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Biomedical subjects

B A Holden

Publications and source records attributed to B A Holden.

At least 19 recordsLinked to original sources
PubMed2001

Superior epithelial arcuate lesions with soft contact lens wear.

BACKGROUND: Superior epithelial arcuate lesions (SEALs) are an infrequent and often asymptomatic complication of conventional soft contact lens wear. The characteristic arcuate pattern of the full-thickness corneal epithelial lesion usually occurs in the area covered by the upper eyelid, within 2 to 3 mm of the superior limbus in the 10- and 2-o'clock region. METHODS: Literature on SEALs and recent clinical records from clinical trials using two types of prototype high Dk soft contact lenses were reviewed to gain greater insights into the etiology of SEALs. RESULTS AND CONCLUSIONS: The reported low incidence of SEALs is partly because SEALs are not usually symptomatic. The etiology of SEALs is multifactorial. Our current hypothesis is that SEALs are produced by mechanical chaffing at the peripheral cornea. This chaffing occurs as a result of inward pressure of the upper lid, in an area where the peripheral corneal topography and lens design, rigidity, and surface characteristics combine to create excessive "frictional" pressure and abrasive shear force on the epithelial surface. Patient characteristics such as gender, age, and specific corneal and lid topographies also appear to influence the occurrence of SEALs. Prototype silicone hydrogel lenses are made from higher modulus materials with surfaces that seem to differ subtly in wettability in some patients. The prevalence of SEALs may well increase with the first generations of these lenses.

Clinical Trials as Topic↗
PubMed2001

Hypoxic effects on the anterior eye of high-Dk soft contact lens wearers are negligible.

PURPOSE: To determine whether the eyes of high-Dk soft contact lens wearing subjects can be discriminated from non-contact lens wearing subjects. METHODS: This study was a prospective masked assessment of 32 subjects, 16 of whom wore experimental high-Dk soft contact lenses and 16 of whom did not wear contact lenses. Subjects wore high-Dk lenses on a 30-night replacement schedule for an average of 9 months. Tear film characteristics, staining and vascularization of the cornea, conjunctival staining, and the presence of microcysts in the corneal epithelium were assessed using slitlamp microscopy. The endothelium was examined for polymegethism. RESULTS: No differences were found between the two groups in any of the variables that were examined (p > 0.05) except that the high-Dk lens wearing group had about twofold more tear film debris and 2.5-fold more severe conjunctival staining (p < 0.05). CONCLUSIONS: Hypoxia-associated effects were not apparent in the eyes of subjects wearing experimental high-Dk soft contact lenses. Conjunctival staining can generally distinguish lens wearers from non-lens wearers and can be used to discriminate between high-Dk lens wearing subjects and non-lens wearing subjects.

Adult↗
PubMed2001

Microbial colonization of soft contact lenses over time.

PURPOSE: To compare the bacterial colonization of soft contact lenses in subjects for successively increasing periods, up to 13 nights of wear. The aim of this study was to determine whether increasing the length of lens wear predisposed subjects to high levels of microbial colonization of lenses. METHODS: Subjects (N = 20) were divided into those with a prior history of adverse events (N = 6), gram-negative bacterial carriers (N = 6), and those with no previous history (N = 8). RESULTS: There were no temporal changes in microbial colonization of lenses. Lenses from all wearers were colonized at least once during the study by gram-positive bacteria at low numbers (<10 cfu/ml). Gram-negative bacteria colonized lenses at least once in 80% of all wearers. Lenses from gram-negative bacterial carriers were more frequently colonized by Staphylococcus aureus and Pseudomonas sp. compared with subjects with no previous history and subjects with a prior history of adverse events, respectively. Lenses from gram-negative bacterial carriers were less frequently colonized by a range of gram-positive bacteria compared with subjects with a prior history of adverse events. CONCLUSIONS: Increasing the length of lens wear up to 13 nights did not result in a predictable increase in bacterial colonization of contact lenses. Gram-positive bacteria were isolated frequently but in low numbers, whereas gram-negative bacteria were present sporadically.

Adult↗
PubMed2001

Bacterial populations on 30-night extended wear silicone hydrogel lenses.

PURPOSE: Ocular infection and inflammation during hydrogel lens extended wear is often associated with colonization of the lenses with bacteria. This study compares colonization of a high Dk silicone hydrogel contact lens (lotrafilcon A) worn on a 30-night extended wear basis to a low Dk HEMA-based lens (etafilcon A) worn on a 6-night extended wear schedule. METHODS: The group wearing the low Dk/t soft contact lens (n = 63) replaced their lenses weekly and the group wearing high Dk/t soft contact lenses replaced their lenses monthly (n = 64). Lens allocation was assigned randomly at enrollment. Worn lenses, from one eye only, were collected aseptically and placed in sterile vials. Microbial growth on various media was enumerated and the number of colony forming units (cfu) per lens was calculated in categories of normal ocular microbiota (such as coagulase-negative staphylococci and Propionibacterium spp.) and known ocular pathogens (such as Staphylococcus aureus and gram-negative bacteria). The proportion of samples colonized with these bacteria and the extent of colonization were compared between the two groups. The proportion of sterile lenses was calculated, and the types of bacteria on each lens group were compared. RESULTS: No differences between the low and high Dk/t Soft contact lens groups were observed in the proportion of lenses colonized by Propionibacterium spp. (48% vs 43%, P = 0.4) or coagulase-negative staphylococci (47% vs 54%, P = 0.2). Similarly, no differences were found for lenses colonized by S. aureus (0% vs 2%, P = 0.1) or gram-negative bacteria (3% vs 2%, P = 0.8). The types of bacteria isolated from the high and low Dk/t lenses were similar. There were no differences in the number of sterile samples (28% vs 27%, P = 0.8) from each group. CONCLUSIONS: These findings suggest that high Dk/t silicone hydrogel materials are colonized by similar numbers and types of microorganisms during extended wear compared to HEMA-based material. Most lenses were colonized by commensal bacteria during 30-night extended wear with high Dk/t lenses and during 6-night extended wear with low Dk/t lenses. The incidence of sterile samples was the same between the high and low Dk/t soft contact lens groups.

Adult↗
PubMed2000

ATPase-positive dendritic cells in the limbal and corneal epithelium of guinea pigs after extended wear of hydrogel lenses.

PURPOSE: It has been said that Langerhans cells can be induced to migrate into the central cornea by various stimuli. We investigated whether extended wear of hydrogel lenses induced the migration of Langerhans cells into the central cornea. METHODS: Guinea-pig eyes were fitted with hydrogel contact lenses, and the number of adenosine triphosphatase (ATPase)-positive dendritic cells at the limbus, peripheral, and central corneal epithelium was quantified after 1, 2, 4, and 8 nights of extended wear. The cells were identified with histochemical procedures using ATPase stain. RESULTS: At baseline, ATPase-positive dendritic cells were seen at the limbus and peripheral cornea, with the density decreasing from limbus to peripheral cornea. There were no cells in the central cornea. With extended wear, cells increased in number at the peripheral cornea from 2 nights onward, and cells were seen in the central cornea from 4 nights onward. CONCLUSION: Extended wear of hydrogel lenses induced migration of ATPase-positive dendritic cells (Langerhans cells) into the central cornea. It is possible that they may play a role in the pathophysiology of some of the adverse events seen with contact lens wear.

Adenosine Triphosphatases↗
PubMed2000

Microcyst response to high Dk/t silicone hydrogel contact lenses.

PURPOSE: To investigate the microcyst response to extended wear (EW) with high oxygen transmissible (Dk/t) silicone hydrogel lenses. METHODS: Microcysts were monitored for 12 months in subjects wearing low Dk/t hydrogel lenses on a 6-night EW schedule or high Dk/t hydrogel lenses on a 30-night EW schedule. Subjects wearing low Dk/t lenses transferred to the high Dk/t EW lenses and schedule after 12 months and were monitored for a further 6 months. RESULTS: The mean number of microcysts did not deviate from baseline in the high Dk/t group. Microcysts in the low Dk/t group increased over 12 months, and more microcysts were observed in low Dk/t lens wearers compared with high Dk/t lens wearers after 3 months. Microcysts increased in 50% of subjects 1 week after transfer to high Dk/t lenses and returned to baseline levels seen with high Dk/t lens wear within 3 months. CONCLUSIONS: EW with high Dk/t silicone hydrogel lenses did not cause an increase in microcyst numbers. It is not necessary to discontinue lens wear with patients who transfer from low to high Dk/t lenses because the increase in microcysts is transitory. This result has implications for practitioners when fitting and assessing the success of high Dk/t hydrogel lenses.

Adult↗
PubMed2000

Bacterial colonization of disposable soft contact lenses is greater during corneal infiltrative events than during asymptomatic extended lens wear.

Microorganisms, especially gram-negative bacteria, are considered to play a role in the etiology of certain corneal infiltrative events (CIEs) observed during soft contact lens wear. This study explored the possibility of microbial colonization of soft contact lenses as a risk factor leading to CIEs. In a clinical trial conducted from March 1993 to January 1996, 330 subjects wore disposable soft contact lenses on a 6-night extended-wear and disposal schedule. During this period, 4,321 lenses (118 during CIEs; 4,203 during asymptomatic lens wear) were recovered aseptically and analyzed for microbial colonization. A greater percentage of lenses were free from microbial colonization during asymptomatic wear than during CIEs (42 versus 23%; P < 0.0001). The incidence of gram-positive bacteria, gram-negative bacteria and fungi was greater during CIEs than during asymptomatic lens wear (P < 0.05). During asymptomatic lens wear, gram-positive bacteria were isolated most frequently and were usually normal external ocular microbiota. Of the gram-positive bacteria, the incidence of Streptococcus pneumoniae was greater during CIE than during asymptomatic wear (7.6 versus 0.6%; P < 0. 0001). While gram-negative bacteria were seen in few cases during asymptomatic wear, their incidence during CIE in comparison to asymptomatic wear was substantial and significant (23.7 versus 3.8%; P < 0.0001). Also, the level of colonization was high. Of CIEs, events of microbial keratitis, contact lens acute red eye, and asymptomatic infiltrative keratitis were associated with lens colonization with gram-negative bacteria or S. pneumoniae. Colonization of soft contact lenses with pathogenic bacteria, especially gram-negative bacteria and S. pneumoniae, appears to be a significant risk factor leading to CIE.

Bacteria↗
PubMed1999

Adverse events with extended wear of disposable hydrogels: results for the first 13 months of lens wear.

OBJECTIVE: To determine the type and incidence of adverse events seen in the first 13 months of extended wear from a prospective clinical trial involving the use of disposable hydrogels on a 6-night extended wear and replacement schedule. DESIGN: A prospective, noncomparative clinical trial. PARTICIPANTS: Three hundred thirty subjects were enrolled in the study from March 1993 to August 1996 and commenced in extended wear. The subjects were new contact lens users with ages ranging from 16 to 39 years and refractive errors from -1.00 to -6.50-diopter (D) sphere with cylindrical component less than 1.0 D. INTERVENTION: Disposable hydrogel lenses on a 6-night extended wear and replacement schedule. MAIN OUTCOME MEASURES: To determine the incidence of adverse events in the first 13 months of lens wear with the use of disposable hydrogels on an extended wear schedule. In addition, corneal infiltrative events observed with lens wear were classified based on their presenting signs and symptoms. RESULTS: A total of 137 adverse events were seen in 102 subjects in the first 13 months of extended wear. The type of adverse events and the incidence per 100 patients per year of lens wear were as follows: corneal infiltrative events (44.4 events), contact lens papillary conjunctivitis (6.4 events), neovascularization and corneal wrinkling (1.7 events each), corneal striae and superior epithelial arcuate lesions (1.3 events each), and blepharokeratoconjunctivitis (0.4 event). Viral keratoconjunctivitis was also observed (0.8 event). The corneal infiltrative events were further subclassified as follows: contact lens-induced peripheral ulcers (13.6 events), contact lens-induced acute red eyes (12.3 events), infiltrative keratitis (9.7 events), and asymptomatic infiltrative events (8.9 events). There were no events of infectious keratitis. Except for all events of contact lens-induced peripheral ulcers and two isolated events of infiltrative keratitis that resulted in scarring, all of the corneal infiltrative events resolved without sequelae. None of the events caused any loss of best-corrected visual acuity. CONCLUSIONS: Based on the observations from the first 13 months of extended wear in the trial, the majority of the complications associated with extended wear of disposable hydrogels are corneal infiltrative events. No events of microbial keratitis were seen in the first 13 months of extended wear. None of the events were associated with loss in best-corrected visual acuity. Clearly, frequent and regular disposing of lenses does not eliminate adverse effects, and better materials and designs are required for extended wear to be a successful method.

Adolescent↗
PubMed1999

Colonization of hydrogel lenses with Streptococcus pneumoniae: risk of development of corneal infiltrates.

PURPOSE: To report the association between colonization of contact lenses with Streptococcus pneumoniae and the observation of corneal infiltrative events in a group of patients wearing disposable hydrogel lenses on an extended-wear schedule. METHODS: In a prospective clinical trial, 330 patients wore disposable hydrogels on a 6-night extended-wear and replacement schedule. The contact lens, lid, and conjunctival microbiota of these subjects was analyzed at frequent intervals and at the time of an adverse event. RESULTS: Streptococcus pneumoniae was an uncommon isolate and was recovered from only one of the 3,763 conjunctival samples, five (0.1%) of the 3,764 lid samples, and 33 (0.8%) of the 4,315 contact lens samples. Of the 33 lens samples, 10 (30%) were associated with corneal infiltrative events. Many of the events were mild inflammatory responses and resolved rapidly on discontinuation of lens wear. The presence of S. pneumoniae on the contact lens was associated with a significant risk of development of corneal infiltrates (odds ratio, 3.0; p = 0.0227, logistic-regression analysis). CONCLUSIONS: Presence of S. pneumoniae on hydrogel lenses is a significant risk factor for the development of corneal infiltrates.

Adolescent↗
PubMed1999

The frequency of ocular symptoms during spectacle and daily soft and rigid contact lens wear.

PURPOSE: Ocular discomfort is the primary reason for discontinuation of contact lens wear. The purpose of the study was to quantify and compare the frequency of ocular symptoms experienced by spectacle wearers and wearers of soft and rigid daily contact lenses. METHODS: We analyzed the results of an ocular symptom survey of prospective volunteers for contact lens clinical trials during the period 1989 to 1995. Questions pertaining to lens-wear experience and ocular symptoms were answered by 883 untrained individuals without active ocular disease. The sample included 664 spectacle wearers, 171 soft contact lens (SCL) wearers, and 48 rigid gas-permeable (RGP) lens wearers. The frequencies of 10 ocular symptoms were compared for each group. Spearman's Rank Correlation was used to test for correlations between symptoms. The chi2 test was used to determine differences between subject groups, adjusted for multiple comparisons. RESULTS: There were no significant differences in the frequency of ocular symptoms between the soft contact lens (SCL) and RGP wearers. The most common symptom was ocular tiredness (27%). None of the symptoms were highly correlated, indicating that they are somewhat different "sensations." Despite ocular discomfort being the primary reason for discontinuation of lens wear, contact lens wearers experienced the same type and severity of symptoms as spectacle wearers. Thus (in order of frequency of occurrence), tiredness, itchiness, watering, pain, aching, excessive blinking, and burning had similar rates of occurrence for all three groups. The two major distinguishing symptoms were dryness and redness, which were reported far more frequently and with greater severity in both contact lens groups (p < 0.001). Grittiness was also reported more with RGP wearers than with spectacle wearers (p < 0.001). CONCLUSIONS: Contact lenses disturb the ocular environment, as evidenced by responses of increased ocular dryness, redness, and grittiness. Despite fundamental differences in SCL's and RGP contact lenses, both groups of contact lens wearers surveyed experienced a similar type and frequency of ocular symptoms.

Adult↗
PubMed1999

Incidence of contamination of preserved saline solutions during normal use.

PURPOSE: To ascertain the incidence of microbial contamination of preserved contact lens saline solutions with normal patient use. METHODS: Eight different brands of preserved saline were dispensed to 40 patients attending optometric practices in the Sydney area. After specific periods of time (7 to 28 days), the samples were collected and the solution bottle nozzles and contents underwent microbial analysis. RESULTS: The overall contamination rate was approximately 26% for contents only and 55% for nozzles of preserved saline solutions. This rate remained constant for all periods of use. Coagulase-negative Staphylococci were most frequently isolated. No Acanthamoebae were isolated. Saline preserved with ethylene-diamine-tetraacetic acid (EDTA) in conjunction with sorbic acid showed the highest percentage of sterility. CONCLUSIONS: The results of this study show that preserved saline became contaminated with gram-positive bacteria. This is in contrast to our previously published paper using unpreserved saline, where contamination was predominantly with gram-negative bacteria. The overall contamination rates with preserved saline were lower than for unpreserved saline.

Contact Lens Solutions↗
PubMed1999

Contact lens-induced peripheral ulcers with extended wear of disposable hydrogel lenses: histopathologic observations on the nature and type of corneal infiltrate.

PURPOSE: Contact lens-induced peripheral ulcer (CLPU), a sudden-onset adverse event observed with extended wear of hydrogel lenses, is characterized by a single, small, circular, focal anterior stromal infiltrate in the corneal periphery or midperiphery. The condition is always associated with a significant overlying epithelial loss and resolves in a scar. The aim was to determine, by using histopathologic techniques, the nature and type of the corneal infiltrate of these events. METHODS: Three CLPUs observed in three patients using disposable hydrogel lenses on an extended-wear schedule were examined. The eye was topically anesthetized, and a corneal section including all of the infiltrate was taken. A small triangular piece of conjunctiva immediately adjacent to the infiltrate was sectioned. The tissue was immediately fixed, processed, stained using hematoxylin and eosin and periodic acid-Schiff stains, and examined by using light microscopy. RESULTS: The diameter of these three corneal infiltrates varied from 0.3 to 0.6 mm. Histopathology of the corneal sections revealed a focal epithelial loss corresponding to the infiltrated stroma in all three patients. The adjacent epithelium was thinned. Bowman's layer was intact in two patients and had a localized area of loss in the remaining patient. The anterior stroma was densely infiltrated with polymorphonuclear leukocytes and had focal areas of necrosis. The infiltration was most dense in the region immediately underlying Bowman's layer. No other infiltrative cell type was seen in any of the sections. Histopathology of the conjunctiva revealed features consistent with normal conjunctival tissue. CONCLUSIONS: On histopathology of CLPU, distinctive features (i.e., focal corneal epithelial loss, an intact Bowman's membrane, and a localized infiltration of the anterior stroma with polymorphonuclear leukocytes) were seen. These features suggest that the event is an acute inflammatory process and probably noninfective in nature.

Adolescent↗
PubMed1998

Assessment of high and low contrast visual acuity after photorefractive keratectomy for myopia.

BACKGROUND: Our aim was to assess visual acuity using standardized charts and illumination conditions after photorefractive keratectomy. METHODS: High and low contrast visual acuity were measured on Bailey-Lovie logarithm of the minimum angle of resolution (LogMAR) charts under high and low illumination conditions on 105 photorefractive keratectomy patients who had been treated with the Summit (N = 60) or the VISX (N = 45) excimer laser. RESULTS: Best corrected visual acuity was reduced in the treated eye compared with the untreated control eye under all test conditions, with the greatest differences under conditions of low contrast and low illumination. Reduction of acuity under low contrast and low illumination was related to small optic zone sizes and steep ablation edge profiles found in Summit-treated eyes. In the VISX-treated eyes, high contrast acuity was reduced in the presence of central topographical irregularities, subepithelial haze, and higher myopic corrections. CONCLUSIONS: Testing conditions such as those described here may be useful in quantifying vision degradation in suboptimal viewing conditions and among patients with vague complaints.

Adult↗
PubMed1998

Nutritional requirements of the corneal epithelium and anterior stroma: clinical findings.

PURPOSE: To monitor the health of the epithelium and the anterior stroma when porous membranes are implanted into the feline cornea and to determine membrane diffusivity characteristics needed to maintain corneal integrity. METHODS: Filtration membranes in a range of effective pore sizes of less than 15 nm (groups 1 and 2, n = 11), 25 nm (group 3, n = 8), 50 nm (group 4, n = 16), and 100 nm (group 5, n = 15) were implanted into an interlamellar corneal pocket of the stroma. The implanted membranes ranged in thickness from 6 nm to 15 nm and were between 8 mm and 12 mm in diameter. Animals were monitored for clinical signs of intolerance to the implants. RESULTS: At 1 month, thinning and ulceration had occurred in the epithelium and the anterior stroma of all animals in groups 1 and 2; epithelial changes, anterior stromal thinning, and ulceration had developed in 75% of animals of group 3; 50% of animals showed vascularization and only 7% showed epithelial degeneration in group 4; and local anterior stromal thinning was observed in 7% of animals in group 5, indicating clinical acceptance of the implanted membrane. In the long term (greater than 50 days), 30% and 73% of the group 4 and 5 corneas, respectively, were clinically quiet. Analysis of the failure times indicated an inverse relation between failure rate and pore size: less than 15 nm > 25 nm > 50 nm > 100 nm. The difference between the 100-nm and 50-nm membranes was significant (P = 0.03). CONCLUSIONS: A corneal implant must have a porosity greater than that provided by 50-nm membranes. The 100-nm membranes used in this study establish the porosity needed to satisfy the nutritional requirements of the cornea.

Animals↗
PubMed1998

Contact lens induced peripheral ulcers during hydrogel contact lens wear.

PURPOSE: Ulcerative keratitis is the most serious adverse response associated with contact lens wear. However, some reports of microbial keratitis in the literature may refer to a less severe form of corneal ulceration, which we have termed contact lens induced peripheral ulcers (CLPU). METHODS: We present details of 11 cases of CLPU which occurred in clinical trials at our research unit. RESULTS: CLPU episodes are characterized by a single, small (< 2 mm diameter) circular lesion in the corneal mid-periphery or periphery, involving a focal loss of the full thickness of the epithelium associated with subepithelial stromal infiltrates. Patient symptoms may include ocular irritation, pain, photophobia, and lacrimation. They are usually associated with the use of hydrogel extended wear contact lenses. The lesions are self-limiting, typically healing within 7 days without treatment. After resolution, a small circular scar remains, which does not affect vision because of its peripheral location. The etiology of CLPU is unclear. In our studies, the incidence of CLPU was similar in conventional (2.9% per patient year) and disposable (2.0% per patient year) hydrogel extended wear, but lower during intermittent extended wear (1.6% per patient year); only one case occurred during daily wear (< 0.5% per patient year). CONCLUSIONS: A conservative approach to patient management of all suspected cases of corneal ulceration is encouraged. However, we suggest that future reports of ulcerative keratitis associated with various lens types and wearing schedules should differentiate between potentially devastating microbial keratitis and the relatively innocuous peripheral ulceration described in this paper.

Adult↗
PubMed1998

Overnight corneal swelling in symptomatic and asymptomatic contact lens wearers.

PURPOSE: High corneal swelling with contact lens wear may be a predictor of patient failure in overnight contact lens use. This study evaluated whether contact lens wearers who had previously experienced corneal inflammation showed greater corneal swelling following a single occasion of overnight contact lens use compared with matched controls. METHODS: Forty-four subjects were evaluated: 9 wearers who had experienced contact lens associated acute red eye (CLARE); 9 controls; 13 subjects who had experienced contact lens induced peripheral ulcer (CLPU); and 13 controls. Controls were matched to cases for age, gender, wear experience and refractive error. Subjects wore bilateral disposable contact lenses overnight. Central corneal thickness was measured optically using a Holden-Payor pachometer at baseline, on eye opening, and 1, 2, and 4 hours later. RESULTS: There was no significant difference in overnight corneal swelling between CLARE subjects (7.6 +/- 2.3%) and controls (7.0 +/- 2.3%) (P = 0.57). Similarly, there was no significant difference in overnight corneal swelling between CLPU subjects (7.7 +/- 2.2%) and controls (7.8 +/- 2.6%) (P = 0.89). Deswell rate was similar in all groups. CONCLUSIONS: There was no apparent predisposition for higher overnight corneal swelling or altered deswell rate after one night of lens wear in subjects who had previously experienced contact lens related corneal inflammation.

Adult↗