Corneal staining as a response to contact lens wear

Objective: To review the effects of contact lenses on the corneal surface.

Methods: A review of the literature and in-house research of corneal staining and its various forms of presentation.

Results: Corneal staining manifests in many different forms. The severity of staining or insult of the cornea is usually determined by the extent (area of coverage), density, and depth. The cause of staining is multifactorial, and its location is often linked to the type of lens that is being worn, the solution used to clean/disinfect the lens, the state of hydration of the soft lens, and the state of the cornea that has been affected by the lens.

Conclusions: Sodium fluorescein dye effectively highlights corneal integrity changes referred to as corneal staining. This review describes the manifestations, the cause, the mechanisms, and the methods of remediation of corneal staining.

Utility of short-term evaluation of presbyopic contact lens performance

Objectives: To establish if evaluations of multifocal contact lens performance conducted at dispensing are representative of behavior after a moderate adaptation period.

Methods: Eighty-eight presbyopic subjects, across four clinical sites, wore each of four multifocal soft contact lenses (ACUVUE BIFOCAL, Focus Progressives, Proclear Multifocal, and SofLens Multifocal) for 4 days of daily wear. Comprehensive performance assessments were conducted at dispensing and after 4 days wear and included the following objective metrics: LogMAR acuity (contrast, 90% and 10%; illumination, 250 and 10 cd/m2; distance, 6 m, 100 cm, and 40 cm), stereopsis (RANDOT), reading critical print size and maximum speed and range of clear vision at near. Subjective assessments were made, with 100-point numerical rating scales, of comfort, ghosting (distance, near), visual quality (distance, intermediate, and near), and the appearance of haloes. At two sites, subjects (n = 39) also rated visual fluctuation (distance, intermediate, and near), facial recognition, and overall satisfaction.

Results: Among the objective variables, significant differences (paired t test, P<0.05) between dispensing and 4 days were found only for range of clear vision at near (2.9 ± 2.0 cm; mean difference ± standard deviation) and high contrast near acuity in low illumination (-0.013 ± 0.011 LogMAR). With the exception of insertion comfort, all subjective variables showed significant decrements over the same period. Overall satisfaction declined by an average of 10.9 ± 5.1 points.

Conclusions: Early assessment is relatively unrepresentative of performance later on during multifocal contact lens wear. Acuity based measures of vision remain substantially unchanged over the medium term, apparently because these metrics are insensitive indicators of performance compared with subjective alternatives.

Clinical evaluation of long-term users of two contact lens care preservative systems

Purpose: To clinically evaluate long-term users of two different contact lens care preservative systems and to investigate whether prolonged use is associated with an increase in the prevalence of dry eye.

Methods: Eighty-nine wearers of group IV hydrogel or silicone hydrogel lenses participated in this one-visit, investigator-masked study. Subjects were required to have consistently used a polyhexamethylene biguanide (PHMB) or polyquaternium-1 (PQT) based solution for 2 years. Consistent use was defined as 80% for the past 2 years and 100% for the past year. Clinical assessments included: average and comfortable wear time; overall and end-of-day comfort; signs of dryness, discomfort, burning or stinging, grittiness or scratchiness and visual changes; non-invasive and fluorescein break-up-time; pre-ocular tear film lipids, tear meniscus height, Schirmer and fluorescein clearance tests; limbal and bulbar hyperemia; palpebral roughness; corneal and conjunctival staining; lens front surface wetting; and lens film deposits.

Results: Significantly more grittiness or scratchiness was reported by subjects using a PHMB-containing system (67% vs. 44%; P = 0.02). Palpebral roughness and hyperemia were significantly greater in the PHMB group wearing group IV lenses (P = 0.01 and P = 0.05, respectively). Corneal staining was significantly higher in the PHMB users in all four peripheral sectors (P < 0.01). Nasal and temporal conjunctival staining was also significantly higher for users of PHMB-containing systems (P < 0.05). Front surface lens wettability was significantly better for group IV PQT users compared to PHMB users (P = 0.008), with 84% vs. 72%, respectively, with lenses graded by the investigator as having good or excellent wettability. Significantly higher levels of lens front surface film deposits were noted with PHMB users (P = 0.007), with 58% of group IV lenses treated with PHMB compared with 38% of group IV lenses treated with PQT showing some lens front surface film deposition. No significant differences between the two preservative system groups were noted for the range of dry eye evaluations nor the remaining clinical assessments.

Conclusions: Differences in both ocular and lens characteristic were observed between long-term users of two preservative systems used in many contact lens multi-purpose solutions. The findings from this study did not support the hypothesis that prolonged use of PHMB-containing solutions leads to dry eye. Additional studies including a larger sample size and perhaps longer use of the systems could help to further elucidate differences in clinical performance between systems.

A prospective study of the effect of education on non-compliant behaviour in contact lens wear

The contact lens practitioner and patient present a specific case for the study of non-compliance in areas such as hygiene, solution use, appointment attendance and wearing times. Education is one of the factors thought to influence compliance among patients in general health care situations and contact lens practitioners are encouraged to educate patients in the care and maintenance of contact lenses. A prospective, randomized, controlled and double masked study was performed to assess the effect of a‘compliance enhancement strategy’ on levels of compliance among contact lens wearers over twelve months. Eighty experienced contact lens patients were randomly allocated to two experimental groups. A standard level of contact lens instruction was applied to the first group and in addition the compliance enhancement strategy was applied to patients assigned to the second group. The strategy consisted of extra education for patients using a video, booklets, posters, a checklist and a health care contract. Patients were given free supplies of RelMu multipurpose solution and Medalist 38 soft contact lenses IBausch and Lomb, Rochester. New York). Compliance levels were assessed at a twelve month aftercare appointment by demonstration and questionnaire. The results indicate that the compliance enhancement strategy had little significant effect on the compliance levels of the patients to whom it was applied. The population of contact lens wearers were generally very compliant and the contact lenses and care regimen were clinically successful. The possibility that the assessment of non–compliance was not adequately sensitive to highlight small differences in non-compliant, behaviour is discussed. The standard level of eduction applied to this sample of contact lens patients was adequate to ensure generally high levels of compliance with the simple care and maintenance regimen recommended.

A seven year survey of the contact lens prescribing habits of Canadian optometrists

Purpose. Little is known about the contact lens prescribing habits of optometrists in North America. The purpose of this survey was to obtain data on the types of lenses and solutions prescribed by Canadian optometrists.

Methods. One thousand Canadian optometrists were surveyed annually over seven consecutive years (2000 to 2006; n = 7000) on their contact lens prescribing preferences. Each survey requested a range of information about the contact lenses prescribed to the first 10 patients after its receipt.

Results. Over this time period, 1008 (14.4%) of the surveys were returned, providing data on 9383 fits. During the seven-year period, the ratio of male:female fits was 1:2 (3123:6217, 43 not reported), with a mean age of 31.3 ± 13.6 years (range 2 to 82 years). The ratio of new fits to refits was 2:3 (3780:5518, 85 not reported), with 91.3% of all fits being soft contact lenses (SCL). Of the SCL fits, 59.5% were spherical, 28.5% toric, 9.7% multifocal, and 2.3% cosmetic tints. Gas permeable (GP) fits were 46.6% spherical, 18.6% toric, 19.5% multifocal, and 6.6% were for orthokeratology (OK). Over the seven-year period, SCL prescribed for continuous wear (CW) increased from 3.2% to 14.3% between 2000 and 2004 and reduced to 8.1% in 2006, for all fits. The use of mid-water content (MWC) materials decreased from 34.6% to 2.7% and the use of silicone hydrogel (SH) lenses increased from 61.4% to 96.2%, for all CW fits. GP lens continuous wear increased from 0.7% to 30.6% of all GP lens fits by 2006. Daily wear (DW) of SH lenses decreased from 49.6% (2000) to 33.7% (2004) and then increased to 86.1% in 2006, for SH fits. MWC SCL fit on a monthly planned replacement (PR) basis reduced in popularity over the seven-year period (75.0% to 39.9%) and in 2006 more patients were fit overall with SH lenses (42.9%). The use of non-PR SCL declined from 20.5% to 4.5% of all fits. Fitting of low-water content lenses also declined (15.1% to 7.0%). High-water content (5.4% to10.2%) and SH lenses (5.4% to 42.9%) both increased. By 2006, the majority of GP lenses fit were with high Dk (HDK) materials (50.3%).

Conclusions. The preferred contact lens modality for Canadian optometrists appears to be DW SCL, which are replaced monthly. The proportion of lenses used for CW peaked in 2004, with SH SCL being the preferred material. The market share for GP lenses remains relatively unchanged, with an increasing proportion used for OK and CW. The launch of DW SH lenses in 2004 resulted in a marked increase in their reported fits, with a similar effect following the launch of a HDK GP lens material for CW.

Managing the emerging presbyopic contact lens wearer

The article deals with a study that examined the performance of a new silicone hydrogel multifocal contact lens for emerging presbyopes compared to other forms of correction. Study participants were asked to wear a different lens design for a week at a time. They were divided into the asymptomatic group and the symptomatic group. Results of the study showed that 24 participants had no difficulties with near vision tasks. It also found similar ghosting between the multifocal and habitual corrections for the near tasks under low illumination.

Contact lens prescribing in Canada 2011

The annual survey to collect data on the contact lens prescribing preferences of practitioners has continued for 12 years in Canada. Practitioners were surveyed for information on the first 10 patients they fitted with contact lenses immediately after receipt of said survey. A total of 121 completed surveys were returned, detailing contact lens fittings for 1,184 patients.

Of the patients fitted with contact lenses, the results indicated that the majority were prescribed soft lenses. The preferred modality was monthly planned replacement and over 67 per cent of the soft lens fits were made of silicone hydrogel materials. Of the rigid lens fits, the majority were prescribed for daily wear, as the overnight use of rigid lenses appears to be mainly for orthokeratology. Practitioners are recommending multipurpose solutions for the majority of their soft lens patients (85.6%).

International contact lens prescribing

Survey results from six countries provide a snapshot of contact lens prescribing around the world.

International contact lens prescribing in 2004

This article presents our fourth annual survey of international contact lens prescribing trends. In 2004, we analyzed prescribing habits in 14 countries: Australia, Belgium, Canada, Germany, Greece, Italy, Japan, the Netherlands, New Zealand, Norway, Singapore, Sweden, the United Kingdom and the United States. To each, we sent 1,000 surveys (or a pro-rata number in countries with less than 1,000 practitioners) to clinicians randomly selected from appropriate national registers.

The surveys elicited prospective information about contact lenses and care products that respondents prescribed to up to 10 patients fit after the study began. We employed a weighting system to better reflect the trends of busier practices.

International survey of rigid contact lens fitting

To determine the extent of rigid contact lens fitting worldwide and to characterize the associated demographics and fitting patterns. Survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for five consecutive years (2007 to 2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Survey data collected between 1996 and 2011 were also analyzed to assess rigid lens fitting trends in seven nations during this period. Data were obtained for 12,230 rigid and 100,670 soft lens fits between 2007 and 2011. Overall, rigid lenses represented 10.8% of all contact lens fits, ranging from 0.2% in Lithuania to 37% in Malaysia. Compared with soft lens fits, rigid lens fits can be characterized as follows: older age (rigid, 37.3 ± 15.0 years; soft, 29.8 ± 12.4 years); fewer spherical and toric fits; more bifocal/multifocal fits; less frequent replacement (rigid, 7%; soft, 85%); and less part-time wear (rigid, 4%; soft, 10%). High-Dk (contact lens oxygen permeability) (36%) and mid-Dk (42%) materials are predominantly used for rigid lens fitting. Orthokeratology represents 11.5% of rigid contact lens fits. There has been a steady decline in rigid lens fitting between 1996 and 2011. Rigid contact lens prescribing is in decline but still represents approximately 10% of all contact lenses fitted worldwide. It is likely that rigid lenses will remain as a viable, albeit increasingly specialized, form of vision correction.