The histopathology of intraocular lenses.
(65/91)Seventeen eyes from patients who had had successful intraocular lens surgery were obtained after the patients died: 14 posterior chamber lenses, 2 anterior chamber lenses, and 1 iris fixation lens. None of these lenses showed significant inflammatory reaction or scarring. Despite iris tucking in the eyes with anterior chamber lenses and asymmetrical supporting loop location in the eyes with posterior chamber lenses, the intraocular lenses seemed to function well. (+info)
Retinal function in high refractive error assessed electroretinographically.
(66/91)The retinal function of patients with high refractive error was studied electroretinographically. Thirty-one hypermetropic patients, 7 myopic patients, and 7 patients with either unilateral or bilateral aphakia participated in the study. The ERG responses were measured in the light- and dark-adapted states. It was found that myopic eyes were characterised by subnormal amplitude but normal pattern, expressed by normal relationship between the b-wave amplitude and the a-wave amplitude. In aphakia the ERG responses were of normal amplitude and pattern. However, the hypermetropic patients could be divided into 3 groups. One group included subjects with a subnormal b-wave to a-wave relationship. The second group was characterised by a normal b- to a-wave relationship, while patients belonging to the third group exhibited supernormal b-wave to a-wave relationship. This classification of hypermetropic subjects did not correlate with the axial length of the eye or the refraction of the ocular media. (+info)
Intraocular lens power calculation for planned ametropia: a clinical study.
(67/91)A prospective series of 25 eyes received an intraocular lens (IOL) of power calculated for planned ametropia, by means of the formulae of R. D. Binkhorst, from data of axial length, corneal curvature, and postoperative anterior chamber depth. All the postoperative refractions were within the +/- 2 D range from the predicted refraction, confirming the clinical value of such calculation. A retrospective study of 100 eyes which had received a +19 D power Binkhorst IOL showed a wide range of change in refraction extending up to the +/- 6 D range, indicating that a 'standard' power IOL cannot be relied upon to reproduce the preoperative refraction. Calculation of IOL power from biometric data is essential when controlled postoperative ametropia is required. (+info)
Corneal thickness response to high and low water content lenses in aphakic eyes.
(68/91)A high water content lens (Scanlens 75, +14.5 dioptres) and a low water content lens (Bausch and Lomb Soflens H3, +14.5 dioptres) were compared with respect to corneal thickness response after 6 hours of wear in a provocative test on 12 aphakic eyes. The mean increase in central corneal thickness was 3.3% for Scanlens and 6.4% for Soflens. This difference is statistically highly significant (p less than 0.001). There seems to be a correlation between the response to Scanlens and that to Soflens when the responses of each eye were plotted against each other. Average lens thickness correlated somewhat better with corneal thickness increase than did central lens thickness. (+info)
Colour perception in pseudophakia.
(69/91)Minor differences in colour perception between pseudophakic, phakic, and spectacle aphakic eyes were identified by the Pickford-Nicholson anomaloscope and the Farnsworth-Munsell 100-hue test. The results suggest that pseudophakic eyes are more sensitive to red and less sensitive to blue than aphakic eyes corrected with spectacles. Spectrophotometer measurements reveal that the Rayner-Pearce posterior chamber intraocular lens used in this study transmits an evenly balanced colour spectrum, whereas an aphakic spectacle lens exhibits significant colour distortion, reducing the red and enhancing the blue transmission. This distortion may possibly be attributed to the increased chromatic aberration in the spectacle lens compared with the intraocular lens. (+info)
Athalamia as a late complication after keratoplasty on aphakic eyes.
(70/91)In 3 cases of keratoplasty in aphakic eyes 4--8 months after surgery a gradual flattening of the anterior chamber was observed. During the initial postoperative months there was no suggestion of any impending complication. No synechiae at the anterior chamber angle were present, the anterior vitreous face had remained intact without being in contact with the posterior corneal surface, and the intraocular pressure remained within normal limits. Separation of anterior synechiae as well as vitrectomy via pars plana resulted merely in a temporary amelioration of this condition. Within a few days the anterior chamber was abolished again. The corneal buttons displayed epithelial oedema; the deeper layers, however, remained clear. Development of secondary glaucoma was kept under control either by appropriate medication or by cyclocryotherapy. The phenomenon reported here developed only in cases in which the anterior vitreous face had remained intact. It seems possible that this type of late complication may be avoided by prophylactic vitrectomy. (+info)
A long-term follow-up study of cystoid macular edema in aphakic and pseudophakic eyes.
(71/91)Forty-four aphakic and 45 pseudophakic eyes with typical cystoid macular edema following cataract surgery were reevaluated one to four years following their initial fluorescein angiograms in an effort to compare the natural courses of the macular lesions in the two groups of eyes. Both aphakic and pseudophakic eyes in which the edema was associated with vitreous adhesions to the cataract wound experienced a lower rate of resolution than comparable cases without such adhesions. Macular edema cleared significantly more frequently in aphakic eyes than in pseudophakic cases. Pseudophakic eyes in which iris fixation had been employed had a particularly poor prognosis, which was significantly worse than the natural course observed in pseudophakic eyes associated with capsular fixation. The latter group of eyes cleared significantly less frequently than did the group of aphakic eyes without vitreous adhesions. The reasons that the natural course of cystoid macular edema in pseudophakic eyes is relatively poor are unknown, but chronic inflammation may play a significant role in the pathogenesis of this important complication. (+info)
Effects of cataract surgery on corneal function.
(72/91)Recent reports suggest that the aphakic eye develops less corneal edema than the phakic eye during hydrogel contact lens wear. Measurements were made of several ocular characteristics that might account for this difference in nine unilateral aphakic subjects. The measurements showed that compared with the phakic eye, the aphakic eye averaged a 15% lower epithelial oxygen uptake rate, 18% fewer endothelial cells, 85% loss of corneal sensitivity, and 8% thinner corneal epithelium. Both eyes of each subject were exposed to a reduced oxygen environment for 2 hr in separate experiments: (1) by wearing a thick hydrogel contact lens and closing the eyes, and (2) by exposing the eye to 100% nitrogen gas. In the gel lens-closed eye experiment the aphakic cornea swelled an average of 7.5%, compared with 11.0% for the phakic cornea. For the nitrogen gas experiment the results were 4.3% and 6.2%, respectively. Eighty-five percent of the edema was in the stromal layer. The lower swelling response for the aphakic eye was significant (p less than 0.01) in both experiments. Corneal swelling after hypoxia is considered to be caused by an increase in corneal osmolarity resulting from an increase in the rate of production of lactic acid. The reduced corneal swelling in the aphakic eye, when compared with the phakic eye, could therefore be the result of either (1) a reduction in the overall metabolic activity of the epithelium, as indicated by the lower epithelial oxygen uptake rate and the thinner corneal epithelium in the aphakic eye, or (2) an increased efflux of lactic acid from the cornea resulting from an increased endothelial permeability to lactate. (+info)