Morphological and biochemical evaluation for rigid gas permeable contact lens extended wear on rabbit corneal epithelium
Ichijima, H.; Ohashi, J.; Petroll, W.M.; Cavanagh, H.D.
Clao Journal Official Publication of the Contact Lens Association of Ophthalmologists Inc 19(2): 121-128
1993
ISSN/ISBN: 0733-8902 PMID: 8495562 Document Number: 406947
We studied the effects of 24-hour wear of rigid gas permeable (RGP) contact lenses of varying oxygen transmissibilities on the rabbit cornea by measuring concomitant lactate dehydrogenase (LDH) activity in tears and by in vivo tandem scanning confocal microscopy (TSCM). We used a PMMA lens and rigid gas permeable (RGP) lenses that had Dk/L values ranging from 7 to 64 times 10-9 (cm/sec) (mL O-2/mL mmHg) and a uniform 0.15 mm thickness. After 6- and 24-hour contact lens wear, rabbit tear LDH activity increased according to the decrease in the Dk of RGP lenses. Tear LDH activity after 24 hours of lens wear was higher than after 6 hours. The observed increase in tear LDH activity was correlated with in vivo corneal epithelial morphology by tandem scanning confocal microscopy. The observed severity of desquamation and swelling of corneal epithelial cells was dependent upon the Dk/L-total of contact lenses worn, which directly related to the contact lens induced corneal hypoxia. Based on the results of this study, we conclude that: 1) a nap or accidental overnight wear of contact lenses with less than 20 times 10-9 Dk/L-total could cause severe corneal epithelial damage; 2) the ultra high Dk lens appeared to alter the ocular surface least; and 3) TSCM accompanied with tear LDH assay is an objective, non-invasive in vivo method to assess the effect of contact lens wear on the ocular surface over time at the cellular level.