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.

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.

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.

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.

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.

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.

Diathermic capsulotomy versus capsulorhexis: a biomechanical study

PURPOSE

To compare the mechanical quality of a capsulotomy opening performed by diathermy with that made by capsulorhexis (tearing).

SETTING

Department of Ophthalmology, Vejle Hospital, Denmark.

METHODS

This study included 12 pairs of human cadaver eyes and 20 pairs of pig eyes. One in each pair was randomly selected for one capsulotomy technique. The capsulotomy edge was stretched in a materials testing machine until break; force and elongation values were continuously recorded.

RESULTS

In humans, the extensibility of the diathermic capsulotomy edge was approximately half that of the capsulorhexis edge (mean 38% +/- 4 [SD] versus 68% +/- 6), and the force required to break the edge was reduced by a factor of five (26 +/- 8 mN versus 134 +/- 36 mN).

CONCLUSION

The mechanical quality of the diathermic capsulotomy edge is significantly less than that of the capsulorhexis edge, which indicates that the diathermic capsulotomy edge would withstand less surgical manipulation.

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.

[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.

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.

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.

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.

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).

[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.

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.

Retrobulbar anaesthesia. A clinical evaluation of four different anaesthetic mixtures

One-hundred and thirty-nine consecutive cases of retrobulbar blocks were evaluated concerning clinical effect on motility and pain. The patients were randomly selected to one of four different mixtures of anaesthetics. A mixture containing lidocaine w/adrenaline, bupivacaine w/adrenaline and hyaluronidase was shown to be significantly more effective than any of the other tested mixtures concerning analgesia and significantly better than mixtures without hyaluronidase concerning motility/akinesia.

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.

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.

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.

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.

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.

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.

Continuous circular capsulorhexis and nucleus delivery in planned extracapsular cataract extraction

A technique for nucleus delivery through a continuous circular capsulorhexis in planned extracapsular cataract extraction is presented. The concept of hydro- and viscoexpression of the nucleus is explained, and a strongly bent cannula specially designed for the procedure is introduced.

[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.

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.

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.

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).

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.

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.

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.

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.

[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.

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.

Corneal ulcer after exposure to vapours from bone cement (methyl methacrylate and hydroquinone)

An operation nurse repeatedly developed a corneal ulcer while mixing bone cement. It is suggested that the ulcer developed because of a composite effect of vapours from bone cement (methyl methacrylate monomer and hydroquinone), in spite of the fact that the Occupational Health Guidelines and the national threshold limit values for chemical substances had been respected. In-vitro and in-vivo animal studies are reviewed.

Corneal astigmatism after cataract extraction. A comparison of corneal and corneoscleral incisions

Corneal astigmatism after cataract surgery by way of corneal incision (C, n = 62) and corneo-scleral incision (CS, n = 61) was followed for six months. Corneal incisions were closed by continuous nylon 10--0 (7--25 loops, median 14). Corneo-scleral incisions were sutured with single knots (2--10, median value 5). Keratometric results in the C and CS groups are compared. Concerning the degree of astigmatism, pre-operative median values were 0.5 and 0.7 D, respectively. After one week they were 4.5 and 3.0 D; after two weeks 3.3 and 3.0 D; after four months 3.0 and 2.0 D; after six months (final status) 1.5 and 1.7 D, respectively. The differences between C and CS were not significant. For both, astigmatism after cataract surgery did not quite return to pre-operative levels. Concerning the axis (weaker meridian) of corneal astigmatism, the C cases retained their pre-operative distribution, while the CS cases showed the classical shift towards against-rule astigmatism. Final corrected visual acuity was of the same order in the C and CS group. Due to frequent shifts, also of the axis, it is recommended by early (preliminary) glass prescription not to correct the astigmatism, but to give only the best spherical correction.

A double-blind study of the influence of tranexamic acid on the central corneal thickness after cataract extraction

A double-blind study of the influence of systemic tranexamic acid on the central corneal thickness after cataract extraction was performed in 17 pairs of patients. Apart from the cataract, no were present. A sequential statistics was used to show that the increase in central corneal thickness after operation was significantly less in the tranexamic acid treated group than in the placebo group. There was no significant difference in intraocular pressure between the tranexamic acid and the placebo treated group. The possible influence of tranexamic acid on the thickness controlling mechanism of the cornea is discussed, and studies concerning the fibrinolytic system, the complement system and the aqueous humour amino acid treated patients are mentioned.

Progress in cataract surgery using microsurgical technique

A microsurgical technique for cataract extraction is presented. The operations were performed with a corneal incision and a continuous nylon 10-0 suture. This technique is evaluated by the study of 1289 cases, consecutively operated on. The complication rate was very low. Haemorrhage in the anterior chamber was found in 1%. Delayed reformation of the anterior chamber occurred in only two cases. No cases of iris prolapse occurred. The intraocular pressure was not interferred with by the operation. Wound rupture following removal of the suture three months post-operatively occurred in 1%. The advantages of the corneal incision and continuous nylon suture are discussed (less irritation, good and secure wound closure).