Purpose: To analyse, describe and test diverse corneal and anterior segment parameters in normal and keratoconic eyes to better understand the geometry of the keratoconic cornea.
Method: 44 eyes from 44 keratoconic patients and 44 eyes from 44 healthy patients were included in the study. The Pentacam System was used for the analysis of the anterior segment parameters. New ad-hoc parameters were defined by measuring the distances on the Scheimpflug image at the horizontal diameter, with chamber depth now comprising of two distinctive distances: corneal sagittal depth and the distance from the endpoint of this segment to the anterior surface of the lens (DL).
Results: Statistically significant differences (p<0.05) between normal and keratoconic eyes were found in all of the analysed corneal parameters. Anterior chamber depth presented statistical differences between normal and keratoconic eyes (3.06 ± 0.43 mm versus 3.34 ± 0.45 mm, respectively; p = 0.004). This difference was found to originate in an increase of the DL distance (0.40 ± 0.33 mm in normal eyes against 0.61 ± 0.45 mm in keratoconic eyes; p = 0.014), rather than in the changes in corneal sagittal depth.
Conclusion: These findings indicate that keratoconus results in central and peripheral corneal manifestations, as well as changes in the shape of the scleral limbus. The DL parameter was useful in describing the forward elongation and advance of the scleral tissue in keratoconic eyes. This finding may help in the monitoring of disease progression and contact lens design and fitting.
Purpose: To evaluate the usefulness of an infrared open-field autorefractor as a predictor of the refractive error when fitting multifocal contact lenses (MCL).; Methods: Objective and subjective measurements of the non-cycloplegic distance refractive error were compared in patients wearing MCL. We used the Grand Seiko WAM-5500 autorefractor for the objective measurements. Three commercially available MCL were tested. Twenty-one eyes of sixteen healthy adults were included in the study. Over-refraction was evaluated in terms of spherical equivalent (SE) and astigmatic vectors (J0 and J45). The mean difference + SD of each parameter was calculated. The Kolmogorov-Smirnov test was used to verify the normal distribution. Pearson's correlation, Bland and Altman plot and paired sample t test were used to compare the results obtained with both methods.; Results: The mean difference between objective and subjective results of the SE over-refraction was 0.13 +/- 0.42D; for astigmatic vectors Jo and J45 were 0.03 + 0.32D and 0.00 + 0.17D, respectively. The Kolmogorov-Smirnov test showed a normal distribution for all parameters. The highest Pearson's correlation coefficients were obtained for the SE with values of 0.98 without MCL and 0.97 with MCL. The lowest were obtained for J45 with values of 0.65 without MCL and 0.75 with MCL. Significant correlations were obtained for each parameter. The paired sample t test failed to show significant differences in analyzed parameters except fork without MCL.; Conclusions: The Grand Seiko WAM-5500 can be used as a screening method of over-refraction in the clinical fitting of MCL. (C) 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Purpose: It was the main purpose of this study to investigate the influence of the moistening solution on TBUT measurements in an asymptomatic population.; Methods: An online survey was employed to determine the compliance of Spanish eye care practitioners with the recommended normalized procedure to administer TBUT. For the purpose of examining the clinical relevance of discrepancies from the recommended procedure, a randomized, double-masked, bilateral study was designed in which a micropipette was used to moisten fluorescein strips with a controlled volume of six different solutions, commonly available in the contact lens office, and TBUT was measured in 58 non-dry eye (OSDI < 15) subjects (age from 19 to 32 years).; Results: Results from the online survey revealed that 64% of Spanish practitioners frequently use (or have used) different solutions to moisten fluorescein strips during TBUT assessment. Statistically significant differences in TBUT values were found between the various solutions as a whole (chi(2) = 198.384, p < 0.001), as well as between all solutions when explored pair-wise (all p < 0.001), except for the two saline solutions.; Conclusions: The present findings support the relevance of selecting the appropriate solution when conducting TBUT for the evaluation of the tear film. Deviations from the recommended procedure may result in misdiagnosis of dry eye and unnecessary patient referral. (C) 2015 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
Pauné, J.; Queiros, A.; Quevedo, L.; Neves, H.; Lopes, D.; González, J. Contact lens and anterior eye Vol. 37, num. 6, p. 455-460 DOI: 10.1016/j.clae.2014.08.001 Data de publicació: 2014-12-01 Article en revista
Purpose: To evaluate the performance of two experimental contact lenses (CL) designed to induce relative peripheral myopic defocus in myopic eyes.; Methods: Ten right eyes of 10 subjects were fitted with three different CL: a soft experimental lens (Exp-SCL), a rigid gas permeable experimental lens (ExpRGP) and a standard RGP lens made of the same material (StdRGP). Central and peripheral refraction was measured using a Grand Seiko open-field autorefractometer across the central 60 degrees of the horizontal visual field. Ocular aberrations were measured with a Hartman-Shack aberrometer, and monocular contrast sensitivity function (CSF) was measured with a VCTS6500 without and with the three contact lenses.; Results: Both experimental lenses were able to increase significantly the relative peripheral myopic defocus up to -0.50 D in the nasal field and -1.00 D in the temporal field (p < 0.05). The ExpRGP induced a significantly higher myopic defocus in the temporal field compared to the ExpSCL. ExpSCL induced significantly lower levels of Spherical-like HOA than ExpRGP for the 5 mm pupil size (p < 0.05). Both experimental lenses kept CSF within normal limits without any statistically significant change from baseline (p > 0.05).; Conclusions: RGP lens design seems to be more effective to induce a significant myopic change in the relative peripheral refractive error. Both lenses preserve a good visual performance. The worsened optical quality observed in ExpRGP was due to an increased coma-like and spherical-like HOA. However, no impact on the visual quality as measured by CSF was observed. (C) 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
De Juan, V.; Aldaba, M.; Martin, R.; Vilaseca, M.; Herrera, J.; Pujol, J. Contact lens and anterior eye Vol. 37, num. 4, p. 278-284 DOI: 10.1016/j.clae.2014.02.003 Data de publicació: 2014-08-01 Article en revista
Purpose: To evaluate the impact of contact lens (CL)-induced corneal swelling on the optical quality of the eye by means of the double-pass technique.; Methods: Measurements of 6 healthy subjects were obtained in 5 visits over 1 week, at baseline and after sleeping with 4 different CLs of +0.50 D, +2.00 D, +5.00 D and +8.00 D (Acuvue2), randomly fitted on 4 different days. The control eye wore no CL Corneal pachymetry and optical quality of the eye (OQAS, Visiometrics) were measured once at baseline and at three interval times in the follow-up.visits: immediately after CL removal, and 1 and 2 h after CL removal. Optical quality was evaluated by means of the Strehl ratio and OQAS values at 100%, 20% and 9% contrasts. Intraocular scattering was evaluated with the objective scatter index (OSI).; Results: Mean overnight swelling was 5.98 4.29% in CL-eyes versus 0.30 0.78% in control eyes (p <0.01). Corneal swelling was maximal immediately after CL removal and decreased with time (p <0.01). A significant worsening in all optical quality parameters and a significant increase of the OSI were found in eyes with corneal swelling (p < 0.05). Two hours after CL removal there were no statistically significant differences (p >0.05) between CL-eyes and control eyes in any of the measured parameters.; Conclusions: Corneal swelling has a significant impact on the optical quality of the eye and on intraocular scattering as assessed with the double-pass technique. (C) 2014 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.
A study was designed to evaluate the efficacy of three different strategies aiming at increasing spontaneous eyeblink rate (SEBR) during computer use.
A total of 12 subjects (5 female) with a mean age of 28.7 years were instructed to read a text presented on a computer display terminal during 15 min. Four reading sessions (reference and three “blinking events” [BE]) were programmed in which SEBR was digitally recorded. “Blinking events” were based on either a slight distortion of the text characters or on the presentation of a white screen instead of the text, with or without accompanying blinking instructions. All BE had a duration of 20 ms and occurred every 15 s. Participants graded the intrusiveness of each BE configuration, and the number of lines participants read in each session was recorded.
Data from 11 subjects was analysed. A statistically significant difference in SEBR was encountered between the experimental configuration consisting on a white screen plus blinking instructions (7.8 blinks/min) and both reference (5.2 blinks/min; p = 0.049) and white screen without blinking instructions (4.8 blinks/min; p = 0.038). All three BE had superior levels of intrusiveness than reference conditions, although the performance of participants (line count) was not compromised.
The joint contribution of white screen and blinking instructions has been shown to result in a short term improvement in blinking rate in the present sample of non-dry eye computer users. Further work is necessary to improve the acceptance of any BE aiming at influencing SEBR.