Macula -on Rhegmatogenous Retinal Detachment

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Macula-on rhegmatogenous retinal detachments require early intervention to prevent subretinal fluid from reaching the macula and reducing the visual acuity.

Introduction

Description

Rhegmatogenous retinal detachment is defined as separation of the neurosensory retina from the retinal pigment epithelium secondary to a ‘rhegma’ or break. The macula is the central 5.5mm circular area inside the temporal vascular arcades and contains the fovea in the central 1.5mm which is responsible for central vision.

Macula- or fovea-sparing (also dubbed macula-on) retinal detachment indicates that subretinal fluid has not affected central vision and that visual acuity remains at baseline.[1]

Macula. Image Courtesy: Madhuvanthi Mohan


Subretinal fluid under the macula indicates some degree of damage despite reattachment.

Macula is a significant factor in determining final visual outcomes and should be considered in the timing of surgical repair. There is higher probability of achieving better visual outcomes in macula-on rhegmatogenous retinal detachments . [1]

Fundus photo of the left eye of a superotemporal retinal detachment with 'Macula - on'. Image Courtesy: Sankara Nethralaya, Chennai

73% of macula- on retinal detachments have greater than 20/40 visual acuity after 2 months of surgery. [2] Hence, macula- on retinal detachments need early surgery.

Risk Factors for progression of macula-on to macula-off [3][4]

Retinal detachment progression occurs due to the shear forces on the retina by the ocular and head movements and gravity.

The following characteristics have a greater chance of progression to involve the macula :

•Superior especially superotemporal retinal detachments

•Greater degree of bullosity

•Subretinal fluid within 1 disc diameter of the fovea

•Larger or giant retinal tears

•Equatorial tears have a greater chance of progression than tears at the ora serrata

Symptoms

Flashes, floaters, a curtain like shadow over visual field

Visual acuity will be normal in cases of macula-on retinal detachment

Fundus examination

  • Configuration of the retinal detachment
  • Quadrant of RD
  • Bullosity
  • Involvement of macula
  • Retinal breaks
  • Type
  • Location
  • Number of breaks
  • Depressiblity of breaks
  • Presence of PVD
  • Presence of PVR changes
  • Chronicity of detachment

Diagnostic procedures

Optical coherence tomography can help rule out subclinical fluid involvement at the fovea

Pre-operative measures

It is imperative to counsel the patient about the importance of early surgery as macula on retinal detachments have better visual outcomes.

Urgent physician fitness needs to be obtained and surgery should be done as early as possible especially in superior bullous retinal detachments.

Other pre-operative steps to be taken are bed rest, bilateral patching of the eyes and positioning of the patient.

Bed rest and bilateral patching[5]

  • Bed rest helps in restricting forces related to head and ocular movements.
  • By positioning the globe with the retinal break in the most dependent position, alteration of the vitreous body is obtained such that there is vitreous occlusion of the breaks.
  • There is simple descent of retina due to gravity and passage of the subretinal fluid from the subretinal to the retrovitreal space via the retinal hole.
  • Large eye movements increase vitreous traction and detachment forces on the edge of the retinal hole, creating a subretinal vacuum and facilitating increased subretinal fluid.
  • Bilateral patching 24-48 hours before surgery decreases saccadic ocular movements and reduces inertial force induced by ocular movements thus decreasing the height of retinal detachment and preventing macula on retinal detachment from converting to macula off retinal detachment.
    Bilateral eye patching. Image Courtesy: Google images

Positioning [6]

  • The detached retina should be in the lower most position to address the force of gravity.
  • In superior retinal detachments, the patient should maintain a supine position with no pillows and with foot end raised ie the Trendelenburg position.
Trendelenburg position: patient is supine on the table with their head declined below their feet. Picture courtesy: Google images
  • In cases of inferior retinal detachments, an upright or sitting position is preferred.
  • For temporal and nasal retinal detachments:
Positioning for retinal detachments - temporal and nasal


Management

Depending on the extent of retinal detachment and location of retinal breaks, management can be non-surgical or surgical.

Treatment can be non-surgical or surgical

Delimiting laser photocoagulation[7]

•Delimiting laser photocoagulation can used in subclinical retinal detachments that extend at least 1 disc diameter from the nearest break and no more than 2 disc diameter posterior to equator with no visual field loss.

•It helps by forming a barrier to prevent further extension of subretinal fluid.

•It has the advantages of being less invasive, inexpensive and an outpatient procedure and is preferred in young patients with vitreous not liquified or when patient cannot be operated due to other reasons

•However, it is important to closely follow-up these patients.

Delimiting laser photocoagulation done in sublinical retinal detachment. Image Courtesy: Sankara Nethralaya, Chennai


Pneumatic Retinopexy [8]

Pneumatic Retinopexy is the injection of gas bubble into the vitreous cavity and serves as an alternative to surgical intervention in certain cases of retinal detachments.

The common indications include:

• Retinal break(s) within the superior 8 clock hours (8 to 4 o’clock)

•Single or multiple breaks within 1 clock hour

•No or minimal media opacity

•Patient should be able to maintain positioning for 5-8 days after procedure

Steam Roller Technique

The steam roller technique is important for preventing iatrogenic macular detachment while doing pneumatic retinopexy.

If there is bullous subretinal fluid which is almost extending to the macula, placement of bubble against the bullous detachment may cause a macular detachment (A).

This is avoided by maintaining a face down position (B) which enables the bubble to traverse the attached retina enroute to the macula. This frequently causes subretinal fluid to pass through the break into the vitreous (arrow)

Gradually over 10 mins, the head position is changed to bring the retinal break to the upper most position (C).

The bubble then rolls towards the break pushing the subretinal fluid away from the macula back into the vitreous and flattening the retina (D).

Steam Roller Technique. Image Courtesy: Madhuvanthi Mohan

Choice of surgical procedure

The macula status does not necessarily play a role in choice of surgery.

The surgical options are scleral buckling or vitrectomy and this depends on other indications. But the goal in either surgery should be to keep the macula attached intra-operatively also and certain precautions can help attain this goal.

Scleral buckling

The aim in scleral buckling surgery for macula on retinal detachment is to prevent subretinal fluid from tracking under the macula.

The following steps can be followed to prevent the same.

•Once buckle is placed initially, the sutures should not be tightened too much

•A thorough examination with an indirect ophthalmoscope should be done after placing the buckle to assess the break location and size

•Subretinal fluid drainage should be done with loosened stay sutures

•Gentle maneuvering of the globe to milk the eyeball with bud from posterior to anterior movements can be done

•Air / gas injection should be done if subretinal fluid persists at macula or fishmouthing is present

Vitrectomy with tamponading agents [9]

If vitrectomy is the preferred surgical procedure, certain modifications can be made to prevent conversion of macula on to macula off retinal detachment intra-operatively.

•Valved cannulas should be used to avoid undue vitreous escape from the port and thereby pulling the detached retina. It helps to prevent intraocular pressure fluctuations during surgery and avoid turbulence of the fluidics thus reducing the retinal dynamics.

•If the retinal detachment is bullous, in an eye with a large open break, select an infusion site that allows you to avoid infusing fluid through the break under the retina which can make the detachment more bullous and causing extension into the macula.

•If the plan is to drain fluid through a primary break, a sclerotomy site in the meridian of the tear can be selected for easier access.

•Avoid instruments exiting and entering the eye frequently during vitrectomy.

•Low suction and high cut rate is preferred to not cause any linear extension of retinal breaks.

•Once you clear vitreous surrounding the primary break, drain subretinal fluid under fluid infusion (fluid-fluid exchange ) and flatten the retina to prevent extension of detachment. Fluid aspiration often flattens the retina and reduces the risk of extension of retinal detachment.

•In selected cases, perfluorocarbon placed over the posterior pole helps in preventing subfoveal subretinal fluid migration and helps keeping the macula on during surgery. It pushes and displaces the subretinal fluid anteriorly and also helps in keeping the posterior pole flat and attached while doing vitreous base shaving.

Use of PFCL can help keeping the posterior polar flat and prevent subfoveal fluid migration. Image Courtesy: Madhuvanthi Mohan


•Complete fluid gas exchange can displace the subretinal fluid from the periphery to the posterior pole thus detaching the macula . This can be prevented with the follow steps.

  • Draining via a relatively posterior iatrogenic drainage retinotomy
  • Air exchange with a large bubble of perfluorocarbon in situ. The perfluorocarbon displaces the subretinal fluid anteriorly and the air displaces the subretinal fluid posteriorly. The doughnut of subretinal fluid is at the interface. With indentation and massage, the subretinal fluid can be evacuated more completely via a peripheral break.
  • Do not perform a complete fluid air exchange. The bubble only needs to be large enough to close the retinal break. Slightly expansile concentration of gas can also be used.
How fluid-air exchange works. Image Courtesy: Madhuvanthi Mohan

•During the endolaser step, complete lasering the break first and then the other areas.

•Choice of tamponade is not based on macula status and should be individualized based on location and characteristics of retinal detachment.

Post-operative precautions[10]

  • If only a small amount of subretinal fluid is present, the patient should be instructed to maintain face down position for about 4–6 hours immediately after the surgery.
  • By this time, the subretinal fluid should be reabsorbed without causing a retinal fold.
  • If a substantial amount of subretinal fluid persists and cannot be removed, it is helpful to leave some preretinal fluid behind (i.e. not completing a full fluid-air exchange) and instructing the patient to keep a supine position for the first hours after the surgery.

Conclusion

  • Macula on retinal detachments especially superior bullous ones should be treated as early as possible as they have better visual prognosis.
  • Pre-operative positioning helps to prevent conversion of macula on retinal detachment to macula off.
  • Proper techniques should be followed intra-operatively to avoid extension of the detachment to the macula.

References

  1. 1.0 1.1 Mahmoudi S, Almony A. Macula-Sparing Rhegmatogenous Retinal Detachment: Is Emergent Surgery Necessary?. J Ophthalmic Vis Res. 2016;11(1):100-107
  2. Wykoff CC, Smiddy WE, Mathen T, Schwartz SG, Flynn HW Jr, Shi W. Fovea-sparing retinal detachments: time to surgery and visual outcomes. Am J Ophthalmol. 2010 Aug;150(2):205-210.e2.
  3. Retinal Detachment: Priniciples and Practice By Daniel A. Brinton M.D., Charles P. Wilkinson M.D.
  4. Ho SF, Fitt A, Frimpong-Ansah K, Benson MT. The management of primary rhegmatogenous retinal detachment not involving the fovea. Eye (Lond). 2006 Sep;20(9):1049-53
  5. Foster WJ. Bilateral patching in retinal detachment: fluid mechanics and retinal "settling". Invest Ophthalmol Vis Sci. 2011;52(8):5437-5440. Published 2011 Jul 20.
  6. de Jong JH, Vigueras-Guillén JP, Simon TC, Timman R, Peto T, Vermeer KA, van Meurs JC. Preoperative Posturing of Patients with Macula-On Retinal Detachment Reduces Progression Toward the Fovea. Ophthalmology. 2017 Oct;124(10):1510-1522.
  7. Lin J, Sridhar J, Flynn HW Jr. Long-term stability of laser-demarcated macula-sparing rhegmatogenous retinal detachments. Clin Ophthalmol. 2019;13:1039-1041. Published 2019 Jun 19.
  8. Retina E-Book: 3 Volume Set By Charles P. Wilkinson, David R. Hinton, SriniVas R. Sadda, Peter Wiedemann, Stephen J. Ryan
  9. uhn F. Vitreoretinal Surgery: Strategies and tactics. Springer 2016
  10. Heimann H, Bopp S: Retinal Folds following Retinal Detachment Surgery. Ophthalmologica 2011;226(suppl 1):18-26.
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