Tuesday, 26 July 2011

What is Retinal Detachment

Published in City Times

What is Retinal Detachment

Approximately one out of 15000 individuals has a retinal detachment (RD) in a given year. The peak incidence of RD occurs between the ages of 50 and 70 years, reflecting the high frequency of PVD and cataract surgery. Further, 10% - 15% of symptomatic PVD will have a retinal tear which increases to 70% if associated with vitreous haemorrhage. Myopia RDs are the most common between the ages of 25 and 45 years and more often of traumatic origin, predominantly in males (60%). Also, retinal detachment in the second eye of an affected individual has been estimated to be about 15%, reveals Dr.Samir Jamal, Specialist Ophthalmic Surgeon, Belhoul European Hospital, Dubai.

What exactly is retinal detachment (RD) and how does it happen?
The retina is a layer of neurosensory and pigment tissue that lines the back, inside wall of the eyes. The retina forms the utmost membrane of the posterior segment of the eye. When the rays of light enter the eye, similar to a camera mechanism, they are focused on the retina by the cornea and lens. The retina reacts in the sense that the light receptive nerve cells of which the retina is made, generate a nerve impulse on being exposed to the light. The retina then sends these nerve impulses along the optic nerve to the brain which in turn interprets the images. However, if the retina is defective, vision is not possible. A retinal detachment is a separation of the retina from the back wall of the eye. When a retinal tear happens, liquid from the vitreous cavity may pass through the tear and detach the retina.

What are the causes of RD?
Causes may be classified into three types of detachments. The most common type (Rhegmategenous or Idiopathic or Spontaneous RD). This chiefly occurs when there is a break in the sensory layer of the retina, and fluid seeps underneath, causing the layers of the retina to separate. This is common in myopics, individuals who have undergone surgery for cataract or have experienced a serious eye injury resulting from contusions or penetrative injuries.

Exudative or serous or secondary RD occurs due to a leakage from under, or in the retina which creates exudates that detach the retina. There is no tear in this instance and the detachment usually happens due to underlying pathological conditions including tumours, inflammatory chorio-retinal disorder, connective tissue diseases, macular degenerations, etc.

Tractional RD occurs with a pulling mechanism whereby there is primarily neither a tear nor a hole in the retina. The pulling on the sensory retina is usually from fibrovascular tissue within the vitreous cavity. Proliferative vitreo retinopathy and Proliferative Diabetic Retinopathy are the common causes and because much of the blood supply to the retina is from the choroid. The separated retina becomes anoxic, hypofunctional and in prolonged RD, the photoreceptors will degenerate.

Who are the people at risk of RD?
Risk factors include: Myopia (50% of patients with idiopathic RD); individuals who have had previous cataract surgery (30%), people who suffer ocular trauma as in case of contusion from blunt injuries to the eye, individuals with lattice degeneration or peripheral retinal thinning, individuals with a family history of RD or retinal tears and indirectly through predisposition to myopia or peripheral retinal degenerations, people suffering from some systemic diseases such as Marfan’s Syndrome, ageing and those who have undergone Yag-laser capsulotomy. RD is believed to run in families.

What are the symptoms of RD and how early do they start manifesting?
Symptoms of an acute retinal tear include a sudden onset of floaters and debris (shower of black spots and cobwebs or tobacco dust), photopsia or flashes and sometimes blurred vision. The same symptoms can occur with an uncomplicated PVD flashes associated with vitreo-retinal traction which are typically of short duration, unlike the flashes encountered with migraine or other vascular disturbances. Once the RD has taken place, patients may additionally become aware of visual field loss perception of progressively enlarging dark curtain or shadow starting in the side (and eventually spreading to the centre), obscuring vision which is significantly impaired if the macula is involved.

Is it possible to have RD without being aware of it?
While these are the commonest symptoms of retinal detachment, “it should be emphasized that retinal detachment can still occur without any symptoms and there are people who get picked up for the condition on routine eye examination,” cautions Dr.Samir.

Patients with chronic, slowly progressive or “demarcated” detachments, usually in the inferior retina, may be asymptomatic. Retinal detachment can happen without the patient feeling any symptoms at all and it gets picked up on routine eye investigation. This usually happens because when the extreme periphery of the retina gets detached, and not the central retina; so the patient will not realize it since it presents no symptoms.

Can other eye conditions or other disorders mimic symptoms of RD?
Migraine sufferers see flashes. However, those having RD do not have headache which is associated with migraine. Floaters could also happen in other conditions causing bleeding into the eye due to diabetes without retinal detachment. It can occur as part of the ageing process, after cataract surgery or even if there is some inflammation and also choroidal effusion retinoschisis.

Once the process of RD sets in, how rapidly does it progress?
RD can be hastened and worsened by certain factors. Bouts of violent coughing or vomiting, lifting heavy weights, constipation, doing pull-ups and pushups may speed up the process.

How is RD diagnosed?
By conducting a complete examination of both eyes. Examining the uninvolved eye may provide clues to the underlying cause of RD in the afflicted eye. We start by checking the visual acuity, followed by the pupillary reflexes, eye pressure (tonometry), Slit Lamp Examination, through a detailed examination of the bottom of the eye with special lens after dilating the pupils to detect vitreous trouble (bleeding), the detached retina, the single or multiple retinal breaks, folds, undulation, etc.

If the retina cannot be seen properly because of unclear media (cloudiness of cornea, cataract, hemorrhage, etc), an ultrasonography can help diagnose the RD and differentiate the rhegmatogenous RD from other non-rhegmatogenous type which is very important to be determined in terms of therapeutic plan. Although this test is highly sensitive and specific for RD, it is not helpful in localizing the retinal breaks. At the end, a schematic drawing of the fundus is made.

What are the complications of untreated RD?
The extent of the detachment is directly proportional to the fluid accumulation and if left untreated, it can lead to cataract formation, glaucoma, and other eye disorders, including vision impairment and even total blindness and globe ashrinkage (atrophy) or to a lesser extent, Ectasia.

What is the treatment of RD and how what is its success rate?
Prognosis or success of treatment is inversely related to the degree of macular involvement and the length of time the retina has been detached and how early it has been diagnosed. Surgery is the only treatment for established RD. Photocoagulation or cryoapplication are the indicated methods to close all the retinal breaks before the stage of RD. The goal of each treatment is to relieve the retinal traction and to close retinal tears. The area surrounding the breaks is treated with cryotherapy (cold) or laser and the surgery usually consists of one or more of the following procedures:

Scleral Buckle or a silicone band is secured to the external surface of the sclera to counteract the forces pulling the retina away from the choroid.

Pneumatic Retinopaxy: An expanding gas bubble (perflkuorocarbon) is injected into the vitreous cavity and the patient is positioned so that the bubble closes the break, allowing for the resorption of the subretinal fluid. Laser or cryo is used to seal the breaks.

Vitreotomy is done to remove the formed vitreous gel as well as any scar tissue or blood that has accumulated.

Inflammatory RDs are usually treated medically. Anatomically, approximately 80% - 85% of primary RD can be successfully repaired and 92% of RD overall. Visual results following RD surgery are in large part determined by the preoperative visual acuity and the status of the macula. Overall, 55% of anatomical surgical successes will achieve at least 40% vision within six months of surgery. Less than 15% will be left with 5% vision or worse.

What are the complications from surgery?
Patients with retinal tear and/or RD, require careful follow-up to watch for the development of post operative complications and to monitor the status of the second eye. The most common cause of failed surgery is the development of proliferative vitreo retinopathy (PVR) which is characterized by the development of certain membranes which distort the retinal surface into fixed folds, and which could often reopen existing breaks or cause new ones to form. If this membrane develops, the prognosis is poor, especially in terms of visual outcome.

Significant complications other than the PVR include bleeding, new retinal break formation, post operative detachment, double vision, infection, high intraocular pressure and cataract, maculopathy, scleral explant exposure and choroidal effusion.

The treatment of retinal tears, compared to RD surgery, is less expensive, requires less rehabilitation, is technically less demanding and results in fewer complications and is much less likely to be associated with significant visual loss.

Can RD be prevented?
Certainly! By instructing high-risk patients to undergo periodic checkups. By avoiding violent sports and educating people about the nature and significance of such symptoms.


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