Ultrasound biomicroscopic study of the stability of intraocular lens implants after phacoemulsification cataract surgery.

PURPOSE: To assess the postoperative stability of three-piece intraocular lens (IOL) implants using ultrasound biomicroscopy (UBM). METHODS: This is a prospective observational cohort case series. Best-corrected visual acuity (BCVA) assessment, slit lamp examination, refraction and UBM evaluation were performed preoperatively and at 1, 6, 12, 18 and 24 months postoperatively. The anterior chamber depth (ACD) and IOL tilt angles at the 12, 6, 3 and 9 o'clock meridians were assessed. RESULTS: Twenty-one consecutive adult patients (21 study eyes) were recruited, but two dropped out from the study. The average age during cataract surgery was 71.7 years (60-83, SD 6.0). There were very slight changes in the refraction and IOL stability characteristics at all the postoperative follow-up time points. These were not found to be statistically significant, apart from the increase in ACD from months one (3.85 ± SD 0.29) to six (3.91 ± SD 0.26) (p = 0.01, paired t-test). CONCLUSION: There was a small but statistically significant increase in ACD between the first and sixth postoperative month, but ACD remained stable thereafter. This was not associated with any significant changes in refraction or BCVA. In contrast, IOL optic tilt remained statistically unchanged throughout the 24-month study duration.

Ultrasound velocity in heavy ocular tamponade agents and implications for biometry.

AIM: Heavy ocular tamponade agents have been shown to be an effective tamponade in complicated retinal detachments. Combined oil removal and cataract surgery may be performed and ultrasound (US) provides a reliable means to measure the axial length of eyes. The aim of this study was to evaluate the velocity of US in various tamponade agents. METHODS: Five tamponade agents (SO 1000, SO 5000, Oxane HD, Densiron 68 and F-Decalin) were studied in vitro. Time of flight (T(1)) was measured between a US transducer and the bottom of a container of the agent, and remeasured (T(2)) after reducing the separation by 1 cm. The speed of sound in the particular material was calculated from the difference between T(2) and T(1). Measurements were repeated over a range of temperatures from 18°C to 42°C. RESULTS: The speed of sound at 37°C ranged from 645 ± 8 m/s to 976 ± 10 m/s depending on the tamponade agent. In Densiron 68 and F-Decalin, the speed of sound was markedly reduced to 914 ± 10 m/s and 645 ± 8 m/s, respectively. The temperature dependence of speed of sound varied between -2.2 and -3.6 m/s per °C depending on the particular oil. With 95% confidence, the true speed is believed to lie within ± 5 m/s of these values. The deviation from intended refraction was between 0.38 to 30.15 D depending on the tamponade agent by using correction factor (CF) for SO 1000 cs. CONCLUSIONS: Variability in the velocity of US should be taken into account when performing biometry. Biometry machines should be adjusted for various tamponade media when calculating intraocular lens power.

Oxane HD and retinal detachment surgery in routine clinical practice.

BACKGROUND/AIMS: To assess the outcomes and complications of endotamponade with Oxane HD following retinal detachment repair. METHODS: Retrospective consecutive case series of inferior retinal detachment with Oxane HD endotamponade within a 3-year period. RESULTS: Case notes for 18 eyes of 18 patients were reviewed. Four (22.2%) were total retinal detachments and 13 (72.2%) had proliferative vitreoretinopathy. The mean Oxane HD endotamponade and follow-up durations were 27 ± 38 and 66 ± 39 weeks, respectively. The eventual anatomic success rate was 77.8%, but without any significant difference in vision. Postoperative complications occurred in 14 (77.8%), including emulsification (6 eyes; 33.3%), epiretinal membrane (5 eyes; 27.8%), and posterior capsular opacification (4 eyes; 22.2%). Of the 14 eyes requiring intraoperative perfluorodecalin, 12 (85.7%) developed complications; all 5 (100%) eyes with direct exchange of perfluorodecalin with Oxane HD developed complications. CONCLUSION: Although useful for inferior retinal detachments, Oxane HD was associated with a relatively high rate of emulsification when compared to other series. Our series also suggests that prior use of perfluorodecalin intraoperatively, and in particular direct exchange of perfluorodecalin with Oxane HD, may be associated with an increased risk of intraocular complications.

Correlation between corneal and scleral thickness in glaucoma.

PURPOSE: To assess the correlation between central corneal thickness (CCT) and anterior scleral thickness (ST) in patients of primary open-angle glaucoma (POAG), normal tension glaucoma (NTG), and ocular hypertension (OHT). PATIENTS AND METHODS: Consecutive patients with OHT, POAG, NTG, and normal individuals were recruited. CCT was measured by ultrasonic pachymetry, whereas ST was measured using ultrasonic biomicroscopy at the temporal quadrant, 2 mm posterior to the scleral spur. Investigators were masked to the diagnosis and CCT/ ultrasonic biomicroscopy data. Correlation between mean CCT and ST was analyzed. RESULTS: One hundred and twenty-four subjects (31 with OHT, 31 with POAG, 31 with NTG, and 31 normal individuals) were enrolled. The CCT (OHT 548.06+/-30.45 microm; POAG 519.39+/-42.95 microm; NTG 505.81+/-27.23 microm; controls 529.90+/-43.40 microm) was found to be thicker in patients with OHT than POAG (P=0.004) or NTG (P<0.01). There was also a difference in CCT between NTG and control eyes (P=0.012). The ST (OHT 755.03+/-69.58 microm; POAG 738.45+/-66.83 microm; NTG 708.74+/-71.58 microm; controls 724.45+/-73.27 microm) was thicker in the OHT group than in NTG patients (P=0.012). No significant difference in ST was found among other groups. Among subgroups, the correlation between CCT and ST was found only among the patients with NTG (r=0.440, P=0.013). However, no correlation was seen between CCT and ST in patients with OHT, POAG, and controls. CONCLUSIONS: There is a correlation between CCT and ST among the NTG group but no correlation was seen among OHT, POAG, and controls.

Grading of pars planitis by ultrasound biomicroscopy--echographic and clinical study.

OBJECTIVE: To determine the value of high frequency ultrasound biomicroscopy (UBM) in the assessment of pars planitis, and in particular to correlate UBM findings and ophthalmoscopy findings. METHODS: All patients with pars planitis were identified from the uveitis database of the Department of Ophthalmology, University of Aberdeen. Fifteen consecutive patients (age 14-52 years) underwent complete ophthalmological examination. UBM was performed at a sound frequency of 50 MHz on 17 eyes of 10 patients to determine the extent of disease. UBM findings were evaluated by two investigators in a blinded fashion and graded from 0 to 3 according to the following grading criteria: 0=no cells, 1=mild cells, 2=marked cells, 3=organization of cells. Opthalmoscopy findings were also graded using the same criteria. UBM and ophthalmoscopy findings were independently graded and compared. RESULTS: We found a good inter-observer correlation for the UBM grading of pars planitis (rho=0.86). There was no significant difference in the grading of pars planitis by indirect ophthalmoscopy as compared to grading by UBM (P>0.05). CONCLUSION: UBM appears to be a valuable and reliable diagnostic technique for the evaluation of patients with pars planitis and may be useful especially in patients with media opacities to diagnose and/or monitor efficacy of treatment.