The greater utilization of soft contact lenses calls for the development of new and objective methods of evaluating the optical performance of the different lens types, in situ. We used videokeratography to examine the surface topography of soft contact lenses that had been worn for more than 1 year on 27 eyes of 23 patients, and compared the resulting color-coded maps and topographic indices as well as contact lens-corrected visual acuities, with those obtained with new replacement lenses on the same eyes. Visual inspection of the color-coded maps revealed differences in the surface characteristics of the used and new lenses. Comparison of quantitative indices including the SAI (Surface Asymmetry Index), IAI (Irregular Astigmatism Index), SRI (Surface Regularity Index), and SDP (Standard Deviation of Powers) showed that asymmetry, surface irregularity, potential visual acuity (derived from the SRI), and corneal power distribution were significantly poorer with the used lenses than with the new (P = 0.0001). The videokeratoscope is useful for evaluating the soft contact lens surface in situ, as an indicator of optical quality; it also permits the objective evaluation of lens cleaning techniques.

Adolescent↗

PubMedDate not supplied

c-myc, ras p21 and p53 expression in pleomorphic adenoma and its malignant form of the human salivary glands.

Using an immunohistochemical study and an immunoblot analysis, the expression of cellular oncogenes of the human salivary glands such as c-myc, ras p21, and p53 tumor-suppressor gene in pleomorphic adenomas and its malignant form, carcinoma in pleomorphic adenomas was examined to evaluate a differential biological significance, in comparison with that in normal salivary gland tissues. Immunohistochemically, the c-myc product was detected in 42% of the pleomorphic adenomas and in 56% of the carcinomas in pleomorphic adenoma. The ras p21 expression was observed in 24% of pleomorphic adenomas, and in 50% of carcinomas in pleomorphic adenoma. The p53 protein was detected in 18% of the pleomorphic adenomas and in 67% of the carcinomas in pleomorphic adenoma. Although there was no significant difference between the benign and malignant forms for the expression of c-myc, a statistical significance in ras p21 and p53 expression was found between the pleomorphic adenoma and its malignant form (P < 0.05) and P < 0.001, respectively). An immunoblotting assay clearly demonstrated the expression of c-myc and p53 gene products in both the benign and malignant forms of the pleomorphic adenoma, and that of ras p21 in the malignant form. These results indicate that activation of c-myc and ras p21 proto-oncogenes and the involvement of p53 mutation may play important roles in the malignant transformation of salivary gland pleomorphic adenoma.

Adenoma, Pleomorphic↗

PubMedDate not supplied

Tear volume in relation to contact lens wear and age.

We examined the tear volume of the inferior conjunctival sac in relation to patient age and complications of contact lens wear using a special phenol red thread test. Records of patients who had undergone this test between 1984 and 1987 were reviewed. Based on the wet length of the thread, three groups were defined: 9 mm or less, 10-14 mm, and 15 mm or more. Those patients who showed consistent results over three or more separate testings were selected for this study. A total of 11,336 eyes met this criterion. A confidence interval of 95% was established as a basis for comparison of the groups. We found that the percentage of eyes with 9 mm or less of wet length increased with the age of the subject group. Likewise, the percentage of each age group with 15 mm or more of wet length steadily decreased among progressively older groups. Eyes wearing PMMA lenses with 9 mm or less of wet length showed the highest incidence of superficial punctate keratitis (SPK) and erosion. The group of eyes wearing high-DK lenses with 15 mm or more of wet length showed the lowest incidence of SPK and erosion.

Adolescent↗

PubMedDate not supplied

Swelling and deswelling of rabbit corneas in response to rigid gas permeable, hydrogel and elastomer contact lens wear.

We determined diurnal variation in corneal thickness in rabbits prior to and following overnight wear of: (i) selected rigid contact lenses with different Dk values; (ii) hydrogel lenses of low and high water content; and (iii) elastomer lenses. The degree of contact lens-induced corneal swelling observed during 24 hours of lens wear, and the rates of deswelling in the subsequent 24 hours, correlated well with the different oxygen transmissibilities of the individual RGP contact lenses. The greatest swelling (21.6 +/- 5.4%) followed the wear of PMMA lenses. The least swelling, 2.9 +/- 4.0%, followed the wear of rigid gas permeable (RGP) Menicon SF-P (melafocon A) lenses, a value nearly identical to the swelling observed in the morning following sleep without lenses, (0.0 +/- 3.1%). By contrast, low-water content hydrogel soft contact lens use was associated with drastic corneal deswelling rates (-15.1 +/- 4.5%) during the hours after lens wear. The difference between these and control corneas was significant by paired t-test (P less than 0.01). Eyes wearing high water content lenses had less deswelling than eyes with their low-water counterparts. Corneal swelling produced by elastomer lenses was similar to that seen with RGP lenses.

Animals↗

PubMedDate not supplied

The clinical significance of the oxygen permeability of contact lenses.

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Contact Lenses↗

PubMedDate not supplied

Adverse effects of contact lens wear in a large Japanese population.

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Contact Lenses↗