Pseudomonas Keratitis Associated With Continuous Wear Silicone-Hydrogel Soft Contact Lens

PURPOSE

To report a case of Pseudomonas aeruginosa culture-positive microbial keratitis in a patient wearing continuous-wear silicone hydrogel soft contact lenses.

METHODS

A 23-year-old white woman in good health had been wearing silicone hydrogel (lotrafilcon A) soft contact lenses continuously for 26 days when she was examined for a corneal ulcer in her left eye. She had given a history of water jet skiing and diving while wearing her contact lenses. Scrapings of the corneal ulcer were positive for P. aeruginosa, and the patient was treated with fortified topical cefazolin and gentamicin for 1 week and subsequently with topical ciprofloxacin for 2 weeks.

RESULTS

The microbial keratitis resolved with successful treatment. However, the patient had a residual visual deficit secondary to stromal scarring.

CONCLUSIONS

The recently introduced continuous-wear silicone hydrogel soft contact lenses, with their hyper oxygen permeability (Dk), have been shown to overcome hypoxia-associated complications and to have less P. aeruginosa binding to the corneal epithelium. Our case shows that sight-threatening microbial keratitis can still occur even with silicone hydrogel soft contact lenses. Contact lens practitioners should educate patients on the risk of sight-threatening microbial keratitis, the need for patient compliance, and prompt assessment of contact lens-related complaints.

Effects of extended-wear soft contact lenses on the ocular surface and central corneal thickness

PURPOSE

New contact lens materials with high oxygen permeability are said to be convenient for the extended-wear (EW) schedule. We evaluated the short-term effect of EW soft contact lens usage on ocular surface and central corneal thickness.

PATIENTS AND METHODS

Fifty-two eyes of 26 patients were included in the study. Sixteen of the patients used the high oxygen-permeable lenses for a 30-day extended-wear schedule (group I). Ten patients used the lenses on a daily wear basis (DW, group II). All patients were evaluated for visual acuity and central corneal thickness by corneal and conjunctival biomicroscopy, Schirmer and tear break-up time (BUT) tests. Impression cytology was performed in the superior/temporal, inferior/nasal quadrants of the conjunctiva, 1 mm from the limbus, with cellulose acetate filter paper. The specimens were graded under light microscopy according to Nelson's classification.

RESULTS

Three patients in the EW group were excluded from the study as they discontinued lens usage due to slight discomfort and hyperemia. Biomicroscopic findings and tear function tests indicated no increased pathological results. Central corneal thickness decreased from 554 +/- 9.55 to 546 +/- 9.30 microm (mean +/- SEM) in the EW group (p = 0.002), whereas no significant change occurred in the DW group. Cytological evaluation of the EW group showed an 88% increase in metaplasia (p = 0.007), especially close to the limbal areas and in the superior quadrants; this ratio was 30% in the DW group. Snake-like chromatin changes were found to be increased, from 4 to 6 patients, in the EW group while it remained the same in the DW group (p > 0.05). Individual comparisons of the initial and final pathological conditions of the ocular surfaces in the two groups showed that there was an increase in pathology in the EW group while there was no significant difference in the DW group.

CONCLUSIONS

On a 30-day extended-wear basis with high oxygen-permeable lenses, the possible development and increase of conjunctival cytologic changes secondary to mechanical trauma is one of the main remaining problems. Conjunctival and related immunologic pathologies should not be overlooked when prescribing an extended-wear lens schedule.

Extended wear contact lenses

The experience with the complications associated with extended wear contact lenses has made practitioners and patients fearful of this modality. Today, strong scientific evidence suggest that the hypoxia problems associated with extended wear lenses have been solved. Good clinical evidence suggests that the new high-Dk silicone lenses are safe and can be worn successfully for up to 30 days. Patients can now be offered contact lenses that meet their desire of continuous vision; however, practitioners and patients must be instructed regarding the signs and symptoms of contact lens complications. Practitioners need to be educated in the diagnosis and management of the complications. Patients need to be educated about the need for proper eye care, contact lens care regimens, and appropriate follow-up visits.

Changes in corneal structure with continuous wear of high-Dk soft contact lenses: a pilot study

PURPOSE

Despite numerous studies that have considered the effects of extended wear of high-Dk soft contact lenses on ocular physiology, little attention has been paid to the impact of such lenses on central or peripheral corneal thickness and curvature. The present study aims to report the time course of changes in corneal thickness and curvature that accompanies the 30-night continuous wear of new silicone hydrogel soft contact lenses in a neophyte population in a longitudinal study.

METHODS

Six subjects wore high-Dk lotrafilcon (Dk = 140) on a 30-night replacement schedule for 12 months. Only measurements from the right eye were considered for analysis. Topographical measurements of corneal thickness and curvature were taken. The same parameters were monitored for an additional period of 3 months after lens removal.

RESULTS

An almost homogenous increase in corneal radius of curvature was detected for all the locations studied, being statistically significant for the 4-mm cord diameter area. This effect was associated with a progressive thinning effect for the central cornea, whereas midperipheral and peripheral areas did not display such a thinning effect during continuous wear. These effects were still evident for the central cornea 3 months after contact lens wear discontinuation.

CONCLUSIONS

Continuous wear of high-Dk silicone hydrogel contact lenses is associated with clinically appreciable changes in topographical corneal curvature, whereas only a reduction in corneal thickness is appreciated in the central area. This effect seems to be a result of mechanical pressure induced by these hybrid hyperpermeable materials, characterized by a higher modulus of elasticity. The small sample size compromises the conclusions addressed from this study, and further work will be necessary to confirm the present results.

Recovery time of corneal epithelial proliferation in the rabbit following rigid gas-permeable extended contact-lens wear

PURPOSE

To determine recovery time needed for the corneal epithelium to return to a normal proliferation rate following 24-hour rigid gas-permeable (RGP) lens wear.

METHODS

An RGP lens (Dk/t = 10) was fitted at 9:00 am on one randomly chosen eye of each rabbit (N = 16) and removed 24 hours later while the other eye served as a control. Following contact lens removal, the rabbits were injected at four different time intervals (1,2, 4, and 7 days) with 5-bromo-deoxyuridine (BrdU) at 9:00 am to label dividing corneal epithelial cells. All animals were sacrificed 24 hours after BrdU injection, and corneas were stained for BrdU. A series of continuously adjacent digital images of the whole-mount epithelium was collected from superior limbus to central cornea, and all BrdU-labeled epithelial cell pairs on each digitized image were counted.

RESULTS

On day 1 following lens removal, the number of BrdU-labeled corneal epithelium cells was reduced by 50% centrally (C) and 36% peripherally (P) (P < 0.001) compared with control eyes. At day 2, there was no statistically significant difference between control and experimental corneas (P = 0.675). At day 4, a marked significant increase in BrdU-labeled cells was noted, averaging 83% (C) and 96% (P) (P < 0.001). At day 7, BrdU-labeling returned to control values, although it was still slightly elevated (14% [C] and 5% [P], P = 0.045).

CONCLUSIONS

The corneal epithelium in the rabbit required at least 1 full week to recover to its stable baseline proliferation rate following only 24 hours of RGP lens wear. Interestingly, hyperproliferation was noted within the limbal, peripheral, and mid-peripheral corneal epithelium 4 days after lens removal.

Mucin balls with wear of conventional and silicone hydrogel contact lenses

PURPOSE

To compare the frequency of mucin balls in subjects wearing conventional and high-Dk silicone hydrogel lenses during 12 months of extended-wear and to determine whether mucin balls are associated with any lens or subject characteristics.

METHODS

This study used data from a clinical trial where subjects wore either conventional hydrogel (N = 69, 6-night extended-wear) or silicone hydrogel (N = 70, 30-night extended-wear) contact lenses for 12 months. The number of mucin balls and other physiological responses, lens fit and performance, and subjective patient responses to lens wear were rated at each scheduled visit.

RESULTS

Subjects in the silicone hydrogel group had significantly greater numbers of mucin balls compared with subjects in the conventional hydrogel group over time (p < 0.001), but there were no significant differences in the percentage of subjects with mucin balls between the two groups. Increasing lens wettability, back surface deposits, and time of lens wear were associated with higher numbers of mucin balls in the conventional hydrogel group (p < 0.05); steeper corneal curvature and increasing lens wettability, back surface deposits, and number of microcysts were associated with higher numbers of mucin balls in the silicone hydrogel group (p < 0.05).

CONCLUSIONS

This study indicates that a subset of the population is predisposed to develop mucin balls irrespective of the soft contact lens type worn, but lens type influences the degree of mucin ball formation. The relationship between lens wettability, back surface deposits, and steeper corneal curvature with mucin balls supports the hypothesis that the mechanical interaction of a lens with the surface layer of the epithelium and the tear film in association with the blinking forces of the lid is involved in mucin ball formation.

Morphology of corneal nerves in soft contact lens wear. A comparative study using confocal microscopy

The aim of this study was to evaluate corneal innervation in soft contact lens wearers using the Tomey Confoscan confocal microscope (40x/0.75 objective lens). Three distinct age- and sex-matched subject groups were involved, including extended soft (hydrogel and silicone-hydrogel) contact lens wearers, overnight soft (hydrogel) contact lens wearers, and non contact lens wearers. A number of variables were objectively measured, subjectively evaluated, or graded in order to investigate the distribution and morphology of corneal nerves. For most of the evaluated parameters, no statistically significant differences were found. However, qualitative observations showed noticeable differences in corneal nerve appearance among the different subject groups; the degree of corneal oedema was suggested as the main causative factor. In conclusion, neither the short-term (overnight wear) nor the long-term (12-month extended wear) soft contact lens wear appeared to affect the morphology and/or distribution of corneal nerves as viewed with confocal microscopy.

Menicon Z 30-day continuous wear lenses: a clinical comparison to Acuvue 7-day extended wear lenses

PURPOSE

To establish equivalent safety and efficacy of the clinical performance of a novel hyper-O2 transmissible rigid gas-permeable (RGP) lens (Menicon Z, tisilfocon A) when worn continuously for 30 days (29 nights) when compared with a conventional control hydrogel lens (Acuvue; etafilcon A) worn for 7 days (6 nights).

METHODS

This study was a prospective, open-label, 24-center, concurrent, cohort-controlled clinical trial. This abbreviated report will focus on the length of wear achieved, slitlamp findings, and adverse event rates.

RESULTS

Two-thirds (66.5%) of patients wearing the RGP lens achieved greater than or equal to 22 nights of continuous wear; slitlamp observations revealed two categories of findings: those associated with lens modality and those with lens wearing time. Adverse events were mostly associated with foreign body abrasions for RGP lenses, whereas the hydrogel lens showed a higher number of bacterial infections.

CONCLUSION

The results of this study revealed some interesting differences in the classification and severity of findings. The results demonstrate that the continuous wear of Menicon Z (tisilfocon A) RGP lenses for up to 30 nights is a safe and equivalent alternative to 7-day (6 nights) hydrogel wear lenses.

Microbial keratitis and vision loss with contact lenses

PURPOSE

Microbial keratitis is the only sight-threatening adverse event that occurs with contact lens wear. This article gives a preliminary estimation of the incidence of microbial keratitis and vision loss with continuous-wear contact lenses made from highly oxygen permeable (Dk) materials.

METHODS

The most up-to-date data available on microbial keratitis and vision loss are collected from a range of sources including industry, private practice, and publications and is reviewed.

RESULTS

There have been 16 cases of microbial keratitis with high-Dk silicone hydrogel lenses. Of the 13 where data are available, none have lost two or more lines of best-corrected visual acuity (BCVA).

CONCLUSION

First approximation indicates that the incidence of microbial keratitis with high-Dk silicone hydrogel lenses may be lower than the incidence with low-Dk soft lenses during extended wear. The rate of loss of more than two lines of BCVA is low in patients that develop microbial keratitis with low- and high-Dk soft lenses.

Risk factors for corneal infiltrative events with 30-night continuous wear of silicone hydrogel lenses

PURPOSE

This analysis reports on risk factors for corneal infiltrative events from a 1-year, randomized clinical trial of lotrafilcon A lenses.

METHODS

Six hundred fifty-eight subjects randomized to lotrafilcon A lenses were observed in a 1-year clinical trial in the United States. Risk factors gathered at baseline were analyzed to determine their association with corneal infiltrative events.

RESULTS

Factors examined but not found to be associated with events were male sex, history of extended or daily lens wear, refractive error, neovascularization, or assessment of lens fit. Significant factors included subject age 18 to 29 years, smoking, smoking and young age combined, history of corneal scar, contact lens acute red eye (CLARE), and corneal infiltrates.

CONCLUSION

Risk factors for corneal infiltrative events with silicone hydrogel lenses worn for 30 nights of continuous wear have been identified. Wearers with a history of inflammatory events such as contact lens peripheral ulcer or CLARE should consider 30-night continuous wear with these lenses. Careful counseling of wearers who smoke is advised.

A 1-year prospective clinical trial of menicon Z (tisilfocon A) rigid gas-permeable contact lenses worn on a 30-day continuous wear schedule

PURPOSE

To establish the safety and efficacy of clinical performance of a novel hyper-O2-transmitting rigid gas-permeable (RGP) lens (tisilfocon A) worn continuously for 30 days (29 nights) equivalent to a conventional control hydrogel lens (etafilcon A) worn for 7 days (6 nights).

METHODS

The study was a prospective, open-label, 24-center, concurrent cohort-controlled clinical trial.

OUTCOME MEASURES

Outcome measures included rates of adverse events, slitlamp findings, length of wear achieved, lens-corrected visual acuity, corneal refractive changes, dryness, and lens deposits.

RESULTS

The RGP lens wear test was equivalent or superior to the hydrogel control performance in all categories. Two-thirds (66.5%) of patients wearing the RGP lens achieved continuous wear periods greater than 22 nights; and 60.4% achieved more than 28 nights of continuous use. There was a statistically significant lower rate of adverse events, considered definitely related to lens wear, for the RGP test lens versus the hydrogel control (none vs. 2.2%; P = 0.007, Fisher's exact two-sided test).

CONCLUSIONS

Continuous wear of the tisilfocon A (Menicon Z, Menicon Co., Ltd., Nagoya, Japan) RGP lens for up to 30 nights is a safe and equivalent alternative to 7-day (6-night) hydrogel wear.

Corneal thickness results in the Menicon Z 30-day continuous wear and ACUVUE 7-day extended-wear contact lens clinical trial

PURPOSE

This study was conducted to measure the corneal thickness changes associated with wearing 30-day tisilfocon A (Dk = 163) and 6-day etafilcon A (Dk = 28) contact lenses. The probable cause of the outcomes is discussed.

METHODS

Thirty subjects were fitted with Menicon Z rigid gas-permeable (RGP) contact lenses and a control group (n = 30) was fitted with ACUVUE hydrogel lenses, at two study sites. After a 2-week period of daily wear, subjects began prolonged wear. Measurements were performed at the dispensing visit, and then at the 2-week daily wear, the 1-week, 6-month, and 12-month extended- and continuous-wear visits.

RESULTS

Repeated measures analysis of covariance was performed on mean corneal thickness. There was a significant increase in corneal thickness in the hydrogel lens extended-wear group compared to the RGP group (P = 0.03). The mean corneal thickness in the ACUVUE group was 2.58% higher at the 2-week daily wear visit, 2.38% higher at the 1-week extended-wear visit, 2.96% higher at the 6-month, and 2.97% higher at the 1-year visit compared to the RGP continuous-wear patients.

DISCUSSION

Patients wearing high-Dk RGP contact lenses for continuous wear may have thinner corneas (within the normal thickness range) probably because of minimal hypoxia-induced corneal stromal swelling; RGP-induced reversible corneal epithelial compression; deceased epithelial sloughing; or long-term contact lens-induced keratocyte apoptosis. Patients wearing hydrogel contact lenses for extended wear may have thicker corneas because of hypoxia-induced corneal stromal swelling. Additional evidence of corneal hypoxic stress is seen in the higher prevalence of striae and epithelial microcysts in the hydrogel group and greater variability of corneal thickness measurements in the soft contact lens group in our results.

Time to resolution of contact lens-induced corneal warpage prior to refractive surgery

PURPOSE

To evaluate the resolution of contact lens-induced corneal warpage before keratorefractive surgery.

METHODS

We prospectively studied the eyes of 165 consecutive contact lens-wearing patients evaluated for keratorefractive surgery. Significant contact lens-induced corneal warpage was detected by comeal topography in 20 eyes of 11 patients. Manifested refraction, keratometry, and cornea topography were subsequently recorded during weekly or biweekly reevaluations and were compared with previous measurements for stability. Effects of age, sex, type, and duration of contact-lens wear and the recovery time period to stabilization were analyzed.

RESULTS

Overall, a 12% incidence of significant contact lens-induced corneal warpage was found. In patients demonstrating lens-associated warpage, the mean duration of prior contact lens wear was 21.2 years (range 10 to 30 years); lens use included daily wear soft (n=2), extended-wear soft (n=6), toric (n=4), and rigid gas-permeable contact lenses (n=8). Up to 3.0 diopter (D) refractive and 2.5D keratometric shifts accompanied by significant topography pattern differences were observed. The average recovery time for stabilization of refraction, keratometry (change within +/- 0.5D), and topography pattern was 7.8+/-6.7 weeks (range 1 to 20 weeks). Recovery rates differed between the lens types: soft extended-wear 11.6+/-8.5 weeks, soft toric lens 5.5+/-4.9 weeks, soft daily wear 2.5+/-2.1 weeks, and rigid gas-permeable 8.8+/-6.8 weeks.

CONCLUSION

We observed a 12% incidence of significant contact lens-induced corneal warpage in patients undergoing evaluation for keratorefractive surgery. Warpage occurred with all types of contact lens wear but resolved at different rates. To optimize the quality and predictability of keratorefractive procedures, an appropriate waiting period is necessary for contact lens-induced corneal warpage to stabilize. We suggest that resolution of corneal warpage be documented by stable serial manifested refractions, keratometry, and corneal topographic patterns before scheduling patients for keratorefractive surgery.

Lipid, lipase and lipocalin differences between tolerant and intolerant contact lens wearers

PURPOSE

Tear volume is reduced in symptomatic contact lens wearers, evaporation of the ocular tear film may be a cause. In this study we have focussed on symptomatic or intolerant subjects and compared their tear film lipid-related features to those tolerant to soft contact lens wear.

METHOD

Fourteen tolerant and 10 intolerant to lens wear subjects were recruited for this study. Intolerance to lens wear was defined as experiencing dryness symptoms in the first 6 hours of lens wear and consequently not being regular lens wearers. Lipid layer appearance was graded on a 0-5 scale, meibomian gland obstruction was observed, and the McMonnies questionnaire completed. Tears were collected without reflex stimulation. Degraded lipid (tear aldehyde content), secretory phospholipase A2 enzyme (sPLA2) concentration and activity and lipocalin concentration were analysed using spectrophotometry to quantify colour reactions and enzyme linked immunosorbent assays. Statistical results were calculated using non-parametric tests (median +/- interquartile range) or chi-squared test.

RESULTS

Degradation of polyunsaturated fatty acids and related esters leads to the by-products, malondialdehyde and 4-hydroxy-2(E)-nonenal. Intolerant subjects were found to have significantly (p = 0.004) higher concentrations of these by-products in their tears (0.85 +/- 1.0 microM; n = 9) compared to tolerant subjects (0.15 +/- 0.15 microM; n = 10). Intolerant subjects (1.86 +/- 0.05 ng/microl; n = 9) had significantly more (p = 0.047) sPLA2 enzyme in their tears compared with tolerant subjects (1.80 +/- 0.08 ng/microl; n = 12) and significantly more enzyme activity (p = 0.012). Intolerant subjects had significantly higher amounts of lipocalin in their tears (2.40 +/- 1.5 microg/microl; n = 10, p < 0.001) compared to tolerant subjects (0.45 +/- 0.85 microg/microl; n = 13).

CONCLUSION

Changes to the components of the tear film, however small, can disturb the nature and dynamics of the tear film. Increased lipases, degraded lipids and lipocalins in the aqueous tear film potentiates intolerance to contact lens wear and was associated with increased McMonnies dry eye history scores and symptoms scores.

Spherical indentations of human and rabbit corneal epithelium following extended contact lens wear

PURPOSE

Mucin balls appear to cause spherical indentations in the corneal epithelium during silicone hydrogel extended contact lens wear. The purpose of this report is to describe and quantify these spherical indentations, as examined in the human cornea by in vivo confocal microscopy and by in vitro immunocytochemistry in the rabbit cornea.

METHODS

Confocal images of full-thickness corneal epithelium were taken from three human patients participating in a 1-year extended contact lens-wear trial. Diameter and depth of the indentations were determined and measured. Two rabbit corneas showing identical indentations were stained with propidium iodide (nuclear stain) and Ki-67 (proliferation marker) and were examined using a laser scanning confocal microscope.

RESULTS

The diameter of the spherical indentations is largest on the epithelial surface, ranging from 33.9 to 78.8 microm. Indentations form spherical sections whose depth variably extends into the corneal epithelium, reaching as far as the basal lamina. The rabbit model showed no epithelial nuclei within the indentation. Furthermore, stromal cells localized immediately beneath the indentations were positive for Ki-67 (proliferation).

DISCUSSION

Spherical indentations of the corneal epithelium induced by mucin balls appear to be gaps or holes that can extend deep into the corneal epithelium. Indentations may potentially open a pathway for infectious microorganisms to penetrate the cornea. Surprisingly, stromal cells immediately beneath the holes were stimulated to proliferate, and there seemed to be an increase in localized cell density.

Corneal iron ring associated with orthokeratology lens wear

A healthy 27-year-old female with a history of daily wear soft contact lenses requested orthokeratology (ortho-k) treatment and was fitted with a pair of reverse geometry lenses. Two weeks later, a faint brown pigmented arc, with fuzzy margins, extending from four to eight o'clock at the inferior midperipheral part of the corneal surface was observed in both corneas. The patient was asymptomatic and happy with the results of the ortho-k treatment, and topographical maps showed a sharp and slightly decentered bull's eye pattern that indicated a clinically acceptable ortho-k effect for both eyes. The rings extended to a near-complete ring in both eyes and became denser and more significant as lens wear continued. The rings were similar in appearance to Fleischer's rings seen in keratoconic eyes and coincided with the margin of the bull's eye observed in the topographical maps. The patient continued to be asymptomatic with unaided visual acuity of 20/20(+1) (OD) and 20/25(-1) (OS). Apart from the presence of the iron rings bilaterally, the corneal integrity and topography were stable and clinically unremarkable; the patient was allowed to continue wearing the lenses with regular aftercare scheduled on a 3-month basis. Possible etiologies of the formation of iron rings are discussed.

[Eye problems due to contact lenses; an advisory report from the Health Council of the Netherlands]

In a recent report, the Committee on Health Risks of Contact Lenses from the Health Council of the Netherlands evaluated the health risks of contact lens wear in the Netherlands. Contact lens-related eye disease appears to be common, with an incidence of approximately 80,000 persons per year, who suffer from self-limiting or mild conditions. Such conditions are multifactorial, caused for example by chronic hypoxia, tear-film dysfunction or inadequate fit of the lens. They can range from ocular irritation to giant papillary conjunctivitis, a common cause of permanent lens intolerance. A very serious complication of contact lens wear is infectious keratitis, caused by bacteria or fungi. This is most common in users of permanent-wear soft lenses (20 per 10,000 persons per year) and can lead to a severe loss of vision. Therefore, the Committee has recommended that permanent-wear lenses should not be used. Moreover, lens fitting and follow-up of contact lens wearers should be a prerequisite for optometrists and ophthalmologists. However, the Dutch government has not taken action with respect to this last recommendation.

Confocal microscopic observations of stromal keratocytes during extended contact lens wear

BACKGROUND

The aim of this study was to monitor changes in keratocyte density during extended contact lens wear and to explore the possible role of hypoxia and oedema in any changes observed.

METHODS

Twenty-three neophyte myopic subjects wore a high Dk/t lens (PureVision) in one eye and a low Dk/t lens (Acuvue 2) in the other eye on an extended wear basis for six months. Slit-scanning confocal microscopy and ultrasonic pachometry were performed on both eyes at baseline (before lens wear), after three and six months of lens wear, and one week after cessation of lens wear (the 'post-cessation' visit).

RESULTS

No differences were established between the two lenses or between the three study visits for anterior stromal keratocyte density (KD). Posterior stromal KD was similar for the two lenses throughout the study. However, there was an overall drop in posterior KD of 14 per cent in both eyes at the six-month visit, compared to the initial visit. Posterior KD at the six-month visit was no different from that at the post-cessation visit. Corneal thickness was similar for the two lenses at the initial and post-cessation visits, but was three per cent greater for the eye wearing the Acuvue 2 lens at the six-month visit.

CONCLUSION

Extended contact lens wear causes a loss of keratocytes; this loss cannot be attributed to contact lens-induced hypoxia and/or oedema, or to an artifact of confocal microscopy relating to presence of residual oedema. It is postulated that lens-induced keratocyte loss may be related to the physical presence of contact lenses creating some mechanical effect.

Nocardia asteroides sclerokeratitis in a contact lens wearer

PURPOSE

To report a case of sclerokeratitis caused by Nocardia asteroides in a soft contact lens wearer.

CASE REPORT

A 65-year-old male presented with a 2-month history of a corneal ulcer in the left eye. He wore two weekly disposable soft contact lenses on an extended basis. He revealed his history of gardening before the onset of symptoms. On examination, his best-corrected visual acuity was 20/30 in the right eye and 20/400 in the left eye. In the left eye, there was conjunctival injection. His cornea showed multiple patchy infiltrates, with a feathery border that was raised and involved up to the midstroma. There was a 3+ anterior chamber reaction. Corneal scrapings were performed for smears and cultures. Topical 2% amikacin sulfate every half hour along with oral clarithromycin therapy was initiated. On follow-up, the sclera lesions worsened.

RESULTS

Smears of corneal scrapings revealed gram-positive filamentous bacteria in Gram's stain. The cultures grew Nocardia asteroides. The patient was switched to trimethoprim-sulfamethoxazole (Bactrim DS, Roche Laboratories, Nutley, NJ) as the sclera was involved. The patient responded to treatment, and the infection resolved. When last seen, approximately 4 months after his initial presentation to us, his visual acuity was 20/40 in the affected eye. There was corneal scarring, and the adjacent sclera showed thinning.

CONCLUSIONS

Nocardia sclerokeratitis can be associated with contact lens wear. Nocardia should be considered in the differential diagnosis of a corneal ulcer with an indolent progressive course with feathery infiltrates. Topical amikacin and systemic trimethoprim-sulfamethoxazole are effective drugs in the treatment of nocardial corneal infection with scleral involvement.

Effect of softperm lens wear on corneal thickness and topography: a comparison between keratoconic and normal corneae

PURPOSE

Complications related to contact lens-induced anoxia in the keratoconic eye are well documented, but the underlying mechanisms are poorly understood. This study compared topographical changes in corneal thickness and anterior corneal radius following SoftPerm (Ciba Vision, Atlanta, GA) (rigid-and-soft combination) lens wear in a group of keratoconic and normal individuals.

METHODS

Video keratoscopic (VKS) (EyeSys, Houston, TX) and ultrasonographic pachometry measurements were taken at nine ocular locations, at central, mid-peripheral, and peripheral corneal areas of keratoconic and normal subjects. Subjects were subsequently fitted with SoftPerm lenses and further measurements of corneal topography and thickness were noted after 1 day, 2 weeks, and 1 month of daily wear.

RESULTS

Corneal thickness increased significantly in normal and keratoconic eyes following SoftPerm lens wear. Radius values obtained from the VKS measurements indicated that a significant and progressive degree of corneal flattening occurred for the keratoconic subjects at the 1-day, 2-week, and 1-month intervals, in contrast to the normal group, whose corneal radii remained unchanged.

CONCLUSIONS

Corneal swelling occurs in both normal and keratoconic corneas following SoftPerm lens wear. Differences in the apparent central edema response within the keratoconic group may relate to the ease with which these corneas may be molded by a rigid contact lens.