Soft Tissue Robotic Assisted Orbital Surgery Using da Vinci SP: A Cadaveric Experience.

PURPOSE: Robotic surgical techniques have transformed many surgical specialties however robotic techniques and applications have been much more limited in ophthalmology. This study aims to evaluate the feasibility of robotic assisted orbital surgery using a single-port novel robotic platform, the da Vinci SP. METHODS: A series of orbital procedures were performed in cadaveric specimens utilizing the da Vinci SP robotic system. The procedures performed included lacrimal gland dissection and biopsy, medial and lateral orbital wall dissections, enucleation, and lid-sparing orbital exenteration. Successful completion of each procedure was defined by the operating surgeon and was considered the primary outcome and marker of feasibility. RESULTS: Seven cadaveric procedures were performed in 3 cadaveric specimens. All 7 procedures were completed successfully without complication. Setup optimization occurred throughout the study and setup and operative times were acceptable. Three instrument arms and 1 endoscope were utilized throughout the study allowing 3 arm operating and dynamic retraction. Instrument size was found to limit surgical access and precision particular at the orbital apex. CONCLUSIONS: This preclinical study demonstrates that the da Vinci SP can be utilized within the orbit and is feasible for several applications. Robotic surgical systems offer significant advantages over conventional techniques and should be embraced. However, current commercially available robotic platforms are not optimized for the orbit and have their limitations although they may be suitable for some clinical applications.

Orbital Crystal-Storing Histiocytosis: A Clinicopathologic Study of 4 Cases.

The authors report the clinicopathological features of crystal-storing histiocytosis (CSH) that involved the orbit and conjunctiva and review published cases of CSH. Cases of histologically proven CSH were identified from archives at the Institute of Ophthalmology, London, and a retrospective review of clinical details and pathology was performed for cases between 1997 and 2017. Four cases of CSH were identified: 1 might have arisen from an inflammatory reaction to a silicone retinal buckle and 3 others occurred with localized B-cell lymphomas. Two patients presented with a conjunctival mass, and 2 had an orbital mass causing proptosis and hypoglobus. One case was associated with amyloid deposition and another had an earlier diagnosis of IgG4-related disease. In the patient without underlying lymphoma, the condition settled with removal of the explant and orbital mass, and the 3 with lymphoma underwent orbital radiotherapy with cessation of disease progression. All patients retained good vision. Ocular CSH is rare, can present in several ways, and should prompt investigation for an underlying lymphoproliferative disorder.

Phenotypes of Thyroid Eye Disease.

PURPOSE: To describe a new classification system of thyroid eye disease (TED) based on the phenotypic features (clinical and radiologic) of the disease. METHODS: Clinical features, photographic, and orbital imaging of TED patients were considered in relation to their natural history and treatment response in the experience of the author. Phenotypically distinct categories of patients were identified and described. RESULTS: Six phenotypes of TED are observed: 1) congestive (active inflammatory), 2) "white eye" expansion, 3) "hydraulic" apex, 4) "white eye" apex, 5) cicatricial active, and 6) cicatricial passive. CONCLUSIONS: The observable characteristics of TED are determined by the underlying pathophysiology of the disease. TED is heterogeneous in its underlying pathogenesis, clinical manifestations, and response to medical and surgical treatment modalities. Several previous categorizations of the clinical appearance of TED exist, but they are dichotomous and underrepresent the heterogeneity of the disease. The authors present clinical and radiologic features of 6 different classes or phenotypes of TED and their response to different treatments.

Imaging Investigation of Thyroid Eye Disease.

INTRODUCTION: Thyroid eye disease (TED), is a term referring to the extrathyroidal manifestation of Grave's disease, a disorder which is currently the most common cause of hyperthyroidism and is characterised by underlying autoimmunity.The pathogenic course of the disease can be broadly classified into two stages, an early inflammatory and a late fibrotic stage. These stages are reflected in clinical severity and activity classifications, such as Clinical Activity Score and Class 0: No signs or symptoms, 1: Only signs, no symptoms (e. g. lid retraction), 2: Soft tissue involvement, 3: Proptosis, 4: Extraocular muscle involvement, 5: Corneal involvement, 6: Sight loss (NOSPECS). Classifications based on the latter, have important implications in treatment decisions since patients in the early active stage of the disease are more likely to respond to anti-inflammatory and immunosuppressive therapies, whereas patients in the late fibrotic stage require different therapeutic approaches, including rehabilitative surgery. METHODS: We reviewed cases of TED investigated with CT and Magnetic Resonance Imaging (MRI) in our department. We assessed the findings of imaging studies and their role in the clinical investigation of patients with TED as well as in the differential diagnosis from other disorders. RESULTS: Imaging has a significant role in the investigation of TED, however a consensus on the use of different imaging modalities in the course of disease has yet to be reached. Nevertheless, imaging and specifically CT and MRI can have a vital role in the initial diagnosis of clinically atypical presentation of TED, in surgical planning, as well as in the differential diagnosis from other orbital disorders. CONCLUSION: In this review, we attempt to present current trends in imaging investigation of TED. Rather than focusing on the findings of each imaging modality separately, we present the two main imaging modalities focusing on CT and MRI, in the context of pathogenic stages of the disease.

Establishing the usefulness of the GO-QOL in a UK hospital-treated population with thyroid eye disease in the CIRTED trial.

Thyroid eye disease (TED) is a potentially sight-threatening and cosmetically disfiguring condition arising in 25-50% of patients with Graves' hyperthyroidism. CIRTED is the first study to evaluate the long-term role of radiotherapy and prolonged immunosuppression with azathioprine in treating TED, one aim of which was to validate the use of the English version of GO-QOL in an UK population with TED. In a three stage design over a 48 week period, the GO-QOL was tested and compared to a general measure of quality of life (WHOQOL-Bref). In stage 1 utilising a standard 14 day test-retest design both GO-QOL subscales achieved Cronbach's alphas demonstrating excellent validity and internal reliability (Visual Function 0.929 and 0.931; Appearance 0.888 and 0.906). In stage 2, Repeated Measures ANOVA demonstrated longitudinal validity, with both subscales of the GO-QOL showing significant change over time (Visual Function, η2 = 0.114, p < .001; Appearance, η2 = 0.069, p < .002). In stage 3 the GO-QOL showed discriminant validity at the week 48 time point, with the visual function subscale being able to detect changes in groups identified by clinicians (using BCCOM ratings of improvement or deterioration), while both subscales could detect group differences when based on participants' subjective ratings of TED noticeability and severity. The results of this project provide support for the English translation of the GO-QOL as an outcome measure for patients with moderately severe active Graves' orbitopathy/TED.

Axial Globe Position Measurement: A Prospective Multicenter Study by the International Thyroid Eye Disease Society.

PURPOSE: Identify a reproducible measure of axial globe position (AGP) for multicenter studies on patients with thyroid eye disease (TED). METHODS: This is a prospective, international, multicenter, observational study in which 3 types of AGP evaluation were examined: radiologic, clinical, and photographic. In this study, CT was the modality to which all other methods were compared. CT AGP was measured from an orthogonal line between the anterior lateral orbital rims to the cornea. All CT measurements were made at a single institution by 3 individual clinicians. Clinical evaluation was performed with exophthalmometry. Three clinicians from each clinical site assessed AGP with 3 different exophthalmometers and horizontal palpebral width using a ruler. Each physician made 3 separate measurements with each type of exophthalmometer not in succession. All photographic measurements were made at a single institution. AGP was measured from lateral photographs in which a standard marker was placed at the anterior lateral orbital rim. Horizontal and vertical palpebral fissure were measured from frontal photographs. Three trained readers measured 3 separate times not in succession. Exophthalmometry and photography method validity was assessed by agreement with CT (mean differences calculation, intraclass correlation coefficients [ICCs], Bland-Altman figures). Correlation between palpebral fissure and CT AGP was assessed with Pearson correlation. Intraclinician and interclinician reliability was evaluated using ICCs. RESULTS: Sixty-eight patients from 7 centers participated. CT mean AGP was 21.37 mm (15.96-28.90 mm) right and 21.22 mm (15.87-28.70 mm) left (ICC 0.996 and 0.995). Exophthalmometry AGP fell between 18 mm and 25 mm. Intraclinician agreement across exophthalmometers was ideal (ICC 0.948-0.983). Agreement between clinicians was greater than 0.85 for all upright exophthalmometry measurements. Photographic mean AGP was 20.47 mm (10.92-30.88 mm) right and 20.30 mm (8.61-28.72 mm) left. Intrareader and interreader agreement was ideal (ICC 0.991-0.989). All exophthalmometers' mean differences from CT ranged between -0.06 mm (±1.36 mm) and 0.54 mm (±1.61 mm); 95% confidence interval fell within 1 mm. Magnitude of AGP did not affect exophthalmometry validity. Oculus best estimated CT AGP but differences from other exophthalmometers were not clinically meaningful in upright measurements. Photographic AGP (right ICC = 0.575, left ICC = 0.355) and palpebral fissure do not agree with CT. CONCLUSIONS: Upright clinical exophthalmometry accurately estimates CT AGP in TED. AGP measurement was reliably reproduced by the same clinician and between clinicians at multiple institutions using the protocol in this study. These findings allow reliable measurement of AGP that will be of considerable value in future outcome studies.

Management of patients with Graves' orbitopathy: initial assessment, management outside specialised centres and referral pathways.

Graves' orbitopathy (GO) is uncommon, but responsible for considerable morbidity. A coordinated approach between healthcare professionals is required in order to meet the needs of patients. Early diagnosis can be achieved by a simple clinical assessment. Low-cost effective interventions can be initiated by generalists, which may improve outcomes. Moderate-to-severe GO should be referred to specialised centres. Recommendations for clinical diagnosis, initial management and referral pathways are highlighted.

Robotic assisted orbital surgery for resection of advanced periocular tumours - a case series report on the feasibility, safety and outcome.

PURPOSE: Orbital surgery benefits from well-designed instrumentation that offers gentle tissue manipulation, high manoeuvrability and control. Nevertheless, in confined spaces, tissue manipulation must be accomplished with exceptionally high accuracy and precision. This is where robotic surgery offers an advantage. We aimed to evaluate a robotic-assisted surgical system's feasibility, safety and outcome in assisting tumour clearance. PATIENTS AND METHODS: A case series of patients with advanced periocular tumours undergoing robotic-assisted globe-sparing resection was performed using the DaVinci XI system (Intuitive Surgical, Inc). Institutional ethics and multidisciplinary approval were sought in all cases. RESULTS: Four patients with advanced periocular tumours underwent robotic-assisted orbital surgery at a mean age of 63 years (range 42-86). Two patients were diagnosed with squamous cell carcinoma, and two had basal cell carcinoma. One patient was found to have positive lymph nodes at the time of surgery and underwent simultaneous parotidectomy and lymph node clearance. Clear resection of the primary tumour was achieved in all patients; three patients underwent further resection due to narrow margins prior to reconstruction. Patients were follow-up for at least one year, and three remained disease-free. One patient with pre-existing extra-orbital disease developed metastatic disease four months post-op. All patients preserved vision peri-operatively, with no complaints of diplopia. Moderate ocular surface disease was noted in two patients. CONCLUSION: Our series highlights the potential advantage of three-dimensional optics, multi-directional instrumentation and motion scaling technology to achieve globe-sparing tumour resection in advanced periocular tumours. However, further robotic instrumentation development is required for orbital surgery.

Supraorbital notch and foramen: positional variation and relevance to direct brow lift.

PURPOSE: Forehead paresthesia after brow lift is well-documented with rates as high as 40.7%. The authors describe an anatomical study to identify the variation in position of the supraorbital notch/foramen to define safe limits for deep dissection during this procedure. METHODS: Sixty-six orbits from 23 dry skulls and 9 formalin-fixed cadavers were analyzed photographically using ImageJ software. The cadaveric specimens were dissected using a coronal incision, which allowed the inferior resection of the frontalis muscle and periosteum. The exit point of the supraorbital neurovascular bundle was noted as a foramen or notch. The position of the supraorbital notch or foramen was recorded in relation to the midline as defined by the sagittal suture at the level of the highest point of the supraorbital rim. The distance and angle for each foramen/notch were calculated. RESULTS: Thirty-three percent of orbits had a foramen. The average distance from the midpoint to the foramen was 25.24 mm (standard deviation 3.78 mm) and to the notch was 22.69 mm (22.69 mm). The range of distance between the midpoint and the foramen/notch was 17.62 to 32.35 mm. The average angle between the horizontal meridian and the foramen was 81/57° (standard deviation 4.69°). CONCLUSIONS: A wide variation in anatomy was seen. Greater caution is required when performing deep dissection around the supraorbital notch because of the variation in position of the supraorbital foramen.

Blood-stained tears-a red flag for malignancy?

BACKGROUND: Blood-stained tears can indicate occult malignancy of the lacrimal drainage apparatus. This study reviews data on patients presenting with blood in their tears and the underlying cause for this rare symptom. METHODS: Patients presenting with blood in their tears, identified over a 20-year period, were retrospectively collected from a single tertiary ophthalmic hospital's database and analysed. RESULTS: 51 patients were identified, the majority female (58%) with a mean age of 55 years. Most cases were unilateral (96%) with blood originating from the nasolacrimal drainage system in 53%. The most common diagnosis for blood-stained tears was a lacrimal sac mucocele (n = 16) followed by a conjunctival vascular lesion (n = 4). Three patients had systemic haematological disorders. The rate of malignancy was 8% (n = 4), with 2 patients having lacrimal sac transitional cell carcinomas, one with a lacrimal sac plasmacytoma and the other with chronic lymphocytic leukaemia and bilateral orbital infiltration (with bilateral bloody tears). One patient had a lacrimal sac inverted papilloma, a premalignant lesion. Four patients had benign papillomas (of the lacrimal sac, conjunctiva and caruncle). CONCLUSION: Haemolacria was a red flag for malignancy in 8% of patients (and tumours in 18% of patients). A thorough clinical examination including lid eversion identified a conjunctival, caruncle, eyelid or canalicular cause in 27% of cases.

Introducing the 'Benign Eyelid Lesion Pathway': 1 year experience of synchronous tele-oculoplastics in a tertiary hospital.

BACKGROUND: Patients with benign eyelid lesions make up a large proportion of referrals to the oculoplastic service and lend themselves well to telemedicine with assessments heavily reliant on history, observation-based examination and photographs to enable management decision-making. Our tertiary unit set up tele-oculoplastics clinics for all new patients referred for benign eyelid lesions comprising tele-consultation with antecedent patient photograph: Benign Eyelid Lesion Pathway (BELP). One year on, we describe a retrospective analysis of 974 patients looking at distinct parameters of effectiveness. METHODS: We retrospectively collected data from electronic patient records (EPR) for BELP patients from July 2020 to August 2021 (n = 974). We analysed time efficiency (referral time to treatment plan, consultation duration in minutes, average waiting times, number of patients seen per clinician and DNA rate), accessibility, safety (via video surveillance clinic) and theatre utilisation. RESULTS: 57.3% (n = 558) were listed for a surgical procedure direct from tele-consultation with 94.9% (n = 513) of these proceeding to surgery; 22.8% (n = 222) were discharged, 10.7% (n = 104) had further video follow-up and 6.7% (n = 65) required face-to-face follow-up. Our results showed efficient referral-to-treatment times, waiting times, consultation times and non-attendance rate. There was only a 2.57% non-attendance rate. There was no missed diagnosis of a malignancy of a presumed benign lesion. CONCLUSION: Tele-oculoplastics provides a streamlined, safe, effective, and logistically convenient way to review benign eyelid lesions. With the increased waiting times for referral to biopsy of eyelid lesions, this clinic shows it is imperative to provide digital accessibility for patient assessment and booking to operating theatre.

Factors Predicting Long-term Outcome and the Need for Surgery in Graves Orbitopathy: Extended Follow-up From the CIRTED Trial.

Graves orbitopathy is both disabling and disfiguring. Medical therapies to reduce inflammation are widely used, but there is limited trial data beyond 18 months of follow-up. METHODS: Three-year follow-up of a subset of the CIRTED trial (N = 68), which randomized patients to receive high-dose oral steroid with azathioprine/placebo and radiotherapy/sham radiotherapy. RESULTS: Data were available at 3 years from 68 of 126 randomized subjects (54%). No additional benefit was seen at 3 years for patients randomized to azathioprine or radiotherapy with regard to a binary clinical composite outcome measure (BCCOM), modified European Group on Graves' Orbitopathy score, or Ophthalmopathy Index.Clinical Activity Score (CAS), Ophthalmopathy Index, and Total Eye Score improved over 3 years (P < .001). However, quality of life at 3 years remained poor. Of 64 individuals with available surgical outcome data, 24 of 64 (37.5%) required surgical intervention. Disease duration of greater than 6 months before treatment was associated with increased need for surgery [odds ratio (OR) 16.8; 95% CI 2.95, 95.0; P = .001]. Higher baseline levels of CAS, Ophthalmopathy Index, and Total Eye Score but not early improvement in CAS were associated with increased requirement for surgery. CONCLUSION: In this long-term follow-up from a clinical trial, 3-year outcomes remained suboptimal with ongoing poor quality of life and high numbers requiring surgery. Importantly, reduction in CAS in the first year, a commonly used surrogate outcome measure, was not associated with improved long-term outcomes.

Reliability of estimating ductions in thyroid eye disease: an International Thyroid Eye Disease Society multicenter study.

PURPOSE: To determine intraobserver and interobserver reliability of 3 clinical techniques for measuring ocular ductions in patients with thyroid eye disease and to compare these with an established method using a Goldmann perimeter. Our secondary goals were to compare the clinical methods for test duration, ease of learning and performance, and whether these differed between novices and experts. DESIGN: Multicenter, prospective, comparative trial. PARTICIPANTS: We recruited 38 patients with thyroid orbitopathy and reduced ocular motility from 7 academic centers. METHODS: At each center, 2 novices and 2 experts measured the ocular ductions of each eye of each patient in 4 directions (0°, 90°, 180°, and 270°) using 3 techniques (best guess [BG], light reflex [LR], and a ruler measuring [RU] technique). Test duration and clinicians' feedback were recorded. A subjective and objective measurement for ocular ductions using a Goldmann perimeter was performed for each subject by a trained technician. The 3 clinical measurements and the perimetry measurements were performed twice, separated by ≥1 hour. MAIN OUTCOME MEASURES: We measured the intraobserver and interobserver reliability of the 3 clinical techniques and intraobserver reliability of Goldmann perimeter. Clinical testing reliability was compared between experts and novices. We also examined test duration and clinician feedback. RESULTS: The LR technique had significantly better intraobserver and interobserver repeatability compared with the BG or RU clinical measurements and statistically was equivalent to the gold-standard perimetric technique. Reliability was constant regardless of the amount of restriction in ocular movement. There was no difference between reliability values for experts and novices. The LR and BG techniques were significantly faster than the RU or perimetry techniques and were considered easiest to learn and perform, but clinicians had most confidence in the LR technique results. CONCLUSIONS: The LR technique for measuring ocular ductions in thyroid orbitopathy is more reliable than other clinical techniques and as reliable as the established technique using the perimeter. However, unlike the latter method, it is easier to learn and perform by both novices and experts, is significantly faster, and can be performed by the clinician without machinery or a trained technician.

Lessons from the past: cribra orbitalia, an orbital roof pathology.

AIMS: To define a computed tomography protocol that may be used in future clinical practice for the reliable detection and analysis of cribra orbitalia. MATERIALS AND METHODS: Two osteological assemblages from the Museum of London were used to select 13 cribratous skulls and 5 non-cribratous skulls. Area of cribra orbitalia was measured using image analysis. Morphology of cribra orbitalia, orbital roof density and the associated optic canal diameter was analysed using computed tomography reconstructions. RESULTS: The presence of cribra orbitalia was associated with changes in the internal diploë layer as well as the cortical bone table. A novel radiological grading system and protocol was developed to identify the pathology. A decrease in the orbital roof density by 210 Hounsfield units and a reduction in the optic canal diameter, up to 1 mm, were found to be associated with the presence of cribra orbitalia. CONCLUSIONS: The occurrence of cribra orbitalia is found to be associated with stenosis of the optic canal, and could explain a proportion of cases ofoptic nerve entrapment. This study provides a guideline for radiologists and oculoplastic surgeons to help detect the presence of cribra orbitalia in suspected patients.

A cadaveric study of the morphometric relationships and bony composition of the caucasian nasolacrimal fossa.

AIMS: To describe the morphometric relationships and bony composition of the nasolacrimal fossa in a Caucasian population with particular reference to the lacrimo-maxillary suture (LMS). METHODS: Forty-seven orbits from 24 formalin fixed cadavers were exenterated. Morphometric measurements were taken between anatomical landmarks forming the lacrimal fossa on the medial orbital wall. RESULTS: The mean recorded distance from the anterior lacrimal crest (ALC) to the posterior lacrimal crest (PLC) and the LMS were 8.8 mm (± 1.6) and 4.3 mm (± 1.1), respectively. In 25.5% of the orbits the LMS was at the mid-vertical line (MVL), defined as a line equidistant from the ALC and PLC. In 42.5% the LMS was located anterior to the MVL toward the ALC. In 66% of the orbits the LMS was at or within one standard deviation (SD) of the MVL. The LMS was >1 SD away from the MVL toward the ALC and PLC in 19% and 15% of orbits, respectively. CONCLUSIONS: In a quarter of the orbits in our Caucasian population the nasolacrimal fossa was formed equally by the maxillary and lacrimal bones. However, in nearly a third of the cases the LMS was located closer to the PLC, indicating predominance of the thicker maxillary bone. This may result in greater difficulty in initiating the surgical osteotomy when performing a dacryocystorhinostomy. These data contribute to our understanding of the variation in lacrimal fossa anatomy and encourage further studies in different racial groups.

The Effect of Ophthalmic Surgery for Graves' Orbitopathy on Quality of Life: A Systematic Review and Meta-Analysis.

Background: Graves' orbitopathy (GO) has a profound negative impact on quality of life. Surgery is undertaken to preserve vision, correct diplopia, and improve aesthetics. We sought to quantify the effect of different surgical approaches on quality of life. Methods: Electronic databases Ovid-MEDLINE and EMBASE were used from inception until March 22, 2021, to identify studies assessing quality of life pre- and postsurgical intervention for GO. Two reviewers independently extracted data and performed quality assessments. Random-effects and Bayesian models for meta-analyses were utilized. Results: Ten articles comprising 632 patients with a mean age of 48.4 years (range 16-85 years) were included. All used the Graves' Ophthalmopathy Quality of Life (GO-QOL) questionnaire. For GO-QOL appearance, the pooled standardized mean improvement for patients after surgery was +0.72 (95% confidence interval [CI 0.50-0.94]), I2 = 69% [CI 52-80%]. For GO-QOL visual functioning, the pooled standardized mean difference (SMD) for patients after surgery was +0.41 [CI 0.25-0.58], I2 = 60% [CI 36-74%]. For visual appearance, orbital decompression yielded the greatest improvement (SMD +0.84 [CI 0.54-1.13]) followed by eyelid surgery (SMD +0.38 [CI 0.05-0.70]), while strabismus correction had no significant effect (SMD +0.94 [CI -0.10 to 1.99]). Conversely strabismus correction was associated with the greatest improvement (SMD +1.25 [CI 0.29-2.21]) in visual functioning, outperforming orbital decompression (SMD +0.29 [CI 0.15-0.43]) and eyelid surgery (SMD +0.12 [CI -0.18 to 0.41]). A mean improvement in GO-QOL of greater than 10 points after orbital decompression surgery was achieved in 12/14 (86%) patient groups for appearance and 5/14 (36%) patient groups for visual functioning. A mean improvement of greater than 6 points was achieved in 5 of 6 (83%) patient groups for strabismus surgery for both appearance and visual functioning. A mean improvement of greater than 6 points after eyelid surgery was achieved in 2/3 (67%) patient groups and 0/3 patient groups for visual appearance and functioning, respectively. Conclusion: Ophthalmic surgery results in substantial improvements in quality of life in patients with GO, with greater perceived effects on appearance than visual function. Orbital decompression has particular impact on visual appearance; strabismus surgery may benefit both visual appearance and function equally, whereas eyelid surgery benefits appearance alone.

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.

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.