A cluster of patients with inferior rectus restriction following local anesthesia for cataract surgery

Strabismus patterns after cataract surgery in adults

New-onset binocular diplopia after cataract surgery in adults is a rare but significant complication. The aim of this study was to analyze causes, risk factors, and treatment outcomes. Forty consecutive patients with new-onset binocular diplopia after uncomplicated cataract surgery were enrolled in this retrospective study at a tertiary medical center. We evaluated risk factors including type of anesthesia, preoperative presence of strabismus, and others regarding their effect on the development of diplopia after cataract surgery. We further analyzed ocular alignment and motility at presentation and during the clinical course. The majority of the patients with new-onset diplopia presented after cataract surgery on the left eye (28 of 40). Vertical strabismus occurred in 37 of 40 patients, and regional (peri- or retrobulbar) anesthesia was the main risk factor for postoperative diplopia (present in 37 of 40). There were four distinct ocular dysmotility patterns in patients with vertical strabismus: deficient elevation with (type 1a) or without over-depression (type 1b), deficient depression (type 2), or normal motility (type 3). After surgery of the right eye, most patients (6 of 9) showed type 2. After cataract surgery on the left eye, type 1a was most common (20 of 24). Three patients had horizontal strabismus due to a decompensated heterophoria or convergence insufficiency. In total, 17 patients required strabismus surgery (mean 1.3 operations, range 1-3). Regional anesthesia was the main risk factor for new-onset diplopia after cataract surgery in adults. Distinct strabismus patterns were observed for left and right eyes.d.

Strabismus After Ocular Surgery

Many types of ocular surgery can cause diplopia, including eyelid, conjunctival, cataract, refractive, glaucoma, retinal, and orbital surgery. Mechanisms include direct injury to the extraocular muscles from surgery or anesthesia, scarring of the muscle complex and/or conjunctiva, alteration of the muscle pulley system, mass effects from implants, and muscle displacement. Diplopia can also result from a loss of fusion secondary to long-standing poor vision in one eye or from a decompensation of preexisting strabismus that was not recognized preoperatively. Treatment, which typically begins with prisms and is followed by surgery when necessary, can be challenging. In this review, the incidence, mechanisms, and treatments involved in diplopia after various ocular surgeries are discussed. [J Pediatr Ophthalmol Strabismus. 2017;54(5):272-281.].

Post-cataract surgery diplopia: aetiology, management and prevention

Diplopia is an infrequent but distressing adverse outcome after uncomplicated cataract surgery. Many factors may contribute to the occurrence of this problem, including prolonged sensory deprivation resulting in disruption of sensory fusion, paresis of one or more extraocular muscles, myotoxic effects of local anaesthesia, optical aberrations (for example, aniseikonia) and pre-existing disorders (for example, thyroid orbitopathy). The purpose of this review is to present the aetiology and clinical features of diplopia after cataract surgery and to discuss the possible modalities for the prevention and treatment of this frustrating complication.

Diplopia and strabismus following ocular surgeries

Postoperative diplopia and strabismus may result from a variety of ocular surgical procedures. Common underlying mechanisms include sensory disturbance, scarring, direct extraocular muscle injury, myotoxicity from injections of local anesthesia or antibiotics, and malpositioning of extraocular muscles by implant materials. The most common patterns are vertical and horizontal motility disturbance. Treatment options include prisms, botulinum, occlusion, or surgery.

Strabismus complications from local anesthetics

Strabismus developing after retrobulbar or peribulbar anesthesia for both anterior and posterior segment eye surgery may be due to myotoxicity to an extraocular muscle from the local anesthetic agent. Initial paresis often causes diplopia immediately after surgery, but later progressive segmental fibrosis occurs, and/or hypertrophy of the muscle, producing diplopia in the opposite direction from the direction of the initial diplopia. The inferior rectus muscle is most commonly affected. Usually a large recession on an adjustable suture of the involved muscle(s) yields good alignment. Using topical anesthesia or sub-Tenon's anesthesia can avoid this complication.

Advances in ophthalmic regional anaesthesia

Although retrobulbar and peribulbar regional anaesthetic techniques are used (by both anaesthesiologists and ophthalmologists) in various types of eye surgery, topical anaesthesia of the conjunctiva and cornea, followed--as needed--by sub-Tenon's block, is now common in routine cataract surgery. Intracameral administration of local anaesthetic by the ophthalmologist is also performed. Sedation during ophthalmic surgery is distinctly lighter than for other surgery because it is essential that the patient remains alert and can cooperate with the surgeon. Continuous insufflation of oxygen-enriched air is needed to ascertain that CO2 has been flushed away. With a catheter placed into the nostril, the patient (whose head is draped and 'hidden') can have the end-tidal CO2 monitored. Finger index (FI), a palpation method that assesses the ease of performing retrobulbar block, is introduced. Because of the risk of life-threatening complications in ophthalmic regional anaesthesia, the services of an anaesthesiologist must be available and training of anaesthesia residents in ophthalmic regional anaesthesia is highly recommended.

Effect of retrobulbar injection of lidocaine on saccadic velocities

PURPOSE

To determine whether exposing the extraocular muscles (EOMs) to lidocaine via retrobulbar injection for cataract surgery has a demonstrable negative effect on subsequent function of the muscle.

SETTING

York Finch Eye Associates, Humber River Regional Hospital, and Toronto Western Hospital Research Institute, Toronto, Ontario, Canada.

METHODS

This study comprised 37 eyes that had phacoemulsification and posterior chamber intraocular lens implantation; 13 eyes had retrobulbar lidocaine with hyaluronidase and 24 eyes, topical anesthesia. The postoperative saccadic velocities were compared with the preoperative velocities using a sensitive recording device. The results were compared within and between the retrobulbar lidocaine and topical anesthesia groups.

RESULTS

No detectable decrement in postoperative saccadic velocities was detected in any patient, and no difference was found between the groups.

CONCLUSIONS

Exposing EOMs to lidocaine for cataract surgery had no detectable negative effect on saccadic velocities 1 week after surgery.

Vertical diplopia following peribulbar anesthesia: the role of hyaluronidase

PURPOSE

To estimate the incidence of vertical diplopia following peribulbar anesthesia in otherwise uncomplicated cataract surgery and to establish whether the use of hyaluronidase in the peribulbar injection mixture affected the likelihood of this complication.

METHODS

Nine hundred forty consecutive phacoemulsification procedures using peribulbar anesthesia were retrospectively reviewed to identify cases of postoperative vertical diplopia. Case notes were reviewed to establish the nature and timing of the onset of diplopia, the anesthetic technique, and whether hyaluronidase was used. The patterns of progression as demonstrated by serial Hess charts were compared.

RESULTS

There were 6 cases of vertical diplopia (incidence, 0.64%). All showed an immediate postoperative hypertropia in the injected eye changing during a 4- to 6-week period to hypotropia with restriction of upgaze. All applications of anesthesia were administered by consultant anesthetists, associate specialists, or residents under their direct supervision using 25-mm, 25-gauge needles with 2% lidocaine. Hyaluronidase was included in the injection mixture for 435 (46%) of the cases and was not included for 505 (54%) of the cases. All 6 cases of vertical diplopia occurred in the group in which hyaluronidase was not used, which has a significant association (chi-square test, 5.22; P = .023).

CONCLUSION

Hyaluronidase should be included in peribulbar anesthetics to reduce the risk of postoperative vertical diplopia.

Anaesthesia-related diplopia after cataract surgery

BACKGROUND

We studied the incidence and clinical characteristics of persistent diplopia related to anaesthesia for cataract surgery in a general hospital.

METHODS

This was a retrospective review of anaesthesia for 3587 cataract surgeries. Of all the cases of diplopia referred to the ocular motility clinic after cataract surgery, those involving anaesthesia-related diplopia lasting longer than 1 month were studied.

RESULTS

During the study period, 3450 cataract surgeries were performed by phacoemulsification and 137 by extracapsular extraction. Retrobulbar block was used in 2024 cases, peribulbar block in 98, topical anaesthesia in 1420 and general anaesthesia in 43. Twenty-six cases of persistent diplopia were found (0.72% incidence), nine of which (0.25%) were considered to be related to anaesthetic factors; five of the latter involved the left eye. Five were caused by paresis of the inferior rectus muscle and three by fibrosis. In one patient, the inferior oblique muscle was affected. Anaesthesia was by retrobulbar block in eight cases (0.39%) and by peribulbar block in one. No diplopia was found in patients who had topical or general anaesthesia. Treatment was with surgery in two patients and with prisms in six. One patient continues to be studied.

CONCLUSIONS

Persistent diplopia can occur after cataract surgery using retrobulbar block predominantly through direct damage to the inferior rectus muscle. The overall incidence of anaesthesia-related diplopia in this series was 0.25%.

Thyroid disease and vertical rectus muscle overaction after retrobulbar anesthesia

PURPOSE

To determine the associated factors of persistent diplopia after retrobulbar anesthesia.

SETTING

Strabismus Section, Department of Ophthalmology, Seoul Municipal Boramae Hospital, Seoul, Korea.

METHODS

A prism and cover test in the diagnostic positions of gaze, force-generation test, and forced-duction test were performed in 11 patients with vertical rectus overaction after retrobulbar anesthesia. A Tensilon (edrophonium chloride) test, thyroid function test, and orbit computed tomography were performed in 8 patients.

RESULTS

None of the 11 patients reported diplopia before receiving local anesthesia. Ten patients showed ipsilateral hypertropia with superior rectus overaction and 1 patient, ipsilateral hypotropia with inferior rectus overaction. One patient had partial fibrosis of the medial half of the superior rectus, presumably caused by a bridle suture. Four (50%) of 8 patients in whom a thyroid function test was performed had abnormal findings; 1 had a history of systemic dysthyroidism.

CONCLUSIONS

In this study, permanent vertical strabismus after local anesthesia was entirely the result of overactive vertical rectus muscles, mostly the superior rectus muscle. Half the patients who had a thyroid function study had abnormal findings.

Neuro-ophthalmologic complications of cataract surgery

Neuro-ophthalmologic complications from cataract surgery are uncommon and include central nervous system toxicity, binocular diplopia, traumatic optic neuropathy and ischemic optic neuropathy. Retrobulbar blocks may be accidentally injected into the subarachnoid space with diffusion to the brainstem. This leads to cardiovascular, respiratory, and mental status compromise. Most patients have complete recovery with adequate support. Post-operative, binocular diplopia may occur secondary to anisometropia or previously unrecognized misalignment. Periocular injection may cause paresis or fibrosis of extraocular muscles. Anterior or posterior ischemic optic neuropathy can occur in the first 6 weeks after cataract surgery with or without periocular injection. The risk to the other eye is high with subsequent contralateral cataract extraction. Post-operative vision loss associated with direct traumatic needle injury is recognized immediately. Therefore, an orbital MRI may be warranted for a patient with an optic neuropathy in the first 24 hours after cataract surgery using periocular anesthesia. If evidence of needle injury is present on neuroimaging, a trial of steroids should be considered.

Persistent vertical binocular diplopia after cataract surgery

PURPOSE

To report the incidence of, and factors associated with, persistent vertical diplopia after cataract surgery.

DESIGN

Consecutive interventional case series.

METHODS

Retrospectively, all adult patients examined during a five year, five month period because of new onset persistent (>3 months) vertical binocular diplopia after cataract surgery were analyzed. All patients had their cataract surgery at the same outpatient ophthalmic surgery center, and were referred to the author, enabling calculation of incidence. Trends in anesthesia type and strabismus complications therefrom were also assessed. Comparison was made between ophthalmologist-administered retrobulbar anesthesia versus anesthesia staff-administered retrobulbar anesthesia. Incidence during a period in which hyaluronidase was not incorporated in the retrobulbar anesthetic was calculated.

RESULTS

Persistent vertical diplopia occurred after cataract surgery in 32 (0.18%) of 17,531 eyes that had cataract surgery. No patient whose cataract surgery was conducted with topical anesthesia (3817 eyes) had persistent vertical diplopia, whereas 32 (0.23%) of the 13714 eyes whose cataract surgery was done after retrobulbar anesthesia were affected. No cases of persistent postoperative diplopia were found among 7410 cataract surgery eyes after retrobulbar injection given by one cataract surgeon. There was a threefold greater number of left eyes involved than right eyes (P <.005). No significant (P >.20) increase in cases of persistent vertical diplopia was noted during a period of hyaluronidase shortage.

CONCLUSIONS

In this study, persistent binocular vertical diplopia after cataract surgery occurred in 0.23% of cases in which retrobulbar anesthesia was performed. No cases were found after topical anesthesia. Occurrence may be technique-related.

Diplopia and ptosis following injection of local anesthesia without hyaluronidase

In a university ophthalmology department, a cluster of postoperative diplopia and ptosis cases occurred in the initial 3 months after hyaluronidase (Wydase) became unavailable for use with injection anesthesia. These cases suggest that hyaluronidase, when used with injection anesthesia, may protect extraocular muscles and nerves from the toxic effects of local anesthetic agents. The spreading action of hyaluronidase facilitates uniform diffusion of anesthetic agents. This prevents elevated extracellular tissue pressure, a cause of ischemic damage to extraocular muscles or nerves. Hyaluronidase may also prevent focal accumulations and concentrations of local anesthetic agents, which at high enough levels may cause myotoxic or neurotoxic damage, fibrosis, and contracture of extraocular muscles or nerves.

Incidence of ocular misalignment and diplopia after uneventful cataract surgery

PURPOSE

To evaluate the incidence of ocular misalignment and diplopia after uneventful cataract surgery.

SETTING

An outpatient private practice eye institute.

METHODS

One hundred thirty-eight patients referred to 1 cataract surgeon were prospectively evaluated. Orthoptic evaluations were performed within 1 month before and then 1 day, 1 week, and 1 month after cataract surgery. Anesthesia was by retrobulbar injection, and cataract extraction was done by phacoemulsification.

RESULTS

Cataract surgery was performed in 118 patients. Preoperatively, 16 patients had ocular misalignment; 10 were phoric, 4 were intermittently tropic, and 2 were tropic. Follow-up evaluation was obtained for 101 patients (86%) at 1 day, 91 (77%) at 1 week, and 88 (75%) at 1 month. A change in ocular alignment occurred in 22 of 101 patients (22%) at 1 day, 9 of 91 (10%) at 1 week, and 6 of 88 (7%) at 1 month. Only 1 patient who had a change in alignment at 1 month was symptomatic.

CONCLUSIONS

A persistent change in ocular alignment after uneventful cataract surgery occurred in 7% of patients. However, symptomatic diplopia was uncommon (1 in 118; 0.85%) in this relatively small series.

Vertical diplopia following local anaesthetic cataract surgery: predominantly a left eye problem?

PURPOSE

Vertical diplopia is an uncommon but disappointing complication of otherwise successful local anaesthetic cataract surgery. We studied strabismus patterns in a group of such patients to identify the nature and extent of extraocular muscle involvement.

METHODS

A retrospective review identified 15 cases of vertical diplopia following local anaesthetic cataract surgery between July 1994 and January 1998. Peribulbar anaesthesia was used in all cases and given by right-handed professionals.

RESULTS

All cases had otherwise successful cataract surgery (mean age 80.5 years; median pre-operative VA 6/18; median post-operative VA 6/9). The mean level of vertical diplopia was 7.2 prism dioptres (PD) in the primary position (range 2-25 PD). The left inferior rectus (IR) was paretic in 6 cases and restricted in 5 cases. The left superior rectus (SR) was not affected in any of the cases. The right IR was restricted in a single case. The right SR was paretic in 2 cases and restricted in a single case. None of the cases had clinical involvement of the oblique muscles. Eleven of the cases were managed successfully with prisms. Two of the cases required strabismus surgery.

CONCLUSIONS

The incidence of left eye extraocular muscle involvement was greater than right eye involvement, although this did not reach statistical significance (73% vs 27%; p = 0.075). This may be due to the more difficult access of right-handed individuals giving left eye peribulbar injections with the needle tract being directed more closely to the muscle cone. The IR muscle is more commonly affected than the SR (80% vs 20%; p = 0.019). An equal incidence of paretic and restricted rectus muscle pathology was found in this study (53% vs 47%; p = 0.818). The exact aetiology of muscle injury is unknown but could be due to direct muscle or nerve trauma, anaesthetic toxicity, periocular haemorrhage or a combination of these.

Cluster of diplopia cases after periocular anesthesia without hyaluronidase

PURPOSE

To describe a cluster of cases of iatrogenic diplopia after cataract surgery that occurred in 1998, when hyaluronidase was unavailable for use in periocular anesthetic regimens.

SETTING

The clinical practices of the authors.

METHODS

This study comprised a retrospective chart review.

RESULTS

Twenty-five cases of transient or permanent diplopia were reported. Of these, 13 eyes had retrobulbar and 10 had peribulbar injections; in 2 cases the injection technique was unknown. The inferior rectus was affected in 19 eyes; of these, 1 had a temporary palsy and 18 had permanent restriction. Temporary paresis developed in the lateral rectus in 5 cases and the superior rectus in 2. Eleven cases were submitted by 4 anterior segment surgeons, who collectively had a zero incidence of iatrogenic postoperative diplopia in the preceding 4 to 11 years of practice (approximately 6900 cases).

CONCLUSION

Hyaluronidase may be more important than previously suspected in preventing anesthetic-related damage to the extraocular muscles. The inferior rectus muscle is particularly vulnerable, presumably because of the injection technique.

Diplopia after cataract surgery

This article discusses clinical findings, differential diagnoses, management, and prognoses for patients with persistent diplopia after cataract extraction.

The National Survey of Local Anaesthesia for Ocular Surgery. I. Survey methodology and current practice

PURPOSE

To describe the current usage of the various techniques of local anaesthesia (LA) in the United Kingdom, and safety precautions taken.

METHODS

An observational study of practice of LA in the whole of the United Kingdom was carried out over 3 months in late 1996. Staff in all ophthalmology theatres in the National Health Service were invited to report every LA given for the purpose of intraocular surgery during the first week, and thereafter to report adverse events only.

RESULTS

Participation during the first week was calculated to be 72.8% overall. Anaesthesia techniques for intraocular surgery were: 70% LA alone, 5.8% LA with sedation and 24.2% general anaesthesia. LA techniques were: 65.6% peribulbar, 16.9% retrobulbar, 6.7% sub-Tenon's, 4.4% subconjunctival, 2.9% topical and 2.3% combinations. Of patients who were given LA, 96% were monitored, 84% had an anaesthetist available in theatres in case of a problem and intravenous access was established in 60%.

CONCLUSION

Local anaesthesia is frequently used for intraocular surgery in the United Kingdom. A variety of techniques are used, and safety precautions are taken in most cases.

Postanesthetic hypotropia: a unique syndrome in left eyes

PURPOSE

To investigate a recurring syndrome of postoperative hypotropia after cataract surgery performed under local anesthesia.

SETTING

Hawaiian Eye Center, Wahiawa, Hawaii, USA.

METHODS

Thirty-one left eyes in 2143 cataract surgeries developed postoperative hypotropia. Phacoemulsification and intraocular lens implantation were performed by one surgeon; the anesthetic (containing bupivacaine) was administered by one anesthesiologist who had treated 4200 patients without incident. We conducted epidemiologic, outcomes, and prevention studies to identify the etiology, evaluate hypotropia treatment, and test specific anesthetic techniques, respectively.

RESULTS

Changes in preoperative and intraoperative management and surgical methods were unsuccessful in preventing the hypotropia. In 55% of the cases, strabismus surgery was required and in 13%, prism glasses. Early recession of the inferior rectus and conjunctiva was successful. After repeated observations of the anesthetic technique, it was noted that the right-handed anesthesiologist misdirected the retrobulbar needle into the left orbit. This resulted in a change in the anesthetic technique, and there has been no incidence of postoperative hypotropia in 3000 surgeries.

CONCLUSION

We believe this syndrome resulted from mytoxicity or perimuscular inflammation, producing contracture hypotropia and restricted elevation of the globe. We propose the term postbupivacaine hypotropia for this chiefly left-sided syndrome.

Medial canthus (caruncle) single injection periocular anesthesia

We studied 151 consecutive patients scheduled for elective short-duration ophthalmic procedures to assess the efficacy of an alternative approach to periocular anesthesia. Single injection at the medial canthus was performed with a 25-gauge needle. The studied variables were: injected volume, onset time of the block, akinesia (scored on a 12-point scale), adequate surgical anesthesia (scored on a 5-point scale), and need for reinjection. The injected volume of local anesthetic solution was 8.6 +/- 1.7 mL. The onset time of anesthesia was 6.9 +/- 3.0 min, with an akinesia score of 11.6 +/- 1.1 (maximum 12). Additional reinjections were necessary in 14 cases (9.2%). There was a learning curve for the technique, with 8 of the additional injections being performed in the first 30 patients (26.6%), and 6 in the last 121 (4.9%). The surgical score recorded after surgery was 4.8 +/- 0.6 (maximum 5). There were no complications, including injury to the globe, optic nerve, or retina or orbital hematoma. Medial canthus single injection periocular anesthesia appears to be a promising alternative to the usual double injection peribulbar block.

Vertical strabismus after cataract surgery

PURPOSE

To compare anesthesia methods with resultant strabismus patterns in patients with vertical diplopia after cataract surgery.

METHODS

The authors analyzed 28 consecutive patients with acquired vertical diplopia after cataract surgery to identify the strabismus pattern. The method of anesthesia administration was available in 21 patients. Three orbital dissections with simulated retrobulbar blocks were performed on cadavers to ascertain the possibility of injuring the vertical rectus muscles at the time of injection.

RESULTS

Fifty percent of the involved muscles were overactive, 39 percent were restricted, and 11 percent were paretic. Eleven patients received retrobulbar, and ten received peribulbar anesthesia. The inferior rectus in 17 patients and the superior rectus muscle in 11 were involved. The odds of damaging the inferior rectus, as opposed to the superior rectus muscle, with peribulbar anesthesia was 4.8 times higher than with retrobulbar blocks. Cadaveric dissections showed the likelihood of direct needle injury to either vertical recti with retrobulbar blocks.

CONCLUSIONS

In this patient population, permanent vertical strabismus after cataract surgery results more often from overacting or restricted muscles than from primary muscle paresis. Both the superior and inferior recti can be injured with retrobulbar anesthesia, but peribulbar injections affect the inferior rectus muscle more frequently.

Ipsilateral hypertropia after cataract surgery

BACKGROUND

Reports of acquired strabismus caused by injection of local anesthetics during cataract surgery have increased recently. The authors proposed a mechanism to explain the occurrence of strabismus with apparent overactive muscles after cataract surgery.

METHODS

The authors studied 19 patients in whom strabismus developed after cataract surgery. Prism and cover test in the diagnostic positions of gaze and forced-duction testing were used to identify the affected muscles.

RESULTS

The deviation was greater in the field of action of the presumed tight muscle in 16 of 19 patients. An ipsilateral hypertropia with superior rectus muscle overaction subsequently developed in two patients with an initial hypotropia. An overaction of the ipsilateral lateral rectus muscle causing an exotropia developed in one patient with initially limited abduction.

CONCLUSIONS

Myotoxicity from direct injection of local anesthetics into an extraocular muscle probably causes transient paresis followed by segmental contracture of the involved muscle. Mild contractures result in strabismus with a motility pattern of an overactive muscle. Larger amounts of contracture lead to restrictive strabismus. The risk of strabismus may be decreased by administering the local anesthetic into sub-Tenon space using a blunt-tipped cannula when performing cataract surgery.

Inferior oblique muscle injury from local anesthesia for cataract surgery

BACKGROUND

Vertical rectus muscle injury is commonly cited as a cause of strabismus after cataract surgery. Injury to the inferior oblique muscle or nerve as a complication of cataract surgery has not been described previously.

METHODS

Four patients without pre-existing strabismus who had diplopia after cataract surgery were studied. Analysis included prism and cover testing, Lancaster red-green testing, and fundus torsion assessment.

RESULTS

Three patients had a delayed-onset hypertropia with fundus extorsion in the eye that underwent surgery, which is consistent with inferior oblique muscle overaction secondary to presumed contracture. The fourth patient had an immediate-onset hypotropia with fundus intorsion in the eye that underwent surgery, which is consistent with inferior oblique muscle paresis. Damage to a vertical rectus muscle or "unmasking" of a pre-existing superior oblique muscle paresis could not explain the history and findings in this group of four patients.

CONCLUSION

The inferior oblique muscle contracture observed in three patients may have been caused by local anesthetic myotoxicity, whereas the paresis observed in one patient may have been due to mechanical trauma or anesthetic toxicity directly to the nerve innervating the muscle. Inferior oblique muscle or nerve injury should be considered as another possible cause of postoperative strabismus, especially when significant fundus torsion accompanies a vertical deviation.

Inferior rectus muscle overaction after cataract extraction

PURPOSE/METHODS

I reviewed the motility of two patients who had binocular vertical diplopia after cataract operations with peribulbar anesthesia.

RESULTS/CONCLUSIONS

The binocular diplopia in these patients was a result of inferior rectus muscle overaction in the absence of restriction or weakness of the antagonist muscle. The mechanism could be related to myotoxicity of the anesthetic agents.

Persistent binocular diplopia following cataract surgery: aetiology and management

We studied all patients referred to the orthoptic department with binocular diplopia following cataract surgery between January 1991 and June 1993. Persistence of diplopia for a minimum of 3 months after cataract surgery was required for inclusion in the study. Eighty-one patients (2% of all patients who underwent cataract surgery during this time) satisfied the entry criteria. The patients fell into two groups: non-traumatic and traumatic cataracts. Horizontal deviations were seen in 24 patients. Vertical deviations were seen in 8 patients and a combined horizontal and vertical deviation was seen in 49 patients. Fresnel prisms were used to manage the diplopia in 58 patients. Of these, 48 patients in the non-traumatic group regained binocular single vision with this prism while 10 in the traumatic group benefited. Mechanical and sensory causes are discussed.