The refractive error after implantation of a posterior chamber intraocular lens. The accuracy of IOL power calculation in a hospital practice

Evaluation of postoperative refractive error correction after cataract surgery

Suboptimal cataract surgery outcomes remain a challenge in most developing countries. In Ghana, about 2 million people have been reported to be blind due to cataract with about 20% new cases being recorded yearly. The aim of this study was to evaluate postoperative correction of refractive errors after cataract surgery in a selected eye hospital in Ashanti Region, Ghana. This was a retrospective study where medical records of patients (aged 40–100) who reported to an eye hospital in Ghana from 2013–2018 were reviewed. Included in the study were patients aged ≥40 years and patients with complete records. Data on patient demographics, type of surgery, intra-ocular lens (PCIOL) power, availability of biometry, postoperative refraction outcomes, pre- and postoperative visual acuity were analyzed. Data of two hundred and thirteen eyes of 190 patients who met the inclusion criteria were analyzed. Descriptive analysis and Chi-square test were carried out to determine the mean, median, standard deviation and relevant associations. The mean ± SD age was 67.21±12.2 years (51.2% were females). Small Incision Cataract Surgery (99.5%) with 100% IOL implants was the main cataract surgery procedure in this study. Pre-operative biometry was performed for 38.9% of all patients on their first eye surgery and 41.5% for second eye surgeries. About 71% eyes in this study were blind (presenting VA<3/60) before surgery; 40.4% had post-operative VA <3/60. Pre-existing ocular comorbidities discovered post- surgery, attributed to suboptimal visual outcomes. More than half (55.3%) of patients did not undergo postoperative refraction due to loss to follow-up. Year of surgery (p = .017), follow up visits< 2months (p < .0001) and discovered comorbidity post-surgery (p = .035) were the factors significantly associated with postoperative refraction. Myopia and compound myopic astigmatism were the dominant refractive error outcomes. The timing of post-operative refraction had a significant effect on postoperative refraction done. These findings indicate a clinically meaningful significance between completion of postoperative care and postoperative refraction done. Consequently, with settings in most developing countries, where less biometry is done, it is appropriate that post-operative refractive services are encouraged and done earlier to enhance the patients’ expectations while increasing cataract surgery patronage.

Outcomes of excimer laser enhancements in pseudophakic patients with multifocal intraocular lens

Purpose

The aim of this study was to assess visual and refractive outcomes of laser vision correction (LVC) to correct residual refraction after multifocal intraocular lens (IOL) implantation.

Patients and methods

In this retrospective study, 782 eyes that underwent LVC to correct unintended ametropia after multifocal IOL implantation were evaluated. Of all multifocal lenses implanted during primary procedure, 98.7% were refractive and 1.3% had a diffractive design. All eyes were treated with VISX STAR S4 IR excimer laser using a convectional ablation profile. Refractive outcomes, visual acuities, patient satisfaction, and quality of life were evaluated at the last available visit.

Results

The mean time between enhancement and last visit was 6.3±4.4 months. Manifest spherical equivalent changed from −0.02±0.83 D (−3.38 D to +2.25 D) pre-enhancement to 0.00±0.34 D (−1.38 D to +1.25 D) post-enhancement. At the last follow-up, the percentage of eyes within 0.50 D and 1.00 D of emmetropia was 90.4% and 99.5%, respectively. Of all eyes, 74.9% achieved monocular uncorrected distance visual acuity 20/20 or better. The mean corrected distance visual acuity remained the same before (−0.04±0.06 logMAR [logarithm of the minimum angle of resolution]) and after LVC procedure (−0.04±0.07 logMAR; P=0.70). There was a slight improvement in visual phenomena (starburst, halo, glare, ghosting/double vision) following the enhancement. No sight-threatening complications related to LVC occurred in this study.

Conclusion

LVC in pseudophakic patients with multifocal IOL was safe, effective, and predictable in a large cohort of patients.

Toward zero effective phacoemulsification time using femtosecond laser pretreatment

OBJECTIVE

To compare effective phacoemulsification time after femtosecond laser pretreatment with conventional phacoemulsification and the associated effect on visual outcomes and endothelial cell loss.

DESIGN

Prospective, consecutive, single-surgeon case-control study.

CONTROLS

Controls underwent phacoemulsification cataract extraction plus insertion of an intraocular lens (IOL). Cases underwent pretreatment with the femtosecond laser followed by phacoemulsification cataract extraction and IOL insertion.

METHODS

Two hundred one eyes underwent cataract surgery between April 2012 and July 2012. Data collected included patient demographics, preoperative characteristics, femtosecond lens fragmentation method, effective phacoemulsification time (EPT), intraoperative complications, and postoperative outcomes.

MAIN OUTCOME MEASURES

Effective phacoemulsification time, intraoperative complications, corneal endothelial cell loss, as well as postoperative best-corrected visual acuity, intraocular pressure, and refractive outcomes.

RESULTS

Patient demographics were similar between groups. There was no difference between baseline cataract grades (2.59 ± 0.71 vs. 2.52 ± 0.72, not significant). One hundred percent of cases pretreated with the femtosecond laser had complete capsulotomy. Mean EPT was reduced by 83.6% in the femtosecond pretreatment group (P<0.0001) when compared with controls, with 30% having 0 EPT (P<0.0001). Effective phacoemulsification time was reduced 28.6% within the femtosecond group using improved lens fragmentation algorithms, and a further 72.8% reduction was achieved with a 20-gauge phacoemulsification tip. Overall, there was a 96.2% reduction in EPT between controls and the optimized femtosecond pretreatment group. This was associated with a 36.1% reduction in endothelial cell loss in the femtosecond group. Visual and refractive outcomes were similar to those of conventional cataract surgery.

CONCLUSIONS

Femtosecond laser pretreatment results in a significant reduction in effective phacoemulsification time, including the possibility of 0 EPT. Further reductions may be achieved using optimization of lens fragmentation patterns and surgical technique.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Predicting the necessity of LASIK enhancement after cataract surgery in patients with multifocal IOL implantation

Purpose

To investigate if the parameters measured routinely prior to cataract surgery with multifocal intraocular lens (IOL) implantation can predict the necessity of additional laser in situ keratomileusis (LASIK) to improve visual outcome.

Methods

Records of patients undergoing cataract surgery between January 2008 and December 2009 were reviewed. Individuals satisfied with visual outcome of cataract surgery and not satisfied were grouped (group 1 and 2, respectively). Preoperative data of refractive error, axial length, corneal astigmatism, intraocular pressure, and postoperative uncorrected visual acuity were recorded. Data was available for 62 patients (104 eyes), of which LASIK enhancement was deemed necessary in 21 eyes (20%; group 2). The receiver operator characteristic curves were used to discriminate between the groups and linear regression analysis was performed to predict the postoperative visual outcome.

Results

The astigmatism measured preoperatively using manifest refraction had an accuracy of 64% in discriminating between the groups. Age, spherical component of refraction, axial length, corneal astigmatism, and intraocular pressure were very close to chance prediction 59%, 57%, 56%, 51%, and 51%, respectively. The postoperative uncorrected visual acuity had an accuracy of 79% in discriminating the groups. Individuals with uncorrected visual acuity worse than 20/40 after cataract surgery were most likely to undergo LASIK enhancement; however, approximately 20% of group 2 underwent LASIK enhancement despite having visual acuity of 20/30 or better. When combined, preoperative visual acuity accounted for just 7% of variance in postoperative uncorrected visual acuity.

Conclusion

Requirement of LASIK enhancement after cataract surgery with multifocal IOL implant is complex in nature, and parameters routinely measured before surgery cannot successfully identify the group requiring LASIK enhancement or predict postoperative uncorrected visual acuity.

LASIK outcomes following multifocal and monofocal intraocular lens implantation

PURPOSE

To evaluate the efficacy, predictability, and safety of LASIK to correct residual refractive error following cataract surgery using multifocal and monofocal intraocular lenses (IOL).

METHODS

Included in this retrospective, comparative study were 100 consecutive eyes with residual refractive error that had undergone cataract surgery with monofocal or multifocal IOL implantation. Two groups were studied according to the implanted IOL--multifocal group (50 eyes, mean age 57.8 +/- 9.9 years) and monofocal group (50 eyes, mean age 51.0 +/- 10.0 years). In all cases, LASLK was performed using the SCHWIND ESIRIS excimer laser.

RESULTS

A statistically significant improvement was observed in uncorrected distance (P < .01) and corrected distance (P < .01) visual acuity at 6 months postoperatively in both groups. A statistically significant reduction was also observed in defocus equivalent and cylinder (P < .01) postoperatively. No statistically significant differences in the percentage of eyes losing lines of corrected distance visual acuity were found between groups (14% multifocal vs 4% monofocal, P = .40). When comparing eyes undergoing hyperopic LASIK in each group, a difference in the limit of statistical significance was found in the percentage of eyes with a spherical equivalent refraction within +/- 0.50 diopters (70% multifocal vs 84% monofocal, P = .06). No significant differences in predictability were found between multifocal and monofocal myopic subgroups (P = .25).

CONCLUSIONS

Laser in situ keratomileusis refinement after cataract surgery with monofocal IOL implantation provides a more accurate refractive outcome than after multifocal IOL implantation. Predictability of LASIK correction is limited in hyperopic eyes implanted with multifocal IOLs.

Conductive keratoplasty to correct residual hyperopia after cataract surgery

PURPOSE

To evaluate the efficacy, predictability, safety, and stability of conductive keratoplasty (CK) for correcting residual hyperopia after cataract surgery with intraocular lens implantation.

SETTING

Vissum-Instituto Oftalmologico de Alicante, Alicante, and Vissum-Instituto de Albacete, Albacete, Spain.

METHODS

Sixteen eyes of 16 patients had CK for the correction of residual hyperopia after cataract surgery. The CK was performed with the CK View Point Refractec (RCS-200, Refractec, Inc.). The follow-up was 12 months.

RESULTS

One year after CK, 10 eyes (62.5%) achieved an uncorrected visual acuity (UCVA) of 0.50 or better. The mean UCVA was 0.50 +/- 0.21 (SD), and the mean best spectacle-corrected visual acuity (BSCVA) was 0.68 +/- 0.24. One eye lost 1 line of BSCVA, and none lost 2 or more lines. The mean spherical equivalent refraction was +0.39 +/- 0.84 D 1 year after CK. No vision-threatening complications occurred.

CONCLUSIONS

One-year data show that CK for the correction of low to moderate hyperopia after cataract surgery was safe, stable, relatively predictable, and efficient. No complications occurred when CK was performed after phacoemulsification.

Postoperative aphakia in modern cataract surgery

PURPOSE

To study the incidence of aphakia after cataract surgery, the surgical complications that can lead to it, and the visual outcome.

SETTING

Six community-run eye clinics participating in the Swedish National Cataract Register.

METHODS

Data on cataract extractions were collected prospectively from 1997 through 2001. The data also covered the type of surgery and type of intraocular lens, including a "no lens implanted" option. All data were stored in a database. These data were supplemented with data on the intended type of surgery, type of complications, possible second surgery, and visual outcome.

RESULTS

The overall incidence of postoperative aphakia was 0.65%. In 87.1% of cases, the aphakia was not planned, corresponding to an incidence of 0.48%. Unplanned aphakia was significantly related to poor preoperative vision, old age, and the presence of ocular comorbidity. The most frequent reasons for unplanned aphakia were intraoperative capsule problems and vitreous loss. In two thirds of cases, a second operation was performed. In 41% of all cases, the final visual acuity was 0.5 or better and in 27.7%, worse than 0.1.

CONCLUSIONS

During the study period, 1 of every 200 routine cataract surgeries ended in unplanned aphakia. The incidence of surgical complications leading to unplanned aphakia and a final visual acuity worse than 0.1 (20/200) was 7.8 per 10,000 operations in cases with no ocular comorbidity and 27.6 per 10,000 operations in cases with ocular comorbidity.

Laser in situ Keratomileusis for Correction of Induced Astigmatism From Cataract Surgery

PURPOSE

To evaluate the efficacy, predictability, stability, and safety of laser in situ keratomileusis (LASIK) to correct residual astigmatism after cataract surgery.

METHODS

LASIK was performed on 20 eyes of 20 patients with refractive myopic or mixed astigmatism (3.00 to 6.00 D) at least 1 year after extracapsular cataract extraction with posterior chamber intraocular lens implantation without complication. Each eye received bitoric LASIK with the Nidek EC-5000 excimer laser and the Automated Corneal Shaper microkeratome.

RESULTS

At 6 months after LASIK, mean refractive cylinder decreased from 4.64+/-0.63 D to 0.44+/-0.24 D (P<.001). Mean percent reduction of astigmatism was 90.4+/-5.0% (range 80% to 100%). Mean spherical equivalent refraction decreased from -2.19+/-0.88 D (range -1.00 to -3.88 D) to -0.32+/-0.34 D (range -1.25 to +0.38 D) (P<.001). Vector analysis showed that the mean amount of axis deviation was 0.7+/-1.2 degrees (range 0 degrees to 4.3 degrees) and the mean percent correction of preoperative astigmatism was 92.1+/-5.9% (range 85.6% to 108%). Eighty-five percent of all eyes had a mean spherical equivalent refraction and mean cylinder within +/-0.50 D of emmetropia. Change in spherical equivalent refraction and cylinder from 2 weeks to 6 months was < or = 0.50 D in 90% (18 eyes) and 95% (19 eyes), respectively. Spectacle-corrected visual acuity was not reduced in any eye. Diffuse lamellar keratitis occurred in three eyes (15%) after LASIK, and were treated successfully with eyedrops.

CONCLUSION

LASIK was an effective, predictable, stable, and safe procedure for correction of residual myopic or mixed astigmatism ranging from 3.00 to 6.00 D with a low spherical component after cataract surgery.

Long-term visual outcomes in the Cataract-Free Zone Project in Brazil

PURPOSE

To determine the long-term visual outcomes and causes of poor vision in the cataract population in Brazil treated in the Cataract-Free Zone Project.

METHODS

Project A subjects (62 patients) were recruited in Taquaritinga, SP, 26 months after surgery. Project B subjects (34 patients) were recruited in São João da Boa Vista, SP, 43 months after surgery. All patients underwent visual screening and eye examination (examination 1). They were classified according to visual acuity in the operated eye and the causes of poor vision were diagnosed and referred for treatment. The results of these interventions were collected (examination 2) and analysed by Chi-square test.

RESULTS

At examination 1 in project A, 47 of 62 patients (75.6%) had visual acuity < or = 20/100. The main causes of poor vision were refractive error (31.9%) and posterior capsule opacification (17.0%), with or without refractive error. At examination 1 in project B, 22 of 34 patients (64.7%) had visual acuity < or = 20/100. The main causes of poor vision were again posterior capsule opacification (50.0%) and refractive error (9.0%). After posterior capsulotomy with Nd:YAG laser and prescription of new corrective eyeglasses, visual acuity = 20/80 was obtained in 64.5% of patients in project A (OR = 0.18, CI = 0.07-0.41) and 70.5% of patients in project B (OR = 0.19, CI = 0.06-0.60) at examination 2. The causes of blindness in the remaining patients were identified.

CONCLUSION

This type of project is effective in reducing blindness caused by cataracts in developing countries. However, long-term scheduled follow-up of operated patients is an effective means of avoiding consecutive blindness resulting from secondary cataracts and refractive changes.

The Swedish National Cataract Register: A 9-year review

The Swedish National Cataract Register (NCR) has been collecting data on cataract extractions in Sweden since 1992. This unique national database now contains data pertaining to more than 400 000 operations, representing 93.4% of all operations performed nationwide during 1992-2000. Clinic participation in the NCR is voluntary. Tests have shown NCR data to be extremely reliable, while the participation of nearly all providers of cataract surgery in Sweden makes the data highly representative of cataract surgery throughout the country. The NCR collects pre- and per-operative data for every cataract extraction performed at participating clinics. Surgical outcome data and data about patients' self-assessed visual function is collected in approximately 10% of cases. Since 1998, all cases of suspected postoperative endophthalmitis have also been reported to the NCR. The rate of surgery has increased from 4.47 to 7.26 per 1000 inhabitants during the period. Female subjects have constituted about 66% of all operated subjects each year and the mean age of patients has slowly increased from 75.2 to 76.1 years. Average pre-operative visual acuity has improved each year. Second eye surgery has increased from 28.5% to 36.8% of all surgeries. Phacoemulsification has reached 98% as type of surgery (in 2000) and 92.7% of all intraocular lenses are foldable. Surgical outcome has improved by achieving a final refraction closer to the target refraction and less surgically induced astigmatism. The positive impact of cataract surgery in very elderly people has been demonstrated, as has the positive effect of second eye surgery, especially in young subjects. The NCR has served to enhance knowledge about trends and results of cataract surgery in Sweden. This review article describes some of the activities carried out and their results.

1998 European Cataract Outcome Study: report from the European Cataract Outcome Study Group

PURPOSE

To collect clinical data on cataract surgery to allow participating surgeons to compare their performance with that of their colleagues in an anonymous manner.

SETTING

Surgeons from 31 surgical units providing cataract surgery in 13 European countries.

METHODS

Every patient at each participating unit having surgery during 1 study month was evaluated. Data were reported to the coordinating center at the time of surgery and at the final examination. When the study was closed 6 months after surgery, all participants were provided with the outcomes from their own patients so they could compare them with outcomes from other centers.

RESULTS

The study included preoperative and intraoperative data on 2950 patients. Complete follow-up data were available for 2731 patients. The surgical audit included surgically induced astigmatism, proximity of target refraction, and the frequency of major complications. For each variable, a large variation in outcome between participating centers was found. Most centers had results both above and below average for different variables.

CONCLUSION

Cataract surgery data collected from 31 units in 13 European countries allowed participants to compare their performance with that of their colleagues in an anonymous manner. Significant variation was found in the outcomes among the units, with many units reporting results above and below the averages.

Older age as risk factor for deviation from emmetropia in pseudophakia

PURPOSE

To find risk factors for deviation from emmetropia after cataract surgery in clinical practice.

METHODS

We evaluated the refractive outcome in 106 patients who had underone phacoemulsification and in-the-bag IOL placement 115 +/- 10 days after surgery. Postoperative optical correction and refractive error (diopters of spherical equivalent--ED) were related to age and sex, pre-operative axial length and keratometric diopter power, and operative incision technique.

RESULTS

Emmetropia was achieved in 15% of cases; 65% of eyes needed a myopic correction, averaging = 0.46 +/- 0.91 ED. The refractive error was 0.74 +/- 0.61 ED (< or = 1 ED in 77% of cases, < or = 2 ED in 97%). Both optical correction and refractive error were correlated to older age at the time of surgery (p=0.002 and p=0.001, respectively). Astigmatism appeared greater in clear-cornea incision than in limbar incision cases (p=0.05).

CONCLUSIONS

The higher refractive error in patients aged over 73 years suggests that age may be a risk factor for deviation from emmetropia after cataract surgery.

Laser in situ Keratomileusis to Correct Residual Myopia After Cataract Surgery

PURPOSE

To evaluate the effectiveness, predictability, and safety of laser in situ keratomileusis (LASIK) for correcting residual myopia after cataract surgery with intraocular lens implantation.

METHODS

Twenty-two eyes of 22 patients underwent LASIK for the correction of residual myopia after cataract surgery. LASIK was carried out using the Chiron Automated Corneal Shaper and the NIDEK EC-5000 excimer laser. In all eyes, the follow-up was 12 months.

RESULTS

Before LASIK, 1 eye (4.5%) had an uncorrected visual acuity of 0.5 or better; 12 months after LASIK, 10 eyes (45.4%) achieved this level of visual acuity and 0 eyes achieved 1.00 or better. Before LASIK, mean refraction was -2.90 +/- 1.80 D; 12 months after LASIK it decreased significantly to 0.40 +/- 0.60 D (P < .01). In 18 eyes (81.8%) at 12 months after LASIK, spherical equivalent refraction was within +/-1.00 D of emmetropia; 11 eyes (50%) were within 0.50 D. No vision-threatening complications occurred.

CONCLUSION

LASIK with the Automated Corneal Shaper and Nidek EC-5000 excimer laser was an effective, predictable, stable, and safe procedure for correcting residual myopia after cataract surgery. No intraocular lens or cataract incision related complications occurred when LASIK was performed at least 3 months after phacoemulsification.

Retinal detachment in myopic eyes after photorefractive keratectomy

PURPOSE

To analyze the incidence and characteristics of retinal detachment (RD) in myopic patients who had photorefractive keratectomy (PRK).

SETTING

Universidad Miguel Hernández, Instituto Oftalmológico de Alicante, Alicante, Spain.

METHODS

The incidence of RD in 5936 consecutive eyes that had PRK to correct myopia was studied. Mean follow-up was 38.5 months +/- 17.4 (SD).

RESULTS

Retinal detachment occurred in 5 eyes (0.08%); 2 in women and 3 in men. The mean interval between PRK and RD was 21. 00 +/- 15.89 months (range 9 to 48 months). The mean best corrected visual acuity (BCVA) after PRK and before RD development was 20/81 (range 20/200 to 20/25). After RD repair, the mean BCVA was 20/460 (range 20/2000 to 20/29). In 4 of the 5 eyes, BCVA after RD was within 1 line of the preoperative value; in 1 eye, it decreased from 20/40 to 20/2000. The mean spherical equivalent (SE) before RD treatment was -1.35 +/- 1.08 diopters (D) (range 0 to -3.00 D) and after RD treatment, -2.95 +/- 0.83 D (range -2.00 to -4.00 D). Differences between SE before and after RD treatment were statistically significant (P =.01, paired Student t test).

CONCLUSIONS

The incidence of RD after PRK to correct myopia was 0.08%. In 4 of 5 eyes, there was little or no visual loss; but in the group as a whole, there was a significant increase in myopic SE.

Photorefractive keratectomy for residual myopia after cataract surgery

PURPOSE

To evaluate the effectiveness, predictability, and safety of photorefractive keratectomy (PRK) for correcting residual myopia and myopic astigmatism after cataract surgery with intraocular lens implantation.

SETTING

Refractive Surgery and Cornea Unit, Instituto Oftalmológico de Alicante, Alicante, Spain.

METHODS

Thirty consecutive eyes (30 patients) had PRK for residual myopia after cataract surgery. Surface PRK with a VISX Twenty-Twenty excimer laser was used in all patients. Follow-up was 1 year.

RESULTS

Before PRK, no eye had an uncorrected visual acuity (UCVA) of 20/40 or better. Twelve months after PRK, 16 eyes (53.33%) had a UCVA of 20/40 or better. After PRK, best corrected visual acuity (BCVA) improved 1 line or more in 14 eyes (46.66%) over the preoperative values, and 15 eyes (50.00%) had the same BCVA as before PRK. Mean pre-PRK refraction of -5.00 diopters (D) +/- 2.50 (SD) decreased significantly to -0.25 +/- 0.50 D at 12 months (P < .001). At 12 months, the spherical equivalent was within +/- 1.00 D of emmetropia in 27 eyes (90.00%). No vision-threatening complications occurred.

CONCLUSION

Photorefractive keratectomy was an effective, predictable, and safe procedure for correcting residual myopia and myopic astigmatism after cataract surgery.

Per-operative retinoscopy as a predictor of final post-operative refraction

PURPOSE

To assess the accuracy of streak retinoscopy performed at the end of cataract surgery as a predictor of final post-operative error.

METHOD

Retinoscopy was performed on 68 patients as they lay on the operating table after routine cataract extraction and intraocular lens implantation. In each case the predicted post-operative refraction by biometry and the retinoscopy at the end of the operation were compared with the 6 week post-operative subjective refraction.

RESULTS

The retinoscopy had a mean difference of 0.6 D (standard deviation of 0.5 D). The post-operative refraction predicted by biometric measurements had a mean difference of 1.6 D (standard deviation 0.6 D). When corrected for systematic error, 8% of patients were found to have an error of greater than 2 D as predicted by pre-operative biometry. Prediction by retinoscopy made no error greater than 2 D. The accuracy in the retinoscopic prediction of post-operative refraction was significantly better than the biometry using the F-test (p = 0.001).

CONCLUSION

Retinoscopy at the end of cataract surgery may be a valuable tool to alert the surgeon to an unexpected refractive error. This would enable immediate intraocular lens exchange, if required.

Accuracy of IOL calculation in cataract surgery

The accuracy of IOL calculation using the SRK II formula was studied in 515 cataract extractions with posterior chamber IOLs. All excessively myopic patients (8 patients) and those where we had predicted an emmetropic postoperative result, from a consecutive series of 994 patients, were included. Preoperatively the patients were divided into different groups according to their refractive status and the mean postoperative refraction was calculated in each group. The mean postoperative refraction increased almost linearly with increasing myopic status. The emmetropic group achieved a mean postoperative refraction of -0.6 D, whilst in the most myopic group mean refraction was -1.8 D. We believe that the SRK II formula is inaccurate for myopic eyes, and that new formulas are needed, taking into account all those factors that make up the dioptric power of an eye.

Women and men--same eyes?

In ophthalmology, few studies have been designed to investigate possible differences between women and men in a consistent manner. Some evidence is, however, available showing significance male-female differences. The importance of gender in ophthalmological research is emphasized by focusing on some knowledge about sex differences in ocular components in relation to cataract surgery and on the influence of the female hormones on the cornea.