[Sphenopalatine ganglion stimulation in the treatment of chronic refractory cluster headache. A preliminary multicenter study in Russia]. / Stimulyatsiya krylonebnogo gangliya v lechenii khronicheskoi klasternoi golovnoi boli. Rezul'taty pervogo mul'titsentrovogo opyta v Rossii.

OBJECTIVE: To analyze the results of sphenopalatine ganglion stimulation in treatment of chronic headache. MATERIALS AND METHODS: Medical histories of patients who underwent sphenopalatine ganglion stimulation in 4 clinical centers have been analyzed. The analysis included the type of pain and its characteristics, methods of surgery, CT, MRI, radiography before and after surgery. The follow-up data of patients with implanted pulse generators was collected in an outpatient clinic or by telephone review. RESULTS: The study included 15 patients with chronic refractory headache, including 14 with cluster headache and one female patient with features of trigeminal autonomic cephalgia without a clear definition of the type of pain. Trial stimulation was performed in 10 patients to determine analgesic effect. Among them stimulation was favorable in 7 cases, and 6 of them underwent pulse generator implantation. In total, 11 (73%) patients underwent implantation with a follow-up from 1 to 60 months. Among them only 6 (54%) patients use stimulation, the remaining 5 (46%) cases had device-related complications (migration, infection of system). Cluster headache has a significant improvement in long-term follow-up. CONCLUSIONS: Sphenopalatine ganglion stimulation may have high potential in the treatment of chronic drug-resistant cluster headache. The complication rate demonstrates that operative technique should be improved.

Heart rate increase after pulmonary vein isolation predicts freedom from atrial fibrillation at 1 year.

INTRODUCTION: Ablation of atrial vagal ganglia has been associated with improved pulmonary vein isolation (PVI) outcomes. Disruption of vagal reflexes results in heart rate (HR) increase. We investigated the association between HR change after PVI and freedom from atrial fibrillation (AF) at 1 year. METHODS AND RESULTS: Patients who underwent PVI for paroxysmal AF were identified from the Johns Hopkins Hospital AF registry. Electrocardiograms taken pre-PVI and post-PVI were used to determine the change in HR. Patients followed-up at 3, 6, and 12 months. Of 257 patients (66% male, age 59+/-11 years), 134 (52%) remained free from AF at 1 year. The average HR increased from 60.6 ± 11.3 beats per minute (bpm) pre-PVI to 70.7 ± 12.0 bpm post-PVI. Patients with recurrence of AF had lower post-PVI HR than those who remained free from AF (67.8 ± 0.2 vs 73.3 ± 13.0 bpm; P <.001). The probability of AF recurrence at 1-year decreased as the change in HR increased (estimated odds ratio [OR], 0.83; 95% confidence interval [CI, 0.74-0.93]; P = .002). HR increase more than 15 bpm was associated with the lowest odds of AF recurrence (estimated OR, 0.39; 95% [0.17-0.85]; P = .018) compared to HR decrease. CONCLUSIONS: Resting HR was found to increase after PVI. Increase in HR more than 15 bpm has a positive association with remaining free from atrial fibrillation at 1 year.

Avoidance of Vagal Response During Circumferential Pulmonary Vein Isolation: Effect of Initiating Isolation From Right Anterior Ganglionated Plexi.

BACKGROUND: Circumferential pulmonary vein isolation (CPVI) often cause unavoidable vagal reflexes during procedure due to the coincidental modification of ganglionated plexus which are located on pulmonary vein (PV) antrum. The right anterior ganglionated plexi (RAGP) which located at superoanterior area of right superior PV antrum is an essential station to regulate the cardiac autonomic nerve activities and is easily coincidentally ablated during CPVI. The aim of this study is to assess the effect of RAGP ablation on vagal response (VR) during CPVI. METHODS: A total of 80 patients with paroxysmal atrial fibrillation who underwent the first time CPVI were prospectively enrolled and randomly assigned to 2 groups: group A (n=40), CPVI started with right PVs at RAGP site; group B (n=40): CPVI started with left PVs first, and the last ablation site is RAGP. Electrophysiological parameters include basal cycle length, A-H interval, H-V interval, sinus node recovery time, and atrioventricular node Wenckebach point were recorded before and after CPVI procedure. RESULTS: During CPVI, the positive VR were only observed on 1 patient in group A and 25 patients in group B (P<0.001). A total of 21 patients with positive VR in group B needed for temporary ventricular pacing during procedure, while the only patient with positive VR in group A did not need for temporary ventricular pacing (P<0.001). Compared with baseline, basal cycle length, sinus node recovery time, and atrioventricular node Wenckebach point were decreased significantly after CPVI procedure in both groups (all P<0.05) and without differences between 2 groups. CONCLUSIONS: Circumferential PV isolation initiated from RAGP could effectively inhibit VR occurrence and significantly increase heart rate during procedure.

Effects of autonomic denervations on the rhythms in axial length and choroidal thickness in chicks.

In chicks, axial length and choroidal thickness undergo circadian oscillations. The choroid is innervated by both branches of the autonomic nervous system, but their contribution(s) to these rhythms is unknown. We used two combination lesions to test this. For parasympathectomy, nerve VII was sectioned presynaptic to the pterygopalatine ganglia, and the ciliary post-ganglionics were cut (double lesion; n = 8). Triple lesions excised the sympathetic superior cervical ganglion as well (n = 8). Sham surgery was done in controls (n = 7). 8-14 days later, axial dimensions were measured with ultrasonography at 4-h intervals over 24 h. Rhythm parameters were assessed using a "best fit" function, and growth rates measured. Both types of lesions resulted in ultradian (> 1 cycle/24 h) rhythms in choroidal thickness and axial length, and increased vitreous chamber growth (Exp-fellow: double: 69 µm; triple: 104 µm; p < 0.05). For double lesions, the frequency was 1.5 cycles/day for both rhythms; for triples the choroidal rhythm was 1.5 cycles/day, and the axial was 3 cycles/day. For double lesions, the amplitudes of both rhythms were larger than those of sham surgery controls (axial: 107 vs 54 µm; choroid: 124 vs 29 µm, p < 0.05). These findings provide evidence for the involvement of abnormal ocular rhythms in the growth stimulation underlying myopia development.

Catheter Ablation of Bradyarrhythmia: From the Beginning to the Future.

Enhanced parasympathetic tone may cause sinus bradycardia or pauses, transient or permanent atrioventricular block, with resultant vasovagal syncope. A substantial portion of these patients may be highly symptomatic and refractory to the conventional therapies and may require cardiac pacemaker implantation. Cardioneuroablation is a little known technique for management of patients with excessive vagal activation based on radiofrequency catheter ablation of main parasympathetic autonomic ganglia around the heart. Due to complicated inclusion criteria, ganglia detection methods, and ablation endpoints, routine usage of the procedure cannot be recommended at this time. In this comprehensive review, we aimed to discuss all aspects of cardioneuroablation procedure in bradyarrhythmias.

Coincidental ganglionated plexus modification during radiofrequency pulmonary vein isolation and post-ablation arrhythmia recurrence.

AIMS: Vagal responses (VR) during left atrial ablation for atrial fibrillation (AF) treatment have been reported to be associated with less recurrences, presumably because they are a sign of ganglionated plexi modification. Our objective was to evaluate whether coincidentally elicited VR during left atrial ablation are associated with lower AF recurrence rates. METHODS AND RESULTS: This is a post hoc analysis of a prospective study of 291 patients with paroxysmal AF undergoing radiofrequency pulmonary vein isolation (PVI). Vagal responses were defined as episodes of heart rate <40 bpm or asystole lasting >5 s elicited during energy application. Sixty-eight patients (23.4%) had a VR during ablation. In Kaplan-Meier analysis, mean recurrence-free survival was 449 days (95% confidence interval 411-488) in patients with VR when compared with 435 days (95% confidence interval 415-455) in those without (P = 0.310). The 12-month recurrence rate estimates were 25 and 27%, respectively. In an unadjusted Cox model, VR was associated with an odds ratio for recurrence of 0.77 (95% confidence interval 0.46-1.28). CONCLUSION: Coincidentally elicited VR during radiofrequency PVI in patients with paroxysmal AF do not appear to be related to lower risk of arrhythmia recurrence. This may mean that, even if a VR is truly a sign of coincidental ablation of a ganglionated plexus, this does not necessarily mean that a therapeutic modification has been effected, at least to a degree associated with clinical benefit.

Feasibility of endoscopic submandibular ganglion neurectomy for drooling.

We performed endoscopic transoral neurectomy of the submandibular and sublingual glands to treat drooling. We bilaterally operated two adult cases with treatment-resistant drooling. In these patients, conventional treatment had failed. Repeated botilinum toxin type A (BOTOX®, Abdi Ibrahim Pharmaceutical Company, Istanbul, Turkey) injections had been effective but were becoming less so. The patients benefited from surgery in that their saliva scores decreased. No issue emerged over 6 months of follow-up. Endoscopic transoral neurectomy of the submandibular and sublingual glands reduces saliva production and allows management of drooling in treatment-resistant patients. Laryngoscope, 127:1604-1607, 2017.

Simple ways to dissect ciliary ganglion for orbital anatomical education.

In the case of anatomical dissection as part of medical education, it is difficult for medical students to find the ciliary ganglion (CG) since it is small and located deeply in the orbit between the optic nerve and the lateral rectus muscle and embedded in the orbital fat. Here, we would like to introduce simple ways to find the CG by 1): tracing the sensory and parasympathetic roots to find the CG from the superior direction above the orbit, 2): transecting and retracting the lateral rectus muscle to visualize the CG from the lateral direction of the orbit, and 3): taking out whole orbital structures first and dissecting to observe the CG. The advantages and disadvantages of these methods are discussed from the standpoint of decreased laboratory time and students as beginners at orbital anatomy.

Integrity of the Ganglionated Plexi Is Essential to Parasympathetic Innervation of the Atrioventricular Node by the Right Vagus Nerve.

INTRODUCTION: Radiofrequency isolation of pulmonary vein can be accompanied by transient sinus bradycardia or atrioventricular nodal (AVN) block, suggesting an influence on vagal cardiac innervation. However, the importance of the atrial fat pads in relation with the vagal innervation of AVN in humans remains largely unknown. The aim of this study was to evaluate the role of ganglionated plexi (GP) in the innervation of the AVN by the right vagus nerve. METHODS AND RESULTS: Direct epicardial high-frequency stimulation (HFS) of the GP (20 patients) and the right vagus nerve (10 patients) was performed before and after fat pad exclusion or destruction in 20 patients undergoing thoracoscopic epicardial ablation for the treatment of persistent AF. Asystole longer than 3 seconds or acute R-R prolongation over 25% was considered as a positive response to HFS. Prior to the ablation, positive responses to HFS were detected in 3 GPs in 7 patients (35%), 2 GPs in 5 patients (25%), and one GP in 8 patients (40%). After exclusion of the fat pads, all patients had a negative response to HFS. All the patients who exhibited a positive response to right vagus nerve stimulation (n = 10) demonstrated negative responses after the ablation. CONCLUSION: The integrity of the GP is essential for the right vagus nerve to exert physiological effects of on AVN in humans.

Neuronavigated percutaneous approach to the sphenopalatine ganglion.

The sphenopalatine ganglion (SPG) has been assumed to be involved in the genesis of several types of facial pain, including Sluder's neuralgia, trigeminal neuralgia, persistent idiopathic facial pain, cluster headache, and atypical facial pain. The gold standard treatments for SPG-related pain are percutaneous procedures performed with the aid of fluoroscopy or CT. In this technical note the authors present, for the first time, an SPG approach using the aid of a neuronavigator.

"Cardio-Neuromodulation" With a Multielectrode Irrigated Catheter: A Potential New Approach for Patients With Cardio-Inhibitory Syncope.

Syncope is frequently neurally mediated and can seriously affect quality of life. Different ablation strategies have been successfully performed. These approaches have not gained wide acceptance and are quite extensive and complex, exposing patients to significant risks. This article reports the case of a 16-year-old girl who was severely affected by frequent and prolonged episodes of syncope and was treated by tailored ablation of the anterior right ganglionated plexus with a multielectrode irrigated catheter. She had fainted >30 times in the 5 years preceding treatment, experiencing approximately 10 severe episodes of syncope in the previous 12 months. After 3 minutes of ablation, the P-P interval was reduced by >400 milliseconds. Syncope disappeared and the patient has remained completely asymptomatic over a follow-up of 22 months. The "reset" basal P-P interval has remained unchanged (follow-up electrocardiogram at 16 months). At 6 months, there was no residual heart rate activity <50 bpm. On 24-hour rhythm registration, P-P intervals ≥1,000 milliseconds (corresponding to a heart rate of ≤60 bpm) were reduced by >16,000 beats. We believe that this case report is original for several reasons: the unusual clinical presentation; the unique structure targeted; the very limited ablation, implying much lower risks for the patient; the anatomical approach; and the different endpoint. This new "cardio-neuromodulation" approach could be useful for the treatment of patients with neurally mediated syncope.

Trigeminal and sphenopalatine ganglion stimulation for intractable craniofacial pain--case series and literature review.

INTRODUCTION: Facial pain is often debilitating and can be characterized by a sharp, stabbing, burning, aching, and dysesthetic sensation. Specifically, trigeminal neuropathic pain (TNP), anesthesia dolorosa, and persistent idiopathic facial pain (PIFP) are difficult diseases to treat, can be quite debilitating and an effective, enduring treatment remains elusive. METHODS: We retrospectively reviewed our early experience with stimulation involving the trigeminal and sphenopalatine ganglion stimulation for TNP, anesthesia dolorosa, and PIFP between 2010-2014 to assess the feasibility of implanting at these ganglionic sites. Seven patients received either trigeminal and/or sphenopalatine ganglion stimulation with or without peripheral nerve stimulation, having failed multiple alternative modalities of treatment. The treatments were tailored on the physical location of pain to ensure regional coverage with the stimulation. RESULTS: Fluoroscopy or frameless stereotaxy was utilized to place the sphenopalatine and/or trigeminal ganglion stimulator. All patients were initially trialed before implantation. Trial leads implanted in the pterygopalatine fossa near the sphenopalatine ganglion were implanted via transpterygoid (lateral-medial, infrazygomatic) approach. Trial leads were implanted in the trigeminal ganglion via percutaneous Hartel approach, all of which resulted in masseter contraction. Patients who developed clinically significant pain improvement underwent implantation. The trigeminal ganglion stimulation permanent implants involved placing a grid electrode over Meckel's cave via subtemporal craniotomy, which offered a greater ability to stimulate subdivisions of the trigeminal nerve, without muscular (V3) side effects. Two of the seven overall patients did not respond well to the trial and were not implanted. Five patients reported pain relief with up to 24-month follow-up. Several of the sphenopalatine ganglion stimulation patients had pain relief without any paresthesias. There were no electrode migrations or post-surgical complications. CONCLUSIONS: Refractory facial pain may respond positively to ganglionic forms of stimulation. It appears safe and durable to implant electrodes in the pterygopalatine fossa via a lateral transpterygoid approach. Also, implantation of an electrode grid overlying Meckel's cave appears to be a feasible alternative to the Hartel approach. Further investigation is needed to evaluate the usefulness of these approaches for various facial pain conditions.

Sphenopalatine Ganglion Stimulation in Neurovascular Headaches.

The interest for the sphenopalatine ganglion (SPG) in neurovascular headaches dates back to 1908 when Sluder presented his work on the role of the SPG in 'nasal headaches', which are now part of the trigeminal autonomic cephalalgias and cluster headache (ICHD-III-beta). Since then various interventions with blocking or lesional properties have targeted the SPG (transnasal injection of lidocaine and other agents, alcohol or steroid injections, radiofrequency lesions, or even ganglionectomy); success rates vary, but benefit is usually transient. Here we briefly review some anatomophysiological characteristics of the SPG and hypotheses about its pathophysiological role in neurovascular headaches before describing recent therapeutic results obtained with electrical stimulation of the SPG. Based on results of a prospective randomized controlled study, SPG stimulation appears to be an effective treatment option for patients with chronic cluster headaches; efficacy data indicate that acute electrical stimulation of the SPG provides significant attack pain relief and in many cases pain freedom compared to sham stimulation. Moreover, in some patients SPG stimulation has been associated with a significant and clinically meaningful reduction in cluster headache attack frequency; this preventive effect of SPG stimulation warrants further investigation. For migraine attacks, the outcome of a proof-of-concept study using a temporary electrode implanted in the pterygopalatine fossa was less encouraging; however, an ongoing multicenter trial is evaluating the efficacy of long-term SPG stimulation against sham stimulation for acute and preventive treatment in patients with frequent migraine.

Transoral submandibular ganglion neurectomy: an anatomical feasibility study.

BACKGROUND: The management of sialorrhea can be difficult for both the patient and the clinician. Current management includes behavioral modification, anticholinergics, botulinum injections, and a variety of surgical options, which all have demonstrated some efficacy. As minimally invasive procedures flourish, we explore the feasibility of highly selective transoral submandibular neurectomy (TOSN) for the management of sialorrhea. METHODS: Ten human cadaver dissections of the floor of mouth were performed bilaterally, for a total of 20 separate cases. An intraoral technique for highly selective, submandibular ganglion neurectomy is demonstrated. RESULTS: A transoral submandibular ganglion neurectomy was performed in 10 cadavers (20 neurectomies) easily and reliably, without injury to the submandibular duct or the main trunk of the lingual nerve. CONCLUSION: Transoral submandibular neurectomy is an attractive addition to the armamentarium of surgical options for the treatment of medically intractable sialorrhea. Further study in selected patients would need to be performed to demonstrate clinical feasibility.

Ablation of epicardial ganglionated plexi increases atrial vulnerability to arrhythmias in dogs.

BACKGROUND: Previous studies have suggested that systematic ablation of ganglionated plexi (GP) could increase the short-term success rate of radiofrequency ablation for atrial fibrillation, but the long-term efficacy of this approach is not fully established. METHODS AND RESULTS: Twenty-four mongrel dogs were divided into 3 groups: epicardial GP ablation group 1 (n=8), epicardial GP ablation group 2 (n=8), and a sham operation group (n=8). In the 2 epicardial GP ablation groups, the 4 major GP and the ligament of Marshall were systematically ablated. The effective refractory period and inducibility of tachyarrhythmias were measured before and immediately after GP ablation in epicardial GP ablation group 1 and 8 weeks later in the other 2 groups. Tyrosine hydroxylase and choline acetyltransferase expressions were also determined immunohistochemically 8 weeks later in the latter groups. Compared with epicardial GP ablation group 1 and the sham operation group, epicardial GP ablation group 2 had the shortest atrial and ventricular effective refractory period and the highest inducibility of atrial tachyarrhythmias. The inducibility of ventricular tachyarrhythmias among the 3 groups was comparable. The density of tyrosine hydroxylase- and choline acetyltransferase-positive nerves in the atrium was the highest in epicardial GP group 2, whereas there were no significant intergroup differences in the densities of these 2 types of nerves in the ventricle. CONCLUSIONS: After 8 weeks of healing, epicardial GP ablation without additional atrial ablation was potentially proarrhythmic, which may be attributable to decreased atrial effective refractory period and hyper-reinnervation involving both sympathetic and parasympathetic nerves.

Cardiac impairment evaluated by transesophageal echocardiography and invasive measurements in rats undergoing sinoaortic denervation.

BACKGROUND: Sympathetic hyperactivity may be related to left ventricular (LV) dysfunction and baro- and chemoreflex impairment in hypertension. However, cardiac function, regarding the association of hypertension and baroreflex dysfunction, has not been previously evaluated by transesophageal echocardiography (TEE) using intracardiac echocardiographic catheter. METHODS AND RESULTS: We evaluated exercise tests, baroreflex sensitivity and cardiovascular autonomic control, cardiac function, and biventricular invasive pressures in rats 10 weeks after sinoaortic denervation (SAD). The rats (n = 32) were divided into 4 groups: 16 Wistar (W) with (n = 8) or without SAD (n = 8) and 16 spontaneously hypertensive rats (SHR) with (n = 8) or without SAD (SHRSAD) (n = 8). Blood pressure (BP) and heart rate (HR) did not change between the groups with or without SAD; however, compared to W, SHR groups had higher BP levels and BP variability was increased. Exercise testing showed that SHR had better functional capacity compared to SAD and SHRSAD. Echocardiography showed left ventricular (LV) concentric hypertrophy; segmental systolic and diastolic biventricular dysfunction; indirect signals of pulmonary arterial hypertension, mostly evident in SHRSAD. The end-diastolic right ventricular (RV) pressure increased in all groups compared to W, and the end-diastolic LV pressure increased in SHR and SHRSAD groups compared to W, and in SHRSAD compared to SAD. CONCLUSIONS: Our results suggest that baroreflex dysfunction impairs cardiac function, and increases pulmonary artery pressure, supporting a role for baroreflex dysfunction in the pathogenesis of hypertensive cardiac disease. Moreover, TEE is a useful and feasible noninvasive technique that allows the assessment of cardiac function, particularly RV indices in this model of cardiac disease.

Bilateral atrial ganglionated plexus involvement in atrial responses to left-sided plexus stimulation in canines.

AIMS: Given the clinical interest concerning 'reflex vagal' responses to identify left atrial (LA) targets for ablative therapy of atrial fibrillation, we investigated whether vagal and bilateral atrial neural pathways may be involved in chronotropic and atrial repolarization responses to LA ganglionated plexus (GP) stimulation. METHODS AND RESULTS: Unipolar electrograms were recorded from 191 right atrial (RA) and LA sites in anaesthetized canines prior to and during electrical stimulation of the right vagus nerve (VgN), left VgN, or LAGP at baseline and following (i) bilateral VgN decentralization, and radiofrequency ablation of (ii) periaortic/superior vena cava (Ao/SVC) and (iii) RAGP in 14 animals (anterograde group), and in the reverse order in 7 (retrograde). Repolarization changes were also measured in similar preparations during Ao/SVC (n = 8) and RAGP stimulation (n = 23). Sinus cycle length (SCL) prolongation, and RA and LA repolarization changes (affected atrial surface area) were induced during LAGP stimulation. SCL prolongation and RA repolarization changes were unaffected by VgN decentralization but reduced following Ao/SVC and RAGP ablation in the anterograde group. In the retrograde group, chronotropic and RA repolarization changes were reduced following RAGP and abolished following Ao/SVC ablation. In contrast, LA repolarization responses to LAGP stimulation were reduced following VgN decentralization and each subsequent ablation step, with small residual responses after completing the anterograde protocol. Ao/SVC and RAGP stimulation exerted predominant influences in adjacent regions as well as demonstrating LA extensions. CONCLUSION: Vagal as well as bilateral atrial neural pathways are involved in mediating chronotropic and LA repolarization responses to LAGP stimulation.

Parasympathetic influences on emmetropization in chicks: evidence for different mechanisms in form deprivation vs negative lens-induced myopia.

Ciliary ganglionectomy inhibits the development of myopia in chicks (Schmid et al., 1999), but has no effect on the compensatory responses to spectacle lenses (Schmid and Wildsoet, 1996). This study was done to assess the potential influence of the other parasympathetic input to the choroid, the pterygopalatine ganglia, on the choroidal and axial responses to retinal defocus, and to form deprivation. 4-5 week-old chicks had one of the following surgeries to one eye: (1) Section (X) of the autonomic part of cranial N VII (input to the pterygopalatine ganglia) (PPGX, n = 16), (2) PPGX plus ciliary ganglionectomy (PPG/CGX, n = 23) or (3) PPGX plus superior cervical ganglionectomy (PPG/SCGX, n = 10). Experimental eyes were fitted with positive or negative lenses, or diffusers, several days after surgery. In one group of PPG/CGX, eyes did not wear any devices (n = 8). Intact (no surgery) controls were done for all visual manipulations (lenses or diffusers). Sham surgeries were done for the PPG/CGX condition (n = 4). Ocular dimensions were measured using A-scan ultrasonography prior to the surgery, 5 days later when visual devices were placed on the eyes, at the end of lens- or diffuser-wear, and in the case of diffusers, 4 days after diffuser removal to look at "recovery". Refractive errors were measured using a Hartinger's refractometer. IOP was measured in 7 PPG/CGX birds 7d after surgery. PPGX/CGX resulted in choroidal thickening (125 µm) and a decrease in IOP over one week post-surgery. It also prevented the development of myopia in response to form deprivation (X vs intact: 0.2 D vs -4.1 D; p < 0.005), by preventing the increase in axial elongation (250 µm vs 670 µm/5d; p < 0.005). In fact, growth rate slowed below normal (X vs fellow eyes: 250 µm vs 489 µm/5d; p = 0.002). By contrast, there were no effects of this lesion on the development of myopia in response to negative lenses (X vs intact: -5.4 D vs -5.3 D). All three lesions inhibited the compensatory choroidal thickening in response to myopic defocus (ANOVA, p = 0.0008), but had no effect on the thinning response to hyperopic defocus. These results argue for different underlying mechanisms for the growth responses to form deprivation vs negative lens wear. They also imply that choroidal thickening and thinning are not opposing elements of a single mechanism.