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eye irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
August 2018
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guideline
according to guideline
OECD Guideline 437 (Bovine Corneal Opacity and Permeability Test Method for Identifying Ocular Corrosives and Severe Irritants)
Version / remarks:
adopted: 09 October 2017
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Test material form:
liquid - solid: mixture of
Details on test material:
At room temperature, the substance can be either a primrose yellow solid or a liquid.
Specific details on test material used for the study:
Batch No.: 18052904
CAS No.: 92-50-2
Physical State: liquid at room temperature
Colour: primrose yellow (solid)
Storage Conditions: room temperature, protected from light
Retest Date: 28 May 2019
Safety Precautions: The routine hygienic procedures were sufficient to assure personnel health and safety.

Test animals / tissue source

Details on test animals or tissues and environmental conditions:
Preparation of the Corneas
The assay uses isolated corneas obtained as a by-product from animals freshly slaughtered at the abattoir A. Moksel AG, Buchloe, Germany. On the test day, fresh eyes were collected from the slaughterhouse and were transported in HBSS containing Pen/Strep on ice to the laboratories. Immediately after arrival of the eyes, cornea preparation was initiated. The eyes were carefully examined for defects and any defective eyes were discarded. The tissue surrounding the eyeball was carefully pulled away and the cornea was excised leaving a 2 to 3 mm rim of sclera. The isolated corneas were stored in a petri dish containing HBSS. Before the corneas were mounted in corneal holders (Duratec GmbH) with the endothelial side against the O-ring of the posterior chamber, they had been visually examined for defects and any defective cornea had been discarded. The anterior chamber was then positioned on top of the cornea and tightened with screws. The chambers of the corneal holder were then filled with RPMI 1640 medium (without phenol red) containing 1% FBS and 2 mM L-glutamine (complete RPMI 1640 medium). The posterior chamber was always filled first. The corneas were incubated for one hour at 32 ± 1 °C.

Calibration of the Opacitometer
The opacitometer (BASF-OP3.0, Duratec GmbH) was switched on at least 15 min before starting the calibration procedure. The filter holder was placed into the opacitometer and the readout was adjusted to 1000 ± 10 lux using the “Calibrate”-turning knob. For calibration the glass filter F2 was introduced into the filter holder. The readout lay in the range between 540-560 lux. To test the linearity of the measurement, two additional calibration filters, glass filter F3 and glass filter F4, were measured. For these glass filters, the opacitometer displayed values between 300-310 lux and between 95-105 lux.

Test system

unchanged (no vehicle)
yes, concurrent positive control
yes, concurrent negative control
Amount / concentration applied:
0.75 mL of the test substance
Duration of treatment / exposure:
10 minutes incubation at 32 ± 1 °C
Duration of post- treatment incubation (in vitro):
2 hours incubation at 32 ± 1 °C
Number of animals or in vitro replicates:
3 corneas for the test item
3 corneas as negative controls treated with physiological saline 0.9% NaCl
3 corneas as positive controls treated with ethanol 100%
Details on study design:
Treatment of the Corneas
After the equilibration period, the medium was removed from both chambers and replaced with fresh complete RPMI 1640 medium. An initial measurement was performed on each of the corneas using the opacitometer. Three corneas with illuminance readings approximately equivalent to the median illuminance of all corneas were selected as negative-control corneas. The illuminance of each cornea was read and recorded. Only corneas that had an initial illuminance reading I > I0/1.1651 lux were used for the assay. The medium was removed from the anterior chamber and replaced with the test item or control.
750 uL of the test substance or the control substance was introduced into the anterior chamber. After 10 minutes incubation at 32 ± 1 °C either the test substance or the control substance was removed and the epithelium washed at least three times with MEM (containing phenol red). Once the medium was free of test substance, the cornea was finally rinsed with complete RPMI 1640 medium (without phenol red). The anterior chamber was refilled with complete RPMI 1640 medium and an illuminance measurement was performed after 2 hours incubation at 32 ± 1 °C. Also, each cornea was observed visually and pertinent observations were recorded.
After the illuminance measurement was performed, the medium was removed from both chambers of the holder. The posterior chamber was refilled with fresh complete RPMI 1640 medium. 1 mL of a 4 mg/mL sodium fluorescein solution was added to the anterior chamber and the corneas were incubated for 90 minutes at 32 ± 1 °C. Then the medium from the posterior chamber was removed and its optical density at 490 nm (OD490) was determined, using a spectrophotometer (Jenway 6405 UV/VIS).
The change in opacity for each cornea was calculated by subtracting the initial opacity reading from the final opacity reading. These values were corrected by subtracting from each the average change in opacity observed for the negative-control corneas. The mean opacity value for each treatment was calculated by averaging the corrected opacity values of each cornea for a given treatment.

Results and discussion

In vitro

Irritation parameter:
in vitro irritation score
Run / experiment:
Vehicle controls validity:
not applicable
Negative controls validity:
Positive controls validity:
Remarks on result:
not determinable because of methodological limitations

Applicant's summary and conclusion

Interpretation of results:
study cannot be used for classification
No prediction can be made regarding the classification of the test substance 2-(N-ethylanilino)ethanol according to the evaluation criteria.
No prediction can be made regarding the classification of the test substance 2-(N-ethylanilino)ethanol according to the evaluation criteria. Further testing in another suitable method is required.