Intraocular lens power calculation for lens exchange.

PURPOSE: To examine patients who had intraocular lens (IOL) exchange for large postoperative refractive errors and determine the factors that contributed to the error in IOL power calculation. SETTING: Thirteen affiliated hospitals in Japan. METHODS: This study comprised 34 cases that required IOL exchange because of large refractive errors after primary lens implantation. Patients with intraoperative complications were excluded from the study. The potential contribution of axial length, corneal refractive power, IOL manufacturer, and IOL fixation to errors in the predicted power was examined retrospectively. Axial length was calculated by the SRK/T and Holladay formulas using refraction after primary IOL implantation. RESULTS: There was no statistical difference between the corneal refractive power before and after cataract surgery. The axial lengths calculated using the SRK/T and Holladay formulas were longer than the ultrasonic axial lengths in 24 and 23 cases, respectively. Using IOLs from the same manufacturer for both primary implantation and exchange reduced the error in predicted refraction. CONCLUSION: Axial length and IOL manufacturer were important factors in predicting refraction power in eyes requiring IOL exchange.

Intraocular lens implantation in a child with monocular cataract and anterior persistent hyperplastic primary vitreous.

A 3-year-old girl had phacoemulsification during which the presence of anterior persistent hyperplastic primary vitreous (PHPV) was discovered. Visual rehabilitation comprised contact lens use for 1 year. However, visual acuity deteriorated gradually because of secondary cataract formation. In a second surgery 1 year after the first, the posterior capsule was incised, followed by an anterior vitrectomy and intraocular lens implantation. At the last follow-up 6 months after the second surgery, there was no evidence of ocular complications and best corrected visual acuity was 0.6.

A case of insulin dependent diabetes mellitus following systemic treatment for Vogt-Koyanagi-Harada syndrome.

A 29-year-old man developed acute visual impairment, cough, and headache. Both eyes showed serous retinal detachment in the posterior fundus. Fluorescein angiography showed subretinal pooling of fluorescein in the late phase. A diagnosis of Vogt-Koyanagi-Harada (VKH) syndrome was made based on clinical features. Treatment with systemic corticosteroids resulted in improvement of uveitis and both eyes showed "sunset glow" fundus 11 months later. Insulin-dependent diabetes mellitus (IDDM) developed 13 months later (3 months after systemic corticosteroid therapy). Despite treatment with insulin, glycemic control was poor. Human leukocyte antigen (HLA) typing showed HLADR9 and DQB 1*0303 related to IDDM. We postulated that treatment with corticosteroids precipitated IDDM, a yet unknown common autoimmune mechanism might have caused IDDM and VKH, or both conditions occurred coincidentally.

Diplopia after cataract surgery.

PURPOSE: To evaluate the cause of diplopia after cataract surgery. SETTING: Cataract surgery at 7 hospitals and examination of diplopia at a central eye hospital. METHODS: This study comprised 18 eyes of 17 patients with diplopia that developed after cataract surgery in which retrobulbar anesthesia was used. The Hess screen test was done to diagnose oculomotor dysfunction. RESULTS: Several cases showed superior or inferior deviation of the globe, but most patients had nonuniform disturbances of eye movement. Examination of 3 patients by the Hess chart within 1 week after surgery showed paralysis of eye muscles but an overaction at a later stage, evident by reversal of eye position 1 month later. Surgery for strabismus was performed in 6 cases. One case with diplopia improved spontaneously 3 months after cataract surgery and achieved good alignment. CONCLUSIONS: The Hess screen test was useful for comparing changes in oculomotor function before and after surgery. Oculomotor dysfunction after cataract surgery may be caused directly by traumatic injury during administration of anesthesia or surgery using bridle sutures or indirectly from sensitivity to anesthetic agents.

[Accuracy of intraocular power calculation formulas].

PURPOSE: We examined the accuracy of intraocular lens power calculation formulas, with special emphasis on the prediction of refraction in different axial lengths. MATERIAL AND METHODS: 786 cases were subdivided into four groups based on the axial length (short axial length < 22.0 mm, normal axial length = 22-24.4 mm, mid-range axial length = 24.5-26.9 mm and long axial length > 27 mm). Seven different formulas (Holladay, SRK, SRK II, SRK/T, S-SRK, M-SRK, L-SRK) were tested for their accuracy in predicting post-operative refraction. RESULT: The best results were obtained using the S-SRK formula in the short axial length group (n = 114), The SRK and Holladay formulas in the normal axial length group (n = 278). The Holladay and SRK/T formulas in the mid-range axial length group (n = 135), and the SRK/T and L-SRK in the long axial length group (n = 259). CONCLUSION: Our results emphasize the importance of using an intraocular lens formula specific for each range of axial length when calculating the predicted refraction.

Rad52 associates with RPA and functions with rad55 and rad57 to assemble meiotic recombination complexes.

We show that the Saccharomyces cerevisiae recombination protein Rad52 and the single-strand DNA-binding protein RPA assemble into cytologically detectable subnuclear complexes (foci) during meiotic recombination. Immunostaining shows extensive colocalization of Rad52 and RPA and more limited colocalization of Rad52 with the strand exchange protein Rad51. Rad52 and RPA foci are distinct from those formed by Rad51, and its meiosis-specific relative Dmc1, in that they are also detected in meiosis during replication. In addition, RPA foci are observed during mitotic S phase. Double-strand breaks (DSBs) promote formation of RPA, Rad52, and Rad51 foci. Mutants that lack Spo11, a protein required for DSB formation, are defective in focus formation, and this defect is suppressed by ionizing radiation in a dose-dependent manner. DSBs are not sufficient for the appearance of Rad51 foci; Rad52, Rad55, and Rad57 are also required supporting a model in which these three proteins promote meiotic recombination by promoting the assembly of strand exchange complexes.

Analysis of preoperative factors predictive of visual acuity in axial myopia.

PURPOSE: To identify the factors predicting visual acuity after cataract surgery in patients with high myopia. SETTING: Departments of Ophthalmology, Showa University School of Medicine and Showa University Fujigaoka Hospital, Kanagawa, Japan. METHODS: Stepwise regression analysis was used to identify the factors determining the visual acuity in 940 eyes with an axial length of 27.0 mm or longer having cataract surgery. Using a formula derived from the stepwise regression analysis, the predicted postoperative visual acuity was compared with the actual value measured in another group of 104 eyes. RESULTS: Five factors were identified to significantly determine postoperative visual acuity: axial length, age, corneal opacity, refractive power of the cornea, and history of retinal detachment surgery. There was a significant relationship between predicted and actual postoperative visual acuities (r = .51, P < .001). Postoperative visual acuity was similar in 63% of cases. CONCLUSION: The results showed that at least five factors determine visual acuity after cataract surgery in patients with high myopia.

Intraocular lens power calculation for microphthalmos.

PURPOSE: To evaluate the refractive results and accuracy of intraocular lens (IOL) power calculation formulas in eyes with microphthalmos. SETTING: Department of Ophthalmology, Showa University Hospital, Tokyo, Japan. METHODS: The accuracy of IOL power calculated using the SRK, SRK II, S-SRK, SRK/T, Holladay, and Hoffer Q formulas was evaluated in six eyes with axial lengths less than 19.0 mm. RESULTS: Postoperative measurement of refraction showed a tendency toward hypermetropia compared with the refraction predicted by each formula. The best predicted refraction was calculated using the SRK/T formula. The tendency for hyperopic estimation was related to the axial length, particularly in eyes with a shorter axial length. However, there was no relationship between the refractive power of the cornea and the error in the predicted refraction by the SRK/T formula. Two eyes with an IOL power of 30.0 diopters (D) had severe hypermetropia. CONCLUSION: Theoretical formulas were more accurate than empirical ones in eyes with microphthalmos. The severe hypermetropia in the two eyes with a 30.0 D IOL indicates that such patients require a higher IOL power.

[Intraocular lens power calculation for short eye].

The accuracy of intraocular lens power calculation formulas for short eyes was examined. We examined 217 eyes with an axial length of shorter than 22.5 mm, with postoperative visual acuity of 0. 5 or more, and postoperative astigmatism of less than +/- 2D. Five formulas were tested for accuracy in prediction for postoperative refraction, the S-SRK, the SRK, the SRK II, the SRK/T, and the Binkhorst formulas. The best results were produced by the S-SRK formula which predicted 74% of the cases within +/- 1D error, if the axial length was shorter than 22 mm. The A-constant was also examined to study the effect of postoperative refraction. The A-constant takes into consideration the depth of the anterior chamber lens, so that the differences in depth would be influenced for short eyes rather than regular eyes in prediction. However, there was no significant difference among the different A-constant groups.

[An intraocular lens power calculation for high myopia].

The accuracy of intraocular lens power calculation formulas for the axial high myopia were examined, especially regarding the point of the predictive refraction. We examined 170 eyes with axial lengths of 27 mm or longer, with postoperative visual acuity of 0.5 or more, and postoperative astigmatism of less than +/- 2D. Five formulas were tested for accuracy in predicting postoperative refraction. They were the L-SRK, SRK, SRK II, SRK/T, and Binkhorst formulas. The SRK formula tended to predict less myopia than the actual postoperative refraction. The SRK II and Binkhorst formulas predicted more myopia than the actual postoperative refraction. The best results were produced by the L-SRK and SRK/T formulas. The accuracy of the L-SRK formula predictions were measured for each of the four myopic levels. The same was done for the SRK/T formula. For both formulas, there was no statistically significant difference in accuracy of prediction for the four myopic categories. The two formulas are considered to be useful for high myopic cases.

Preferred postoperative refraction after cataract surgery for high myopia.

Eighty-four patients (121 eyes) with high myopia who had cataract surgery and intraocular lens implantation completed a survey on preferred postoperative refraction. Forty-two percent of the sample reported that they were accustomed to removing their glasses to read a newspaper or book. These respondents were fitted with soft contact lenses and their refraction changed to 0 D, -3.00 D, and -5.00 D. Of the patients whose best corrected postoperative visual acuity was 20/40 or better (n = 63), 48% preferred the -3.00 D correction; 38%, the 0 D correction; and 14%, -5.00 D. Of those with a best corrected postoperative visual acuity worse than 20/200 (n = 8), 80% preferred the -5.00 D refraction, which allowed them to read close up. Most patients with phakic eyes and good visual acuity (n = 13) preferred the 0 D and -3.00 D corrections. Our results indicate that in patients with high myopia, it is important to take patient preference into account when selecting postoperative refraction.

[The retinal image of three multifocal intraocular lenses through an eye model].

Retinal images produced by two types of multifocal intraocular lenses (IOLs) were studied using an eye model. One of them was a refractive IOL with five zones, and the other was a diffractive lens. The IOLs were inserted into an eye model with a pupil diameter of 3 mm. The retinal plane of the eye model was observed microscopically. When the section of the IOL used for far vision was in focus, the retinal image of the refractive IOL was almost the same as that of the monofocal IOL, which was better than that of the diffractive IOL. When the near vision section of the IOL was in focus, the retinal image of the diffractive IOL had almost the same quality as the far section. The light rings produced when the multifocal IOLs were illuminated by a glare source were also examined. They showed that the diffractive IOL was stronger than the refractive IOL, but the monofocal was the smallest of the three.

Experimental study of small intraocular lenses using an eye model.

Contrast and glare tests were performed on small intraocular lenses (IOLs) using a new eye model, which was based on and about the same size as the Gullstrand eye model. Lenses with a small optic diameter were inserted and retinal images were observed under the operating microscope. Contrast and glare disability tests were done using the MCT-8000 contrast tester and the Miller-Nadler glare tester. No effect on contrast sensitivity attributable to glare was observed, but under severe glare light conditions a faint reflection around the circumference of the optic was found. Questionnaires from patients implanted with small optic IOLs confirmed that this phenomenon was similar to their symptoms.

Eye growth after cataract extraction and intraocular lens implantation in children.

We studied the effect of cataract extraction and intraocular lens (IOL) implantation (14 unilateral and 2 bilateral cases) on eye growth in 16 children. Visual acuity, refractive power, axial length, corneal curvature, and anterior chamber depth in both the operated and unoperated eyes were measured before and after surgery. The operated eyes tended to become myopic (maximum, -11.00 diopters). However, though the axial length of two eyes increased significantly after surgery, there was no significant difference between the postoperative increase in axial length in the operated and in the unoperated eyes. The anterior chambers of the unoperated eyes tended to be deeper. We suggest that the tendency to become myopic in the operated eyes occurred because, as axial length increases with growth, the proportion occupied by the vitreous body, ie, the part posterior to the IOL, also increases.

A new endoscope for ophthalmic microsurgery.

We present an endoscope designed for ophthalmic microsurgery. The handpiece contains a charge-coupled device, a solid-state imager (250,000 pixels), and a probe (either 0.89 or 1.5 mm in diameter), including the light guide. The light source is a halogen lamp. The clear views the instrument provides of the ciliary sulcus and ciliary body behind the iris make it useful in secondary posterior chamber intraocular lens implantation using the ciliary sulcus suturing technique, and in endolaser photocoagulation of the ciliary body in end-stage glaucoma. It also is useful in performing vitrectomy in cases in which visualization is difficult because of corneal opacification or fluid-gas exchange.

Modified SRK formula for axial myopia (24.5 mm < or = axial length < 27.0 mm).

When used for eyes with greater than average axial length (AXL), the SRK formula has been reported to have a tendency to yield more myopic refractions than those predicted. To further evaluate such findings, we studied 609 eyes with AXLs between 24.5 and 27.0 mm. Comparing the predicted with the actual refractions and calculating the range of errors, we found that the postoperative refractions were more myopic than predicted. Then, based on our evaluation of the relationship between the postoperative refractions and the powers of the implanted intraocular lenses (IOLs), we devised the following formula: R = 0.8 x (P - I) + 0.57 (P < .01) in which R = the postoperative refraction; P = the emmetropic IOL power; and I = the actual IOL power. Testing this modified SRK formula in 55 additional eyes, we found that the predicted postoperative refractions it yielded were more accurate than those calculated using five earlier formulas.

Long-term study of children with implanted intraocular lenses.

We studied children between five and 15 years of age who were implanted with intraocular lenses (IOLs). The subjects comprised eight cases of traumatic cataract, 11 of congenital cataract, and six of steroid cataract. The follow-up ranged from four months to nine and one half years. Twenty of the eyes studied achieved a postoperative visual acuity of equal to or better than 20/40. Binocular function was retained in most cases. Postoperative complications included seven cases of posterior iris synechia, three of iris capture, one of transitory elevated intraocular pressure, and one of cystoid macular edema. Corneal endothelial studies were normal in the eyes in which posterior chamber IOLs were implanted.

Sulcus fixation of posterior chamber lenses by transscleral sutures.

Sulcus fixation of posterior chamber lenses by transscleral sutures was performed in 23 cases. We used new techniques to be sure that the sulcus was pierced accurately and the suture was placed in the posterior chamber instead of the ruptured capsule. This paper describes these techniques and the clinical results of 23 cases.

Errors in IOL power calculations for axial high myopia.

We studied 115 eyes with axial lengths of 27 mm or more after implantation of a posterior chamber intraocular lens in order to determine discrepancies between the predicted refractions and the actual postoperative refractions. We then reviewed the three major variables used to predict refractions in these eyes--corneal curvature, anterior chamber depth, and axial length measurements--in an attempt to determine whether any of these variables were correlated with the discrepancies. We found that the main reason for postoperative refractive error was inaccurate measurements of preoperative axial length.

A simple modified SRK formula for severely myopic eyes.

We describe our modification of the most accurate intraocular lens power calculation formula currently used, the SRK formula, to improve the accuracy with which it can be used to calculate the power of IOLs that are implanted in severely myopic eyes, especially in those with exceptional axial length. This modified formula, which we call the L-SRK, is I = A - 2.5 L - 0.9 K - 1.69R - 1.69 (where I = the actual implanted IOL power; A = the A-constant; L = the axial length; K = the average keratometer reading; and R = the predicted postoperative refraction). The results achieved using this modified formula demonstrate its superior accuracy in calculating lens powers for severely myopic eyes.