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Biomedical subjects

Brien A Holden

Publications and source records attributed to Brien A Holden.

At least 19 recordsLinked to original sources
PubMed2005

Corneal oxygen deficiency.

OBJECTIVES: To compare the ocular effects of low Dk hydrogel and high Dk silicone hydrogel contact lenses. METHODS: A review of recent literature was conducted to determine the effects of wearing low and high Dk soft lenses on corneal swelling, vascular response, refractive error and the corneal epithelium. RESULTS: High Dk silicone hydrogel contact lenses became available for research and clinical practice almost 10 and 5 years ago respectively. During that time many studies have been conducted and it has been demonstrated repeatedly how much improvement there has been to the physiological response of the eye particularly when wearing the lenses on an overnight basis. CONCLUSIONS: Although silicone hydrogels only constitute about 2% of current wearers, their positive effects on the eye compared with low Dk hydrogel lenses should make them the most dominant lenses in the near future.

Bacterial Infections↗
PubMed2005

The current state of corneal reshaping.

PURPOSE: The application of contact lenses to alter the shape of the cornea and temporarily reduce or eliminate myopia is known as orthokeratology, corneal refractive therapy, or corneal reshaping. It was first introduced in the 1960s, but high oxygen permeable materials and more sophisticated designs allow patients to wear contact lenses only during sleep, while dramatically improving the predictability and rate of myopia reduction. Many studies have shown that most corneal reshaping patients achieve uncorrected visual acuity of 20/25 or better that lasts all day long in one to two weeks of nighttime wear. Treatment is primarily effective through central epithelial thinning and midperipheral epithelial and stromal thickening. Much remains to be learned about corneal reshaping contact lenses and their effects on the cornea. METHODS: The authors reviewed existing knowledge and determined what needs to be learned in order to provide patients with appropriate informed consent prior to corneal reshaping contact lens wear. RESULTS: While corneal reshaping contact lenses are effective at temporarily reducing or eliminating myopia, claims about the progress of myopia being controlled with corneal reshaping contact lenses should not be made until further studies are published in peer-reviewed literature. The incidence and prevalence of microbial keratitis related to corneal reshaping contact lens wear is not known. Any overnight wear of contact lenses increases the risk of infection, but it is not known whether the risks of microbial keratitis are greater for corneal reshaping overnight contact lens wearers than other form of overnight contact lens wear. It is also not known whether the risk of microbial keratitis is greater for children than adults, but we must determine if children are at greater risk than adults because many children are wearing corneal reshaping contact lenses. CONCLUSIONS: Finally, it is recommended that ongoing education be provided to practitioners and staff regarding safety, informed consent, and prevention of potential problems, with special emphasis on the critical need to properly and thoroughly disinfect lenses that will be worn overnight.

Child↗
PubMed2005

Microbial keratitis in prospective studies of extended wear with disposable hydrogel contact lenses.

PURPOSE: To report the annualized incidence of microbial keratitis with extended wear of low oxygen transmissible (Dk/t) disposable soft contact lenses from prospective postmarket clinical trials. METHODS: Seven hundred ninety subjects were enrolled at the L.V. Prasad Eye Institute (LVPEI), Hyderabad, India from March 1993 to March 2000, resulting in 1231 patient eye years, and 167 subjects were enrolled at the Cornea and the Contact Lens Research Unit (CCLRU), Sydney, Australia from July 1987 to December 1999, resulting in 842 patient eye years. RESULTS: The annualized incidence of microbial keratitis per 10,000 eyes per year of lens wear was 32.5 (95% CI 8.9 to 83.2) for LVPEI, 23.8 (95% CI=2.9 to 85.8) for CCLRU; when data are combined across both centers, the incidence was 28.9 (95% CI=10.6 to 63) per 10,000 eyes per year of lens wear. This equates to 57.0 per 10,000 wearers or 1 in 173 wearers per year of lens wear. All events were rated as slight to moderate in severity and did not result in visual loss. Two events were described to highlight the challenges in diagnosis and treatment of microbial keratitis. CONCLUSIONS: The incidence of microbial keratitis with extended wear of low-Dk/t disposable lenses was higher in these prospective studies (1 in 210 wearers per year at CCLRU and 1 in 154 wearers per year at LVPEI) than that seen in retrospective population-based surveillance studies (1 in 500 wearers per year). Practitioners and patients should always be alert to signs and symptoms, and practitioners should adopt conservative strategies for diagnosis and management of contact lens-related adverse events.

Adolescent↗
PubMed2004

Comparison of the performance of 6- or 30-night extended wear schedules with silicone hydrogel lenses over 3 years.

AIM: To compare the clinical performance of silicone hydrogel lenses worn for 6- or 30-nights, with monthly replacement, for 3 years. METHODS: In this 3-year prospective clinical trial, 161 subjects were enrolled and 154 commenced extended wear. Clinical performance was assessed by comparing discontinuations and lens surface characteristics (front surface deposits, lens wettability, number of mucin balls), lens fitting performance (primary gaze movement, lens tightness), and physiologic parameters (limbal and bulbar redness, corneal and conjunctival staining, microcysts) and subjective parameters (ratings of comfort and vision) between groups. RESULTS: Eighty-eight subjects remained in the study after 36 months. There were no differences in the probability of subjects surviving in either group, and the major cause of lens-related discontinuation in both groups was contact lens-induced papillary conjunctivitis. There were no clinically important differences in performance between wear schedules. CONCLUSION: The long-term clinical performance of silicone hydrogels worn for 6- or 30-nights continuously was similar. Clinical markers of hypoxia were low in both groups, and the 6-night wear schedule was not superior to the 30-night wear schedule with regard to preventing lens spoilage, improving corneal physiology, or subjective symptoms of comfort and vision.

Adult↗
PubMed2004

Secretory phospholipase A2 deposition on contact lenses and its effect on bacterial adhesion.

PURPOSE: Secretory phospholipase A2 (sPLA2) is a potent antibacterial enzyme in tears and has been found to kill Staphylococcus aureus rapidly in vitro. The purpose was to determine whether sPLA2 deposition is associated with contact lens (CL) type, if sPLA2 remains active on CLs, and if this has an effect on bacterial adhesion. METHODS: Ionic (etafilcon A) and nonionic (Polymacon) high-water, soft CLs were used. CLs were worn for 6 hours (daily wear, n = 39) or 6 nights on an extended-wear schedule (n = 25). Tears were collected from patients and worn contact lenses were removed and protein and active enzymes extracted for estimation of their levels. The number of S. aureus adhering to sPLA2-soaked CLs in vitro was also quantified. RESULTS: There was no significant difference in the concentration of sPLA2 in tears between groups of daily CL wearers. Significantly less sPLA2 was recovered from Polymacon CLs for both daily and extended wear compared with etafilcon A CLs (daily wear: 3 vs. 5 ng/lens; extended wear: 3 vs. 6 ng/lens; P < 0.05). sPLA2 activity correlated with protein amounts from lenses. Relatively less active sPLA2 was recovered from Polymacon contact lenses. sPLA2 reduced adhesion of Staphylococcus to contact lenses in vitro. CONCLUSIONS: Etafilcon A CLs absorb more active sPLA2 than Polymacon CLs, which increases with length of CL wear. The sequestering of sPLA2 onto CLs did not affect amounts of the enzyme in tears. sPLA2 adsorbed to a CL can reduce the viable Staphylococcus adhering to the CL, which may protect the eye from colonization by this pathogen.

Absorption↗
PubMed2003

Comparison of adverse events with daily disposable hydrogels and spectacle wear: results from a 12-month prospective clinical trial.

OBJECTIVE: To evaluate the type and incidence of adverse events seen with daily disposable hydrogel contact lens wear compared with a control (spectacle) group over 12 months. DESIGN: Prospective, randomized, observer-masked, comparative clinical trial. PARTICIPANTS: Two hundred eighty-one myopes with no prior contact lens wear experience were enrolled from August to December 1996. Subjects were 16 to 35 years old and had refractive errors ranging from a -0.75-diopter (D) sphere to a -6.00-D sphere with a cylinder less than -1.00 D. INTERVENTION: Each subject was randomly assigned to wear either bilateral disposable hydrogels on a daily disposable wear schedule or spectacles. MAIN OUTCOME MEASURE: Type and incidence of adverse events from each group. Adverse events were categorized as serious, significant, and nonsignificant based on the potential to cause vision impairment, severity at event, and level of clinical concern. RESULTS: At baseline, 1.6% of eyes had asymptomatic infiltrates that were nonsignificant. During the study, asymptomatic infiltrates were seen in both contact lens and spectacle groups at 20.5 events versus 11.3 events per 100 eyes per year of wear. No significant events were seen with the spectacle group. With the contact lens group, the type and incidence of significant events per 100 eyes per year of lens wear were corneal peripheral ulcer, 2.5 events; infiltrative keratitis, 1.5 events; and papillary conjunctivitis, 1 event. The incidence of both significant and nonsignificant events was greater with the contact lens group (P<0.05). No serious events (i.e., microbial keratitis) were seen in either group. A greater number of subjects were lost to follow-up or permanently discontinued from the contact lens group relative to the spectacle group (33% vs. 17%, P = 0.002). Lens-related problems such as dryness, discomfort, and difficulty with insertion and removal accounted for 27% of discontinuations from the contact lens group. Poor compliance (40%) was the greatest reason for discontinuations from the spectacle group. CONCLUSIONS: No clinically serious events were seen with either group. Only a small percentage of contact lens-wearing eyes presented with significant events, which is promising for daily disposable lens wear. Far more contact lens subjects were lost to follow-up or discontinued. Small, asymptomatic, subepithelial corneal infiltrates of unknown significance were seen in both contact lens- and spectacle-wearing eyes.

Adolescent↗
PubMed2003

Clinical characterization of corneal infiltrative events observed with soft contact lens wear.

PURPOSE: Corneal infiltrates are commonly observed during adverse reactions associated with contact lens wear. Broad ranges of presentations are encountered, and there is no well-established classification system. The aim of this paper is to categorize corneal infiltrates associated with soft lens wear and present the typical clinical characteristics associated with each type of event. METHODS: All events of corneal infiltrates occurring in soft contact lens clinical trials over 10 years (9 years retrospective and 1 year prospective) and conducted at two contact lens research centers were reviewed by a panel of experts comprising ophthalmologists, optometrists, and other biologic scientists. Classification of each event was based on assessment of a range of signs and symptoms by the review panel. RESULTS: A classification scheme was devised to distinguish infiltrative events that were serious and symptomatic (microbial keratitis), clinically significant and symptomatic (contact lens-induced peripheral ulcer, contact lens-induced acute red eye, infiltrative keratitis), and clinically nonsignificant and asymptomatic (asymptomatic infiltrative keratitis and asymptomatic infiltrates). CONCLUSION: Corneal infiltrates can be classified into six distinct categories. This classification scheme, based on clinical characteristics, should aid diagnosis, management, and treatment of corneal infiltrates as well as assisting investigations into the etiology of each of these conditions.

Contact Lenses, Hydrophilic↗
PubMed2003

Altered conjunctival response after contact lens-related corneal inflammation.

PURPOSE: Corneal inflammation in overnight contact lens (CL) wear is not fully understood. We designed a masked study to examine the impact of overnight CL wear on clinical variables in subjects who had previously experienced corneal inflammatory disease. METHODS: Forty-four subjects were entered into the study: Nine subjects who had previously experienced CL-associated acute red eye (CLARE) and nine controls; 13 subjects who had previously experienced CL-induced peripheral ulceration (CLPU) and 13 controls, respectively. Controls were matched for age, gender, CL wear experience, and refractive error. Subjects wore bilateral disposable CLs (-3.00 DS). Corneal, conjunctival, and CL fitting variables were assessed prior to sleep, after a single night of CL wear, at 1, 2, and 4 hours after waking by clinicians who were masked to group membership. Retrospective analysis of prewear corneal and conjunctival variables for CLARE subjects and their respective controls was also performed. RESULTS: Contact lens-associated acute red eye subjects consistently showed higher limbal redness (p < 0.05), bulbar redness (p < 0.05), and conjunctival staining (p < 0.005) compared with controls. Lens fitting and corneal variables were not significantly different at any time point for CLARE subjects. Contact lens-induced peripheral ulceration subjects were not different from matched controls for any variable at any time point. Limbal redness varied significantly over time among controls, with highest values measured at eye opening (p < 0.05). Retrospective analysis of prewear variables showed no significant differences between CLARE and control subjects. CONCLUSIONS: Wearers who previously experienced CLARE had a greater conjunctival response to CL wear compared with wearers who had no previous inflammatory disease. Clinical observations, however, were not helpful in predicting wearers who were predisposed to CLARE.

Adult↗
PubMed2003

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.

Adult↗
PubMed2003

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.

Adult↗
PubMed2003

Refractive error and visual impairment in African children in South Africa.

PURPOSE: To assess the prevalence of refractive error and visual impairment in school-aged African children in South Africa. METHODS: Random selection of geographically defined clusters was used to identify a sample of children 5 to 15 years of age in the Durban area. From January to August 2002, children in 35 clusters were enumerated through a door-to-door survey and examined in temporary facilities. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. In nine clusters, children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance. RESULTS: A total of 5599 children living in 2712 households were enumerated, and 4890 (87.3%) were examined. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 1.4%, 1.2%, and 0.32%, respectively. Refractive error was the cause in 63.6% of the 191 eyes with reduced vision, amblyopia in 7.3%, retinal disorders in 9.9%, corneal opacity in 3.7%, other causes in 3.1%, and unexplained causes in the remaining 12.0%. Exterior and anterior segment abnormalities were observed in 528 (10.8%) children, mainly corneal and conjunctival. Myopia (at least -0.50 D) in one or both eyes was present in 2.9% of children when measured with retinoscopy and in 4.0% measured with autorefraction. Beginning with an upward trend at age 14, myopia prevalence with autorefraction reached 9.6% at age 15. Myopia was also associated with increased parental education. Hyperopia (+2.00 D or more) in at least one eye was present in 1.8% of children when measured with retinoscopy and in 2.6% measured with autorefraction, with no significant predictors of hyperopia risk. CONCLUSIONS: The prevalence of reduced vision is low in school-age African children, most of it because of uncorrected refractive error. The high prevalence of corneal and other anterior segment abnormalities is a reflection of the inadequacy of primary eye care services in this area.

Adolescent↗
PubMed2002

Case reports of three atypical infiltrative keratitis events with high DK soft contact lens wear.

PURPOSE: We report three atypical infiltrative keratitis events in patients that had successfully worn highly oxygen permeable (Dk) soft contact lenses on an extended wear (EW) schedule for at least 15 months. These cases highlight the role of patient/practitioner education, patient compliance, examination, and appropriate referrals that are required to reduce the risk of complications during lens wear. METHODS AND RESULTS: Each patient had been wearing high Dk soft lenses on an EW schedule with monthly replacement for at least 15 months and presented with severe pain, redness, and photophobia. The events were characterized by focal infiltrate(s) with an overlying epithelial defect in the superior periphery to mid-periphery of the cornea and extensive diffuse infiltration. CONCLUSIONS: The signs and symptoms of each case were more severe than is typically associated with contact lens-related infiltrative keratitis. Because of the slow progression of signs and relatively fast resolution, the cases were not found to be microbial keratitis. Although high Dk soft contact lenses overcome hypoxia-associated complications associated with extended wear, patients and practitioners must be vigilant as adverse events can still occur and in rare instances can be severe. Education and patient compliance are a crucial part of successful management of patients on EW schedules. Constant reinforcement is necessary to ensure patient compliance.

Adult↗
PubMed2002

Bacterial populations on high-Dk silicone hydrogel contact lenses: effect of length of wear in asymptomatic patients.

BACKGROUND: Ocular infection and inflammation during extended wear with hydrogel lenses are often associated with contamination of the lenses with bacteria. This study examines the colonisation of a high-Dk silicone hydrogel contact lens worn on a 30-night extended wear basis (continuous wear) during asymptomatic lens wear. METHODS: Worn lenses were collected aseptically and placed in sterile vials. Microbial growth on various media was enumerated and the number of colony-forming units per whole lens was calculated. The proportions of samples contaminated with the bacteria and the extent of contamination were compared after one month, six months and two years of continuous wear with monthly replacement. The proportion of lenses that were sterile was calculated. RESULTS: The most frequently isolated and most numerous microbes that colonised the contact lenses during wear were the coagulase-negative staphylococci (in particular Staphylococcus epidermidis), followed by Propionibacterium sp. The frequency of isolation of the majority of bacterial isolates did not increase over time. Generally, lenses were sparsely colonised during asymptomatic wear. CONCLUSION: Up to two years continuous wear of silicone hydrogel lenses of the type used in this study does not appear to alter the types and number of bacteria that colonise the eye during wear, when lenses are replaced on a monthly schedule and the patients remain asymptomatic.

Adult↗