Muriël Doors

Use of Anterior Segment Optical Coherence Tomography to Study Corneal Changes After Collagen Cross-linking

PURPOSE To investigate the stromal demarcation line after corneal cross-linking using anterior segment optical coherence tomography (AS-OCT) and its influence on the short-term results of cross-linking in patients with progressive keratoconus. DESIGN Prospective, nonrandomized study. METHODS Twenty-nine eyes of 29 patients with progressive keratoconus (n = 28) or after laser in situ keratomileusis ectasia (n = 1) were included and treated with corneal cross-linking at our institution. Measurements at 1, 3, 6, and 12 months after corneal cross-linking were: refraction, best-corrected visual acuity (BCVA), tonometry, corneal topography, AS-OCT, specular microscopy, and aberrometry. Demarcation line depth was measured centrally, 2 mm temporally, and 2 mm nasally by two independent observers using AS-OCT and was correlated with clinical parameters. RESULTS The stromal demarcation line was visible with AS-OCT at 1 month after surgery in 28 of 29 eyes. Pairwise comparisons between the two observers of the AS-OCT measurements did not show a statistically significant difference. After an initial steepening of maximal keratometry values and a decrease in BCVA at 1 month after surgery (both with P < .012), no significant changes were found at 3, 6, and 12 months after surgery compared with before surgery. Refractive cylinder, topographic astigmatism, aberration values, endothelial cell density, and intraocular pressure remained stable during all postoperative visits. A deeper demarcation line depth was associated with a larger decrease in corneal thickness (r = -0.506; P = .012). CONCLUSIONS AS-OCT is a useful device to detect the stromal demarcation line after corneal cross-linking. At 3 to 12 months follow-up, all clinical parameters remained stable, indicating stabilization of the keratoconic disease.

Evaluation of the Lenstar LS 900 non-contact biometer.

Background/aims: Evaluation of the reproducibility of the Lenstar LS 900 non-contact biometer, and a comparison with the Visante anterior-segment optical coherence tomography (AS-OCT) and the IOLMaster. Methods: Central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), keratometry (K) values, corneal diameter (CD) and axial length (AL) were obtained in 38 healthy volunteers (76 eyes) to determine the reproducibility of the Lenstar. CCT, ACD, CD, K values and AL measurements measured with the Lenstar were compared with the AS-OCT and IOLMaster. Intraocular lens (IOL) power calculations were done to study the significance of the difference between AL measurements. Results: The reproducibility of the Lenstar was better than 0.9% for CCT, ACD, LT, K values and AL measurements. Although all correlations were highly significant (p<0.001), all comparisons showed a significant difference, except for the comparison of CD measurements using the Lenstar and IOLMaster (p = 0.175). The differences in IOL power calculations for an AL of 20, 25 and 30 mm with a mean difference between Lenstar and IOLMaster AL measurements of 0.03 mm, were 0.13 D, 0.10 D and 0.08 D, respectively. Conclusion: The reproducibility of the Lenstar was excellent. Small but significant differences exist between the Lenstar, Visante OCT and the IOLMaster. Therefore, measurements of the Lenstar, AS-OCT and IOLMaster are not interchangeable. Despite the significant difference between AL measurements, there is no clinically significant difference in the IOL power calculation results.

Value of optical coherence tomography for anterior segment surgery

&NA; Anterior segment optical coherence tomography (AS‐OCT) is an important new noncontact imaging technology that uses a 1310 nm super luminescent diode. It can be used to assess anterior chamber biometry, corneal thickness, lens thickness, and angle configuration; to visualize pathological processes; to evaluate postsurgical anatomy and posttraumatic eyes; and to image phakic intraocular lenses and intracorneal ring segments. Because it is a noncontact technique, it can also be used intraoperatively, which could be useful during trabeculectomy and after deep anterior lamellar keratoplasty to detect abnormalities in the cornea and interface. A disadvantage of AS‐OCT is its inability to penetrate the iris pigment epithelium, which makes it impossible to evaluate the structures behind the iris. The most frequently used devices are time‐domain AS‐OCT, but new Fourier‐domain OCT devices, which have faster image acquisition and higher resolution, are currently under investigation. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Comparison of central corneal thickness and anterior chamber depth measurements using three imaging technologies in normal eyes and after phakic intraocular lens implantation.

BackgroundThe repeatability and interchangeability of imaging devices measuring central corneal thickness (CCT) and anterior chamber depth (ACD) are important in the assessment of patients considering refractive surgery. The purpose of this study was to investigate the agreement of CCT and ACD measurements using three imaging technologies in healthy eyes and in eyes after phakic intraocular lens implantation (pIOL).MethodsIn this comparative study, CCT and ACD were measured using anterior segment optical coherence tomography (AS-OCT), Orbscan II, and Pentacam in 33 healthy volunteers (66 eyes) and 22 patients (42 eyes) after pIOL implantation. Intraobserver repeatability was evaluated for all three devices in the healthy volunteer group.ResultsPairwise comparison of CCT measurements showed significant differences between all devices (P < 0.001), except for the AS-OCT and Orbscan II in the healthy volunteer group (P = 0.422) and the Orbscan II and Pentacam in the pIOL group (P = 0.214). ACD measurements demonstrated significant differences between all pairwise comparisons in both groups (P ≤ 0.001). Intraobserver reliability was high for CCT and ACD measurements in the healthy volunteer group, with coefficients of variation ranging from 0.6% to 1.2% and 0.4% to 0.5% respectively.ConclusionsCCT and ACD measurements using AS-OCT, Orbscan II, and Pentacam demonstrated high intraobserver reliability. However, these devices should not be used interchangeably for measurements of CCT and ACD in healthy subject and patients after pIOL implantation.

Influence of anterior chamber morphometrics on endothelial cell changes after phakic intraocular lens implantation

PURPOSE: To analyze the position of iris‐fixated phakic intraocular lenses (pIOLs) using anterior segment optical coherence tomography (AS‐OCT) and evaluate the effect of anterior chamber morphometrics on endothelial cell changes. SETTING: Department of Ophthalmology, Academic Hospital Maastricht, The Netherlands. METHODS: In this cross‐sectional study, AS‐OCT was used to measure the distances from the center and the edges of the pIOL to the corneal endothelium in 242 eyes with various models of myopic pIOLs. Endothelial cell measurements were performed preoperatively and at each follow‐up examination. RESULTS: The mean follow‐up was 34.1 months ± 24.7 (SD) (range 3 months to 7 years). The mean distance between the edge of the pIOL and the endothelium was 1.37 ± 0.22 mm. Although this distance was smaller than the safety value of 1.50 mm in 68.6% of the eyes, no eye developed corneal decompensation. There was a significant endothelial cell density (ECD) loss of 1.28% ± 8.46%, 3.25% ± 8.24%, and 5.02% ± 10.40% at 2 years, 5 years, and 7 years, respectively. Linear mixed‐model analysis predicted a yearly ECD loss of 0.98% for a mean edge distance of 1.37 mm, 0.15% for an edge distance of 1.59 mm (mean plus 1 SD), and 1.80% for an edge distance of 1.15 mm (mean minus 1 SD). CONCLUSIONS: A shorter distance between the edge of the pIOL and the endothelium was significantly associated with higher ECD loss. For safety reasons, the postoperative examination should include long‐term evaluation of the anterior chamber morphometrics in addition to ECD counts.

Visual outcome and patient satisfaction after multifocal intraocular lens implantation: aspheric versus spherical design.

PURPOSE: To evaluate visual outcomes and patient satisfaction after implantation of an aspheric apodized diffractive intraocular lens (IOL) or a spherical apodized diffractive IOL in cataract surgery. SETTING: Maastricht University Medical Center, The Netherlands. DESIGN: Nonrandomized clinical trial. METHODS: This prospective nonrandomized study with a 6‐month follow‐up compared the results of cataract surgery with implantation of an aspheric AcrySof ReSTOR SN6AD3 IOL and a spherical AcrySof ReSTOR SN60D3 IOL. Main outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, uncorrected (UNVA) and distance‐corrected (DCNVA) near visual acuities, straylight levels, incidence of glare and halos, and contrast sensitivity levels. RESULTS: The mean UDVA was 0.14 ± 0.15 logMAR in the aspheric group (47 eyes) and 0.14 logMAR ± 0.17 (SD) in the spherical group (45 eyes) and the mean CDVA, −0.01 ± 0.06 logMAR and 0.02 ± 0.10 logMAR, respectively. The mean UNVA was Jaeger (J) 1 in 83.0% of patients in the aspheric group and 55.5% of patients in the spherical IOL group (P = .003). The DCNVA was J1 in 95.7% and 71.1%, respectively (P = .001). There were no significant differences between the 2 groups in contrast sensitivity levels, intraocular straylight levels, incidence of night‐vision symptoms, or subjective rating of vision. CONCLUSIONS: Patients with the aspheric multifocal IOL had significantly better near vision than patients with the multifocal spherical IOL. The UDVA, CDVA, intraocular straylight, night‐vision symptoms, and contrast sensitivity were similar between the 2 groups. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Model to predict endothelial cell loss after iris-fixated phakic intraocular lens implantation.

PURPOSE To describe a model predicting endothelial cell (EC) loss after iris-fixated phakic intraocular lens (pIOL) implantation, taking distance from the edge of the pIOL to the endothelium into account. METHODS This prospective observational study monitored long-term EC changes in 306 eyes after pIOL implantation. EC density (ECD) was determined before surgery, 6 months after surgery, and then annually up to 8 years after surgery. Mean follow-up was 31.7 +/- 25.7 months. All eyes underwent anterior segment optical coherence tomography to determine minimum distance from the edge of the pIOL to the endothelium. Linear mixed-model analysis was performed to present a model that describes EC loss as a linear decrease and an additional decrease depending on the postoperative edge distance of the patient. RESULTS Mean minimum edge distance was 1.43 +/- 0.23 mm (range, 0.70-2.21 mm). For this mean edge distance, the model predicted a yearly EC loss of 1.0%, whereas an edge distance of 1.20 mm resulted in a yearly EC loss of 1.7%, and an edge distance of 1.66 mm led to a yearly EC loss of only 0.2%. Furthermore, the model predicted that for patients with preoperative ECDs of 3000, 2500 or 2000 cells/mm(2), and edge distances of 1.43 mm, a critical ECD of 1500 cells/mm(2) (at which point pIOL explantation and cataract extraction can still safely be performed) will be reached at 56, 37, and 18 years after implantation. CONCLUSIONS The presented model predicts EC loss after iris-fixated pIOL implantation in relation to the measured edge distance, patient age, and preoperative ECD, which can assist ophthalmologists in patient selection and follow-up of pIOLs.

Artiflex Toric Foldable Phakic Intraocular Lens: Short-term Results of a Prospective European Multicenter Study

PURPOSE To evaluate the short-term efficacy, predictability, stability, and safety of the foldable Artiflex Toric phakic intraocular lens (pIOL; Ophtec) for the correction of myopia with astigmatism. DESIGN Prospective, nonrandomized multicenter study. METHODS One hundred fifteen eyes of 73 patients were implanted with an Artiflex Toric pIOL. Mean implanted spherical and cylindrical powers were -7.10 ± 2.70 diopters (D) and -2.14 ± 0.80 D, respectively. Total follow-up was 6 months. Outcome parameters included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), subjective manifest refraction (used for vector analysis), intraocular pressure, and endothelial cell density (ECD). RESULTS At 6 months, 99.0% of eyes had a UCVA of ≥20/40, and 81.8% of eyes were ±0.5 D of the intended refraction. In 74.5% postoperative UCVA was equal to or better than preoperative BSCVA; 2 eyes lost 2 or more lines of BSCVA postoperatively because of the development of synechiae. In 75.5% of eyes the remaining cylinder was ±0.5 D. There was a significant decrease in ECD after 3 months (4.8% ± 11.9%), with no additional decline between 3 and 6 months. There were few complications, except for the incidence of pigment and nonpigment precipitates (14.8% and 12.2%, respectively at 6 months). Mean misalignment was 0.6 ± 1.5 degrees (range 0-8). CONCLUSIONS The Artiflex Toric pIOL effectively and safely corrects myopia and astigmatism in the short term, with stable and predictable visual results after 6 months, when strict inclusion criteria are applied. Deposition of pigment and nonpigment precipitates on the pIOL warrants further investigation.

Late-onset decentration of iris-fixated phakic intraocular lenses: a case series.

PURPOSE To investigate late-onset downward decentration of iris-fixated phakic intraocular lenses (pIOL) resulting from progressive shifting of the haptics through the iris and its influence on the position of the pIOL and the amount of enclavated iris tissue. DESIGN Institutional, prospective, observational case series. METHODS Six patients (9 eyes) from among 368 eyes had 1 shifted haptic during long-term follow-up. Anterior segment optical coherence tomography (AS-OCT) was used to measure the distance between the edges of the pIOL and the corneal endothelium. Slit-lamp photography imaged the pIOL after implantation and after decentration. The images were analyzed to determine decentration and amount of iris tissue at the enclavation sites. RESULTS Shifting of the haptics occurred in 2.4% and was discovered at a mean follow-up of 4.8 years (range, 3 to 7 years). Mean downward decentration was 0.28 +/- 0.15 mm. Mean edge-distances on the nasal, temporal, superior, and inferior side were 1.71 +/- 0.30 mm, 1.86 +/- 0.31 mm, 1.86 +/- 0.31 mm, and 1.58 +/- 0.34 mm, respectively. Mean enclavated iris tissue on the nasal and temporal side was smaller after decentration when compared with that directly after surgery (P = .033 and P = .017, respectively). Shifting of the haptics did not result in a decreased uncorrected and best-corrected visual acuity. CONCLUSIONS Late-onset downward decentration resulting from progressive shifting of the haptics occurred in 2.4% and was associated with a decrease in enclavated iris tissue. AS-OCT showed a mean distance between the edge of the pIOL and the endothelium greater than the advised safety distance of 1.5 mm.

The Effect of Iris-Fixated Foldable Phakic Intraocular Lenses on Retinal Straylight

PURPOSE To determine changes in straylight after iris-fixated phakic intraocular lens implantation (pIOL) and to investigate the relationship between straylight and several preoperative and postoperative variables. DESIGN Institutional, prospective cross-sectional study. METHODS Artiflex (Ophtec B.V.) pIOL implantation was performed in 61 eyes (36 patients). Straylight values were measured before surgery and 3 months after surgery using the Oculus C-Quant (Oculus Optikgeräte). Furthermore, correlations were analyzed between straylight and the following parameters: keratometry, axial length, spherical equivalent, astigmatism, pIOL power, best spectacle-corrected visual acuity, and pupil size. RESULTS Mean straylight decreased from 1.18 ± 0.17 log units before surgery to 1.13 ± 0.17 after surgery (P = .016). Higher preoperative straylight values were associated with larger postoperative decreases in straylight (r = -0.534; P < .001). Higher postoperative straylight values were correlated to higher axial length (r = 0.444; P = .001) and lower keratometry values in diopters (r = -0.414; P = .001). After regression analysis, only axial length was found to be an independent predictor of preoperative and postoperative straylight (P < .001 and P = .001, respectively). After correcting for the axial length of an emmetropic eye (23.44 mm), all straylight correlations disappeared, indicating that an increase in distance from cornea to retina explains the increase in straylight values in longer eyes. CONCLUSIONS Retinal straylight was reduced significantly after Artiflex pIOL implantation. Besides age, axial length was the only predictor of preoperative and postoperative straylight values. The increased tissue length light has to pass from cornea to retina, might explain the increase in straylight values in longer eyes.