Epidemiology of Contact Lens–Related Inflammation and Microbial Keratitis: A 20-year Perspective

Comparative efficacies of contact lens disinfecting solutions against Pseudomonas aeruginosa

PURPOSE

The aim of the present study was to evaluate the disinfection properties of multipurpose contact lens disinfection solutions, based on the International Organization for Standardization (ISO) 14729 guidelines.

METHODS

Three lots of each of six multi-purpose solutions were tested as follows: Renu MultiPlus, Solo Care Aqua, All-Clean Soft, Contact All-in one Advanced, Hippia, Ginza multi-purpose solution and 0.9% normal saline solution were inoculated with the standard strain of Pseudomonas aeruginosa (ATCC 9027). The surviving bacteria were quantified at specified times. An average logarithm reduction in bacterial numbers at the manufacturer's minimum recommended disinfection time was determined and compared with the criteria for stand-alone disinfection products for each multi-purpose disinfection solution against each bacterial strain.

RESULTS

Renu MultiPlus, Solo Care, All-Clean Soft and Contact All-in one Advanced were effective in achieving a four logarithmic units reduction in the bacterial count; however, Renu MultiPlus and Solo Care Aqua resulted in the greatest reduction in bacterial numbers. The other solutions were not effective against Pseudomonas aeruginosa after specified times.

CONCLUSIONS

Generally, Renu MultiPlus, Solo Care Aqua, All-Clean Soft and Contact All-in one Advanced meet the ISO 14729 guidelines for stand-alone contact lens solutions.

Tear oxygen under hydrogel and silicone hydrogel contact lenses in humans

PURPOSE

To determine the tear oxygen tension under a variety of conventional and silicone hydrogel contact lenses in human subjects.

METHODS

Three hydrogel and five silicone hydrogel lenses (Dk/t = 17 to 329) were coated on the back surface with an oxygen sensitive, bovine serum albumin-Pd meso-tetra (4-carboxyphenyl) porphine complex (BSA-porphine). Each lens type was placed on the right eye of 15 non-contact lens wearers to obtain a steady-state open eye tear oxygen tension using oxygen sensitive phosphorescence decay of BSA-porphine. A closed-eye oxygen tension estimate was obtained by measuring the change in tear oxygen tension after 5 min of eye closure. In separate experiments, a goggle was placed over the lens wearing eye and a gas mixture (PO2 = 51 torr) flowed over the lens to simulate anterior lens oxygen tension during eye closure.

RESULTS

Mean open eye oxygen tension ranged from 58 to 133 torr. Closed eye estimates ranged from 11 to 42 torr. Oxygen tension under the goggle ranged from 8 to 48 torr and was higher than the closed eye estimate for six out of the eight lenses, suggesting that the average closed eye anterior lens surface oxygen tension is <51 torr. For Dk/t >30, the measured tear oxygen tension is significantly lower than that predicted from previous studies.

CONCLUSIONS

The phosphorescence decay methodology is capable of directly measuring the in vivo post lens PO2 of high Dk/t lenses without disturbing the contact lens or cornea. Our data indicate that increasing Dk/t up to and beyond 140 continues to yield increased flux into the central cornea.

Effects of contact lens multipurpose solutions on human corneal epithelial survival and barrier function

PURPOSE

To examine the effect of 4 commercially available contact lens multipurpose solutions (MPS) on the viability and barrier function of human corneal epithelial cells in vitro.

METHODS

Immortalized human corneal epithelial cells were exposed to 4 solutions, MPS A, B, C, and D with culture medium and Hanks' Balanced Salt Solution as controls. MTT assay was used to evaluate cell viability. ApopTag Fluorescein Apoptosis assay was used to detect cell death in situ. Corneal epithelial barrier function was evaluated by fluorescein permeability and immunofluorescent staining for tight junction proteins zonula occludens (ZO)-1 and occludin.

RESULTS

Corneal epithelial survival rates, evaluated by MTT assay showed no statistical difference between MPS A and the culture medium or Hanks' Balanced Salt Solution controls. MPS B, C, and D were associated with significantly less cell survival than the controls after exposure for 6 hrs (all P<0.01). Compared with the controls, the MPS A did not increase cell apoptosis, whereas the other 3 caused higher apoptotic rates. The epithelial permeability after exposure to MPS A was similar to controls and significantly lower than MPS B and MPS D (P<0.01). The tight junction proteins ZO-1 and occludin were well maintained after exposure to MPS A. In contrast, the expression of ZO-1 and occludin were largely disturbed by the other 3 MPS solutions.

CONCLUSIONS

The current marketed contact lens MPS may have negative effects on human corneal epithelial viability and barrier function. Among 4 MPS studied, MPS A maintains the cell viability and barrier function significantly better than other 3 marketed products.