Umeå University's logo

Objective: To evaluate the effects of customized corneal collagen cross-linking (CXL) on higher-order aberrations (HOAs) in keratoconus (KC): vertical coma (VC), horizontal coma (HC), spherical aberration (SA), trefoil (TF) and astigmatism, compared with the same effects in healthy eyes undergoing CXL for low-grade myopia.

Methods: This mixed-designed study included 38 eyes of 38 patients with KC, treated and followed prospectively, who received customized epi-on CXL in high oxygen, and a retrospective control group of 23 eyes from 23 patients who underwent central 4-mm CXL treatment for low-grade myopia. VC, HC, SA, TF and keratometry values were obtained from Pentacam HR® measurements at baseline and at 1, 6, 12 and 24 months post-treatment. Statistical analyses included paired T-tests for changes over time and Pearson correlation tests to assess relationships between aberrations, best spectacle-corrected and low-contrast visual acuities (BSCVA and LCVA, respectively) and CXL parameters.

Results: Reduced HOAs and improved visual acuities were observed in KC. A 20% reduction in VC was observed at 24 months (from −1.82 ± 1.15 μm to −1.46 ± 1.01 μm; 95% CI: [0.155, 0.629], p = 0.002), while a 17% reduction in HC was observed at 12 months (from −0.35 ± 0.56 μm to −0.29 ± 0.62 μm; 95% CI: [0.003, 0.096], p = 0.037). A positive correlation was found between baseline VC and the level of improvement in VC at 24 months (R2 = 0.200, p = 0.015). SA increased by 126% at 24 months (from −0.21 ± 0.62 μm to 0.054 ± 0.52 μm; 95% CI: [0.143, 0.347], p ≤ 0.001). TF and astigmatism did not alter from the treatment. In myopia, the natural positive SA increased by 57% post-treatment (from 0.14 ± 0.061 μm to 0.22 ± 0.076 μm at 24 months; 95% CI: [0.067, 0.098], p ≤ 0.001), while changes in VC and HC were minor and BSCVA remained stable.

Conclusion: Customized CXL effectively reduces HOAs in KC. For VC the improvement is larger in cases with higher preoperative VC, indicating that the concept of customization has its intended effect. Accordingly, SA and visual acuities improve in KC whereas CXL for low-grade myopia tends to increase corneal SA unfavourably.

Purpose: To study the prioritization effects of the of COVID-19 pandemic on Swedish cataract surgery using a national healthcare registry with high coverage.

Setting: A study from the Swedish National Cataract Register (NCR), involving all patients undergoing cataract surgery in Sweden during 2019–2022 – before, during and after the COVID-19 pandemic.

Results: With the pandemic outbreak, the number of cataract surgeries fell by 22% in 2020 (15 369 procedures), albeit with large regional differences (−43% to +58%). The numbers recovered in 2021, and in 2022, a new top notation was seen (n = 149 952). On a national level, the patients were younger (−0.46 years, p < 0.001), with a larger proportion of less difficult cases (p < 0.001) and the proportion of males was higher (p < 0.001) during the pandemic, but all these variables also differed substantially between different regions and clinics.

Conclusion: A national registry with high coverage can map the consequences of an event disrupting elective surgery in detail. During the COVID-19 pandemic, the impact on Swedish cataract surgery varied largely between different regions, clinics, and healthcare providers, leading to inequality in the availability of surgery. These differences likely owed to variations in healthcare policy approaches in different parts of the country. The present study shows that outcomes at one clinic or region cannot be extrapolated to larger regions under these circumstances. It actualizes the need to aim for a healthcare on equal terms, but it also shows a system that delivers care to many despite difficult times.

Purpose: To compare clinical outcomes of customized transepithelial (epi-on) corneal crosslinking (CXL) in high oxygen and customized CXL with epithelial removal (epi-off) in room air for keratoconus (KC).

Setting: Umeå University Hospital, Umeå, Sweden.

Design: Prospective, randomized, single-masked, intraindividually comparing study.

Methods: 32 participants with bilateral progressive KC were treated with bilateral customized topography-guided CXL, 30 mW/cm2; 7.2 to 15 J/cm2and were randomized to epi-on in one eye (32 eyes) and epi-off in the fellow eye (32 eyes). Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), maximal keratometry (Kmax), subjective ocular discomfort, low-contrast visual acuities (LCVAs) at 10% and 2.5% contrast, ocular and anterior corneal wavefront aberrations, manifest refractive spherical equivalent, endothelial cell count (ECC), and adverse events were assessed through 24 months.

Results: Both treatments showed improvements at 24 months in UDVA; -0.16 ± 0.24 (P <.001) and -0.13 ± 0.20 logMAR (P =.006), respectively, CDVA; -0.10 ± 0.11 (P <.001) and -0.10 ± 0.12 (P =.001), Kmax; -1.74 ± 1.31 (P <.001) and -1.72 ± 1.36 D (P <.001). LCVA 10% improved for both protocols (P <.001), but LCVA 2.5% improved for epi-on CXL only (P =.001). ECC was unaltered, and no adverse events occurred. The epi-on eyes had significantly less discomfort symptoms during the whole first week posttreatment (P <.05).

Conclusions: High-oxygen customized epi-on CXL is a viable alternative to room air customized epi-off CXL, with faster improvements in CDVA and LCVA and less early ocular discomfort.

Purpose: To compare the safety of a standardized, commercially available intracameral combination of mydriatics and anesthetic (ICMA) with a reference topical mydriatic regimen for cataract surgery.

Patients and Methods: The safety results from two international, randomized, controlled clinical studies were combined to compare ICMA at the beginning of cataract surgery (ICMA group) to the reference topical mydriatic regimen (reference group). Data were collected on ocular and systemic adverse events, corneal and anterior chamber examination, endothelial cell density, retinal thickness and visual acuity. Analysis was performed on a pooled safety set from both studies, preoperatively and up to 1 month postoperatively.

Results: 342 patients received ICMA and 318 the reference topical regimen. Ocular adverse events were reported in 17.0% of patients in the ICMA group and 18.6% in the reference group. No difference was shown between groups in endothelial cell density (2208 ± 498 cells/mmfor ICMA group versus 2241 ± 513 cells/mmfor the reference group; p=0.547) and retinal thickness (change from baseline less than 50 µm in 94.7% versus 95.0% of patients, respectively) at 1 month postoperatively. At 1-day post-surgery, less patients in the ICMA group had moderate or severe (Grades 2 and 3) superficial punctate corneal staining (3.9% versus 7.0% for the reference group; p=0.064). Postoperatively, some ocular symptoms were also less frequently reported in the ICMA group. Best-corrected visual acuity increased in 96.0% of patients in the ICMA group and 95.8% in the reference group at 1 month.

Conclusion: ICMA injection at the beginning of cataract surgery was demonstrated to be safe and may also provide perioperative and postoperative advantages over the standard topical mydriatic regimen.

Purpose: To study the trend of delayed sequential bilateral cataract surgery (DSBCS) in Sweden in the past decade.

Methods: This register-based cohort study utilized data from the Swedish National Cataract Register (NCR) from 2010 through 2019. Register files from patients who underwent cataract surgery in both eyes during the study period were linked using their social security numbers. Bilateral surgeries on different days were classified as DSBCS. The study investigated the association between DSBCS within 3 months and several variables with stratification and multivariate logistic regression. The following variables were used: operation year, region, private or public unit, age, sex, indication for surgery, type of intraocular lens (IOL), preoperative visual acuity, ocular comorbidity, posterior capsule rupture and perioperative difficulties.

Results: During the study period, 368,106 patients underwent DSBCS, of which 62.6% (n = 230,331) had bilateral surgery within 3 months. The median time between the surgeries was 61 days (interquartile range 26–161 days), showing regional variations. Better visual acuity in the fellow eye, presence of ocular comorbidity, various perioperative events and complications were associated with longer time to surgery of the second eye. Conversely, cataract surgery in more recent years, private clinic, increasing age, anisometropia and multifocal IOL were associated with shorter timespan between surgeries.

Conclusions: The majority of DSBCS were conducted within a 3-month timeframe, with the interval between surgeries decreasing throughout the study period. Several rational factors were associated with the time difference, in addition to regional variations. Many patients would probably benefit from less time between the surgeries, and we encourage a clinical practice taking the whole patient’s visual function into account.

Purpose: To analyse trends of ISBCS reported to the Swedish National Cataract Register (NCR) over a 10-year period.

Methods: Since 2010 the NCR contains social security number of all individuals in the list of parameters reported to NCR after each cataract procedure. Bilateral surgeries were mapped out using social security numbers. When dates of both-eye surgeries are identical for an individual it is classified as an immediate sequential bilateral cataract surgery (ISBCS). This study includes all data reported during the period 1st of January 2010 to 31st of December 2019. During the study period 113 cataract surgery clinics affiliated to the NCR reported their data on consecutive cataract cases.

Results: For the whole period 54 194 ISBCS were reported. The total number of bilateral cataract extractions was 422 300. There was a significant trend of increasing ISBCS over time with linear regression (Beta = 1.75, p < 0.001). In ISBCS the occurrence of an ocular comorbidity decreased over time. The use of a capsular tension ring was significantly more common in ISBCS than in delayed sequential bilateral cataract surgery (DSBCS). All other measures taken during surgery were more common in DSBCS. The use of multifocal IOL was significantly more frequent in ISBCS compared to DSBCS (p < 0.001).

Conclusions: The use of ISBCS has increased over the study period. The operated eyes have less risk factors than eyes going through a DSBCS, but both ocular comorbidities and surgical complications occur in ISBCS eyes.

Cataract surgery is the most commonly performed surgery worldwide. However, there is significant variation in practice both within and among countries. The European Registry of Quality Outcomes for Cataract and Refractive Surgery was established in 2007 to address this variation and improve the quality of care. Based on registry data from more than 500,000 surgeries, the registry developed the first European guidelines for cataract surgery, with plans to improve those guidelines continuously with registry-based studies. At this point, the registry has collected data from more than 4 million surgeries, creating opportunities for establishing guidelines, conducting research, and benchmarking. This article describes how the registry was developed, its achievements, planned refinements, efforts to expand participation, the challenges encountered, and future potential.

Purpose: To analyse the temperature of the corneal surface in keratoconus during corneal customized crosslinking (CXL) with a preserved epithelium (epi-on) under oxygen flow, and epi-off CXL in room air, and to assess the effect of pre-heating the oxygen.

Methods: This masked, intra-individual comparing randomized study included 14 participants with bilateral progressive keratoconus treated with bilateral CXL: one eye with epi-on CXL under a flow of 2.5 L/min oxygen; the fellow eye with epi-off CXL in room air. In a second setting involving 12 healthy participants, room-tempered oxygen was flushed over one eye and oxygen pre-heated to 37°C over the fellow eye. The corneal surface temperature was assessed with infrared photography.

Results: A reduction in corneal surface temperature was seen from the pre-treatment application of topical riboflavin in the epi-off group (−1.1 ± 1.0°C, p < 0.001). The temperature increased during the first half of the CXL treatment in both groups (+0.7 ± 1.2°C, p = 0.041 for epi-on; +0.7 ± 0.9°C, p = 0.023 for epi-off CXL, respectively). In epi-on CXL an overall temperature increase was seen during the treatment (+0.8 ± 1.2°C, p = 0.016). In the second setting, pre-heating the oxygen rendered a surface temperature increase of +1.8 ± 0.2°C (p < 0.001).

Conclusion: In epi-off CXL, the application of topical room-tempered riboflavin decreases the corneal surface temperature, likely due to increased evaporation. A slight temperature increase is seen during CXL with both epi-on and epi-off CXL, albeit far below the corneal safety limit. The corneal temperature can, however, be increased by applying pre-heated oxygen, a possible approach to modify or augment the treatment effect in CXL.

Purpose: To investigate the surgical and pharmacological management and outcomes of patients with cataract and concurrent uveitis.

Methods: Data from the Swedish National Cataract Register, 2018–2019, were collected and analysed. Uveitic eyes were identified and eyes without uveitis were used as controls. Generalized estimating equations were used to adjust for intra-individual correlation.

Results: The study included 719 eyes with and 256 360 without uveitis. The mean age was 66.0 ± 13.5 (standard deviation [SD]) years in the uveitis group and 74.3 ± 8.7 years in the control group (p < 0.001). Surgery was associated with more intraoperative difficulties in eyes with uveitis (27.0%) than in control eyes (7.1%; p < 0.001). Posterior capsule rupture/zonular complications were registered in nine eyes with uveitis (1.3%) and in 1464 eyes without uveitis (0.6%; p = 0.02). Hydrophilic acrylic intraocular lenses (uveitis 3.6%, controls 1.2%) and subconjunctival steroids (uveitis 17.4%, controls 6.1%) were more frequently used in eyes with uveitis (p < 0.001). post-operative best-corrected visual acuity (BCVA) was 0.16 ± 0.38 logarithm of the minimum angle of resolution (logMAR, mean ± SD) in eyes with uveitis (n = 52) and 0.08 ± 0.20 in control eyes (n = 14 489; p = 0.008).

Conclusion: In this large registry-based Swedish cohort study, the findings demonstrate that cataract surgery in patients with uveitis poses more challenges and requires special surgical precautions. Eyes with concurrent uveitis had worse BCVA prior to and following surgery. Despite the intraoperative challenges, the visual improvement was greater in the uveitic group.

Purpose: To evaluate the performance of different probabilistic classifiers to predict posterior capsule rupture (PCR) prior to cataract surgery. Methods: Three probabilistic classifiers were constructed to estimate the probability of PCR: a Bayesian network (BN), logistic regression (LR) model, and multi-layer perceptron (MLP) network. The classifiers were trained on a sample of 2 853 376 surgeries reported to the European Registry of Quality Outcomes for Cataract and Refractive Surgery (EUREQUO) between 2008 and 2018. The performance of the classifiers was evaluated based on the area under the precision-recall curve (AUPRC) and compared to existing scoring models in the literature. Furthermore, direct risk factors for PCR were identified by analysing the independence structure of the BN. Results: The MLP network predicted PCR overall the best (AUPRC 13.1 ± 0.41%), followed by the BN (AUPRC 8.05 ± 0.39%) and the LR model (AUPRC 7.31 ± 0.15%). Direct risk factors for PCR include preoperative best-corrected visual acuity (BCVA), year of surgery, operation type, anaesthesia, target refraction, other ocular comorbidities, white cataract, and corneal opacities. Conclusions: Our results suggest that the MLP network performs better than existing scoring models in the literature, despite a relatively low precision at high recall. Consequently, implementing the MLP network in clinical practice can potentially decrease the PCR rate.