Comparison of the new perimetric GATE strategy with conventional full-threshold and SITA standard strategies.

PURPOSE: A new, fast-threshold strategy, German Adaptive Thresholding Estimation (GATE/GATE-i), is compared to the full-threshold (FT) staircase and the Swedish Interactive Thresholding Algorithm (SITA) Standard strategies. GATE-i is performed in the initial examination and GATE refers to the results in subsequent examinations. METHODS: Sixty subjects were recruited for participation in the study: 40 with manifest glaucoma, 10 with suspected glaucoma, and 10 with ocular hypertension. The subjects were evaluated by each threshold strategy on two separate sessions within 14 days in a randomized block design. RESULTS: SITA standard, GATE-i, and GATE thresholds were 1.2, 0.6, and 0.0 dB higher than FT. The SITA standard tended to have lower thresholds than those of FT, GATE-i, and GATE for the more positive thresholds, and also in the five seed locations. For FT, GATE-i, GATE, and SITA Standard, the standard deviations of thresholds between sessions were, respectively, 3.9, 4.5, 4.2, and 3.1 dB, test-retest reliabilities (Spearman's rank correlations) were 0.84, 0.76, 0.79, and 0.71, test-retest agreements as measured by the 95% reference interval of differences were -7.69 to 7.69, -8.76 to 9.00, -8.40 to 8.56, and -7.01 to 7.44 dB, and examination durations were 9.0, 5.7, 4.7, and 5.6 minutes. The test duration for SITA Standard increased with increasing glaucomatous loss. CONCLUSIONS: The GATE algorithm achieves thresholds that are similar to those of FT and SITA Standard, with comparable accuracy, test-retest reliability, but with a shorter test duration than FT.

Dose-response relationship in inferior oblique muscle recession.

BACKGROUND: Recession of the inferior oblique muscle is a widely applied operation in the treatment of strabismus sursoadductorius. In this retrospective study, the dose-response relationship of this procedure was determined in order to improve surgical outcomes. In particular, the effect of an additional anteroposition of the operated muscle was analysed, as well as differences between short and long term results. METHODS: This retrospective study included 37 patients. Inclusion criteria were unilateral strabismus sursoadductorius and normal retinal correspondence. Exclusion criteria comprised previous ocular muscle surgery and any ocular or orbital disease. Nineteen patients had received an additional anteroposition of the muscle. Patients were examined at a tangent screen pre-operatively and 1 day post-operatively (short-term effect). Sixteen patients underwent an additional examination 3 months post-operatively (long-term effect). Changes of vertical, torsional and horizontal deviations, measured in different positions of gaze, were related to the surgical dose in order to calculate the dose-response relationship by linear regression analysis. RESULTS: Surgery always reduced preoperative deviations. The short-term vertical dose-response without/with anteroposition was 0.6 degrees /0.5 degrees per mm in primary gaze and 1.2 degrees /1.1 degrees per mm in adduction. The short-term torsional dose-response without/with anteroposition was 0.8 degrees /0.5 degrees per mm in primary gaze. Three months later, the vertical effect had remained constant, whereas the torsional effect had decreased to 0.6 degrees /0.1 degrees per mm. Variance was high, e.g. the standard deviation of the short-term effect for the vertical deviation in adduction was 2.5 degrees . CONCLUSIONS: Despite the large variation of effects, a dose-response relationship could be established, facilitating surgical planning. Large vertical deviations with small excyclodeviation are an indication for additional anteropositioning. The torsional effect of inferior oblique muscle recessions can diminish over time.

Relative afferent pupillary defect with normal vision and vertical strabismus--implications for pupillary pathway anatomy.

BACKGROUND: A relative afferent pupillary defect (RAPD) is usually a sign of visual dysfunction. Here, an unusual case of an RAPD combined with vertical strabismus but normal vision is described. Implications for pupillary pathway anatomy are discussed. METHODS: A 12-year-old girl with chronic headache was shown to have a midbrain tumour. She presented to us with intermittent diplopia. Examination included visual acuity, visual fields, pupillary function, anterior and posterior segments, and strabismus evaluation with the tangent screen. RESULTS: There was a right-sided pathologic RAPD but no afferent visual impairment. Isocoria was present in light and darkness. There was a right-sided strabismus sursoadductorius. CONCLUSIONS: A pathologic RAPD with normal vision can be caused by tumour compression of the contralateral pretectal nucleus or its afferent or efferent fibres. As an implication for pupillary pathway anatomy, our case suggests that there is equal distribution between crossing and non-crossing intercalated neurons. An associated strabismus can show a non-paralytic pattern.

Pattern ERG as an early glaucoma indicator in ocular hypertension: a long-term, prospective study.

PURPOSE: The conversion rate from untreated ocular hypertension (OHT) to glaucoma is only approximately 1% per year. Discrimination of nonconverters and potential converters would help reserve preventative treatment for those who need it and thus avoid unnecessary side effects and expenditure for those who do not. This prospective study was designed to assess the pattern electroretinogram (PERG) as an early indicator of dysfunction preceding glaucoma. METHODS: Ninety-five eyes of 54 patients with intraocular pressure > or =25 mm Hg (or > or =23 mm Hg with additional risk factors), normal visual fields, normal optic disc cupping, and visual acuity > or =0.8 were evaluated. Every 6 months during a median follow-up of 8.2 years, the PERG and visual fields were obtained besides other standard diagnostics. PERGs were recorded in steady state mode in response to checkerboard stimuli at 15 reversals/s, and the amplitudes in response to check sizes of 0.8 degrees and 16 degrees as well as the ratio of the amplitude of responses to 0.8 degrees over that to 16 degrees checks were determined. RESULTS: Glaucomatous visual field defects developed in eight eyes. For the PERG to 0.8 degrees checks and for the PERG ratio, analysis of the receiver-operating characteristic (ROC) yielded steadily increasing ROC areas before conversion (i.e., an increasing ability of the PERG to predict nonconversion or conversion). One year before conversion, the ROC area of the PERG ratio was 0.78; at a threshold of 1.06 this corresponded to a sensitivity of 80% and a specificity of 71%. CONCLUSIONS: The PERG can help to predict stability or progression to glaucoma in OHT at least 1 year ahead of conversion.

Changes of the lid fissure after surgery on horizontal extraocular muscles.

PURPOSE: To evaluate the effect of isolated medial and lateral rectus muscle surgery on eye lid position. DESIGN: Prospective, interventional case series. METHODS: We recruited 36 patients with strabismus with surgery performed on one horizontal extraocular muscle only. The width of the lid fissure and the position of the upper and lower lids in relation to the pupil center were measured before and 3 months after surgery. Regression analysis was used to evaluate the surgical effect. RESULTS: Recessions induced a widening of and resections a narrowing of the lid fissure, mainly because of changes of the lower lid position. The effect was statistically significant (change in lid fissure width, = 0.13 x surgical dose in millimeters; r(2) = .35; P = .0001). CONCLUSION: Patients should be informed about changes in lid fissure width after operations on horizontal extraocular muscles. If adequately integrated into the surgical plan, this side effect may alleviate pre-existing interocular differences in lid configuration.

Enzyme-assisted vitrectomy in enucleated pig eyes: a comparison of hyaluronidase, chondroitinase, and plasmin.

PURPOSE: Facilitation of vitrectomy by vitreolytic enzymes may be of great value in complicated or office-procedure vitreo-retinal surgery. In this study, we quantified and compared the effect of hyaluronidase, chondroitinase, and plasmin pre-incubation on vitrectomy rate and explored potential retinal damage. METHODS: Freshly enucleated pigs eyes were incubated (1 or 3 hours) with an intravitreally injected enzyme or control solution. Enzyme doses were 100 and 1000 U for hyaluronidase, 1 and 2 U for chondroitinase, 3 and 30 U for plasmin. The eyes were weighed before and after 10 minutes of one-port vitrectomy, the difference representing the amount of removed vitreous. Light microscopy was used to assess potential damage to the retina. RESULTS: All enzymes significantly increased the amount of removed vitreous at all doses and incubation periods. The highest increase was found with hyaluronidase 1000 U, 3 hours, the lowest with chondroitinase 1 U, 1 hour. Damage occasionally occurred to the internal limiting membrane and very rarely to the nerve fiber layer. No damage at all was seen in the 100 and 1000 U hyaluronidase (1-hour incubation) groups. CONCLUSIONS: Hyaluronidase, chondroitinase, and plasmin are good candidates for enzyme-assisted vitrectomy. Although retinal structural damage was very rarely seen, safety concerns will have to be investigated further.

Optic disk drusen.

Optic disk drusen occur in 3.4 to 24 per 1,000 population and are bilateral in approximately 75%. Disturbance in the axonal metabolism in the presence of a small scleral canal--regardless of eyelength--is considered responsible for the development. The drusen increase in size, becoming more visible with age due to continuing calcium apposition, and they are associated with visual field defects in a considerable number of patients. Patients do not usually notice these defects, despite their progressive nature over the years, and this indicates an insidious course. A correct diagnosis of optic disk drusen is mandatory, although effective treatment is not yet available. It is most important to differentiate optic disk drusen from papilledema in order to avoid unnecessary neurological examinations, but also to avoid overlooking genuine neurologic disorders. Because optic disk drusen can cause severe visual field defects, patients require individual consultation regarding work issues and whether or not to drive. Optic disk drusen can be accompanied by vascular complications as well. In some cases these vascular changes--for example, choroidal neovascularization--are treatable. Patients with optic disk drusen should undergo regular visual field, IOP, and nerve fiber layer examinations. In patients with deteriorating visual field and borderline IOP, we recommend antiglaucomatous therapy.