CI-OCT, monovision and nomograms

September 13, 2012

During the final day of lectures at the Milan ESCRS 2012…

Monovision to the extreme for diplopia


Extreme pseudophakic monovision could treat stable acquired strabismus with diplopia, a busy Dr Osher concluded in the Complex Surgery lecture earlier.
The case series investigation, "New instruments and devices in cataract surgery", took twelve patients with stable diplopia and created intentional extreme monovision in all the eyes waiting for cataract surgery.
In one eye an intraocular lens was used to target emmetropia and a minimum of 3.0 D of myopia in the fellow eye. All patients achieved excellent uncorrected distance and near vision and a significant reduction or elimination of double vision.
Dr Osher stated, "Patients with stable acquired strabismus with diplopia may be candidates for extreme pseudophakic monovision, which may be a new strategy to eliminate double vision."

CI-OCT can multi-task in lamellar corneal surgery


Continuous intraoperative optical coherence tomography (CI-OCT) allows biometric measurements during surgery and ‘live’ qualitative morphological assessment, said Dr Oliver Findl earlier today. The study, titled "Continuous intraoperative OCT integrated into the operating microscope for lamellar keratoplasty" involved 15 eyes of 15 patients with Fuchs endothelial dystrophy, bullous keratopathy, keratoconus and deep stromal scars. Each participant was scheduled for corneal lamellar surgery. Dr Findl used a prototype operating microscope with a microscope-integrated anterior segment OCT device for the treatment. The lecture, part of the free paper session Corneal Surgery III, revealed that CI-OCT is useful for DSAEK, ensuring a complete removal of Descemet and was also helpful for the detection of fluid in the interface. Also, the folding of the transplant in the implantation device, such as the Tan glide, can me monitored when loading. Deep anterior lamellar keratoplasty (DALK) proved to be successful with the CI-OCT due to efficient visualization of the big bubble.
Dr Findl presented example video clips of DSAEK procedures to the audience, demonstrating that CI-OCT allows qualitative morphological, as well as quantitative perioperative biometric evaluation of the anterior segment. Dr Findl claimed, "This new surgical tool has great potential to guide treatment and enhance outcomes for lamellar corneal surgery."

Nomogram developed to gain the best outcomes from WFG LASIK


A nomogram has been developed to gain the greatest gain in outcomes of WFG LASIK procedures for myopia.
Dr Schallhorn presented the free paper session study, "Development of an optimal wavefront-guided LASIK nomogram for myopia using a large dataset", explaining he assessed 64,739 eyes of 32,990 patients across 41 surgical centres. Each patient underwent laser vision correction with wavefront guided (WFG) LASIK for the treatment of myopia.
A good nomogram starts with knowing the target. For this, Dr Schallhorn produced a graph that depicted patient satisfaction against postoperative sphere, which demonstrated that achieving 0.0 D from surgery results in the highest patient satisfaction. This applies for older patients who seek good distant vision as well.
Dr Schallhorn said, "The extensive data validation process included outlier verification and data logic checks. The follow up was 100% for one month, 66% for three months and 53% for six months used for significance testing, model development and trend preservation confirmation, respectively."
Preoperative parameters were used to identify relative variance and covariance on outcomes and included age, gender, manifest refraction, higher order aberrations, and treating surgeon. The nomogram was developed using an iterative procedure to maximize refractive outcomes and simplicity of use.
At the three-month results, the two parameters with the strongest influence were preoperative manifest sphere and disparity between the manifest and treated sphere. Age and spherical aberration had a much smaller effect.
Dr Schallhorn continued, "The most comprehensive model, which included all the significant variables, was expected to offer the most improvement for refractive accuracy. However, in the iterative process, a much simpler nomogram model was developed which achieved nearly identical refractive accuracy as the more complicated comprehensive model."
"This model involved selecting a WF capture where the derived sphere is between -0.75 D and 0.75 D with a physical adjustment to match the manifest sphere to the treatment sphere and adding a % boost to the treatment. This will also improve the cylinder outcomes."

Purely aspheric is the way to go in myopia


Purely aspheric ablations offer better clinical results than purely wavefront-guided ablations in myopic astigmatic corrections.
Dr Suphi Taneri presented the findings on the study titled "Comparing aspheric, wavefront-guided, and aspheric wavefront-guided treatments" at yesterday,s Surgical Refinement in LASIK lecture.
The observational, single-centred study included 161 aspheric-treated eyes in group one, 148 wavefront-guided treated eyes in group two, 202 aspheric wavefront-guided treated eyes in group three.
The measurements recorded included distance visual acuity, automated refraction, total higher order aberration (HOA) root mean square (RMS), spherical aberration, low contrast visual acuity preoperatively and three and six months postoperatively.
Mean postoperative corrected distance visual acuity preoperatively was 0.94, 0.91 and 1.00 for groups one, two and three, respectively. This is compared to mean postoperative uncorrected distance visual acuity of 0.90, 0.83 and 0.96 in groups one, two and three, respectively.
The postoperative spherical equivalent in groups one, two and three was -0.22, -0.30 and -0.24 D, respectively and mean HOA RMS for one, two and three were 0.48±0.18 m

2

, 0.60±0.20 m

2

and 0.46±0.23 m

2

, respectively.
Dr Taneri explains the results "demonstrate that using only purely aspheric ablations yields a slight improvement in clinical results, compared to wavefront-guided ablations. The clinical results, in terms of HOA RMS and low contrast visual acuity, were significantly better with the aspheric ablations."