Altered globe dimensions of axial myopia as risk factors for penetrating ocular injury during peribulbar anaesthesia

Inadvertent triple globe penetration during peribulbar anesthesia

Inadvertent globe perforation following peribulbar anesthesia can lead to unpleasant experiences if not identified early and managed appropriately. We present the case of a 75-year-old female who came with decreased vision in the left eye (LE) following cataract surgery under peribulbar block. Her visual acuity in the right eye (RE) was 6/24 and LE was 6/75. Fundus examination of LE showed vitreous hemorrhage with localized subretinal hemorrhage along the inferotemporal arcade suggestive of globe perforation. Optical coherence tomography (OCT, Spectralis. Heidelberg imaging, Germany) scan across the perforation site showed subretinal hemorrhage and full-thickness retinal tear. On follow-up, two more focal points of retinal whitening were noted in the inferotemporal equatorial region. The patient was kept under close monitoring, and 4 weeks later, vision improved to 6/9 and barrage laser was done around the perforation sites. Serial OCT scans and close follow-up in iatrogenic globe perforation can result in good visual outcomes.

Anaesthetic considerations for the surgical management of ocular hypotony in adults

Ocular hypotony can occur from many causes, including eye trauma, ophthalmic surgery and ophthalmic regional anaesthesia-related complications. Some of these patients require surgical intervention(s) necessitating repeat anaesthesia. While surgical management of these patients is well described in the literature, the anaesthetic management is seldom discussed. The hypotonous eye may also have altered globe anatomy, meaning that the usual ocular proprioceptive feedbacks during regional ophthalmic block may be altered or lost, leading to higher risk of inadvertent globe injury. In an 'open globe' there is a risk of sight-threatening expulsive choroidal haemorrhage as a consequence of ophthalmic block or general anaesthesia. This narrative review describes the physiology of aqueous humour, the risk factors associated with ophthalmic regional anaesthesia-related ocular hypotony, the surgical management, and a special emphasis on anaesthetic management. Traumatic hypotony usually requires urgent surgical repair, whereas iatrogenic hypotony may be less urgent, with many cases scheduled as elective procedures. There is no universal best anaesthetic technique. Topical anaesthesia and regional ophthalmic block, with some technique modifications, are suitable in many mild-to-moderate cases, whilst general anaesthesia may be required for complex and longer procedures, and severely distorted globes.

A Three-Dimensional-reconstruction-based study on the ocular volume of Chinese children with high myopia

BACKGROUND

Highly myopic eyes differ in morphology from emmetropic eyes, and the correct estimation of the vitreous volume is difficult. To explore an effective method to estimate ocular volume using refractive factors in children.

METHODS

This is a retrospective study of children with high myopia who visited the Shenzhen Shekou People's Hospital (July-December 2018) before undergoing posterior scleral reinforcement surgery. Data on refractive factors and ocular 3D reconstruction imaging based on high-end CT were collected for linear correlation and linear regression analyses.

RESULTS

Ten patients (20 eyes) were included. There are nine males and one female. They were 4 to 12 years of age. The spherical equivalent ranges from + 0.25 to -20.00 D. The cylindrical equivalent ranges from - 0.50 to -6.25 D. The AL(axial length, AL) ranges from 21.78 to 33.90 mm. The corneal curvature (mean) ranges from 42.44 to 46.75. The 3D reconstruction of the CT images shows that the ocular volume ranges from 4.591 to 10.988 ml. The ocular volume of the 20 eyes decreases with the increase of diopter and total curvature, both presenting a linear trend, with the Pearson correlation coefficients being - 0.776 (P < 0.001) and - 0.633 (P = 0.003), respectively. The ocular volume of the 20 eyes increases with the increasing AL, also presenting a linear trend, with the Pearson correlation coefficient being 0.939 (P < 0.001).

CONCLUSIONS

In children, the ocular volume is negatively and linearly correlated with the diopter and curvature, and positively and linearly correlated with the AL.

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.

Sub-Tenon's anaesthesia for modern eye surgery-clinicians' perspective, 30 years after re-introduction

Sub-Tenon's block (STB) is a good technique of local anaesthesia for many types of eye surgery. It has a relatively good risk profile, in that sight- and life-threatening complications appear to be extremely rare. STB has gained popularity in the last three decades, with refinements including different types of blunt metal cannula, plastic cannulae and 'incisionless' approaches. Usage of STB varies significantly across the globe. This narrative review documents the historical evolution of STB techniques, anatomical and physiological considerations, its utility and suitability, complications, explores the current practice and possible future applications.

Management of iatrogenic globe perforation during peribulbar anesthesia with submacular hemorrhage

A patient with an amblyopia and poor vision in the fellow eye experienced iatrogenic globe perforation during peribulbar anesthesia for cataract surgery. The injection and surgery were immediately aborted. Visual acuity was hand motion, and retinal examination revealed retinal detachment, hemorrhagic choroidal detachment, and submacular hemorrhage. These were initially managed medically until the hemorrhagic choroidal detachment resolved and afterward by combined phacoemulsification with pars plana vitrectomy, subretinal recombinant tissue plasminogen activator, and gas tamponade. Two weeks post operative, the patient achieved the best-corrected visual acuity of around 20/200, which after 1 year of follow-up improved to 20/70.

Do oblate eyeballs exist? A rare case of rhegmatogenous retinal detachment in an elliptical globe

A patient, being a moderate myope with an axial length of 24.71 mm, presented to us with a fresh rhegmatogenous retinal detachment and marked peripheral chorioretinal degeneration. Difficulty in maneuvering with the standard 23 gauge vitrectomy cutter, inability to identify the break due to poor peripheral contrast, inadequate laser uptake, and an unusual large silicon oil fill (7.3 ml) were a few findings raising suspicion. Postoperative ocular ultrasonography showed an oblate eyeball with a relatively longer oblique axis (26.1 mm) as compared to the axial length confirming our suspicion. Oblateness should be suspected when the chorioretinal degenerations are more marked in the periphery as compared to the posterior pole. Intraoperative difficulties should be kept in mind while operating such cases.

Preoperative Preparation and Anesthesia for Trabeculectomy

Preoperative preparation should improve the likelihood of successful trabeculectomy surgery. The team can reconsider the appropriateness of the proposed surgery, and steps can be taken to maximize the chance of a good outcome. For example, adjustments to anti-hypertensive or anti-coagulant medications may be made, and topical ocular medications adjusted. Choice of anesthesia technique is of particular relevance to the trabeculectomy patient. Some anesthesia techniques are more likely to have serious complications, and glaucoma patients may be at higher risk of some sight-threatening complications, because the optic nerve is already damaged and vulnerable. Posterior placement of local anesthesia (retrobulbar, peribulbar, posterior sub-Tenon's techniques) could potentially damage the optic nerve, and thereby cause "wipe-out" of vision. Anesthesia technique may influence the likelihood of vitreous bulge and surgical difficulty. Regarding long-term control of intraocular pressure, there is no good evidence to indicate that any particular anesthesia technique is better than another. There is little high-quality evidence on this topic. The author's preferred technique for trabeculectomy is subconjunctival-intracameral anesthesia without sedation. How to cite this article: Eke T. Preoperative Preparation and Anesthesia for Trabeculectomy. J Curr Glaucoma Pract 2016; 10(1):21-35.

Ophthalmic regional blocks: management, challenges, and solutions

In the past decade ophthalmic anesthesia has witnessed a major transformation. The sun has set on the landscape of ophthalmic procedures performed under general anesthesia at in-hospital settings. In its place a new dawn has ushered in the panorama of eye surgeries conducted under regional and topical anesthesia at specialty eye care centers. The impact of the burgeoning geriatric population is that an increasing number of elderly patients will present for eye surgery. In order to accommodate increased patient volumes and simultaneously satisfy administrative initiatives directed at economic frugality, administrators will seek assistance from anesthesia providers in adopting measures that enhance operating room efficiency. The performance of eye blocks in a holding suite meets many of these objectives. Unfortunately, most practicing anesthesiologists resist performing ophthalmic regional blocks because they lack formal training. In future, anesthesiologists will need to block eyes and manage common medical conditions because economic pressures will eliminate routine preoperative testing. This review addresses a variety of topical issues in ophthalmic anesthesia with special emphasis on cannula and needle-based blocks and the new-generation antithrombotic agents. In a constantly evolving arena, the sub-Tenon's block has gained popularity while the deep angulated intraconal (retrobulbar) block has been largely superseded by the shallower extraconal (peribulbar) approach. Improvements in surgical technique have also impacted anesthetic practice. For example, phacoemulsification techniques facilitate the conduct of cataract surgery under topical anesthesia, and suture-free vitrectomy ports may cause venous air embolism during air/fluid exchange. Hyaluronidase is a useful adjuvant because it promotes local anesthetic diffusion and hastens block onset time but it is allergenic. Ultrasound-guided eye blocks afford real-time visualization of needle position and local anesthetic spread. An advantage of sonic guidance is that it may eliminate the hazard of globe perforation by identifying abnormal anatomy, such as staphyloma.

Management of retinal detachment in block related globe perforation with pneumatic retinopexy

Retinal detachment after ocular perforation related to local anesthesia is a common complication, which is usually associated with a poor prognosis despite complex vitreoretinal surgical procedures. We report a case of 62-year-old male with cataract surgery done 4 weeks back with nasal retinal detachment with a posterior break. Pneumatic retinopexy was performed and laser barrage of the breaks was done the next day when the retina got attached. A vision of 20/30 was achieved at the end of 2 months. To the best of our knowledge, this is a first case report in literature where pneumatic retinopexy was used to manage a retinal detachment caused by block-related perforation.

Eye shape and retinal shape, and their relation to peripheral refraction

PURPOSE

  We provide an account of the relationships between eye shape, retinal shape and peripheral refraction.

RECENT FINDINGS

  We discuss how eye and retinal shapes may be described as conicoids, and we describe an axis and section reference system for determining shapes. Explanations are given of how patterns of retinal expansion during the development of myopia may contribute to changing patterns of peripheral refraction, and how pre-existing retinal shape might contribute to the development of myopia. Direct and indirect techniques for determining eye and retinal shape are described, and results are discussed. There is reasonable consistency in the literature of eye length increasing at a greater rate than height and width as the degree of myopia increases, so that eyes may be described as changing from oblate/spherical shapes to prolate shapes. However, one study indicates that the retina itself, while showing the same trend, remains oblate in shape for most eyes (discounting high myopia). Eye shape and retinal shape are not the same and merely describing an eye shape as being prolate or oblate is insufficient without some understanding of the parameters contributing to this; in myopia a prolate eye shape is likely to involve both a steepening retina near the posterior pole combined with a flattening (or a reduction in steepening compared with an emmetrope) away from the pole.

SUMMARY

  In the recent literature, eye and/or retinal shape have often been inferred from peripheral refraction, and, to a lesser extent, vice versa. Because both the eye's optics and the retinal shape contribute to the peripheral refraction, and there is large variation in the latter, this inference should be made cautiously. Recently retinal shape has been measured independent of optical methods using magnetic resonance imaging. For further work on retinal shape, determining the validity of cheaper alternatives to magnetic resonance techniques is required.

Percaruncular single injection peribulbar anaesthesia in patients with axial myopia for phacoemulsification

BACKGROUND

Myopia has been identified as a risk factor for globe perforation during regional anaesthesia for cataract surgery. We conducted this study to evaluate efficacy of single injection percaruncular peribulbar anaesthesia for phacoemulsification in patients with axial myopia.

METHODS

Eighty patients with axial myopia received percaruncular peribulbar anaesthesia and were evaluated for incidence of major or minor complications. Also surgeon and patients' satisfaction and their comment on operative conditions were noted.

RESULTS

Of the 80 patients 51 patients had posterior staphylomas. About three quarters of the patients developed adequate akinesia in 10 min. Remaining 25% received second injection with the same technique but with less volume after which the percent of patients with adequate akinesia rose to 91%. Adequate analgesia developed in almost all patients and only in one patient, intravenous analgesia was necessary to complete the operation. All operations were completed uneventfully. No perforations or penetrations were recorded and no other major complications were encountered. About 97% of the surgeons and 96% of the patients found the operative conditions satisfactory.

CONCLUSION

Using single injection percaruncular peribulbar local anaesthesia for phacoemulsification in patients with axial myopia is an effective technique.

A review of directions of gaze during intraocular anesthetic blocks

Safety of orbital blocks depends on operator and patient factors. Among the patient factors, the direction of gaze is important. Certain ocular structures move when the gaze is shifted. These may veer into the path of the needle, setting the stage for injury. The optic nerve with its accompanying artery swerves medially during abduction, direct up gaze, and superolateral and inferolateral gazes. These gazes are therefore risky for medial compartment blocks. In a superomedial gaze, the optic nerve shifts down and out and is likely to be injured during inferolateral needle blocks. Primary gaze is considered to be the safest for akinetic sharp needle blocks. "Tethering tests" involving extremes of gazes are dangerous. The superomedial, superior, superolateral, and inferomedial routes are perilous in all gazes. The superolateral gaze during classic Steven's sub-Tenon's block brings the optic nerve forward, rendering it vulnerable. Complications can be reduced by avoiding deep blind dissection and posterior injections.

Needle-based blocks for the 21st century ophthalmology

PURPOSE

This paper reviews history of the needle orbital blocks used in the earlier centuries and how they have evolved towards safer anaesthesia in the modern clinical practice.

METHODS

Material is derived from literature searches from major ophthalmic and anaesthetic journals on the use of orbital needle blocks over earlier centuries.

RESULTS

Needle-based anaesthetic techniques were described shortly after the invention of reliable medical needles. Atkinson popularized the classical retrobulbar block in a series of papers published in the early 20th century. This technique,which utilises a relatively long needle inserted towards the apex of the muscle cone behind the globe, has been criticized by some as unsuitable for modern 21st century ophthalmic surgery because of the extremely rare potential for serious complications. Satisfactory anaesthesia and akinesia can be obtained with short sharp or dull needles with slightly higher volumes of local anaesthetic agent placed in the farthest inferotemporal quadrant.

CONCLUSION

Aside from relative safety, modern needle blocks offer the advantage of lid akinesia without a need for a second injection for the seventh nerve that is often performed con-comitantly with retrobulbar block.

Effects of form deprivation on peripheral refractions and ocular shape in infant rhesus monkeys (Macaca mulatta)

PURPOSE

To determine whether visual experience can alter ocular shape and peripheral refractive error pattern, the authors investigated the effects of form deprivation on refractive development in infant rhesus monkeys.

METHODS

Monocular form deprivation was imposed in 10 rhesus monkeys by securing diffuser lenses in front of their treated eyes between 22 +/- 2 and 163 +/- 17 days of age. Each eye's refractive status was measured longitudinally by retinoscopy along the pupillary axis and at 15 degrees intervals along the horizontal meridian to eccentricities of 45 degrees . Control data for peripheral refraction were obtained from the nontreated fellow eyes and six untreated monkeys. Near the end of the diffuser-rearing period, the shape of the posterior globe was assessed by magnetic resonance imaging. Central axial dimensions were also determined by A-scan ultrasonography.

RESULTS

Form deprivation produced interocular differences in central refractive errors that varied between +2.69 and -10.31 D (treated eye-fellow eye). All seven diffuser-reared monkeys that developed at least 2.00 D of relative central axial myopia also showed relative hyperopia in the periphery that increased in magnitude with eccentricity. Alterations in peripheral refraction were highly correlated with eccentricity-dependent changes in vitreous chamber depth and the shape of the posterior globe.

CONCLUSIONS

Like humans with myopia, monkeys with form-deprivation myopia exhibit relative peripheral hyperopia and eyes that are less oblate and more prolate. Thus, in addition to producing central refractive errors, abnormal visual experience can alter the shape of the posterior globe and the pattern of peripheral refractive errors in infant primates.

Early use of eyeglasses for myopia predicts long axial length of the eye

Patients with long axial length (AL) eyes (> 25 mm) are at increased risk of globe perforation during performance of intraconal (retrobulbar) eye block. These patients often require glasses or contact lenses for myopia (nearsightedness) as children or young adults. A history of early correction for myopia might, therefore, be a predictor of long AL eyes. One hundred one patients undergoing cataract surgery had AL measured and answered questions about their use of corrective lenses. We found that a history of correction for myopia as a child or young adult was 82% sensitive and 84% specific for having a measured AL > or = 25 mm. Patients with this history may be at increased risk for globe perforation during intraconal block.

Peribulbar blockade with a short needle for phacoemulsification surgery

BACKGROUND

Peribulbar blockade is still widely used for phacoemulsification surgery. The potential complications of this technique include central spread, globe perforation and retrobulbar hemorrhage. The 25 mm needle is the most common needle used to perform the block. The aim of this study was to demonstrate the efficacy of a 12.5 mm needle in performing peribulbar blockade for phacoemulsification surgery.

METHODS

After obtaining the hospital research and the Human Ethics Committees' approval, 200 patients undergoing the phacoemulsification procedure under local anesthesia were enrolled in this descriptive study. Peribulbar blockade was performed with a 27 G, 12.5-mm-long needle. The needle was inserted transcutaneously through the lower eyelid into the inferotemporal quadrant. Digital pressure was applied by the thumb and index fingers around the needle hub during injection. After negative aspiration, a local anesthetic solution was injected until total drop of the upper eyelid was achieved. Ocular akinesia was assessed 10 min after the block using the simple akinesia score. A score of 3 or less was accepted to provide adequate analgesia for the surgical procedure to be performed. If the block was inadequate for surgery after 10 min, supplementary anesthesia was provided using the same needle.

RESULTS

Adequate analgesia after the first injection was reported in 90.5% of the patients while 9.5% required supplementary anesthesia. There were no major sight or life-threatening complications.

CONCLUSION

Using a 12.5-mm-long needle for peribulbar blockade produced satisfactory results. This technique is effective for phacoemulsification surgery.

Ophthalmic regional anaesthesia

PURPOSE OF REVIEW

To summarize recent knowledge concerning ophthalmic regional anaesthesia.

RECENT FINDINGS

Ophthalmic regional anaesthesia has changed considerably over the past few years. Alternatives to retrobulbar anaesthesia have been proposed to reduce the number of complications without detriment to efficiency. Finally new local anaesthetics have been adopted and the indications have broadened, especially in vitroretineal surgery.

SUMMARY

New developments in ophthalmic regional anaesthesia are presented in this review. Different methods, indications and side effects are described in order to facilitate the clinician's choice, without any claim to single out an ideal technique.