Ophthalmic surgery and lasers最新文献

Background and objective: To provide a detailed description of the clinical features that are considered forerunners of symptomatic complications in asymptomatic degenerative retinoschisis, and to show that in selected cases at this stage prophylactic photocoagulation may be a better choice than mere observation.

Materials and methods: Forty-three eyes of 27 patients with asymptomatic bullous degenerative retinoschisis and outer layer breaks (OLBs) were studied through binocular indirect dynamic ophthalmoscopy and retinal biomicroscopy with the Goldmann 3-mirror lens, fundus drawings, and photographs where feasible. Argon laser treatment was performed on each eye: first, around the posterior border of the schisis to achieve a full-thickness retinal scar, and then on the schisis itself to promote scarring of the retinal pigment epithelium, thus avoiding retinal detachment. The follow up was 2 years minimum after treatment.

Results: OLBs usually involved the largest schises when multiple retinal splittings were present. Breaks were single in 18 eyes (peripheral in 16 and posterior in 2) and multiple in 25 (peripheral in 15 and posterior in 10). Overall, 23 eyes showed asymptomatic retinal detachment (schisis detachment): 20 with peripheral outer layer breaks and 3 with posterior breaks. Schisis detachment was localized to the schisis area in the first group, whereas it extended beyond the posterior boundary of retinoschisis in the latter. After treatment, no posterior progression of retinoschisis was noted nor did symptomatic retinal detachment arise. Only 1 eye had complications in the second step of the treatment that was later resolved with medical care.

Conclusion: Prophylactic Argon laser photocoagulation can be used safely in the asymptomatic stage of bullous retinoschisis with outer layer breaks to avoid the onset of acute symptomatic retinal detachment.

Background and objective: In both clinical and animal studies, it has been shown that repetitive short laser pulses can cause selective retinal pigment epithelium damage (RPE) with sparing of photoreceptors. Our purpose was to determine the ophthalmoscopic and angiographic damage thresholds as a function of pulse durations by using different pulsed laser systems to optimize treatment modalities.

Materials and methods: Chinchilla-breed rabbits were narcotized and placed in a special holding system. Laser lesions were applied using a commercial laser slit lamp, contact lens, and irradiation with a frequency-doubled Nd:YLF laser (wave-length: 527 nm; repetition rate: 500 Hz; number of pulses: 100; pulse duration: 5 micros, 1.7 micros, 200 ns) and an argon-ion laser (514 nm, 500 Hz, 100 pulses, 5 micros and 200 ms). In all eyes, spots with different energies were placed into the regio macularis with a diameter of 102 microm (tophat profile). After treatment, fundus photography and fluorescein angiography were performed and radiant exposure for ED50 damage determined. Speckle measurements at the fiber tips were performed to determine intensity peaks in the beam profile.

Results: Using the Nd:YLF laser system, the ophthalmoscopic ED50 threshold energies were 25.4 microJ (5 micros), 32 microJ (1.7 micros), and 30 microJ (200 ns). The angiographic ED50 thresholds were 13.4 microJ (5 micros), 9.2 microJ (1.7 micros), and 6.7 microJ (200 ns). With the argon laser, the angiographic threshold for 5 micros pulses was 5.5 microJ. The ophthalmoscopic threshold could not be determined because of a lack of power; however, it was > 12 microJ. For 200 ms, the ED50 radiant exposures were 20.4 mW ophthalmoscopically and 19.2 mW angiographically. Speckle factors were found to be 1.225 for the Nd:YLF and 3.180 for the argon laser. Thus, the maximal ED50 -threshold radiant exposures for the Nd:YLF were calculated to be 362 mJ/cM2 (5 micros), 478 mJ/cm2 (1.7 micros), and 438 mJ/cm2 (200 ns) ophthalmoscopically. Angiographically, the thresholds were 189 mJ/cm2 (5 micros), 143 mJ/cm2 (1.7 micros), and 97 mJ/cm2 (200 ns). For the argon laser, the maximal ED50 radiant exposure threshold was 170 mJ/cm2 angiographically.

Conclusion: The gap between the angiographic and the ophthalmoscopic thresholds for the 200 ns regime (4.5 times above angiographic ED50) was wider than for the 1.7 micros regime (3.3 times above the angiographic ED50). This would suggest the appropriate treatment would be 200 ns pulses. However, histologies have yet to prove that nonvisible mechanical effects increase with shorter pulse durations and could reduce the "therapeutic window." When comparing the thresholds with 5 micros pulses from the argon and Nd:YLF laser, it demonstrates that intensity modulations in the beam profile must be considered.

Objective: To determine the temporal relationship of microaneurysmal dosure following focal laser photocoagulation in diabetic macular edema.

Patients and methods: This prospective study included 25 eyes of 23 diabetic patients with clinically significant macular edema. Ten to 20 well-defined microaneurysms were preselected and marked on an enlarged photograph of the prelaser fundus fluorescein angiogram. These preselected microaneurysms were focally lasered and followed up angiographically at 48 hours, 1 week, 3 weeks, 6 weeks, and 12 weeks after photocoagulation. Thereafter, the average time span between photocoagulation and the closure of the microaneurysms was determined.

Results: The mean number of preselected microaneurysms at baseline was 18.24 +/- 3.51, which remained the same at 48 hours. However, the mean microaneurysmal count decreased to 11.76 +/- 2.65 (35% reduction) at 1 week, 9.12 +/- 2.53 (50% reduction), 7.12 +/- 2.26 (61% reduction), and 4.56 +/- 1.32 (75% reduction) at 3, 6, and 12 weeks, respectively. The majority of the microaneurysms (35%) closed between 48 hours and 1 week.

Conclusions: The microaneurysmal closure following focal laser photocoagulation is a delayed process. None of the preselected microaneurysms showed closure within 48 hours, and 75% of the preselected microaneurysms closed at the end of 12 weeks.

Objective: To determine the relative effectiveness of neodymium:YAG cyclophotocoagulation (NCYC) and pars plana modified Baerveldt implant (PPBI) surgery on intraocular pressure (IOP) control in eyes with neovascular glaucoma (NVG).

Participants: In this retrospective comparative group study, 30 patients with NVG treated with contact NCYC were compared with 18 patients who underwent PPBI. Patients groups were not statistically dissimilar with respect to the underlying disorder-causing angle and iris neovascularization, intraocular pressure, and patient's age.

Results: During a follow up of 6 months, an IOP control of > or = 6 and < or = 21 mm Hg was achieved in 23 eyes (76.6%) treated with NCYC compared with 17 eyes (94.4%) receiving PPBI (P = 0.13). Among eyes that had unsuccessful outcome in both groups, the proportions with persistently high IOP or hypotony were greater in the NCYC group than in the PPBI group. Based on our criteria, the cumulative proportion of failure in the NCYC group was 23.3% at 6 months as compared to 5.6% in the PPBI group. Seven eyes (23.3%) in the NCYC group lost light perception versus 1 eye (5.6%) in the PPBI group. The incidence of postoperative choroidal effusion (36%) was higher in the PPBI group.

Conclusions: This study suggests that in the management of NVG, PPBI surgery more frequently controls IOP in a medically acceptable range with less hypotony and greater preservation of visual acuity than NCYC.