Retinal Detachment

Retinal detachment (RD) refers to a separation of the inner sensory retina and the outer retinal pigment epithelium (RPE).¹ The space between them becomes filled with subretinal fluid which may come from a number of sources (not all of which are known). RD broadly falls into two categories: rhegmatogenous and non-rhegmatogenous.

• Rhegmatogenous RD This where the sensory retina detaches due to a retinal break: it may get torn as a result of vitreous traction or chronic retinal atrophy may result in a hole. This is the most common form of RD.
• Non-rhegmatogenous RD There are two types of non-rhegmatogenous RD:
  • Tractional: the vitreous contracts (e.g. due to proliferative diabetic retinopathy) and pulls the sensory retina away with it.
  • Exudative (serous or secondary RD): damage of the underlying RPE (e.g. severe hypertension) allows subretinal fluid to leak into the subretinal space under the sensory retina, so pushing this out and causing a detachment.

• Incidence is about 1 in 15,000 with a prevalence of about 0.3% of the general population.
• It most commonly occurs in the 40-70 year old age group although traumatic retinal detachment is more frequently seen in younger patients, particularly males.
• There is anecdotal evidence that it is less common in patients of African origin.

RD may be predisposed or caused by a number of conditions, some of which are applicable to all types of RD (see box) and other which tend to occur more specifically in different types of RD.

• Lattice degeneration
• Aphakia (no crystalline lens)
• Age-related retinoschisis
• Previous retinal break

• Proliferative diabetic retinopathy
• Sickle cell retinopathy
• Retinopathy of prematurity
• Toxocariasis
• Previous giant retinal tear

• Vascular disease e.g. severe hypertension, Coats disease
• Neoplasia e.g. multiple myeloma, choroidal tumours, haemangioma
• Inflammatory conditions e.g. Vogt-Koyanagi-Harada syndrome, posterior scleritis
• Congenital abnormalities e.g. coloboma
• Idiopathic central serous chorioretinopathy
• Nanophthalmos

History¹

The classic symptom is photopsia (flashing lights) which occurs in about 60% of patients. This tends to be induced by eye movements and is best seen in dim lighting conditions, particularly in the temporal, peripheral visual field. Photopsia is commonly associated with floaters (which may be described as a solitary opacity, a cobweb-like opacity or a shower of little spots). Some patients go on to describe a visual field defect apparent as a curtain descending over their vision. This may become worse as the day goes on. If the macula becomes involved, visual acuity is severely reduced. A simple tear in the absence of detachment may be completely asymptomatic.⁴

Examination⁵

• Visual acuity - this should be checked in all patients. If you strongly suspect a retinal detachment and the visual acuity is normal, referral is all the more urgent as the macula has not yet been involved and surgery can prevent it from becoming detached. A poor visual acuity suggests that the macula has already become detached - these patients do need urgent referral but their outcome is less promising.
• Visual fields - confrontational visual field testing will give you an idea of any gross visual defects corresponding to the area of detached retina - defects may not be picked up this way if they are small.
• Dilated fundal examination (check for an RAPD first) - once you have ruled out the presence of a relative afferent pupillary defect - RAPD (this indicates extensive RD), dilate the pupils. A large detachment can be seen as a sheet of sensory retina (usually hanging down) over which the vessels pass like paths over a hill. There may be an associated tear visible. If you have access to a slit-lamp, look for cells in the anterior chamber and the presence of tobacco dust, seen as grey-red specks just behind the pupil.

Ultimately, these patients will be fully re-examined in the Eye casualty department. This will involve a slit-lamp examination, indirect ophthalmoscopy (a head-mounted ophthalmoscope shines light through a wide-angled lens to allow a more peripheral look) or they will have a Goldmann triple mirror examination (which involves a slit-lamp and a contact lens applied against the anaesthetised cornea for a few minutes as the peripheral retina is examined). Some patients may also have an ultrasound performed where they simply have to lie back with their eyes closed as the probe is applied over the eyelid. Ophthalmologists will be assessing the type and extent of the detachment, the type, extent and number of any associated tears and any ocular co-morbidity.

Conditions with similar symptoms:

• Posterior vitreous detachment: this may lead to a retinal detachment.
• Atypical / ocular migraine
• Optic neuritis
• Cerebrovascular accident

Conditions with similar signs:

• Retinoschisis: usually benign condition where the retina is split into layers.
• Choroidal detachment: detachment of the vascular layer of the eye.
• Uveal effusion syndrome: rare idiopathic condition characterised by self-limiting choroidal and retinal detachment.

Diagnosis is confirmed on examination and any further investigations relate to the suitability of the patient to have a general anaesthetic.

Referral

Patients with a suspected RD should be seen by an ophthalmologist within 24 hours. The referral is all the more important if the visual acuity is good and therefore it is likely to be a 'macula-on' RD (the macula is still adherent to the underlying RPE) as opposed to a 'macula-off' detachment (where surgery is a rescue procedure rather than a protective one).

Medical treatment

Exudative RD caused by inflammatory conditions may respond best to treatment of the underlying condition. All other forms of RD need active intervention.

Laser treatment

This is performed if there is a retinal break but a full-blown RD hasn't yet developed (or if it is very small). The idea is to encircle the lesion with laser burns. The subsequent scar tissue prevents the tear from extending or subretinal fluid from leaking in or out of it. This can be done within a clinic setting.

Cryotherapy

This treatment modality may be selected in preference to laser treatment if the tear is in certain locations around the fundus, if the view is a little hazy or the pupil is small.

Surgical treatment

There are three approaches to surgical treatment:⁶

• Scleral buckle A silicone sponge or solid silicone is placed on the outside of the globe at the site of retinal breaks. The breaks themselves are treated with cryotherapy. The idea is to create an inward indentation of the sclera in order to close off the breaks and to reduce any associated vitreal traction. The explants may be short stumps placed locally or longer structures encircling the circumference of the globe. The choice depends on the nature of the break(s).
• Vitrectomy The vitreous may be removed in the case of a tractional RD. This technique is also sometimes used in rhegmatogenous RD.
• Pneumatic retinopexy A gas bubble (sometimes a silicone bubble) is injected inside the globe, over the site of the break (which has either previously been repaired with cryotherapy or is subsequently repaired with laser therapy) and pushes the flaps of retina against the periphery. If it stays in position, it permits the subretinal fluid to be resorbed over 24-48 hours. The bubble itself will very gradually be resorbed over weeks/months.

There are a few things that are helpful to know about surgical repair of RD:⁷

• It is carried out by specialist vitreoretinal surgeons (so a patient may find themselves being referred on from a DGH).
• It is usually done in working hours.
• It is usually performed under a general anaesthetic.
• It may involve 'posturing' (the gas or silicone bubble has to stay in the right place by keeping the head very still). This can be for up to 10 days.
• It usually involves a few nights stay (2 or 3 is common) at the hospital.
• Following discharge, patients should report excessive pain, loss of vision or an increasingly red eye to the team.
• Patients who have had pneumatic retinopexy should not travel by air and should advise anaesthetists that they have intraocular gas prior to any subsequent general anaesthetic. (The team will inform the patient when these activities are safe).

• Untreated retinal detachment Some retinal breaks and RDs are long-standing problems that are incidentally picked up. These are more likely to be stable but should be monitored and depending on the site and size, repair is carried out on an elective basis. All new problems should be treated as they may lead to extensive detachment and ultimately, sight loss.
• Laser treatment Complications are uncommon. If these do occur, they may include maculopathy (such as oedema), choroidal detachment, a secondary tear or haemorrhage.
• Cryotherapy There is often an associated transient lid chemosis. Other complications include transient diplopia, vitritis (inflammation of the vitreous) and rarely, maculopathy.
• Complications of surgical treatment¹ These are relatively uncommon and patients will be advised individually depending on the nature of their RD. Generic complications include haemorrhage, iatrogenic retinal break during the procedure, retinal incarceration (where the retina folds and gets pulled up into the break) and a paradoxical gaping of certain types of retinal break. Poor visual recovery and the need for a further procedure (due to re-detachment of the retina) are also possible. Rarely, a silicone explant may dislodge or even ulcerate out through the conjunctiva or the skin.

Patients who have simply needed laser treatment or cryotherapy should expect a full recovery. For those requiring surgery, recovery depends on the site and extent of the RD. A patient presenting late with a 'macula-off' RD has a very bleak outlook. However, most patients present early and prompt treatment should ensure good recovery with restoration of most of the vision. It may take several weeks for the vision to improve after surgery (particularly if there is a gas/silicone bubble in situ) and patients may go on to need additional spectacles or other visual aids.

A rhegmatogenous RD can be prevented if the retinal break is diagnosed and treated prior to the accumulation of subretinal fluid.