Applanation tonometry in silicone hydrogel contact lens wearers

INTRODUCTION: Previous studies have investigated intraocular pressure (IOP) measurements through conventional soft (hydrogel) therapeutic contact lenses, and have found that an accurate IOP can be recorded in normal eyes, and in eyes with abnormal anterior segments. The IOP measurement through soft contact lenses may be affected by the water content and centre thickness of the lens. Silicone hydrogel contact lenses are now being used as therapeutic contact lenses due to their high oxygen permeability. The purpose of this study is to investigate if IOP can be accurately measured in a subject wearing a silicone hydrogel contact lens. METHODS: In a cohort study, the IOP was measured with a Goldmann applanation tonometer without a contact lens and then repeated with a hydrogel contact lens in situ. RESULTS: The IOP of 20 eyes of 10 volunteers with no ocular pathology was measured. The mean difference (+/-S.D.) found between IOP measurement with (mean 15.55+/-1.70 mmHg) and without (mean 16.05+/-1.90 mmHg) contact lens was found to be -0.5+/-0.89 mmHg. Statistical analysis was performed which revealed a correlation coefficient of 0.89. No significant statistical difference was found between the two groups with paired t-test (p=0.19). CONCLUSION: Accurate measurement of IOP by applanation tonometry can be achieved through a silicone hydrogel contact lens.     

The effect of hydrogel and silicone hydrogel contact lenses on the measurement of intraocular pressure with rebound tonometry

Purpose

To assess the accuracy of intraocular pressure (IOP) measurements using rebound tonometry over disposable hydrogel (etafilcon A) and silicone hydrogel (senofilcon A) contact lenses (CLs) of different powers.

Methods

The experimental group comprised 36 subjects (19 male, 17 female). IOP measurements were undertaken on the subject's right eyes in random order using a rebound tonometer (ICare). The CLs had powers of +2.00D, −2.00D and −6.00D. Six measurements were taken over each contact lens and also before and after the CLs had been worn.

Results

A good correlation was found between IOP measurements with and without CLs (all r ≥ 0.80; p < 0.05). Bland Altman plots did not show any significant trend in the difference in IOP readings with and without CLs as a function of IOP value. A two-way ANOVA revealed a significant effect of material and power (p < 0.01) but no interaction. All the comparisons between the measurements without CLs and with hydrogel CLs were significant (p < 0.01). The comparisons with silicone hydrogel CLs were not significant.

Conclusions

Rebound tonometry can be reliably performed over silicone hydrogel CLs. With hydrogel CLs, the measurements were lower than those without CLs. However, despite the fact that these differences were statistically significant, their clinical significance was minimal.     

The accuracy of Goldmann applanation tonometry over silicone hydrogel contact lenses in patients with glaucoma

PurposeTo investigate the accuracy of measuring intraocular pressure over a silicone hydrogel contact lens using Goldmann applanation tonometry in eyes with glaucoma.MethodsThis was a prospective, randomized study and enrolled 28 patients (28 right eyes) with primary open angle glaucoma. Intraocular pressure was taken with and without a silicone hydrogel contact lens (−0.50 D), in situ (using Goldmann applanation tonometry), in a randomized order of measurements. Statistical analysis was performed using paired t-test and Bland–Altman plot.ResultsThe mean difference (± standard deviation) found between intraocular pressure measurement without (mean 16.7 ± 3.2 mmHg) and with (mean 17.3 ± 3.0 mmHg) contact lens was found to be −0.57 ± 2.3 mmHg (95% confidence interval, −1.5 to 0.3). No significant statistical difference was found between the two groups with paired t-test (p = 0.19). The Bland Altman plot showed some evidence of increasing variability of differences between two measures of intraocular pressure, with increasing intraocular pressure. The 95% limits of agreement of the Bland Altman plot were unacceptably large (−5 mmHg to 3.9 mmHg).ConclusionAgreement between Goldmann applanation tonometry with and without contact lenses seems to be poor in patients with glaucoma, especially for high intraocular pressure.     

Non-contact tonometry over soft contact lenses: effect of contact lens power on the measurement of intra-ocular pressure.

PURPOSE: To perform non-contact applanation tonometry over soft contact lenses and to examine any differences between the measured IOPs with and without the contact lens. METHOD: IOP was measured at one eye of eight subjects and re-evaluated through a soft lens in situ over the cornea. Seventy percent (ES70, Lunelle) water contact lenses or powers ranging from -15.00 D to +13.00 D were used. RESULTS: Mean IOP without lenses was 15.2 mmHg (S.D. = +/-4.2) and this did not change significantly for lenses ranging from -15.00 D to +3.00 D (P > 0.01) but did change for lens powers +6.00 D and above (P<0.01). The least squares line describing the change in measured IOP (deltaIOP) as a function of lens power (x) has the following characteristics, deltaIOP = 0.022 + 0.591x + 0.11x2 + 0.005x3 (r = 0.985, P = 0.0001). CONCLUSION: Non-contact tonometry can be performed with sufficient accuracy over a soft lens on condition: (a) lens centre thickness is no more 0.30 mm and (b) power is not greater than +3D.     

The relationship between measurement method and corneal structure on apparent intraocular pressure in glaucoma and ocular hypertension

PurposeTo analyse the relationship between measured intraocular pressure (IOP) and central corneal thickness (CCT), corneal hysteresis (CH) and corneal resistance factor (CRF) in ocular hypertension (OHT), primary open-angle (POAG) and normal tension glaucoma (NTG) eyes using multiple tonometry devices.MethodsRight eyes of patients diagnosed with OHT (n = 47), normal tension glaucoma (n = 17) and POAG (n = 50) were assessed. IOP was measured in random order with four devices: Goldmann applanation tonometry (GAT); Pascal^® dynamic contour tonometer (DCT); Reichert^® ocular response analyser (ORA); and Tono-Pen^® XL. CCT was then measured using a hand-held ultrasonic pachymeter. CH and CRF were derived from the air pressure to corneal reflectance relationship of the ORA data.ResultsCompared to the GAT, the Tonopen and ORA Goldmann equivalent (IOPg) and corneal compensated (IOPcc) measured higher IOP readings (F = 19.351, p < 0.001), particularly in NTG (F = 12.604, p < 0.001). DCT was closest to Goldmann IOP and had the lowest variance. CCT was significantly different (F = 8.305, p < 0.001) between the 3 conditions as was CH (F = 6.854, p = 0.002) and CRF (F = 19.653, p < 0.001). IOPcc measures were not affected by CCT. The DCT was generally not affected by corneal biomechanical factors.ConclusionThis study suggests that as the true pressure of the eye cannot be determined non-invasively, measurements from any tonometer should be interpreted with care, particularly when alterations in the corneal tissue are suspected.     

Masked comparison of two silicone hydrogel bandage contact lenses after photorefractive keratectomy

PurposeTo compare the efficiency and safety of two bandage contact lenses after photorefractive keratectomy (PRK).MethodsIn this double-blind study, 45 patients (90 eyes) received PRK in both eyes and wore bandage contact lenses (BCLs), PureVision (Bausch & Lomb, Rochester, NY, USA) in one eye and PureVision2 (Bausch & Lomb, Rochester, NY, USA) in the other eye, randomly assigned. The medication regimen after surgery was the same for both eyes. The epithelial defect's size, conjunctival hyperemia and lens centration were graded objectively using slit-lamp biomicroscopy on days 1, 3 and 5 after surgery. Also ocular symptoms of discomfort including tearing, photophobia, foreign body sensation and visual fluctuations were assessed subjectively at each visit.ResultsThe mean epithelial defect size on the first day after operation was similar in eyes fitted with PureVision (30.08 ± 5.30 mm²) and PureVision2 (30.25 ± 5.72 mm²) lenses. (p = 0.79) Contact lens deposits and bulbar hyperaemia on days 1 and 3 after PRK were similar between the two eyes, but were significantly greater on day 5 for PureVision2 lenses. (p = 0.02; p = 0.04 respectively) There was no difference in contact lens decentration, and discomfort symptoms including pain, tearing, foreign body sensation, photophobia and visual fluctuations between the eyes fitted with PureVision and PureVision2. (p > 0.05)ConclusionsPureVision and PureVision2 contact lenses are equivalent as bandage lenses in important aspects such as corneal re-epithelialization and subjective comfort., although PureVision2 led to a higher incidence of contact lens deposits and conjunctival hyperemia early post-PRK.     

Clinical evaluation of different types of contact lenses in keratoconus management

PurposeTo compare the clinical and topographical findings of the keratoconus patients according to the prescribed contact lens type and to investigate the effects of corneal collagen cross-linking (CXL) and cone location on lens selection.MethodsThe records of 301 eyes of 195 keratoconus patients who were prescribed contact lenses were analyzed retrospectively. The eyes were grouped according to the lens type: Soft toric contact lens (STCL), rigid gas-permeable contact lens (RGPCL), hybrid contact lens (HCL) and mini-scleral contact lens (MSCL). The history of having CXL, ophthalmological examination findings, and the topographical findings were compared between the groups. Brown-Forsythe, Chi-square, and post-hoc tests were used to compare the groups. Mann-Whitney U test was used for subgroup analysis. Comparison of the lens-corrected visual acuity (LCVA) and spectacle-corrected visual acuity (SCVA) levels was made with Wilcoxon signed-ranks test.ResultsThere was no significant difference between the groups regarding topographical cone location, CXL history, spherical refraction, and LCVA. The difference between spectacle-corrected visual acuity and LCVA was higher in RGPCL and MSCL groups than STCL group (p=0.01). Keratometry of RGPCL and MSCL groups were higher than STCL and HCL groups (p=0.01, p<0.001). In RGPCL group, eyes with central cones had a higher increase in visual acuity with contact lenses compared to eyes with paracentral cones (p=0.043). STCL and MSCL were mostly prescribed in mild and severe keratoconic eyes, respectively. In RGPCL group, the increase in visual acuity with contact lens was higher in eyes treated with CXL (p= <0.01).ConclusionsWhile STCL and HCL were mostly prescribed in mild keratoconus, RGPCL and MSCL were selected for moderate or advanced disease. If appropriately chosen, all types of contact lenses could result in a good visual acuity level. CXL history did not affect the prescribed lens type. Having central cone location and CXL history in RGPCL group improved visual acuity more efficiently.     

Intraocular pressure changes in neophyte scleral lens wearers: A prospective study

PurposeTo examine the variation in intraocular pressure (IOP) during the first six months of scleral lens wear.MethodsThirty-two neophyte scleral lens wearers were recruited and IOP was measured using Goldman applanation tonometry before, and after 1 and 6 months of scleral lens wear (following lens removal). All scleral lenses were designed based on scleral topography or an impression of the ocular surface. Central corneal thickness and the central post-lens fluid reservoir thickness were quantified using optical coherence tomography.ResultsPost-lens removal IOP displayed an increasing trend after 1 and 6 months of lens wear, but the magnitude of change was not clinically or statistically significant using several repeated measures analyses to account for sporadic missing longitudinal data (mean increase of 1 mmHg or less, p > 0.05). Central corneal thickness and the central post-lens fluid reservoir remained stable throughout the first six months of lens wear.ConclusionIOP measured following lens removal did not vary significantly during the first 6 months of lens wear in scleral lens neophytes. Further research is required to determine if IOP varies during lens wear, following lens removal, or after longer-term lens wear due to suction forces or tissue compression beneath the landing zone.     

Utility of a semi-scleral contact lens design in the management of the irregular cornea

ObjectivesTo evaluate the utility of the Rose K2 XL semi-scleral contact lens (Menicon Co. Ltd., Nagoya, Japan) in the management of the irregular cornea.MethodsTwenty-seven subjects (34 eyes) with irregular corneas referred for contact lens fitting were evaluated. A diagnostic trial set was used in the fitting process. Once the trial lens was considered optimal, a final lens was ordered from the manufacturer with the necessary changes in power, edge lift and diameter. We analyzed visual acuity, number of lenses ordered and patients’ ability to wear and handle lenses.ResultsTwenty-three subjects (30 eyes) were fitted with the Rose K2 XL lens. Four subjects (4 eyes) decided not to conclude the fitting process for different reasons. Average logMAR visual acuity without correction and with the lens was 0.82 and 0.09, respectively (p < 0.001). An average of 1.4 ordered lenses (range 1–3) were necessary to achieve the optimal fit. Nineteen eyes (63%) were fitted with the first lens ordered. Three subjects (13%) had problems with lens handling, and three subjects (4 eyes) abandoned the wear of the lenses after three months due to discomfort (3 eyes) and unsatisfactory visual acuity (1 eye), respectively. Follow-up ranged from 6 to 9 months.ConclusionRose K2 XL semi-scleral contact lens provides good visual acuity and comfort in patients with irregular corneas.     

Corneal biomechanical properties: Precision and influence on tonometry

PurposeTo assess the precision and reproducibility of the corneal biomechanical parameters, and their relationships with the intraocular pressure (IOP) measured with the Goldmann tonometer and a noncontact tonometer.MethodsReadings for biomechanical properties and for IOP measured with the Goldmann and noncontact tonometers, were taken on one randomly selected eye of 106 normal subjects, on each one of two measurement sessions. Measurements with the ocular response analyzer (ORA) and the noncontact tonometer were randomized, followed by the measurement of central corneal thickness and with the Goldmann tonometer.ResultsRepeatability coefficients for CCT, corneal hysteresis (CH) and corneal resistance factor (CRF) in Session 1 were ±0.01 μm, ±3.05 mmHg and ±2.62 mmHg, respectively. The mean CCT, CH, CRF, Goldmann and noncontact tonometry did not vary significantly between sessions. Reproducibility coefficients for CCT, CH and CRF were ±0.02 μm, ±2.19 mmHg and ±1.97 mmHg, respectively. Univariate regression analysis showed that CCT, CH and CRF significantly (P < 0.0001) correlated with the IOP measured with the Goldmann and noncontact tonometers (and with the differences between tonometers) in Session 1. There were no significant correlations with the differences between tonometers in Session 2. Multivariate analysis revealed a minimal effect of CCT on Goldmann measurements but a significant effect on those of the noncontact tonometer.ConclusionsMeasurement of the biomechanical properties of the cornea, using the ORA, are repeatable and reproducible, affect Goldmann tonometry less than noncontact tonometry, and have a minimal influence on the difference in measured intraocular pressure between tonometers.     

Intraocular pressure measurement with ocular response analyzer over soft contact lens

PurposeTo compare intraocular pressure (IOP) measured with ocular response analyzer (ORA) with and without soft contact lenses (CL) on eye.MethodsGoldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) were measured in 56 eyes of 28 subjects without any ocular pathology, using ORA. One eye was fitted with Narafilcon A (1-Day Acuvue True Eye, Johnson & Johnson) and the other eye with Nelfilcon A (Daily AquaComfort Plus, Ciba Vision), each with −3.00D and IOPg and IOPcc were again measured over CL. The variation in the IOP with and without CL was determined.ResultsOut of 28 subjects, 54% (15) were female. Mean age of the subjects was 29.4 ± 9.8 years. Both the IOPg and IOPcc when measured with CL, were found statistically significantly lower than without CL (p < 0.05). In subjects wearing Narafilcon A lens, IOPg and IOPcc were found 0.88 ± 2.04 mmHg and 1.55 ± 2.16 mmHg lower than without CL, respectively. Similarly, with Nelfilcon A lens, IOPg and IOPcc were found to be 1.03 ± 1.93 mmHg and 1.62 ± 3.12 mmHg lower, respectively. IOPcc was highly affected and underestimated by more than 3 mmHg in upto 36% of the subjects.ConclusionMeasurement of IOP over minus (−3.00D) CL with ORA is dependent upon CL properties when measured in normal IOP population. It showed lower IOP over Narafilcon A and Nelfilcon A soft CL in comparison to the pressures measured without lenses. IOPg was found less affected by CL. For the accurate measurement of IOP with ORA, CL should be removed.     

Influence of lens material and intra-ocular pressure on the outcome of non-contact tonometry over soft contact lenses

Purpose

To quantify the influence of soft lens rigidity and power on the difference between intraocular pressure values (ΔIOP) obtained by non-contact tonometry through soft lenses in situ and over the cornea (IOP).

Methods

Both eyes of 25 patients, attending for either routine contact lens check up, were fitted with a (I) low water content silicone hydrogel lenses of relatively high modulus of rigidity (modulus of rigidity 1.2 MPa, Focus Night and Day, Cibavision) and (II) high water content daily disposable of relatively low modulus of rigidity (0.91 MPa, Focus Dailies, Cibavision). IOP measurements were taken over the cornea and repeated over the lens after insertion. Lens powers ranged from −7.50 D to +6.00 D.

Results

ANOVA revealed ΔIOP was associated with both lens power and material (p < 0.05). Multiple linear regression revealed relationships between ΔIOP (y) lens power (x₁) and IOP (x₂) as follows

(I), right eyes,

y = 0.899x₁ − 0.172x₂ + 5.659 (F = 15.615, r = 0.766, p < 0.001, n = 25)

(I), left eyes,

y = 0.993x₁ − 0.101x₂ + 4.694 (F = 23.368, r = 0.825, p < 0.001, n = 25)

(II) right eyes,

y = 0.399x₁ − 0.370x₂ + 6.595 (F = 11.804, r = 0.719, p < 0.001, n = 25)

(II) left eyes,

y = 0.561₁ − 0.225x₂ + 4.153 (F = 28.736, r = 0.723, p < 0.001, n = 25)

Conclusion

ΔIOP appears to be related to lens power, material and to a lesser extent IOP. Practitioners should derive their own empirical relationship between ΔIOP, lens power and IOP for the specific types of soft lenses they commonly use. This would improve efficiency in the screening of IOP in more susceptible soft lens wearers.     

Spherical aberration in contact lens wear

INTRODUCTION: The aim of the present studies was to investigate the effect on spherical aberration of different non custom-made contact lenses, both with and without aberration control. METHODS: A wavefront analyser (Zywave, Bausch & Lomb) was used to measure the aberrations in each subject's right eye uncorrected and with the different contact lenses. The first study evaluated residual spherical aberration with a standard lens (Focus Dailies Disposable, Ciba Vision) and with an aberration controlled contact lens (ACCL) (Definition AC, Optical Connection Inc.). The second study evaluated the residual spherical aberrations with a monthly disposable silicone hydrogel lens with aberration reduction (PureVision, Bausch & Lomb). RESULTS: Uncorrected spherical aberration was positive for all pupil sizes in both studies. In the first study, residual spherical aberration was close to zero with the standard lens for all pupil sizes whereas the ACCL over-corrected spherical aberration. The results of the second study showed that the monthly disposable lens also over-corrected the aberration making it negative. The changes in aberration were statistically significant (p<0.05) with all lenses. CONCLUSION: Since the amount of aberration varies individually we suggest that aberrations should be measured with lenses on the eye if the aim is to change spherical aberration in a certain direction.     

The association of comfort and vision in soft toric contact lens wear

PurposeThis work set out to investigate if there was an association between subjective comfort and both subjective and measured vision during the use of contemporary daily disposable soft toric contact lenses.MethodsThirty-eight habitual soft contact lens wearers wore each of three daily disposable toric lenses for one week in a prospective, crossover, randomised, single-masked study. The following clinical measures were recorded at dispensing and follow-up visits: biomicroscopy scores, lens fitting (including rotation and rotational stability), high and low contrast visual acuity, subjective vision quality and subjective ocular surface comfort. Subjective scores were collected using 0–10 numerical grading scales. Comfort scores were analysed using a linear regression model with age, sex, visit, phase of crossover (‘phase’), lens type, lens rotation, lens rotational stability, visual acuity, cylinder power and subjective vision quality as factors of interest and then refined using backward stepwise regression.ResultsThirty six participants (31.1 ± 13.5 years) completed the study. Comfort scores were found to be associated with subjective vision quality (F = 127.0 ; p < 0.0001), phase (F = 7.2; p = 0.001) and lens type (F = 4.9; p = 0.009). Greater comfort scores were observed with greater subjective vision quality scores. Visual acuity was not statistically significant in the model.ConclusionThis work suggests that symptoms of ocular discomfort may be more intense if there is also perceived visual compromise in daily disposable soft toric lenses. There was a stronger positive correlation between comfort and subjective vision quality compared with comfort and measured visual acuity.     

Evaluation of daily disposable senofilcon A contact lenses in a symptomatic population

PurposeTo evaluate the comfort performance of ACUVUE OASYS® 1-Day with HydraLuxe? Technology among symptomatic contact lens wearers by using Contact Lens User Experience (CLUE) comfort scores and Contact Lens Dry Eye Questionnaire 8 (CLDEQ-8) discomfort and dryness scores.MethodsThree clinical trials evaluated comfort and dryness when refitting symptomatic contact lens wearers to ACUVUE OASYS® 1-Day with HydraLuxe? lenses. This analysis combined the CLUE comfort and CLDEQ-8 scores obtained at baseline and 2-week follow-up and compared average scores between visits. Subjects were grouped by habitual lens modality (daily disposable or daily wear reusable) and habitual lens material (silicone hydrogel or hydrogel). The analysis included data from 107 subjects.ResultsSignificant increases in mean CLUE comfort scores between baseline and 2–week follow-up occurred in all subject groups across habitual lens modality and material, indicating an improvement in overall comfort. CLUE comfort score improved clinically (≥5-point increase) among 75.7% of subjects (81/107). Similarly, significant decrease in mean CLDEQ-8 scores between baseline and 2-week follow-up occurred in all subject groups, indicating a decrease in the prevalence of dryness and discomfort symptoms. CLDEQ-8 score improved clinically (≥3-point reduction) among 82.2% of subjects (88/107). A majority of subjects (57.0%) became asymptomatic (CLDEQ-8 score ≤ 11 points) after 2 weeks of bilateral wear.ConclusionRefitting symptomatic contact lens patients to ACUVUE OASYS® 1-Day with HydraLuxe? can improve overall comfort and reduce symptoms of dryness and discomfort, irrespective of the previous lens modality or habitual lens material.     

The impact of contact lens wear on ocular surface mucins using a novel clinical fluorescence imaging system

PurposeFluorescein-labelled wheat germ agglutinin (F-WGA) acts as a marker for ocular surface mucins. This clinical study sought to investigate whether the degree of F-WGA fluorescence observed at the ocular surface differed between symptomatic contact lens wearers, asymptomatic contact lens wearers and non-contact lens wearers, using a novel imaging system.MethodsTwenty-five participants (10 symptomatic contact lens wearers, 10 asymptomatic contact lens wearers and 5 non-contact lens wearers) attended a single study visit. Photographs of the cornea, bulbar and tarsal conjunctiva were captured following application of F-WGA solution.ResultsThe imaging system captured high-resolution images of F-WGA fluorescence at the ocular surface. The degree of fluorescence differed between the ocular surface regions (p < 0.001). A significant difference in fluorescence was observed between participant groups for the cornea (p = 0.01), with both the symptomatic and asymptomatic contact lens wearers showing lower fluorescence than the non-lens wearers. F-WGA associated fluorescence appeared diminished in the lid wiper region of the symptomatic lens wearers, compared to the asymptomatic group (p = 0.025).ConclusionThe use of F-WGA as a clinical marker for ocular surface mucins allows an improved understanding of their distribution across the ocular surface. Contact lens wear appears to negatively impact mucin density across the ocular surface, with the most marked effect on the cornea. F-WGA fluorescence appeared diminished in the lid wiper region for the symptomatic contact lens wearing group, indicating that mechanical interaction in this region may play a role in the aetiology of contact lens discomfort. Given the ability of F-WGA to disclose mucin distribution across the ocular surface it is likely to be a key clinical tool in furthering our understanding of (i) the aetiology of contact lens related discomfort, (ii) contact lens designs/materials to minimise interaction with the ocular surface and (iii) dry eye disease and other ocular surface diseases.     

Temporal considerations in contact lens discomfort

PurposeTo determine the relative contributions to perceived discomfort during contact lens wear of contact time with the lens and the time of day at which wear begins, using a wearing framework similar to that of regular users.MethodsTwenty-three participants reported ocular discomfort using a 1–100 visual analogue rating scale, when prompted by email, during one day without contact lenses and on three other days while wearing soft contact lenses for twelve hours. Contact lens wear began at a different time on each day. The effect of start time on the change in discomfort during the wearing period was evaluated.ResultsThe average (± 95 % CI) change in discomfort over 12 h without contact lenses was -0.3 ± 3.5. The corresponding values during contact lens wear were 23.5 ± 14.6 when starting wear before 8am, 16.8 ± 11.0 when starting between 8am & 10am and 22.7 ± 8.4 when starting after 10am. While the increased discomfort was significant irrespective of start time (p < 0.01), there were no statistically significant differences between start times (p = 0.98).ConclusionDiscomfort during contact lens wear is associated with the length of time lenses are on-eye but not with the time of day when lenses are placed on-eye. This relationship is variable in the population and does not, of itself, explain why contact lenses become uncomfortable during wear. Active monitoring of participant compliance should be a consideration in all studies involving time critical responses.     

Monitoring ocular discomfort using a wrist-mounted electronic logger

PurposeTo investigate ocular discomfort during contact lens wear using a wrist-mounted electronic ‘lens awareness logger’ (LAL).MethodsThirty symptomatic contact lens wearers wore study contact lenses for three days. On the first two days, two lens types which are known to differ in end-of-day comfort (lens A: senofilcon A and lens B: balafilcon A), were worn as a matching pair (randomised order). On day three, a pair of lens B was worn. On each day, the participant used a LAL. On day one and two, the participant pressed a button on the LAL whenever they became aware of their lenses due to discomfort. On day three, the participant used a multiple click protocol (1 = mild awareness to 3 = severe awareness) to report discomfort.ResultsLAL events were similar on days one and two (17.3 vs. 15.8 events per day). There were significantly more LAL events for lens B (21.6 events per day) in comparison with lens A (11.6 events per day) (p = 0.006). The LAL event profile highlighted peaks in awareness following lens application and towards the end of the wearing cycle. Comparison of the LAL event profile for the two lens types showed significant differences in lens awareness, particularly in the first half of the wearing cycle. LAL events on day 3, showed a uniform distribution of single and double clicks through the day, but a marked peak in triple clicks in the last two hours of lens wear.ConclusionThe LAL was able to differentiate between the study lenses and demonstrated differences in their LAL event profiles. Lens awareness associated with discomfort appeared to increase not only in frequency, but also in intensity towards the end of the wearing cycle. The ability of the LAL to track lens awareness suggests it is likely to be a useful tool in furthering understanding of ocular discomfort.     

The impact of short-term fenestrated scleral lens wear on intraocular pressure

PurposeTo examine the influence of short-term fenestrated scleral lens wear on intraocular pressure (IOP) in healthy eyes.MethodsIOP was measured before, during, and after a brief period (1–2 min) of fenestrated, scleral lens wear, using a rebound tonometer, in fifty, young healthy adults (mean age 23 ± 4 years) with normal corneas.ResultsImmediately following lens insertion, 48 of the 50 (96 %) of participants displayed an increase in IOP (mean ± SD increase in these participants of 3.8 ± 2.0 mmHg). Immediately following lens removal, 50 % of participants displayed a reduction in IOP, equal to or lower than, the pre-insertion IOP (-1.0 ± 0.8 mmHg lower than baseline). The remaining 50 % of participants displayed an IOP slightly greater than the pre-insertion IOP (1.6 ± 1.0 mmHg greater) after lens removal.ConclusionsShort-term fenestrated scleral lens wear resulted in a small, but statistically significant, increase in IOP in 96 % of young healthy participants (< 4 mmHg on average), which decreased to a level similar to pre-lens insertion IOP levels immediately following lens removal. Further research is required to determine if this measured change in IOP during scleral lens wear is artefactual, or an elevation in the true IOP.