Simulation of complex strabismus surgical procedures on goat eyes

Purpose: To describe the possibility of complex strabismus surgical simulation on goat eyes. Methods: The goat eyes were procured from local slaughterhouse with retained extra ocular muscle tissues. The obtained eyes were inspected for globe integrity, muscle quality, muscle length, and the surrounding teno-conjunctival layers. The included eyes were then segregated for surgical simulation based on their insertion and orientation (as oblique or recti), and they were mounted on a mannequin head, with a fixation suture at free end to simulate the resting tension. Additionally, as per necessary, extra muscles were also transplanted along desired sites to simulate human extra ocular muscle anatomy. Results: The inferior oblique, superior oblique, and all other four recti were successfully simulated in varying proportions in more than 50 eyes. Primarily, by simulating the lateral rectus, inferior rectus, and the inferior oblique muscle, staged weakening procedures of inferior oblique were successfully practiced (Fink’s recession, Park’s recession, Elliot and Nankin procedure, total anterior positioning, and antero-nasal trans-position or Stager’s procedure). Similarly, by simulating superior rectus, inferior rectus, lateral rectus, and the medial rectus muscles, half width transposition, full width transposition, and other complex procedures were practiced (Knapp’s procedure, augmented Knapp’s, Nishida’s procedure, Faden operation, and Y splitting procedure). Furthermore, by simulating superior oblique and the superior rectus muscles, superior oblique tuck, posterior tenectomy, loop tenotomy, and Harada Ito procedures were successfully practiced. Conclusions: On goat eyes, the complex strabismus surgical procedures can be successfully simulated and practiced after re-organizing the existing muscles in different patterns.

EOG Elicited by Rhythmic Auditory Predicts the Depth of Sedation During Sevoflurane Anesthesia

Background: Several electroencephalographic (EEG) variables have been used to estimate changes in human brain electrical activity during changing states of consciousness as a clinical monitoring tool to anesthesia and sedation. However, the EEG signal is weak and extremely susceptible to suppression interference. The use of EEG variables as anesthesia monitors is still controversial. Recent studies have shown a new language paradigm that elicited rhythmic brain responses and ocular muscle activity tracking sentence rhythms in speech. Electrooculogram (EOG) driven by rhythmic auditory stimulation has a larger amplitude than EEG variables and a higher temporal resolution than event-related brain potentials, which may be a potential monitor of anesthetic depth.Methods: Twenty-five patients inhaled sevoflurane via laryngeal mask for induction of anesthesia. The initial concentration of sevoflurane was set to 0.4% and increased by 0.1% every 1 min until loss of consciousness. During the entire operation, rhythmic auditory stimulation was presented binaurally to elicit ocular muscle activity.Results: When the end-tidal sevoflurane concentration (Etsevo) was low, the EOG had a significant spectral peak at 0.5 Hz, which is the same frequency as the rhythmic auditory stimulation, and then the peak value of EOG decreased with the increase of Etsevo. Peak value of EOG spectrum under the rhythmic auditory stimulation (PERA) showed significant differences in different depth of sedation (wakefulness: 84.0 ± 22.8, light sedation: 47.0 ± 27.7, deep sedation: 10.9 ± 16.5, P<0.01). PERA is correlated well with Etsevo (-0.75, P<0.01) and was able to predict the sedation depth during the induction period of anesthesia well (PK = 0.92 ± 0.08).Conclusion: We found that the ocular muscle activity synchronizes to the rhythmic auditory stimulation structures during induction with sevoflurane. With the increase of Etsevo, the synchronizing ability of the ocular electricity to rhythmic auditory stimulation gradually weakens and eventually disappears. Based on this evidence, the EOG driven by a rhythmic auditory stimulation may be a new and reliable approach to characterize and predict anesthetic depth objectively. Trial registration: The research project was registered at chictr.org.cn (ChiCTR1900026590, 2019/10/15).

Effectiveness of Occular Muscle exercises on degree of Myopia

There is an ever-rising prevalence of myopia in our population. Many individuals are being diagnosed with myopia; however, the treatment for myopia is relatively the same. Evidence has shown that there is the involvement of extraocular muscles as well in the development of myopia. These muscles can be trained and may prove useful in improving myopia. Thus it is important to study the effects of ocular exercises on myopia. The objective of this study was to find out the effect of ocular muscle exercises on the degree of myopia. There was a total of 46 subjects who were willing participants of this study. Pre-intervention and post-intervention visual acuity was analyzed. The experimental group received ocular exercises, and the control group was advised to follow a routine for six weeks. There was no significant effect of ocular muscle exercises on the degree of myopia post-intervention (p = 0.3275). Based on the result of the study, it can be said that the ocular exercise does not affect the improvement in the visual acuity in an individual. Similarly, the ocular muscle exercises were not effective in improving the degree of myopia.

Ultrasound detection of iatrogenic injury during peribulbar eye block: a cadaveric study

BackgroundOphthalmic eye blocks, such as retrobulbar, peribulbar and sub-Tenon’s, are traditionally conducted “blind”. Complications are rare but potentially devastating. Life-threatening complications include brain stem anesthesia and local anesthetic toxicity, whereas sight-threatening complications include globe perforation, optic nerve damage and ocular muscle damage. Ultrasound permits a view of orbital structures and can be used to guide needle placement. The ultrasound appearances of unintended local anesthetic injection into vital orbital structures have not been documented. This study aimed to record the ultrasound appearances of unintended injection locations.MethodsThe spherical shape of the eyeballs of three soft-fix Thiel embalmed human cadavers were restored using glycerol. Iatrogenic injury in peribulbar block was then simulated through injection of printers’ ink mixed with Thiel embalming fluid. Ultrasound was used to guide the needles and the tips were redirected to lie within the globe, lateral rectus and optic nerve. Ultrasound images were recorded during injection. The orbital cavities were then dissected via a superior approach to record the location and extent of injectate spread.ResultsReal-time globe rupture, ocular muscle injection and optic nerve injection were visible using ultrasound. Characteristic appearances were identified in each case. Dissection confirmed needle and injection placement.ConclusionsThe ultrasound appearance of block complications is important to document and should be an integral part of regional anesthesia training. This study is the first to provide such images for ophthalmic nerve blocks. It offers ophthalmic anesthetists and ophthalmologists the potential to diagnose severe complications rapidly and accurately with a potential impact on patient safety.

A Case of Transient Visual Disturbance and Ocular Paresis after Endoscopic Sinus Surgery

Endoscopic sinus surgery (ESS) is widely used as standard surgical treatment for chronic rhinosinusitis. Orbital complications of varying degrees occurred during ESS have been widely reported. If the orbital symptoms occurred immediately after surgery, ocular damage associated with surgery is suspected if the patient’s preoperative ocular function was patent. If immediate action is not taken, permanent visual loss might develop, so it is very important to diagnose orbital complications and take appropriate action. In our case, there was no definite intraorbital hemorrhage when sudden visual loss was noted. The symptoms were fully recovered without further treatment and it is clinically suspected to be caused by transient ocular muscle toxicity of local anesthetics.