Peripheral corneal infiltrates associated with contact lens wear

PURPOSE

A retrospective study was performed to review the clinical characteristics of peripheral corneal infiltrates in contact lens wearers.

METHODS

The charts of all contact lens patients with peripheral corneal infiltrates 1.5 mm or less in size who presented to the office from 1987 to 1994 were reviewed.

RESULTS

The epidemiological and clinical characteristics of peripheral corneal infiltrates associated with contact lens wear were reviewed in 52 patients (64 infiltrates). Forty-four patients presented with a single infiltrate, while the remaining 8 patients had multiple infiltrates. While there was no predilection for a specific quadrant of the cornea, when a subgroup of patients who wore extended wear lenses was analyzed, 19 of the 40 infiltrates were located in the superior quadrant. Forty percent of the patients were wearing disposable extended wear contact lenses, 21% were wearing conventional extended wear lenses, 33% were wearing conventional or frequent replacement/disposable daily wear contact lenses and 6% were wearing rigid gas permeable lenses. The majority of patients had minimal conjunctival inflammation, an anterior stromal cellular reaction and minimal anterior chamber activity. A subgroup of 16 patients had corneal cultures of their infiltrates. In this group, 8 of the 16 had positive cultures. All patients had a resolution of the infiltrates without complications and the majority were refitted to daily wear soft or rigid contact lenses.

CONCLUSION

Peripheral corneal infiltrates in contact lens wearers appears to be more common in patients wearing extended wear soft contact lenses. While often considered "sterile" in the literature, a significant number have been shown to be culture-positive. The organisms that have been associated with peripheral infiltrates appear to be less "pathogenic" than those that have been reported to be associated with central corneal ulcer. However, it is probably advisable that patients with peripheral corneal ulcers secondary to contact lens wear should be initially treated with topical antibiotics.

Extended wear soft contact lenses induce corneal epithelial changes

The purpose of this study was to determine the corneal epithelial alterations induced by various types of contact lenses. By employing the specular microscope, the corneal epithelia of 60 patients who had worn contact lenses for more than 1 year were re-examined along with 15 myopic controls. The morphological changes in aphakic patients who changed from extended wear soft to extended wear rigid gas permeable lenses were also studied. The mean cell area of the corneal epithelium was 621.5 (SD 92.5) microns 2 for daily wear rigid gas permeable lenses (n = 15), 645.8 (98.1) microns 2 for daily wear soft lenses (n = 15), and 634.7 (88.6) microns 2 for extended wear rigid gas permeable lenses (n = 15), none of which differed significantly from the control value of 610.5 (98.1) microns 2. Only the extended wear soft lens group (n = 15) showed significantly enlarged epithelia (806.1 (50.1) microns 2, p < 0.01 versus the other groups). The epithelium partially returned to normal after changing from extended wear soft lenses to extended wear rigid gas permeable ones. The corneal epithelium showed increased cell area only with extended wear soft contact lenses which are known to pose a risk for corneal infection.

Effects of long term extended wear of PMMA lenses on corneal function: a case report

BACKGROUND

Recent studies have shown that some long-term PMMA contact lens wearers who are presumably exposed to hypoxia can develop modest but permanent changes in corneal structure and function. What is not known is the corneal effects that may result from severe and long-term exposure to an hypoxic environment. This case report is presented to illustrate an extreme example of the effects of the cornea from prolonged exposure to hypoxia.

METHODS

A 37-year-old male who had worn PMMA lenses on a 2-week extended wear basis for 20 years was examined in the laboratory to assess changes in corneal structure and function. Function was determined by monitoring the rate at which the cornea recovered from induced edema and is expressed as a percent recovery per hour (PRPH). Morphology was studied via specular microscopy.

RESULTS

For this subject, the PRPH was 39.6 percent/hr and 40.5 percent/hr for right and left eyes respectively; these values are substantially reduced compared to the reported 55.3 percent/hr for an age-matched, non-contact lens wearing population. Specular microscopy demonstrated reduced cell counts of 1,052 cells/mm2 OD and 1,741 cells/mm2 OS compared to an age adjusted normal population with 2,853 +/- 320 cells/mm2.

CONCLUSIONS

This case example appears to represent an extreme case of contact lens abuse and the effects of long-term hypoxic contact lens wear on corneal function.

A case report of Mycobacterium chelonae keratitis and a review of mycobacterial infections of the eye and orbit

Mycobacteria are unusual causes of keratitis and other ocular infections but the outcome of infection is often serious. We report a case of keratitis due to Mycobacterium chelonae, a rapidly growing environmental mycobacterium, in a soft contact-lens wearer, and discuss the difficulty and delay in identifying the organism, twice erroneously identified as Nocardia asteroides on morphological grounds. Despite in vitro susceptibility, the response to anti-bacterial agents was negligible and a second keratoplasty was required after a recurrence of disease at the donor-host junction. We review the role of mycobacteria as the cause of keratitis and other forms of ocular disease.

Effects of rigid lens extended wear on lactate dehydrogenase activity and isozymes in rabbit tears

Effects of and recovery from continuous wear of four rigid gas permeable (RGP) contact lenses was assessed by noninvasive measurement of lactate dehydrogenase (LDH) activity and isozyme pattern in rabbit tears. Oxygen transmissibility (Dk/L) of lenses used was 27, 44, 84, and 97 x 10(-9) (cm/s)(ml O2/ml mm Hg); lens thickness (0.15 mm) and diameter (14.0 mm) were standardized. Lenses were worn continuously for 90 days; recovery was assessed 30 days after cessation of lens wear. LDH activity was measured by UV rate assay; isozyme subtypes were determined by agarose gel electrophoresis. Light and scanning electron microscopy (LM, SEM) were used with the determination of total protein as additional measures of lens effects. LDH levels were inversely correlated with lens Dk/L values; low Dk/L values increased the anaerobic (LDH4,5)/aerobic (LDH1,2,3) subtypen ratio indicating in vivo metabolic shift. SEM observations were consistent with these results. There was no significant difference in the total cell content of tears or total tear protein levels between control and RGP test-wear groups. Measurement of tear LDH activity and isozyme ratios appears to provide a sensitive, noninvasive assessment of the effects of RGP lens-induced hypoxia over time on the corneal surface. A level of Dk/L of > or = 84 appears best for maintaining corneal physiology during extended wear. Recovery from chronic lens-induced hypoxia is characterized by a return to normal tear LDH levels and isozyme subtypes.

A retrospective study of disposable extended wear lenses in 100 patients: year 3

We present the results of the third year of follow-up of a group of 100 patients wearing disposable contact lenses on an extended wear basis. Thirty-seven males and 63 females participated in the study. The mean patient age was 41.76 years (SD: 14.5), and the mean patient follow-up time was 37.73 months (SD: 5.25). Twenty-three patients were lost to follow-up. Most of those lost to follow-up decided to purchase their lenses at discount outlets. A case of recurrent corneal ulcers in a patient wearing lenses obtained from a discount outlet is described. A significant decrease in events defined as complications (14 events) was noted as compared with the second year (32 events) of the study. One corneal infiltrate and one corneal ulcer were noted. Disposable extended wear lenses may be a reasonable means of vision correction in the properly selected patient with appropriate follow-up provided by a well-trained eye care practitioner.

Rigid gas permeable extended wear

We have reviewed the pertinent literature on rigid gas permeable (RGP) extended wear contact lenses, and we discuss the benefits and adverse reactions of this contact lens modality, drawing conclusions from reviewed studies. We suggest parameters for success with these lenses and guidelines for the prevention of adverse reactions.

Testing hypotheses for risk factors for contact lens-associated infectious keratitis in an animal model

Various risk factors contributing to contact lens related infectious corneal ulcers were tested. These factors included the presence of infectious organisms, loss of corneal surface integrity, and corneal hypoxia. High concentrations of Pseudomonas bacteria were applied to rabbit corneas under the following conditions: normal, intact corneal surface; "mild" corneal hypoxia with extended-wear soft contact lens and eyes closed; "moderate" corneal hypoxia with daily wear soft contact lens and eyes closed; "severe" corneal hypoxia with daily wear aphakic soft contact lens and eyes closed; corneal abrasion and eyes open; corneal abrasion and eyes closed; corneal abrasion with soft contact lens and closed eyes. No infectious ulcers occurred in normal intact corneas. The frequency of infectious ulcers increased with increasing degrees of corneal swelling. No ulcers were found in corneas with a mean swelling of 10%, whereas a mean swelling of 20% resulted in ulcers in half the group, and a mean swelling of 43% resulted in ulcers in all eyes. The three groups of abraded corneas resulted in infectious ulcers at a 20 to 30% frequency. The presence of infectious organisms alone does not lead to infectious corneal ulcers in rabbits. Corneal abrasions are a risk factor for infectious ulcers, but moderate and severe degrees of hypoxia are more significant.

Comparison of clinical diagnostic tests in hydrogel extended wear

We compared the relative value of biomicroscopy, pachometry, esthesiometry, and corneal oxygen flux measurements for the detection of corneal hypoxia in myopic patients wearing hydrogel extended wear lenses. Measurements were standardized by relating the change in each parameter to its test-retest reliability. After 3 months of extended wear the greatest change occurred in biomicroscopic signs (microcysts and vacuoles, fluorescein staining, inferior conjunctival hyperemia) and in stromal edema measured with pachometry. These four signs were poorly correlated to each other (Pearson's r < 0.3), indicating that none could be considered redundant. Stromal striae, endothelial edema (blebs), esthesiometry, and corneal oxygen flux measurements showed relatively little change during the period of lens wear.

FluoroPerm 151 extended wear: a clinical study

In this 3-month study, 132 (81.5%) of 162 eyes (81 subjects) successfully wore FluoroPerm 151 RGP lenses on an extended wear schedule. Fifty-nine (72.8%) subjects were adapted RGP lens wearers; 3 (3.7%) were polymethylmethacrylate (PMMA) lens wearers; 12 (14.8%) were current hydrogel lens wearers; and 7 (8.6%) had no previous contact lens experience. Throughout the study, no significant physiologic or pathologic concerns were found or led to lens discontinuation. Among the 30 eyes that discontinued the study, there were no serious health concerns; the chief reason for discontinuing lens wear was discomfort. Study results seemed to indicate that little, if any, physiologic stress was induced by extended wear of the FluoroPerm 151 lenses. The overall clinical success with the FluroPerm 151 lenses can be attributed to the material's high level of oxygen flux and compatible surface characteristics.

Risk factors with contact lens related suppurative keratitis

Risk factors in contact lens related suppurative keratitis were investigated. Over 12 months, sixty contact lens wearers presented with presumed microbial keratitis and 147 presented with presumed sterile keratitis. The control group consisted of contact lens wearers without lens related disorders (n = 507). The relative risk of microbial keratitis for extended wear soft contact lens users were 36.8 times (12.6-107.6) that of rigid gas permeable (RGP) contact lens users; while the relative risk of sterile keratitis among extended wear soft lens users was 4.6 times (2.2-9.9) that of RGP lens users. For daily wear soft contact lens users, the relative risk of microbial keratitis was 4.2 times (1.1-16.0) that of RGP lens wearers; for sterile keratitis the relative risk was 2.3 times (1.3-4.3) greater than RGP contact lens users. A multivariable logistic regression analysis was used to examine associated risk factors for daily and extended wear soft lens users. The type of disinfection system and its frequency of use were associated with both microbial keratitis and sterile keratitis in daily wear users. Duration of overnight wear and gender were associated with microbial keratitis, while a patient's age and socioeconomic class were associated with sterile keratitis. Different relative risks and risk factors for microbial keratitis and sterile keratitis support the use of a clinical definition to differentiate the diseases.

Epithelial, stromal, and endothelial responses to hydrogel extended wear

Corneal epithelial, stromal, and endothelial edema were assessed in 19 subjects before and after a 4-month period of hydrogel contact lens extended wear. A thick hydrogel lens was worn under closed-eye conditions for 3 hours to induce stromal edema and endothelial edema (blebs), and eye bathing with a hypotonic solution was used to induce epithelial edema. Initial central stromal edema (corneal thickness) was 14.4 +/- 0.6% in response to the stress lens compared with 2.1 +/- 0.4% in the control eye (mean +/- SE). After 4 months of lens extended wear, stromal edema was significantly reduced (P < 0.0001) to 12.3 +/- 0.6% and 0.5 +/- 0.2% in test and control eyes, respectively. Adjustment of the stromal edema response at the second visit for residual edema from the extended wear accounted for some of the reduction, but the edema response remained significantly decreased (stress lens: 13.6 +/- 0.7%; and control eye: 1.2 +/- 0.4%). Endothelial edema response to the stress lens, as measured on a scale of 1 to 7, decreased from 4.6 +/- 0.3 to 2.8 +/- 0.3 over the period of extended wear. The final level was indistinguishable from that of the eye not wearing the stress lens. The epithelial edema response to hypotonic exposure was not altered with extended wear. These findings indicate that the stromal and endothelial edema responses may be unreliable diagnostic signs of the physiologic impact of hydrogel extended wear.

Contact lenses and corneal shields

Contact lens wear has been associated with a wide spectrum of corneal complications. Disposable contact lenses have not eliminated the problem of corneal ulcers associated with extended-wear contact lenses. Rigid, gas-permeable extended-wear lenses may be considered as an acceptable alternative to extended wear of soft contact lenses. Collagen corneal shields are a clinical indicator of collagenase activity on the ocular surface and serve as a collagenase inhibitor.

A comparison of conventional and disposable extended wear contact lenses

The charts of 126 extended wear contact lens patients (65 disposable and 61 conventional extended wear lens users) were reviewed for subjective and objective contact lens problems. We found that the number of complication events per person per year of lens wear was higher for conventional extended lens wearers than for disposable extended wear patients. There was a trend in both groups toward decreased numbers of complications in the second and third years of lens wear. Within each group, we also examined first time lens wearers and patients with a history of contact lens related complications. Both of these subgroups also fared better with disposable lenses, with fewer complication events per year and fewer complications overall. Of the 20 individual signs and symptoms that were analyzed, 13 occurred more frequently among conventional extended wear lens users; this difference was statistically significant for itching, burning and dryness, poor vision, foreign body sensation, torn and lost lenses, giant papillary conjunctivitis, mucus, and superficial punctate keratopathy. Five signs were more frequent among the disposable extended wear lens users, but the difference was not statistically significant. There were no cases of ulcerative keratitis in either group. The average wearing time was 11.2 +/- 5.9 days for conventional extended wear patients and 6.7 +/- 2.3 days in the disposable group. The difference in wearing time between the two groups may have been a factor in the higher complication rate among conventional extended wear lens patients.

Morphological and biochemical evaluation for rigid gas permeable contact lens extended wear on rabbit corneal epithelium

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 x 10(-9) (cm/sec) (mL O2/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/Ltotal 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 x 10(-9) Dk/Ltotal 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.

Complications and symptoms in disposable extended wear lenses compared with conventional soft daily wear and soft extended wear lenses

We conducted a historical cohort study of 2,433 cosmetic contact lens wearers (1,055 conventional [non-disposable] daily wear lens users, 905 disposable extended wear lens users, and 473 conventional extended wear lens users) in order to estimate the rates of occurrence of complications and symptoms among disposable extended wear contact lens users and compare these rates with those for conventional soft daily wear users and conventional soft extended wear users. Data were abstracted from the office records of eight eye care practitioners for the period February 1987 through April 1989. The prevalence of all complications for disposable extended wear lens users was not significantly different from the prevalence for conventional daily wear lens users but was significantly lower than the prevalence for conventional extended wear lens users. The incidence of ulcers among disposable extended wear lens users did not differ significantly from the incidence found with conventional extended wear, but was significantly higher than the rate for conventional daily wear. Disposable extended wear lenses, in contrast to conventional extended wear lenses, may be more strongly associated with benign peripheral infiltrates than with the more serious central ulcers. Disposable extended wear lens users reported symptoms less frequently at routine scheduled visits than both conventional daily wear and conventional extended wear users and had a lower rate of unscheduled visits for complications and symptoms.

Effect of Pseudomonas aeruginosa concentration in experimental contact lens-related microbial keratitis

Pseudomonas aeruginosa adherence in vitro to perfilcon A (ionic, 71% H2O) extended wear soft contact lenses--both new and after 7 days of continuous wear on closed rabbit eyes--was found to be related directly to the bacterial concentration in the contaminating solution. Thirty rabbits wore perfilcon A lenses for 7 days with complete lid closure to mimic contact lens overwear. After 7 days, conjunctival cultures showed no growth of pathogens, but all corneas had developed epithelial cell exfoliation and/or epithelial defects and stromal edema. The lenses were then incubated in various concentrations (10(7), 10(6), 10(5), 10(4), and 10(2) colony-forming units per milliliter or saline control; n = 5/group) of P. aeruginosa suspensions and replaced on their respective corneas with tarsorrhaphies for an additional 48 h. By day 9, corneal thickness had increased significantly, and P. aeruginosa keratitis had developed in 13 of 25 bacterially exposed eyes but not in 5 control eyes. Although with decreasing P. aeruginosa concentration the prevalence of ulcerative microbial keratitis also decreased, the initial concentration of bacteria or the initial extent of soft contact lens-induced corneal damage had no influence on the ultimate clinical severity of the disease.