), the location of small tears and the identification of the retinal plane under suboptimal conditions for visualization.

CONCLUSION

The use of an intra-ocular SD-OCT can expand upon visual cues during surgery, helping in the decision-making process and allowing additional deliberate surgical manoeuvres aimed at improving surgical outcomes.

Superficial extraconal blockade for vitreoretinal surgery

Context:

Needle length plays an important role for the success of ophthalmic block. The standard practice is to use 25 mm needles length; however, unnecessarily long needles may increase the risk of complications especially in the presence of staphyloma or previous scleral buckle.

Aims:

This work was designed to compare the efficacy of using 15 and 25 mm needle in performing extraconal block for patients undergoing vitreoretinal surgery.

Settings and Design:

Prospective randomized double blinded study.

Materials and Methods:

A total of 120 patients were enrolled in this study and were divided in two groups. In group (1) extraconal block was performed using 25 mm needle, while in group (2) 15 mm needle was used. After primary injection, assessment of the block was done by an anesthesiologist who was unaware of the needle used. If satisfactory akinesia was not achieved a supplementation was provided. At the end of the procedures, patients and surgeons were asked to assess their pain and satisfaction with the anesthetic technique.

Statistical Analysis used:

The sample size calculation using N-Quary version 4. Numerical and categorical data were analyzed using an independent sample, a two-tailed t-test, and chi-square test, respectively.

Results:

The volume of primary injectable was significantly higher in group 2. The two groups were comparable as regards total volume of local anesthetic, supplementation rate, akinesia, pain score, and surgeon satisfaction.

Conclusions:

Using 15 mm needle length to perform extraconal blockade for posterior segment procedures is equally effective to 25 mm needle.

Visual loss following intraocular gas injection

INTRODUCTION

The range of indications for vitreoretinal surgery has widened in recent years, and intraocular gas application is frequently performed as part of retinal surgery, with the aim of achieving long-acting tamponade.

METHODS

Selective literature review.

RESULTS

An intraocular gas bubble containing perfluoropropane (C(3)F(8)) or sulfur hexafluoride (SF(6)) can expand during anesthesia due to nitrous oxide diffusion and cause retinal ischemia and postoperative blindness. A decrease in atmospheric pressure associated with travel to high altitude can have the same effect. Case reports suggest that, considering physical properties of these gases and ocular physiology, patients remain at risk for at least three months after intraocular gas application.

DISCUSSION

Both doctors and patients need to be well informed about the hazards of intraocular gas application as good communication may prevent complications. If in doubt, the anesthesiologist should avoid nitrous oxide, in particular in the unconscious patient.