The American Academy of Ophthalmology’s (AAO) 2018 annual meeting was held in Chicago, Illinois, U.S.A., from October 27 to 30. Below, we detail some of the intriguing posters in refractive surgery from this prestigious meeting.
Femtosecond-Assisted Crosslinking vs. Conventional Crosslinking
Crosslinking is a hot topic in refractive surgery these days. To prove that deeper cross-linking (CXL) better dampens keratoconus, Dr. Lional Raj D. from Dr. Agarwal’s Eye Hospital in Tirunelveli, India, compared femtosecond-assisted crosslinking (FC) with the conventional CXL (CC). Twenty-five eyes underwent FC, while 22 underwent CC. Vision, pachymetry, maximum keratometry (K-max), simulated keratometry (SimK), and the anterior segment OCT-derived demarcation line (DL) were analyzed at one year.
At follow-up, vision improved 2 lines in the FC group and 1 line in the CC group. Pachymetry was maintained in FC eyes, while it dropped 28 microns in CC eyes. The corneas were flattened in both groups. The FC group’s astigmatism was reduced by 0.31 diopters (D), and in the CC group it increased by 0.27D. Regarding the DL, it was 393 microns deep in FC eyes and 243 in CC eyes. There were no endothelial changes noted.
These results led the author to conclude that “femto-laser assists deeper crosslinking than conventional procedures, favoring an effective stabilization as proof of ‘the deeper, the better’ concept”.
Achieving Perfection with Multicomponent IOLs
Today, advances in intraocular lens (IOL) technology allow surgeons more flexibility to enhance patient outcomes and visual acuity. For example, multi-component IOLs (MC-IOLs) allow for refinement after cataract surgery through surgical exchange of its refractive components. To determine the safety and consistency of these lenses, Dr. Harvey Uy, medical director at Peregrine Eye and Laser Institute in Makati, Philippines, presented results of refractive enhancements on eyes that received MC-IOLs after cataract surgery.
Three months following the primary surgery, 50 eyes with a manifest refraction spherical equivalent (MRSE) greater than 0.75D underwent enhancement. During the procedure, the primary front IOL optic was replaced with a new front optic with the corrected refractive power. The main outcome measures were three-month post-enhancement unaided distance visual acuity (UDVA) in logMAR, MRSE change and adverse events.
Following the procedure, the mean (SD) preoperative UDVA of 0.2 (0.15) logMAR improved to 0.0 (0.07), (P= .008). The mean pre-enhancement MRSE decreased from +1.4 (0.9) D to +0.1 (0.4) D, (P= .0002). All eyes had a UDVA of 0.1 or better, and no significant adverse events occurred.
This led Dr. Uy to conclude that “MC-IOL enhancement is a safe and consistent method of refractive enhancement that enable cataract surgeons to optimize outcomes”.
Enhancement Options Following SMILE
Following any refractive surgery, its possible enhancements might be necessary to optimize visual outcomes. In this poster, Egyptian cornea and refractive specialists Drs. Moones Fathi Abdalla and co-author Osama Ibrahim evaluated different techniques for enhancement following small incision lenticule extraction surgery (SMILE).
Four techniques were used: PRK, flap creation (off-label); circle option, flap creation; capless/cap-preserving re-SMILE (off-label); and sub-SMILE retreatment (SMILE at a deeper level, off-label).
This retrospective assessment looked at retreatment cases from more than 10,000 eyes. The authors mandated that time between the primary and retreatment surgeries was at least three months. In all, five eyes underwent PRK, two eyes with new flap creation, three eyes had the circle option, four eyes were capless, and three eyes had the sub-SMILE treatment.
Following retreatment, surgical challenges, visual recovery, and visual outcomes were assessed. The authors found that all modalities had minimal surgical complications. And while visual recovery varied widely between the groups, at one-month follow-up all cases showed excellent visual outcomes.
This led the authors to conclude that “Retreatment for SMILE visual outcome is very promising if it’s taken into consideration that it is case-specific and that every technique has its indications”.
Managing Complications in SMILE
This retrospective review of consecutive case series reported complications associated with the SMILE procedure. Along with colleagues, Dr. Arturo J. Ramirez-Miranda, assistant professor of ophthalmology in cornea and refractive surgery at Instituto de Oftalmologia Conde de Valenciana in Mexico City, looked at 460 eyes of 231 patients, with a mean follow-up time of 72 months.
Including the surgeons’ learning curve cases, they found that 7% had complications. These included: epithelial defect, suction loss, opaque bubble layer, cap rupture, lenticule rupture, interface haze, residual refractive errors, and infectious keratitis.
The low complication rate led the authors to conclude that “while SMILE complications can occur, most are related to inexperience and are included in the learning curve of the technique, with favorable resolution, because the majority of them are mild and have no lasting effect on the patient’s final visual acuity”.
Does Bowman’s Layer Influence Corneal Biomechanics?
A recent study by Dr. Emilio A. Torres Netto and colleagues at the University of Zurich, Switzerland, tested the biomechanical properties of Bowman’s layer (BL) in healthy ex vivo human corneas using stress-strain extensometry.
The investigators obtained 26 corneas following Descemet membrane endothelial keratoplasty, and separated them into two groups. In group 1, the BL was ablated (20µm thick, 10mm optical zone); in the second group the BL was left intact. In both groups, a 110µm thick lamella was cut and elastic-viscoelastic properties were analyzed.
During pre-conditioning and destructive testing, no significant differences in the elastic modulus was noted between groups. Additionally, no significant differences were found in relation to stress. Therefore, the authors determined that the presence or absence of the BL did not alter the stiffness of a 110µm cornea lamella.
“These results may have implications, not only in refractive laser surgeries, but also for Bowman layer transplantation in keratoconus,” concluded the authors.
Protecting Diabetic Patients Against Macular Edema
This prospective, interventional study assessed the efficacy of phacoemulsification combined with intravitreal bevacizumab in diabetic patients without macular edema as a prophylaxis against developing the condition postoperatively.
In this study by Drs. Ashraf H. El Habbak and co-author Mohammed Awwad from Benha University in Egypt, 100 eyes of 65 patients were randomly split into two groups: 50 eyes in Group A underwent phacoemulsification alone; and 50 eyes in Group B received combination phacoemulsification and intravitreal bevacizumab. Patients were followed-up for one year – during these visits, central macular thickness (CMT) was recorded using OCT.
The end of the third follow-up month saw significant CMT increases in Group A, from 167.58 ± 7.36mm preoperatively to 208.56 ± 25.99mm (P< .005). No significant changes were found in Group B, from 165.86 ± 6.89mm preoperatively to 160.12 ± 4.48mm (P> .005).
This led the authors to conclude that the “use of intravitreal bevacizumab combined with phacoemulsification protects against the development of macular edema in diabetic patients without diabetic maculopathy”.
