Retina Note · Retinal Detachment Surgery · Part 2
Principles of Retinal Detachment Surgery
Retinopexy, internal tamponade, scleral buckling and pneumatic retinopexy
Once the retina has been flattened and traction relieved, surgery must create a durable seal around the retinal break and maintain break closure long enough for chorioretinal adhesion to develop. This is achieved through retinopexy, internal tamponade or external buckle support.
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What Retinopexy Achieves
Retinopexy creates a controlled inflammatory response around a retinal break, followed by adhesion between the neurosensory retina, retinal pigment epithelium and underlying choroid.
Retinopexy Is Not Tamponade
These two steps perform different functions:
Retinopexy
Creates the chorioretinal reaction that will eventually surround and isolate the retinal break.
Tamponade or buckle support
Temporarily supports the break and limits further passage of fluid through it while the adhesion strengthens.
Laser Photocoagulation and Cryotherapy
The two principal methods are:
| Feature | Laser photocoagulation | Cryotherapy |
|---|---|---|
| Mechanism | Controlled thermal injury produced by absorbed laser energy | Controlled tissue freezing using a trans-scleral cryoprobe |
| Common use | Endolaser during pars plana vitrectomy or laser around accessible retinal breaks | Very anterior breaks and retinal breaks treated during scleral-buckle surgery |
| Visualisation | Requires a sufficiently clear view and access to the retinal break | Can be applied externally while the break is localised indirectly |
| Tissue response | Generally produces earlier strengthening of adhesion with less external inflammation | Produces a more marked inflammatory response and blood–retinal barrier disruption |
Neither technique is universally superior. The choice depends on the location of the break, visibility, surgical approach and surgeon preference. Comparative clinical evidence has not demonstrated a clear difference in anatomical success when either method is appropriately used during PPV for RRD. [1]
Internal Tamponade
Internal tamponade may be provided by:
- air;
- expansile gas;
- silicone oil.
A tamponading agent does not exert equal pressure over the entire retinal surface. Instead, its principal effect is to provide contact over the region positioned uppermost and prevent liquefied vitreous or aqueous fluid from passing through the treated break.
The effectiveness of tamponade therefore depends on:
- the location of the retinal break;
- the size of the bubble;
- head and eye position;
- the duration of support required;
- the presence of PVR;
- the patient’s ability to follow positioning instructions.
Air and Expansile Gases
Air provides the shortest period of internal support. Fluorinated gases expand after injection when used in pure form and persist longer within the vitreous cavity.
In vitreoretinal surgery, they are therefore commonly diluted with air to produce approximately non-expansile mixtures.
| Agent | Commonly taught non-expansile concentration | Approximate expansion of pure gas | Approximate intraocular persistence |
|---|---|---|---|
| Air | 100% | Does not expand | About 5–7 days |
| SF6 | 20% | Approximately doubles in volume | About 2–3 weeks |
| C2F6 | 16% | Intermediate expansion | About 4–5 weeks |
| C3F8 | 14% | Approximately quadruples in volume | About 6–8 weeks |
These are conventionally taught values rather than guarantees. Persistence varies with gas concentration, injected volume, completeness of gas fill, axial length and surgical factors. [2]
Why Gas Concentration Matters
Pure expansile gas absorbs nitrogen and other gases from the surrounding tissues faster than the injected gas initially leaves the eye. The bubble therefore enlarges before it begins to contract.
Diluting the gas with air limits this postoperative expansion.
However, a “non-expansile” concentration does not guarantee that the intraocular pressure will remain normal. Pressure elevation may still occur because of:
- an excessive gas fill;
- an incorrectly prepared concentration;
- postoperative inflammation;
- pupillary block;
- angle closure;
- impaired aqueous outflow.
Longer-acting gas is not automatically better. The surgeon selects the agent according to the duration and location of support required.
Choosing Between Air, SF6 and C3F8
Air
Provides short-duration support and is absorbed relatively quickly.
SF6
Provides a shorter-acting expansile gas tamponade. It may be chosen when support is required for several weeks but rapid visual rehabilitation is desirable.
C3F8
Provides a longer duration of tamponade and may be useful when prolonged break support is required.
C2F6
C2F6 has an intermediate duration but is used less commonly in many contemporary practices.
Gas selection also affects how long the patient experiences blurred vision and must avoid air travel and nitrous oxide.
Gas Safety
An intraocular gas bubble may expand dangerously when ambient pressure falls or when nitrous oxide diffuses into the eye.
Patients must be clearly advised:
- Do not travel by air while gas remains in the eye.
- Avoid significant ascent to high altitude unless specifically cleared by the retinal surgeon.
- Do not scuba dive while the bubble remains.
- Nitrous oxide anaesthesia is contraindicated.
- Inform every doctor, dentist and anaesthetist that an intraocular gas bubble is present.
- Vision will remain blurred while the bubble obstructs the visual axis.
- Seek urgent assessment for severe ocular pain, headache, nausea or sudden further visual loss.
Nitrous oxide rapidly enters the gas bubble and can cause marked bubble expansion, acute intraocular-pressure elevation and irreversible visual loss. [3]
Silicone Oil
Silicone oil provides longer-term internal tamponade and remains within the eye until it is surgically removed or deliberately retained.
It is commonly considered in selected eyes with:
- significant proliferative vitreoretinopathy;
- complex or recurrent retinal detachment;
- giant retinal tears;
- extensive retinectomy;
- trauma;
- a need for prolonged internal support;
- circumstances in which gas-related travel restrictions or prolonged visual obstruction would create major difficulties.
Silicone oil is not automatically superior to gas. In the landmark Silicone Study, silicone oil and long-acting C3F8 gas produced broadly comparable results in eyes with severe PVR, whereas silicone oil performed better than short-acting SF6 in several important outcomes. [4]
The poorer prognosis often observed in silicone-oil-filled eyes largely reflects the complexity of the retinal detachment for which oil was selected, rather than proving that silicone oil itself caused the poor outcome.
Silicone-Oil Prognosis: Historical Evidence
The lecture quotes visual-prognosis figures based on whether silicone oil was required. Those exact percentages should not be presented as a universal comparison.
The closest major historical evidence is the Silicone Study, which enrolled eyes with severe PVR and compared silicone oil with intraocular gas. Its principal visual endpoint was 5/200 or better, not 20/400. [4]
The final visual prognosis depends more directly on:
- the condition of the macula;
- the severity of PVR;
- retinal shortening or retinectomy;
- previous failed surgery;
- optic-nerve and retinal damage;
- postoperative complications.
Optical Effects of Silicone Oil
Silicone oil has a higher refractive index than aqueous fluid and vitreous. Its optical effect depends on the lens status and the curvature of the oil interface.
| Lens status | Typical refractive effect |
|---|---|
| Phakic | Hyperopic shift |
| Pseudophakic | Usually a hyperopic shift, influenced by IOL design and position |
| Aphakic | Marked myopic shift |
Classic clinical studies reported refractive changes of approximately 5–9 dioptres in silicone-oil-filled phakic or aphakic eyes, although the direction differs: hyperopic in phakia and myopic in aphakia. [5]
The exact change in an individual eye is not fixed and depends on:
- axial length;
- lens or IOL status;
- silicone-oil fill;
- posture;
- curvature of the oil interface.
Silicone-Oil Complications
- cataract progression;
- raised intraocular pressure;
- pupillary block;
- silicone-oil emulsification;
- migration of oil into the anterior chamber;
- corneal endothelial damage and keratopathy;
- inflammation;
- recurrent retinal detachment after oil removal;
- unexplained visual loss in selected eyes.
Some complications relate to the underlying retinal disease, while others arise from prolonged oil contact, emulsification or altered aqueous flow.
Aphakia and Pupillary Block
In an aphakic eye, silicone oil can move through the pupil into the anterior chamber. Because standard silicone oil floats, it may obstruct the pupil superiorly.
Aqueous then accumulates behind the iris, producing:
↓
Forward bowing of the iris — iris bombé
↓
Secondary angle closure and raised intraocular pressure
An inferior peripheral iridectomy, classically at six o’clock, creates an alternative route for aqueous to pass from the posterior chamber into the anterior chamber beneath the floating oil. [6]
A patent iridectomy reduces the risk but does not make pupillary block impossible.
Postoperative Positioning
Postoperative positioning is prescribed according to:
- the position of the retinal break;
- the tamponading agent;
- the operation performed;
- the amount of gas or oil;
- the surgeon’s intended area of contact.
The goal is to position the bubble against the treated break—not automatically against the macula.
The Steamroller Manoeuvre
The steamroller manoeuvre is a positioning technique used in selected bullous superior detachments to reduce the risk of subretinal fluid shifting toward the macula during pneumatic retinopexy.
The basic concept is:
- gas is injected;
- the patient is initially positioned so the bubble lies posteriorly;
- the head is then rotated slowly along the meridian toward the retinal break;
- the bubble progressively displaces subretinal fluid toward the break rather than toward the macula.
The exact sequence of gas injection, positioning and retinopexy varies with technique. Cryotherapy does not universally have to be performed after the manoeuvre.
How a Scleral Buckle Works
A scleral buckle is an external implant placed against the sclera to create a controlled inward indentation of the eyewall.
This indentation:
- brings the RPE and choroid closer to the detached retina;
- supports the retinal break externally;
- changes the direction and magnitude of traction acting across the break;
- reduces the passage of fluid through the break.
The buckle does not reattach the retina merely by globally reducing the circumference of the vitreous cavity. Its main purpose is to provide accurately positioned support beneath the causative break.
Common Buckle Configurations
| Configuration | Basic principle |
|---|---|
| Radial buckle | Placed perpendicular to the limbus and supports a localised break along its anterior–posterior extent |
| Segmental circumferential buckle | Supports a limited arc of peripheral retina along the circumference of the globe |
| Encircling band | Provides 360° support around the globe, commonly near the vitreous base |
| Combined buckle | Uses an encircling band together with a local radial or circumferential element |
Common implant materials include:
- solid silicone tyres;
- silicone sponges;
- narrow silicone bands.
The ends of an encircling band may be joined using a silicone sleeve.
When Scleral Buckling May Be Favoured
Scleral buckling remains particularly useful in selected eyes with:
- young age;
- phakia;
- a relatively formed vitreous;
- anterior retinal breaks;
- retinal dialysis;
- a limited and clearly localised break pattern;
- absence of significant PVR;
- a desire to avoid vitrectomy-associated cataract progression.
The buckle may be used alone or combined with PPV.
In phakic primary RRD, scleral buckling can achieve excellent anatomical and visual results when the detachment configuration is suitable. PPV remains more commonly favoured in many pseudophakic and complex detachments. [7]
Pneumatic Retinopexy
Pneumatic retinopexy is a minimally invasive method of repairing selected rhegmatogenous retinal detachments using:
- retinopexy around the retinal break;
- an intravitreal gas bubble;
- postoperative positioning to bring the bubble against the break.
As the gas occludes the break, further fluid entry is reduced and the RPE gradually absorbs the remaining subretinal fluid.
Retinopexy may be performed with cryotherapy or laser. The exact timing relative to gas injection varies with technique and clinical circumstances.
Classic Selection Criteria
Traditional favourable features include:
- a single retinal break or a small group of breaks within approximately one clock hour;
- break location in the superior retina;
- clear media permitting a complete retinal examination;
- no significant PVR;
- ability to maintain the required position;
- reliable and prompt follow-up.
Small additional inferior breaks may alter suitability because the superior gas bubble may not support them.
Pneumatic Retinopexy Versus PPV
Pneumatic retinopexy generally has a lower primary single-procedure reattachment rate than PPV, but selected patients may achieve excellent functional results.
In the PIVOT randomized trial, appropriately selected eyes treated with pneumatic retinopexy demonstrated:
- better visual acuity during follow-up;
- less vertical metamorphopsia;
- less retinal displacement;
- less cataract progression;
But PPV produced a higher primary anatomical reattachment rate. [8]
This is an important example of the distinction between:
Primary anatomical success
Quality of functional visual recovery
Pneumatic retinopexy should therefore not be judged solely by whether a second procedure is occasionally required.
Anatomical Success Is Not Visual Success
Outcomes after retinal-detachment repair should be separated into three endpoints:
Primary anatomical success
The retina remains attached after one operation.
Final anatomical success
The retina remains attached after one or more procedures.
Functional visual success
The patient regains useful visual acuity and visual quality.
Final anatomical reattachment rates can be high even when more than one procedure is required. Visual recovery may remain limited despite successful reattachment if the macula or photoreceptors have sustained significant damage.
Factors Affecting Visual Prognosis
Important prognostic factors include:
- macula-on or macula-off status;
- duration of macular detachment;
- presenting visual acuity;
- severity of PVR;
- chronicity of the detachment;
- extent and complexity of retinal involvement;
- giant retinal tear or retinal shortening;
- recurrent detachment;
- previous vitreoretinal surgery;
- macular folds or retinal displacement;
- postoperative complications.
The presence of silicone oil should not be interpreted in isolation as the cause of poor prognosis. It is often a marker that the original detachment was complex.
Part 2 Summary
- Retinopexy creates chorioretinal adhesion; tamponade supports the break while adhesion develops.
- The commonly taught non-expansile gas concentrations are 20% SF6, 16% C2F6 and 14% C3F8 .
- Intraocular gas requires strict counselling regarding air travel, altitude, diving and nitrous oxide.
- Silicone oil provides prolonged support in selected complex detachments but usually requires later surgical management.
- Silicone oil typically causes a hyperopic shift in phakic eyes and a myopic shift in aphakic eyes.
- A scleral buckle supports the retinal break by producing a controlled inward indentation of the eyewall.
- Pneumatic retinopexy can provide excellent functional outcomes in properly selected and reliably followed patients.
- Anatomical reattachment and final visual recovery are related but distinct outcomes.
References
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Veckeneer M, van Overdam K, Bouwens D, et al. Randomized clinical trial of cryotherapy versus laser photocoagulation for retinopexy in conventional retinal detachment surgery. American Journal of Ophthalmology. 2001;132(3):343–347. doi:10.1016/S0002-9394(01)01026-1
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Kontos A, Tee J, Stuart A, Shalchi Z, Williamson TH. Duration of intraocular gases following vitreoretinal surgery. Graefe’s Archive for Clinical and Experimental Ophthalmology. 2017;255(2):231–236. doi:10.1007/s00417-016-3438-3
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Schöneberger V, Seider MI, et al. Outcomes of short- versus long-acting gas tamponades in vitrectomy for rhegmatogenous retinal detachment. International Journal of Retina and Vitreous. 2024;10:11. doi:10.1186/s40942-024-00530-y
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Yang YF, Herbert L, Rüschen H, Cooling RJ. Nitrous oxide anaesthesia in the presence of intraocular gas can cause irreversible blindness. BMJ. 2002;325(7363):532–533. doi:10.1136/bmj.325.7363.532
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McCuen BW II, Azen SP, Boone DC, et al.; Silicone Study Group. Vitrectomy with silicone oil or perfluoropropane gas in eyes with severe proliferative vitreoretinopathy: results of a randomized clinical trial—Silicone Study Report 2. Archives of Ophthalmology. 1992;110(6):780–792. doi:10.1001/archopht.1992.01080180052028
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Abrams GW, Azen SP, McCuen BW II, et al.; Silicone Study Group. Vitrectomy with silicone oil or long-acting gas in eyes with severe proliferative vitreoretinopathy: results of additional and long-term follow-up—Silicone Study Report 11. Archives of Ophthalmology. 1997;115(3):335–344. doi:10.1001/archopht.1997.01100150337005
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Stefánsson E, Anderson MM Jr, Landers MB III, Tiedeman JS, McCuen BW II. Refractive changes from use of silicone oil in vitreous surgery. Retina. 1988;8(1):20–23. No DOI has been reliably indexed for this article.
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Beekhuis WH, Ando F, Zivojnović R, Mertens DAE, Peperkamp E. Basal iridectomy at 6 o’clock in the aphakic eye treated with silicone oil: prevention of keratopathy and secondary glaucoma. British Journal of Ophthalmology. 1987;71(3):197–200. doi:10.1136/bjo.71.3.197
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Heimann H, Bartz-Schmidt KU, Bornfeld N, et al.; SPR Study Group. Scleral buckling versus primary vitrectomy in rhegmatogenous retinal detachment: a prospective randomized multicenter clinical study. Ophthalmology. 2007;114(12):2142–2154. doi:10.1016/j.ophtha.2007.09.013
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Hillier RJ, Felfeli T, Berger AR, et al. The Pneumatic Retinopexy versus Vitrectomy for the Management of Primary Rhegmatogenous Retinal Detachment Outcomes Randomized Trial (PIVOT). Ophthalmology. 2019;126(4):531–539. doi:10.1016/j.ophtha.2018.11.014
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Popovic MM, Muni RH, Nichani P, Kertes PJ. Pars plana vitrectomy, scleral buckle, and pneumatic retinopexy for the management of rhegmatogenous retinal detachment: a meta-analysis. Survey of Ophthalmology. 2022;67(1):184–196. doi:10.1016/j.survophthal.2021.05.008
