ABSTRACT
Double-exposure holograms are taken of the patient's cornea after a heartbeat. The resulting stress test, or holographic interferogram, shows sharply demarcated fringe patterns outlining structurally weak areas in the cornea. Wound strength in postoperative keratoplasties is now being evaluated on a routine basis to determine the effect of topical medications and surgical techniques. All grafts measured to date reveal "bulging" or weakness of the wound margin by holography even though clinically they are fully "healed." Only one patient had a vascularized region of the wound that was stronger than surrounding cornea. It is no longer necessary to resort to pulling the wound apart in animals for measurement of tensile strength.
Subject(s)
Corneal Transplantation , Holography/methods , Wound Healing , Adult , Aged , Cornea/physiology , Electrocardiography , Female , Holography/instrumentation , Humans , Male , Middle Aged , Tensile Strength , Transplantation, HomologousABSTRACT
The projected beam radiance of several common ophthalmologic instruments was measured, and potential hazard to the patient from light exposure was analyzed with reference to safety standards for coherent light. The indirect ophthalmoscopes tested appear to be "safe" under moderate voltage settings, provided exposure is reasonably brief. Slit-lamp biomicroscopy of the fundus, however, merits caution. It produces a three-times-higher retinal irradiance than the indirect ophthalmoscope. Overhead surgical lamps produce a retinal irradiance about one-third that of the indirect ophthalmoscope (for clear media and dilated pupil). This could be dangerous, since an operation may take long enough to exceed the maximal permissible exposure by several orders of magnitude. Major design changes are indicated for surgical illuminators to extend the "safe time" to the 40 to 60 min range.
Subject(s)
Light/adverse effects , Ophthalmology/standards , Retinal Diseases/etiology , Animals , Eye Diseases/diagnosis , Humans , Lighting , Macaca mulatta , Ophthalmology/instrumentation , Ophthalmoscopes , Optics and PhotonicsABSTRACT
Exposure of a monkey retina to the light from a slit lamp for 40 minutes produced a visible retinal change that disappeared after four weeks. Exposures of 20, ten, and five minutes produced no visible changes. Extensive retinal damage was produced in the macula of the other eye of the monkey by a one-hour exposure to the light from an operation microscope. This damage was almost unchanged one year later. Exposure of the monkey retina from the same operation microscope, for the same length of time, with the blue light filtered out, produced a much smaller lesion that, after one year, could not be seen visibly but was detected with fluorescein angiography.
Subject(s)
Light/adverse effects , Retina/radiation effects , Animals , Dose-Response Relationship, Radiation , Fluorescein Angiography , Haplorhini , Macaca mulatta , Microscopy , Surgical EquipmentABSTRACT
Several popular surgical microscopes were measured for source radiance. A method has been devised for calculating patient retinal exposure from these instruments. Retinal irradiance is seen to be surprisingly high, assuming dilated pupils and clear media. It ranges from 0.10 to 0.97 W/sq cm. This is one to ten times higher than that produced by an indirect ophthalmoscope. There is evidence linking light exposure during surgery to cystoid maculopathy (Irvine-Gass syndrome).
Subject(s)
Light/adverse effects , Microscopy , Retina/radiation effects , Surgical Equipment , Humans , Maximum Allowable Concentration , OphthalmoscopesABSTRACT
On routine examination, three patients demonstrated yellow-white lesions in the posterior third of the fundus. These lesions have a subtle but unique appearance. They are in the choroid and have definite borders, minimal or no elevation, a lack of secondary changes in the overlying pigment epithelium or neuroepithelium, and no pigment within the lesion or at its borders. Ophthalmoscopic and fluorescein angiographic data permit discussion of the differential diagnosis of these lesions. They may represent amelanotic nevi of the choroid.
