Hand-held dynamic contour tonometry

The Alteration of Intraocular Pressure and Ocular Pulse Amplitude by Retrobulbar Anaesthesia-A Search for Risk Factors for Serious Complications Due to Retrobulbar Anaesthesia

Our goal was to assess the impact of retrobulbar anaesthesia on ocular pressure and perfusion development and to find out if there were systemic or biometric parameters of patients affecting them in order to understand the effect of retrobulbar anaesthesia better. Methods: Changes in intraocular pressure (IOP) and ocular pulse amplitude (OPA) using a dynamic contour tonometer (DCT) were noted before and after retrobulbar anaesthesia (RBA) in combination with five minutes of oculopression at 40 mmHg in 134 patients. Only results with a quality Q 1-3 were considered for further statistical analysis. Systemic and ophthalmic parameters were noted and their impact was tested using linear regression. Results: IOP decreased from 18.9 ± 7.2 mmHg to 15.4 ± 6.3 mmHg (n = 71, p = 0.001) after first RBA. The dosage of midazolam administered during premedication was found to increase IOP significantly after first RBA (B = 3.75; R2 = 0.38). Ocular pulse amplitude decreased significantly from 3.8 ± 1.7 mmHg to 3.0 ± 1.9 mmHg after first RBA (n = 72, p < 0.001). This change was found to be dependent on the presence of diabetes mellitus (n = 68, p = 0.048). Conclusions: IOP and OPA decrease after RBA and oculopression. Caution is needed with midazolam premedication due to potential IOP increase. Patients with diabetes and pre-existing retinal or optic nerve damage should consider alternative anaesthesia methods, such as eye drops or general anaesthesia, due to the observed decrease in OPA after RBA and oculopression.

Muscle Relaxants as a Risk Factor for Vis-à-tergo During Penetrating Keratoplasty: A Prospective Interventional Study

INTRODUCTION

This study aimed to investigate the influence of three muscle relaxants on intraocular pressure (IOP), ocular pulse amplitude (OPA), and vis-à-tergo (VAT) in patients undergoing penetrating keratoplasty (PKP) under general anesthesia.

METHODS

Ninety-five patients undergoing PKP were included in this prospective single-center interventional study. IOP and OPA were measured with a dynamic contour tonometer before and 5 min after onset of general anesthesia. Mivacurium (n = 30), atracurium (n = 35), and rocuronium (n = 30) were administered as nondepolarizing muscle relaxants. VAT was assessed 15 min after surgery had begun.

RESULTS

When mivacurium was used, IOP decreased by 2.2 mmHg [standard deviation (SD) ±2.2 mmHg; p < 0.001]. Atracurium decreased the IOP by an average of 5.8 mmHg (SD ±1.8 mmHg; p < 0.001) and rocuronium caused an IOP reduction of 7.2 mmHg (SD ±2 mmHg; p < 0.001). The relative IOP decrease was 12% with mivacurium, 29% with atracurium, and 37% with rocuronium (p < 0.001). OPA decreased by 0.6 mmHg with mivacurium (SD ±0.6 mmHg; 26%; p < 0.001), 1.3 mmHg with atracurium (SD ±1.3 mmHg; 40%; p < 0.001), and 1.2 mmHg with rocuronium (SD ±0.7 mmHg; 42%; p < 0.001). The relative OPA decrease was 26% with mivacurium, 40% with atracurium, and 42% with rocuronium (p < 0.001). VAT occurred in 36% of cases. Mivacurium was used in 77% of these cases, atracurium in 26%, and rocuronium in 6.6% (p < 0.001).

CONCLUSIONS

Mivacurium is associated with a higher risk of VAT during PKP. Therefore, atracurium or rocuronium may minimize complications in ocular surgery with large incisions.

[Reduction of intraocular pressure and ocular pulse amplitude during general anesthesia]

AIM

Measurement of the intraocular pressure (IOP) is an important tool for glaucoma diagnostics in children or patients with impaired cooperation. General anesthesia (GA) may significantly influence the IOP. This study aimed to evaluate the reduction of IOP during GA.

PATIENTS AND METHODS

The IOP was measured in 229 patients in a recumbent position in the non-operated eye prior to and 5 min after the beginning of GA with a dynamic contour tonometer (DCT).

RESULTS

The average IOP decreased from 19.9 ± 3.7 mmHg prior to GA to 14.1 ± 3.5 mmHg 5 min after beginning GA (p < 0.0001, IOP decrease 30 %). The GA caused a decrease of up to 2 mmHg in 6.1 %, 2-4 mmHg in 18.8 %, 4-6 mmHg in 21.0 %, 6-8 mmHg in 36.6 %, 8-10 mmHg in 13.6 %, 10-12 mmHg in 2.2 % and more than 12 mmHg in 1.7 % of the eyes. The ocular pulse amplitude (OPA) decreased from a mean of 3.4 ± 1.5 mmHg to 1.9 ± 1.0 mmHg (p < 0.0001, OPA decrease 41 %) under GA.

CONCLUSION

A significant decrease of IOP (mean 6 mmHg) occurs during GA and under extreme conditions up to 13.8 mmHg. A decrease of OPA of 1.5 mmHg should be taken into consideration for patients under general anesthesia and under extreme conditions up to 7 mmHg.

The ocular pulse amplitude as a noninvasive parameter for carotid artery stenosis screening: a test accuracy study

PURPOSE

To investigate a potential correlation between the ocular pulse amplitude (OPA; i.e., the intraocular pressure difference between the systolic and diastolic phases of the heartbeat) and the severity of carotid artery stenosis (CAS) and to test its role as a screening parameter for CAS during routine ophthalmic examination.

DESIGN

Test accuracy study.

PARTICIPANTS

Patients referred for color duplex ultrasound examination of the extra- and intracranial cerebral arteries were enrolled consecutively.

METHODS

We measured OPA on both eyes by dynamic contour tonometry. Multivariate analyses were performed with risk factors for CAS (age, total cholesterol, low-density lipoprotein, and triglycerides) to compare the diagnostic value of OPA measurements with other non- or minimally invasive screening parameters.

MAIN OUTCOME MEASURES

The difference between OPA measurements in patients with no (<50%) and patients with severe CAS (>70%) as well as the value of OPA measurements to predict the severity of CAS taking further risk factors of CAS into consideration.

RESULTS

One hundred thirty-four eyes of 67 patients (25 women, 42 men) with a mean age of 67±13 years (range, 25-87) were included. The means of the OPA values of those patients showing no CAS (<50%) differed significantly (P = 0.036) from those with a stenosis of ≥70%. The multivariate model produced a statistically significant odds ratio (0.46; P = 0.007) for CAS of ≥70%.

CONCLUSIONS

The results of the present study provide proof of principle that the OPA is reduced in patients with CAS and may be used as a noninvasive, inexpensive, readily available, and unconfounded screening parameter to detect CAS and possibly to reduce the incidence of stroke.

FINANCIAL DISCLOSURE(S)

The authors have no proprietary or commercial interest in any of the materials discussed in this article.