Omid Kermani

Retrospective study of retinal detachment following neodymium:YAG laser posterior capsulotomy

ABSTRACT A retrospective study of 1,000 cases that had Nd:YAG laser posterior capsulotomy after cataract surgery is presented. We analyzed the correlation of the patients age, axial length of the eye, method of cataract surgery, and laser parameters (exposures, energy, and burst mode) with the incidence of retinal detachment (1.6% overall). The highest risk for retinal detachment (12.3%) was in patients with an axial eye length of 26.1 mm to 28.0 mm. The average age of patients with retinal detachments was 60.6 years, ten years younger than the collective average age. Laser parameters, such as energy, exposures, and burst mode, and the method of cataract surgery (extracapsular or phacoemulsification) did not correlate with the incidence of retinal detachment. After surgical treatment of the 16 retinal detachments, a good postoperative visual acuity (better than 20/40) was achieved in most cases.

Intrastromal refractive surgery with ultrashort laser pulses: in vivo study on the rabbit eye

BackgroundFemtosecond (fs) laser pulses may offer new possibilities in the field of refractive surgery, especially when using the laser as a microkeratome. By induction of nonlinear absorption processes the laser can be used to perform intrastromal cuts. The conventional microkeratome, associated with numerous potential side effects, can possibly be replaced. Furthermore, refractive lenticules can be prepared within the stroma and removed in a single-step operation.MethodsIn 10 rabbits, cuts were made to create both a lamellar flap and an intrastromal refractive lenticule. The flap was lifted, the lenticule was extracted and, finally, the flap was repositioned (intrastromal laser keratomileusis, ILK). The corneal samples were collected up to 120 days after treatment and processed for histopathological analysis.ResultsAll flaps could be opened and prepared lenticules could be extracted in one piece by the surgeon. The treated corneas developed a mild wound healing reaction, comparable to that known from excimer laser in situ keratomileusis (LASIK) studies. The wound healing was restricted to the flap–stroma interface, most pronounced at the periphery of the flaps.ConclusionsThe use of the fs-laser offers new possibilities in preparation of corneal flaps, possibly providing advantages over conventional microkeratomes. Furthermore, the fs-laser has the potential to create intrastromal refractive lenticules for complete refractive procedures (ILK).

Dual intraocular lens implantation: Monofocal lens in the bag and additional diffractive multifocal lens in the sulcus

PURPOSE: To evaluate a new diffractive multifocal intraocular lens (IOL) as an additional (add‐on) IOL for sulcus‐based implantation. SETTING: Augenklinik am Neumarkt, Köln, Germany. METHODS: In this prospective study, cataract patients had phacoemulsification and IOL implantation. After phacoemulsification, an aspheric silicone monofocal IOL (MS 612 ASP‐Y) with a power range of +4.00 to +27.00 diopters [D]) was implanted in the capsular bag. This was followed by sulcus placement of an add‐on multifocal IOL (MS 714 PB) with a +3.50 D diffractive element for near but zero refractive power for distance. RESULTS: The study included 56 eyes of 30 patients. Three months postoperatively, the mean monocular uncorrected distance visual acuity was 0.10 logMAR ± 0.11 (SD) (median 1.00 decimal; 20/20 Snellen), with a remaining mean postoperative spherical equivalent of 0.01 ± 0.51 D. The mean uncorrected intermediate visual acuity was 0.20 ± 0.15 logMAR (median 0.63 decimal; 20/30 Snellen) with a luminance of 500 lux at 1 m. The mean uncorrected near visual acuity (Early Treatment Diabetic Retinopathy chart) was 0.16 ± 0.13 logMAR (median 0.80 decimal; Jaeger 2). No major complications (eg, iris chafing, iris capture, lens epithelial cell ingrowth, glaucoma) were associated with the add‐on IOL in the sulcus. CONCLUSIONS: Combined implantation of an add‐on diffractive sulcus IOL and a monofocal capsular bag IOL was safe and effective in improving far and near visual acuity in cataract surgery. Preliminary visual acuity results were similar to those in eyes with a single 1‐piece diffractive multifocal IOL.

Hyperopic laser in situ keratomileusis with 5.5-, 6.5-, and 7.0-mm optical zones.

PURPOSE To evaluate the results of laser in situ keratomileusis (LASIK) for the correction of hyperopia and hyperopic astigmatism using a large 7.0-mm optical zone and to compare them with treatments using a 5.5- and 6.5-mm optical zone. METHODS One hundred sixty-one eyes of 89 patients with a mean preoperative spherical equivalent refraction of +2.44 +/- 1.32 diopters (D) (range: +0.00 to +5.62 D, cylinder 5.25 to 0.00 D) were treated for hyperopia and hyperopic astigmatism using a 7.0-mm optical zone and were analyzed retrospectively. Postoperatively, patients were examined after 1 day, 1 week, 1 month, 3 months, and 1 year. Eyes treated previously at the same center by the same surgeons with 5.5- and 6.5-mm optical zone applications were used as controls. All treatments were performed with the Nidek EC 5000 CXII excimer laser system (Nidek, Gamagori, Japan). A nasal hinged flap was created using the Nidek MK 2000 microkeratome in all cases. RESULTS The mean postoperative spherical equivalent refraction after 1 month (n=89) was +0.12 +/- 0.72 D (range: -1.75 to +2.75 D), +0.13 +/- 0.74 D (range: -1.88 to +1.62 D) at 3 months (n=70), and +0.20 +/- 0.69 D (range: -1.62 to +1.12 D) at 1 year (n=33). Regression between 1 month and 1 year was 0.08 D in the 7.0-mm optical zone group. Regression was 0.25 D in the 5.5-mm group and 0.02 D in the 6.5-mm optical zone group between 1 month and 1 year. In both the 5.5- and 6.5-mm optical zone groups, 13% of eyes lost one line in visual acuity (2% in the 7.0-mm optical zone group). The gain of one or more lines in visual acuity was 19% in the 5.5-mm group, 17% in the 6.5-mm group, and 27% in the 7.0-mm optical zone group. All data represent primary cases without retreatment. CONCLUSIONS Increasing the optical zone size from 5.5 mm to 6.5 mm and to 7.0 mm seems to improve refractive results, stability, and safety of hyperopic and hyperopic-astigmatic LASIK treatments. Although some hyperopic and astigmatic eyes are endangered by loss of lines in best spectacle-corrected visual acuity, more eyes gain one or more lines.

Comparative micromorphologic in vitro porcine study of IntraLase and Femto LDV femtosecond lasers.

PURPOSE: To assess flap creation and stromal bed quality of 2 femtosecond refractive surgery lasers in laser in situ keratomileusis. SETTING: Augenklinik am Neumarkt, Cologne, Germany. METHODS: Corneal flaps were created in 115 freshly enucleated porcine eyes using the 60 kHz IntraLase FS laser (Advanced Medical Optics) and a prototype model of the Femto LDV femtosecond laser (Ziemer Ophthalmic Systems AG). The parameters that were evaluated included actual versus intended thickness by subtraction pachymetry, cutting and total suction time, quality of flap edges, and smoothness of flap beds. Confocal microscopy (Atos PLμ [Altos GmbH]) was used to objectively determine the root mean square (RMS) of the surface roughness of the stromal bed. RESULTS: Cutting time was 31 seconds for the 60 kHz IntraLase FS laser and 38 seconds for the Femto LDV laser. With both lasers, the standard deviation in achieved versus intended flap thickness was small (136 μm ± 10 and 130 ± 9 μm, respectively). Under micromorphologic examination, stromal bed quality was slightly better with the IntraLase. The RMS of bed roughness was 1.6 ± 0.5 μm with the IntraLase and 2.0 ± 0.4 μm with the Femto LDV. Neither laser showed significant thermal or mechanical damage in adjacent tissue layers of the stromal bed. The laser‐induced bubble layer was more pronounced with the IntraLase. CONCLUSION: The laser cuts of the IntraLase FS and Femto LDV femtosecond lasers were equally smooth and of excellent quality. The standard deviation of the flap thickness was small and equal in both systems.

Topographic- and wavefront-guided customized ablations with the NIDEK-EC5000CXII in LASIK for myopia

PURPOSE To assess refractive outcomes, changes in the total higher order root mean square (RMS) aberration, and changes in higher order wavefront aberrations after LASIK for myopia and myopic astigmatism with the NIDEK Advanced Vision Excimer Laser platform (NAVEX) using either an aspheric or topography-based or whole eye wavefront ablation algorithm. METHODS This was a retrospective study of 1459 eyes that underwent LASIK for myopia and myopic astigmatism. The mean preoperative spherical equivalent refraction was -4.68 diopters (D) (range: -0.50 to -9.63 D) with astigmatism up to -4.50 D. Treatments were classified into three categories depending on the type of ablation algorithm used--optimized aspheric transition zone (OATz) denoted eyes that underwent aspheric treatment zones; customized aspheric treatment zone (CATz) denoted eyes that underwent customized ablations based on corneal topography; and OPDCAT denoted eyes that underwent customized ablation based on the whole eye wavefront profile. Follow-up data are reported at 3 months (69%) and 12 months (17%) postoperatively. RESULTS Three months after LASIK, the predictability (10.5 D from target refraction) was 80% for OATz, 91% for CATz, and 76% for OPDCAT. Of all eyes, 96% were within +/- 1.0 D of intended refraction 3 months postoperatively and 100% after 12 months (87% +/- 0.5 D). In the aspheric and custom groups, a notable improvement of uncorrected visual acuity was noted between 3 and 12 months after LASIK. No eye lost >1 line of best spectacle-corrected visual acuity. Mean higher order RMS increased in all groups. CONCLUSIONS The data support that the treatment of myopia and myopic astigmatism is safe and effective with NAVEX. Customized ablation based on corneal topography rather than on total wavefront error was more predictable.

Virtual Eye: retinal image visualization of the human eye

In computer graphics, ray tracing produces realistic images of 3D scenes. Most work in the field has focused on modeling reflection to account for the interaction of light with different materials, deriving illumination algorithms to simulate light transport throughout the environment, and designing new optimization techniques. Additional work by (Cook et al., 1984) targeted simulation of depth of field and motion blur. Kolb and Hanrahan (1995) presented a realistic camera model that simulates aberration and radiation and produces images showing a variety of optical effects. Our challenge is to combine these two well-developed scientific fields to simulate human vision. We have begun to do so with the development of the Virtual Eye, a method to visualize retinal images. This article describes how the Virtual Eye simulates retinal perception and discusses its potential value in clinical applications such as planning and evaluating surgical techniques or new lens combinations.

Thermal and mechanical damage of corneal tissue after free-running and Q-switched mid-infrared laser ablation

Laser ablation of corneal tissue by mid-infrared laser radiation was studied in dependence of the laser wavelength and the pulse duration. The thermally and mechanically laser induced damage was determined by light microscopy (LM) and scanning electron microscopy (SEM). Fresh porcine eyes were irradiated with three different lasers: Er:YAG ((lambda) equals 2.94 micrometers ), Er:YSGG ((lambda) equals 2.79 micrometers ) and Ho:YAG ((lambda) equals 2.1 micrometers ). The experiments were performed with both, free running (pulse duration (tau) equals 200 microsecond(s) ) and Q-switched pulsed ((tau) equals 100 ns) lasers. The extent of thermally damaged tissue was found to be the same for Er:YAG and Er:YSGG lasers: 8 - 45 micrometers and 2 - 10 micrometers , with the long and the Q-switched pulses, respectively. The Ho:YAG laser induced coagulation zones were 200 - 600 micrometers thick in the free running and 40 - 80 micrometers in the Q-switched mode. The ablation efficiency of Er-lasers was between 4 and 13 times higher than that of the Ho:YAG.

Early results of nidek customized aspheric transition zones (CATz) in laser in situ keratomileusis.

PURPOSE Standard ablation profiles for myopia and myopic astigmatism are spherical in shape and usually induce spherical aberration, often resulting in glare, halo, and other night vision problems. New ablation algorithms with aspheric transition zones may help reduce the amount of induced spherical aberrations in refractive surgery. METHODS Between September and November 2002, 52 eyes were treated with bilateral laser in situ keratomileusis (LASIK) using a new ablation profile with customized aspherical transition zone (CATz). Results were analyzed from examinations performed 1 day, 1 and 3 months (if available) after surgery, and compared to a standard LASIK patient group. RESULTS Refractive outcome of patients was within +/- 0.50 D of intended correction in 72% on day 1, and 82% at 1 month after surgery. At 1 month after LASIK, mean spherical equivalent refraction was changed from preoperative mean -6.73 +/- 2.04 D to postoperative mean -0.43 +/- 0.80 D (range -2.00 to +1.50 D). No eye lost more than 1 line of visual acuity; 10% gained 1 line and 80% remained unchanged 1 month after surgery. The topographically visible effective optical zone size was larger than in comparable treatments with standard ablation profiles. Spherical aberration was reduced and no patient complained about night vision problems after surgery. CONCLUSIONS Customized aspheric transition zones may help reduce induction of spherical aberration in refractive surgical correction of myopia and myopic astigmatism.

ArF-excimer laser-induced secondary radiation in photoablation of biological tissue

Secondary radiation, emitted during and after the irradiation of corneal, dermal, and dental tissue by an ArF‐excimer laser (193 nm), was qualitatively and quantitatively characterized. Emission of secondary radiation was found in the range of 200–800 nm. The intensity of secondary radiation in the range of 200–315 nm (UVC and UVB) is ∼20% of the total intensity at high laser fluences (>2 J/cm2), and ∼50% at moderate laser fluences (<500 mJ/cm2); 10 μJ/cm2 in the UVC and UVB were measured at the sample surface, at fluences (<1J/cm2) which are of relevance for clinical procedures on soft tissues. In dental tissue processing, very high fluences (>5 J/cm2) are required. As a consequence, laser–induced plasma formation can be observed. Secondary radiation can be used as a visible guide for selective removal of carious altered tissue. The data we have found might be of assistance in estimating potential hazards for future mutagenic studies in the field.