Retina surgery has undergone a revolutionary transformation in recent years, driven by technological innovations that enhance visualization, improve precision, and expand treatment possibilities.
This article reviews some cutting-edge technologies that are reshaping the landscape of vitreoretinal procedures and improving outcomes for patients with previously challenging or untreatable conditions.
Evolution of vitrectomy systems
The evolution of vitrectomy instrumentation has been characterized by progressive miniaturization, with 27-gauge systems currently representing the smallest incision size available to vitreoretinal surgeons. This advancement in instrumentation has been accompanied by clinical evaluation to ensure that the benefits of smaller incisions are not offset by compromised surgical efficacy or safety.
A comprehensive study published in 2018 assessed the long-term outcomes of 27-gauge pars plana vitrectomy (PPV) in 390 eyes with various posterior segment diseases.1 Results demonstrated that 27-gauge PPV was well tolerated across a diverse range of surgical indications, with notably low rates of post-operative complications. This large-scale assessment provided important validation for the clinical application of this ultra-small-gauge technology.
Comparing 25- and 27-gauge instrumentation
The comparative efficacy of 27-gauge instrumentation has been evaluated against larger-gauge alternatives across different pathologies. A 2021 retrospective study compared 27- and 25-gauge vitrectomy specifically in patients with proliferative diabetic retinopathy and tractional retinal detachment—conditions that represent significant technical challenges for ultra-small-gauge instrumentation.2 The findings revealed no significant difference in mean operation time between the two approaches.
Post-operatively, there were no significant differences in ocular hypertension, hypotony, best-corrected visual acuity (BCVA) improvement, recurrent vitreous hemorrhage, or reoperation rate. Interestingly, the 27-gauge approach was associated with significantly reduced microforceps usage and fewer wound sutures than the 25-gauge group.2
Similarly, a 2020 study compared 27 and 23-gauge instruments in patients undergoing vitrectomy for macular pucker, macular hole, or vitreous hemorrhage.3 Results demonstrated that the rate of hypotony on post-operative day one and the need for sclerotomy stitching at the end of surgery were significantly more frequent in the 23-gauge group compared to the 27-gauge group.
However, the mean duration of surgery, anatomic success, and BCVA improvement were comparable between the two groups. These findings suggest that 27-gauge instrumentation offers advantages in wound integrity without compromising surgical efficacy.3
Fluid dynamics principles and adaptations
Poiseuille’s Law and implications for instrument design
The trend toward smaller-gauge instrumentation presents unique challenges related to fluid dynamics during vitrectomy procedures.
Understanding these challenges requires consideration of Poiseuille's Law, which describes the relationship between flow rate and instrument dimensions: Flow Rate = Q = (ηr4ΔP) / 8μl. In this equation, ∆P represents the pressure difference across the length (l) of the needle, r is the internal radius of the probe, and η is the viscosity of the aspirated liquid.
Flow rate, measured as volume per unit time, is a critical parameter in vitrectomy procedures, with higher rates generally associated with shorter surgical duration, enhanced intraocular pressure stability, and reduced risk of retinal injury. Since flow rate is directly proportional to the fourth power of the instrument radius, even minor reductions in instrument size result in significant decreases in flow rate.
For example, reducing instrumentation from 25-gauge to 27-gauge results in a theoretical 59% reduction in flow rate if all other variables remain constant. To counteract this reduction, several compensatory approaches have been developed. Modern vitrectomy consoles can generate up to 650mmHg of vacuum, effectively increasing the pressure differential (∆P) to enhance aspiration efficiency despite smaller instrument dimensions.
Cutting speed in vitreoretinal surgery
Additionally, the non-Newtonian properties of vitreous fluid—specifically, its variable viscosity under different mechanical stresses—can be exploited during surgery. High cutting frequencies effectively create smaller vitreous fragments, thereby reducing the effective viscosity of the aspirated material and increasing the instrument's flow rate.
However, increased cutting frequencies introduce another challenge: a reduction in the duty cycle of the cutter. Vitrectomy cutters operate in two phases—the cutting phase and the closed phase. During the cutting phase, the blade opens, cuts the vitreous, and the vitreous is aspirated into the port, and the blade closes.
During the closed phase, the blade obstructs the port, temporarily halting new vitreous aspiration while previously aspirated material continues through the instrument. Higher cutting frequencies reduce the proportion of time that the port remains open (the duty cycle), potentially limiting flow despite the benefits of reduced vitreous viscosity.
Cutting technology innovations
High-speed cutting
Beyond instrument gauge, significant innovations have emerged in cutter design and cutting frequency capabilities, measured as cuts per minute (cpm). Higher cutting frequencies have been developed to enhance surgical efficiency and safety during vitreoretinal procedures.
A 2023 study directly compared the efficiency and safety of 27-gauge vitreous cutters operating at 20,000cpm versus 10,000cpm.4 The investigation revealed that vitrectomy duration was significantly shorter in the 20,000 cpm group.
Additionally, while one patient in the 10,000 cpm group experienced post-operative vitreous hemorrhage, no such complications were observed in the 20,000cpm group. These findings suggest that higher cutting speeds may contribute to procedural efficiency and potentially improved safety profiles.4
Dual-blade cutting mechanisms
Dual-blade vitrectomy cutters have been developed to address the limitations associated with reduced duty cycles at higher cutting frequencies. These instruments utilize two cutting edges that perform cuts on each cycle's forward and backward strokes. A cutter operating at 10,000cpm delivers 20,000cpm through this dual-action mechanism.5
The key advantage of this design is that the port remains open for a greater proportion of each cycle, effectively increasing the duty cycle and allowing more continuous aspiration. By simultaneously optimizing both cutting frequency (which reduces the effective viscosity of vitreous) and duty cycle (which enhances aspiration efficiency), dual-blade cutters significantly improve vitreous removal while minimizing fluidic instability and retinal traction.5
Beveled-tip designs
In addition to dual-blade technology, the configuration of the cutter tip itself has undergone essential refinements. Beveled-tip designs have demonstrated superior performance to traditional flat-tip cutters, with studies showing greater velocity in both frontal and proximal flow aspiration. These characteristics result in higher overall aspiration rates and enhanced reflux flow velocity.6
The advantages of beveled-tip cutters extend beyond improved flow dynamics to enhanced tissue dissection capabilities. A novel "shovel and cut" technique for managing diabetic tractional retinal detachments has been investigated using beveled-tip technology.6
Research findings demonstrate that this unique design allows more effective dissection of particularly challenging plaques within diabetic membranes. Surgeons reported the ability to remove these plaques with greater control and safety, likely due to reduced tractional forces exerted on the retina through improved tissue manipulation.7
An overview of specialized instrumentation
The most advanced vitrectomy system currently available is the UNITY HYPERVIT, which integrates multiple technological innovations to optimize surgical performance. With cutting speeds reaching 30,000cpm, dual-blade design, beveled tip, and pneumatic drive technology, this system provides maximal flow rates during vitrectomy procedures.8
UNITY Vitreoretinal Cataract System
The UNITY HYPERVIT introduces several groundbreaking features to vitreoretinal surgery. It represents the first probe equipped with multi-spot illuminated laser capability, allowing for the delivery of one, two, or four laser spots in a single application. This innovation significantly enhances treatment efficiency, particularly in procedures such as diabetic retinopathy management, where numerous laser spots must be applied to the retina.7
Another innovative feature of this system is its dynamic stiffeners, which allow the instrument to maintain flexibility during insertion and manipulation within the eye while providing increased rigidity when the surgeon needs. This variable stiffness characteristic enables precise control without compromising the maneuverability essential for operating in the confined space of the vitreous cavity.
The UNIFYE Gas Delivery System incorporated into the UNITY platform offers predictable, precise gas-to-air ratio control.8 This feature is significant when gas is injected into the vitreous cavity as a tamponade agent, as the volume of gas relative to vitreous fluid significantly impacts surgical outcomes.
The system provides precise, real-time control of the desired intraocular pressure (IOP) setpoint, allowing optimal intra-operative pressure management, retinal reattachment, and eventual gas removal from the vitreous cavity.
Additional features include UNITY illumination with customizable RGB lighting that boasts an extended 10,000-hour lifespan. The console has been designed to streamline workflow efficiency with faster setup and teardown processes and reduced vitrectomy connections, enhancing overall procedural efficiency.
Finesse Sharkskin ILM peeling forceps
The Finesse Sharkskin internal limiting membrane (ILM) peeling forceps represents a significant advancement in instrumentation for macular procedures requiring ILM removal. This innovative tool features a laser-ablated microserrated surface, an optimized grasping platform, and an angled tip closure designed to minimize membrane shedding during delicate macular procedures.
A 2024 comparative study evaluated the performance of Sharkskin forceps against conventional end-grasping forceps for ILM peeling across various macular pathologies.9 The study involved 70 patients with macular hole, epiretinal membrane, vitreomacular traction syndrome, and myopic foveoschisis requiring pars plana vitrectomy and ILM peeling. Patients were equally distributed between the Sharkskin and end-grasping forceps groups.9
Results demonstrated significantly fewer attempts to initiate ILM peeling in the Sharkskin group than in the end-grasping group. More importantly, patients in the Sharkskin group exhibited a lower incidence of retinal microstructure damage and a smaller mean depth of inner retinal injury at the initiating site at 3-month post-operative follow-up.9
Robotizing vitreoretinal surgery
The integration of robotic surgery has become common in various surgical specialties. Specifically in gynecology, urology, and general surgery, the da Vinci Robotic Surgical System has emerged as a means for improved maneuverability and precision. The success in other surgical fields has inspired the development of robotic technology in ophthalmologic surgery.
An experimental study in 2009 developed and evaluated a prototype robotic system designed to assist vitreoretinal surgery.10 The primary outcome measures compared the average maximum deviation in pointing accuracy tests on graph paper and animal eye models, between manually conducted procedures and those undertaken with robotic assistance.
The success rate of creating a posterior vitreous detachment, retinal vessel sheathotomy, and retinal vessel microcannulation was assessed. Results showed that pointing accuracy was superior with robotic assistance on graph paper and in animal eye models. Creating PVD, RVS, and retinal vessel microcannulation was feasible in four of four attempts, four of four attempts, and two of four, respectively.10
One primary concern when performing vitreoretinal surgery is the impact of a surgeon’s physiologic tremor. At microscopic distances, even a minor tremor can impact the accuracy of movements and result in less desirable outcomes for the patient.
One review assessed the literature for factors contributing to the physiologic tremor during eye surgery.11 One of the factors they found that had the potential to assist in overcoming tremors was robotic technology. Although advancements have been made in instrument development, ophthalmologists are still limited by the dexterity of their tools.
When operating, instruments are limited to 4° of movement, tilt in two directions, and rotation and translation along the long axis of the instrument. Robotic surgery allows for improved instrument tip dexterity, increasing the precision and accuracy of the surgeon’s movements.
Preceyes Robotic Surgical System
The Preceyes Robotic Surgical System is a robotic assistive device designed to enhance precision and control in vitreoretinal surgeries. This system has been utilized in complex retinal procedures, including membrane peeling, subretinal injections, and retinal vein cannulation. The system has a motion controller that the surgeon uses to command the surgical tool-tip position. This controller can be equipped with standard microsurgical instruments (forceps, injectors).12
One study used an artificial retina model to compare manual and robotic-assisted simulated subretinal injections.13 Success in creating a bleb without reflux, injection duration, drift, tremor, and increase in the diameter of the puncture hole was analyzed. Results showed that robotic assistance improved drift, tremor, and enlargement of the retinal hole, and allowed for prolonged injection times. It also allowed for a higher bleb formation rate with a moderate reflux reduction.
Studies on the safety of the Preceyes Robotic Surgical System
The first randomized controlled trial in 2022 explored the feasibility and safety of performing common surgical steps in epiretinal membrane peeling using the Preceyes Robotic Surgical System.14 In total, 15 patients were randomized to robot-assisted or manual surgery in a 2:1 ratio.
Results showed that all steps performed with the robotic system were feasible with no clinical adverse events or complications. While the surgical time was longer in the robot-assisted group, the duration over the length of the study decreased from 72 to 46 minutes.14 In addition, the distance travelled by the forceps was shorter in the robot-assisted group.
Another clinical trial evaluated robot-assisted surgery in patients requiring dissection of the epiretinal or inner limiting membrane over the macula.15 Results showed that surgical outcomes were equally successful in the robotic-surgery and manual-surgery groups. Like the previous study, dissection took longer with robotic surgery than with manual surgery.
Furthermore, the study proved the robot's feasibility in injecting recombinant tPA under the retina. Another study evaluating robot-assisted epiretinal membrane peeling showed a substantial reduction in pre- and intra-operative times throughout the study.16
Moreover, a questionnaire found that surgeons noted:
- Improved hand strain
- Increased ease
- Reduced stress as familiarity with the system increased
Retinal implants and drug delivery systems
Retinal implant technology represents another frontier in ophthalmology, offering potential visual restoration for patients with previously untreatable conditions. These devices aim to bypass damaged photoreceptors by directly stimulating remaining viable retinal cells or replacing lost cellular function through innovative approaches.
Recent advances in bioelectronics, materials science, and surgical techniques have enabled significant progress in this field, with several implantable systems now demonstrating meaningful visual function improvements in clinical trials.
PRIMA system for dry AMD
The PRIMA system represents an innovative approach to restoring light perception in patients with atrophic dry age-related macular degeneration (AMD).17 This photovoltaic subretinal implant operates through an elegant integration of external and internal components.
A camera incorporated into the external unit captures visual information from the environment, which is then processed and transmitted via projected infrared light directly onto the implanted microchip. Upon receiving this information, the implant generates electrical stimulation to adjacent retinal neurons, bypassing the degenerated photoreceptors.17
Clinical evaluation of the Prima system has yielded promising initial results. In a study of five patients with advanced geographic atrophy (at least three optic disc diameters in size), no foveal light perception, and BCVA ranging from 20/400 to 20/1000 in the worse-seeing eye, the prosthesis was successfully implanted beneath the macula in all cases.
All five patients subsequently demonstrated the ability to perceive white-yellow prosthetic visual patterns with adjustable brightness in previously scotomatous areas.17 Importantly, residual natural visual acuity was preserved in all patients following implantation, suggesting that the device does not compromise remaining photoreceptor function.17
While preliminary, these findings highlight this technology's potential to restore basic visual function in patients with advanced dry AMD, a condition for which few effective treatments currently exist.
Argus II Retinal Prosthesis System for retinitis pigmentosa
The Argus II Retinal Prosthesis System has been developed to restore functional vision in patients with profound vision loss due to retinitis pigmentosa or outer retinal degeneration.18 This epiretinal implant functions through a complex integration of external and internal components. An external camera mounted on glasses captures visual information, which is processed and wirelessly transmitted to the implanted electronics.
The implant is secured to the sclera and connected via an electrode cable to an intraocular epiretinal electrode array, which is anchored to the retina's surface using a specialized retinal tack. This electrode array directly stimulates the inner retina and ganglion cells, bypassing the degenerated photoreceptors.18
Studies on the safety and efficacy of the Argus II implant
Long-term evaluation of the Argus II has demonstrated both safety and functional efficacy. In a 5-year follow-up study of 30 patients, 24 remained implanted, with only one serious adverse event reported after the 3-year timepoint. Patients consistently performed significantly better on visual function tests and functional vision tasks with the device activated than when it was turned off, demonstrating sustained utility over time.18
These findings were reinforced by another long-term outcome study, which included 17 patients who completed the full follow-up protocol.19 Over 70% of participants reported positive impacts on functional vision and overall well-being.
Significant improvements were observed in specific daily activities, including finding doorways, estimating obstacle sizes, visually locating place settings on dining tables, and detecting people in non-crowded settings. Only two device or procedure-related serious adverse events were observed and resolved with appropriate treatment.19
Complications linked with the Argus II implant
As with any implantable device, the Argus II is associated with specific complications that warrant careful consideration. A comprehensive retrospective analysis of 274 patients (30 from initial clinical trials and 244 from the post-approval phase) implanted between 2007 and 2017 provided valuable insights into adverse events.19 In the post-approval cohort, 83% of patients experienced no device or surgery-related serious adverse events.
Conjunctival erosion emerged as the most common complication, with an incidence rate of 6.2% over nearly 6 years of follow-up. Anatomically, 55% of erosion cases occurred in the inferotemporal quadrant, 25% in the superotemporal quadrant, and 20% in both locations. Temporally, 60% of erosion events developed within 15 months of implantation, and 85% within the first 2 years.19
These findings have led to essential refinements in patient selection and surgical technique. Patients with previous ocular surgery, conjunctival damage, or systemic disorders affecting conjunctival health may not be ideal candidates for implantation.19
Several surgical modifications have been proposed to reduce erosion risk, including refinements in suture management. By cutting suture tails longer and inverting them posteriorly under the implant's silicone body, surgeons have prevented them from protruding toward the conjunctiva.19
An alternative approach positions the knots under the silicone tab, allowing them to sit between the sclera and device rather than under the conjunctiva. Material selection has also proven significant—when 5-0 Mersilene suture was used instead of nylon, the erosion rate decreased from 14.9 to 3.6%.19 These technical refinements highlight the importance of ongoing evaluation and improvement of surgical approaches for retinal implant technology.
Alpha AMS
The Alpha AMS represents another approach to electronic retinal prosthesis for end-stage retinal degeneration. The Alpha AMS utilizes a subretinal implantation strategy, unlike epiretinal devices like the Argus II.
The system consists of a metal-oxide-semiconductor chip attached to a distal polyimide foil, which together comprise the subretinal components of the implant. The device measures 4mm × 3.2mm × 70μm and incorporates 1,600 individual pixel cells. Each pixel cell (70μm × 70μm) includes a photodiode, amplifier, and stimulation electrode.20
This implant is positioned between the retina and retinal pigment epithelium, allowing each pixel cell to directly stimulate adjacent bipolar cells according to the local light intensity detected by its photodiode. This design enables a more physiological stimulation pattern than epiretinal approaches, as it targets the retinal network earlier in the visual processing cascade.
Studies on the efficacy of the Alpha AMS device
Clinical evaluation of the Alpha AMS has been conducted through two trials, with several interim reports published. In one report, implant-mediated light perception was observed in 13 of 15 patients, with the same proportion achieving implant-mediated localization of visual targets.20
Comparison of performance with the implant activated versus deactivated revealed that detection ("how many") and localization ("where") of geometric shapes were significantly better at all assessment timepoints when the implant was functioning.
Recognition scores ("what") did not show statistically significant differences. The study also assessed patients' ability to correctly position objects in target regions, with significantly better performance when the implant was activated at months 2 and 12 post-implantation.20
Adverse events associated with the Alpha AMS
Serious adverse events were reported in four patients, including two implant movements, four instances of conjunctival erosion or dehiscence, one case of pain around the coil, and one partial reduction of silicone oil tamponade. All complications were successfully managed with appropriate interventions.
A notable case study from this clinical trial documented the highest visual acuity achieved with an electronic retinal device.21 The patient attained a reading vision of 0.04 decimal (equivalent to 1.39 LogMAR, or 20/500). Additionally, the patient demonstrated perception and partial identification of obstacles and distance evaluation capabilities in both daylight and nighttime conditions.21
This case represents an important proof-of-concept for the potential of subretinal implants to restore functionally meaningful vision.
IRIS II
The Intelligent Retinal Implant System II (IRIS II), developed by Pixium Vision SA, offers another approach to addressing blindness caused by inherited photoreceptor degeneration, particularly retinitis pigmentosa.
This system features an exchangeable implant with a 150-electrode stimulating array attached to a flexible intraocular coil. The coil connects to electronics that enable wireless energy reception and generate stimulation currents to activate the remaining viable neurons in the degenerated retina.22
A clinical evaluation of the IRIS II involved 10 successfully implanted patients. Efficacy assessments utilized the square grading scale of the Freiburg Vision test, with the device either activated or deactivated. Patients demonstrated statistically significant improvements in median distances for square localization and picture recognition tasks at 3- and 9-month post-implantation.22
Additionally, considerable motion detection enhancements were observed at 3 and 6 months. Visual field improvements were particularly notable, with 80% of participants developing a measurable visual field by 3 months, showing significant improvement in the median visual field area on Goldmann perimetry testing.22
In total, six serious adverse events were reported in four patients during the study period, with four events related to the surgical procedure and two potentially associated with both the device and method.
ENCELTO implant for macular telangiectasia
One of the most groundbreaking recent developments in retinal implant technology is the ENCELTO device (revakinagene taroretcel-lwey) for treating idiopathic macular telangiectasia type 2 (MacTel).
Unlike electronic prostheses, ENCELTO represents an innovative approach using allogeneic encapsulated cell-based gene therapy. This intravitreal implant contains 200,000 to 440,000 allogeneic retinal pigment epithelial cells genetically modified to express recombinant human ciliary neurotrophic factor (rhCNTF).23
The therapeutic mechanism underlying ENCELTO is particularly intriguing. Neurons endogenously produce ciliary neurotrophic factors and support glial cells in the retina. When provided exogenously, rhCNTF primarily targets Müller glia, triggering a cascade of signaling events that promote photoreceptor survival.23
Although this represents the prevailing theory regarding its mechanism of action, the complete biological impact of rhCNTF remains incompletely understood, suggesting potentially broader neuroprotective effects.24
Studies on the efficacy of ENCELTO
Clinical evaluation of ENCELTO has focused on its effect on the progression of ellipsoid zone (EZ) loss—a hyperreflective band visible on optical coherence tomography that corresponds to the ellipsoid portion of photoreceptor inner segments.
In MacTel, the loss of this zone has been closely correlated with functional visual deficits.25 Two clinical trials have assessed the efficacy of ENCELTO by measuring the rate of change in EZ loss area.26
Compared to sham treatment, the implant significantly reduced the rate of EZ area loss from baseline over 24 months. This significant finding led to FDA approval of ENCELTO, marking a breakthrough in therapeutic options for this previously untreatable progressive macular disorder.26
SUSVIMO implant for neovascular AMD
SUSVIMO (ranibizumab injection) is a VEGF inhibitor indicated for the treatment of nAMD in patients who have previously responded to at least two intravitreal injections of a VEGF inhibitor.
Approval of Susvimo was based on the phase 3 Archway study for eyes with previously treated nAMD. Susvimo is delivered through an ocular implant. The recommended dosage is 2mg continuously delivered with refills every 24 weeks.27
Supplemental treatment with 0.5mg intravitreal ranibizumab injection may be administered if necessary. This delivery system is unique and provides patients with a way to receive VEGF treatment without repeated retinal injections and the associated discomfort.27
Complications related to the Susvimo implant include:
- Endophthalmitis
- Rhegmatogenous retinal detachment
- Implant dislocation
- Septum dislodgement
- Vitreous hemorrhage
- Conjunctival retraction
- Conjunctival erosion
- Conjunctival bleb
- A decrease in visual acuity usually occurs over the first 2 months post-operatively
Note, it has been associated with a 3-fold higher rate of endophthalmitis compared to monthly intravitreal injections of ranibizumab. In clinical trials, 2% of patients receiving an implant experienced an episode of endophthalmitis.28 To minimize the risk of vitreous hemorrhage, it is recommended to discontinue antithrombotic medication before implant insertion.
Conclusions
Recent years have witnessed remarkable progress in vitreoretinal surgery, driven by innovations across instrumentation, robotics, and therapeutic implants. Miniaturized tools, advanced cutting technologies, and robotic assistance enhance surgical precision and efficiency, tackling previously challenging conditions.
Furthermore, novel retinal prostheses and drug delivery systems offer unprecedented hope for restoring vision and managing complex retinal diseases. These collective advancements signify a transformative era in retinal care, promising improved outcomes and expanded possibilities for patients worldwide.
