Surgical Anatomy of the Chinese Orbit

A Systematic and Critical Review on the Anatomy of the Ethmoidal Foramina

PURPOSE

The osteologic anatomy of the orbit is still a field of intense research, particularly as far as vascular channels are concerned. Among them, ethmoidal foraminas (EFs) are certainly those that have more clinical importance and indeed have been deeply investigated. Unfortunately, the vast production of articles, far from clarifying their anatomy, generated a certain degree of confusion.

METHODS

A search on Pubmed and Scopus databases updated up to December 31, 2023, has been carried out with the keyword "ethmoidal foramen" yielding a list of 357 items. With a careful screening process, 31 articles were enlisted to be included in the present review.

RESULTS

A critical review process confirmed that many results published over the years appear inconsistent, particularly as far as EFs topography is concerned. The possible reasons for this lack of consistency can be traced back to inter-ethnical differences, uncertainty on the anterior bony landmarks employed in the investigations, and lack of a general consensus over EFs classification. A novel approach, based on the normalization of the distance of the anterior landmarks relative to the length of the orbit (relative depth index), should overcome some of the major problems encountered so far.

CONCLUSIONS

Novel and clear guidelines to classify EFs and to locate them on the medial wall are required. Determining the relative depth index of EFs may be an interesting approach to solve the matter. Other methods can be also devised. However, direct measurements from bony landmarks, without any further analysis seem inadequate and possibly misleading.

Are the Ethmoidal Foramina Through the Frontal Bone, Ethmoid Bone, or Frontoethmoidal Suture?

INTRODUCTION

To investigate the locations of the anterior, middle, and posterior ethmoidal foramina and their relationships to the frontoethmoidal suture.

METHODS

One hundred twenty sides from sixty adult human skulls were used. Specimens with significant damage to the medial orbit wall were excluded. The number of ethmoidal foramina (anterior, middle, and posterior) on the medial orbital wall and the relationship of each foramen to the frontoethmoidal suture were recorded and classified as follows: Type I: superior to the frontoethmoidal suture; Type II: on the frontoethmoidal suture; Type III: inferior to the frontoethmoidal suture.

RESULTS

Of the ninety-four sides, fourteen (14.9%) had one foramen, sixty-two (66.0%) had two , and eighteen (19.1%) had three. In total, 192 ethmoidal foramina were observed. Among the fourteen sides with one foramen, eight foramina were anterior and six were posterior. Among the 192 ethmoidal foramina, 162 were eligible for fur ther classification (74 anterior, 14 middle, and 74 posterior). Types I, II, and III ethmoidal foramina were found in 38.3% (62/162), 61.7% (100/162), and 0% (0/162), respectively.

CONCLUSIONS

Our current study found a higher incidence of type I than previously reported. It is important to be aware of the significant incidence of foramen variations when the medial orbit wall is manipulated during surgery. Unless caution is observed, an inadvertent surgical injury can occur and lead to life-threatening complications. Therefore, a good understanding of orbital anatomy and its potential variations is critical for improving patient out comes.

Reverse Lid Swinging Approach: A Case Series

In this report, the authors describe the reverse lid swinging approach, which comprises lateral canthotomy, superior lateral cantholysis to free the upper eyelid, and an incision at the superonasal conjunctival fornix for orbital exposure. Four patients underwent orbitotomy using the reverse lid swinging approach for orbital tumor removal (n = 3) or orbital abscess drainage (n = 1). All 4 operations were uneventful, with no optic nerve dysfunction or extraocular dysmotility over the follow-up period. Satisfactory cosmesis was achieved with no visible external scar in all cases. The reverse lid swinging approach provides easy access to medial orbital lesions as demonstrated in the present case series.

Evaluation of the Cranial Aperture of the Optic Canal on Cone-Beam Computed Tomography Images and its Clinical Implications for the Transcranial Approaches

OBJECTIVE

This study aimed to investigate morphometric properties of the cranial aperture (CA) of the optic canal.

METHODS

Cone-beam computed tomography images of 400 individuals (200 males and 200 females) aged 37.32 ± 15.87 years were retrospectively examined to assess the morphometry and morphology of the CA.

RESULTS

The height and width of CA were found as 4.22 ± 0.74 mm and 7.27 ± 1.15 mm, respectively. The distances between the CA and the midsagittal line, the anterior and lateral boundaries of the anterior skull base were measured as 5.77 ± 1.32 mm, 64.97 ± 6.36 mm, and 41.00 ± 4.05, respectively. The angle of the optic canal in the sagittal plane was measured as 7.57° ± 3.95°, whereas in the horizontal plane as 38.96° ± 4.36°. The aperture shape was defined as the tear-drop (413 foramina, 51.62%), triangular (180 foramina, 22.50%), oval (158 foramina, 19.75%), round (30 foramina, 3.75%), and polygonal (19 foramina, 2.38%).

CONCLUSIONS

The authors observed that the diameters, and angulations of the CA may change relative to gender and the shape. The anatomic features of CA are important for the positioning of the patient's head, the choice of the appropriate surgical approach or equipment, and the detection of anatomical landmarks during interventions. In this context, our dataset may be beneficial for surgeons helpful as a reference for radiological evaluations.

A cadaveric study investigating the anatomy of the medial orbital wall

The purpose of this study is to investigate the applicability of the current surgical guideline, known as ‘24-12-6’ surgical guideline, in the Hispanic and European populations. This guideline is used during numerous orbital surgeries and states that the distance between the anterior lacrimal crest (ALC) to the anterior ethmoidal foramen (AEF) (24 mm), the AEF to the posterior ethmoidal foramen (PEF) (12 mm), and the PEF to the optic canal (OC) (6 mm) follows a Rule of Halves. Previous studies suggest this surgical guideline is not applicable for all ethnicities; however, to our knowledge, no data has been published regarding the accuracy of this guideline pertaining to the Hispanic population. An experimental study was performed on 79 orbits (52 cadavers) donated to the Human Anatomy Program at UT Health San Antonio. The ALC, AEF, posterior ethmoidal foramen, and OC were identified; the orbit was enucleated and all remaining soft tissue removed. The distance between each landmark was recorded using a digital caliper. For all cadavers studied, the distances between the ALC, AEF, posterior ethmoidal foramen, and OC were 24.76 mm, 13.89 mm, and 7.61 mm, respectively. Thus, the ‘24-12-6’ surgical guideline was not applicable to the sample studied. Based on ethnicity data, these relationships were also not true for the European or the Hispanic populations. Therefore, significant anatomical variations exist in the current surgical guideline. Clinicians may need to adjust their methodology during surgical procedures in order to optimize patient care.

Anatomic features of the cranial aperture of the optic canal in children: a radiologic study

OBJECTIVE

This study aimed to peruse anatomic features of the cranial aperture of the optic canal (CAOC) for obtaining an extended morphometric dataset in children.

METHODS

Computed tomography images of 200 children were included in this retrospective work to analyze the shape, location and diameters of the CAOC.

RESULTS

The CAOC area, width and height were observed as 17.53 ± 2.80 mm², 6.12 ± 0.84 mm, and 4.35 ± 0.64 mm, respectively. The angle of the optic canal in axial plane was found as 39.28 ± 5.13°, while in sagittal plane as 16.01 ± 6.76°. The distance between the CAOC and the midsagittal line was 7.17 ± 1.48 mm. The CAOC was measured as 54.04 ± 5.23 mm and 42.55 ± 3.28 mm away from the anterior and lateral boundary of the anterior skull base, respectively. The CAOC shape was described as the tear-drop (186 foramina, 46.5%), triangular (156 foramina, 39%), oval (47 foramina, 11.8%), and round (11 foramina, 2.8%).

CONCLUSION

The depth, angle and diameter measurements belonging to the CAOC were changing according to its shape or demographic data (e.g., sex and age). Therefore, preoperative radiologic evaluation containing the shape, location and size of the CAOC should be considered by multidisciplinary operating teams in terms of surgical interventions such as implant positioning.

Triangulating the ledge: radiographic study of the floor of orbit and derivation of a novel template

In orbital floor reconstruction, the need for the orbital implant to reach the exact position of the posteromedial ledge is essential, but owing to the complex anatomy of the region, visualisation of the ledge may be difficult. Several morphometric studies, both radiographic and cadaveric, have calculated a mean length from the orbital rim to the ledge. However, those linear measurements are unreliable and possess a higher margin of error for intraoperative guidance. This study attempts to triangulate the position of the posterior ledge from three easily accessible and reproducible points on the orbit and tries to provide a better guideline. A total of 50 patients (25 male and 25 female) with no history of orbital trauma or orbital surgery were selected randomly for this study. Computed tomography (CT) of both orbits, was done from three anatomically consistent and reproducible points: the infraorbital rim just above the infraorbital foramen (point A), hamulus lacrimalis (point B), and the most anterior point of the inferior orbital fissure (point C). The distance from these landmarks to the posterior ledge was measured using DICOM imaging software. A polygonal template was fabricated using the data obtained, which was used for intraoperative guidance. The mean (SD) distance to the posterior ledge from point A was 32.99 (1.35) mm, from point B was 31.36 (1.31) mm, and from point C was 20.19 (1.40) mm. There were no significant differences between left and right orbit or between male and female subjects. The template guides the shape, size, and direction of the orbital implant, reducing the risk of undersized or misplaced implants.

Location of the infraorbital foramen with reference to soft tissue landmarks for regional nerve blocks during midface surgery

PURPOSE

An infraorbital nerve (ION) block is widely used to accomplish regional anesthesia during surgical procedures involving the midface region. This study aimed to elucidate the exact location of the infraorbital foramen (IOF) in relation to clinically useful soft-tissue landmarks for achieving an effective ION block.

METHODS

Forty-three hemifaces from 23 embalmed Korean cadavers were dissected. The lateral canthus, peak of Cupid's bow, medial limbus, and midline were used as reference points. The distances from the IOF to the midline and the lateral canthus were measured.

RESULTS

The IOF was located approximately 25 mm below the lateral canthus and 27 mm lateral to the midline. In all cases, the IOF was situated within 9.0 mm of the crossing point of the oblique line connecting the lateral canthus to the peak of Cupid's bow and the vertical line through the medial limbus.

CONCLUSION

Considering the spread of an anesthetic agent, injecting it into the crossing point of the oblique line through the lateral canthus to the peak of Cupid's bow and the vertical line through the medial limbus would successfully block the ION in most patients.

Morphometric Analysis of the Orbital Aperture in North Indian Population: A Retrospective Digital Forensic Study

Introduction:

The morphometric variations seen in the orbital aperture play a significant role in forensic anthropology, for determining the personal and gender identification, especially in case of mass disasters.

Aim:

The aim of the present study was to evaluate the orbital aperture dimensions along with interorbital distance as observed on posteroanterior (PA) cephalograms for personal and gender identification.

Materials and Methods:

The present retrospective study was conducted to evaluate the morphometric dimensions of orbital aperture seen on PA cephalogram taken using PLANMECA digital machine and ROMEXIS software. The height and width of the orbits along with the interorbital distance were measured using measuring tools in the accompanying software. Data were analyzed using SPSS software version 21.0.

Results:

All the linear measurements such as orbital height, orbital width, and interorbital distance were significantly greater in males than females in the North Indian population with P = 0.001. The present study found 84.8% accuracy after subjecting the obtained value to discriminant function analysis.

Conclusion:

The morphometric analysis of the orbital aperture using postero-anterior cephalogram can be used as an adjuvant for personal and gender identification in forensic anthropology.

An Applied Anatomical Study of the Ethmoidal Arteries: Computed Tomographic and Direct Measurements in Human Cadavers

Computed tomography (CT) images have been used in very few studies on distances to the ethmoidal arteries in the orbit. Most other studies have included direct measurements on cadavers and frequently quote the 24-12-6 mm rule to describe distances from the anterior lacrimal crest to the anterior and posterior ethmoidal foramina (AEF and PEF), optic canal (OC), respectively. However, the large interindividual variation of distances renders absolute values less applicable in a clinical setting. Preoperative measurements on CT images may provide more precise distances than absolute rules and thus lead to safer orbital surgery. The authors hypothesize that the distances to the ethmoidal arteries and the length of the medial wall are positively correlated and that measurements of the distances from the posterior lacrimal crest (PLC) on CT images are feasible with a low intra- and interobserver variability.Fifty intact orbits from 25 Caucasian cadavers were exenterated and examined. In additional, high-resolution CT scans of 48 orbits from 24 other Caucasian nonexenterated cadavers were examined. Distances were measured from 4 different anterior landmarks to the AEF and PEF and the OC.Distances from the most anterior landmarks to the arteries were positively correlated with the length of the medial wall. Measurements of the distances from the PLC to the ethmoidal arteries on CT images were feasible with a low intra- and interobserver variability. In conclusion, iatrogenic damage to the ethmoidal arteries in the orbit may be best avoided by using CT measurements in presurgical planning.

A novel anatomical thin titanium mesh plate with patient-matched bending technique for orbital floor reconstruction

This study developed an anatomical thin titanium mesh (ATTM) plate for Asian orbital floor fracture based on the medical image database. The computer aided stamping analysis was performed on four hole/slot patterns included the control type without hole design, circular hole pattern, slot pattern and hole/slot hybrid patterns within the ATTM plate with upper/lower dies of averaged orbital cavity reconstruction models. The curved-fan ATTM plate with 0.4 mm thickness was manufactured and pre-bent using a patient matched stamping process to verify its feasibility and the interfacial fitness between the plate and bone on the orbital floor fracture model. The stamping analysis found that the hole/slot hybrid patterns design resulted in the most favorable performance among all designs owing to the lowest maximum von-Mises stress/strain and spring-back value. The interfacial adaption results test showed that the average patient-matched stamping bending gap size was only 0.821 mm and the operative time was about 8 s. This study concluded that the curved-fan ATTM plate with hole/slot hybrid pattern design and patient-matched pre-bent technique can fit the ATTM plate/orbital cavity interface well, decrease unstable fracture segment mobility and improve the overall reduction efficiency.

Longitudinal changes in intraocular pressure and association with systemic factors and refractive error: Lingtou Eye Cohort Study

OBJECTIVES

To investigate the longitudinal changes in intraocular pressure (IOP) and its associations with refractive error and systemic determinants in a Chinese geriatric population.

DESIGN

Prospective cohort study.

SETTING

Guangzhou Government Servant Physical Check-up Center, Guangzhou, China.

PARTICIPANTS

4413 government employees aged no less than 40 years (41.9% female) attending annual physical and eye examinations were included in this study. The inclusion criterion was having attended the 2010 follow-up examination. The exclusion criteria include glaucoma or intraocular surgery history, IOP >21 mm Hg at any visit or without available IOP data at all visits from 2010 to 2014.

PRIMARY AND SECONDARY OUTCOME MEASURES

The outcome measure was IOP at each follow-up visit from 2010 to 2014. Mixed-effect model was used to assess the relationship between longitudinal changes in IOP and potential risk factors.

RESULTS

For the 2653 participants who had available IOP data at both the 2010 and 2014 follow-up visits, the average change in IOP was an increase of 0.43 (95% CI 0.36 to 0.50) mm Hg. For the whole study population and in the optimised mixed model, there was a non-linear increase of IOP with age (P<0.001), with greater changes in younger subjects and in women (P<0.001 and P=0.002, respectively). Elevations in systolic blood pressure, diastolic blood pressure, body mass index (BMI) and fasting plasma glucose (FPG), as well as a myopic shift (all with P<0.001), during the follow-up were associated with an increasing trend of IOP, while serum lipids were found to be not significantly associated.

CONCLUSIONS

In this cohort of elderly Chinese adults, IOP increases non-linearly with ageing. People with increasing blood pressure, BMI, FPG and myopic progression are more likely to have IOP elevation over time.

Orbital Morphometry: A Computed Tomography Analysis

INTRODUCTION

The human orbit is a complex anatomic region, which plays predominant role in the evaluation of craniofacial complex. A thorough understanding of the relationship of the distance from orbital rim to the important vital structures of the orbital apex is required for the surgeon to perform safe and effective surgery.

OBJECTIVES

To evaluate and compare the depth and distances from various points of the orbital rim to the fissures and foramina of the orbital apex between genders in the local population.

METHODOLOGY

Linear measurements were conducted on 60 orbits from 30 patients who had undergone head computed tomography scan. These measurements were done utilizing the multiplanar reconstruction modes on computed tomography images with minimum slice thickness of 1 mm.

RESULTS

Males have statistically significant larger orbits than females with higher mean measurements in all parameters, except for the distance from posterior ethmoidal foramen to the optic canal which was the same. However, there were no significant differences in all parameters between the right and left orbits.

CONCLUSION

This study provides the absolute limit of safe internal orbital dissection in respect to the local population. Despite males having larger orbits than females, it is clinically negligible.

Osteologic analysis of ethnic differences in supernumerary ethmoidal foramina: implications for endoscopic sinus and orbit surgery

BACKGROUND

Knowledge of the position of the ethmoidal arteries is critical to enable safe endoscopic sinus and orbital surgery. The presence of a third or "middle" ethmoid variant has recently become more relevant as endoscopic intraconal surgery continues to advance. The purpose of this study was to quantify the presence of supernumerary (ie, over 2) ethmoid foramina in different ethnicities and genders.

METHODS

Morphometric osteologic measurements were performed in 273 orbits. Prevalence of supernumerary ethmoid foramina and orbital length data were obtained from human skulls of Asian (n = 54), Caucasian (n = 70), African (n = 39), Hispanic (n = 49), and Middle Eastern (n = 61) derivation. Correlations between gender, ethnicity, symmetry, orbital floor, and lamina papyracea length were assessed by analysis of variance, paired t test, and χ² test.

RESULTS

Supernumerary foramina were identified in 95 of 273 orbits (34.79%). A significantly higher prevalence was seen in Asian (42.59%), African (41.02%), and Hispanic (41.00%) skulls as compared with Caucasian (25.71%) and Middle Eastern (22.95%) skulls (p < 0.05 for all). The length of the orbital floor was significantly shorter in the Asian (3.35 ± 1.52 cm) specimens (p < 0.01). Asians were found to have the highest risk of ethmoid artery injury compared with the other ethnic groups (ratio of number of supernumerary foramina to orbital floor length = 0.72).

CONCLUSION

Supernumerary ethmoidal foramina were common among all orbits studied. Orbits of Asian and African derivation had significantly greater numbers of ethmoidal foramina, both unilaterally and symmetrically and within a shorter orbital length, suggesting a greater proximity between the ethmoidal vessels. Surgeons should be alert to the possible presence of middle ethmoidal vessels during endoscopic sinus and orbital approaches.

Orbital aperture morphometry in Indian population: A digital radiographic study

Background:

Morphological variations of the orbital aperture measurements may be used in forensic medicine as a parameter for determining sexual and ethnic identity of an individual.

Aim and Objective:

The aim and objective of this study was to evaluate the orbital aperture dimensions in Indian individuals and verify their relationship with gender.

Materials and Methods:

A retrospective study was conducted using digital posteroanterior view radiographs of 50 males and 51 females, which were taken using NEWTOM GIANO-CEFLA SC machine (81 kVp, 10 mA, and 6.6 s). The orbital aperture measurements were carried out using NEWTOM software NNT version 5.5. The maximum width and height of the orbits and the inter-orbital distance were measured. The obtained data were subjected to t-test and discriminant function analysis.

Results:

In the t-test, significant differences in orbital width and inter-orbital distance were obtained between the genders. On subjecting the data to discriminant function analysis, result was obtained with 86.1% accuracy rate in gender determination.

Conclusion:

If the discriminant score is >1.0365, the skull is likely to be of a male, and if it is <1.0365, it is likely to be of a female. Therefore, orbital aperture measurements can be used for gender determination in human identification.

The Combination of Ketorolac with Local Anesthesia for Pain Control in Day Care Retinal Detachment Surgery: A Randomized Controlled Trial

This study aims to evaluate the efficacy of ketorolac with local anesthesia compared to local anesthesia alone for perioperative pain control in day care retinal detachment surgery. The randomized controlled trial included 59 eyes of 59 participants for retinal detachment surgery who were randomly assigned (1 : 1) into the ketorolac (K) group and control (C) group. All participants underwent conventional local anesthesia while patients in the K group received an extra administration of preoperative ketorolac. Participants in the K group had a statistically significantly lower intraoperative NRS score (median 1.0 versus 3.0, P = 0.003), lower postoperative NRS score (median 0 versus 1.0, P = 0.035), fewer proportion of rescue analgesic requirement (10% versus 34.5%, P = 0.023), and lower incidence of postoperative nausea and vomiting (13.3% versus 41.4%, P = 0.015) compared to the C group. Intraocular pressure (IOP) changes (△IOP) were significantly reduced in the K group (median 1.9 versus 3.0, P = 0.038) compared to the C group 24 hours postoperatively. In conclusion, the combination of local anesthesia with ketorolac provides better pain control in retinal detachment surgery compared to local anesthesia alone. The beneficial effect of ketorolac with local anesthesia may contribute to a wider-spread adoption of day care retinal detachment surgery. This trial is registered with ClinicalTrials.gov NCT02729285.

Correction of Medial Blowout Fractures According to the Fracture Types

BACKGROUND

Regarding the issue of blowout fracture, a variety of approaches and surgical techniques have been reported to improve postoperative results. However, there are no extant guidelines for the selection of these various methods. The current authors classified the medial blowout fracture into 3 different types and adapted to suitable surgical techniques.

METHODS

Between October 2010 and March 2013, 89 patients who had medial blowout fracture were included in this study. We classified the study patients into 3 different categories: greenstick, simple, and complex. The greenstick type used the transnasal endoscopic approach and was reduced with packing after applying a silastic sheet. The simple type used an onlay covering technique. The complex type was treated using the transcaruncular approach and inlay implanting technique. After surgery, the continuity of orbital wall was checked by computed tomography. Patients were then examined for the following conditions: diplopia, eyeball movement, and enophthalmos.

RESULTS

The greenstick category consisted of 12 cases, most cases were satisfied. One case relapsed after removal of the packing. In the simple category, a total of 9 cases were treated by onlay covering technique. In all 68 cases of the complex type, we could obtain suitable anatomical reconstruction with inlay implanting technique. Only 2 cases complained of transient diplopia and moderate enophthalmos.

CONCLUSIONS

Appropriate clinical classification, depending on the type of fracture and selection of optimal treatment methods, could obtain the satisfactory result and improve the treatment outcomes in the correction of medial orbital wall fracture.

Predictability of Optic Foramen Location From a Ray Through the Ethmoidal Foramina

PURPOSE

To determine how accurately a ray through the anterior and posterior ethmoidal foramina predicts the location of the optic foramen.

METHODS

Dried, well-preserved, complete human skulls without bony defects belonging to the Hamann-Todd osteological collection of the Cleveland Museum of Natural History were examined. Photography was performed and a ray was drawn on orbit photographs extending through the center of the anterior and posterior ethmoidal foramina toward the optic canal. The location of the ray at the anterior aspect of the optic canal was recorded.

RESULTS

Sixty-six total orbits were examined from 36 skulls with 6 skulls with only unilateral data. Thirty-eight orbits were of African descent and 28 were of European descent with an average age 45.25 years (range = 19-89 years). The anterior-posterior ethmoidal foramen ray extended superior (12/66), through (53/66), and inferior (1/66) to the optic canal. Of those rays passing through the optic canal, 32/53 (60%) passed through the upper one-third, 19/53 (36%) passed through the middle one-third, and 2/53 (4%) passed through the lower one-third of the optic canal.

CONCLUSIONS

The anterior-posterior ethmoidal foramen ray highly predicts the superior aspect of the optic canal. This information can guide medial orbital wall surgery.

Positional Relationship of Ethmoidal Foramens With Reference to the Nasion and Its Significance in Orbital Surgery

PURPOSE

The aim of the study was to elucidate the positional relationship of the ethmoidal foramens (EFs) with reference to the nasion to facilitate prediction of the exact location of EFs, the optic canal (OC), and the frontoethmoidal suture (FS), and thereby avoid complications during complex surgery involving the medial wall of the orbit.

MATERIALS AND METHODS

One hundred two intact orbits of 57 embalmed cadavers were dissected in this observational anatomic study. Nasion' (N') was defined as the intersection point of the medial orbit margin with the horizontal line through the nasion, and this was used as a reference point. N'-OC was defined as the straight line joining N' and OC. The locations of the anterior ethmoidal foramen (AEF), posterior ethmoidal foramen (PEF), and OC were determined with reference to N'. The vertical distances from N'-OC to EFs and to FS were also determined.

RESULTS

The N'-AEF, AEF-PEF, and PEF-OC distances were 18.4, 15.3, and 8.3 mm, respectively. Vertically, AEF and PEF were situated at 0.2 mm below and 0.4 mm above N'-OC, respectively. At the same reference points, N'-OC was situated at 0.4 and 0.6 mm above FS, respectively.

CONCLUSIONS

N', AEF, PEF, and OC were considered to be situated on the same straight line, and N'-OC could be regarded as coinciding with FS. This means that N' is an easily identifiable and reliable landmark for identifying EFs, OC, and FS. Our navigational parameters with reference to N' will help surgeons to enhance the safety of orbital surgery.

Transorbital endoscopic identification of supernumerary ethmoid arteries

Background:

Anterior and posterior ethmoid arteries supply the paranasal sinuses, septum, and lateral nasal wall. Precise identification of these arteries is important during anterior skull base procedures, endoscopic sinus surgery, and ligation of ethmoid arteries for epistaxis refractory to standard treatment. There is controversy in the literature regarding the prevalence of supernumerary ethmoid arteries.

Objective:

This study examined the prevalence of supernumerary ethmoid arteries by using direct visualization after transorbital endoscopic dissection.

Methods:

Nineteen cadaveric specimens were evaluated by using a superior lid crease (blepharoplasty) incision and an endoscopic approach to the medial orbital wall. Ethmoid arteries were identified as they pierced the lamina papyracea coplanar with the skull base and optic nerve. The distances from the anterior lacrimal crest to the ethmoid arteries and optic nerve were measured with a surgical ruler under endoscopic guidance.

Results:

Thirty-eight cadaveric orbits were measured. Overall, there were three or more ethmoid arteries (including anterior and posterior arteries) in 58% of orbits, with 8% of the total sample that contained four or more ethmoid arteries. The average number of ethmoid arteries was 2.7. Bilateral supernumerary ethmoid arteries were noted in 42% of the specimens. The distance between the anterior lacrimal crest and the anterior ethmoid, posterior ethmoid, and optic nerve averaged 20, 35, and 41 mm, respectively. The average distance to the supernumerary or middle ethmoid artery was 29 mm.

Conclusion:

This study found supernumerary ethmoid arteries in 58% of cadaveric specimens, a prevalence much higher than previously reported. Recognition of these additional vessels may improve safety during endoscopic sinus surgery and skull base surgery, and may permit more effective ligation for refractory epistaxis originating from the ethmoid system.

Pediatric Orbital Depth and Growth: A Radiographic Analysis

BACKGROUND

Orbital reconstruction requires knowledge of orbital depth in order to prevent optic nerve injury. Numerous analyses of adult orbital dimensions have been undertaken previously in order to characterize this measurement, including skull specimen and computerized tomography studies. However, there is a paucity of information regarding the pediatric orbit.

METHODS

The authors used pediatric magnetic resonance imaging (MRI) studies in order to quantify the change in orbital depth in relationship to patient age, and to develop methods to estimate and calculate orbital depth for individual pediatric patients. MRIs of the head in normal pediatric patients were reviewed retrospectively. Orbital depths were measured and correlated with age and cephalometric dimensions. In a randomly selected subgroup of patients, measurements were repeated by an independent investigator to determine interobserver reliability.

RESULTS

Measurements were obtained in 72 patients ranging from 3 months to 18 years of age (mean=7.8 years). There was a significant exponential relationship between orbital depth and patient age (r=0.81, F(2,69)=143.97, P<0.001). Depth increased more rapidly in the first 6 years of life, but leveled off in the early teen years toward a horizontal asymptote of approximately 45 mm. There was also a significant relationship between orbital depth and the sum of the biparietal width plus the anterior-posterior length (r=0.72, F(2,69)=87.44, P<0.0001). There was high interobserver reliability in measurements between 2 independent investigators (r=0.79, P<0.0001).

CONCLUSION

In children, orbital depth increases predictably with rising age and increasing head size. Knowledge of this growth curve and the relationship between head size and orbital depth can complement careful surgical dissection to improve safety and efficacy in pediatric orbital reconstructions.

Clinical and surgical implications regarding morphometric variations of the medial wall of the orbit in relation to age and gender

The ethmoidal foramens are located on the medial wall of the orbit and are key reference points for intraoperative orientation. Detailed knowledge of the anatomy, bony landmarks and morphometric characteristics of the medial wall of the orbit is essential for various surgical procedures. The aim of this study was to determine the morphometric variations in the medial wall of the orbit and establish significant variations regarding age and gender. A total of 110 orbits were analyzed and subdivided by age (over or under 40 years) and gender. The distances of the medial wall of the orbit between the anterior lacrimal crest, the ethmoidal foramen, the optic canal and the interforamina were determined. Safe surgical areas were sought. Statistical tests were used to determine the differences between groups. In men, there is a safe surgical area proximal to the anterior and posterior ethmoidal foramen. In women, this area is in the posterior third of the medial wall of the orbit between the posterior ethmoidal foramen and the optic canal. Regarding variation according to age, the results of this study suggested that the anteroposterior diameter of the medial wall increases with age. This study showed that the anteroposterior total length of the medial orbit wall is similar between genders of similar age, increases with age, and has significant variations in the distances between the various structures that make up the medial orbit wall with regard to gender and age.

Anatomy of anterior ethmoidal foramen, medial canthal tendon, and lacrimal fossa for transcutaneous anterior ethmoidal nerve block in Japanese individuals

PURPOSE

To examine the anatomical relationships of the anterior ethmoidal foramen (AEF), medial canthal tendon (MCT), and lacrimal fossa (LF) in Japanese individuals.

METHODS

Thirty-eight orbits from 19 Japanese cadavers (7 men and 12 women; average age at death, 89.3 years) were used in this experimental anatomical study. The AEF, MCT, and superior border of the LF were exposed. The following distances were then measured: 1) from the point at the medial orbital rim directly anterior to the AEF to the superior border of the MCT (AEF-MCT), and 2) from the superior border of the LF to the superior border of the MCT (LF-MCT).

RESULTS

(AEF-MCT) and (LF-MCT) distances were 9.40±1.92 (mean±standard deviation) and 4.21±1.18 mm, respectively. No values of (LF-MCT) exceeded the mean (AEF-MCT) (9.40 mm).

CONCLUSIONS

The transcutaneous anterior ethmoidal nerve block can be reliably performed without injury to the lacrimal sac by inserting a needle approximately 9 mm superior to the superior border of the MCT.

Medial orbital wall landmarks in three different North American populations

PURPOSE

We sought to measure the medial orbital wall foramina distances in two previously unstudied populations, to describe a new bony medial wall feature, and to validate the accuracy of a new coordinate measurement device within the orbit.

METHODS

Dried, well-preserved, complete human skulls without orbital defects were studied. Age, gender, birthplace, ethnicity, and laterality of the orbit were recorded for each skull. Supranumerary ethmoidal foramina were recorded, and the fronto-ethmoidal groove depth was measured. The distances between the anterior lacrimal crest (ALC) - anterior ethmoidal foramen (AEF), AEF - posterior ethmoidal foramen (PEF), and PEF - optic canal (OC) were measured first by surgical ruler and wire and then by the Microscribe coordinate measurement device.

RESULTS

One hundred and forty-six orbits were studied. Fifty-seven orbits were of European or Caucasian descent, 68 orbits of African American descent, 2 orbits of West African descent, 11 orbits of Eskimo descent, and 8 orbits of unknown origin. No significant differences existed between the manual and Microscribe measurements for the ALC-AEF, AEF-PEF, and PEF-OF distances (p < 0.0001). A significant frontoethmoidal groove was observed in 27/146 (19%) orbits, in 6/57 (11%) Caucasian orbits, in 17/70 (24%) African American orbits, and in 4/11 (36%) Eskimo orbits. Supranumerary ethmoidal foramina were found in 50/146 orbits (34.2%) and in 17/27 (63%) orbits with a significant frontoethmoidal grooves.

CONCLUSIONS

No significant differences in medial wall foramina distances exist between African American and Caucasian orbits; however, a frontoethmoidal groove occurs more commonly in African American orbits. This groove often occurs in the presence of supernumerary ethmoidal foramina. The Microscribe coordinate measurement system represents a valid tool to measure distances within the orbit.

Three-dimensional evaluation of the danger zone of ethmoidal foramens on the frontoethmoidal suture line on the medial orbital wall

INTRODUCTION

It is clear that the importance of the ethmoidal foramen (EF) is based on its vascular contents. The frontoethmoidal suture (FS) line is recommended as more reliable navigational landmark for identifying the EF.

MATERIALS AND METHODS

The vertical orientation between the EF and the FS line was studied in 188 orbits using a computer software program.

RESULTS

146 anterior EFs (77.7 %) and 42 anterior EFs (22.3 %) were situated in the FS line as intrasutural and extrasutural, respectively. 146 posterior EFs (77.25 %) and 8 posterior EFs (4.25 %) were presented as intrasutural and extrasutural, respectively. Although accessory EFs were detected in 25.5 % specimen exhibited an extrasutural location. Majority of the EFs (1-4 EFs) were situated on the FS line. The mean distances from the FS and the anterior EF, the posterior EF and the accessory EF were measured as 2.1 ± 0.5, 2.0 ± 1.5 and 2.3 ± 1.2 mm, respectively. The range of the distances from the FS to the anterior EF, posterior EF and accessory EF were -1.2 to 3.32 , -1.02 to 5.76 and -1.1 to 3.65 mm, respectively.

CONCLUSION

The ranges of EF changed within 1-6 mm. As the FS is not a single point, it is more suitable to make the incision 7 mm above the suture line. The data from this study to help the orbital surgeons explain and avoid unexpected hemorrhage during the orbital procedures such as posttraumatic orbital reconstruction, orbital tumor resections, anterior skull base reconstruction, and orbital decompression surgery.

Orbital blowout fracture location in Japanese and Chinese patients

PURPOSE

To characterize the location of orbital blowout fractures in Asian individuals.

METHODS

This was a retrospective review of 470 consecutive Asian patients with orbital blowout fractures who presented to four tertiary care hospitals in Japan and China. Computed tomography (CT) characterized the location and severity of fractures involving the medial wall, the orbital floor, and/or the maxilloethmoidal strut.

RESULTS

A total of 475 orbital blowout fractures were identified. More than one fracture location was involved in 19% of all cases. The medial orbital wall was the most commonly involved location, presenting in 29 cases (61%), of which 204 (43%) were isolated medial blowout fractures. The orbital floor was the second most common location involved, present in 226 cases (48%) with 150 isolated orbital floor fractures (32%), while the maxilloethmoidal strut was involved in 45 cases (9%) with 30 of those being isolated strut fractures (6%). The majority of fractures (62%) were classified as moderately severe, whilst 14% were mild, and 24% were severe. Associated nasal fractures were present in 16% of the cases.

CONCLUSIONS

Orbital blowout fractures in Japanese and Chinese individuals occur most commonly in the medial wall. This is in contrast to previous reports on white individuals, who tend to sustain fractures involving the orbital floor rather than the medial wall.

Three-dimensional pre-bent titanium implant for concomitant orbital floor and medial wall fractures in an East asian population

Background

The objective of this article is to evaluate clinical outcomes of combined orbital floor and medial wall fracture repair using a three-dimensional pre-bent titanium implant in an East Asian population.

Methods

Clinical and radiologic data were analyzed for 11 patients with concomitant orbital floor and medial wall fractures. A combined transcaruncular and inferior fornix approach with lateral canthotomy was used for the exposure of fractures. An appropriate three-dimensional preformed titanium implant was selected and inserted according to the characteristics of a given defect.

Results

Follow-up time ranged from 2 to 6 months (median, 4.07 months). All patients had a successful treatment outcome without any complications. Clinically significant enophthalmos was not observed after treatment.

Conclusions

Three-dimensional pre-bent titanium implants are appropriate for use in the East Asian population, with a high success rate of anatomic restoration of the orbital volume and prevention of enophthalmos in combined orbital floor and medial wall fracture cases.

Prevalence of high astigmatism in children aged 3 to 6 years in Guangxi, China

PURPOSE

To investigate the prevalence and type of high astigmatism among children aged 3 to 6 years in Guangxi, a relatively undeveloped province in western China, and to examine the correlation between astigmatism and visual acuity.

METHODS

Children aged 3 to 6 years in Nanning, the capital of Guangxi Province, participated in a population-based survey using a cluster random sampling technique. Eye examinations included autorefraction, visual acuity measurements, and assessments of the external eye, anterior segment, media, and fundus. Data for the right eyes were analyzed.

RESULTS

Among the 2304 children examined, the overall prevalence of high astigmatism (≥1.25 diopters by noncycloplegic SureSight autorefraction) was 12.7% (95% confidence interval, 11.3 to 14.0%). The age-specific prevalences of high astigmatism in 3-, 4-, 5-, and 6-year-old children were 13.8, 13.2, 12.9, and 8.1%, respectively. The prevalence of high astigmatism did not vary with age or gender (p > 0.05). The majority of cases of high astigmatism were with-the-rule astigmatism (82.9%), followed by against-the-rule (12.6%) and oblique (4.5%) astigmatism. A linear correlation was found between astigmatism magnitude and visual acuity (logMAR acuity = 0.068 + 0.055 × astigmatism) in all participants. Multiple linear regression analysis further showed that the correlation of astigmatism with visual acuity was magnitude dependent (β = 0.240). When with-the-rule astigmatism was used as a reference group, against-the-rule astigmatism (β = 0.137) and oblique astigmatism (β = 0.154) were closely correlated with visual acuity.

CONCLUSIONS

High astigmatism was moderately prevalent among children aged 3 to 6 years in Guangxi Province. With-the-rule astigmatism was the dominant form of astigmatism. Magnitude- and orientation-dependent correlations of astigmatism with visual acuity were confirmed.

Endoscopic anatomy of the middle ethmoidal artery

BACKGROUND

The purpose of this study was to describe the incidence of the middle ethmoidal artery and its anatomical nuances via an endoscopic endonasal approach.

METHODS

A cadaveric study was performed on 22 adult specimens. First, a frontal sinusotomy and ethmoidectomy were performed via an endoscopic endonasal approach in order to fully expose the anterior skull base. Subsequently, the lamina papyracea and the bone of the canals covering the ethmoidal neurovascular bundles were removed to identify the anterior, middle, and posterior ethmoidal arteries. Presence, laterality, and location of the middle ethmoidal artery were recorded.

RESULTS

A total of 14 middle ethmoidal arteries were identified (10 right and 4 left), among 44 sides (22 specimens), accounting for an incidence of 31.8%. Bilateral middle ethmoidal arteries were found in 3 of 22 specimens (14%). Endonasal endoscopy features of the middle ethmoidal artery were noted.

CONCLUSION

This is the first study assessing the anatomical features of the middle ethmoidal arteries from an endonasal endoscopic perspective. The findings of this research have clinical significance in guiding surgeries that involve the medial orbital wall, intractable epistaxis, and anterior skull base pathologies, as well as endoscopic endonasal surgeries.

Anatomy of deep lateral and medial orbital walls: implications in orbital decompression surgery

BACKGROUND

Isolated deep lateral and combined medial orbital wall decompressions (balanced decompression) are well accepted for treatment of disfiguring proptosis and compressive optic neuropathy in patients with Graves' orbitopathy. However, cerebrospinal fluid leakage and/or optic nerve injury occasionally occur during these operations.

PURPOSE

To describe the anatomy of the deep lateral and medial orbital walls and its surgical implications in orbital decompression.

METHODS

We reviewed literature on the anatomy of the deep lateral and medical orbital walls. In addition, we performed cadaver dissection and computed tomographics studies to illustrate the anatomy.

RESULTS

We provided an anatomical overview and elucidated the detailed surgical anatomy of the posterior and superior borders of the deep lateral orbital wall, the posterior and accessory ethmoidal foramina, and the frontoethmoidal suture.

CONCLUSIONS

The anatomy of the deep lateral and medical orbital walls presented here will warrant safe and confident performance of orbital decompression surgery.

Infraorbital foramen: horizontal location in relation to ala nasi

PURPOSE

To examine the horizontal location of the infraorbital foramen in relation to the ala nasi.

METHODS

Fifty-six orbits of 28 Japanese cadavers (18 male and 10 female cadavers; average death age, 79.7 years), fixed in 10% buffered formalin, were used. The horizontal distance from the vertical line through the lateral margin of the ala nasi to the medial margin of the infraorbital foramen (the horizontal distance) and the transverse diameter of the infraorbital foramen (the transverse diameter) were examined. Values were compared between genders and sides using Student's t test.

RESULTS

The mean horizontal distance was 4.9 mm, with no significant difference between genders (male, 5.2 mm; female, 4.4 mm; p = 0.150) or sides (right, 4.9 mm; left, 4.9 mm; p = 0.944). The mean transverse diameter was 5.5 mm. Although there was no significant difference in this diameter between sides (right, 5.3 mm; left, 5.6 mm; p = 0.358), there was a significant difference between genders (male, 5.7 mm; female, 5.1 mm; p = 0.033).

CONCLUSION

The horizontal distance had no gender difference. This value is available irrespective of gender in surgery.

Morphometric and geometric anatomy of the caucasian orbital floor

INTRODUCTION

To describe the morphometric and geometric relationships of the orbital floor in a Caucasian population.

MATERIALS AND METHODS

Exenterations of 47 orbits from 24 formalin fixed cadavers were performed. Morphometric measurements were taken between anatomical landmarks located along the orbital floor and the orbital apex. The mean measurements were used to calculate geometric data. These results were analysed according to sex and side and compared to results from other ethnic populations.

RESULTS

The average distances from the infraorbital foramen to the nasolacrimal fossa, inferior orbital fissure, optic canal and inferior orbital rim were 20.67 mm (± 2.42), 25.40 mm (±2.70), 43.23 mm (±3.35) and 8.95 mm (± 1.53), respectively. The average distances from the tip of the infraorbital groove to the tip of the inferior orbital fissure, lateral aspect of the inferomedial strut, optic canal and the intersection with the inferior orbital fissure were 14.08 mm (±2.41), 12.12 mm (±2.42), 35.02 mm (±3.17) and 20.05 mm (± 2.87), respectively. The distances from the tip of the inferior orbital fissure to the optic canal and the intersection with the inferior orbital groove were 29.56 mm (±2.73) and 13.37 mm (±2.76), respectively.

DISCUSSION

Orbital surgeons should be aware of the morphometric relationships of the orbital floor due to the degree of variation that exists between different ethnic groups. Geometric data may be used to provide orbital surgeons with a navigational template that can be used to plan surgery and as a guide intraoperatively.

Inlay implanting technique for the correction of medial orbital wall fracture

BACKGROUND

For blowout fractures of the medial orbital wall, the goals of treatment are complete reduction of the herniated soft tissue and anatomical restoration of the orbital wall without surgical complications. Surgeons frequently worry about damage to the optic nerve caused by dissection when the part over the posterior ethmoidal foramen is fractured. The authors performed small incision and inlay implantation of porous polyethylene for reconstruction of medial orbital wall fractures.

METHODS

Between January of 2007 and December of 2009, 55 patients were included in an analysis of the outcome of corrected medial orbital wall fractures. For 55 patients with posterior comminuted fractures of the medial orbital wall, insertion of porous polyethylene into the ethmoid sinus was performed in multiple layers, through the transconjunctival approach.

RESULTS

In all cases, the orbital cavity was restored to its normal anatomical shape. The associated ocular problems disappeared except for mild enophthalmos in three patients and diplopia in one patient. There were no serious surgical complications associated with inlay implantation.

CONCLUSIONS

The advantages of the inlay technique include the anatomical reconstruction of the orbital wall, the avoidance of optic nerve injury, the simplicity of the procedure, and consequently the absence of surgery-related complications. This technique is presented as one of the preferred treatments for posterior comminuted fractures of the medial orbital wall.

A cadaveric study of the morphometric and geometric relationships of the orbital apex

INTRODUCTION

To define the morphometric and geometric relationships which exist at the orbital apex.

MATERIALS AND METHODS

Forty-seven orbits from twenty-four formalin-fixed Caucasian cadavers were exenterated and the relevant sutures, fissures and foramina identified. Measurements were taken from the optic canal to anatomical landmarks located along the medial wall, inferior wall and lateral wall of each orbit. Based on the mean results the geometric angles between the different anatomical structures were calculated and used to create three-dimensional models.

RESULTS

The mean distances from the midpoint of the optic canal to the superior orbital fissure, inferior orbital fissure and anterior ethmoidal foramen were 10.22 mm, 29.56 mm and 21.65 mm, respectively. The mean distances from the anterior ethmoidal foramen to the superior and inferior orbital fissures were 24.27 mm and 31.93 mm, respectively. The mean distance between the tips of the superior and inferior orbital fissures was 27.70 mm. The mean distances directly from the tips of the superior and inferior orbital fissures and the anterior ethmoidal foramen to the orbital rim were 39.23 mm, 17.11 mm and 18.94 mm, respectively. These values were used to calculate geometric values and create three-dimensional models.

DISCUSSION

The orbital apex is a congested structure and the practicing orbital surgeon must have an intimate knowledge of its contents. We have presented novel data, which in conjunction with radiology may be used as both a navigational aid to plan orbital surgery and to guide the surgeon intraoperatively to assess proximity to key anatomical structures.

Astigmatism in preschool children in Taiwan

PURPOSE

To elucidate the prevalence of astigmatism and its corneal component, the association between the amount of astigmatism and its axis, and the association between the axis of astigmatism and body mass index (BMI) in Taiwanese preschool children.

METHODS

In this population-based study we analyzed 2 data sets, one obtained by retrospective review of vision-screening data and another obtained in a prospective observational study. Each study collected data for age, sex, and refraction status. Autokeratometry, height, and weight measurements were obtained only in the observational study. Astigmatism was classified as with-the-rule, against-the-rule, or oblique.

RESULTS

The prevalence of astigmatism was unassociated with age or sex in both data sets. The retrospective study (1,094 subjects; mean age, 5 years; range, 2.19-7.32 years) revealed that 13.3% of the subjects had astigmatism > or = 1.00 D, and most of them had with-the-rule astigmatism; 4.0% had high astigmatism (>1.50 D). Children with with-the-rule astigmatism had greater mean cylinder power than those with against-the-rule or oblique astigmatism. In the prospective study (190 subjects; mean age, 5.65 years; range, 3.79-6.68 years) astigmatism correlated with its corneal component. Preschoolers with with-the-rule astigmatism and with-the-rule corneal astigmatism had greater BMI and heavier weight than those with against-the-rule or oblique type.

CONCLUSIONS

Astigmatism is common in Taiwanese preschool children. The predominant types are with-the-rule and oblique astigmatism. Most patients with high astigmatism and high corneal astigmatism have with-the-rule type. High BMI or weight is associated with with-the-rule astigmatism and with with-the-rule corneal astigmatism.