Intraoperative conversion rate to a large, limbal opening in minimally invasive strabismus surgery (MISS).

BACKGROUND: To evaluate which factors predispose to an intraoperative conversion to the usual limbal approach in minimally invasive strabismus surgery (MISS). METHODS: This study included 451 consecutive patients operated on by one surgeon at Kantonsspital St Gallen, Switzerland, with minimally invasive rectus muscle surgery between February 2003 and December 2007. We evaluated the intraoperative conversion rate to the usual limbal approach over time, and performed a retrospective determination of date of surgery, age of patient, motility of the eye, primary or revision surgery, and the type and dose of surgery in 982 consecutive rectus muscle procedures. RESULTS: In 3.6% (35/982) of MISS procedures, an intraoperative conversion to a large, limbal approach was necessary. The overall conversion rate decreased over time, from 8.4% in 2003 to 0.4% in 2007. The multivariate regression analysis showed a significant negative influence between the date of surgery and the conversion rate (p < 0.005). Muscle resections were associated with a higher conversion rate (p < 0.001). The other evaluated factors had no significant influence on an intraoperative enlargement of the conjunctival opening. CONCLUSIONS: This study confirms the reliability of the new MISS technique, and shows a low conversion rate to the usual limbal approach. The conversion rate decreased over time with increasing surgical experience. Muscle resections were associated with a higher conversion rate, while the age of the patient, the motility of the eye, revision surgery and the dose of surgery had no significant influence on an intraoperative conversion.

Fluorescein leakage of the optic disc: time course in primary open-angle glaucoma.

PURPOSE: To identify and quantify the time course of fluorescein leakage of the optic nerve head in primary open-angle glaucoma (POAG) and controls. METHODS: Twenty patients with POAG (aged 58 +/- 10 years) and 14 controls (aged 51 +/- 12 years, p = 0.07) were included in a prospective study. Fluorescein leakage of the optic disc was quantified using digital image analysis. A new leakage ratio (fluorescence of the optic disc divided by fluorescence of the surrounding retina) was defined and fluorescein leakage was quantified at 7-8, 9-10, 11-12, and 13-14 min after injection of 2.5 cc sodium fluorescein (10%). RESULTS: The fluorescein leakage exhibited a significantly different time course with higher leakage ratio values in POAG compared to controls (7-8 min: 1.24 +/- 0.32 vs 1.16 +/- 0.12; 9-10 min: 1.37 +/- 0.37 vs 1.19 +/- 0.1; 11-12 min: 1.38 +/- 0.36 vs 1.24 +/- 0.13; 13-14 min: 1.44 +/- 0.36 vs 1.27 +/- 0.13; p = 0.004). The change in optic disc fluorescence from 7-8 min to 9-10 min was significantly higher in POAG compared to controls (0.13 +/- 0.09 vs 0.03 +/- 0.07; p = 0.002). CONCLUSION: The time course of fluorescein leakage is significantly different in POAG compared to controls. This might reflect damage of the optic disc vasculature related to increased vascular permeability.

Dronabinol and retinal hemodynamics in humans.

PURPOSE: To investigate the effects of oral cannabinoids on retinal hemodynamics assessed by video fluorescein angiography in healthy subjects. DESIGN: Interventional study. METHODS: In a self-experiment, the cannabinoid dronabinol (delta-9-tetrahydrocannabinol [THC]) was administered orally to eight healthy medical doctors (7.5 mg Marinol; Unimed Pharmaceuticals, Chicago, Illinois, USA). At baseline and two hours after dronabinol intake, intraocular pressure (IOP) was measured and retinal hemodynamics were assessed by fluorescein angiography. The retinal arteriovenous passage time was determined on the basis of dye dilution curves by means of digital image analysis in a masked fashion. RESULTS: Dronabinol resulted in a significant IOP reduction from 13.2 +/- 1.9 mm Hg to 11.8 +/- 2.0 mm Hg (P = .038). The retinal arteriovenous passage time decreased from 1.77 +/- 0.35 seconds to 1.57 +/- 0.31 seconds (P = .028). Systemic blood pressure and heart rate were not statistically significantly altered. CONCLUSIONS: Cannabinoids, already known for their ability to reduce IOP, may result in increased retinal hemodynamics. This may be beneficial in ocular circulatory disorders, including glaucoma.

Fluorescein filling defects and quantitative morphologic analysis of the optic nerve head in glaucoma.

OBJECTIVES: To evaluate absolute filling defects of the optic nerve head in normal tension glaucoma (NTG) and primary open-angle glaucoma (POAG) and to compare the filling defects with topographic analysis of the optic disc. METHODS: Twenty-five patients with NTG, 25 patients with POAG, and 25 age-matched controls were included. Fluorescein angiograms were performed by means of a scanning laser ophthalmoscope. The extent of absolute filling defects of the optic nerve head was assessed using digital image analysis of early-phase angiograms. Topographic measurements of the optic disc were acquired using the Heidelberg Retina Tomograph II. RESULTS: Absolute filling defects were significantly larger (P =.001) and were seen more often (P<.001) in patients with NTG (n = 18) and POAG (n = 19) compared with controls (n = 3). Rim area (P =.006), rim volume (P =.007), cup-disc area ratio (P =.008), linear cup-disc ratio (P =.005), maximum cup depth (P =.002), cup shape measure (P =.03), and nerve fiber layer thickness (P =.008) and cross-sectional area (P =.006) were significantly different between patients with glaucoma and controls. Absolute filling defects were significantly correlated with cup area (r = 0.31; P =.007), rim area (r = -0.38; P<.001), rim volume (r = -0.35; P =.002), cup-disc area ratio (r = 0.49; P<.001), linear cup-disc ratio (r = 0.48; P<.001), cup shape measure (r = 0.27; P =.02), and nerve fiber layer thickness (r = -0.33; P =.004) and cross-sectional area (r = -0.30; P =.009). CONCLUSIONS: Fluorescein filling defects of the optic disc are present in NTG and POAG. The extent of these filling defects is correlated with the morphologic disc damage.

Ocular pulse amplitude before and after cataract surgery.

PURPOSE: To investigate the impact of cataract surgery on the association of the ocular pulse amplitude (OPA) and intraocular pressure (IOP) with respect to the interpretation of OPA as an estimate of ocular blood flow. METHODS: Twenty-four patients with cataract were included in a clinical study. OPA was measured using dynamic contour tonometry (DCT, Pascal(®), SMT Swiss Microtechnology AG, Switzerland). IOP was measured by means of Goldmann applanation tonometry (IOP GAT) and DCT (IOP DCT). All measurements were performed before and one day after cataract surgery. RESULTS: At baseline, OPA was correlated to IOP GAT (r = 0.67, P = 0.0002) and IOP DCT (r = 0.82, P < 0.0001), but not to age or axial length. Postoperative OPA was correlated to IOP GAT (r = 0.67, P = 0.0002) and IOP DCT (r = 0.65, P = 0.0004). In 17 patients, IOP GAT decreased after surgery (IOP DCT n = 14), whereas an increase was apparent in seven patients (IOP DCT n = 10). The mean absolute deviation of IOP GAT pre- to post-surgery was 4.54 mmHg ± 2.47 (range 1-10 mmHg) and 5.4 mmHg ± 3.2 (range 1.1-13.1 mmHg) for IOP DCT. The changes of OPA were significantly correlated to changes in IOP GAT (r = 0.48, P = 0.017) and IOP DCT (r = 0.60, P = 0.001). IOP GAT and IOP DCT changes were not correlated to changes in corneal thickness. CONCLUSIONS: The OPA measured with the Pascal(®) device seems to be dependent on IOP changes. Particular caution should be taken in the interpretation of OPA in estimating pulsatile ocular blood flow.

Prolonged retinal arteriovenous passage time is correlated to ocular perfusion pressure in normal tension glaucoma.

BACKGROUND: The pathogenesis of normal tension glaucoma (NTG) might be related to impaired autoregulation of ocular blood flow. The purpose of the study is to evaluate retinal haemodynamics by fluorescein angiography and to correlate arteriovenous passage times (AVP) with ocular perfusion pressure in patients with NTG and controls. METHODS: Thirty-five patients with NTG without any topical treatment (mean age 53 +/- 11 years) and 35 age-matched controls (mean age 53 +/- 11 years) were included in this study. Retinal AVP was assessed by video fluorescein angiography using a scanning laser ophthalmoscope (Rodenstock, Germany). Dye dilution curves of temporal superior and inferior arterioles and venules were evaluated by digital image analysis. AVP was correlated to mean arterial blood pressure and ocular perfusion pressure. RESULTS: The AVP was significantly prolonged in patients with NTG compared to controls (1.82 +/- 0.57 versus 1.42 +/- 0.46, p = 0.002). Patients with NTG and controls showed no significant differences in intraocular pressure, mean arterial pressure and mean and diastolic ocular perfusion pressure. The AVP was significantly correlated to mean arterial pressure and mean and diastolic ocular perfusion pressure in patients with NTG (r = -0.54; p = 0.0006, r = -0.51; p = 0.002, r = -0.49, p = 0.002), but not in controls (r = -0.21; p = 0.23, r = -0.19; p = 0.27, r = 0.02, p = 0.93). CONCLUSIONS: Patients with NTG exhibit prolonged retinal AVP compared to controls. A significant correlation of retinal haemodynamics to mean arterial blood pressure and ocular perfusion pressure might reflect impaired autoregulation in NTG.

Fluorescein filling defects of the optic nerve head in normal tension glaucoma, primary open-angle glaucoma, ocular hypertension and healthy controls.

BACKGROUND: To evaluate fluorescein filling defects of the optic nerve head in normal tension glaucoma (NTG), primary open-angle glaucoma (POAG), ocular hypertension (OHT) and controls. METHODS: Forty patients with NTG (mean age 55 +/- 10 years), 40 patients with POAG (mean age 55 +/- 11 years), 40 patients with OHT (mean age 53 +/- 13 years), and 40 age-matched controls (mean age 54 +/- 11 years) were included in a prospective study. Video fluorescein angiograms were performed by means of a scanning laser ophthalmoscope. The extent of absolute filling defects of the optic nerve head was assessed (as a percentage of the disc area) using digital image analysis. Visual fields were tested by automatic static perimetry (Humphrey Field Analyzer, programme 24-2). RESULTS: Absolute filling defects were significantly larger in patients with NTG (12.2 +/- 15.5%) and POAG (12.9 +/- 13.1%) compared to patients with OHT (1.2 +/- 3.6%) and healthy controls (0.1 +/- 0.5%) (p < 0.0001). The area under the receiver operating characteristic (ROC) curve was 0.806 for NTG vs healthy controls, and 0.812 for POAG vs OHT. Absolute filling defects are significantly correlated to the global indices mean deviation (r = -0.63, p < 0.0001), pattern standard deviation (r = 0.61, p < 0.0001), and corrected pattern standard deviation (r = 0.62, p < 0.0001) and significantly correlated to horizontal (r = 0.50, p < 0.0001) and vertical (r = 0.53, p < 0.0001) cup-to-disc-ratios. CONCLUSIONS: Fluorescein filling defects of the optic disc representing capillary dropout are present in NTG and POAG. The extent of these filling defects is correlated to visual field loss and morphological damage. Fluorescein angiography may be useful in the diagnosis and management of NTG and POAG.

Asymmetric visual field loss and retrobulbar haemodynamics in primary open-angle glaucoma.

PURPOSE: To investigate interocular differences in retrobulbar flow velocities in patients with asymmetric glaucomatous visual field loss. METHODS: Twenty-five patients with primary open-angle glaucoma (POAG) and asymmetric visual field loss were included in this study. Asymmetric visual field loss was defined as a difference of the global index mean deviation (MD) >6 dB between the two eyes. Flow velocities (peak systolic velocity PSV and end-diastolic velocity EDV) and resistive indices (RI) of the ophthalmic artery (OA), central retinal artery (CRA), and nasal and temporal posterior ciliary arteries were measured by means of colour Doppler imaging. RESULTS: MD of eyes with more severe glaucomatous visual field loss was -18.3+/-7.8 dB vs -6.8+/-5.5 dB (p<0.0001) in the less affected eyes. The PSV and the EDV of the CRA and the PSV of the OA were significantly decreased in eyes with more severe glaucomatous visual field loss (CRA PSV: 7.6+/-2.0 cm/s vs 8.3+/-1.7 cm/s, p=0.04; CRA EDV: 2.24+/-0.5 cm/s vs 2.55+/-0.6 cm/s, p<0.007; OA PSV: 29.7+/-9.9 cm/s vs 32.7+/-11.5 cm/s, p<0.02). None of the other differences in velocity or resistive index were significant. CONCLUSIONS: Patients with asymmetric glaucomatous visual field loss exhibit asymmetric flow velocities of the CRA and OA. Patients with more severe damage display reduced flow velocities in retrobulbar vessels in POAG.

Fluorescein leakage of the optic disc in glaucomatous optic neuropathy.

PURPOSE: To identify and quantify the role of capillary leakage of the optic nerve head in digital fluorescein angiography in normal subjects and patients with open-angle glaucoma. METHODS: We conducted a prospective cross-sectional study in the Department of Ophthalmology of the Technical University of Aachen. Thirty patients with primary open-angle glaucoma (POAG) and 30 healthy age-matched subjects were included. Fluorescein angiograms were performed using the scanning laser ophthalmoscope. The fluorescence of the optic nerve head and the surrounding retina (ratio of leakage) was measured using digital imaging analysis in the late phases of the angiogram (9-10 min). RESULTS: The ratio of optic nerve head fluorescence to retinal reference loci was significantly increased (p=0.01) in patients with glaucoma (POAG, 1.38+/-0.34) compared with normal subjects (1.20+/-0.19). Intraocular pressure (p=0.0001), visual field indices (mean deviation, p<0.0001; pattern standard deviation, p<0.0001; corrected pattern standard deviation, p<0.0001), and cup to disc ratios (p=0.02) differed significantly between the groups. Age and systolic and diastolic blood pressure showed no significant differences between groups. CONCLUSION: Fluorescein angiography revealed significantly increased vascular leakage of glaucomatous optic nerve heads. An endothelial disruption and fluorescein leakage might be the result of mechanical stress at the level of the lamina cribrosa and/or a sign of ischemic damage. This measurement approach might enable us to judge the severity of optic nerve head leakage, and it is a potential way to evaluate therapeutic regimens.