Photometric oculometry. II. Measurement of axial ocular distances with slit-lamp microscopy. Clinical evaluation, and comparison with ultrasonography.

Photometric oculometry is a slit-lamp technique, which makes possible an estimation of intraocular axial distances and axial length. The technique is based on a transformation of a sagittal slit-lamp movement into intraocular axial distances when the slit-lamp focal plane is moved in the optical axis from retina to cornea. Determination of the axial length in 50 eyes (refractive range +4.75 to -5.25 D) showed that the axial length varied from 21.9 mm in hypermetropic eyes to 26.0 mm in myopic eyes, with the emmetropic eyes being approximately 24 mm. A comparison of intraocular axial distances determined by photometric oculometry and by ultrasonography on a small series of eyes showed no significant differences between the axial length, the length of the vitreous body, and the lens thickness, whereas a significant difference between the anterior chamber depth was observed (photometry giving slightly larger values than ultrasound).