The use of a computer-assisted image-guided system (InstaTrak) in orbital surgery.

PURPOSE: To assess the usefulness of a computer-assisted image-guided system (CAIGS) as an intraoperative anatomical guide in performing orbital surgery. METHODS: Noncomparative interventional case series of 30 consecutive orbital procedures performed by one surgeon (J.G.C.) using the CAIGS (InstaTrak) for intraoperative anatomical guidance. RESULTS: The series consisted of 8 cases of orbital decompression, 8 cases of orbital fracture, 11 cases of tumor excision, 2 cases of orbital reconstruction for severe enophthalmos, and 1 case of drainage of an orbital abscess. The CAIGS (InstaTrak) was useful in providing adjunctive intraoperative guidance in all 30 orbital cases. CONCLUSION: The CAIGS (InstaTrak) system is a useful adjunctive tool in providing intraoperative anatomic guidance in a consecutive series of varied orbital operations.

Therapeutic index of pilocarpine, carbachol, and timolol with nasolacrimal occlusion.

We assessed the effect of nasolacrimal occlusion on the therapeutic index of various antiglaucoma medications in healthy volunteers and patients with glaucoma. Nasolacrimal occlusion used with pilocarpine 2% every 12 hours gave the maximal ocular hypotensive response. Carbachol 1.5% every 12 hours with nasolacrimal occlusion gave the maximal response for this drug. For timolol, nasolacrimal occlusion collapsed the dose-response curve and extended the duration of action. A final trial of carbachol added to timolol with nasolacrimal occlusion showed that timolol 0.25% and carbachol 1.5% every 12 hours gave the maximal response for this combination. Our findings suggest that most of the commercially used ocular hypotensive agents can achieve the same maximal effect with lower concentrations and less frequent administration (never exceeding every 12 hours) than are currently recommended should nasolacrimal occlusion be performed. Furthermore, nasolacrimal occlusion should markedly decrease the systemic absorption of topical ocular drugs and lessen the chance of systemic side effects.

Therapeutic index of epinephrine and dipivefrin with nasolacrimal occlusion.

We assessed the effect of nasolacrimal occlusion on the therapeutic index of the adrenoreceptor agonists in healthy volunteers and patients with glaucoma. Nasolacrimal occlusion did not significantly alter the response to 2% epinephrine or to 0.1% dipivefrin in healthy subjects, suggesting that both 2% epinephrine and 0.1% dipivefrin are at the top of the dose-response curve. When 0.5% epinephrine with nasolacrimal occlusion was tested in patients with glaucoma, effects were noticeable at four and eight hours (P less than .05), but not at 12 hours. For 2% epinephrine, there was no significant difference at any measurement time. Epinephrine (1%) with and without nasolacrimal occlusion gave results similar to those of 2% epinephrine, suggesting that 1% epinephrine is also at the top of the dose-response curve. Nasolacrimal occlusion did not increase the ocular hypotensive effect of either of these concentrations. Because dipivefrin, the most widely used formulation in this class, is a prodrug of epinephrine that has a corneal penetration approximately 17 times that of epinephrine, 0.05% dipivefrin, every 12 hours, might be an adequate dosage for maximal effect. Although nasolacrimal occlusion did not alter the drug effect of 0.1% dipivefrin, preventing as much drug as possible from reaching the systemic circulation is desirable.

Sneezing as a cause of acute angle-closure glaucoma.

We report the case of a patient who had an attack of acute angle-closure glaucoma precipitated by sneezing, probably as a result of a sudden increase in venous back pressure. This young woman had a history of allergic sinusitis.

Effect of chronic carbonic anhydrase inhibitor therapy on bone mineral density in white women.

A limited, dual-photon absorptiometry, single-center study of bone mineral density (BMD) was conducted on white female glaucoma subjects who were chronic users of the carbonic anhydrase (CA) inhibitors acetazolamide (Az) or methazolamide (Mz). In postmenopausal subjects long-term (greater than 4 years) CA inhibitor use was associated with a bone-sparing effect as judged by spinal BMD in comparison to controls matched for age, sex, weight, and ethnic group or in comparison to a national normative data base. Short-term (0-2 years) postmenopausal CA inhibitor users and premenopausal subjects using CA inhibitors showed no sparing of spinal BMD. Femoral neck BMD was not affected by CA inhibitor therapy in any of the groups. This study supports a proposed role for carbonic anhydrase in human bone resorption and suggests a possible future utility for carbonic anhydrase inhibitors in prophylaxis or management of primary involutional osteoporosis. Future studies are necessary to verify and expand these findings, assess the effects of CA inhibitors on bone mechanical competence, and further develop CA inhibitors with some specificity for bone.

Automated perimetry, tonometry, and questionnaire in glaucoma screening.

To evaluate the sensitivity and specificity of various portions of the glaucoma screening process, 145 participants underwent complete ophthalmic examinations. A weighted questionnaire was 20% (2 patients) and 36% (5 suspects) sensitive for the glaucoma patients and glaucoma suspects, respectively. Tonometry alone was 20% (2 patients) and 7% (1 suspect) sensitive for glaucoma patients and glaucoma suspects, respectively. Automated perimetry of the central 30 degrees and nasal periphery identified nine (90%) of the glaucoma patients and five (36%) of the glaucoma suspects. The presence of increased intraocular pressure was not by itself very useful, but when perimetry or tonometry was used, 10 (100%) of the glaucoma group was identified. We recommend that automated suprathreshold perimetry and tonometry be performed in glaucoma screening.

Effect of intracameral carbachol on intraocular pressure after cataract extraction.

Thirty-two patients were randomly assigned to a treatment or a control group to determine the dose-response and duration of action of intracameral carbachol on immediate postoperative intraocular pressure after extracapsular cataract extraction using a viscoelastic substance. Patients in the treatment group received 0.5, 0.25, or 0.1 ml of 0.01% intracameral carbachol. Patients in the control group received 0.1 or 0.5 ml of balanced salt solution. Intraocular pressures of all patients were measured preoperatively and at three, six, 12, 24, and 48 hours postoperatively. The control group as a whole showed a 9.5-mm Hg intraocular pressure rise at three hours, a 10.0-mm Hg rise at six hours, a 9.0-mm Hg rise at 12 hours, and a 7.2-mm Hg rise at 24 hours postoperatively. The group treated with 0.5 ml of carbachol maintained stable intraocular pressures through the 48-hour measurement period. The groups treated with 0.25 and 0.1 ml of carbachol maintained stable intraocular pressures through 24 hours postoperatively. The differences in intraocular pressure were statistically significant for all treated groups through the 24-hour measurement.