Biomedical subjects

L Corydon

Publications and source records attributed to L Corydon.

At least 19 recordsLinked to original sources

PubMed2000

One year follow-up of astigmatism after 4.0 mm temporal clear corneal and superior scleral incisions.

PURPOSE: To compare the effect of 2 contemporary sutureless cataract surgery incisions on corneal astigmatism 1 year after surgery. SETTING: Outpatient Clinic, Department of Ophthalmology, Vejle Hospital, Denmark. METHODS: Sixty-nine patients who had cataract surgery in 1997 with a 4.0 mm temporal clear corneal (n = 32) or superior scleral (n = 37) incision were examined 1 year postoperatively. Surgically induced astigmatism was analyzed by vector analysis, vector decomposition, and polar values using preoperative and postoperative keratometric readings. RESULTS: Vector analysis revealed a slightly lower median induced cylinder in the clear corneal patients; 0.41 diopter (D) (95% confidence limits [CL] 0.24 to 0.67 D) versus 0.61 D (95% CL 0.49 to 0.73 D) (P < .05). Decomposition of the induced cylinder (against the rule/total) showed statistically significant differences in the direction of the cylinder; 0.21 (95% CL 0.03 to 0.41) versus 0.90 (95% CL 0.82 to 0.95) (P < .00001). The directional difference was confirmed by polar values. CONCLUSION: Both incisions induced low and comparable amounts of astigmatism. The directional differences were modest. Findings in previous studies of a poor outcome after clear corneal incisions were not confirmed in this long-term follow-up.

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PubMed1998

Relationship between preoperative axis of astigmatism and postoperative astigmatic change after superior scleral incision phacoemulsification.

PURPOSE: To evaluate the effect of the preoperative axis of astigmatism on the outcome of corneal astigmatism after sutured 5.2 to 5.7 mm superior incision phacoemulsification. SETTING: Departments of Opthalmology, Odense and Vejle Hospitals, Denmark. METHODS: Seventy-three consecutive patients with preoperative corneal astigmatism of 2.0 diopters (D) or less, axial length between 20.0 and 25.5 mm, and no eye disease except cataract were grouped according to preoperative with-the-rule (WTR) or against-the-rule (ATR) astigmatism. The keratometric cylinder, induced keratometric cylinder (subtraction), and induced cylinder (Jaffe) were measured and calculated 10 to 12 months postoperatively. RESULTS: The postoperative keratometric cylinder and induced keratometric cylinder were significantly higher in the ATR group (P < .00001; mean difference [95% confidence limits]: 0.76 D [0.54; 0.98] and 0.69 D [0.46; 0.92], respectively). There was no significant difference between groups in induced cylinder (Jaffe). CONCLUSION: The estimated differences were significantly in favor of patients with preoperative WTR astigmatism. The findings support using temporal incision in cases with a preoperative ATR axis of astigmatism.

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PubMed1998

Posterior capsule opacification and neodymium: YAG capsulotomy with heparin-surface-modified intraocular lenses.

PURPOSE: To compare the effect of heparin-surface-modified (HSM) and conventional unmodified poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) on the formation of posterior capsule opacification (PCO). SETTING: Department of Ophthalmology, Vejle Hospital, Denmark. METHODS: This prospective, randomized, double-blind study comprised 250 eyes of 246 patients who had uneventful extracapsular cataract extraction in otherwise healthy eyes with implantation of a biconvex IOL or a convex-plano lens with a continuous laser ridge. Patients were examined once a year for 3 years, at which time the degree of PCO was recorded. A neodymium:YAG laser capsulotomy was performed if certain criteria were met. RESULTS: The incidence of PCO was statistically significantly higher in eyes with an HSM convex-plano laser-ridge IOL than in those with an unmodified convex-plano lens (P < .005). There were no significant differences between any other groups. CONCLUSION: The incidence of PCO was higher in eyes with an HSM convex-plano IOL with a laser ridge.

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PubMed1998

Retinal detachment after cataract extraction in myopic eyes.

PURPOSE: To determine the incidence of retinal detachment (RD) after cataract extraction in people 40 years of age or older with axial myopia (i.e., axial length > or = 25.5 mm). SETTING: Fifteen Danish eye clinics. METHODS: Two hundred forty-five eyes had cataract extraction performed at 15 eye clinics; 237 eyes had extracapsular cataract extraction (ECCE) and 8 eyes, intracapsular cataract extraction (ICCE). Postoperative data were reported by the practicing ophthalmologists. Mean follow-up was 27 months (range 14 to 32 months). RESULTS: Five RDs occurred in the 245 eyes (2.0%). Excluding the ICCE cases and the two cases of combined cornea transplantation and ECCE, RD occurred in 4 of the 235 eyes that had ECCE (1.7%). The incidence after ECCE with posterior chamber lens implantation was 1.4%. Complete postoperative status was reported on 158 eyes. Forty-eight eyes (30.4%) had a neodymium:YAG capsulotomy and 3 (6.0%) developed an RD 1, 3.5, and 21 months after the capsulotomy. CONCLUSION: The RD incidence after ECCE with posterior chamber lens implantation was low but higher than that in unselected populations. The incidence increased after laser capsulotomy.

Adult↗

PubMed1998

Two year follow-up of astigmatism after phacoemulsification with adjusted and unadjusted sutured versus sutureless 5.2 mm superior scleral incisions.

PURPOSE: To evaluate changes in astigmatism 6 months to 2 years after 5.2 mm superior scleral incision phacoemulsification using 3 closures. SETTING: Department of Ophthalmology, Vejle Hospital, Vejle, Denmark. METHODS: This long-term follow-up study included 75 consecutive phacoemulsification patients who were randomly allocated to 1 of 3 incision closures: 1 intraoperatively adjusted cross suture, 1 unadjusted cross suture, no suture. Postoperative astigmatism after 1 and 2 years was evaluated by keratometric cylinder, induced astigmatism (Naeser's polar values), induced cylinder (Jaffe's vector analysis), and vector decomposition (Olsen). The data were compared with 1 week values. RESULTS: In the previous study, median astigmatism after 6 months was similar in all 3 groups, but only the sutureless group showed early stability. Significant against-the-rule (ATR) changes were seen in the sutured cases (P < .01). The 1 and 2 year follow-up showed continued stability in the sutureless cases. The adjusted-suture group exhibited stability after 6 months, while the unadjusted-suture group showed a further tendency to change ATR. At 2 years, median ranges of astigmatism were -0.49 to -0.90 diopter (D) (Naeser), 0.77 to 1.02 D (Jaffe), and 96% to 98% ATR (Olsen). The intergroup differences were not statistically significant. CONCLUSION: Two year follow-up confirmed that sutureless closure led to early astigmatism stability. Using a suture prolonged the postoperative period of astigmatism instability, and if used without intraoperative adjustment, a tendency toward a less predictable outcome persisted after 2 years.

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PubMed1997

One-handed phacoemulsification with low settings.

We describe a technique in which one-handed phacoemulsification with low aspiration flow and vacuum is performed with a peristaltic pump machine. With this technique, ultrasonic energy can be used for nucleus segmentation without the need for a second instrument. Measurements in cadaver eyes and clinical experience showed the technique to be simple, effective, and safe.

Humans↗

PubMed1996

[Increasing waiting lists for cataract surgery in the county of Vejle].

For several years the waiting list for cataract surgery has increased in the county of Vejle, Denmark. To reveal any change of indications for cataract surgery accounting for this increase, we analyzed referral notes and files in two samples of 86 and 72 patients examined preoperatively in 1991 and 1993. No significant difference was found between the groups regarding age, visual acuity, other eye diseases than cataract, diabetes, treatment with steroids, anisometropia or occupational disability due to poor vision. Thus no signs of changed indications for cataract surgery were found comparing the two samples. Median waiting time from referral to surgery had increased highly significantly from 1991 to 1993 (p << 0.01). The number of cataract operations per year was unchanged in the period. We propose that the increasing waiting time could be attributed to more people wanting cataract surgery, reflecting growing demands for good visual functioning and better expectations of the outcome after surgery.

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PubMed1996

Astigmatism after phacoemulsification with adjusted and unadjusted sutured versus sutureless 5.2 mm superior scleral incisions.

PURPOSE: To evaluate changes in astigmatism in the first 6 months after 5.2 mm superior scleral incision phacoemulsification using three different closures. SETTING: Department of Ophthalmology, Vejle Hospital, Denmark. METHODS: This study comprised 75 consecutive patients who had 5.2 mm superior scleral incision phacoemulsification. Patients were randomly assigned to one of three groups based on type of incision closure: Group 1, one intraoperatively adjusted cross suture; Group 2, one unadjusted cross suture; Group 3, no suture. Inclusion criteria were preoperative astigmatism of 2.00 diopters (D) or less (range of median 0.74 to 0.81 D) and no eye disease except cataract. Postoperative astigmatism was evaluated by keratometric cylinder, induced astigmatism (Naeser), and induced cylinder (Jaffe) on the first day and after 1 week and 1, 3, and 6 months. Time before stability was estimated. RESULTS: All groups had the same level of postoperative keratometric cylinder with no significant change between 1 week and 6 months (range of median 0.81 to 1.06 D). The groups reached the same level of induced astigmatism (Naeser) 3 to 6 months after surgery (range of median -0.44 to -0.64 D). Group 3 (sutureless) reached that value after 1 week, and induced astigmatism was stable thereafter. Both sutured groups (Groups 1 and 2) had a highly significant change between the first week and third month (P < .01). There were no significant intergroup differences in induced cylinder (Jaffe), which stabilized after 1 week in Groups 1 and 2 and after 1 month in Group 3 (range of median 0.61 to 0.87 D). During the early postoperative period, variation was highest in Group 2. CONCLUSIONS: Keratometric cylinder, induced astigmatism, and induced cylinder 3 to 6 months postoperatively were similar among the three groups, but early stability was only seen in the sutureless group. If a suture is used, intraoperative adjustment seems to result in lower variations in the early postoperative period.

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PubMed1995

Intraocular lens power calculation with an improved anterior chamber depth prediction algorithm.

The accuracy of intraocular lens (IOL) power calculation was evaluated in a multicenter study of 822 IOL implantations using the Binkhorst II, Sanders/Retzlaff/Kraff (SRK I, SRK II, SRK/T), Holladay, and Olsen formulas. All but the first of these were optimized in retrospect with calculation of the SRK A-constant, the Holladay surgeon factor, and the Olsen pseudophakic anterior chamber depth (ACD) for each lens style. The ACD prediction of the Olsen formula was based on a previously described regression formula incorporating preoperative ACD, corneal height, axial length, and lens thickness. Among the optical IOL power calculation formulas, the highest IOL power prediction error was found with Binkhorst's and the lowest with Olsen's, which was more accurate than the SRK/T and the Holladay formulas (P < .05). The SRK/T formula was significantly more accurate than the original SRK regression formulas (P < .001). When analyzed for axial length dependence, all formulas showed the least error in the normal range. Error of the Olsen formula was lower than that of the others in the axial length interval 20 mm to 26 mm. No differences in accuracy were found between the optical IOL calculation formulas in eyes with an axial length above 26 mm (P < .05). The accuracy of IOL power calculation can be improved with optical formulas using newer-generation ACD-prediction algorithms.

Adult↗

PubMed1995

Contrast sensitivity, glare, and visual function: diffractive multifocal versus bilateral monofocal intraocular lenses.

We measured contrast sensitivity binocularly in different light conditions in nine patients with bilateral diffractive multifocal intraocular lenses (IOLs) and nine patients with bilateral monofocal IOLs. In general, the diffractive multifocal group had a lower mean contrast sensitivity. Patients completed a questionnaire that asked about their vision under daylight, twilight, and sunshine conditions. Monofocal patients had complete visual restitution in all light conditions. Multifocal patients reported several visual problems, especially when driving at night, but also in normal daylight and cloudy weather conditions.

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PubMed1995

Intraocular pressure seven years after extracapsular cataract extraction and sulcus implantation of a posterior chamber intraocular lens.

Seven years after extracapsular cataract extraction (ECCE) and sulcus implantation of a posterior chamber intraocular lens, we measured the intraocular pressure (IOP) in 28 eyes of 28 patients. The results were compared with the preoperative IOP and with the postoperative IOP at four months and 2 1/2 years. The mean IOP value seven years after surgery was 1.3 mm Hg lower than the preoperative mean value. No significant difference was found among the values at four months, 2 1/2 years, and seven years. One patient experienced a marked rise in IOP between 2 1/2 years and seven years and was excluded from the calculations. However, we could not tell whether it was a consequence of the cataract surgery. In this study, we found that IOP stabilized at a postoperative level that was significantly lower than the preoperative value and has remained there for seven years.

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PubMed1994

[Risk of cataract surgery in patients with myopia. A prospective Danish multicenter study with special reference to a complication].

A prospective Danish multicentre study was conducted to evaluate the incidence of retinal detachment after cataract extraction in myopic eyes (axial length, > or = 25.5 mm). Two hundred and forty-seven cataract extractions in myopic eyes were reported during a period of 13 months. Two hundred and forty-one eyes underwent extracapsular and six eyes intracapsular cataract extraction. The mean follow-up time for 158 eyes was seven months (ranging from 1-30 months). In five cases a retinal detachment was observed, one case was probably present preoperatively, this person had undergone intracapsular cataract extraction. The incidence of retinal detachment was thus 1.62-2.02% in the total material and 1.66% in eyes operated with extracapsular cataract extraction.

Adult↗

PubMed1994

Biomechanical aspects of the anterior capsulotomy.

We used the finite element method to evaluate different capsulotomy techniques. Nucleus expression was simulated in a computer model to visualize stress distribution in the anterior capsule. The finite element model demonstrated that the capsulorhexis edge is strong because of low and uniform stress distribution in the tissue. With can-opener and envelope capsulotomies, areas of high stress accumulation create the risk of tears during surgery.

Cataract Extraction↗

PubMed1994

Peribulbar anaesthesia. A clinical evaluation of two different anaesthetic mixtures.

Fifty-four consecutive cases of single injection peribulbar anaesthesia performed by the same ophthalmologist were evaluated concerning clinical effect on motility/akinesia and pain. The patients were randomly selected to one of two different mixtures of anaesthetics, one containing lidocaine, bupivacaine, adrenaline and hyaluronidase. The other lidocaine and bupivacaine. The mixture with adrenalin and hyaluronidase was significantly more effective than the other (success rates of 77.8% and 25.9%, p < 0.005).

Anesthesia, Local↗

PubMed1993

Using the surgical result in the first eye to calculate intraocular lens power for the second eye.

This paper examines the possibility of using the surgical result in the first eye when planning the intraocular lens power for the second eye. Two methods were considered: (1) an empirical method by which one regards the second procedure as a repeat of the one in the first eye and calculates the power from the actual refractive error obtained in the first eye and (2) a theoretical method by which one measures the pseudophakic anterior chamber depth (ACD) of the first eye and uses this value to plan for the second eye. Based on the data from 136 second eye procedures using extracapsular cataract extraction, the prediction error of the empirical method ranged from -10.5 to +9.5 diopters. The error of the theoretical method ranged from -2.3 to +2.8 diopters, which was significantly more accurate than the empirical method (P < .001). We conclude that the fellow eye ACD may be used as a guideline for the assumed ACD of the second eye. However, such use of the fellow eye ACD could not be shown to improve power calculation predictions significantly.

Adult↗

PubMed1993

Strength of the lens capsule during hydroexpression of the nucleus.

In planned extracapsular cataract extraction, hydroexpression of the nucleus has been introduced to facilitate nucleus delivery when performing capsulorhexis. The hydroexpression technique induces a fluid pressure in the capsular bag, which may rupture the posterior capsule. In a human cadaver eye model the pressure at the capsule's rupture point was determined in 16 cadaver eyes and compared to the fluid pressure in the capsular bag during hydroexpression of the nucleus in 32 eyes. The posterior capsule was able to withstand a pressure of 59 +/- 10 mm Hg (mean +/- SD) without rupturing. During hydroexpression of the nucleus the pressure was less than 12 mm Hg (3 mm Hg to 12 mm Hg) when the diameter of the capsulorhexis opening was 5.5 mm or more (measurement in the anterior chamber). Thus hydroexpression of the nucleus seems to be a safe technique when the diameter of the capsulorhexis is 5.5 mm or more.

Adult↗

PubMed1993

Hydroexpression and viscoexpression of the nucleus through a continuous circular capsulorhexis.

When a continuous circular capsulorhexis (CCC) is performed, conventional nucleus expression may be impossible because of the strong capsular rim. Hydroexpression of the nucleus seems to overcome the problem if the capsulorhexis opening is large enough. Because a viscoelastic material may be an even more gentle tool than balanced salt solution (BSS), hydroexpression and viscoexpression were evaluated in 16 pairs of human cadaver eyes. The diameter of the capsulorhexis opening ranged from 4 mm to 6 mm; it was the same in each pair of eyes. Hydroexpression was performed in one eye using BSS and viscoexpression was performed in the fellow eye using sodium hyaluronate (Healon Yellow). The fluid pressure in the capsular bag was measured during both procedures. The pressure was higher during hydroexpression than during viscoexpression. The pressure difference between fellow eyes ranged from 0 to 32 mm Hg and was most marked when the CCC opening was small. This correlation was significant (P < .05). Viscoexpression may enhance the safety in cases with a small CCC opening or in those that are otherwise difficult.

Adult↗

PubMed1993

Contrast sensitivity and glare in patients with a diffractive multifocal intraocular lens.

Contrast sensitivity was measured in 25 patients who had a multifocal diffractive intraocular lens and in 23 control patients with a monofocal lens in four simulated light conditions: (1) daylight, (2) daylight with peripheral glare, (3) twilight, (4) twilight with central glare. In normal daylight and twilight, contrast sensitivity of the multifocal group was significantly lower than the control group's (P < .05). The difference was 0.13 log units for the multifocal group and 0.17 log units for the control group (mean value across the tested frequency from 1.5 to 18 cycles/deg). Peripheral glare reduced contrast sensitivity under daylight conditions in both groups (P < .05), but the loss did not differ significantly between the two (P > .05). Central glare reduced contrast sensitivity under twilight conditions in both groups (P < .05), with the greatest loss in the multifocal patients (P < .001). We conclude that the most significant loss of contrast sensitivity in patients with the diffractive multifocal intraocular lens is found with central glare under twilight conditions.

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