August 5, 2013
Know Your Diseases

What is retina?

Retina is innermost light sensitive layer of eyeball similar to a film of the camera. Rays of light enter the eye and are focused on the retina by the lens. The retina produces a picture, which is sent along the optic nerve for the brain to interpret. Considering about structure, Retina is multi-layered thin sheet of neural tissue. The inner layers of retina known as neurosensory layer is loosely attached to the outermost layer Retinal pigment epithelium (RPE). Its outer layers receive its nourishment through the adjacent outer layer i.e. choroid through diffusion.

What is retinal detachment (RD)?

Separation of inner neurosensory layer of retina from outermost retinal pigment epithelium is called as retinal detachment. Due to separation of neurosensory layer the nourishment of this layer is compromised(Fig-1).

Fig.1: Retinal Detachment

What are the different types of retinal detachment?

Depending upon the cause there are three types of retinal detachment.

Rhegmatogenous retinal detachment: This is the most common type of RDcaused by break(Fig-2) in the retina which allows the fluid to get in between the neural layer & retinal pigment epithelium layer and separation of the neural layer from RPE layer & causing RD.

Fig.-2: Rhegmatogenous Retinal Detachment

Tractional retinal detachment: This type of RD is caused by the contraction of fibrous or scar tissue present on the surface of retina resulting in separation of neurosensory layer from RPE layer. Most common cause of this type of RD is Diabetic retinopathy.

Exudative retinal detachment(Fig-3): This type of retinal detachment is caused by the diseases of retina and choroid like inflammatory, neoplastic, or traumatic diseases which usually results in the leakage of fluid in between the RPE layer & neurosensory layer.

Fig–3: Exudative Retinal Detachment

Who are at risk for retinal detachment?

Although retinal detachment can occur in any person of any age but there are certain risk factors which can make a person more prone for the development of RD. Rhegmatogenous RD is most common RD and following persons are at risk  for its development who

  • Are extremely nearsighted (myopic)
  • Have had a retinal detachment in the other eye
  • Have a family history of retinal detachment
  • Have had cataract surgery without IOL implantation
  • Have other peripheral retinal degeneration or disorders, such as Lattice Degeneration, White without Pressure, Retinoschisis, Degenerative Myopia, or
  • Have had an eye injury

Why Retina breaks?

Most of the eye ball is filled with a jelly like structure called vitreous which is present in between lens and retina. Vitreous is mainly composed of water and proteinacous fibre like structures and is loosely attached to the retina except some points where it is firmly attached. In childhood, vitreous is well formed jelly (except certain diseased conditions), but with growing age the fibres starts to get clumped and because of aging, in old age most of the vitreous converted to liquid state and starts shrinking. The well form long proteinaceous fibrils of childhood become small fibre clumps suspending in liquid vitreous. This condition is known as vitreous syneresis. Vitreous syneresis causes vitreous to shrink & it starts getting detached from retina known as posterior vitreous detachment(PVD), but at places where it is firmly attached to retina it causes a tractional force upon the retina which results in tear in retina. Depending upon amount of traction, size of tear may vary from small horse shoe shaped tear to giant retinal tear. The liquefied vitreous enters through this tear & separates the neurosensory retina from the RPE layer. Certain disease condition like various vitreous degenerative condition, high myopia, uveitis, retinoschisis, lattice degeneration, promotes vitreous syneresis & weakening of retina leading to tear in retina.

There are certain other holes which occur in thin retina called atrophic holes.

What are the signs& symptoms of Rhegmatogenous Retinal detachment?

Retinal detachment usually causes sudden loss of vision if macula involves. It appears like a curtain coming over the field of vision. If macula is not involved then increased amount of floaters and loss of vision in the respective field may be noted.

Is there any early symptom of Retinal detachment?

Yes, sometimes increased flashes and floaters may occur in early retinal detachment. So any increase in flashes & floaters call for immediate retina check up by vitreo-retinal surgeon.

Is there any prevention for Retinal detachment?

The persons who are at risk of retinal detachment should be under regular check up with a vitreo retinal surgeon to look for the horse shoe tear or other retinal degenerations predisposing to retinal detachment. If any tear or degeneration prone to tear or retinal detachment found, that should be barraged with laser treatment. . Laser barrage is similar to welding process and in this procedure multiple laser burns were placed surrounding the tear on normal retina to create a firm adhesion between retina and its bed so that detachment not proceed further.

How retinal detachment is managed?

Management of retinal detachment is complex multistep procedure and it should be individualised. Where exudative retinal detachment is mostly managed with medical treatment,Rhegmatogenous & tractional retinal detachment almost always need surgery. Rhegmatogenous retinal detachmentis a surgical emergency and it must be managed urgently otherwise visual recovery will be less than expectation.A small retinaldetachment with minimal sub retinal fluid present inferiorly can be managed with laser barrage. A large retinal detachment can only be treated with surgery. There are two way to attach the detached retina in Rhegmatogenous retina depending upon site of break & other factors.

  1. Scleral buckle in this procedure, a tiny synthetic band, is attached to the outside of the eyeball to gently push the wall of the eye against the detached retina to relieve the traction and keep the retina attached.
  2. Vitrectomy in this procedure the retina is settled through inside the eyeball. In this procedure the vitreous is removed and retina attached with the help of silicon oil or non expansile gas as a tamponading agent in vitreous cavity. The gas is absorbed by 4 to 6 weeks by itself and the vitreous cavity is filled with fluid secreted by inner eye coats. If the retina is attached with the help of silicon oil, the oil has to removed after 6 month by a minor surgical procedure.

Surgery has been done. Now what I have to do?

After Vitrectomy either silicon oil or nonexpansile gas has been used to substitute the vitreous and tamponading the break. So, for complete attachment the retina needs constant support to remain in contact with RPE Layer. As the eyeball is bowl like structure and the retina is posterior wall of eyeball, and the retina needs constant pressure from oil or gas head should be kept down horizontal to the surface because oil and gas are lighter than water and tends to float on water surface. Head down position allows the oil and gas to tamponade the retina by keeping the oil or gas bubble above the water surface. This head down position should be maintained minimum 10-12 hours for at least 2 weeks but the initial postoperative period is very crucial.

What are the possibilities of getting vision after surgery?

With modern therapy, over 90 percent of those with a retinal detachment can be successfully treated, although sometimes (approx. 10% cases) a second treatment is needed. However, the visual outcome is not always predictable. The final visual result may not be known for up to several months following surgery. Even under the best of circumstances, and even after multiple attempts at repair, treatment sometimes fails and vision may eventually be lost.Visual results are best if the retinal detachment is repaired before the macula (the center of the retina responsible for fine, detailed vision) detaches. That is why it is important to contact a vitreo retinal surgeon immediately if you see a sudden or gradual increase in the number of floaters and/or light flashes, or a dark curtain over the field of vision.

What are the complications of retinal detachment surgeries?

Like any other surgery retinal detachment surgery has also its own complications. Long term retention of silicon oil in vitreous cavity may cause cataract formation or rapid progression of pre-existing cataract. Silicon oil may cause increase in in intra ocular pressure also. Removal of silicon oil may lead to recurrent retinal detachment. Scleral Buckle surgeries may be complicated by increase in astigmatism, increase in Myopia, buckle infection and buckle extrusion.