Detached Retina (Retinal Detachment)

Detached Retina

The retina is the light-sensitive tissue found at the posterior portion of the inner eye. It focuses the images that comes through the lens and converts them into electrical impulses which are sent to the brain via the optic nerve. It contains photoreceptor cells (cones and rods) contained in its most sensitive part, the macula. The retina has around seven million cones for detailed daytime vision and color perception; and about 75 – 150 million rods for the dim light (black and white) and peripheral visions. A light-sensitive ganglion cell helps in the reflexive responses to bright light.

The retina occupies around 65 percent of the eye’s inner surface. It has a thickness of about 0.2 mm and an area roughly the dimension of a silver dollar (1100mm²). Each retina contains approximately two hundred million neurons. It has a highly vascular layer (choroid) that supplies its oxygen and nutrients. The “red eye” sometimes noted in flash photos is attributable to the light reflected from this layer. It is red since the light’s shorter wavelengths are absorbed by the oxygenated blood.

Retinal Detachment

Retinal detachment occurs when the retina is separated from its supporting tissues. Early detachment is usually localized however if it is not treated immediately, the whole retina may break free and this could lead to blindness and loss of vision. A detached retina is considered a medical emergency.

There are three recognized types of retinal detachment

1. Rhegmatogenous retinal detachment happens as a result of a break in the retina allowing fluids in the vitreous space to enter the sub-retinal space causing the retina to be detached from the retinal pigment epithelium. This is the most widespread type of retinal detachment.
2. Exudative or Secondary retinal detachment is due to any vascular abnormalities, injury or inflammation beneath the retina. The fluid would still leak into the sub-retinal space even without any tear, break or hole.
3. Tractional retinal detachment happens when the sensory retina is pulled away by the fibrovascular tissue from the retinal pigment epithelium due to inflammation, neo-vascularization or injury.

A normal retina is transparent. An opaque or gray retina seen through slit-lamp examination with complete pupil dilation or opthalmoscopy would indicate retinal detachment.

The risk for retinal detachment to occur in a normal eye is approximately five in a hundred thousand per year. This eye condition is more common in middle age or elderly individuals (20,000 in 100,000 a year). This is also common in people with severe myopia since the retina is stretched out too thin. It would also occur more often in post-cataract surgery. Patients with proliferative retinopathy either due to diabetes or sickle cell anemia will most likely have tractional retinal detachment due to neo-vascularization.

Partially Detached Retina

In this condition, only a portion of the retina is detached from the retinal pigment epithelium. A special laser treatment, photocoagulation, is used to form a scar around the retinal hole border. This would fuse the retina with the supporting layer and prevent fluids from leaking in.

Detached Retina Causes

Retinal detachment frequently occurs with no underlying cause. But the following conditions could also cause the retina to be detached:

• Trauma
• Hemorrhage
• Diabetes
• exudates behind or in front of the retina
• Inflammatory disorders
• Sudden, extreme physical exertion
• Posterior vitreous detachment
• Myopic degeneration
• Aphakia (lack of crystalline lens)
• Congenital malformations
• Choroidal tumors

Detached Retina Symptoms

One of the most common symptoms of detached retina is a spreading “black curtain” or shadow across the vision field. As the minute blood vessels bleed in the vitreous layer, blurring of vision may occur.

Other retinal detachment symptoms that might be experienced are:

• Bright flashes of light most especially at the peripheral vision due to the pulling action of the vitreous field
• Floaters that might appear as strings, dark spots or specks across vision field due to condensations in the vitreous layer
• Partial blindness
• Loss of central vision

Since the retina does not have sensory nerves that could relay pain sensations, pain is not considered as one of the symptoms of detached retina.

Detached Retina Treatment

A detached retina can be treated in several ways. The type of treatment would depend on the severity, location and type of detachment.

Retinal tears or holes are sometimes treated to avoid their progression to a complete detachment by cryotherapy or laser therapy. Cryotherapy freezes the surrounding area of the tear to reattach the retina back while laser therapy would include the burning of tiny holes around the tear to solder the retina back to its place.

Pneumatic retinopexy is another way of reattaching the retina. The eye is anesthetized locally and the doctor would inject a tiny gas bubble inside the vitreous cavity. This bubble would press the retina against the posterior section of the eye. This treatment is most useful for detachments at the upper segment of the eye since gas would rise up. The bubble would be gradually absorbed after two to six weeks.

If partial retinal detachment is not treated it would be completely detached inside six months. The longer the retina is detached the more difficult it would be to reattach it since the vitreous layer would start to shrink and fibrous growths would start forming on the retina. Once this happens, the eye would continue to lose its visual capacity and eventually the person becomes blind.

Detached Retina Surgery

Retinal detachments are ophthalmologic emergencies and need to be treated immediately with surgery. Surgical procedure for this condition is done under general or local anesthesia, depending on the severity of the detachment. NPO is maintained at least 6 hours before the scheduled operation. Mydriatics are given prior to the surgical procedure to dilate the pupil.

• Scleral buckle surgery is the conventional treatment for a detached retina. In this procedure, the doctor will stitch silicone bands to the sclera. This would push the wall of the eye against the hole to seal it thus reducing or stopping the flow of fluid into the sub-retinal space and reattaching the retina. Laser or freezing is then done to close the hole. Oftentimes, the fluid is also drained from the space.
• Vitrectomy entails the removal of the vitreous layer then the eye is filled with silicon oil (more common) or C₃F₈ or SF6 gas. The advantages of this procedure are that the gas will be absorbed after two to eight weeks and the absence of a myopic shift but unfortunately, it would also lead to a development of cataract in the affected eye.

Detached Retina Surgery Recovery

Over 85-90% of the retinal detachment cases are successfully treated with just one operation while the remaining cases would require over two operations. The patients would slowly recover their vision within a few weeks but visual acuity might not be as fine before the detachment. The visual acuity would actually depend on the location of the detachment. If the macula is not involved then the vision might be quite good. Involvement of the macula for less than a week would improve the vision but not 20/20. If the macula was separated for a longer period then vision is restored but might be impaired, most of the time at 20/200 – the cutoff point for legal blindness. The patient may need to wear an eye patch after the operation to prevent strain on the operated eye.

Detached Retina Surgery Complications

Possible complications of the surgery would include:

• New holes formed
• Bruises around the eye
• Hemorrhage inside of the eye
• Glaucoma
• Cataract
• Diplopia
• Medication allergy
• Ptosis
• Itching and swelling
• Sympathetic opthalmia
• Infection
• Immune reaction that would affect the unoperated eye (extremely rare)

Detached Retina Surgery Time and Cost

The need to stay in the hospital would depend on the type of surgery that will be done. Usually, a patient stays a day or two. Total cost of operation would be little bit costly depending on the area you belong.

References:

http://www.nlm.nih.gov/medlineplus/ency/article/001027.htm

http://emedicine.medscape.com/article/798501-overview

http://www.nhs.uk/conditions/retinal-detachment/Pages/Introduction.aspx