Aberrometry, Trypan Blue, PMCD and inflammation

October 9, 2013

Review of the fifth day of ESCRS 2013

Aberrometer safe and effective for instruction of excimer laser


Using the new iDesign Aberrometer (Abbott Medical Optics; Santa Ana, California, USA) to instruct the ablation profile to the STAR S4 IR excimer laser platform (Abbott Medical Optics) results in a safe and effective procedure for the reduction of myopia and myopic astigmatism, according to Dr Josef Ruckhofer (University Eye Clinic, Paracelsus Medical University, Salzburg, Austria) and colleagues. They announced the findings of their prospective non-comparative study of 100 eyes undergoing the CustomVue procedure with the iDesign aberrometer during a free paper session this morning.
All of the studied eyes were undergoing Wavefront Guided (WFG) LASIK surgery for the correction of myopic astigmatism, and had corneal flaps created by the iFS femtosecond laser (Abbott Medical Optics).
"A comprehensive visual and ocular examination was performed preoperatively in all cases that included manifest and cycloplegic refraction, uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA)," said Dr Ruckhofer.
Patients were examined postoperatively 1 day, 1 week and 2 months after surgery. At the final follow-up visit, UDVA was ≥0.8 in 95/100 eyes (95%), ≥1.0 in 91/100 eyes (91%) and 1.2 in 81/100 eyes (81%); there were no losses of ≥2 lines of CDVA and 5/100 eyes (5%) gained 2 lines. Postoperative spherical equivalent was within 1.0 D in 97/100 eyes (97%) and within 0.5 D in 95/100 eyes (95%).
"There was no significant increase of high order RMS and primary spherical aberration postoperatively. Conversely, a non-significant decreasing trend in HOA values was found," Dr Ruckhofer added. "We therefore conclude that the iDesign Aberrometer is safe and effective for the instruction of an excimer laser during LASIK surgery."

Trypan Blue does not influence iris pattern recognition


The vital dye Trypan Blue, used during phacoemulsification of eyes with white, mature cataracts does not influence the process of iris pattern recognition system, Dr Suzana Matić (Josip Juraj Strossmayer University of Osijek, Osijek, Croatia) and colleagues have concluded.
The team conducted a prospective study of eyes undergoing phacoemulsification (n=30) and eyes undergoing phacoemulsification with Trypan Blue (n=30), with a control group of eyes (n=30) who did not undergo surgery and were not administered any topical prostaglandins.
"The eye photographs of the patients before surgery and one month after the surgery, as well as the eye photographs of patients in the control group, were entered in the database and analysed using the software for iris identification," said Dr Matić.
The main result obtained by comparing the two pictures is the percentage of correspondence, and this was found to be 85.0% (range: 71.0–89.0%) and 78.5% (range: 68.0–85.0%) in phacoemulsification with and without Trypan Blue, respectively; in control eyes, the percentage of correspondence was found to be 91.0% (86.0–96.0%). These findings demonstrate that phacoemulsification (regardless of dye use) affects the percentage of correspondence and therefore influences the ability for existing iris identification programs to accurately identify patients (Man Whitney U test, p "Although the application of biometric iris identification systems has been proved as highly reliable and precise, results obtained in this research call for correction of algorithm and modification of certain procedures in the process of person recognition (recording, lighting, and so on). This will ensure the improvement in quality, accuracy and safety of this biometric system," Dr Matić concluded.

A novel treatment for extremely advanced PMCD


A new technique to partially excise and then 'tuck' the ectasia not only makes excisional surgery possible for eyes with extremely advanced pellucid marginal corneal degeneration (PMCD) with a minimal effect on the structural integrity of the eye, but also rehabilitates vision to the 20/50 level or better, explained Dr R Barbara (Villa Igea Hospital, Forli, Italy) and colleagues during this morning's 'Cornea Surgical' session.
A case series of 3 eyes with extremely advanced PMCD (defined as the ectatic area extending for about 4 mm from the corneoscleral limbus towards the centre of the cornea and over ~270° of the circumference), which were unsuitable for conventional surgical approaches, were treated with this novel surgical procedure.
As described by Dr Barbara, the procedure involves: "Removal of the corneal peripheral epithelium from the entire area of thinning and opening of the conjunctiva at the limbus; excision of a full-thickness strip of thinned corneal tissue, about 1 mm in width, along the whole 270° of the ectasia; overlapping of the residual wound margins ("corneal tuck"), which were then sutured together with interrupted 10-0 nylon stitches and a 10-0 nylon running suture."
Selective removal of the sutures was completed within 9 months of surgery in all 3 cases.
No complications were recorded during or after surgery in any case. Uncorrected best spectacle-corrected visual acuity (BSCVA), refraction, and corneal topography were assessed preoperatively as well as 3, 6, 9, 12, 24, 36 (n=2), and 48 (n=1) months after surgery in all cases. Preoperative BSCVA was limited to perception of hand movement for 1 eye and finger counting in 2 eyes; one year postoperatively, all eyes had BSCVA of ≥20/50, with refractive astigmatism within 5.0 D in all eyes. Two eyes underwent phacoemulsification with IOL implantation in the first year after surgery but refractive outcomes remained unchanged during the remainder of the follow-up period.
"This demonstrated that the partial excision and tucking technique is safe and effective for rehabilitating corneal shape, and the corneal tuck that was created was sufficiently thick to allow easy and safe suturing through the tucked tissue, and the resulting scar was strong enough to avoid recurrence of ectasia," Dr Barbara concluded.

Inflammatory response in the anterior chamber after IOL implantation


The AcrySof Cachet (Alcon; Hünenberg, Switzerland), a new foldable acrylic anterior chamber IOL model designed to reduce or eliminate moderate to high near-sightedness in adults, is not associated with the inflammation that has been a common feature of anterior chamber IOL implantation, Dr Suphi Taneri (St Franziskus Hospital, Münster, Germany) and colleagues have announced.
Dr Taneri and his team conducted a prospective study of 15 eyes implanted with the AcrySof Cachet. All implanted eyes had stable myopia >7.0 D and anterior chamber depth (including corneal thickness) ≥3.2 mm, endothelial cell density that was sufficient according to the manufacturer’s age-related recommendations, and no other pre-existing ocular conditions or previous eye surgery. After implantation of the IOL, treatment included antibiotic eye drops for 5 days and non-steroidal anti-inflammatory eye drops for 4 weeks: no steroidal eye drops were administered.
A slitlamp was used to evaluate 1 mm x 1 mm segments of the anterior chamber; measurements performed before and 1 day, 1 week, 1 month, 3 months and 12 months after implantation revealed 0–10 cells within the measurement window on every visit. Laser cell flare values were 8.29 photons/ms (range: 1.80–40.40 photons/ms), 18.96 photons/ms (3.10–100.30 photons/ms), 23.56 photons/ms (6.60–114.90 photons/ms), 15.33 photons/ms (3.40–48.60 photons/ms), 14.87 photons/ms (3.80–63.90 photons/ms) and 10.00 photons/ms (1.10–26.00 photons/ms) preoperatively and at 1 day, 1 week, 1 month, 3 months and 12 months after implantation.
"These results indicate that, in addition to the excellent visual outcomes of the AcrySof Cachet, there is a low maximum inflammatory response in the anterior chamber and a relatively quick recovery of laser cell flare counts to safe values after implantation," Dr Taneri concluded. “Avoiding corticoids, which should be possible in most cases, can help to limit the drawbacks associated with this method of anti-inflammatory prophylaxis.”