|Year : 2013 | Volume
| Issue : 3 | Page : 95-97
Myopic shift of sulcus suture-fixated posterior chamber intraocular lenses
Ya-Chi Huang, Chien-Chi Tseng, Chang-Ping Lin
Department of Ophthalmology, Changhua Christian Hospital, Changhua, Taiwan
|Date of Web Publication||22-Aug-2013|
Department of Ophthalmology, Changhua Christian Hospital, Number 135, Nan-Hsiao Street, Changhua City 500
Source of Support: None, Conflict of Interest: None
Purpose: The objective of this study is to evaluate the myopic shift in sulcus suture-fixated posterior chamber intraocular lenses (PC IOLs).
Methods: It was a retrospective study of patients diagnosed with lens subluxation or aphakia who received sulcus suture-fixated PC IOLs from 2004 to 2010. Preoperative visual acuity; axial length; predicted IOL power by the SRK-T, Hoffer-Q, and Holladay-1 formulas; predicted refraction; postoperative visual acuity; and postoperative refraction were recorded. Differences between postoperative refraction and predicted refraction for an in-the-bag lens were calculated for each patient.
Results: Twenty eyes from 16patients with sulcus suture-fixated PC IOLs were included inthe study. Another 18 eyes from 18 patientswithin-the-bag fixationofIOLwereassigned tothe controlgroup. Inastudygroup, the difference between postoperative spherical equivalent and predicted refraction was −1.66 ± 0.97 D. The simple linear regression suggests that the SRK-T formula provides a better calculation of IOL power than other formulas for sulcus suture fixation of PC IOL using our technique. A comparison of postoperative refraction shifts between the study and the control groups showed that the myopic shift was statistically significant in the study group (p < 0.001).
Conclusion: Sulcus suture-fixation of a PC IOL induces, on average, a 1.66 D myopic shift, which is equivalent to an IOL power of around 2 D. In order to prevent a postoperative hyperopia refraction, we suggest that IOL power should be reduced to 1 –1.5 D for performing sulcus fixation using our technique.
Keywords: myopic shift, posterior chamber intraocular lenses, suture fixation
|How to cite this article:|
Huang YC, Tseng CC, Lin CP. Myopic shift of sulcus suture-fixated posterior chamber intraocular lenses. Taiwan J Ophthalmol 2013;3:95-7
|How to cite this URL:|
Huang YC, Tseng CC, Lin CP. Myopic shift of sulcus suture-fixated posterior chamber intraocular lenses. Taiwan J Ophthalmol [serial online] 2013 [cited 2022 Jan 22];3:95-7. Available from: https://www.e-tjo.org/text.asp?2013/3/3/95/203882
| 1. Introduction|| |
During cataract surgery, capsular complications such as congenital cataract and lens anomalies, trauma-related aphakia, zonular dialysis, or posterior capsule rupture result in inadequate capsule support for posterior chamber intraocular lens (PC IOL) implantation. To overcome this situation, several alternative techniques have been developed for proper IOL implantation, including an angle-supported anterior chamber IOL, an iris-fixated anterior chamber IOL, and a sulcus suture-fixated PC IOL.
The sulcus suture-fixation of a PC IOL is a popular technique for patients lacking adequate capsule support. The technique that we have developed is easy to perform, avoids suture exposure, and provides good IOL centration and stability. However, because IOLs are located more anteriorly than the intended in-the-bag fixation, the postoperative refraction shows a myopic shift from the predicted value. The intent of this study is to evaluate refractive outcomes and find a suitable adjustment for the sulcus suture-fixated PC IOL using our technique.
| 2. Patients and methods|| |
This retrospective study was conducted in 2004–2012 involving 20 eyes from 16 patients who had received sulcus suture-fixated PC IOLs. They had Marfan syndrome with lens subluxation, lens dislocation, traumatic cataract, and complications of a cataract surgery resulting in an inadequate posterior capsule support. Another 18 eyes from 18 patients with in-the-bag fixation of IOL were assigned to a control group. Patients who had any history of a severe ocular trauma, glaucoma, vitreous hemorrhage, intraocular surgery other than cataract extraction, and any concurrent pathology of the eye that would affect the surgical results were excluded. After the surgery, patients were followed up regularly in our clinic for at least 6 months. All the operations were performed by the same doctor. We recorded preoperative visual acuity, axial length by contact A-scan biometry, predicted IOL power by the SRK-T formula, predicted refraction, postoperative visual acuity, and postoperative refraction. The spherical equivalent value was assessed at least 6 months after the procedure. Two IOLs, a Storz P366UV IOL and an Alcon CZ708D IOL, have been used in accordance with the hospital supply at the time of surgery. Both IOLs have an eyelet on the haptic. The Stroz IOL has an optic diameter of 6.5 mm and a total diameter of 13.4 mm. The optic and total diameters of Alcon IOL are 7.0 mm and 12.5 mm, respectively.
During the surgery, the operator might subjectively adjust various powers of the inserted IOL to avoid a refraction shift after surgery, but this may result in a shift of manifest refraction. The predicted refraction of the actually inserted IOLcalculated using the SRK-T formula would be chosen and compared with the manifest refraction. The differences were considered as the refraction shift. The Hoffer-Q and Holladay-1 formulas were also applied to verify our results. Correlations between the predicted and manifest refractions were calculated using a simple linear regression.
2.1. Surgical technique
All patients received sulcus suture-fixated PC IOLs. The surgical technique has been published previously and described brieflyas follows: (1) conjunctival peritomies from the 4 o’clock to the 8 o’clock positions at the upper limbus are created, and two 3 mm sclera incisions paralleling the limbus and center at the 3 o’clock and 9o’clock positions are made; (2) an CIF-4 needle with 10-0 prolene (Ethicon Inc. Somerville, New Jersey, USA) and a 25-gauge needle (BD PrecisionGlide™ Needles, Singapore) are inserted separately through the upper ends of the opposite scleral grooves, the 25-gauge needle is then withdrawn, and the CIF-4 needle is engaged in its barrel; (3) one 10-0 Prolene suture is extended from the 9 o’clock to the 3 o’clock incision, and the procedure is repeated at the lower end of the groove; (4) the corneoscleral wound is opened; the threads are retrieved with a hook or IOL forceps and cut into halves; (5) two threads are tied at each site to the haptic eyelets. The IOL is inserted and the corneoscleral wound is closed with a 10-0 nylon thread; and (6) threads tied at the IOL are pulled out and their two ends are tied together; the threads are trimmed exactly above the knot, which is buried spontaneously in the scleral groove.
2.2. Statistical analysis
Analyses were performed using a commercially available statistical package (SPSS version 19.0 for Windows; SPSS Inc. Chicago, IL, USA). Results were presented as mean ± standard deviation. Differences of refraction shifts between the study and control groups were evaluated with the Mann–Whitney U test; p < 0.05 was considered statistically significant.
| 3. Results|| |
Sixteen patients (11 males and 5 female), with sulcus suture-fixated PC IOLs in 20 eyes, were included in the study. However, two patients (2 eyes) were lost to follow-up after 6 months, so only 18 eyes from 14 patients were considered for the statistical analysis [Table 1]. The age of the patients ranged from 5 years to 85 years, with a mean of 45.6 ± 25.0 years. The mean axial length was 25.4 ± 2.2 mm and the mean inserted IOL power was 17.7 ± 4.7 D. The Stroz lenses were used in five eyes, and the Alcon lenses were used in 13 eyes. The mean predicted refraction calculated by the SRK-T formula was -0.35 ± 0.62 D and the mean postoperative spherical equivalent was -2.01 ± 1.04 D. Seventeen eyes had myopic shifts and one eye had a hyperopic shift. The difference between postoperative spherical equivalent and predicted refraction was -1.66 ± 0.97 D. Using the Hoffer-Qand Holladay-1 formulas, the difference between postoperative spherical equivalent and predicted refraction was -1.90 ± 1.20 D and -1.70 ± 1.10 D, respectively. The results of a simple linear regression showed that the SRK-T formula was better than the others for choosing a sulcus suture-fixated PC IOL(standard β ofthe SRK-T, Hoffer-Q Holladay-1 formulas: 0.409, 0.120, and 0.284, respectively; R-square of the SRK-T, Hoffer-Q, and Holladay-1 formulas: 0.168, 0.014, and 0.081, respectively; [Figure 1]).
|Figure 1: Regression and correlation between predicted refraction and spherical equivalent of manifest refraction.|
Click here to view
Eighteen patients (18 eyes) were included in the control group. The age of the patients ranged from 52 years to 83 years, with a mean of71.8 ± 8.07 years. The mean axial length was 23.7 ± 1.1 mm and the mean inserted IOL power was 21.1 ± 1.1 D. The mean predicted refraction calculated using the SRK-T formula was -0.41 ± 0.26 D and the mean postoperative spherical equivalent was -0.20 ± 0.73 D; the difference was 0.21 ± 0.70 D. Six eyes had myopia shifts, one eye had a hyperopia shift, and 11 eyes had emmetropia.
No significant differences were observed in the axial length and inserted IOL power between the study and control groups. When we compared postoperative refraction shifts between these two groups, the myopic shift was statistically significant in the study group (p < 0.001; p value by Mann–Whitney U test).
| 4. Discussion|| |
It is a general concept that sulcus-fixated IOL induces a myopic shift; various modifications have been suggested based on different calculation methods. Hayashi et al have demonstrated a 0.50 D reduction in the intended power for sulcus-fixated IOL. Bayramlar et al have suggested that when sulcus fixation is necessary, Poly-methylmethacrylate (PMMA) IOL power should be approximately 1.25–1.50 D less than the power for in-the-bag fixation. Suto et al measured the effective lens position of IOLs with sulcus fixation and, compared with that with in-the-bag fixations, found it to be 0.75 mm shorter using A-mode measurement and 0.62 mm shorter using back calculation from the theoretical formula. The change in an anterior chamber depth (ACD) was calculated to be 0.1 mm, recommended a 1.0 D reduction in the intended power for sulcus fixation.
In our study, we observed a myopic shift of -1.66 ± 0.94 D, which is equivalent to a 1 mm forward movement, compared to in-the-bag fixation. We fixed the IOL in a triangular shape, with one fixation point at the eyelet of the haptic and two fixation points on the sclera; this may cause a stronger tension to stretch the IOL forward than using only a single line with two fixation points. As a result, the myopia shift in our study is more than what has been reported in other studies. Ma et al stated that overtightening of a trans-scleral fixation suture could cause a greater anterior shift of the IOL optic than when it is properly tightened, and it may induce pupillary capture of the IOL optic; this study supports our assumption. The drawback of our study is that we did not measure ACD after IOL implantation, so the relation between ACD and the predicted refraction could not be surveyed.
In conclusion, our study has indicated that sulcus suture fixation of a PC IOL with our technique has induced a myopic shift of -1.66 D, equivalent to an IOL power of around 2 D. In order to prevent a residual hyperopia after the operation, we suggest that the IOL power should be reduced to around 1–1.5 D for performing sulcus fixation using our technique.
| References|| |
Lin CP, Tseng HY. Suture fixation technique for posterior chamber intraocular lenses. J Cataract Refract Surg
Bayramlar H, Hepsen IF, Yilmaz H. Myopic shift from the predicted refraction after sulcus fixation of PMMA posterior chamber intraocular lenses. Canad J Ophthalmol
Hayashi K, Hayashi H, Nakao F, Hayashi F. Intraocular lens tilt and decentration, anterior chamber depth and refractive error after trans-scleral suture fixation surgery. Ophthalmology
Suto C, Hori S, Fukuyama E, Akura J. Adjusting intraocular lens power for sulcus fixation. JCataract Refract Surg
Olsen T. Sources of error in intraocular lens power calculation. JCataract Refract Surg
Ma DJ, Choi HJ, Kim MK, Wee WR. Clinical comparison of ciliary sulcus and pars plana locations for posterior chamber intraocular lens transscleral fixation. J Cataract Refract Surg