[The VK-vitrektom. A vitrectomy machine for the anterior segment surgeon (author's transl)]

The VK-Vitrektom was specially devised to suit the needs of the anterior segment surgeon. Depsite its relatively low price this non-disposable instrument fulfills high demands upon durability and cutting performance. When stored under sterile conditions, it is usable any time within a few moments.

Total hyphema evacuation by vitrectomy instrumentation

We describe our technique for the surgical removal of hyphema using the Ocutome vitrectomy system and report the results in 12 patients. Blood was removed successfully with just one operation in all 12 eyes. Eleven of the 12 eyes maintained intraocular tension of less than 20 mm Hg. Vision improved in 11 of 12 eyes and six had a vision of 6/18 or better. Permanent vision loss could not be attributed to the operative technique.

Radial keratotomy: an analysis of the American experience

A total of 223 patients with bilateral nonprogressive myopia ranging from - to - 11 D underwent partial-thickness radial keratotomy (400 eyes). Topical anesthesia was used for all surgery and all patients had 16 radial incisions from a preset central optical zone, determined by table and/or formula. Neither corneal diameter or scleral rigidity was taken into account in these groups. Substantial reduction of myopia resulted immediately in all cases, with Group 1 showing a 44% regression of the myopia with stabilization occurring at three months. Group 2 showed a 14% regression of effect. In Group 1, 28% attained an unaided visual acuity (postoperatively) of 20/40 or better for most of the day, while 61% of Group 2 attained the same result. Night glare was present in both groups, usually subsiding in three months. Fluctuation was reported in both groups. Side effects were mild. The comparison of the two groups shows that incisions carried almost to Descemet's membrane and deepened in the periphery resulted in much greater reduction of the myopia and a more permanent and stable effect following surgery. New methods of measuring corneal curvature are necessary and a more satisfactory blade needs to be developed for surgery. Corneal thickness measurements have been made more accurate by the development of the ultrasonic pachymeter.

Corneal topography. Corneascope

We present an introduction to a clinical quantitative corneascope for measurement of corneal topography in detail. This instrument provides contour keratometry in all corneal meridians. We review the normal myopic and hyperopic eye contours, keratoconus, pellucid marginal degeneration, and wound gape and compression related to cataract surgery. We present a modified Placido disk for office use that incorporates the unique incident light image of the corneascope for rapid review of irregular corneal contours. Corneal topography irregularities frequently contribute to devastating refractive states of the eye and should be examined carefully when keratorefractive surgery is considered.

A simplified approach to the management of tangential retinal traction bands

Images

Comparison of endothelial evaluation techniques

Comparative evaluation of the corneal endothelium with the Heyer-Schulte specular photomicroscope, the McIntyre CEB reticle affixed to a slitlamp, and a slitlamp alone found the reticle-slitlamp combination to give results within a 10% average of endothelial cell counts determined with the specular microscope. The reticle also compared favorably in time and cost savings. All three methods of corneal evaluation were effective for observation of polymegathism. Because of its lower magnification, the slitlamp without the reticle was best suited for evaluation of cornea guttata.

Extraocular muscle forces in normal human subjects

Actively developed horizontal muscle forces and tissue stiffnesses were measured in 29 normal orthophoric volunteer subjects (18 to 33 years old) by means of noninvasive length-tension forceps. Mean active fixation force developed at 50 deg extreme gaze was 26% greater for the medial rectus (74.8 gm) than for the lateral rectus (59.1 gm). The variation of maximum active force among individuals was 2:1 (48 to 103 gm). These muscles developed up to 25% of their maximum active force out of their field of action. Active (counter) hysteresis force differences of over 10 gm were measured between nasal and temporal gaze directions. This study suggests that a muscle which develops a maximum active force of less than 45 gm would be suspect as paretic. Variations from the normal pattern of reciprocal innervation, reflected in the graded active force of individual muscle contraction, may help in understanding some types of oculomotor pathology. The mean tissue stiffness-restraining movement of the globe in the nasal direction (1.05 gm/deg) is 11% greater than in the temporal direction (0.94 gm/deg). This is consistent with a stronger medial rectus balanced by a greater load. Variation of stiffness of 2:1 was observed among individuals; 0.8 to 1.7 gm/deg pulling nasally and 0.77 to 1.2 gm/deg temporally. Passive hysteresis and viscous force differences of over 10 gm were observed between the passive forced pull and normal spring-return of the eye. Large stiffnesses may be normal if balanced by large active forces. Abrupt changes of the length-tension curve indicate the magnitude and location of restrictions.

Ophthalmometry without patient fixation

Because of the asphericity of the cornea, proper ophthalmometry requires the visual axis of the eye, the optical axis of the ophthalmometer, and the corneal apex to be coincident. The animal subject and the human patient cannot always direct their visual axis to the axis of the instrument. This paper describes the attachment of a photographer's tripod pan arm to the Haag Streit ophthalmometer and the method devised, which allows accurate corneal curvature measurement in cases of nonfixating subjects.