Ocular explosions from periocular anesthetic injections: a clinical, histopathologic, experimental, and biophysical study

Biomechanics of open-globe injury: a review

Open-globe injury is a common cause of blindness clinically caused by blunt trauma, sharp injury, or shock waves, characterised by rupture of the cornea or sclera and exposure of eye contents to the environment. It causes catastrophic damage to the globe, resulting in severe visual impairment and psychological trauma to the patient. Depending on the structure of the globe, the biomechanics causing ocular rupture can vary, and trauma to different parts of the globe can cause varying degrees of eye injury. The weak parts or parts of the eyeball in contact with foreign bodies rupture when biomechanics, such as external force, unit area impact energy, corneoscleral stress, and intraocular pressure exceed a certain value. Studying the biomechanics of open-globe injury and its influencing factors can provide a reference for eye-contact operations and the design of eye-protection devices. This review summarises the biomechanics of open-globe injury and the relevant factors.

Patient and surgeon comfort in vitreoretinal surgery performed with Sub-Tenon's Anaesthesia

Background. Since Stevens first introduced Sub-Tenon's anaesthesia into cataract surgery it has shown itself to be a safe, simple, and efficient technique. The advantages of this type of block are comparable to those of sharp needle anaesthesia and complications are minimal. Several studies have found that the anaesthesia provided by Sub-Tenon's capsule injection is as good as or better for cataract surgery than that achieved by retrobulbar injection, but the efficacy of Sub-Tenon's block in vitreoretinal surgery is less well established. Methods. We performed 50 vitreoretinal procedures; 50 eyes received a Sub-Tenon's injection of a 5 ml mixture (50:50) of lidocaine and ropivacaine, plus 15 IU mL-1 of Hyaluronidase. Results. In 45 cases, only one injection was needed to achieve sufficient anaesthesia and akinesia; in 5 cases a second injection was performed five minutes after the first. Mean surgical time was 45.7 minutes. After surgery, each patient was asked to indicate his value on the VAS pain scale. Mean VAS degree was 2.4. In 7 cases, VAS was > 3 and the pain was successfully managed with the administration of paracetamol in the postoperative period. No light perception was detected at the end of surgery in 33 patients. All cases with 2 injections had no light perception at the end of surgery. Anaesthesia lasted throughout the surgery in all cases. The surgeon performed all surgery comfortably and with no difficulty. Conclusions. According to our experience and to a growing body of evidence, Sub-Tenon's anaesthesia appears to be a safe, simple, versatile, and effective technique and should be considered as a real alternative method of anaesthesia in vitreoretinal surgery.

Ocular complications of perioperative anesthesia: a review

Ocular complications associated with anesthesia in ocular and non-ocular surgeries are rare adverse events which may present with clinical presentations vacillating between easily treatable corneal abrasions to more serious complication such as irreversible bilateral vision loss. In this review, we outline the different techniques of anesthetic delivery in ocular surgeries and highlight the incidence and etiologies of associated injuries. The changes in vision in non-ocular surgeries are mistaken for residual sedation or anesthetics, therefore require high clinical suspicion on part of the treating ophthalmologists, to ensure early diagnosis, adequate and swift management especially in surgeries such as cardiac, spine, head and neck, and some orthopedic procedures, that have a comparatively higher incidence of ocular complications. In this article, we review the literature for reports on the clinical incidence of different ocular complications associated with anesthesia in non-ocular surgeries and outline the current understanding of pathophysiological processes associated with these adverse events.

PFOh No: Spontaneous Globe Rupture During Injection of Perfluoro-n-Octane (PFO) During Retinal Detachment Repair

The authors describe a case of spontaneous globe rupture during instillation of perfluoro-n-octane (PFO) during retinal surgery. A 71-year-old male with a macular-involving rhegmatogenous retinal detachment underwent pars plana vitrectomy. During instillation of PFO manually on a single-bore cannula by the assisting resident, spontaneous globe rupture occurred superotemporally in an area with no visible underlying structural abnormalities. Factors that led to this complication include the use of single-bore cannula, error in judgment of resistance during PFO injection, and inexperience. This is the first report of this complication without an identifiable structural abnormality predisposing patient to perforation.

Displacement of crystalline lens into the sub-conjunctival space following periocular anesthesia

A 65-year-old female presented with loss of vision and a mass in her right eye after periocular anaesthesia for cataract surgery in a camp. She was found to have a nasal subconjunctival mass, which was confirmed to contain the crystalline lens after surgical exploration, along with a superior perilimbal suspected scleral rupture. There was accompanying vitreous haemorrhage, retinal detachment and subretinal haemorrhage that was managed by pars plana vitrectomy. Post operatively, she achieved a best corrected visual acuity of 20/80 that was maintained till 6 months follow up. Globe rupture and subconjunctival lens extrusion in the setting of inadvertent globe penetration during periocular anesthesia is a rare complication. In the absence of medical records pertaining to the primary event, this clinical presentation posed a diagnostic challenge. Timely and appropriate management led to an acceptable visual and anatomical outcome in this unfortunate and devastating scenario.

Eye rubbing type and prevalence including contact lens 'removal-relief' rubbing

BACKGROUND

Eye rubbing is commonly associated with keratoconus and may contribute to disease onset and progression. Verbal counselling to avoid rubbing may not be successful and adverse consequences of rubbing, which occurs on contact lens removal may be more serious. This study examines the prevalence of 'removal-relief' rubbing and its potential consequences.

METHODS

Rubbing histories were recorded for contact lens wearing normal and keratoconic patients as well as for normal non-contact lens wearers. Analogue scaled responses were used to identify and compare abnormal rubbing habits.

RESULTS

Contact lens wearing patients (both with and without keratoconus) reported significantly more rubbing before contact lens insertion (p < 0.05) compared to non-contact lens wearers. Eye rubbing after contact lens removal ('removal-relief' rubbing) was found to be significantly more prevalent among contact lens-wearing keratoconic patients compared to contact lens-wearing non-keratoconic patients (p < 0.001 in both cases).

CONCLUSIONS

Rubbing-related trauma occurring before contact lens insertion may predispose the cornea to wound healing activities and greater levels of adverse response to contact lens wear. Such adverse responses could predispose the cornea to greater trauma, which occurs in response to rubbing on removal of contact lenses. Strong counselling to avoid eye rubbing is often not an adequate form of management for a significant number of patients with keratoconus. Evidence of relapses indicates the need for better methods of counselling and for them to be repeated regularly. Apart from keratoconus, any other keratectasia, corneal disease or wound healing (including post-surgical) may increase susceptibility to corneal rubbing trauma. Such cases also appear to warrant counselling on avoidance of rubbing.

Unusual ocular injury by an acupuncture needle

PURPOSE

To educate ophthalmologists on the potential dangers of periocular acupuncture and to describe an unusual mechanism of retinal injury.

METHODS

A 42-year-old woman who presented with blurred central vision and loss of peripheral vision. Her medical history was significant for hemifacial spasms related to a facial nerve injury, for which she had sought treatment. Clinical examination showed vertically oriented subretinal track measuring 12 mm in length, contiguous to the macula, with normal optic nerve appearance and foveal reflexes. Spectral domain optical coherence tomography showed a full-thickness perforation of the neurosensory retina at the inferior retinal arcade. Visual field testing 3 weeks after her injury showed 90% loss of her nasal hemifield. Electroretinography performed 8 weeks postinjury showed a 50% decrease in the right B-wave. Multifocal electroretinography showed a mild decrease in the recording of the right eye versus that of the left eye.

CONCLUSION

Based on the history and clinical findings, the acupuncture needle penetrated the inferior globe and created a subretinal track. The particular location of the needle entry into the eye and the extreme malleability of the acupuncture needle created a long subretinal track. Ophthalmologists should be familiar with the ocular injuries caused by periocular acupuncture therapies.

Eye injury risk from water stream impact: biomechanically based design parameters for water toy and park design

PURPOSE

Interactive water displays are becoming increasingly popular and can result in direct eye contact. Therefore, the purpose of this study is to investigate eye injury risk from high speed water stream impacts and to provide biomechanically based design parameters for water toys and water park fountains.

METHODS

An experimental matrix of 38 tests was developed to impact eight porcine eyes with water streams using a customized pressure system. Two stream diameters (3.2 mm and 6.4 mm) were tested at water velocities between 3.0 m/s and 8.5 m/s. Intraocular pressure was measured with a small pressure sensor inserted through the optic nerve and used to determine the injury risk for hyphema, lens dislocation, retinal damage, and globe rupture for each impact.

RESULTS

Experimental water stream impacts created a range of intraocular pressures between 3156 mmHg and 7006 mmHg (61 psi to 135 psi). Injury risk varied between 4.4%-27.8% for hyphema, 0.0%-3.0% for lens dislocation, and 0.1%-3.3% for retinal damage. All tests resulted in 0.0% injury risk for globe rupture. The two water stream diameters did not result in significantly different water stream velocities (P = 0.32); however, the variation in water stream diameter did result in significantly different intraocular pressures (P = 0.03) with higher pressures for the 6.4 mm stream.

CONCLUSIONS

This is the first study to experimentally measure intraocular pressure from high speed water stream impacts and quantify the corresponding eye injury risk. It is recommended that toy water guns and water park fountains use an upper threshold of 8.5 m/s for water stream velocities to minimize the risk of serious acute eye damage from impacts.

Bilateral subcutaneous emphysema from pressurized infusion during pars plana vitrectomy: a case report

OBJECTIVES

To report a case of extensive subcutaneous emphysema introduced during vitrectomy while using an advanced feedback-controlled pressurized infusion system.

METHODS

Clinical case report of a 56-year-old woman undergoing pars plana vitrectomy for rhegmatogenous retinal detachment of the left eye. The clinical and radiologic findings of the patient's eyes were documented. The mechanisms of feedback-controlled pressurized infusion devices were reviewed to explain the adverse events. A search of PubMed was conducted to look for any similar cases and/or discussion.

RESULTS

In this surgical case, vitrectomy was completed with air-fluid exchange and a formed anterior chamber was observed with an estimated pressure of high teens to low 20s by the surgeon. After the undraping, the patient was noted to have severe facial crepitus extending to the clavicles. Immediate chest X-ray was done, followed by computed tomography, confirming orbital and subcutaneous emphysema, as well as the presence of perfluoro-N-octane in the left orbit.

CONCLUSION

Integrated pressurized infusion devices using feedback sensors allow for a sophisticated method of maintaining intraocular pressure and globe formation. However, inadvertent or occult globe rupture may lead to disruption of feedback control and subsequent high rates of infusion. As the infused substances exit the site of rupture, they can lead to extensive extraocular gas or fluid accumulation, and we report a case of severe bilateral subcutaneous emphysema as a result.

Are ocular injection anesthetic blocks obsolete? Indications and guidelines

PURPOSE OF REVIEW

In this era of topical anesthesia for ocular surgery, anesthetic ocular blocks are still important when profound anesthesia and akinesia are required. Although injection ocular blocks, retrobulbar and peribulbar anesthesia, have been supplanted for most ocular surgery in many centers by sub-Tenon's irrigation block because of its superior safety profile, still worldwide, injection blocks remain popular.

RECENT FINDINGS

We present here the results of a survey of the literature published over the last 5 years to assess current international preferences for ocular anesthesia injection blocks. We discuss the reasons why sub-Tenon's anesthesia is not more universally popular and advocate for its greater acceptance because of safety. Specific narrow indications for performing injection ocular blocks are presented. Also, guidelines for performing retrobulbar anesthesia which reduce the risk of serious ocular complications are provided as well as our rationale for preferring retrobulbar to peribulbar anesthesia.

SUMMARY

Sub-Tenon's block should be performed in the operating theatre in preference to retrobulbar or peribulbar anesthesia except for limited indications. When injection ocular block is deemed necessary, we feel that retrobulbar anesthesia with the technique described may be safer than peribulbar anesthesia.

Evaluation of Different Projectiles in Matched Experimental Eye Impact Simulations

Eye trauma results in 30,000 cases of blindness each year in the United States and is the second leading cause of monocular visual impairment. Eye injury is caused by a wide variety of projectile impacts and loading scenarios with common sources of trauma being motor vehicle crashes, military operations, and sporting impacts. For the current study, 79 experimental eye impact tests in literature were computationally modeled to analyze global and localized responses of the eye to a variety of blunt projectile impacts. Simulations were run with eight different projectiles (airsoft pellets, baseball, air gun pellets commonly known as BBs, blunt impactor, paintball, aluminum, foam, and plastic rods) to characterize effects of the projectile size, mass, geometry, material properties, and velocity on eye response. This study presents a matched comparison of experimental test results and computational model outputs including stress, energy, and pressure used to evaluate risk of eye injury. In general, the computational results agreed with the experimental results. A receiver operating characteristic curve analysis was used to establish the stress and pressure thresholds that best discriminated for globe rupture in the matched experimental tests. Globe rupture is predicted by the computational simulations when the corneoscleral stress exceeds 17.21 MPa or the vitreous pressure exceeds 1.01 MPa. Peak stresses were located at the apex of the cornea, the limbus, or the equator depending on the type of projectile impacting the eye. A multivariate correlation analysis revealed that area-normalized kinetic energy was the best single predictor of peak stress and pressure. Additional incorporation of a relative size parameter that relates the projectile area to the area of the eye reduced stress response variability and may be of importance in eye injury prediction. The modeling efforts shed light on the injury response of the eye when subjected to a variety of blunt projectile impacts and further validate the eye model’s ability to predict globe rupture. Results of this study are relevant to the design and regulation of safety systems and equipment to protect against eye injury.

Injection intravitréenne accidentelle de lidocaïne au cours d’une anesthésie palpébrale : toxicité rétinienne de la lidocaïne ?

INTRODUCTION

We report an atypical case of scleral perforation due to an inadvertent intravitreal lidocaine injection following palpebral anesthesia. We discuss the management of this rare complication and focus on the transient lidocaine toxicity on human retina.

OBSERVATION

A 29-year-old man presented with unilateral decreased vision during a lower right palpebral anesthetic injection for a chalazion removal procedure. The patient's vision was light perception. Examination revealed intraocular pressure at 55 mmHg, a wound of the posterior crystalloid, an intraocular gas bubble, and a central retinal artery spasm. On ERG, the b wave was decreased. The central retinal artery spasm resolved with prompt reduction of hypertony. Twenty-four hours later, the vision was 6/10 and the ERG showed an increased b wave activity. No clinical retinal toxicity of lidocaine was observed. Only a subcapsular cataract was observed, which had caused the loss of vision.

CONCLUSION

This case confirms that lidocaine is well tolerated by the retina and reminds us that superficial palpebral anesthetic injection should be done with great caution.

Treatment of thyroid associated ophthalmopathy with periocular injections of triamcinolone

AIM

To evaluate the efficacy of periocular triamcinolone acetonide for the treatment of thyroid associated ophthalmopathy (TAO), and the presence of ocular or systemic adverse effects.

METHODS

A multicentre prospective pilot study was performed on patients diagnosed with Graves' ophthalmopathy less than 6 months before entry to the study. Patients were admitted to the study and were randomised into two groups: treatment and control. The treatment group received four doses of 20 mg of triamcinolone acetate 40 mg/ml in a peribulbar injection to the inferolateral orbital quadrant. Both groups were evaluated by measuring the area of binocular vision without diplopia on a Goldmann perimeter and the size of the extraocular muscles on computed tomography (CT) scans. Ophthalmological and systemic examinations were done to rule out ocular and systemic adverse effects. Follow up was 6 months for both groups.

RESULTS

50 patients were eligible for the study. 41 patients completed the study. There was an increase in the area of binocular vision without diplopia in the treatment group (Sigma initial: mean 231.1 (SD 99.9) and final absolute change, mean 107.1 (SD 129.0)) compared to the control group (Sigma initial: mean 350.7 (SD 86.5) and final absolute change, mean -4.5 (SD 67.6)). The sizes of the extraocular muscles were reduced in the treatment group (mean (inferior rectus initial values): 1.3 (0.7), final percentage change: -13.2 (25.7), medial rectus initial values: 1.2 (0.6), final percentage change: -8.2 (20.7), superior rectus-levator palpebrae initial values: 1.2 (0.6), final percentage change: -9.5 (29.1), lateral rectus initial values: 1.0 (0.4), final percentage change: -11.5 (20.6)) compared to the control group (inferior rectus initial values: 0.9 (0.3), final percentage change: -4.0 (21.5), medial rectus initial values: 0.9 (0.3), final percentage change: 0.6 (22.4), superior rectus-levator palpebrae initial values: 0.9 (0.3), final percentage change: 12.5 (37.5), lateral rectus initial values: 0.9 (0.4), final percentage change: -0.5 (31.6)). Both measurements (degree of diplopia and muscle thickness) were statistically significant between groups (initial - final). No systemic or ocular adverse effects were found.

CONCLUSIONS

Triamcinolone administered as a periocular injection is effective in reducing diplopia and the sizes of extraocular muscles in TAO ophthalmopathy of recent onset. This form of treatment is not associated with systemic or ocular side effects.

How long can donor sclera be safely stored?

PURPOSE

To determine whether after prolonged storage of sclera in glycerin, there is any bacteriologic contamination that will reactivate, whether reconstituted sclera retains its tensile strength, and whether sclera retains its microstructural integrity.

METHODS

Sixty-six scleral shells stored in glycerin for 9 to 19 years, as well as 11 controls stored for 6 months to 4 years, were studied by cutting a small wedge of tissue from the anterior margin of each and directly inoculating into thioglycolate broth, cutting an equatorial ring and determining its break strength using a tensiometer, and cutting a small piece from the remaining posterior portion and examining by scanning electron microscopy.

RESULTS

After such prolonged storage, bacteriologic contamination was not detected, tensile strength generally increased with increasing duration of storage, and ultrastructural integrity was maintained on scanning electron microscopy.

CONCLUSIONS

This study suggests that storage of scleral shells can be safely prolonged; we hope this can facilitate an increased supply of donated sclera to patients and surgeons.

Techniques for managing common complications of cataract surgery

Cataract surgery has evolved dramatically over the last two decades, largely as a result of technological advances. As a result, visual outcomes and patient convalescence have improved significantly. A second consequence of increased instrumentation and technology, however, is increased complexity of cataract surgery and the advent of complications unique to these advances. Cataract surgeons must be aware and capable of managing the many possible adverse events that can occur during cataract surgery. This review identifies many of the common complications of cataract surgery, describes methods to avoid these complications and discusses techniques to address complications that do occur. It is the ability to avoid, quickly identify, and properly manage complications that defines the accomplished cataract surgeon.

The Law of Laplace and its relevance to contemporary medicine and rehabilitation

OBJECTIVE

To show that the Law of Laplace is not only a historical curiosity but also remains relevant to our daily teaching and clinical activities.

DATA SOURCES

Comprehensive MEDLINE (1960-2000) and CINAHL (1982-2000) computer literature searches performed by using key words such as Law of Laplace, Laplace, and Laplace relationship. Additional references were obtained from the bibliographies of the selected articles. Supplementary searches were also made by using various Internet search engines.

STUDY SELECTION

Primary references were used whenever possible.

DATA EXTRACTION

A single reviewer assessed all references and extracted information relevant to the Law of Laplace.

DATA SYNTHESIS

Although the Law of Laplace is attributed to Pierre Simon de Laplace, Laplace may not deserve the credit for the discovery. Nevertheless, the relationship (T [tension] alpha P [pressure] R [radius]) is easily derived and improves our understanding of the physiologic basis of many of our medical and rehabilitation practices. For example, the Law provides an insight into the mechanism of action of compression garments and lumbosacral orthoses, an understanding of the role of uterine muscle during delivery, and a reason why cesarean sections are made in the lower uterus. In addition, the Law explains many aspects of such diverse phenomena as penile erection, compartment syndromes, and peripheral edema. Perhaps most important, the Law explains the basis of many common medical practices that we use to promote bladder emptying, to control edema, and to plan surgery.

CONCLUSION

The Law of Laplace explains the mechanism of a wide range of physiologic phenomena. Unfortunately, even though it was developed about 200 years ago, the insights it provides us are often underused. More consideration of its implications can improve our clinical practice, our teaching, and our enjoyment of medicine.

Ocular explosion after peribulbar anesthesia

We report 3 cases of globe rupture after peribulbar anesthesia. We discuss the predisposing factors, presenting features, and visual outcome after this complication. Globe explosion is a severe complication of inadvertent intraocular injection during peribulbar anesthesia. Visual outcome after vitrectomy is generally poor; however, cases that do not develop a retinal detachment may achieve good results.

Measure for measure

Shakespeare's play Measure for Measure colorfully illustrates a concept that is relevant to the testimonies given by the medical expert witness in the courtroom. The expert should not ask the jury to hold the defendant physician to a higher standard than that actually practiced by an acceptable reasonable minority of the defendant's peers under similar circumstances. Two cases are presented.