National Data and the Applicability to Understanding Rural and Remote Substance Use.

Responding to increases in overdose, addiction, and substance misuse, local public health experts need accurate data to plan and implement evidence-based prevention and treatment programs. In many countries, national data are the tool most readily available for these efforts. In the United States, the National Study on Drug Use and Health and the Treatment Episode Data Set are data sources used by states to determine the extent of addiction. This project sought to determine if these national data sources are applicable for local use in addiction prevention and program planning. NSDUH prevalence estimates from 2015 to 2019 were applied to the state population to determine the number of persons estimated to be substance users. The prevalence estimates were compared over time with the population data and substance use treatment admissions to assess the covariance and population change as an indicator of efficacy. The primary drivers of fatal overdose in Alaska are fentanyl, heroin, and methamphetamine. Fentanyl use was not assessed in either dataset. When applying the estimated use prevalence to the population, heroin users varied annually by 1777 persons and methamphetamine varied up to 2143 persons. These observed variances did not correspond with state population changes nor any trend in the persons seeking treatment for these substances. Our analyses do not support the use of NSDUH data for planning in rural and remote areas. The methods used in NSDUH data collection exclude ~ 20% of the state population, mostly Native persons, based on location and language. The annual prevalence estimates applied to the population did not correspond with changes in population nor changes in treatment. Fentanyl, which causes the most overdoses in Alaska and is of primary concern locally, was not assessed.

KOOS pain as a marker for significant knee pain two and six years after primary ACL reconstruction: a Multicenter Orthopaedic Outcomes Network (MOON) prospective longitudinal cohort study.

OBJECTIVE: The prevalence of radiographic osteoarthritis (OA) after anterior cruciate ligament reconstruction (ACLR) approaches 50%, yet the prevalence of significant knee pain is unknown. We applied three different models of Knee injury and Osteoarthritis Outcome Score (KOOS) thresholds for significant knee pain to an ACLR cohort to identify prevalence and risk factors. DESIGN: Multicenter Orthopaedic Outcomes Network (MOON) prospective cohort patients with a unilateral primary ACLR and normal contralateral knee were assessed at 2 and 6 years. Independent variables included patient demographics, validated Patient Reported Outcomes (PRO; Marx activity score, KOOS), and surgical characteristics. Models included: (1) KOOS criteria for a painful knee = quality of life subscale <87.5 and ≥2 of: KOOSpain <86.1, KOOSsymptoms <85.7, KOOSADL <86.8, or KOOSsports/rec <85.0; (2) KOOSpain subscale score ≤72 (≥2 standard deviations below population mean); (3) 10-point KOOSpain drop from 2 to 6 years. Proportional odds models (alpha ≤ 0.05) were used. RESULTS: 1761 patients of median age 23 years, median body mass index (BMI) 24.8 kg/m(2) and 56% male met inclusion, with 87% (1530/1761) and 86% (1506/1761) follow-up at 2 and 6 years, respectively. At 6 years, n = 592 (39%), n = 131 (9%) and n = 169 (12%) met criteria for models #1 through #3, respectively. The most consistent and strongest independent risk factor at both time-points was subsequent ipsilateral knee surgery. Low 2-year Marx activity score increased the odds of a painful knee at 6 years. CONCLUSIONS: Significant knee pain is prevalent after ACLR; with those who undergo subsequent ipsilateral surgery at greatest risk. The relationship between pain and structural OA warrants further study.

Meniscus treatment and age associated with narrower radiographic joint space width 2-3 years after ACL reconstruction: data from the MOON onsite cohort.

OBJECTIVE: To identify risk factors for radiographic signs of post-traumatic osteoarthritis (OA) 2-3 years after anterior cruciate ligament (ACL) reconstruction through multivariable analysis of minimum joint space width (mJSW) differences in a specially designed nested cohort. METHODS: A nested cohort within the Multicenter Orthopaedic Outcomes Network (MOON) cohort included 262 patients (148 females, average age 20) injured in sport who underwent ACL reconstruction in a previously uninjured knee, were 35 or younger, and did not have ACL revision or contralateral knee surgery. mJSW on semi-flexed radiographs was measured in the medial compartment using a validated computerized method. A multivariable generalized linear model was constructed to assess mJSW difference between the ACL reconstructed and contralateral control knees while adjusting for potential confounding factors. RESULTS: Unexpectedly, we found the mean mJSW was 0.35 mm wider in ACL reconstructed than in control knees (5.06 mm (95% CI 4.96-5.15 mm) vs 4.71 mm (95% CI 4.62-4.80 mm), P < 0.001). However, ACL reconstructed knees with meniscectomy had narrower mJSW compared to contralateral normal knees by 0.64 mm (95% C.I. 0.38-0.90 mm) (P < 0.001). Age (P < 0.001) and meniscus repair (P = 0.001) were also significantly associated with mJSW difference. CONCLUSION: Semi-flexed radiographs can detect differences in mJSW between ACL reconstructed and contralateral normal knees 2-3 years following ACL reconstruction, and the unexpected wider mJSW in ACL reconstructed knees may represent the earliest manifestation of post-traumatic osteoarthritis and warrants further study.

HIV risk behaviour knowledge, substance use and unprotected sex in men who have sex with men in Tallinn, Estonia.

This study examines HIV risk behaviour knowledge, substance use and unprotected sex in a sample of 79 men who have sex with men (MSM) in Tallinn, Estonia. Median age of the study population was 30 years (range 18-62 years); 35 were bisexual; 56 answered correctly to at least 10 out of 13 questions about HIV risk behaviours; 23 consumed more than seven alcoholic drinks in the week before the survey; nearly half (n=34) of the participants reported some illicit drug use in the past 12 months; 40 did not use a condom regularly in the 12 months preceding the survey, and 41 did not use a condom during their last sexual intercourse. Alcohol consumption in the week before the survey was negatively associated with condom use during last intercourse (RR 0.48; 95% CI 0.41-0.56). Use of illicit drugs varied significantly by ethnicity (p-value = 0.02). Multivariable analysis showed that higher consumption of alcohol in the week before the survey could be predicted by education, age group and sexual orientation. In conclusion, socio-demographic factors such as education, age, ethnicity and sexual orientation may affect HIV risk behaviour knowledge, sexual behavior and substance use among MSM in Estonia, and need to be taken into consideration for targeted HIV prevention.

A three-factor analytic model of the MADRS in geriatric depression.

OBJECTIVE: Major depression is a heterogeneous disorder, perhaps comprising several clinical subtypes or subgroups of symptoms. This study examined whether items on the Montgomery-Asberg Depression Rating Scale (MADRS) form distinct symptom subgroups among geriatric depressive patients that might form the basis of new outcome measures for tracking treatment effects. METHOD: The study examined a sample of 225 adults age 59 and older diagnosed with major depression. Factor analysis with oblique rotation was used to analyze baseline MADRS item scores. RESULTS: Three distinct interpretable factors were obtained; all ten items loaded <0.60 on a domain. The first factor, dysphoric apathy/retardation, comprised five items: apparent sadness, reported sadness, lassitude, reduced concentration, and inability to feel. Psychic anxiety, the second factor, included three items: inner tension, pessimistic thoughts, and suicidal thoughts. The third factor, vegetative symptoms, resulted from items involving sleep and appetite. CONCLUSIONS: The study produced three interpretable MADRS factors reflecting geriatric depression dimensions that may be useable to monitor focused treatment outcomes.

Arthroscopic identification of the popliteofibular ligament.

PURPOSE: The popliteofibular ligament has recently received recognition as a distinct structure with a significant contribution to posterolateral stability of the knee. The popliteofibular ligament plays a key role in stabilizing the posterolateral corner of the knee by limiting posterior translation, varus angulation, and external rotation (coupled and primary). During arthroscopic procedures, the senior author (R.D.P.) has observed vertically oriented fibers descending from the inferior surface of the intra-articular portion of the popliteus tendon at the popliteal hiatus. This study was performed to determine if these fibers were actually the popliteofibular ligament. TYPE OF STUDY: This is an anatomic study using a cadaveric knee model to identify the popliteofibular ligament both arthroscopically and through gross anatomic dissection. METHODS: Eight fresh human cadaveric knees were examined arthroscopically and the vertically oriented fibers from the inferior surface of the popliteus tendon at the popliteal hiatus were identified and marked with a suture using an arthroscopic suture passer. A dissection of the lateral side of the knee was then performed to identify the marked structure. RESULTS: In all specimens, the dissection revealed that the fibers identified and marked arthroscopically had firm attachments to the popliteus tendon superiorly and inserted distally into the posterior aspect of the fibular head. The labeled structure was, therefore, the popliteofibular ligament. The popliteofibular ligament bifurcated distally with 2 insertion sites onto the fibular head. CONCLUSIONS: From this study, we concluded that the vertically oriented fibers descending from the inferior surface of the intra-articular portion of the popliteus tendon at the popliteal hiatus identified during arthroscopy are indeed those of the popliteofibular ligament. It is hoped that this knowledge will lead to improved outcomes in the treatment of injuries to the posterolateral corner of the knee.

The effects of tibial rotation on posterior translation in knees in which the posterior cruciate ligament has been cut.

BACKGROUND: One of the most useful clinical tests for diagnosing an isolated injury of the posterior cruciate ligament is the posterior drawer maneuver performed with the knee in 90 degrees of flexion. Previously, it was thought that internally rotating the tibia during posterior drawer testing would decrease posterior laxity in a knee with an isolated posterior cruciate ligament injury. In this study, we evaluated the effects of internal and external tibial rotation on posterior laxity with the knee held in varying degrees of flexion after the posterior cruciate and meniscofemoral ligaments had been cut. MATERIALS AND METHODS: Twenty cadaveric knees were used. Each knee was mounted in a fixture with six degrees of freedom, and anterior and posterior forces of 150 N were applied. The testing was conducted with the knee in 90 degrees, 60 degrees, 30 degrees, and 0 degrees of flexion with the tibia in neutral, internal, and external rotation. All knees were tested with the posterior cruciate and meniscofemoral ligaments intact and transected. Repeated-measures analysis of variance was used for statistical analysis. RESULTS: At 30 degrees, 60 degrees, and 90 degrees of flexion, there was a significant increase in posterior laxity following transection of the posterior cruciate and meniscofemoral ligaments. At 60 degrees and 90 degrees of flexion, there was significantly less posterior laxity when the tibia was held in internal compared with external rotation. At 0 degrees and 30 degrees of flexion, there was no significant difference in posterior laxity when the tibia was held in internal compared with external rotation. CONCLUSIONS: After the posterior cruciate and meniscofemoral ligaments had been cut, posterior laxity was significantly decreased by both internal and external rotation of the tibia. Internal tibial rotation resulted in significantly less laxity than external tibial rotation did at 60 degrees and 90 degrees of knee flexion.

A comparison of preoperative imaging techniques for predicting patellar tendon graft length before cruciate ligament reconstruction.

Autogenous bone-patellar tendon-bone is commonly used as graft material for cruciate ligament reconstructions. If this type of graft is too long, graft fixation other than an interference screw may be required. If it is too short, selection of another type of graft may be necessary. If the length of the patellar tendon portion of the graft could be accurately predicted, preoperative planning could determine the adequacy of this graft and choice of fixation for the planned procedure. Using lateral radiographs with the knee flexed 30 degrees, standard magnetic resonance imaging, and magnetic resonance imaging with supplemental three-dimensional reconstructions, we measured the length of the patellar tendon in cadavers and then compared these measurements with the actual patellar tendon length measurements. Linear regression analysis resulted in r2 values of 0.80, 0.43, and 0.65 for lateral radiographs, standard magnetic resonance imaging, and magnetic resonance imaging with three-dimensional reconstructions, respectively. We concluded that lateral radiographs at 30 degrees of knee flexion are the most accurate predictors of patellar tendon length.

Pathology of ocular irritation with bleaching agents in the rabbit low-volume eye test.

Despite differences in the processes leading to tissue damage, the ocular irritation response to various surfactants, two concentrations of an acid and an alkali, and an acetone, alcohol, aromatic amine, and aldehyde has been shown to depend on the extent of initial injury. The purpose of this study was to assess the extent to which this fundamental relationship exists for bleaching agents in the rabbit low-volume eye test. Ten microl of sodium perborate monohydrate (NaBO3), sodium hypochlorite (NaOCl), 10% hydrogen peroxide (H2O2), and 15% H2O2 was applied directly to the cornea of the right eye of each rabbit. Macroscopic assessments for irritation were made 3 hours after dosing and periodically until 35 days. Light microscopic examinations were conducted on tissues obtained at 3 hr and on 1, 3, and 35 days. In vivo confocal microscopy (CM) and measurements of dead corneal epithelial cells and keratocytes at 3 hours and 1 day were used to characterize quantitatively initial corneal injury, while in vivo CM performed at 3 hours and 1, 3, 7, 14, and 35 days was used to characterize quantitatively the corneal changes over time. The changes with NaBO3 and NaOCl were consistent with mild irritancy. For both, corneal injury was limited to the epithelium and superficial stroma. The changes with 10% H202 and 15% H2O2 were consistent with severe irritation. Both concentrations affected the epithelium and deep stroma, with 15% H2O2 also at times affecting the endothelium. However, unlike other irritants previously studied, with 10% H2O2 and 15% H2O2 there was an incongruity between the extent of epithelial and stromal injury, with stromal injury being more extensive than epithelial injury. A similar, although less dramatic, effect was observed with NaBO3. Additionally, there was still significant keratocyte loss at 35 days with 10% H2O2 and 15% H2O2 even though the eyes at times were considered to be macroscopically normal. These observations highlight the need to include both epithelial and stromal components in an ex vivo or in vitro alternative assay. In conclusion, these results continue to support and extend our hypothesis that ocular irritation is principally defined by the extent of initial injury despite clear differences in the means by which irritants cause tissue damage. Importantly, we have identified unique differences in the ocular injury and responses occurring with bleaching agents that are important to consider in the development and validation of alternative ocular irritation tests to characterize a broad range of materials differing in type and irritancy.

Pathology of ocular irritation with acetone, cyclohexanol, parafluoroaniline, and formaldehyde in the rabbit low-volume eye test.

The ocular irritation responses to 11 different surfactants and two concentrations of acetic acid and sodium hydroxide have been shown to depend on the extent of initial injury, despite marked differences in the processes leading to tissue damage. The purpose of these studies was to determine the extent to which this fundamental relationship applies to other nonsurfactants. Ten microl of acetone (ACT). cyclohexanol (CY), parafluoroaniline (PF), or 37% formaldehyde (FA) was directly applied to the cornea of the right eye of each rabbit. Eyes and eyelids were macroscopically scored for signs of irritation beginning 3 hours after dosing and periodically until recovery or 35 days. Tissues were obtained for light microscopic examination after 3 hours and on days 1, 3, and 35. Initial corneal injury was characterized quantitatively at 3 hours and I day using in vivo confocal microscopy (CM) and by postmortem quantitation of dead corneal epithelial cells and keratocytes using a Live Dead Assay (L/D, Molecular Probes) and scanning laser CM. Corneal changes over time were characterized quantitatively using in vivo CM performed at 3 hours and 1, 3, 7, 14, and 35 days. The changes with ACT were consistent with mild irritation. Corneal injury was limited to the epithelium and superficial stroma, with the mean normalized depth of injury (NDI) being less than 10% with the majority of regions showing no stromal injury. Changes with CY and PF were consistent with moderate to severe irritation, and FA caused severe irritation. Specifically, corneal injury by CY and PF tended to involve the epithelium and anterior stroma, with the mean NDI being 10.4% to 23.8%, while injury with FA involved the epithelium, deep stroma, and at times the endothelium. Interestingly, with FA significantly less injury was observed at 3 hours with a dramatic increase in injury observed at 1 day and thereafter. In conclusion, these results continue to support and extend our hypothesis that ocular irritation is principally defined by the extent of initial injury despite clear differences in the means by which irritants cause tissue damage. We believe this approach can be applied to developing alternative assays based on injury to ex vivo eyes or injury to an in vitro corneal equivalent system.

A biomechanical comparison of posterior cruciate ligament reconstruction techniques.

Most posterior cruciate ligament reconstruction techniques use both tibial and femoral bone tunnels for graft placement. Because of the acute angle the graft must make to gain entrance into the tibial tunnel, abnormal stresses are placed on the graft that could lead to graft failure. An alternative technique for posterior cruciate ligament reconstruction involves placement of the bone plug from the graft anatomically on the back of the tibia (inlay), preventing formation of an acute angle at the tibial attachment site. We used six pairs of human cadaver knees to compare the biomechanical properties of these two techniques. One knee from each pair underwent tunnel reconstruction while the other knee underwent inlay reconstruction. There was significantly less anterior-posterior laxity in the inlay group when compared with the tunnel group from 30 degrees to 90 degrees of knee flexion and after repetitive loading at 90 degrees of knee flexion. Evaluation of the grafts revealed evidence of mechanical degradation in the tunnel group but not in the inlay group. The inlay technique resulted in less posterior translation with less graft degradation than did the tunnel technique for posterior cruciate ligament reconstruction.

Quantitative characterization of acid- and alkali-induced corneal injury in the low-volume eye test.

Defining the extent of initial injury has proven to be a useful basis for differentiating the ocular irritation potential of surfactants; however, the applicability of this method to other types of irritants has not been demonstrated. In the following studies we characterized the extent of corneal injury following exposure to different concentrations of acetic acid and sodium hydroxide (NaOH) in the rabbit low-volume eye test. Groups of rabbits received 3% acetic acid, 10% acetic acid, 2% NaOH, or 8% NaOH and were evaluated in vivo by macroscopic and in vivo confocal microscopic examination and postmortem using a live/dead staining kit and scanning laser confocal microscopic examination. Quantitative assessment of macroscopic scores, corneal surface epithelial cell size, corneal epithelial thickness, corneal thickness, depth of stromal injury, corneal light scattering (confocal microscopy through focusing, CMTF), and number of dead cells was conducted at various times, including the following: at 3 hours and at 1, 3, 7, 14, and 35 days. Based on macroscopic scores, the order of ocular irritancy potential was 3% acetic acid < 2% NaOH < 10% acetic acid < 8% NaOH. Evaluation of the quantitative in vivo and postmortem microscopic live/dead data revealed a slight decrease in epithelial thickness and an increase in dead epithelial cell numbers with 3% acetic acid. With 2% NaOH, significant focal changes in epithelial cell size, epithelial thickness, corneal thickness, and number of dead surface epithelial cells occurred at 3 hours and at 1 day, with injury to only a very small number of corneal stromal keratocytes, despite the presence of epithelial denudation. Changes with 10% acetic acid were similar to those noted with 2% NaOH at 3 hours and 1 day, but these changes were more diffuse and included stromal injury to a depth of 7.2 +/- 9.3% of the corneal thickness, with significant numbers of dead keratocytes. Eight percent NaOH, on the other hand, caused focally extensive injury that averaged 26.3 +/- 18.4% of the corneal thickness at 1 day, with significant light scattering from the cornea, which did not return to normal by 35 days postinjury. Overall, these data indicate that ocular irritation as a result of acetic acid and NaOH was associated with changes similar to those observed with surfactants (ie, slight irritants damage the corneal epithelium, mild and moderate irritants damage the corneal epithelium and anterior stromal cells, and severe irritants damage the corneal epithelium and deep stroma). To our knowledge, this is the first time that the ocular irritation potential for different types of materials (acid/alkali, surfactants) has been shown to be primarily dependent on the initial area and depth of injury.

Microscopic changes with acetic acid and sodium hydroxide in the rabbit low-volume eye test.

Differences in ocular irritancy have been hypothesized to reflect differences in the extent of initial injury. Although differences in the processes leading to tissue damage may exist, extent of injury is believed to be the principal factor determining final outcome of ocular irritation. Previous studies characterizing the pathology of surfactant-induced ocular irritation support this premise. The purpose of this study was to begin to determine the applicability of this premise in terms of nonsurfactants; we planned to accomplish this by assessing the ocular irritancy of different concentrations of an acid and an alkali. Ten microliters of 3 or 10% acetic acid (C2H4O2) or 2 or 8% sodium hydroxide (NaOH) were directly applied to the cornea of the right eye of each test rabbit. Untreated left eyes served as the controls. Eyes and eyelids were macroscopically examined for signs of irritation beginning 3 hours after dosing and periodically until recovery or day 35. Eyes and eyelids from animals in each group were collected for microscopic examination after 3 hours and on days 1, 3, and 35. The macroscopic and microscopic changes were consistent with slight (3% C2H4O2), mild (2% NaOH, 10% C2H4O2), and severe (8% NaOH) irritancy. The spectra of changes were similar to those previously reported for surfactants of differing types and irritancies. As with surfactants, as the extent of initial injury increased, the intensity and duration of the subsequent responses increased. These results indicate that our hypothesis also applies to nonsurfactants. The results also support our belief that the initial extent of injury associated with ocular irritation may be used to predict the subsequent responses and final outcome. Finally, our results further indicate that such an approach may be applicable to the development of alternative assays that are based on either injury to ex vivo eyes or injury to an in vitro corneal equivalent system.

Electrothermally-assisted capsulorrhaphy (ETAC): a new surgical method for glenohumeral instability and its rehabilitation considerations.

Knowledge of current surgical procedures and the effect they have on healing tissue is important when developing rehabilitation guidelines. Recently, clinicians have been asked to treat patients who have undergone Electrothermally-Assisted Capsulorrhaphy (ETAC) for shoulder instability. The ultimate tensile strength of the tightened capsule is unknown during various timeframes following surgery. The use of thermal energy to shrink the shoulder joint capsule initially causes weakness of the collagen ultrastructure. Rehabilitation following ETAC includes a period of relative immobilization, followed by controlled range of motion exercises. Exercises to strengthen shoulder muscles must be done in a manner that minimizes stress on the surgically treated capsule. This article provides a brief review of capsuloligamentous repair; describes the surgical procedure, its indications, contraindications, and the effect ETAC has on the healing tissue; and provides guidelines for rehabilitation following ETAC based on the evidence available and the authors clinical experience.

Second time around: evaluating the postoperative anterior cruciate ligament.

Anterior cruciate ligament (ACL) injuries are especially common in the younger athletic population. In 1998, more than 100,000 ACL reconstructions were performed. MR imaging examination has proved to be valuable in imaging and evaluating ACL reconstructions. This article reviews different surgical reconstruction procedures, indications for postoperative MR imaging, and the MR imaging appearance seen in routine ACL reconstructions and in complications associated with ACL reconstructions.

Characterization and application of thin film pressure sensors.

Data regarding intra-joint loads during range of motion is essential to understanding normal joint mechanics and pathology. The investigators configured and characterized the response of a 440 N range, 0.076 mm thick commercial thin film sensor to monitor joint loads through a range of motion. Following preconditioning, static and dynamic tests were performed to evaluate the sensor response under varied environmental conditions. Both tests utilized a fixture to align the sensor and applied load. Under conditions that included dry, wet, folded and kinked configurations, a static load of 100 N was applied and the sensor output monitored up to thirty minutes from the time of loading. A load of 400 N at 50 N/s was applied to the sensor to determine dynamic characteristics and calibration curves under the conditions described for static tests in addition to curved, hard and soft contact surfaces and sensor overload. Static kinked data was significantly different from the dry, wet and folded conditions. Dynamic data showed that inter-package variability was not significant but that differences between sensor packages and sensor configuration conditions were significant. To investigate applicability of these sensors to the field of orthopaedics, a cadaveric knee was instrumented with sensors to examine the role of the meniscus in load transmission and distribution across the knee. The sensors were placed bilaterally below each meniscus on the anterior, posterior and center of the tibial plateau. Sensor data were obtained at these locations during manually flexed range of motion for the intact, re-attached and lateral menisectomized conditions of the knee specimen.

Outcomes of postoperative septic arthritis after anterior cruciate ligament reconstruction.

Arthroscopically guided reconstruction of the anterior cruciate ligament is a common orthopaedic procedure. While many associated complications have been described in the literature, postoperative septic arthritis has received little attention. Although rare after anterior cruciate ligament reconstruction, septic arthritis can have devastating consequences. From a group of 831 consecutive patients, we report 4 (0.48%) who sustained septic arthritis. All patients had similar symptoms and were treated by the same surgeon in the same manner. All underwent immediate arthroscopic lavage, open incision, drainage of associated wounds, debridement with graft retention, and treatment with intravenous and then oral antibiotics. The patients underwent an average of 2.75 procedures after the diagnosis to eradicate the infection and restore knee motion. All patients were evaluated at an average of 3 years after surgery. We found that previous knee surgery and meniscal repair were risk factors for the development of postoperative septic arthritis. The infection was successfully eradicated, the ligament graft was preserved, and knee stability and mobility were adequately restored in all patients. However, the clinical outcome of these patients appeared to be inferior to that of patients who had undergone uncomplicated anterior cruciate ligament reconstruction. This inferior outcome appeared to be secondary to damage to the articular cartilage from the infection.

Quantitative measurement of acute corneal injury in rabbits with surfactants of different type and irritancy.

We have hypothesized that differences in ocular irritancy are related to differences in extent of initial injury and that, regardless of the processes leading to tissue damage, extent of injury is the primary factor that determines the final outcome of ocular irritation. In previous in vivo confocal microscopic (CM) studies we identified quantifiable differences in the extent of corneal injury occurring with four surfactants (three anionic, one cationic) known to cause different levels of ocular irritation and demonstrated that extent of initial corneal injury was related to the magnitude of cell death. The purpose of this study was to assess the applicability of this hypothesis to a broad sampling of surfactants. Specifically, initial corneal changes induced by seven different surfactants (one anionic, three cationic, three nonionic) were measured by in vivo CM and cell death was measured by an ex vivo live/dead assay. The right eye of each rabbit was treated by placing 10 microl of a surfactant directly on the cornea. Eyes were examined macroscopically and scored for irritation at 3 h and 1 day. At 3 h and 1 day, in vivo CM was used to examine the corneas and quantitate epithelial cell size, epithelial thickness, corneal thickness, and depth of stromal injury. At 3 h and/or at 1 day, corneas were removed and excised regions were placed in culture media containing 2 microM calcein AM and 4 microM ethidium homodimer. Using laser scanning CM, the number of dead epithelial and/or stromal cells in a 300 x 300 x 170-microm3 (xyz) volume of the cornea was determined. In vivo CM and live/dead assay findings revealed three surfactants to affect only the epithelium, three surfactants to affect the epithelium and superficial stroma, and one surfactant to affect the epithelium and deep stroma. Extent of initial corneal injury reflected level of ocular irritation, and magnitude of cell death was related to the extent of initial corneal injury. These findings are consistent with those for known slight, mild, and moderate to severe irritants, respectively. They suggest that our hypothesis is broadly applicable to surfactants. Additionally, we believe these surfactants should be included as part of a new "gold standard" for use in developing and validating in vitro tests to replace the use of animals in ocular irritancy testing.