Rotational Stability after Toric Implantable Collamer Lens Implantation

PURPOSE: To evaluate rotational stability of Toric Implantable Collamer Lens (ICL) implantation to correct myopic astigmatism. METHODS: We estimated the degree of Toric ICL rotation together with change in visual acuity and astigmatism in 118 eyes of 66 patients who underwent Toric ICL implantation and had a long-term mean follow-up period of 37 months. RESULTS: After Toric ICL implantation, 107 (91%) out of 118 eyes showed uncorrected visual acuity of 0.8 or better. The mean postoperative astigmatism decreased to -0.64 +/- 0.61 D from a mean preoperative astigmatism of -2.96 +/- 1.13 D. The mean axis change of Toric ICL was 2.4 +/- 3.8 degrees during follow-up period. Two (1.7%) out of 118 eyes showed the axis change of more than 10 degrees. These two eyes had a decrease in visual acuity, rotational axis change of 18 degrees and 30 degrees, respectively, and increases in astigmatism of 1.50 D and 1.00 D, respectively. The remaining 116 eyes (98.3%) showed excellent rotational stability without visual acuity decreasing Toric ICL rotation during the follow-up period. CONCLUSIONS: Toric ICL implantation to correct high myopia with astigmatism rarely has axis rotation and maintains excellent rotational stability for long-term follow-up.

Risk Factors for Cataract Formation after Implantable Collamer Lens Implantation: Over a Mean 7.5-Year Follow-Up Period

PURPOSE: To determine the risk factors and incidence of cataract formation over a long-term mean follow-up of 7.5 years after type V4 implantable collamer lens (ICL) implantation. METHODS: We analyzed the preoperative, 3-month postoperative, 3-year postoperative, and last follow-up data of 228 eyes (118 patients) with mean preoperative spherical equivalent of -12.7 D and minimum postoperative follow-up of 3 years. Additionally, we determined the risk factors for cataract formation and calculated the 10.3 year cumulative cataract formation rate and 10.3 year cumulative cataract surgery rate using a survival curve. RESULTS: After type V4 ICL implantation with minimum follow-up of 3 years, the calculated 10.3 year cumulative cataract formation rate was 20% and actual cataracts developed in 34 eyes (14.9%). The 10.3 year cumulative cataract surgery rate was 12% based on a survival curve and actual cataract surgery was performed in 12 eyes (5.3%). The risk factors for cataract formation were age (odds ratio [OR] = 1.10, p = 0.00), preoperative spherical equivalent (OR = 0.90, p = 0.00), crystalline lens thickness (OR = 9.54, p = 0.00), axial length (OR = 1.33, p = 0.00), 3 months postoperative vault (OR = 0.50, p = 0.03), and existence of peripheral touch between ICL optic margin and crystalline lens at last follow-up (OR = 7.84, p = 0.00). CONCLUSIONS: We suggest one of the main risk factors for cataract formation after ICL implantation is decreased central vault and peripheral touch between ICL optic margin and crystalline lens.

Comparison of LASIK Mode Ablation and PRK Mode Ablation in LASEK Using MEL-80 Excimer Laser

PURPOSE: We compared laser assisted in situ keratomileusis (LASIK) mode and photorefractive keratectomy (PRK) mode ablation methods in laser subepithelial keratomileusis (LASEK) surgery using the MEL-80 excimer laser. METHODS: All patients were followed up for a minimum of 1 year. The PRK mode group consisted of 46 eyes of 23 patients and the LASIK mode group consisted of 97 eyes of 56 patients. The central corneal thickness (CCT), ablation thickness, manifest refractive error and uncorrected visual acuity were compared preoperatively, 1 month and 1 year postoperatively. Spherical equivalent (SE) of cycloplegic refraction at postoperative 1 month and the uncorrected visual acuity (UCVA) ratios of 1.0 or better at postoperative 1 year were compared between the two groups to evaluate clinical efficacy. RESULTS: The SE of refractive error, CCT and target corneal ablation thickness of the two groups were not significantly different preoperatively. The PRK mode group obtained an actual ablation mean thickness of 82.8% of the target and the LASIK mode group obtained an actual ablation mean thickness of 94.1% of the target at postoperative 1 month. In each group, a statistically significant difference was observed between the actual corneal ablation thickness and target corneal ablation thickness. In the PRK mode group, the mean SE of postoperative 1 month cycloplegic refraction was +0.24 +/- 0.47 D and in the LASIK mode group, +0.87 +/- 0.54 D, indicating a statistically significant difference between the two groups. One year postoperatively, the UCVA ratios of 1.0 or better were 83% in the PRK mode group and 96% in the LASIK mode group, showing a statistically significant difference between the two groups. However, SE of manifest refractive error and CCT in the two groups were not statistically different at postoperative 1 year. CONCLUSIONS: The LASIK mode ablation method showed better results than the PRK mode ablation method in postoperative UCVA prognosis after LASEK surgery using the MEL-80 excimer laser.

Axial Length Change after Implantable Collamer Lens Implantation

PURPOSE: The axial length measurement is an important variable in calculating the intraocular lens (IOL) power in cataract surgery. In this study, the effects of the implantable collamer lens (ICL) on the axial length measurement were investigated. METHODS: The axial lengths of 141 eyes of 76 highly myopic patients were measured before ICL implantation and 1 month postoperatively using applanation A-scan ultrasound. RESULTS: The measured axial lengths before ICL implantation and 1 month after the surgery were 28.03 +/- 1.91 mm and 28.08 +/- 1.86 mm respectively, with a statistically significant difference of 0.05 mm (p = 0.036). These 2 values showed a high correlation (R2 = 0.9829, p < 0.0001). CONCLUSIONS: Even though the axial length after ICL implantation significantly increased, the 0.05 mm change was too small to influence the determination of the IOL diopters in cataract surgery. Therefore, ICL implantation history may be reflected when measuring the axial length for the IOL power calculation in cataract surgery, but the axial length measured immediately before the cataract surgery may be used to calculate the IOL power regardless of the ICL implantation history.

Corneal Endothelial Cell Changes after LASEK and M-LASEK

PURPOSE: In this study we evaluated the changes in the corneal endothelial cells before and after the operation among myopes in the M-LASEK group, on whom 0.02% mitomycin C (MMC) was used and in the LASEK group, on whom MMC was not used. METHODS: The corneal endothelial cell analysis was performed in 104 eyes of 57 subjects in the LASEK group and in 86 eyes of 48 subjects in the M-LASEK group before the operation, and 3 months and 12 months postoperatively. RESULTS: There were no statistically significant differences in the corneal endothelial cell density (CD), the cell area coefficient of variance (CV), and hexagonal cell rate (6A) between the 2 groups before the operation, and 3 months and 12 months postoperatively (p > 0.05). In the LASEK group, there were no statistically significant differences (p > 0.05) in CD when the numerical values before the operation and 3 months and 12 months after the operation were compared, but there were statistically significant differences in CV and 6A when comparing before the operation and 12 months postoperatively (p = 0.001, p = 0.034, respectively). In the M-LASEK group, there was a 2.8% statistically significant decrease (p = 0.004) in CD when the numerical values before the operation and 3 months after the operation were compared, but there were no statistically significant difference (p > 0.05) when the numerical values before the operation and 12 months after the operation were compared. In addition, there were no statistically significant differences (p > 0.05) in CV and 6A when the numerical values before the operation and 3 months and 12 months after the operation were compared. CONCLUSIONS: M-LASEK, contrary to LASEK, showed statistically significant differences in CD in short-term results such as 3 months postoperatively, but in long-term observation such as 12 months postoperatively, both groups showed no statistically significant differences.

The Safety of 250 micrometer Residual Stromal Bed in Preventing Keratectasia after Laser in situ Keratomileusis (LASIK)

To determine if the residual corneal stromal bed of 250 micrometer is enough to prevent iatrogenic keratectasia in laser in situ keratomileusis (LASIK), we studied 958 patients who underwent LASIK from April 2000 to October 2003 retrospectively. The estimated probabilities of the residual stromal bed, that was less than 250 micrometer, were calculated using the published flap thickness data of Moria C&B microkeratome. Then we calculated the ratio of the real incidence of keratectasia to the expected the percentage of the patients with less than 250 micrometer residual stromal bed in our study. Using the LASIK flap thickness data of Miranda, Kezirian and Nagy, the expected probabilities that the residual stroma would be less than 250 micrometer were 8.8%, 4.3% and 1.5% of the 1,916 eyes respectively, while keratectasia developed in both eyes (0.1%) of 1 patient in our study. The estimated ratio of the keratectatic eyes to eyes with less than 250 micrometer stromal bed were 1.2-6.9%. Compared to the number of eyes with residual stromal thickness less than 250 micrometer, the incidence of keratectasia was relatively low. The residual stromal bed thickness of more than 250 micrometer may possibly be safe, but further observations for long period are necessary.

Peripheral Retinal Lesions Observed after Preoperative Evaluation for LASIK

PURPOSE: We estimated the incidence of retinal lesions at preoperative evaluation of retina for LASIK and investigate its clinical importance. METHODS: We estimated retrospectively the incidence of retinal lesions of the patients who visited our hospital with the purpose of correction of refractive error. The examination of retina upto periphery was done preoperatively. RESULTS: The mean spherical value and axial length were -6.5 +/- 3.4 diopters (range -26.0 ~ +17.0) and 25.4 +/- 2.0mm (range 15.7 ~ 34.5), respectively. The retinal lesions were found in 189 eyes of 139 persons (12.4%). Among them degenerative changes were found in 48 eyes of 34 persons, chorioretinal scars in 7 eyes of 7 persons, pigmented lesions in 28 eyes of 24 persons, and miscellaneous lesions in 106 eyes of 74 persons. There was a significant increase of spherical value and axial length in the group with retinal lesions -7.9 +/- 4.5 diopters (range -26.00 ~ -2.25), 26.5 +/- 2.3mm (range 23.1 ~ 34.5) compared to that without retinal lesions -6.1 +/- 3.4 diopters (range -25.00 ~ 17.00), 25.4 +/- 2.1mm (range 15.7 ~ 35.4). And the incidence of degenerative change and retinal tear was significantly increased in moderate myopes more than -4 diopters. CONCLUSIONS: LASIK is relatively a kind of safe refractive surgery, but to prevent the unexpected postoperative retinal complications, it is essential to thoroughly examine the retina upto periphery before surgery.

The Efficacy and Safety of Dream Lens(TM) in School Children

PURPOSE: This project was designed to study the effectiveness and safety of Dream lens(TM) (OK B+ series lenses, Contex, USA) in correcting myopia in a population of school children, under 13 years old. METHODS: Twenty-three school children aged 7 to 13 years followed over a 3-month period were fitted with lenses in the Vision Eye Center from September 2002 to March 2003. Slit lamp examination, uncorrected visual acuity, autorefraction and autokeratometry by Canon RK-5 and topography were measured at baseline and at 1week, 1 month, and 3 months after the lenses were worn. RESULTS: The mean baseline autorefraction was -2.54 +/- 1.00 diopters (range: -0.63~-4.00) and baseline uncorrected visual acuity over 0.5 was 11.1% and over 0.8 was 0%. Vision correction of over 0.8 was found in 80% of the cases in the first 1 week, 78% at 1 month, 91% at 3 months with the most rapid improvement occurring during the first 1 week. Superficial punctate keratitis occurred in 4 of 45 eyes, but there was no other pathologic problem. CONCLUSIONS: Dream lens is an effective and safe means of temporarily reducing myopia in a certain range of myopic patients; however, further studies are needed to determine the long-term effects on the eye health.

Amniotic Membrane Transplantation for Tube Eerosion after Ahmed Glaucoma Valve Implant Surgery: Two Cases

PURPOSE: We report two cases of tube erosion after Ahmed valve implantation, treated with Amniotic Membrane Transplantation. METHODS: Erosion of conjunctiva over tube occured in 2 female patients with Ahmed valve implantation. They were treated with pericardial patch grafts and conjunctival free graft with amniotic membrane epithelial side up transplantation. RESULTS: No recurrent tube erosion has been found since then. Intraocular pressure has been maintained well for 12-14 months of follow-up. CONCLUSIONS: In cases of tube erosion, additional amniotic membrane transplantation can improve surgical success.

Refraction before and after LASIK

PURPOSE: It is important to know the accurate refractive error of the patients before LASIK because the amount of ablation is determined by that. We analyzed whether there are differences among the preoperative and postoperative results of cycloplegic retinoscopy (CR), module setting value, and autorefraction with and without cycloplegia (ACR, AMR). METHODS: The manifest and cycloplegic refractions of 104 eyes of 104 patients who underwent LASIK from February 2001 to July 2001 were reviewed. The preoperative and postoperative cycloplegic refraction, autorefraction by Canon RK-5, and module setting value were analyzed. RESULTS: In comparison of the preoperative values, AMR showed myopic shift compared to CR, module setting, and ACR (p<.001). ACR showed hyperopic shift compared to CR (p<0.001). The module setting showed myopic shift compared to CR, but it was not statistically significant. Postoperative mean spherical equivalent was 0.04 +/- 0.67D(range: -1.75 ~ +1.5). In comparison of the postoperative results, ACR showed hyperopic shift compared to CR (p<0.001) and AMR showed myopic shift compared to CR (p<0.001). CONCLUSIONS: As there is a difference between autorefraction and cycloplegic refraction, it is inappropriate to decide the amount of ablation only by one method. Hence when LASIK or LASIK retreatment is planned, cycloplegic refraction as well as autorefraction is necessary.

Intraocular Lens Power Calculation for Cataract Surgery in Patients who had Previous Refractive Surgery (RK 1 Case, PRK 3 Cases, LASIK 1 Case)

The purpose of this study is to assess the accuracy of IOL power calculations using clinical history method in patients who undergo cataract surgery after previous PRK, RK, or LASIK.Five eyes of 3 patients who had previous PRK, RK, or LASIK underwent phacoemulsifications with IOL implantation.We calculated IOL power for target refractive error using clinical history method.We compared postoperative refractive error to target refractive error at 3 months after cataract surgery.In the first case (RK (od)& PRK (os)), there was 3.50 diopter undercorrection on the right eye and IOL was exchanged.And target refractive error was achieved on the left eye.In the second case (LASIK patient)there was 1.00 diopter undercorrection.In the third case (PRK (ou)), right eye achieved 0.75 diopter undercorrection and left eye achieved 0.50 diopter overcorrection.The types of cataract were nuclear sclerotic in 3 cases and anterior subcapsular in 2 cases.To determine the exact IOL power after refractive surgery, using clinical history method would be good alternative in these patients.

Clinical Experience with the Ahmed Glaucoma Valve

The purpose of this study is to assess clinical outcomes of the patients who underwent Ahmed glaucoma valve implantation. Twelve eyes of 11 patients underwent Ahmed valve implantation for intractable glaucoma unresponsive to conventional management from March 1997 to April 1998 at department of ophthalmology of Kangbuk Samsung Hospital and had minimum follow-up of three months. Success(survival)was defined as an intraocular pressure(IOP)between 6 and 21 mmHg and with no additional glaucoma surgery, phthisis, implant removal, or loss of light perception. The mean follow-up period was 8 months(range, 3-17 months). There were 7 neovascular glaucomas, 3 secondary angle close glaucomas and 2 juvenile open angle glaucomas. The postoperative 1 year cumulative survival rate (Kaplan-Meier survival analysis)was 83. 3%. High survival rate was shown in secondary angle close glaucoma and JOAG(100%). The survival rate was not affected by sex, age, preoperative IOP, preoperative diagnosis, or number of preoperative glaucoma medications. There was failure in 2 eyes. One eye had qualified success by secondary Ahmed valve implantation. In the other eye, the tube in anterior chamber was too short and was plugged by blood clot and inflammatory membrane. This patient could not be reoperated due to poor general condition. Complications were hyphema and hypotony, and they were well controlled. Ahmed valve implantation in patients with intractable glaucoma may offer a better chance of surgical success.

Management of Three Cases of Decentration after Laser In Situ Keratomileusis

Four hundred one eyes of 219 patients underwent laser in situ keratomileusis(LASIK) at Kangbuk Samsung Hospital from March 1997 to June 1998. Of those, 33 eyes of 25 patients were retreated. Among 33 eyes, we presumed that 3 eyes had decreased visual quality mainly associated with decentration. The mean reftactive error and the amount of decentration of 3 eyes were -1.00 diopter and 2.66mm. After retreatment of these 3 eyes, uncorrected and corrected visual acuity, and visual quality were improved by correction of residual refractive errors, even though the amount of decentration was the same. In cases of decreased visual quality which is suspected to be mainly associated with decentration, we need differentiation between decentration and residual rfractive errors as causes of decreased visual quality. Even though decentration is suspected as a cause of decreased visual quality, visual quality can be improved by correction of residual refractive errors.

Management of Three Cases of Decentration after Laser In Situ Keratomileusis

Four hundred one eyes of 219 patients underwent laser in situ keratomileusis(LASIK) at Kangbuk Samsung Hospital from March 1997 to June 1998. Of those, 33 eyes of 25 patients were retreated. Among 33 eyes, we presumed that 3 eyes had decreased visual quality mainly associated with decentration. The mean reftactive error and the amount of decentration of 3 eyes were -1.00 diopter and 2.66mm. After retreatment of these 3 eyes, uncorrected and corrected visual acuity, and visual quality were improved by correction of residual refractive errors, even though the amount of decentration was the same. In cases of decreased visual quality which is suspected to be mainly associated with decentration, we need differentiation between decentration and residual rfractive errors as causes of decreased visual quality. Even though decentration is suspected as a cause of decreased visual quality, visual quality can be improved by correction of residual refractive errors.