[Treatment of traumatic choroidal neovascularization with ranibizumab]. / Behandlung einer traumatischen chorioidalen Neovaskularisation mit Ranibizumab.

We report on a patient who had a choroidal rupture after contusion of the eyeball. Some months later choroidal neovascularization appeared which could be treated with ranibizumab. Although the patient was young several injections were necessary before the choroidal neovascularization vanished.

Biofilms formed on humic substances: response to flow conditions and carbon concentrations.

Stream biofilms are exposed to dynamic conditions of flow velocity and organic carbon availability. Thus, the aim of this study was to investigate the response of biofilms formed with and without humic substances (HSs) to an increase in flow velocity (0.04-0.10 ms(-1)) and HSs concentration (9.7+/-1.0 to 19.8+/-0.4 mgL(-1) C). The highest amount of biofilm, measured as volatile suspended solids and total countable cells, was observed at 0.10 m s(-1) without HSs. The bacterial community composition of the biofilm with HSs was characterized by sequences with high similarities (> or =97%) to the genus Dokdonella and to the genera Comamonas, Cupriavidus and, Ralstonia. Sequences retrieved from the biofilm without HSs presented high similarities (> or =97%) to the genus Sphingomonas and the genus Nitrosospira. Experimental results suggested that the presence of HSs under different concentrations and flow velocities did not significantly enhance the cell density of biofilms but influenced its microbial composition.

[Frequency of posterior vitreous detachment as determined intraoperatively in patients with an idiopathic epiretinal membrane]. / Intraoperativ festgestellte Häufigkeit der hinteren Glaskörperabhebung bei Patienten mit einer idiopathischen epiretinalen Membran.

INTRODUCTION: The prevalence of a posterior vitreous detachment in patients with an idiopathic epiretinal membrane is often exaggerated in the literature. This may make the surgeon become overconfident during vitrectomy. PATIENTS AND METHODS: 34 patients with an idiopathic epiretinal membrane (mean age 72.9 years) were vitrectomised. The membrane and with it the remaining vitreous were stained with Membrane Blue. RESULTS: The preoperative visual acuity was -0.6 +/- 0.176 logMar units. Visual acuity increased postoperatively to -0.3 +/- 0.252 logMar units after 372.6 days. A posterior vitreous detachment was found in 17 patients (50 %), whereas there was none in the remaining 50 %. There was no correlation between age and prevalence of vitreous detachment. DISCUSSION: The increase in visual acuity was very encouraging. In contrast to reports in the older literature one cannot expect to find a posterior vitreous detachment in patients with an idiopathic epiretinal membrane. This can be checked intraoperatively very easily with Membrane Blue. Such a check becomes more urgent as the posterior vitreous detachment cannot be achieved with 23-G vitrectomy as easily as with 20-G vitrectomy.

[Can the scattering of differences from the target refraction be avoided?]. / Lässt sich die Streuung der Abweichung von der Zielrefraktion verhindern?

INTRODUCTION: We wanted to check how the stochastic error is affected by two lens formulae. METHODS: The power of the intraocular lens was calculated using the SRK-II formula and the Haigis formula after eye length measurement with ultrasound and the IOL Master. Both lens formulae were partially derived and Gauss error analysis was used for examination of the propagated error. RESULTS: 61 patients with a mean age of 73.8 years were analysed. The postoperative refraction differed from the calculated refraction after ultrasound biometry using the SRK-II formula by 0.05 D (-1.56 to + 1.31, S. D.: 0.59 D; 92 % within +/- 1.0 D), after IOL Master biometry using the SRK-II formula by -0.15 D (-1.18 to + 1.25, S. D.: 0.52 D; 97 % within +/- 1.0 D), and after IOL Master biometry using the Haigis formula by -0.11 D (-1.14 to + 1.14, S. D.: 0.48 D; 95 % within +/- 1.0 D). The results did not differ from one another. The propagated error of the Haigis formula can be calculated according to DeltaP = square root (deltaL x (-4.206))(2) + (deltaVK x 0.9496)(2) + (DeltaDC x (-1.4950))(2). (DeltaL: error measuring axial length, DeltaVK error measuring anterior chamber depth, DeltaDC error measuring corneal power), the propagated error of the SRK-II formula according to DeltaP = square root (DeltaL x (-2.5))(2) + (DeltaDC x (-0.9))(2). The propagated error of the Haigis formula is always larger than the propagated error of the SRK-II formula. DISCUSSION: Scattering of the postoperative difference from the expected refraction cannot be avoided completely. It is possible to limit the systematic error by developing complicated formulae like the Haigis formula. However, increasing the number of parameters which need to be measured increases the dispersion of the calculated postoperative refraction. A compromise has to be found, and therefore the SRK-II formula is not outdated.

Characterization of biofilm formation on a humic material.

Biofilms are major sites of carbon cycling in streams. Therefore, it is crucial to improve knowledge about biofilms' structure and microbial composition to understand their contribution in the self-purification of surface water. The present work intends to study biofilm formation in the presence of humic substances (HSs) as a carbon source. Two biofilm flowcells were operated in parallel; one with synthetic stream water, displaying a background carbon concentration of 1.26+/-0.84 mg L(-1), the other with added HSs and an overall carbon concentration of 9.68+/-1.00 mg L(-1). From the biofilms' results of culturable and total countable cells, it can be concluded that the presence of HSs did not significantly enhance the biofilm cell density. However, the biofilm formed in the presence of HSs presented slightly higher values of volatile suspended solids (VSS) and protein. One possible explanation for this result is that HSs adsorbed to the polymeric matrix of the biofilm and were included in the quantification of VSS and protein. The microbial composition of the biofilm with addition of HSs was characterized by the presence of bacteria belonging to beta-Proteobacteria, Cupriavidus metallidurans and several species of the genus Ralstonia were identified, and gamma-Proteobacteria, represented by Escherichia coli. In the biofilm formed without HSs addition beta-Proteobacteria, represented by the species Variovorax paradoxus, and bacteria belonging to the group Bacteroidetes were detected. In conclusion, the presence of HSs did not significantly enhance biofilm cell density but influenced the bacterial diversity in the biofilm.

Life cycle assessment of wastewater treatment options for small and decentralized communities.

Sustainability has strong implications on the practice of engineering. Life cycle assessment (LCA) is an appropriate methodology for assessing the sustainability of a wastewater treatment plant design. The present study used a LCA approach for comparing alternative wastewater treatment processes for small and decentralised rural communities. The assessment was focused on two energy-saving systems (constructed wetland and slow rate infiltration) and a conventional one (activated sludge process). The low environmental impact of the energy-saving wastewater treatment plants was demonstrated, the most relevant being the global warming indicator. Options for reduction of life cycle impacts were assessed including materials used in construction and operational lifetime of the systems. A 10% extension of operation lifetime of constructed wetland and slow rate infiltration systems led to a 1% decrease in CO2 emissions, in both systems. The decrease in the abiotic depletion was 5 and 7%, respectively. Also, replacing steel with HDPE in the activated sludge tank resulted in a 1% reduction in CO2 emission and 1% in the abiotic depletion indicator. In the case of the Imhoff tank a 1% reduction in CO2 emissions and 5% in the abiotic depletion indicator were observed when concrete was replaced by HDPE.

Energy-saving wastewater treatment systems: formulation of cost functions.

Natural interactions between water, soil, atmosphere, plants and microorganisms include physical, chemical and biological processes with decontaminating capacities. Natural or energy-saving wastewater treatment systems utilize these processes and thereby enable a sustainable management in the field of wastewater treatment, offering low investment and operation costs, little or no energy consumption, little and low-skill labor requirements, good landscape integration and excellent feasibility for small settlements, especially when remote from centralized sewer systems. The objective of this work is the development of cost functions for investment and operation of energy-saving wastewater treatment technologies. Cost functions are essential for making cost estimations based on a very reduced number of variables. The latter are easily identified and quantified and have a direct bearing on the costs in question. The formulated investment and operation cost functions follow a power law, and the costs decrease with the increase of the population served. The different energy-saving wastewater treatment systems serving small population settlements, between 50 p.e. and 250 p.e., present associated investment costs varying from 400 Euro/p.e. to 200 Euro/p.e. and annual operation costs in the range of 70 Euro/p.e. to 20 Euro/p.e., respectively.

Did the spectrum of endophthalmitis change? A study comprising 13 years experience with operative therapy of endophthalmitis.

PURPOSE: The authors wondered whether the spectrum of endophthalmitis and the type of therapy had changed. METHODS: Files of patients who were operated upon for endophthalmitis between 1988 and 2000 were retrospectively analyzed. They were divided into Group 1 (operated upon 1988 to 1994) and Group 2 (1995 to 2000). RESULTS: Group 1 consisted of 83 patients (43.4% female, mean age 63.9 years), Group 2 of 108 (38.9% female, mean age 64.6 years). Bilateral endophthalmitis occurred in 8.4% of Group 1 patients (3.7% of Group 2 patients). Patients in both groups took on average 1.2 drug types against various internal diseases. The mean interval between first symptoms and presentation in the clinic was 45.7 days in Group 1 (19 days in Group 2; difference statistically significant). There were 63% (Group 1) (70% [Group 2]) cases of postoperative endophthalmitis, among them 58% (Group 1) (63% [Group 2]) after cataract extraction, 6% (Group 1) (5% [Group 2]) after glaucoma surgery, 20% (Group 1) (17% [Group 2]) endogenous and 17% (Group 1) (13% [Group 2]) post traumatic. In Group 2 slightly more Gram-negative bacteria were found. As an initial procedure the following were performed: vitrectomy (70% [Group 1], 88% [Group 2]), removal of crystalline lens (11% [Group 1], 10% [Group 2]), removal of pseudophakos (2% [Group 1], 12% [Group 2]), opening of posterior capsule (1% [Group 1], 9% [Group 2]), and anterior chamber irrigation (36% [Group 1], 43% [Group 2]), often combining procedures. There were significantly more vitrectomies and openings of the posterior capsule in Group 2. Neither the spectrum of secondary and tertiary procedures nor the reasons for such surgery differed in both groups. Neither visual acuity at initial presentation (0.1) nor at final follow-up (0.3) differed between the two groups. The rate of enucleation was less in Group 2 (6% versus 11%) although not statistically significantly. CONCLUSIONS: In Group 2 there were slightly more Gram-negative bacteria and the time interval between initial symptoms and presentation in the clinic had decreased. This can be interpreted as an increase in the severity of the endophthalmitis cases. The final visual acuity was identical in both groups, the enucleation rate improved.

[Phacoemulsification combined with cyclophotocoagulation]. / Phakoemulsifikation kombiniert mit Zyklophotokoagulation.

INTRODUCTION: Cyclophotocoagulation and phacoemulsification procedures may be combined to treat patients with glaucoma and cataract. To the best of our knowledge data concerning this combination have not been published as yet. PATIENTS AND METHODS: 28 eyes (23 patients, mean age 78.1 +/- 7.6 years) were operated upon between 9.04.2002 and 29.06.2004. Patients were compared to a group with phacoemulsification alone. RESULTS: A median of 15 laser flashes (duration 2000 ms, power 1750 mW) were applied. Complications at discharge from hospital (and after 6 weeks) were: corneal oedema 18 % (4.0 %), fibrinous reaction 25 % (7.1 %), hyphaema 7.1 % (0 %), 1 decentred IOL, 7.1 % capsular tear. Visual acuity increased statistically significantly from 0.3 to 0.5. Mean intraocular pressure decreased statistically significantly from 23.7 +/- 5.6 mmHg to 16.0 +/- 3.4 mmHg after 166 days. Success rate was 76 % after 6 weeks and 85.7 % after 166 days. The mean number of antiglaucomatous drugs could be reduced from 1.6 to 1.1 after 166 days. In the control group there was a transient corneal edema in 14.3 % (7.1 % cornea guttata), other complications were not found. CONCLUSION: The combination of cyclophotocoagulation and phacoemulsification is as successful as other combinations of cataract and glaucoma surgery with a similar or lower complication rates. Cyclophotocoagulation is cost efficient, can be repeated and is adaptable to the intraocular pressure.

Frequency of ocular hemorrhages in patients with subarachnoidal hemorrhage.

BACKGROUND: Vitreous hemorrhage (Terson's syndrome) and other intraocular hemorrhages have been reported in up to 40% of patients with subarachnoidal hemorrhage (SAH). Our objective was to determine prospectively the frequency of intraocular involvement and its relationship to the grade of SAH. METHODS: Seventy-four consecutive patients with SAH were prospectively examined. The patients were classified according to Hunt and Hess and ophthalmological examination was performed by an ophthalmologist. RESULTS: In all patients SAH was caused by a ruptured cerebral aneurysm. Intraocular hemorrhages were present in 28% of the patients, all of whom had retinal hemorrhages, which were detectable unilaterally in 45%, while 15% of these patients exhibited typical retrohyaloidal or vitreal hemorrhages. Ocular involvement was statistically more frequent in patients with a higher grade of SAH according to Hunt and Hess. CONCLUSIONS: Due to ocular involvement in more than a quarter of the patients with SAH and due to the fact that ocular involvement is related to the severity of SAH, screening of patients with SAH is recommended, especially when no reliable data about visual function are available. Early vitrectomy of vitreous hemorrhages provides a more effective rehabilitation.

Outbreak of Empedobacter brevis endophthalmitis after cataract extraction.

BACKGROUND: We present a series of patients who were operated upon on the same day by the same surgeon. All of those patients developed postoperative endophthalmitis due to Empedobacter brevis - a bacterium hitherto unknown in ophthalmologic literature. METHODS: Twelve patients were referred because of endophthalmitis after cataract extraction. The patients' files were studied and the intraoperative and postoperative outcome was analysed. RESULTS: Twelve patients (five male, seven female, mean age 75 years) presented 1-6 days after uncomplicated cataract extraction. Although some suffered from medical or ophthalmological diseases there was no association with the severity of the endophthalmitis. Eleven patients required vitrectomy, seven as primary procedure, one primary with extraction of the lens and three secondary after anterior chamber lavage and intravitreal antibiotics. In three cases vitrectomy had to be repeated together with extraction of the intraocular lens. There were two postoperative retinal detachments that required silicon oil and in one case an encircling band. Mean visual acuity rose from 0.02 to 0.47 by 9 months after operation. Empedobacter brevis was found in the anterior chamber and in the vitreous in all except one patient. CONCLUSION: In high-volume cataract surgery endemic endophthalmitis is always possible. Sources of infection may be anything from the lens to the sterilisation process, the latter being the primary suspect in our series. Prompt, adequate and (if necessary) aggressive treatment by vitreous surgery may lead to favourable results.

Internal limiting membrane ablation in pig eyes with the Er:YAG laser under perfluorodecalin.

PURPOSE: The aim of our study was to evaluate the in vivo feasibility of non-contact Er:YAG laser ablation of the internal limiting membrane (ILM), which is recommended for the treatment of macular holes. METHOD: Vitrectomy was performed in 16 eyes of 15 pigs. After perfluorodecalin filling, it was attempted to remove the ILM using a free-running fiber-guided Er:YAG laser (lambda=2.94 microm, pulse length 250 micros, repetition rate 1.7 Hz, radiant exposure 0.6-2.05 J/cm2). The eyes were enucleated either immediately (11 eyes, group 1) or 2 weeks after laser therapy (5 eyes, group 2). Furthermore, in one additional pig eye the retina was carefully treated with microforceps after vitrectomy to assess the damage produced by conventional techniques of ILM peeling. All eyes were examined histologically. RESULTS: Group 1: Nine eyes could be examined (problems with fixation in two eyes). In four of nine eyes, the ILM was either removed or detached, in one eye there was a superficial retinal hemorrhage, and in four eyes the ILM was still intact. In the latter cases, there was no intraoperative whitening or bleeding and no posterior vitreous detachment was present histologically. Group 2: Four eyes (problems with fixation in one eye) could be examined. The ILM was either removed or detached in three eyes. In one eye there was a superficial retinal hemorrhage. In one eye the ILM was not removed and there had neither been intraoperative whitening or hemorrhage nor histologically visible posterior vitreous detachment. In both groups, the nerve fiber layer in treated areas was thicker than in adjacent untreated retina. In one eye the retina was gently manipulated with microforceps in an attempt to perform ILM peeling. This led to damage to all layers of the retina. CONCLUSIONS: Removal of the ILM by Er:YAG laser is possible in vivo. However, the variability of the laser effects calls for further improvement such as a reliable indicator of ablation depth. In any case, any damage to the retina was lesser than that produced by microforceps.

Steady-state electroretinograms and pattern electroretinograms in pigs.

BACKGROUND: Electroretinograms (ERG) or pattern-electroretinograms (PERG) could be valuable for the quantification of potential damage to the pig retina by experimental erbium:YAG laser treatment. We therefore performed a normative study of ERGs and PERGs in pigs. METHODS: We recorded ERGs and PERGs under general anaesthesia in two experiments. In experiment 1 we examined eight eyes from six pigs of 20-25 kg body weight; in experiment 2 we examined four eyes from four pigs of 40-45 kg body weight. We used flash and checkerboard stimuli. In experiment 1, the stimulus parameters were mean luminance 48.3 cd/m2 for checkerboard stimuli, 96.6 cd/m2 for ERG, check sizes of 4 degrees, 8 degrees, and 16 degrees, temporal frequencies were 16 Hz for ERG and 8 rev/s for PERG. Three measurements were repeated after two weeks. Stimulus parameters for experiment 2 were luminance 175 (350) cd/m2, check sizes 1.6 degrees, 3.2 degrees, 6.7 degrees, and 16 degrees, temporal frequencies 6.3 Hz for ERG and 8 rev/s for PERG. Recordings were subjected to Fourier analysis. RESULTS: In experiment 1 the mean ERG amplitude was 1.02 +/- 0.89 microV with a coefficient of variation of 42% for repeat sessions. The mean PERG amplitudes were 0.53 +/- 0.25 microV for 16 degrees checks, 0.36 +/- 0.21 microV for 8 degrees, and 0.25 +/- 0.17 microV for 4 degrees. The mean coefficient of variation between two measurements was 103% for 16 degrees checks, 24% for 8 degrees, and 116% for 4 degrees. In experiment 2 the mean ERG amplitude was 9.72 +/- 3.96 microV. The mean PERG amplitudes were 0.77 +/- 0.50 microV for 16 degrees checks, 0.09 +/- 0.16 microV for 6.7 degrees, 0.07 +/- 0.13 microV for 3.2 degrees, and 0.08 +/- 0.09 microV for 1.6 degrees. CONCLUSIONS: It was possible to record ERGs and PERGs in pigs. However, the ERG amplitudes were small; PERG amplitudes were even smaller in both groups and cannot be reliably recorded. A problem for both ERG and PERG was the high intra-individual and interindividual variability. Therefore, only very extensive damage to the retina by vitrectomy or Er:YAG laser treatment might lead to a significant change in the ERG or PERG amplitudes.

Erbium: YAG laser ablation of retinal tissue under perfluorodecaline: determination of laser-tissue interaction in pig eyes.

PURPOSE: To evaluate the effect of Er;YAG laser on pig retina using a perfluorodecaline/retina interphase with the goal of precisely determining the extent of retinal tissue ablation. METHODS: Free running (tau = 250 microsec) Er:YAG laser pulses were transmitted through a zirconium fluoride (ZrF4) fiber guarded by quartz rod (d = 1000 microm). Laser pulses were applied to the retinal surface of enucleated pig eyes. Eyes were mounted in a specially designed rotating sample holder. The fiber probe was elevated 1.0 +/- 0.3 mm above the retinal surface with perfluorodecaline serving as transmitting medium. The laser energy was applied in a circular pattern with a radius of 3.0 mm. Radiant exposures were set to 1, 3, 5, and 10 J/cm2. RESULTS: Tissue ablation linearly increased with radiant exposure from 3.2 +/- 3.7 microm at 1 J/cm2 up to 40.9 +/- 12.9 microm at 10 J/cm2. Thermal tissue changes extended 70 +/- 10 microm vertically into the retina and 25 +/- 5 microm horizontally. Distortion of outer photoreceptor segments was noticed when the retina was exposed to radiant exposures of 3 J/cm2 or higher. CONCLUSIONS: The Er:YAG laser in combination with perfluorodecaline produced precise ablation of the pig retina, which suggests the feasibility of this technique for safe ablation of epiretinal membranes.

Long-lasting contamination of a vitrectomy apparatus with Serratia marcescens.

OBJECTIVE: To investigate the contamination of a vitrectomy apparatus with Serratia marcescens. DESIGN: Descriptive microbiological and molecular environmental study. SETTING: An 1,800-bed university hospital. RESULTS: S. marcescens was found inside the vitrectomy apparatus at the pressure transducer. Molecular typing by randomly amplified polymorphic DNA-automated laser fluorescence analysis and pulsed-field gel electrophoresis identified a single pattern for all strains isolated from the apparatus. Surprisingly, the contaminating strain was identical to two strains of S. marcescens isolated nearly 2 years earlier from two patients who were involved in a small outbreak of acute postoperative endophthalmitis following cataract surgery at another hospital. The emergency vitrectomies in these patients were performed at our hospital with the same apparatus that was found to be contaminated 2 years later. CONCLUSION: Performing a systematic environmental search for the assumed bacterial reservoir within the system of the vitrectomy apparatus finally made it possible to find and eliminate the nidus for the gram-negative rod. Molecular typing demonstrated that all isolates belonged to a single genotype, and revealed unexpectedly a link to two vitrectomies performed 2 years earlier. The data support the hypothesis that the source of the contamination was one of these patients, and thus contamination of the apparatus was present for almost 2 years.

Bacterial contamination of the pressure receiver of a vitrectomy machine.

On a routine sterility check, the authors found bacteria in their vitrectomy machine. Serratia marcescens was detected in the pressure receiver of a roller pump vitrectomy machine. The authors improved the machine by installing a millipore filter in front of the receiver that prevents bacteria from entering it without interfering with the pressure measurements. The origin of Serratia was probably a patient with endophthalmitis who was operated on long before the routine check. Although this appears to be the first report of a bacterial contamination of a vitrectomy machine, the results of testing show that this situation is indeed possible. The authors strongly recommend routine checks of the equipment and suggest mounting an antibacterial filter.

[Post-traumatic endophthalmitis with multiple water pathogens]. / Posttraumatische Endophthalmitis mit multiplen Wasserkeimen.

HISTORY AND SIGNS: A 37-y-old worker for a recycling company suffered from a corneal perforation by a wire which had been in contact with dirt and moisture. THERAPY AND OUTCOME: Initially, the typical signs of an endophthalmitis were missing so that we only irrigated and instilled antibiotics into the anterior chamber. However, later on two pars-plana vitrectomies became necessary. At each operation a bacteriological examination was performed and we found four different species-Pseudomonas aeruginosa. Klebsiella oxytoca, Aeromonas caviae, Flavobacterium odoratum. CONCLUSION: The latter two species are very rare in ophthalmology. This fact and some peculiarities in the clinical course of the patient's disease make him an unusual case. After unsuccessful irrigation of the anterior chamber vitrectomy ought to be performed immediately.

Diameter of the optic nerve in idiopathic optic neuritis and in anterior ischemic optic neuropathy.

PURPOSE: There is considerable overlap in the clinical profile of patients with idiopathic optic neuritis (ON) and anterior ischemic optic neuropathy (AION). We tested the hypothesis that the retrobulbar diameter of the optic nerve may be a criterion for the differential diagnosis between ON and AION. METHODS: The diameter of the optic nerve was measured by B-scan ultrasonography with the eye in an abducted position. Only patients with a unilateral optic neuropathy were included, 16 ON patients (mean age 24 years, 5 with and 11 without disc swelling) and 9 patients with AION (mean age 72 years). As controls for the ON patients 10 young normal subjects (mean age 25 years) and as controls for the AION patients 10 elderly subjects with eye problems not related to the optic nerve (mean age 76 years) were examined. RESULTS: In the ON patients with disc swelling the diameter of the optic nerve was 5.4 +/- 0.5 mm in the affected and 3.0 +/- 0.3 mm in the unaffected side. This difference was significant (Wilcoxon-test, p = 0.043). In the ON patients without disc swelling the diameter of the optic nerve was 4.4 +/- 0.4 mm in the affected and 3.0 +/- 0.3 mm in the unaffected side. This difference was significant (Wilcoxon-test, p = 0.003). In the AION patients the diameter of the optic nerve was 3.0 +/- 0.3 mm on the affected and 2.8 +/- 0.4 mm on the unaffected side. This difference was not significant (Wilcoxon-test, p = 0.093). Comparing the optic nerves with ON and AION to those of the controls, the diameter was significantly enlarged in the nerves with ON and normal in the nerves with AION (one factor repeated ANOVA). CONCLUSION: The diameter of the optic nerve is increased in ON without disc swelling and even more so in ON with disc swelling. The enlargement is probably due to edema of the nerve itself, not the surrounding subarachnoidal space. In AION, the diameter of the optic nerve is normal. Measuring the diameter of the optic nerve by B-scan ultrasonography is particularly useful in the differential diagnosis between ON with disc swelling and AION.