ABSTRACT
Intravitreal sodium fluorescein was used to simulate equilibrium fluorescein kinetics, thereby allowing simple measurement of the aqueous to cornea fluorescein distribution ratio. Two groups of rabbit corneas were studied: normal corneas and corneas wounded by freezing. The aqueous to cornea fluorescein distribution ratio was approximately 0.4, was not significantly different in groups of normal or wounded eyes and little variability was noted. In addition, a comparison of in vivo and in vitro measurements of corneal fluorescein concentration in wounded eyes suggests that in vivo protein-bound fluorescein in the cornea fluoresces less efficiently than free fluorescein.
Subject(s)
Aqueous Humor/metabolism , Cornea/metabolism , Corneal Diseases/metabolism , Edema/metabolism , Fluoresceins/metabolism , Animals , Cornea/anatomy & histology , Cornea/pathology , Corneal Diseases/pathology , Edema/pathology , Fluorescein , Fluorometry , Models, Biological , Photography , Rabbits , Reference Values , Spectrometry, Fluorescence , Tissue DistributionABSTRACT
Wide-field specular microscopy, fluorophotometry, pachymetry, and scanning electron microscopy are used to characterize a reproducible, in vivo model of corneal endothelial injury and recovery in the rabbit. Following an 8-mm central cryo-injury, the cornea remains thickened for as long as 3 weeks. Mean endothelial permeability to fluorescein is above normal for 10 days following injury, but by 14 days postinjury the endothelial permeability to fluorescein is not statistically significantly different from preinjury control values, thus indicating that endothelial permeability probably returns to normal by approximately 2 weeks postinjury. Cell morphology, as determined by scanning electron microscopy, is also essentially normal by 2 weeks postinjury. Endothelial permeability appears to recover before stromal thickness normalizes, suggesting a lag in recovery of endothelial pump function.
Subject(s)
Cold Temperature/adverse effects , Corneal Injuries , Animals , Cell Count , Cornea/metabolism , Cornea/pathology , Cornea/physiopathology , Endothelium/physiopathology , Epithelium/metabolism , Epithelium/pathology , Fluorescein , Fluoresceins/metabolism , Microscopy, Electron, Scanning , Permeability , RabbitsABSTRACT
Twenty-three patients who underwent penetrating keratoplasty were evaluated preoperatively for potential retinal acuity utilizing the Randwal Laser Interferometer and the Mentor Potential Acuity Meter. When compared with Snellen visual acuity during the early postoperative period (1-6 months), both instruments were useful as qualitative predictors of macular function when used in the presence of mild to moderate corneal edema. The laser interferometer was somewhat more accurate in the severe cases of corneal edema.
Subject(s)
Corneal Diseases/surgery , Corneal Transplantation , Interferometry/methods , Visual Acuity , Cataract Extraction , Humans , Lasers , Postoperative Complications/etiology , Refraction, OcularABSTRACT
Recent advances in technology have contributed to better evaluation of potential visual acuity in patients with cataracts. The blue field entoptic test, the clinical interferometers, and the Potential Acuity Meter are discussed with respect to their basic principles, clinical uses, advantages, and limitations. There are problems in evaluating these instruments, but their findings can play an important role in clinical decision making.
Subject(s)
Cataract Extraction , Visual Acuity , Humans , Interferometry , Light , Postoperative Period , Prognosis , Vision Tests/methods , Vision, EntopticABSTRACT
A new instrument allows accurate measurement of retinal visual acuity behind mild to moderate cataracts. Mounted on a slit lamp, the Potential Acuity Meter projects a Snellen visual acuity chart into the eye via a narrow beam of light converging to a minute aerial aperture only 0.15 mm in diameter. The examiner aims the narrow beam through "windows" in the cataract, avoiding blockage or scattering of the light that would otherwise occur. In 47 cataractous eyes having best preoperative visual acuity of 20/200 and better, the postoperative visual acuity was predicted to within three lines in 100% of cases, and to within two lines in 91%. With a successful result from cataract surgery defined as postoperative vision of 20/40 or better, the prediction of success with the Potential Acuity Meter was correct in 95% of cases.
