Rigid gas permeable contact lenses: Out in the cold

Introduction

Rigid gas permeable (RGP) contact lens wearers may experience episodes of lens fracture during handling. In this paper, we report the case of a keratoconic contact lens wearer whose lens fractured whilst being handled at sub-zero temperatures. Subsequent studies illustrate how PMMA and RGP contact lenses behave when exposed to sub-zero temperatures.

Methods

Using a previously validated custom-built strain gauge we have measured the force required to invert RGP contact lenses (Fluroperm, DK30-DK151, PMMA and Aquasil; dioptric power −2.00DS) under different temperature conditions.

Results

It was found that RGP lenses, frozen to −7 °C, required on average 15% less force to cause inversion than when stored at room temperature, regardless of material. It was also found that without due care, lenses of all materials fractured more easily after having been frozen, than lenses kept at room temperature. Fracture rates rose from 8% to 83% if lenses were stored wet (at −7 °C) as opposed to dry.

Conclusion

The authors conclude that practitioners should consider inappropriate contact lens storage and handling as a possible reason for otherwise unexplained acute RGP contact lens fracture.     

Trends in Contact Lens Prescribing in Japan (2003–2016)

Purpose

To review contact lens prescribing trends in Japan between 2003 and 2016.

Determination of central corneal clearance in scleral lenses with an optical biometer and agreement with subjective evaluation

PurposeTo compare three methods to measure central corneal clearance (CCC) during scleral lens wear: subjective (slit lamp), image processed (ImageJ) and with an optic biometer. The optic biometer technique was validated in comparison to an OCT in the first part of the study.MethodsTwenty-two eyes (11 subjects) with healthy corneas were recruited. Three measures of OCT with scleral lens and ten measurements of axial length (AL) with IOLMaster with and without lens were performed. For the second part, 61 eyes (35 subjects) enrolled in a clinical study were selected. Measurements of CCC were done with IOLMaster, SlitLamp and ImageJ.ResultsThe measurements of CCC indirectly obtained with IOLMaster had a strong correlation with AS-OCT measurements (r = 0.981), showing a mean difference of 122.18 ± 46.05 μm (higher with IOLMaster). Regarding the second part, measurements of CCC were 238.66 ± 95.94 μm, 250.16 ± 124.31 μm and 263.15 ± 90.60 μm, for the IOLMaster, SlitLamp and ImageJ, respectively. The correlations were higher for ImageJ vs Subjective measure (r = 0.891) than for IOL vs Subjective (r = 0.748) and IOL vs ImageJ (r = 0.745). Analysis of differences and correlations between SlitLamp and ImageJ through time showed a mean difference of -32.28 ± 89.95 μm (r = 0.683) at V1month, 12.53 ± 59.46 μm (r = 0.850) at V6months and 11.57 ± 32.95 μm (r = 0.940) at V12months.ConclusionsIt is possible to measure CCC with IOLMaster, considering AL measured with and without lens and lens thickness. The three methods tested have good correspondence, showing that IOLMaster and ImageJ could be objective techniques to measure CCC. Also, it is possible to improve the agreement of subjective measures when compared to objective measures trough time.     

Factors influencing the 8-item contact lens dry eye questionnaire score and comparison of translations in Japanese soft contact lens wearers

PurposeTo determine (1) the factors associated with a high degree of self-reported symptoms with Japanese translations of the 8-Item Contact Lens Dry Eye Questionnaire (J-CLDEQ-8) in a cross-section of soft contact lens (SCL) wearers in Japan and (2) whether the difference in translation of the CLDEQ-8 affects the scores between validated and non-validated versions of the Japanese translation.MethodsHabitual SCL wearers completed the validated J-CLDEQ-8 and a previous non-validated version. Demographics and SCL history questions were queried when they presented for routine eye care in nine geographically distinct clinics across Japan. The following risk factors for high J-CLDEQ-8 scores (≥11) were tested: sex, age, SCL replacement (daily disposable vs. bi-weekly and monthly reusable), years of SCL wear, and self-reported use of rewetting drops. The scores of the validated and non-validated questionnaires were compared.ResultsSignificant patient-related risk factors for high J-CLDEQ-8 scores were female sex, use of reusable SCLs, longer years of SCL wear, and use of rewetting drops. Scores for six out of eight questions in the validated J-CLDEQ-8 were significantly higher than those of the non-validated version, resulting in a significant difference in the average total score between the two questionnaires (validated J-CLDEQ-8: 10.5 ± 5.9 vs non-validated J-CLDEQ-8: 9.5 ± 5.8, P < 0.001).ConclusionsFemale sex, use of reusable SCLs, longer years of SCL wear, and use of rewetting drops were significant risk factors for high J-CLDEQ-8 scores in a cross-sectional clinical population of Japanese SCL wearers. Symptoms with SCL are not predicted by age and must therefore be queried at follow-up visits for all SCL wearers. Differences in the two translations affected the ability of the questionnaire to identify individuals with high symptoms associated with SCL wear.     

Quarter of a century of contact lens prescribing trends in the United Kingdom (1996 – 2020)

PurposeTo document contact lens prescribing trends in the United Kingdom over the past quarter of a century.MethodsAn annual survey of contact lens prescribing was conducted each year from 1996 to 2020, inclusive, by asking a random selection of optometrists and contact lens opticians to provide information relating to 10 consecutive contact lens fits between January and March.ResultsOver the 25 year survey period, 2,671 practitioners returned survey forms, reporting a total of 25,575 contact lens fits. The mean (± standard deviation) age of lens wearers was 35 ± 15 years, of which 64 % were female. Over the survey period, rigid lens new fits decreased from 22 % to 2%. The prescribing of silicone hydrogel lenses has increased steadily since their introduction towards the end of the 1990s, and now represent 80 % of soft lens fits. Soft toric lens prescribing has gradually increased to 47 % – a value at which astigmatism ≥ 0.75DC is theoretically corrected in all contact lens wearers. Daily disposable prescribing increased steadily over the survey period and now represents 63 % of lenses prescribed. Extended wear fits remain at very low levels, except for some prescribing for overnight orthokeratology. Multi-purpose lens care solutions are ubiquitous; peroxide and other systems are now seldom prescribed. Rigid lenses and monthly replacement soft lenses are predominantly worn on a full time basis, whereas daily disposable soft lenses are mainly worn part time.ConclusionsThis report documents the evolution of contact lens fitting in the United Kingdom over the past 25 years. The most likely lens fit is a spherical design silicone hydrogel daily disposable contact lens prescribed for a 35 year old female and worn on a part-time basis.     

Scleral lens fitting and assessment strategies

PurposeTo describe prescriber reported scleral lens fitting and assessment strategies.MethodsThe SCOPE (Scleral Lenses in Current Ophthalmic Practice Evaluation) study group designed and administered an IRB approved, electronic survey (REDCap) regarding current scleral lens fitting and assessment methods. The survey was distributed to attendees of the 2017 Global Specialty Lens Symposium.Results95 practitioners responded to the survey. Over half of the respondents, 58% (55/95) reported fitting scleral lenses for less than five years (new prescribers), and 42% (40/95) reported fitting scleral lenses for more than five years (experienced prescribers). There was a statistically significant difference between their initial use of technology (χ² = 21.117, p < 0.0005) in selection of a diagnostic lens. New prescribers consider base curve first (60%, 33/55), while experienced prescribers considered sagittal depth first (63%, 25/40) in their initial scleral lens selection. All of the experienced lens prescribers (100%, 39/39) reported estimating central clearance by comparing thickness of the post-lens tear reservoir to scleral lens thickness using a slit lamp beam at least some of the time, and 62% of new scleral lens prescribers (34/55; χ² = 19.175, p < 0.0005) reported doing so. All (100%, 40/40) experienced prescribers schedule scleral lens follow-ups at a specific time and assess conjunctival compression (100%, 40/40), conjunctival staining (100%, 39/39), and corneal staining (100%,40/40) after lens removal.ConclusionsPractitioners with varying backgrounds and experience have added sclerals to their lens inventories. However, definite guidelines for fitting have not been developed. The results of a survey are provided; demonstrating that among practitioners with greater than 5 years of scleral lens experience, a consensus has emerged for best practices. Strategies for lens evaluation, which may inform future efforts at generating scleral fitting standards are described.     

Bitoric rigid gas permeable contact lenses in the optical management of penetrating keratoplasty

PurposeThe purpose of this study was to evaluate the complexity and effectiveness of fitting bitoric rigid gas permeable contact lenses (RGPCLs), compared to spherical RGPCLS, when used in the correction of high amounts of post-penetrating keratoplasty astigmatism.MethodsRecords of post-penetrating keratoplasty (PKP) patients being managed with bitoric RGPCLs were compared to controls (post-PKP patients managed with spherical RGPCLs). Factors that were analyzed included the number of diagnostic RGPCLs used to assess the initial fit, the number of RGPCLs ordered to finalize the fit and the number of total doctor visits to finalize the fit.ResultsFourteen eyes of 14 patients satisfied the study criteria. The average amount of total astigmatism in this study group was 10.0 D ± 5.0 compared to the control group which was 3.3 D ± 2.6. The number of diagnostic RGPCLs used for the study group was 1.2 ± 0.4 compared to 1.0 ± 0.0 for the control group. The mean number of contact lenses ordered to complete the fitting for the study group was 1.9 ± 0.7 compared to the control which was 2.1 ± 0.8. The study group presented for an average of 6.3 ± 1.6 visits whereas the control group presented for 4.9 ± 1.1 visits. Contact lens corrected acuity for the study group was 0.101 ± 0.11 (20/25) compared to the control group 0.08 ± 0.12 (20/24).ConclusionsThe complexity of fitting bitoric RGPCLs was found to be similar to fitting spherical RGPCLs on post-PKP eyes and the visual outcomes were not different.     

A one-year prospective study on scleral lens wear success

PurposeTo report the success rate of scleral lens wear and the lens handling learning curve from the wearers perspective.MethodsNinety-five participants were consecutively screened for enrollment in a prospective study. Participants were divided into two groups: ICGroup (71 participants with irregular corneas) and RCGroup (24 participants with regular corneas). Participants attended several visits: Baseline, Lens Dispense Visit (LDV), 1-month, 3-month, 6-month and 12-month follow-ups. The number and causes of scleral lens discontinuation and the time to correctly apply the lens for the first time at the LDV were evaluated. During follow-ups, participants answered a questionnaire regarding scleral lens wear (mean number of hours/day and days/week of lens wear, methods used for handling, number of attempts to correctly apply and remove the lenses).ResultsSixty-nine participants (73 %) successfully completed the 12-month period. Twenty-six participants (27 %) discontinued scleral lens wear. None of the discontinuations were due to adverse events. The success rate (number of participants that wore the lenses for the 12 months) was 77 % in ICGroup and 58 % in RCGroup. The main reasons for scleral lens discontinuation were handling issues (35 %) and discomfort (19 %). 36 % of participants required <15 min to correctly apply the lens at the LDV, however 13 % required >60 min (participants that wore spectacles, soft lenses or had no correction method at Baseline). The mean wearing time (hours/day and days/week) increased significantly from 1-month to 12-month appointments: from 9.8–11.1 h and 5.1–5.6 days in new scleral lens wearers, while the number of attempts to correctly apply and remove the lenses decreased significantly.ConclusionsThe success rate was 73 % during this prospective 12-month follow-up study. The main reasons for drop-out were handling issues and discomfort. Participants who continued scleral lens demonstrated increased handling skills.     

Refractive lens exchange for presbyopia

True presbyopia correction still remains one of the main challenges amongst eye professionals. Many corrective techniques exist including bifocal spectacle correction, monovision techniques both with corrective lenses and surgery, multifocal corneal excimer laser and refractive lens exchange with either accommodating or multifocal lenses. Refractive lens exchange was first described more than 10 years ago and has become more accepted in recent years with advancements in lens technology and improvements in surgical techniques. This article reviews developments in this field and current available lens options in the treatment of presbyopia.     

Efficacy of spherical aberration correction based on contact lens power

PurposeTo investigate the efficacy of spherical aberration (SA) correction with aspheric contact lenses (aspheric lenses) based on lens power, and compare the results with those of spherical contact lenses (spherical lenses).MethodsOcular higher-order aberrations were measured with a wavefront sensor, in 11 myopic subjects wearing an aspheric lens (Medalist Fresh fit (PUREVISION 2 HD); Bausch + Lomb) or a spherical lens (ACUVUE Oasys; Johnson & Johnson). Six different lens powers (−7.00 diopters (D), −5.00 D, −3.00 D, −1.00 D, +1.00 D, +3.00 D) were used for all subjects. The amount of SA correction from the contact lens at each power was calculated as the difference between SA with the contact lens on-eye and SA of the eye alone.ResultsFor the spherical lenses, SA correction was close to 0.00 μm for the +1.00 D lens, became more positive as the labeled lens power increased and became more negative as the labeled lens power decreased. For the aspheric lenses, SA correction was consistent, from −0.15 to −0.05 μm, for all lens powers except for the −1.00 D lens. SA correction for the spherical and aspheric lenses was significantly different at −7.00 D (p = 0.040), −3.00 D (p = 0.015), −1.00 D (p < 0.001), +1.00 D (p = 0.006), and +3.00 D (p < 0.001) powers.ConclusionAn aspheric lens is capable of correcting SA at different lens powers, and has SA correction in the range of −0.15 to −0.05 μm over a 6 mm aperture.     

Colonization of therapeutic contact lens by dematiaceous fungi

PurposeTo report 2 patients with colonization of therapeutic contact lens with dematiaceous fungi.MethodsCase report.ResultsThe first patient had a retained soft contact lens on an opaque cornea for 4 years with brownish black multiple colonies on the soft contact lens and culture grew Bipolaris spp. The second patient was on therapeutic contact lens for pseudophakic bullous keratopathy for 4 months and developed a brownish colonization of contact lens with unidentified dematiaceous fungi. Both the patients had conjunctivitis but did not develop fungal keratitis.ConclusionJudicious use of therapeutic contact lens is required in agrarian countries with adequate emphasis on strict adherence to the standard protocols and frequent replacement of the lens.     

How often are contact lenses worn?

There are important clinical, academic and commercial reasons for seeking to develop a comprehensive understanding of the frequency of wear of different forms of contact lenses. Data that we have gathered from annual contact lens fitting surveys over the past 12 years demonstrate that contact lenses are worn, on average, 5.4 ± 1.9 days per week. Rigid lenses tended to be worn on a full-time basis, typically seven days per week. The distribution of daily disposable lens wear is bimodal, with peaks at two days and seven days per week of wear. Over the survey period there appears to have been a small trend toward the use of contact lenses on a part-time basis.     

BCLA CLEAR – Medical use of contact lenses

The medical use of contact lenses is a solution for many complex ocular conditions, including high refractive error, irregular astigmatism, primary and secondary corneal ectasia, disfiguring disease, and ocular surface disease. The development of highly oxygen permeable soft and rigid materials has extended the suitability of contact lenses for such applications. There is consistent evidence that bandage soft contact lenses, particularly silicone hydrogel lenses, improve epithelial healing and reduce pain in persistent epithelial defects, after trauma or surgery, and in corneal dystrophies. Drug delivery applications of contact lens hold promise for improving topical therapy. Modern scleral lens practice has achieved great success for both visual rehabilitation and therapeutic applications, including those requiring retention of a tear reservoir or protection from an adverse environment. This report offers a practical and relevant summary of the current evidence for the medical use of contact lenses for all eye care professionals including optometrists, ophthalmologists, opticians, and orthoptists. Topics covered include indications for use in both acute and chronic conditions, lens selection, patient selection, wear and care regimens, and recommended aftercare schedules. Prevention, presentation, and management of complications of medical use are reviewed.     

The use of contact lens telescopic systems in low vision rehabilitation

Refracting telescopes are afocal compound optical systems consisting of two lenses that produce an apparent magnification of the retinal image. They are routinely used in visual rehabilitation in the form of monocular or binocular hand held low vision aids, and head or spectacle-mounted devices to improve distance visual acuity, and with slight modifications, to enhance acuity for near and intermediate tasks. Since the advent of ground glass haptic lenses in the 1930’s, contact lenses have been employed as a useful refracting element of telescopic systems; primarily as a mobile ocular lens (the eyepiece), that moves with the eye. Telescopes which incorporate a contact lens eyepiece significantly improve the weight, comesis, and field of view compared to traditional spectacle-mounted telescopes, in addition to potential related psycho-social benefits. This review summarises the underlying optics and use of contact lenses to provide telescopic magnification from the era of Descartes, to Dallos, and the present day. The limitations and clinical challenges associated with such devices are discussed, along with the potential future use of reflecting telescopes incorporated within scleral lenses and tactile contact lens systems in low vision rehabilitation.     

Contact lens complications among wearers in Ghana

PurposeContact lens (CL) practice is relatively new in Ghana; a country where the geographical location (warm climate) lends itself to harsh environmental conditions (high humidity) known to influence CL wear. Recent studies suggest an increase in CL wear (corrective and cosmetic), yet, there are no studies about CL-related complications. This study sought to determine the complications associated with CL wear in Ghana.MethodsThis was a retrospective cohort study. The medical records of contact lens wearers from five CL clinics in the two largest metropolises in Ghana, Accra and Kumasi, were reviewed. Included in the study were records of individuals who visited the clinics within the period of 2013–2016. Data on patients with contact lens-related complications were analyzed.ResultsThe prevalence of CL complications was 29.06 %. The mean ± SD age of patients with CL complications was 35 ± 15 years. Contact lens complications were more common in females (52.90 %). The majority of complications were in soft contact lens wearers (82.35 %). Refractive error correction was the most common indication for CL wear (61.76 %) among those with complications, followed by keratoconus (14.71 %), scarred blind eye (14.71 %), corneal ulcer (5.88 %) and anterior staphyloma (2.94 %). Contact lens complications reported were giant papillary conjunctivitis (41.18 %), corneal infiltrates (23.53 %), bacterial keratitis (14.71 %), corneal abrasion (11.76 %), dry eye (5.88 %) and corneal oedema (2.94 %). The causes of CL complication were inappropriate lens cleaning (29.41 %), poor hygiene (23.53 %), overnight contact lens wear (17.64 %), poor lens fit (14.71 %) and reaction to contact lens solution (14.71 %).ConclusionContact lens complications were more common in soft contact lens wearers in Ghana. Giant papillary conjunctivitis was the most common contact lens complication reported. Adherence to CL wear care regimen and good personal hygiene may prevent the majority of CL complications observed in Ghana.     

The 75th anniversary of the Tuohy corneal contact lens: A review

The aim of this review is to mark the 75th anniversary of the introduction of the original corneal contact lens of Tuohy in 1948.American documents in the public domain, such as census records and draft registration cards, were consulted in order to provide a more comprehensive biography of Kevin M Tuohy, inventor of the corneal contact lens, than those previously published.Perhaps due to a failure to consult original sources concerning the Tuohy corneal lens, some historical accounts have provided incomplete or incorrect information about its design and dimensions. The back surface specification of the bi-curve Tuohy lens in its standard diameter of 11.50 mm has been tabulated and edge lift and edge clearance values calculated. A colour photograph illustrates the fluorescein pattern of a Tuohy lens.Patients wearing Tuohy lenses were able to achieve a much longer wearing time compared to those wearing sealed scleral lenses since they eliminated corneal epithelial oedema, a frequent problem which necessitated removal of lenses after a few hours of wear due to cloudy vision. Only some of Tuohy lens wearers exhibited an adverse corneal response such as fluorescein staining after 12, or more, hours of wear.The clinical success of the Tuohy lens and the fact that its fitting procedure was simpler and quicker than that for scleral lenses encouraged optometrists to commence contact lens practice and to implement improvements in the design of the corneal lens.