Posterior Segment Complications of Cataract Surgery (Prevention, Early Recognition and Management) PN Nagpal, Kamal Nagpal, Manish Nagpal
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Globe Injury during Retrobulbar and Peribulbar Anesthetic InjectionsCHAPTER 1

 
INTRODUCTION
Although present day cataract surgery is being carried out as an exhibition item under ‘topical’ and ‘no’ anesthesia, complete analgesia with immobilization of eyeball and eyelids is essential for safe conduct of intraocular surgery in majority of our patients. Hermann Knapp in 1884 first described the use of retrobulbar injection of cocaine to achieve regional ocular anesthesia for an enucleation procedure. In 1936, Atkinson successfully re-introduced the use of retrobulbar injections within the muscle cone using procaine.1 Since then, introduction of several modifications of the original technique, including the ‘peribulbar’ anesthesia, introduction of safer and longer lasting anesthetic agents, such as bupivacaine and lidocaine and synthesis of anesthesia enhancing drugs such as epinephrine and hyaluronidase have greatly popularized local anesthesia. The advantages of regional ophthalmic anesthesia surpass those of general anesthesia in terms of comfortable surgical results and economic efficiency in cataract surgery.
Over a period of time, it was realized that several serious complications could result from this technique, globe perforations being one of the most dreaded. Other important complications reported included retrobulbar hemorrhage, brainstem anesthesia,2 oculocardiac reflex,3–4 needle trauma to optic or other cranial nerves,5,6 allergic and toxic reactions to local anesthetics, central retinal artery occlusion,7,8 ocular explosion,9,10 scleral and eyelid necrosis,11 contralateral amaurosis,12–14 etc.
 
GLOBE PENETRATION AND PERFORATION
 
Incidence
The incidence of needle stick injuries varies from less than 0.1 percent for eyes with axial lengths shorter than 26 mm to 1 percent for axial lengths greater than 26 mm.15,16 However, it assumes considerable significance in view of the large numbers of ophthalmic procedures carried out in regional anesthesia, worldwide.2
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FIGURE 1.1: The relationship between the needle and the globe as it enters the muscle cone during a retrobulbar injection
 
Mechanism
Extraconal (peribulbar) injection is used to describe needle placement within the orbit but outside the extraocular muscle cone. Intraconal (retrobulbar) injection normally means placement of the anesthetic agent behind the globe, within the muscle cone.
  • Retrobulbar injections (Figure 1.1): Injection of any drug by needle advancement into the orbit is essentially a blind procedure. In retrobulbar injections, the needle passes near the equator of the globe into the intraconal space. This renders it in close proximity to several vital structures, such as the posterior pole of the eye, the optic nerve, central retinal vessels and the dural sheath. During a routine retrobulbar injection directed towards the apex, the needle is closest to the globe just posterior to the equator. This point, thus is extremely susceptible to penetration from the needle point. This may explain the predilection of inferior arcades as a common site of perforation breaks.17 The ‘up and in’ position of the globe popularized by Atkinson brings the posterior pole of the eye and the optic nerve closer to the needle tip2 (Figures 1.2 to 1.4).
  • Peribulbar injections: The injections were developed to avoid the intraconal area by injecting the drug outside the muscle cone and allowing it to diffuse inwards. However, the confines of the orbital space ensure a close proximity of the globe and the needle tract, similar to that in the retrobulbar injection, particularly in high risk eyes (see below). Additional superior extraconal injection probably doubles the risk of penetration.17,18
 
Risk Factors
  • Long axial length of the eye 15,163
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    FIGURE 1.2: Retrobulbar injection with eye in the primary gaze; the needle does not cross the mid-saggital plane
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    FIGURE 1.3: Upward and nasal gaze places the optic nerve in the path of the needle
  • Posterior or inferior staphyloma
  • Deep set eye with prominent eyebrows
  • Enophthalmos
  • Previous ophthalmic surgeries, particularly scleral buckling procedures
  • Multiple injection sites
  • Physician experience, patient cooperation 19–21
  • Length and sharpness of the needle
  • Position of the eye4
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FIGURE 1.4: Downward and outward displacement of the optic nerve in upgaze
 
Prevention
  • Surgeon's understanding of orbital anatomy and physical relationships of structures within the orbit is the foremost prerequisite for a safe and effective regional anesthesia.
  • Preoperative assessment of the globe (protruding or deep seated eyeball) and orbit and possibly ultrasound evaluation of a high risk patient brings any anatomic variations into the surgeon's knowledge.7 These variations should be kept in mind, while injecting in a high risk patient.
  • In order to minimize the chances of globe injury by the needle during regional blocks, a thorough assessment of the patient's physical and psychological build-up is essential. General anesthesia is usually preferred for all subjects under 18 years of age, or those who are unduly anxious about surgery or phobic of needle pricks. These patients will be more prone to not only an uneasy surgical course, but also are at a greater risk for block related complications. Patients considered good candidates for regional anesthesia should undergo a frank pre-operative counseling of the procedure with communication regarding the risk factors. This time spent towards educating and bonding with the patient helps alleviate patient's fears and ensures greater compliance during the anesthesia and surgery.
  • Preoperative medication: The site of injection can be prepared by local application of surface anesthetic agent, such as Prilox (combination of prilocain and xylocain) to reduce pain during injecting. If preoperative reluctance to an injection close to the eyeball is anticipated (especially in 18 to 25 year old subjects), block can be given under ultra short-acting general anesthesia, intravenous injection propofol (1%, 2 mg/kg). The outcome of this agent is extremely clear headed and smooth.5
  • Needle selection: Blunt tipped needles have been recommended on the basis of their superiority in reducing incidence of bleeding and ocular penetration. 9,17 However, these claims have been negated by evidence regarding greater damage produced by dull and longer needles as compared to fine disposable ones. Using blunt tipped does not ensure protection against penetration into the globe. On the other hand, these are more painful for the patient. Fine (27–25 gauge) needles with a long bevel commonly used are relatively atraumatic, more comfortable for the patient and may result in less damage if penetration does occur. The risks of ocular perforation and optic nerve damage may decrease with use of the long 25 gauge (25 mm) needle instead of the longer (37.5 mm) retrobulbar needle.17 The needle should not, and need not be inserted more than 2.5 cm. The injection should be made with the globe in the primary gaze position when the optic nerve remains in its normal position behind the globe, and the posterior part of the globe is not presenting itself for presentation. Facing the bevel of the needle towards the eyeball decrease the chances of perforation. It is helpful to orientate the needle with the bevel facing in the same direction as the printed scale on the syringe to avoid confusion once the needle tip is out of sight.
  • If a supplementary injection in the upper quadrant is needed, it should be postponed for short while, to wait for the absorption of drug so that the eyeball is in a nearly original position and drug induced eyelid displacement is not a risk factor.
 
Management
An early recognition of an inadvertent injury and its early assessment by a vitreoretinal surgeon is of the utmost importance. During and after the injection, the cataract surgeon should actively look out for any signs of accidental perforation. Careful observation of the globe during needle entry may alert the surgeon to impending globe penetration by rotation of the eye toward the direction of needle entry. The so-called “wiggle test” is useful in determining if the needle tip has impaled an orbital structure fixed to the eye.9 In this test, when the retrobulbar needle is in the orbit, the needle is moved from side to side; any rotation of the eye suggests that the sclera, optic nerve, or an extraocular muscle may have been penetrated. Another useful test is to ask the patient to move the eyeball on both sides, with the needle in place, but before injecting the drug. Free movements signify that the needle is away from the globe. In case the movements are restricted, one may avoid injecting the drug in order to prevent a possible intraocular deposit of the drug.
Signs like sudden give in feeling or unusual difficulty in injecting, severe pain response from the patient 9,10 sudden increase in intraocular pressure (as evidenced by corneal edema) 8,9 or hypotony, hyphema, loss of corneal transparency, subconjunctival hemorrhage or loss of the red reflex indicate penetration into the globe. In case of any such suggestion, immediate fundoscopy with indirect 6ophthalmoscope is recommended. In cases where visualization of fundus is not possible, B-scan ultrasound can be used to evaluate the situation.
Whenever possible, according to visibility, it should be attempted to differentiate the needle stick injury into penetrating (only an entry site) and perforating (an entry and an exit site). A penetrating injury, with adequate fundal view without retinal detachment may be watched as local hemorrhage may preclude prophylactic laser therapy (cryotherapy in the presence of local hemorrhage has been implicated in the development of proliferative vitreoretinopathy). Trans pars plana vitrectomy is generally indicated in cases with adequate fundal view with retinal detachment or inadequate fundal view due to vitreous hemorrhage.
If upon indirect ophthalmoscopy or ultrasound, neither vitreous hemorrhage nor retinal detachment is detected, the surgeon can consider cataract extraction as planned with immediate retinal examination postoperatively for management of retinal breaks.16,22
Advanced cataract, which can preclude the posterior segment surgeons viewing of the fundus and management of the posterior segment condition, is another indication of early cataract extraction.
 
Clinical Presentations of Complications and Their Management
  • Unrecognized perforation: At times, it can happen that the needle travels through the globe (seen as an entry and exit wound) and as a result the anesthetic is still injected in the periocular space, leading to adequate anesthesia and akinesia. There is often nothing unusual during the insertion of the needle or injection of anesthetic. The loss of vision may have been attributed to the effect of local anesthetic blockade and the visual impairments are noticed much later. Fundus examination reveals optic disc edema, retinal edema and vitreous hemorrhage and in the later stages, signs of optic nerve atrophy. CT scan and ultrasonographic examination may reveal thickening of the optic nerve either due to hemorrhage or injection of anesthetic. 8,12 Other, innocuous, unnoticed perforations may manifest solely as chorioretinal scars detected years later.
  • Severe hypotony: Puncture wound from a needle along with external pressure (digital massage) is likely to cause globe explosion. An important sign of scleral rupture is a ‘give in’ response to digital massage. Prompt exploration with surgical closure of all wall defects is important, with fundoscopic evaluation and subsequent management after the intraocular pressure is stabilized. In case of a posterior rupture, not amenable to surgical closure, conservative approach with intraocular air injection (if needed for severe hypotony), systemic antibiotics, and total rest with patching of both the eyes is advocated.
  • Vitreous hemorrhage (Figure 1.5): B scan ultrasound monitoring of posterior segment is done to rule out retinal detachment or choroidal hemorrhage.
    7
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    FIGURE 1.5: Localized hemorrhage due to needle tip perforation. Site of perforation seen (arrow)
    Vitrectomy is often indicated to manage these adjunct problems and minimize the risk of future retinal detachment and proliferative retinopathy developing from untreated retinal tears.17,21,24
  • Retinal tears: These are usually located along the inferotemporal vascular arcade. In cases of second (supplement) injection of peribulbar anesthesia, tears may be seen supranasally.8,17,18 Even 360° giant retinal dialysis has been reported.10 Early repair of these tears with laser is indicated, if media is clear enough.
  • Retinal detachment (Figure 1.6): Retinal detachment, with or out vitreous hemorrhage should be considered for an early surgical intervention with vitrectomy being the procedure of choice, to avoid the high risk of proliferative vitreoretinopathy.7,18,23 Aggressive use of postoperative steroids depending upon the patient's tolerance is helpful.
  • Choroidal hemorrhage: Small choroidal hemorrhage can be monitored closely. Large hemorrhages, particularly when there is a retina to retina contact are watched closely to look for clot lysis, after which external drainage is performed.
  • Ocular explosion (Figures 1.7 and 1.8): Accidental entry of needle intraocularly and intraocular deposition of the drug during anesthetic injection causes progressive increase in intraocular pressure. When this exceeds the ultimate strength of the eye by continued injection of anesthetic agents without realizing the penetration, the eye ruptures and intraocular contents expel out, which has been observed clinically and experimentally.9,25
    8
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    FIGURE 1.6: Retinal detachment with PVR due to needle stick injury. Site of perforation seen (arrow)
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    FIGURE 1.7: Globe rupture during experimental intraocular saline injection. Whitening of the cornea precedes the rupture at the equator
    9
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    FIGURE 1.8: Globe rupture during experimental intraocular saline injection. Whitening of the cornea precedes the rupture at the equator with expulsion of the crystalline lens
    Common sites of globe rupture are equatorial (9 to 12 mm posterior to the limbus) and perilimbal. Lens extrusion may be associated with perilimbal rupture.9,10,25 Sometimes it may be present as posterior scleral rupture with totally normal looking anterior segment. These injuries are dealt with on the lines of open globe injuries.
  • Intraocular drug toxicity and fluid jet trauma: It has been seen that the retinal toxicity of ophthalmic anestheic agents is usually transient, and even a significant loss of vision completely reverses in absence of other mechanical complications.22,26,27 On the contrary, the force of the fluid jet stream can cause retinal tears at the point of contact with the retina or elsewhere, owing to vitreous traction. Prompt detailed retinal evaluation is indicated to avoid further complications.
  • Amaurosis and optic nerve atrophy: Rarely, local anesthetics can cause amaurosis as a consequence of optic nerve block. Optic nerve atrophy can be a consequence of damage to the optic nerve or central retinal artery with injection into optic nerve sheath.12,1410
Needle perforation is a rare but potentially serious complication of local anesthesia injection. This may be explained in the informed consent. Patient outcome depends on the amount of initial damage to the retina and despite successful retinal reattachment, factors including epiretinal gliosis, optic atrophy and proliferative vitreoretinopathy can result in poor visual acuity. The ophthalmic surgeon may be held liable for damages even if an anesthesiologist administers the anesthesia. Whoever is responsible for the actual injection should be adequately trained to give ocular injections and alerted to any risk factors that might increase the possibility of needle perforation such as increased axial length, previous scleral buckle or posterior staphyloma. Patient's primary care physician should be consulted in cases where the severity of a pre-existing condition or illness could increase the patient's anesthesia risk and the same should be documented. The use of no needle techniques such as topical anesthesia or sub-Tenon's anesthesia may help minimize the likelihood of scleral perforation in high risk cases.28,29
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