New developments in selected cysts of the jaws.

The number and variety of cysts that occur in the jaws are greater than those in any other part of the body. Consequently, dental practitioners must keep up with advances in this field, including the definition of new entities, such as the glandular odontogenic cyst; the deletion of the old incorrect concept of maxillofacial fissural cysts, including the globulo-maxillary cyst; and the advances in the molecular biology of established cysts, such as the dentigerous cyst and the odontogenic keratocyst.

Observation of the retina using the tandem scanning confocal microscope.

A tandem scanning confocal microscope (TSCM) is currently being used to obtain high-resolution images of the human cornea in vivo. Advantages of confocal microscopy for in vivo imaging include optical sectioning and increased contrast through removal of scattered light. We have adapted to TSCM to view the retina in vivo by constructing an applanating lens and fitting the microscope with an imaging-intensifying camera of increased sensitivity. The microscope uses a spinning disc with 40,000 holes, each of 30 microns diameter, and a 100 W mercury arc lamp light source with a 455 nm long pass filter. The applanating lens is composed of three elements, two of which are movable for focusing. Images of a rabbit retina were obtained in vivo revealing the nerve fiber layer and blood vessels around the optic disc. The power density at the retina was calculated to be 3 mW/cm2, which is well below the power levels of a direct or indirect ophthalmoscope. Magnification of the retinal image was approximately 60 x and a 1 mm wide area of retina was in view. This prototype TSCM system demonstrates that images of a retina in vivo are obtainable with confocal microscopy and that the sharpness is comparable to standard fundus camera photography. Further modifications to improve the light level and alterations in the design of the objective should improve the quality of the images obtained and achieve the enhanced resolution of which, in theory, the confocal microscope is capable.

Tear flow and evaporation in patients with and without dry eye.

PURPOSE: To evaluate the steady-state tear flow and evaporation from the ocular surface of patients with and without dry eye. METHODS: Two groups of patients, 21 with dry eye and 34 without dry eye, with similar age distributions were selected by criteria based on tear osmolarity, Schirmer test, meibomian gland loss, and dry eye symptoms and were compared for tear flow, tear volume, percent turnover, and surface evaporation. RESULTS: Tear flow averaged 0.10 +/- 0.08 microliters/minute in patients with dry eye versus 0.15 +/- 0.12 microliters/minute in patients without dry eye (P = 0.002). Tear volume averaged 2.13+/- 1.3 microliters in patients with dry eye versus 2.23 +/- 2.5 microliters in patients without dry eye (P = not significant) and tear turnover averaged 5.3 +/- 2.9% in patients with dry eye versus 8.2 +/- 4.3% in patients without dry eye (P = 0.019). Evaporation averaged 25 +/- 35 X 10(-7) g/cm(2)/second in patients with dry eye versus 13 +/- 6 X 10(-7) g/cm(2)/second in patients without dry eye (P = 0.003). CONCLUSIONS: Measured tear flow was significantly lower than previously determined in patients with and without dry eye. Evaporation was increased in patients with dry eye and accounted for the majority of the tear loss in patients with dry eye. Normal tear osmolarity can be maintained, even with low tear flow, if evaporation is kept within the normal range.

A study of aqueous humor dynamics in keratoconus.

Clinical observations suggest that patients with keratoconus have lower intraocular pressures, on average, than normal subjects. Our purpose was to determine whether differences in aqueous production and outflow facility could account for differences in intraocular pressure between a group of patients with keratoconus and a group of normal, age-matched control subjects. Aqueous humor dynamics were determined by the use of fluorophotometry in one eye of seven patients with keratoconus and ten age-matched normal subjects. Intraocular pressure was measured by applanation tonometry. Keratoconus patients had a statistically significant lower mean intraocular pressure than normal control subjects (11.3 +/- 1.6 mmHg vs. 16.6 +/- 2.8 mmHg, P = 0.0004). The difference in mean intraocular pressure remained significant even after correcting for possible errors in applanation tonometry due to thin corneal stroma. There was no difference in mean aqueous humor flow rates in the keratoconus patients as compared to controls (2.29 +/- 0.53 microliter min-1, P = 0.73). The mean apparent outflow facility was 0.21 +/- 0.07 microliter min-1 mmHg-1 for keratoconus patients compared to 0.14 +/- 0.03 microliter min-1 for controls (P = 0.02). Lower mean intraocular pressure in keratoconus patients appears to be due to increased outflow facility as compared to normal subjects.

Diagnosis of Acanthamoeba keratitis in vivo with confocal microscopy.

We present eight cases of Acanthamoeba keratitis. In each case; the Acanthamoeba organisms were visualized in the epithelium and anterior stroma using tandem scanning confocal microscopy. The organisms were highly reflective, ovoid, and were 10-25 microns in diameter. The Acanthamoeba organisms in the human corneas were identical in size and shape to Acanthamoeba organisms on an agar plate visualized with the same confocal microscope. Confocal microscopy is a useful method for identifying Acanthamoeba organisms in vivo within the corneal epithelium and anterior stroma.

In vivo observation of the human tear film by tandem scanning confocal microscopy.

A new method for observing normal and pathologic states of the human tear film using tandem scanning confocal microscopy is presented. The confocal microscope is configured with a horizontal light path, a 10 x dry objective, and an image-intensified camera for collecting images at a magnification of approximately 150x. The advantages of confocal microscopy can be used to collect reflected images of the human tear film with improved detail and resolution.

Osteonecrosis in patients treated with definitive radiotherapy for squamous cell carcinomas of the oral cavity and naso-and oropharynx.

A group of 381 patients with squamous cell carcinoma of the oral cavity and naso-and oropharynx treated with definitive radiotherapy were analyzed with respect to the incidence and precipitating factors of mandibular osteonecrosis. Elective dental extraction prior to therapy increased the incidence, and dental conservation decreased it. Spontaneous osteonecrosis did not occur with doses less than 6,000 rads in 6 weeks, and was uncommon (1.8%) at doses under 7,000 rads in 7 weeks. At doses over 7,000 rads, osteonecrosis developed in 9%. The incidence was greater in patients with tumors near bone (9.4%) than in those with tumors not next to bone (2.1%).