Yukiko Kora

Long-term study of children with implanted intraocular lenses

ABSTRACT 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.

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.

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.

Sulcus fixation of posterior chamber lenses by transscleral sutures

ABSTRACT 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.

Intraocular lens implantation and high myopia

ABSTRACT We evaluated aphakia and pseudophakia in highly myopic patients whose axial lengths were 27 mm and over. Cataract surgery alone was performed on 99 eyes (aphakic group) and intraocular lens (IOL) implantation was performed on 84 eyes (pseudophakic group). The IOL power was determined by the SRK formula and ranged from + 9.0 to + 18.5 diopters (D). There was no statistical difference in postoperative complications between the aphakic and pseudophakic groups. The postoperative aphakic refractions ranged from + 9.5 D to ‐ 3.5 D, and the pseudophakic refractions, from + 2.5 D to ‐14.0 D. A visual acuity of 20/40 or better was achieved by 51% of aphakic patients and 63% of pseudophakic patients. A near visual acuity of 20/40 or better was achieved by 65% of pseudophakic patients. Seventy‐three pseudophakic eyes (87%) were not corrected or were corrected with minus diopter lenses. This confirmed our opinion that there was no need to correct them for near vision. According to a postoperative questionnaire, 67% of the pseudophakic patients did not need spectacles for near vision and 93% of patients could see comfortably for daily life. In view of these results, we feel that most myopic patients are good candidates for IOL implantation.

Preferred postoperative refraction after cataract surgery for high myopia

Abstract 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.

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.

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.

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 visuai 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.

Experimental study of small intraocular lenses using an eye model

ABSTRACT 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.