Ординатура / Офтальмология / Английские материалы / Moorfields Manual of Ophthalmology_Jackson_2007

Retinal Degenerations and Tears

Peripheral retinal degenerations

Background There are several peripheral vitreoretinal degenerations. Some predispose to retinal detachment (RD).

Classification

■Lattice : retinal thinning associated with overlying vitreous liquefaction, retinal vascular sclerosis, and abnormally strong vitreoretinal adhesion (Fig. 11.3).

■Nonlattice : several peripheral degenerations such as white- without-pressure, snail-track, microcystoid, reticular, and pavingstone.

Management

■Lattice : there are three common situations: lattice alone, atrophic round holes in lattice, and lattice associated retinal tears. Retinopexy may be appropriate to reduce the risk of RD (Table 11.1).

■Nonlattice : prophylactic treatment is not usually required. Provide all patients with a retinal detachment warning ([RDW] p. 522).

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C

D

Fig. 11.3—cont’d.

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Retinal degenerations and tears

Retinal breaks

Background Full-thickness defects that usually occur following posterior vitreous detachment (PVD). Their configuration influences the likelihood of subsequent retinal detachment (RD).

Symptoms, signs, and investigations Similar to PVD except Shafer’s sign is usually positive (p. 521).

Management See Table 11.1. This outline will be modified by factors such as the break size and position, other ocular

disease, patient/clinician preference, and increased pigmentation under break (indicates RPE hyperplasia and chronicity). Provide an RDW.

Retinopexy Two options exist: laser or cryotherapy (Fig.

11.4). If possible, select laser as it is less destructive. Laser safety training is often mandatory. For techniques see Box 11.1 and 11.2.

Consent

■Benefit : reduced risk of RD and visual loss.

■Risk : failure to prevent RD, re-treatment, visual field defect, accidental macular treatment and visual loss, subsequent distortion from epiretinal membranes (can also occur with untreated retinal breaks).

Box 11.1: Laser retinopexy

1.Obtain written consent. Warn the patient that they will feel the laser pulse, but try not to move.

2.Connect the argon laser to either the slit lamp or indirect output.

3.Once warmed up, fire a test shot against a nonreflective object.

4.Ensure patient is maximally dilated, in a darkened room, with topical anaesthesia in both eyes. Others in the room require protective goggles.

Slit-lamp : select the lens that gives the best view, e.g. transequator contact lens or three-mirror. Noncontact lenses (e.g. 90 D) may be used, but require more power and don’t stabilize the eye. Select 200 microns spot size; 0.1 seconds.

Indirect ophthalmoscope with 20 D lens: good for peripheral breaks and allows indentation. Spot size varies with focusing.

5.Adjust the aiming beam brightness.

6.Confirm landmarks to prevent accidental macular burns.

7.Laser power will vary with media clarity, fundus pigmentation, and machine. Start low and gradually increase to produce a definite white spot.

8.Encircle the break and any subretinal fluid with two rows of semi-confluent spots (Fig. 11.4).

9.Occasionally periocular LA is needed if patients cannot tolerate laser treatment.

Box 11.2: Cryotherapy

1.Explain the procedure and obtain written consent.

2.Anaesthetic requirements vary from topical, subconjunctival injection at the cryo-site, to peribulbar. Fellow eye topical anaesthesia may help keep lids open.

3.Most machines require gas purging, e.g. set the temperature to −25ºC, depress footpedal for 10 seconds, wait 1 minute, and repeat.

4.Cryoprobes are notoriously unreliable, so check. Set the treatment temperature (typically −85ºC), dip into sterile water, depress the footpedal for 10 seconds, lift out. A 5 mm ice-ball

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Box 11.2: Cryotherapy—cont’d

5.The handle is usually marked to manually orient the probe, as the tip is not visible during treatment.

6.Beware : it is possible to indent the break with the probe handle whilst the tip is accidentally treating the macula. Avoid treating the ciliary body (painful).

7.View the fundus with the indirect ophthalmoscope and a 20 D lens.

8.Indent the break with the probe tip, and plan treatment.

9.The break margin requires treatment but not the central defect.

10.Larger breaks may require treatment in more than one site, but avoid unnecessary treatment to reduce the risk of epiretinal membranes.

11.Depress the footpedal until the treatment area freezes, then release.

12.Wait until fully thawed before moving the probe to another site to avoid scleral/choroidal damage.

13.Wait 1 minute after the last treatment before turning off machine. This allows gas to escape

14.Provide analgesia.

Follow–up Two weeks. If an RPE reaction fully encircles the break, discharge with an RDW for annual dilated optometry review. Review those with subretinal fluid within 2 days, then as required.

Rhegmatogenous Retinal

Detachment

Background Usually occurs secondary to retinal tears

(rhegma ). These are most commonly caused when the posterior vitreous face separates from the internal limiting membrane and vitreoretinal adhesions tear the retina. Syneretic vitreous fluid passes through these tears, detaching the retina from the RPE. More common in high myopes.

Symptoms Flashing lights in the temporal field, floaters, field loss, variable loss of VA.

Signs Bullous RD is easily detected (Fig. 11.5) but the only sign of shallow elevation may be loss of choroidal markings and subtle elevation. RD may be associated with an RAPD, low IOP, vitreous haemorrhage, and tobacco dust (p. 521). Chronic detachments often have thinned retina, RPE pigmentation at the border of attached and detached retina (‘high-water mark’, example

p. 552), and may have retinal telangiectasia or retinal scarring (proliferative vitreoretinopathy, PVR). There is sometimes a mild anterior uveitis or raised IOP.

Examination Record VA, RAPD, lens status (clear, cataractous, pseudoaphakic or aphakic), and presence of posterior

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vitreous detachment (PVD, p. 521). Draw the extent of the RD noting macular involvement, breaks, and lattice degeneration. Check the periphery of both eyes using an indirect ophthalmoscope, 20 D lens (or equivalent), and 360º indentation. Finding breaks can be difficult but their position is suggested by Lincoff’s Rules (see Fig. 11.6). Trauma may cause tears at the anterior retinal border that are hard to detect (see Retinal dialysis; p. 552). Grade any proliferative vitreoretinopathy (PVR) as A (increased vitreous haze and pigment), B (inner retinal fibrosis), and C (full-thickness retinal folds), and note if anterior (A) or posterior (P), and extent in clock hours, e.g. PVR CA2, CP6.

Investigations If there is significant media opacity, perform same-day ultrasound.

Differential diagnosis Consider PVD, serous RD (no breaks with shifting subretinal fluid), and tractional RD (usually caused by fibrosis from severe diabetic retinopathy or PVR). Retinoschisis occurs secondary to an intraretinal split that produces an appearance similar to RD. It is often bilateral and symmetric, is more common in hypermetropes, tends not to

produce a ‘high-water mark’, and unlike RD produces an absolute rather than partial scotoma. The elevated inner retinal layer appears thin and atrophic. Retinoschisis is extremely uncommon in myopes.

Management Refer for same-day vitreoretinal opinion. Aim to repair most sight-threatening macula-on RDs within 24 hours and macula-off RDs less urgently, but as soon as possible. Three surgical options exist:

■Pneumatic retinopexy : suitable only for a minority of straightforward cases with superior breaks. A vitreous injection of expansile gas produces a flotation force that tamponades retinal breaks and flattens the retina. Cryotherapy or laser retinopexy creates an adhesive scar between the break and RPE, preventing vitreous fluid moving into the subretinal space.

■Conventional (cryobuckle) surgery : a silicone explant is sutured externally to the sclera, indenting the RPE toward the retina. This relieves vitreoretinal traction and promotes re-attachment. Surgery may be augmented by trans-scleral drainage of subretinal fluid. Retinopexy is applied to seal the break. Gas is sometimes injected.

■Vitrectomy : an endoscopic light, vitreous infusion cannula, and vitrector are inserted through three 20 or 23-gauge ports at the pars plana. The vitrector is used to remove the vitreous, relieving any vitreoretinal traction. Retinopexy is by trans-scleral cryotherapy or endoscopic laser. A slowly

absorbing gas (sulphur hexafluoride [SF6] or octafluoropropane [C3F8]) tamponades the retina, or silicone oil in complex cases.

Consent In a national audit, 81% of primary RDs required only one operation but subspecialists achieved 87% success. The final re-attachment rate is >95% with two or more operations. The VA following macula-off RD varies widely, but some reduction is to be expected. Macula-on RDs usually retain good acuity although epiretinal membranes may occur in 4–8% of cases. Severe loss of vision can occur from haemorrhage and infection (<1%). Prophylactic retinopexy may be required in the fellow eye (see Table 11.1).

■Pneumatic retinopexy : lower success rate than other options but simpler procedure. The consequences of gas injection are similar to vitrectomy.

■Cryobuckle : Risks include diplopia ( ≈3%); myopic shift;

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■Vitrectomy : markedly impaired vision until gas absorbs in 1

week (air), 2 weeks (SF6), or 2 months (C3F8). Patients must not fly during this period as gas expansion may dangerously elevate IOP. Patients should advise anaesthetists that they have gas in their eye, as inhaled nitrous oxide may also elevate IOP. Most patients require 10 days of head posturing to float the gas bubble onto the breaks. Postoperative IOP elevation is normal and may require treatment. Silicone oil is removed later if the retina is secure, typically at 3–6 months. Silicone may lead to chronic IOP elevation and corneal changes. See the general risks of vitrectomy below.

■Risks of vitrectomy : Patients undergoing vitrectomy should be aware of the following risks: general progressive nuclear

sclerosis (81% at 6 months, 98% at 1 year); iatrogenic retinal breaks (≈5%) that require retinopexy/gas injection and may lead to RD; choroidal haemorrhage (<1%); endophthalmitis

(<1%). Intravitreal gas injection may be required.

For patient information see http://www.rcophth.ac.uk/scientific/ publications.html

Postoperative care Patients are usually discharged at the first postoperative day, or treated as day cases. Confirm the retina is attached. The RPE pump will often remove shallow residual subretinal fluid. All patients require a retinal detachment warning (p. 522) and G. chloramphenicol 0.5% q.d.s. 2 weeks, G. atropine 1% b.d. 2 weeks, and G. dexamethasone 0.1% q.d.s. 2 weeks, then tail off over 3 weeks.

■Pneumatic retinopexy : check for inferior secondary retinal breaks caused by gas-induced vitreous traction. Advice is as for vitrectomy, but more frequent follow-up is required initially, e.g. day 1, 3, and 7.

■Cryobuckle : check there is an adequate indent directly under the breaks and consider anterior segment ischaemia (uncommon) if there is raised IOP, anterior uveitis, and

pain. Routine follow-up is day 1, 10, 30, then optometrist yearly.

■Vitrectomy : the gas fill should be at least 70% of the vitreous cavity, especially if there are inferior breaks. Advise on head posturing, e.g. right cheek to pillow for a right eye RD with nasal breaks. Posture 50 minutes per hour for 10 days and be