Reproducibility of nerve fiber layer thickness measurements using optical coherence tomography in silicone oil-filled eyes.

PURPOSE: To evaluate the reproducibility of nerve fiber layer (NFL) thickness measurements by optical coherence tomography (OCT) in individuals with silicone oil-filled eyes. METHODS: Eighteen patients who had undergone pars plana vitrectomy and silicone oil tamponade for retinal detachment were enrolled in a prospective, case-controlled clinical study. Each patient underwent OCT measurement of NFL thickness. Five repetitions of a series of scans on five separate occasions within a 0.5-month period were performed. Each eye was scanned at two different nerve head programs [radius (R) = 1.5 and R = 1.73]. The contralateral healthy eye was used as control. For each option (R = 1.5 and R = 1.73) and region (superior, inferior, temporal, nasal and overall mean), variance components and intraclass correlation coefficients (ICCs) were determined using repeated-measures regression. In these models, NFL thickness, as measured by OCT, was considered to have three variance components: intersubject, intervisit (within subject, between dates), and intravisit (within subject, within date). The ICC (intersubject variance/total variance) was used as a measure of reliability. RESULTS: The contralateral healthy eye provided a higher degree of reproducibility than the silicone oil-filled eye (p = 0.0001). Reproducibility was higher in a given eye on a given visit than from visit to visit. Reproducibility as measured by ICCs was as follows: R = 1.5, 0.54/0.30 (control eyes/silicone oil-filled eyes); R = 1.73, 0.51/0.30. CONCLUSIONS: Reproducibility results for OCT measurement of NFL thickness are different in healthy eyes and silicone oil-filled eyes. NFL thickness measurement is not reliable in silicone oil-filled eyes.

Treatment of retinal tears and lattice degenerations in fellow eyes in high risk patients suffering retinal detachment: a prospective study.

BACKGROUND/AIMS: Fellow eye prophylaxis for retinal detachment (RD) is still a controversial issue since opinions are not unanimous regarding the kind of lesions to be treated or the method of treatment. This prospective clinical study aimed to follow the course of vitreoretinal conditions in 150 high risk fellow eyes. METHODS: 150 consecutive patients with unilateral rhegmatogenous RD were included in this study. Inclusion criteria were good explorability of fellow eye retinal periphery and one of the following conditions in the fellow eye-aphakia, pseudophakia with capsulotomy, high myopia (>-6D), contralateral eye to a giant retinal tear. Prophylactic treatment (photocoagulation or scleral buckling) was performed in the presence of retinal tears and lattice degenerations. The state of the vitreous body was determined at the beginning of the study and at the end, when RD occurred. RESULTS: Follow up ranged from 36 to 132 months. 95 fellow eyes were subjected to laser treatment; five eyes underwent prophylactic surgical treatment. Initially, in the treated group posterior vitreous detachment (PVD) was present in 100 eyes (100% of cases), but as a complete PVD only in 42 of them (42%). 10 eyes in the treated group developed RD during the follow up period. In five of these cases the partial PVD had progressed and a retinal tear in a previously healthy area was the cause of the retinal detachment. In the other five eyes RD apparently developed from previously treated lesions. Progression of PVD was evident in four out of these five eyes. The untreated eyes had no visible degenerative lesions. During follow up eight eyes developed RD. These eyes had no PVD at the beginning of the study, but showed a partial PVD at the time of the diagnosis of RD. CONCLUSION: Fellow eyes with pre-existing retinal tears and PVDs can go on to retinal detachment in spite of laser prophylactic treatment. When PVD is not detectable or a partial PVD is present, the progression of posterior vitreous separation can account for retinal tears and RDs arising in formerly healthy areas.

In vitro viability of external eye microbial flora in hydroxy-propyl-methylcellulose.

The aim of this study was to verify the in vitro influence of various dilutions of a viscoelastic substance containing 2% hydroxy-propyl-methylcellulose (HPMC) on the viability of some microbial strains representative of the normal flora of the external eye. Pure reference strain cultures of Candida albicans, Pseudomonas aeruginosa, Propionibacterium acnes, Staphylococcus aureus, Staphylococcus epidermidis and a fresh clinical isolate of Proteus mirabilis were selected for this study. Serial twofold dilutions of 2% HPMC, prepared so as to obtain a final concentration ranging from 50 to 0.78% of the product in sterile saline solution (0.85% NaCl), were taken out with a pipette that delivered 1.0 ml per tube. One hundred microliters of the abovementioned microbial inocula, used for the evaluation of the positive control of the test organism, were dispensed into each tube. After 24 h of incubation, 100 microl of samples were taken from each tube and plated into the specific medium for the growth of the test organism. After 24-48 h of incubation, these agar plates were examined and the colony-forming-unit count of each test organism was compared to the corresponding total colony count, acting as a positive control, in order to determine the quantitative variation of the test organism grown in the presence of the viscoelastic compounds. C. albicans and P. aeruginosa showed a statistically significant increase in growth with HPMC dilutions varying from 1:2 to 1:16. P. acnes and P. mirabilis growth was significantly reduced by all dilutions except for the 1:128 one. S. epidermidis growth was also significantly reduced in the presence of HPMC dilutions varying from 1:2 to 1:64. S. aureus growth was not significantly influenced. The viability of P. aeruginosa in HPMC dilutions needs to be carefully considered because of the ability of this organism to induce endophthalmitis, and the possibility that during cataract surgery, a small amount of HPMC may be left in the eye, trapped behind the intraocular lens optic.

Echobiometry of the ocular layers at the posterior pole.

The thickness of the retina, choroid and sclera in relation to macular oedema (ME) can be measured using A scan echography. Ninety diabetic patients (180 eyes) divided into two groups with and without ME, respectively, were studied compared to a third group of 73 healthy controls (146 eyes). Statistical analysis of results showed good specificity (80%) and reasonable sensitivity (70%) of the echographic method in showing the presence of ME confirmed by fluorescein angiography.

Intraocular pressure changes after phacoemulsification and foldable silicone lens implantation using Healon GV.

The authors studied the intraocular pressure (IOP) changes after phacoemulsification with two different kinds of foldable silicone lens implantation using Healon GV as viscoelastic substance. One hundred patients undergoing cataract surgery were enrolled in this study. Inclusion criteria were: absence of ocular hypertension or glaucoma. Patients were randomly assigned to plate haptic (Silens PH, Domilens Chiron Vision, Lyon, France) or three-piece (CeeOntrade mark& ;920, Pharmacia spa, Milano, Italia) silicone intraocular lens (IOL) implantation. Following phacoemulsification and cortical aspiration, the capsular bag was reinflated with Healon GV. After foldable silicone IOL insertion residual Healon GV was removed from the anterior chamber. IOP was measured preoperatively and at 6, 24 h and 1 week postoperatively. Six hours postoperatively IOP was higher in the Silens PH group than in the CeeOn group (20. 85+/-5.42 vs. 18.88+/-2.95 mm Hg, p= 0.026). The difference was confirmed after 24 h (21.02+/-5.18 vs. 17.34+/-3.18 mm Hg, p < 0.01). Despite the medical treatment (acetazolamide 250 mg orally every 6 h), at the 24-hour control 2 eyes with plate haptic silicone lens showed IOP values higher than 30 mm Hg. Slitlamp examination showed in both eyes a shallowing of the anterior chamber together with the evidence of capsular bag hyperdistension and capsular block resulting from the occlusion of the circular anterior capsule opening by the plate haptic IOL. Residual Healon GV removal from the anterior chamber was performed. At 1-week control both eyes showed normalization of IOP. The use of a plate haptic silicone lens may be associated with a more consistent retention of Healon GV in the eye with trapping in the capsular bag. Retained viscoelastic may cause either trabecular meshwork blockage by viscoelastic substance or postoperative capsular bag hyperdistension, anteroplacement of the IOL optic and capsular block from occlusion of the circular anterior opening by the IOL optic.

In vitro Staphylococcus epidermidis growth in some viscoelastic substances containing sodium hyaluronate.

The aim of our study was to verify the in vitro growth of Staphylococcus epidermidis in various dilutions of some viscoelastic substances containing hyaluronic acid (Healon and Healon GV, IAL, Biolon). Serial twofold dilutions of each sterile viscoelastic substance, prepared so as to obtain a final concentration ranging from 50 to 0.78% of the product in sterile saline solution (0.85% NaCl), were taken out with a pipette that delivered 1.0 ml/tube. One hundred microliters of the S. epidermidis inocula, used for the evaluation of the positive control of the test organism, was dispensed into each tube. After 24 h of aerobic incubation at 37 degrees C, 100 microl of sample was taken out from each tube and plated into the specific medium for the growth of the test organism. After 24 h of incubation at 37 degrees C, these agar plates were examined and the colony-forming unit count of the test organism was compared to the corresponding total colony count, acting as a positive control, in order to determine the quantitative variation of the test organism grown in the presence of the viscoelastic compounds. For the lowest dilutions (from 1:2 to 1:8) statistically significant bacterial growth was detected in all tested viscoelastic substances. For the highest dilutions (1:64 and 1:128) Biolon and Healon GV showed a significant inhibition of S. epidermidis growth. A significant inhibition was also observed in the highest dilution (1:128) of Healon. In every dilution of IAL a statistically significant increase in bacterial growth was observed. It remains to be carefully considered whether S. epidermidis, accidentally penetrating the eye via the intraocular lens, could find a culture medium in a small amount of sodium hyaluronate left in the capsular bag behind the optic.

Effects of brimonidine 0.2% on blue-yellow perimetry of glaucomatous patients.

A cross-over double-blind study was performed to evaluate the effect of acute administration of brimonidine on the blue-yellow perimetry. Thirty patients with primary open-angle glaucoma were admitted. After brimonidine administration, IOP and pupil diameter showed a significant reduction (p < 0.01) without modification in systolic and diastolic blood pressure. Blue-on-yellow perimetry showed a significant reduction in CPSD from 3.81 +/- 1.60 to 2.71 +/- 1.92 (p < 0.05). This result suggests that brimonidine improves ocular perfusion via a reduction of IOP.