Slit lamp biomicroscope

Slit lamp biomicroscope An instrument that allows for the microscopic examination of the cornea, anterior chamber lens, and posterior chamber. 

Examination of reactions can be facilitated by use of a binocular loupe hand slit-lamp, biomicroscope, or other suitable device. After recording the observations at 24 hours, the eyes of any or all rabbits may be further examined with the aid of a fluorescent lamp. The duration of the observation period should not be fixed rigidly but should be long enough to fully evaluate the reversibility or irreversibility of the effects observed. This period, however, need not exceed 21 days after instillation of the test chemical. 

An ABMD may be evident. Classic findings of ABMD include intraepithelial geographic opacities, microcysts, and concentric refractile lesions that resemble fingerprints. The use of retroillumination is helpful in viewing the epithelial defects with the slit-lamp biomicroscope. 

The effect of solutions of CN in PEG 300 on corneal thickness was investigated in vivo in the rabbit using solutions in the concentration range 0.01-0.75% with measurements being taken before instillation and at 1 and 24 h, and 2,4, 8 and 17 days post-treatment. Corneal thickness was measured by an optical pachymeter attached to a slit-lamp biomicroscope. Increases in corneal thickness were statistically significant for exposures to 0.03% CN and above, and both the magnitude and duration were related to the CN concentration. Times for comeal thickness to return to control values varied between 2 days for 0.02% and 14 days for 0.75%. 

When the corneal epithelium is breached by injury, the barrier to fluorescein penetration is lost, and it can diffuse into the underlying cornea stroma. Thus, detection of the presence of fluorescein staining is valuable for the detection of early comcal injury. This i.s facilitated by examination under ultraviolet light or by using a blue filter in a slit-lamp biomicroscope. 

A method was described by Burton et al. (1981) involving the direct application of irritant test substance to the cornea of eyes removed immediately after sacrifice of rabbits and subsequent evaluation of the cornea for swelling, opacity, and fluorescein staining, The eye is mounted on a clamp in a temperature-controlled superfusion chamber with isotonic saline dripped onto the surface of the cornea, After an equilibrium period of 30-45 min, the test material is applied to the surface of the cornea and then washed off. Eyes are inspected macroscopically. Then, with a slit-lamp biomicroscope, the comeal thickness is measured and any fluorescein staining noted. The predictive value of the method has been confirmed in several studies (Commission of the European Communities, 1991 Koeter and Prinsen, 1985 Price and Andrews, 1985 Whittle et al., 1992), By using comeal thickness measurement, fluorescein retention, and comeal opacity as criteria for ocular injury, the suitability of the chicken eye as an enucleated model was confirmed by Prinsen and Kocier (1993) and Prinsen (1996). 

As a part of the Federal Hazardous Substances Act (FHSA), a modified Draize test was adopted (96-98) as the official method for evaluation of acute ocular irritancy (99). It is a pass/fail determination that remains in effect today. The test may use a small volume more consistent with the capacity of the inferior conjunctival sac (100), and incorporate biomicroscopic slit-lamp examination and/or fluorescein staining to assess ocular changes (71,97,98). While various in vitro tests have been proposed to replace this in vivo evaluation and a U.S. interagency committee has recommended certain in vitro tests to detect severe irritants and corrosives, none has yet been officially accepted or validated (101-104). 

Slit Lamp Examination. Also known as biomicroscopy, a slit lamp examination allows the optometrist to closely inspect the anatomical structures of the eye. If a biomicroscope is used, the optometrist can obtain a magnified and detailed view of the eye. The slit lamp is an instrument that can focus an intense, thin sheet of light into the eye. During this examination, the patient is asked to place his or her chin and forehead against a support or to keep his or her head and eyes steady. 

---