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Biomedical subjects

L Corydon

Publications and source records attributed to L Corydon.

At least 19 recordsLinked to original sources
PubMed1992

Visual outcome following complicated extracapsular cataract extraction.

In a prospective study of 1,597 consecutive extracapsular cataract extractions (ECCE), we review 49 cases complicated by capsular or zonular rupture with or without vitreous loss. The ECCEs were divided into two groups depending on the type of intraocular lens (IOL) implanted. In Group A, whose patients received an anterior chamber lens, we found a significantly (P < .05, t-test) worse postoperative visual acuity than in Group B whose patients received a posterior chamber lens. We therefore suggest that in the presence of a capsular tear and vitreous loss, one should try to implant a posterior chamber lens rather than an anterior chamber lens to obtain as good a visual acuity as possible.

Aged↗
PubMed1992

Prediction of pseudophakic anterior chamber depth with the newer IOL calculation formulas.

Five methods for predicting pseudophakic anterior chamber depth (ACD) by five previously described intraocular lens power calculation formulas (Binkhorst II, Lepper and Trier, Holladay et al., Sanders-Retzlaff-Kraff (SRK/T), Olsen et al.) were evaluated in a series of 640 patients with a posterior chamber lens implant. Significant differences in formula performance were found in unusually short and long eyes. High errors were found in long eyes with the Lepper and Trier formula, the Holladay formula, and the SRK/T method. The highest accuracy was found with the Binkhorst formula and our previously described linear regression formula which expresses the pseudophakic ACD as a function of the average pseudophakic ACD for a given lens style, the preoperative ACD, and the axial length. The use of the preoperative ACD in combination with the axial length for the prediction of the pseudophakic ACD can therefore be expected to improve the accuracy of IOL power calculation.

Adolescent↗
PubMed1991

[Clinical experience with a bifocal intraocular lens].

At cataract operation, the opaque cataractous lens is removed from the eye and is replaced by an artificial intraocular lens. Employing modern technology, development of a bifocal intraocular lens based on diffraction optic has now proved possible. The lens contains correction for distant vision and also for close work so that the patients may be independent of glasses. Sixty-two eyes with bifocal intraocular lenses were followed-up for approximately one year. The results are promising. 84% of the patients could read small print without corrective glasses. The accuracy by which the intraocular lens power can be calculated preoperatively and the surgical control of astigmatism in the eye are of decisive importance for the success of the lens.

Adult↗
PubMed1991

Accuracy of the newer generation intraocular lens power calculation formulas in long and short eyes.

The accuracy of two newer generation theoretical intraocular lens (IOL) power calculation formulas and of the empirical SRK I and II formulas was evaluated in a series of 500 IOL implantations including a series of unusually long and short eyes. The prediction error of the theoretical formulas was found to be largely unaffected by the variation in axial length and corneal power, while the prediction of the SRK I formula was less accurate in the short and long eyes. The prediction of the SRK II formula was more accurate than the SRK I in that no systematic offset error with axial length could be demonstrated. However, because of a relatively larger scatter in the long eyes and a significant bias with the corneal power, the absolute error of the SRK II formula was higher than that of the theoretical formulas in the long eyes. The higher accuracy of the newer generation theoretical formulas was attributed to their improved prediction of the pseudophakic anterior chamber depth.

Adult↗
PubMed1991

Stretching capacity of capsulorhexis and nucleus delivery.

The stretching capacity of the continuous circular capsulorhexis was studied in 30 human cadaver eyes. The capsulorhexis was found to have a remarkable stretching capacity, allowing safe nucleus delivery in planned extracapsular cataract extraction using hydroexpression. The difficulties encountered when trying to deliver the nucleus by external pressure to the sclera are discussed.

Adult↗
PubMed1990

Theoretical versus SRK I and SRK II calculation of intraocular lens power.

The predictability of a theoretical, computerized (PC-assisted) intraocular lens (IOL) power calculation method and of the Sanders-Retzlaff-Kraff [SRK] I and II methods was evaluated from preoperative and postoperative biometry in 202 cataractous patients who had extracapsular cataract extraction (ECCE). The theoretical method resulted in the lowest range and standard deviation of the error, and the highest correlation coefficient between the observed and the predicted refraction (P less than .05). The superiority of the theoretical approach was most clearly demonstrated when the postoperative measurements were used in the predictions (P less than .001). This demonstrated the potential accuracy of the formula used and the importance of incorporating methods to predict the IOL position after surgery. If the prediction of the IOL chamber depth was properly corrected for the axial length dependence, a high prediction accuracy could be obtained in short as well as in long eyes.

Adult↗
PubMed1990

Prediction of postoperative intraocular lens chamber depth.

The postoperative intraocular lens (IOL) chamber depth was predicted using a multiple linear regression analysis of the postoperative chamber depth as a function of the corneal height, the preoperative chamber depth, and the axial length in 279 patients with a posterior chamber lens implant. Based on a linear regression formula incorporating these preoperatively defined parameters, the postoperative IOL chamber depth could be predicted with a correlation coefficient of 0.71 and an error of +/- 0.30 mm (SD). It is concluded that an individual prediction of the IOL chamber depth will improve the accuracy in IOL calculation.

Aged↗
PubMed1990

New multifocal intraocular lens design.

The first clinical experience with a new diffractive multifocal intraocular lens implanted in 55 eyes of 53 patients is reported. Excluding four patients with preoperative senile macular degeneration, the best corrected visual acuity was 20/40 or better and the near vision without any add to the best distance correction was J2 or better in all cases three, six, and 12 months postoperatively.

Cataract Extraction↗
PubMed1990

Contrast sensitivity in patients with a new type of multifocal intraocular lens.

Contrast sensitivity was measured in 13 pseudophakic eyes of ten patients who had a new type of diffractive multifocal intraocular lens (IOL) and compared with an age-matched control group with a conventional monofocal IOL. All selected cases had a postoperative follow-up of four to six months and a corrected visual acuity of 20/20 or better. For distance vision, no significant difference in contrast sensitivity could be found between the two groups, indicating an uncompromised distance focus of the multifocal IOL. For near vision, an overall decrease in the contrast sensitivity of 0.19 log units (mean value across the tested frequency from 1.5 to 18 cycles/deg) was found in the multifocal group when these patients were tested without near addition and compared with the controls with near addition (P less than .05). This indicated the near focus of the multifocal IOL to be somewhat less efficient than the far focus. We find these results promising for the new diffractive multifocal IOL.

Accommodation, Ocular↗
PubMed1990

Contrast sensitivity as a function of focus in patients with the diffractive multifocal intraocular lens.

Contrast sensitivity as a function of focus and visual acuity as a function of contrast were investigated in 19 patients with a diffractive multifocal intraocular lens and compared with 19 control patients with a conventional monofocal implant. The contrast sensitivity of the multifocal patients followed a bimodal curve with a maximum sensitivity at the far focus and a second peak at the near focus, corresponding to about +3 diopters in the spectacle plane. The maximum sensitivity of the multifocal group was 0.14 log units lower than the control group (P less than .05). In the near region, the contrast sensitivity of the multifocal patients exceeded that of the control group from +2 diopters and inward. No difference in distance visual acuity was found with high contrast letters. With intermediate contrast letters, the visual acuity of the multifocal patients was lower than that of the control group (P less than .05).

Aged↗
PubMed1989

[Control of refraction in cataract surgery].

The optical problems associated with cataract surgery are reviewed and methods to control the refractive state of the eye after the operation are presented. The clinical benefit of a calculation of intraocular lens (IOL) power from measurements of corneal curvature and eye length is demonstrated in a series of operated patients from two Danish eye departments. It is concluded, that the postoperative refraction can be controlled with a reasonable accuracy. Large and unexpected deviations in the postoperative refraction are avoided in this way, and in a number of cases it is possible to reduce the need for spectacles after the operation.

Cataract Extraction↗
PubMed1989

[Soft intraocular lenses].

Hard intraocular polymethylmethacrylate (PMMA)-lenses have been implanted following cataract extractions since 1949, and their good properties are well proven. Soft intraocular lenses have only been implanted since 1976. Their chemical and physical properties, advantages and disadvantages are discussed with reference to the well known PMMA-lenses. In the short term the patients obtain the same visual acuity with soft intraocular lenses as with hard intraocular lenses, and it is the impression, that the soft lenses are more tissue compatible, but more prolonged follow up is required.

Aged↗
PubMed1988

Posterior capsule fibrosis and intraocular lens design.

Four different posterior chamber lens designs were used in 1,845 consecutive, unselected extracapsular cataract extractions performed over a 31-month period in Vejle, Denmark. Ninety-seven eyes (5.3%) required a posterior capsulotomy during a postoperative observation period ranging from two to 32 months. At 16 months postoperatively, the cumulative capsulotomy rate was 7.1% with plano-convex anterior lenses, but only 1.7% with meniscus lenses and 1.8% with continuous ridged lenses. These results suggest that close contact between the posterior capsule and the optic could induce early posterior capsule opacification.

Cataract Extraction↗