Cone-beam computed tomography of the orbit and optic canal volumes

Orbital Dynamics and Efficacy of Retrobulbar Anesthesia With and Without Hyaluronidase in Vitreoretinal Surgery

Purpose: To compare retrobulbar anesthesia injection (RAI) with hyaluronidase and without hyaluronidase in vitreoretinal surgery using clinical efficacy measures and orbital manometry (OM). Methods: This prospective randomized double-masked study enrolled patients who had surgery using an 8 mL RAI with or without hyaluronidase. Outcome measures were clinical block effectiveness (akinesia, pain scores, need for supplemental anesthetic or sedative medications) and orbital dynamics assessed by OM before and up to 5 minutes after RAI. Results: Twenty-two patients received RAI with hyaluronidase (Group H+), and 25 received RAI without hyaluronidase (Group H-). Baseline characteristics were well matched. No differences in clinical efficacy were found. OM showed no difference in preinjection orbital tension (4 ± 2 mm Hg in both groups) or calculated orbital compliance (0.6 ± 0.3 mL/mm Hg, Group H+; 0.5 ± 0.2 mL/mm Hg, Group H-) (P = .13). After RAI, the peak orbital tension was 23 ± 15 mm Hg in Group H+ and 24 ± 9 mm Hg in Group H- (P = .67); it declined more rapidly in Group H+. Orbital tension at 5 minutes was 6 ± 3 mm Hg in Group H+ and 11 ± 5 mm Hg in Group H- (P = .0008). Conclusions: OM showed faster resolution of post-RAI orbital tension elevation with hyaluronidase; however, there were no clinically evident differences between groups. Thus, 8 mL RAI with or without hyaluronidase is safe and can achieve excellent clinical results. Our data do not support the routine use of hyaluronidase with RAI.

Orbital Aging: A Computed Tomography-Based Study of 240 Orbits

BACKGROUND

Previous studies have attempted to explain age-related changes to the orbit in isolation, often producing conflicting results. The authors used highly accurate imaging software to analyze computed tomographic scans to characterize changes related to age objectively.

METHODS

In this case-control study, patients seen in an ear, nose, and throat clinic were screened for study entry. Male and female participants were divided into two age groups (20 to 30 years and 60 to 75 years). Primary outcomes included measurement of bony orbital dimensions, volume of soft tissues (muscle and fat volume), and anterior globe position. Three-dimensional reconstructions were created of each orbit allowing these measurements. The generalized estimating equation was used so that both orbits from each patient could be included without any bias.

RESULTS

The final sample included 240 orbits from 120 patients. There were 30 patients in each age group. Among female participants, the bony orbital volume ( p < 0.05), fat volume ( p < 0.01), and central width ( p < 0.001) of the bony orbit increased with age. The anterior globe position was significantly greater in older female participants ( p < 0.01). For male participants, the fat volume ( p < 0.0001) and central height ( p < 0.03) increased with age; the lateral rim moved posteriorly with age ( p < 0.007). The anterior globe position was not different between the age groups in male participants ( p = 0.56).

CONCLUSION

The female bony orbit expands with age and is associated with a more anterior position of the globe; the male bony orbital volume remains the same and the lateral rim moves posteriorly.

Optic Canal Analysis in Syndromic Craniosynostosis: Volumetric and Surface Area Validation Study Using Different Measurement Modalities

BACKGROUND

In syndromic craniosynostosis (SC), unlike persistent corneal irritation due to severe exophthalmos and increased intracranial pressure, optic canal (OC) stenosis has been scarcely reported to cause visual impairment. This study aimed to validate the OC volumetric and surface area measurement among SC patients.

METHODS

Sixteen computed tomography scan of SC patients (8 months-6 years old) were imported to Materialise Interactive Medical Image Control System (MIMICS) and Materialise 3-matics software. Three-dimensional (3D) OC models were fabricated, and linear measurements were obtained. Mathematical formulas were used for calculation of OC volume and surface area from the 3D model. The same measurements were obtained from the software and used as ground truth. Data normality was investigated before statistical analyses were performed. Wilcoxon test was used to validate differences of OC volume and surface area between 3D model and software.

RESULTS

The mean values for OC surface area for 3D model and MIMICS software were 103.19 mm2 and 31.27 mm2, respectively, whereas the mean for OC volume for 3D model and MIMICS software were 184.37 mm2 and 147.07 mm2, respectively. Significant difference was found between OC volume (P = 0.0681) and surface area (P = 0.0002) between 3D model and software.

CONCLUSION

Optic canal in SC is not a perfect conical frustum thus making 3D model measurement and mathematical formula for surface area and volume estimation not ideal. Computer software remains the best modality to gauge dimensional parameter and is useful to elucidates the relationship of OC and eye function as well as aiding intervention in SC patients.

Orbital Volume Increases With Age: A Computed Tomography-Based Volumetric Study

OBJECTIVE

The aim of the study was to determine whether the bony orbital volume (BOV) changes with age in males and females.

METHODS

This case-control study reviewed high-resolution (<1-mm slices) computed tomography (CT) scans of consecutive patients seen for 4 years. The scans were requested as part of the patient's routine care for symptoms related to sinus symptoms. Eligible participants were adults aged between 18 and 30 years and 60 and 75 years. Exclusion criteria included previous surgery, any medical conditions that might affect the bone or soft tissue of the orbit, and any abnormalities seen on imaging. Male patients aged between 18 and 30 years were compared with males aged 60 to 75 years. The same was done for females. The main outcome measure was measurement of the BOV. Both orbits of each patient were included using the generalized estimating equation, to avoid any bias from correlation between 2 orbits of the same patient.

RESULTS

A total of 240 orbits from 120 patients were used for this study. Each age group contained 30 patients. There were no significant differences in the ages between males and females in each age category (P = 0.88 for ages 20-30 years and P = 0.74 for ages 60-75 years). The mean (SD) BOV for females aged between 20 and 30 years was 19,153.69 mm (3776.21), whereas that for females aged between 60 and 75 years was 20,939.38 mm (2837.34). The difference between the groups was significant (Pr(>|W|) = 0.05). The mean (SD) BOV for males aged between 20 and 30 years was 22,2721 mm (2977.35), whereas that for males aged between 60 and 75 years was 22,892.92 mm (2389.46) (Fig. 1). The difference between these 2 groups was not significant (Pr(>|W|) = 0.40). The mean BOV was significantly greater for males than females (P ≤ 0.01) across both age groups.

CONCLUSIONS

This study found that female orbits expand with age, whereas male orbits showed no significant changes. Changes to the orbital volume in females may contribute to the appearance of aging.

Morphometric and Volumetric Measurements of Orbit With Cone-Beam Computed Tomography

PURPOSE

The purpose of this study was to determine cone-beam computed tomography (CBCT) as a tool for measuring morphometric and volumetric measurements of the orbit. Also, to assess gender and age variations and compare traditional methods of measurements in dry-skull, cadaveric, and other imaging modalities.

PATIENTS AND METHODS

Morphometric and volumetric values of 98 orbits (49 subjects, 21 men/28 women) were measured using CBCT. Their mean and standard deviation were measured and analyzed. The gender and age variability older and younger than 40 years were evaluated. They were compared with other dry-skull and imaging studies done among different populations.

RESULTS

CBCT could accurately measure the various morphometric and volumetric parameters of the orbit. From the reference point infraorbital foramen (I) to lacrimal fossa (F1), inferior orbital fissure (F2), inferior orbital rim (F3), and the optic canal (F4) were (in mm) (mean ± SD) 22.88 ± 1.08, 32.53 ± 0.88, 7.44 ± 0.71, and 51.45 ± 1.28, respectively. From the reference point, superior orbital notch/foramen (S) to superior orbital fissure (S1), lacrimal fossa (S2), and the optic canal (S3) were 49.29 ± 2.1, 26.39 ± 1.58, and 46.82 ± 0.88, respectively. From the reference point frontozygomatic suture (L) to lacrimal fossa (L1), superior orbital fissure (L2), the optic canal (L3), and inferior orbital fissure (L4) were 18.19 ± 0.88, 39.91 ± 1.44, 47.63 ± 1.11, and 35.19 ± 1.02, respectively. Orbital volume was found to show a significant difference between older and younger than 40 years of age, though not significant compared between men and women.

CONCLUSION

CBCT is a viable tool for morphometric and volumetric measurements of the orbit and other orocraniofacial structures. It can also assess age and gender variability. The low cost, high accuracy, low radiation, and ease of use can help in reproducibility among the different living populations.

Longitudinal Changes in Adult Bony Orbital Volume

PURPOSE

To our knowledge, no prior study has measured bony orbital volume in a group of subjects over time. This study evaluates longitudinal changes in bony orbital volume with age.

METHODS

A search was created for patients with digitized CT imaging studies of the orbit at least 8 years apart. Charts with a history of prior head trauma, head and neck tumors, sinus disease, head surgery, elevated intracranial pressure, thyroid eye disease, or conditions that could affect bone metabolism were excluded. Three outcome measures were used: orbital volume, medial orbital wall length, and lateral orbital wall length. Categorical data were summarized with frequency (%); normally distributed continuous data are summarized with mean (standard deviation), and non-normally distributed data were summarized with median. Normality was verified with Shapiro-Wilk Test. Paired t-tests were used to analyze the differences in the 3 outcome variables.

RESULTS

One hundred and eighty-two subjects, 91 males and 91 females, were included. The median time between CT scans was 9.4 years. Orbital volume was significantly larger at the second scan than the first (p < 0.001). The average difference in orbital volume was 0.91 ml, an increase of 4.1%. Lateral orbital length was significantly shorter in the second scan than in the first (p = 0.046) though the difference was only 0.4 mm. There was no statistically significant change in medial orbital wall length.

CONCLUSIONS

Bony orbital volume increases in individuals with age. This increase in orbital volume occurs in the context of soft tissue changes to contribute to the aging appearance of the periorbital region.

A combination of skeletal deformations of the dorsal mandible and temporomandibular region detected in orthopantomograms of patients with neurofibromatosis type 1 indicates an associated ipsilateral plexiform neurofibroma

PURPOSE

Neurofibromatosis type 1 (NF1) is a tumour suppressor syndrome and also a bone disease. In the craniofacial region, local skeletal deformities have been recorded in patients with NF1. Obvious syndrome-related alterations of the jaws are particularly conspicuous in the mandible. Here we aimed to analyse the mandibular alterations of NF1-affected individuals from orthopantomograms (OPGs).

MATERIALS AND METHODS

This study analyses 358 OPGs of 358 patients (mean age, 34.63 years; range, 12.57-69.13 years). The OPGs of 179 patients of Caucasian origin with NF1 were investigated (mean age, 34.84 years; range, 12.83-68.89 years; 44.13% male, 55.86% female). The radiographic findings were compared to those obtained from OPGs of sex- and age-matched controls.

RESULTS

Characteristic deformations of the bone regions of interest occur in NF1 patients, especially in patients with plexiform neurofibroma of trigeminal nerve. These findings are always one-sided. The co-occurrence of several skeletal deformations can be expected with very high probability in this patient group.

CONCLUSION

The radiological sign of the unilateral deformed mandible should be included in the diagnostic criteria for NF1. In addition to the diagnostic value in this syndrome, these findings are important for avoiding surgical complications in planned interventions in this region.

Accuracy of Bone Measurements in the Vicinity of Titanium Implants in CBCT Data Sets: A Comparison of Radiological and Histological Findings in Minipigs

Purpose

The aim of this animal study was the determination of accuracy of bone measurements in CBCT (cone-beam computed tomography) in close proximity to titanium implants.

Material and Methods

Titanium implants were inserted in eight Göttingen minipigs. 60 implants were evaluated histologically in ground section specimen and radiologically in CBCT in regard to thickness of the buccal bone. With random intercept models, the difference of histologic measurements and CBCT measurements of bone thickness was calculated.

Results

The mean histological thickness of the buccal bone was 5.09 mm (CI 4.11–6.08 mm). The four raters measured slightly less bone in CBCT than it was found in histology. The random effect was not significant (p value 1.000). Therefore, the Intraclass Correlation Coefficient (ICC) was 98.65% (CI 100.00–96.99%).

Conclusion

CBCT is an accurate technique to measure even thin bone structures in the vicinity of titanium implants.

The Optic Canal: A Bottleneck for Cerebrospinal Fluid Dynamics in Normal-Tension Glaucoma?

Purpose

To report on the optic canal cross-sectional area (OCA) in Caucasian patients with normal-tension glaucoma (NTG) compared with Caucasian control subjects without known optic nerve (ON) diseases.

Methods

Retrospective analysis of computed tomographic images of the cranium and orbits in 56 NTG patients (30 females and 26 males; 99 of 112 eyes; mean age 67.7 ± 11.1 years). Fifty-six age- and gender-matched subjects (mean age: 68.0 ± 11.2 years) without known ON diseases served as controls. The OCA at the orbital opening was measured in square millimeters by using the tool “freehand.” Statistical analysis was performed by using the independent two-tailed t-test.

Results

The mean orbital opening OCA in NTGs measured 14.5 ± 3.5 mm² (right OCA: 14.4 ± 3.6 mm², left OCA: 14.5 ± 3.4 mm²) and in controls measured 18.3 ± 2.6 mm² (right OCA: 18.5 ± 2.7 mm², left OCA: 18.1 ± 2.5 mm²). The difference between NTG and controls was statistically significant (p < 0.000 for the right OCA, p < 0.000 for the left OCA).

Conclusion

This study demonstrates narrower OCAs in Caucasian NTG patients compared with Caucasian control subjects without known ON diseases. Narrower OCAs might contribute to a discontinuity of the cerebrospinal fluid flow between the intracranial and orbital subarachnoid space in NTG patients. This might have an influence onto the pathophysiology in NTG.