A virtual reality surgery simulation of cutting and retraction in neurosurgery with force-feedback

A virtual-reality surgical simulator aimed at neurosurgery is presented. The simulator utilises boundary element (BE) technology to develop real-time realistic deformable models of the brain. The simulator incorporates the simulation of surgical prodding, pulling and cutting. Advanced features include the separation the cut surfaces by retractors and post-cutting deformations. The experience of virtual surgery is enhanced by implementing 3D stereo-vision and the use of two hand-held force-feedback devices.

Orbital dermoid cysts showing conjunctival epithelium

The orbital area is one of the most common sites for dermoid cysts. Most often these cysts are lined by keratinizing squamous epithelium; however, dermoid cysts may rarely be lined with conjunctival epithelium. We describe such a cyst and the features that distinguish it from other dermoid cysts.

Effect of blinking on tear elimination as evaluated by dacryoscintigraphy

To document the change in drainage of tears that occurs with blinking, the authors evaluated 17 lacrimal systems of 12 individuals with dacryoscintigraphy. A significant difference in tear drainage was found by keeping the eyelids closed during the first 2 minutes after drop placement (P less than 0.03), but not from 2 to 5 minutes (P greater than 0.4). Retardation of tear drainage after droplet placement can be achieved by simple eyelid closure for 2 minutes.

Benign mixed tumors arising in the palpebral lobe of the lacrimal gland

The accurate clinical diagnosis of benign mixed tumors of the lacrimal gland is imperative for proper therapeutic management. Although benign mixed tumors of the orbital portion of the lacrimal gland have an established identity, those tumors arising in the palpebral lobe are unusual. Four patients with benign mixed tumors of the palpebral lobe are presented, emphasizing the confusion that exists in making the diagnosis. Palpebral lobe benign mixed tumors should be strongly considered in the differential diagnosis of upper outer eyelid masses. En bloc resection avoids the risk of tumor spillage, recurrence, and/or malignant transformation caused by preliminary biopsy or incomplete resection.

Orbital invasion by malignant eyelid tumors

An important factor in the preoperative evaluation of patients with invasive periorbital carcinomas is the presence or absence of orbital bone involvement. A retrospective study was performed to evaluate the reliability of computed tomography (CT) in detecting orbital bone invasion. Eleven patients with extensive facial-orbital basal cell or squamous cell carcinomas were evaluated preoperatively by CT and the results were compared with the clinical findings and postoperative histopathologic examination confirmed bone and/or periosteal invasion, CT was positive in three (43%). Based on these findings, we strongly recommend that CT not be relied upon in excluding orbital bone involvement. Bony invasion may be histologically present, even though destruction is not seen on CT scans. Therefore, a normal CT scan should not deter one from removing clinically abnormal bone or periosteum and submitting it for histologic examination.

Relative canalicular tear flow as assessed by dacryoscintigraphy

Studies evaluating the relative importance of the upper and lower canaliculi in tear drainage have been many and varied, and at times the application of the data to clinical situations is difficult. In order to evaluate the relative tear flow in the upper and lower canaliculi and to quantitatively evaluate the different tear flow rates by a physiologic method, we have studied 11 patients using partial canalicular obstructions and dacryoscintigraphy. The authors found no statistical difference in tear flow between the upper and lower canalicular systems. This information has clinical application when deciding whether to repair an isolated canalicular injury.

Eosinophilic granuloma of the orbit with spontaneous healing

A 13-year-old boy presented with a 2-month history of swelling of the right upper eyelid and displacement of the right eye. Computed tomography (CT) showed a tumor in the right orbit and a large osteolytic defect of the orbital frontal bone. At surgery a yellowish-tan mass was found replacing the orbital roof and abutting the dura. Incisional biopsy established the diagnosis of eosinophilic granuloma. In the absence of further therapy, the mass resolved, and the bony defect completely reossified within 14 months. During more than 2 years of follow-up, there has been no evidence of local recurrence or systemic disease. This case demonstrates that eosinophilic granuloma may resolve spontaneously with healing of bony defects, thus eliminating the need for adjunctive resection or radiation therapy in selected patients.

Eyelid necrosis following intralesional corticosteroid injection for capillary hemangioma

The intralesional injection of corticosteroids has been employed successfully in treatment of adnexal neonatal hemangiomas since 1979. This form of treatment is easily administered, is repeatable and free from serious complications. We present an exceptional case in which full-thickness eyelid necrosis ensued following intralesional injection of corticosteroids in a capillary hemangioma. After eyelid reconstruction the patient's visual axis has remained unobstructed, and amblyopia has been thus far averted.

Subconjunctival orbital fat prolapse

Subconjunctival orbital fat prolapse is a benign entity in which fat herniates through Tenon's capsule. It is often confused with other lesions such as lacrimal gland tumors, lymphoid tumors and lipodermoids. The clinical and computed tomographic findings in a series of 15 patients are presented, and the features that are helpful in the differential diagnosis are discussed.