Corneal endothelial cells' protection against thermal injury: influence of ophthalmic viscoelastic substances in experimental study on rabbits.
OBJECTIVE
To quantify the maximal level of temperature and the time the maximal temperature is achieved and correlate the temperature parameters to the mean rate of endothelial cell loss after standardized ultrasound delivery assisted with four viscoelastic substances or different temperature of balanced salt solution (BSS).


METHODS
Thirty rabbits (60 eyes) were divided into six groups in which different viscoelastic substances or different temperature of BSS were used: Group 1, Viscoat; 2, Provisc; 3, soft shell technique; 4, Celoftal; 5, BSS 22 degrees C; and 6, BSS 4 degrees C. The same parameters of ultrasound energy were delivered by standard phaco tip introduced into pupillary plane. Thermocamera was employed for measurements of temperature parameters. Endothelium cell count was measured before surgery and 1 month postoperatively.


RESULTS
Maximal level of temperature was measured as follows: Group 5, 27.85 +/- 0.52 degrees C; Group 2, 27.75 +/- 0.54 degrees C; Group 3, 27.74 +/- 0.46 degrees C; Group 4, 27.25 +/- 0.60 degrees C; Group 6, 26.81 +/- 0.34 degrees C; Group 1, 26.52 +/- 0.48 degrees C (p<0.05). The time the maximal temperature is achieved was statistically shorter in Groups 5 and 6: 4 seconds, 5 seconds, respectively, p<0.0001, as compared with Group 2 (30 seconds), Group 3 (40 seconds), Group 1 (45 seconds), and Group 4 (50 seconds). The mean rate of endothelial cell loss was calculated as follows: Group 1, 4.35%+/-2.55%; Group 2, 8.43%+/-5.2%; Group 3, 6.25%+/-4.20%; Group 4, 6.53%+/-4.65%; Group 5, 14.3%+/-3.85%; and Group 6, 8.78%+/-4.45%.


CONCLUSIONS
Viscoelastic substances offer different levels of endothelial cell protection against temperature increase during phacoemulsification. The mean rate of endothelial cell loss correlates with the time the maximal temperature is achieved rather than with the value of maximal level of temperature. This implicates that surgical strategy should consider the choice of the most effective viscoelastic substances, particularly in difficult cases, e.g., hard nucleus, shallow anterior chamber, primary endothelial abnormality.
Jurowski
P
P
Department of Ophthalmology and Visual Rehabilitation, Medical University of Lodz, Poland. p.jurowski@poczta.wprost.pl
Goś
R
R
Owczarek
G
G
Gralewicz
G Z
GZ
D000818:Animals; D000867:Anterior Chamber / Q000503:physiopathology; D001672:Biocompatible Materials / Q000494:pharmacology; D001831:Body Temperature / Q000502:physiology; D019610:Cytoprotection / Q000187:drug effects; D004728:Endothelium, Corneal / Q000293:injuries / Q000473:pathology*; D005126:Eye Burns / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D006025:Glycosaminoglycans / Q000494:pharmacology*; D006358:Hot Temperature / Q000009:adverse effects; D006979:Hyperthermia, Induced / Q000009:adverse effects*; D009883:Ophthalmic Solutions / Q000494:pharmacology; D018918:Phacoemulsification / Q000009:adverse effects*; D011817:Rabbits; D013817:Thermography / Q000379:methods; D013821:Thermometers; D013997:Time Factors
D001672:Biocompatible Materials; D006025:Glycosaminoglycans; D009883:Ophthalmic Solutions