Differential effect of maximal incremental treadmill exercise on tear secretion and tear film stability in athletes and non-athletes.

The study investigated the differential response to a single bout of maximal incremental treadmill exercise between athletes and non-athletes without dry eyes regarding tear secretion, tear film stability, visual acuity (VA), and stereoacuity. Additionally, the study examined the effect of gender and the duration of exercise on exercise-induced changes. Study participants included young university students aged 18-25 years who were athletes (male/female: 13/13) or non-athletes (male/female: 17/9). Participants underwent an aerobic exercise session using a treadmill and following the laid down Bruce treadmill test protocol till exhaustion. Measurements were taken in the order of distance VA, stereopsis, non-invasive tear break-up time (TBUT), and phenol red thread test, at baseline and after the exercise regimen. Within- and between-subject analyses using multiple t-tests with correction for multiple comparisons were performed to determine differences before and after exercise in athletes and non-athletes. Subsequently, ANCOVA was used to assess the influence of gender and the duration of exercise. The mean age (SD) of the athletes and the non-athletes was 22.4 ± 2.1 years and 21.8 ± 2.1 years, respectively (p = 0.357). Before exercise, the athletes had higher TBUT than non-athletes (14.6 ± 2.9 s vs. 11.9 ± 3.8 s; p = 0.021), but no difference was observed in any other ocular measurements. After exercise, the athletes showed significant improvement in tear secretion with the basal tear secretion increasing from 22.3 ± 2.5 mm to 25.8 ± 1.7 mm (p < 0.001). The non-athletes on the other hand had a borderline increase in tear secretion from 21.42 ± 2.85 mm to 23.73 ± 2.68 mm (p = 0.08). Also, the TBUT was much improved in the athletes after exercise compared to the non-athletes (17.7 ± 2.7 s vs. 14.8 ± 2.9 s, p = 0.004). Additionally, exercise improved the VA indifferently between the groups, while stereoacuity was unchanged after exercise in either group. Gender had no influence on the differences in the tear function measures between athletes and non-athletes after exercise. The duration of exercise, however, showed a borderline effect on the tear film stability (p = 0.068) after exercise. Our findings support the differential effect of maximal incremental treadmill exercise on tear secretion and tear film stability between athletes and non-athletes. Thus, increased physical fitness and the duration of exercise might be crucial in the improvement of tear function through aerobic exercise.

The Impact of Scleral Contact Lens Vault on Visual Acuity and Comfort.

PURPOSE: To assess how varying degrees of corneal clearance of scleral contact lenses (ScCL) impact visual acuity (VA) and comfort in patients with corneal ectasia. METHOD: Three ScCL were fitted to 20 subjects with previous diagnosis of either keratoconus (n=18) or pellucid marginal degeneration (n=2). Fitting of ScCL was based on corneal sagittal height (CSH) measured with Visante OCT at a 15-mm chord on the horizontal meridian. To select the ScCL from the diagnostic lens set, values of 325, 375, and 425 µm were randomly added in sequence to CSH. Subjects wore ScCL for 1 hr. Central corneal clearance (CCC) and topographic corneal clearance (TCC) along the vertical meridian were assessed using an ultralong optical coherence tomographer. High-contrast VA (HCVA) and low-contrast VA (LCVA) were measured using a logarithm of the minimum angle of resolution VA chart, and comfort ratings were obtained with a standard comfort scale (0-100). RESULTS: Mean CSH in the horizontal meridian was 3.78±0.53 (range: 3.33-4.17) mm at a 15-mm chord. Mean CCC was 190±100 µm (TCC: 160±94 µm at +3 mm and 180±94 µm at -3 mm), 360±120 µm (TCC: 260±100 µm at +3 mm and 330±110 µm at -3 mm), and 450±170 µm (TCC: 320±120 µm at +3 mm and 400±120 µm at -3 mm) for each lens (P=0.001). Mean HCVA for lenses 1, 2, and 3 were 0.05±0.12, 0.07±0.11, and 0.11±0.08 respectively, which were significantly different (P=0.02). Tukey post hoc analysis showed that this difference was only significant between lenses 1 and 3 (P=0.01). Similar findings were found for LCVA. Comfort ratings for lenses 1, 2, and 3 were 74.9±9.2, 79.7±11.6, and 78.6±10.8, respectively (P=0.24). CONCLUSION: The CSH is an effective method of determining the appropriate lens/cornea relationship. Lens 2 (+375 µm) gave the best combination of acuity and comfort ratings. Evaluation of the fluorescein pattern must be balanced with VA and comfort ratings for successful fitting in a clinical setting.

Effect of Time on Scleral Lens Settling and Change in Corneal Clearance.

SIGNIFICANCE: With the increase in the use of scleral contact lenses among practitioners, questions regarding lens settling are gradually gaining attention. This is because current studies support the notion that scleral lenses settle back over time. More research is needed to understand the exact cause and the factors that underpin such phenomenon. PURPOSE: The present study aims to assess the effect of time on topographic corneal clearance of three scleral contact lenses of varying sagittal depths. METHODS: Three scleral contact lenses were fitted to 20 subjects with previous diagnosis of keratoconus (n = 18) or pellucid marginal degeneration (n = 2). The fit was based on corneal sagittal height measured with the Visante optical coherence tomographer (OCT) at 15 mm along the horizontal meridian. To select an appropriate lens from the diagnostic lens set, values of 325 µm (lens 1), 375 µm (lens 2), and 425 µm (lens 3) were randomly added in sequence to the corneal sagittal height. Subjects wore each lens for 1 hour. Corneal clearance was measured at 10-minute intervals for 1 hour using a custom ultra-long OCT. To assess change in clearance, central point and two mid-peripheral points (+3 mm and -3 mm) along an 8-mm chord were measured by taking differences at each time point up to 1 hour. Measurements were repeated for the two other lenses. RESULTS: Mean central corneal clearance loss for all three lenses was 33.83 ± 48.40 µm. This was 26 ± 27 µm (13 ± 14 µm, +3 mm; 34 ± 37 µm, -3 mm), lens 1; 35 ± 59 µm (38 ± 61 µm, +3 mm; 52 ± 69 µm, -3 mm), lens 2; and 41 ± 54 µm (33 ± 26 µm, +3 mm; 52 ± 48 µm, -3 mm), lens 3, respectively. There was no significant difference (P = 0.06) at central and other locations for lens 1 (location and over time). There were significant differences for both lenses 2 and 3 (P < .001, P = .01, respectively) for all three locations and over time. CONCLUSIONS: There is a likelihood of clearance loss after 1 hour of lens wear. This varies between subjects, initial lens-fit relationship, and over time.

Repeatability of topographic corneal thickness in keratoconus comparing Visante™ OCT and Oculus Pentacam HR® topographer.

PURPOSE: To assess the repeatability and reproducibility of Visante™ OCT and Oculus Pentacam HR® in measuring central (CCT) and topographic corneal thickness (TCT) along the principle meridians in keratoconus (KC) corneae. METHOD: Twenty participants diagnosed with KC were recruited. There were two study visits. On the first study visit, two repeated corneal thickness measurements were obtained with each instrument. Measurements were repeated at least 48hrs later in the same order. TCT were recorded in the 90, 180, 45 and 135 meridians at 1mm intervals across 8mm chord. RESULTS: Mean CCT for Visante™ OCT was 484.97±43.14µm (range: 484.84-486.09) and Oculus Pentacam HR® was 478.86±45.31µm (range: 477.20-480.53). No significant difference in TCT between the two visits (p=0.54) and measurements (p=0.63) for Visante™ OCT. For Oculus Pentacam HR®, no significant difference was found for each visit (p=0.18) but differences existed in the measurements outside of the central region (p=0.001). Tukey post-hoc analysis shows the differences (p˂0.05) were found in the +1 and +4 (supero-temporal) locations in the 135 meridian. Significant differences were found comparing the two instruments, (p<0.05). Bland Altman plots were used to demonstrate the differences between the two instruments and indicate their limits of agreement. CONCLUSION: Both instruments gave repeatable measurements as no significant differences were found in most locations in all meridians. Comparing the two instruments, they were not reproducible in all locations.

Knowledge, usage and barriers associated with contact lens wear in Ghana.

BACKGROUND: Despite findings that contact lens wear for vision correction provides better quality of life than spectacles, contact lens use in developing countries is low. This study evaluated knowledge, usage and barriers associated with contact lens wear among spectacle wearers in Cape Coast, Ghana. METHOD: A cross-sectional survey using a structured questionnaire was conducted on an adult population of spectacle wearers to assess their knowledge of contact lens wear for vision correction. The participants were proportionately sampled from three eye clinics in the Cape Coast Metropolis, Ghana. Questionnaires were either self-administered or completed with the help of a research assistant. RESULTS: Of the 422 participants, only 147 (34.8%) knew of contact lens wear for vision correction. The proportion of spectacle wearers reporting history of contact lens wear was 14 (3.3%). Barriers to contact lens wear reported were satisfaction with vision through spectacles 102 (25.0%), lack of adequate information 111 (27.2%), fear of side effects 94 (23.0%) and cost 78 (19.1%). The younger adults and those with higher number of changes of spectacles were more likely to know of contact lenses. CONCLUSION: Knowledge and usage of contact lenses among spectacle wearers was low. Contact lens education and demonstration of visual performance through fitting of trial contact lenses on potential candidates may help overcome barriers to contact lens wear.

Impact of Cosmetics on the Surface Properties of Silicone Hydrogel Contact Lenses.

PURPOSE: This study evaluated the impact of various cosmetics on the surface properties of silicone hydrogel (SiHy) contact lens materials. METHODS: In this in vitro experiment, 7 SiHy contact lens materials were coated with 1 of 9 cosmetics, including common hand creams (3), eye makeup removers (3), and mascaras (3). Dark-field microscopy images were taken to determine pixel brightness (PB) after cosmetic exposure, which describes the visible surface deposition (n=6 for each lens type), with a higher PB indicating increased deposition. The sessile drop technique was used to determine the advancing contact angle (CA). Measurements were repeated for both methods after a single peroxide-based cleaning cycle. RESULTS: Pixel brightness was significantly higher for mascara-coated lenses compared with the other cosmetic products (P<0.01). The peroxide-based lens care solution removed most deposits from the nonwaterproof mascara for 4 lens types, whereas deposits remained relatively unchanged for 1 waterproof mascara (P>0.05). Hand creams and makeup remover had minimal impact on PB. Changes in CA measurements after cosmetic application were highly lens dependent. Hand creams caused primarily a decrease in CA for 5 of the 7 lens types, whereas 1 of the waterproof mascaras caused a significant increase of 30 to 50° for 3 lens types. CONCLUSION: Some mascara-lens combinations resulted in increased CA and PB, which could have an impact on in vivo lens performance. Nonwaterproof mascara was mostly removed after a cleaning cycle. Further research is needed to understand the clinical implications for SiHy lens wearers using cosmetics.