Optical quality comparison among different Boston contact lens materials

Impact of soft and rigid gas-permeable contact lenses on visual performance in mesopic conditions

CONTEXT

Evaluation of visual quality in soft and rigid gas-permeable contact lens wearers, with an emphasis on twilight vision.

PURPOSE

To assess the visual acuity and visual performance at dusk before and after soft and rigid gas-permeable contact lens (CL) correction in healthy subjects.

SETTINGS AND DESIGN

This prospective study was conducted in a tertiary eye-care center.

METHODS

Sixty eyes corrected with soft contact lenses (SCLs) and 30 eyes with rigid gas-permeable contact lenses (RGPCLs) were enrolled in this study. Patients underwent corrected distance visual acuity with spectacles (CDVAs), corrected distance visual acuity with contact lenses (CDVAcl), and twilight vision (TV) testing (Vista Vision Far-Pola, DMD MedTech charts). Parameters were evaluated before and after the CL fitting and repeated 3 months after the baseline visit.

STATISTICAL ANALYSIS USED

MedCalc for Windows, version 11.4 (MedCalc Software, Ostend, Belgium).

RESULTS

Rigid gas-permeable CL wear showed significant improvement in CDVAcl compared to wearing spectacles on both visits ( P = 0.0039 and P = 0.0003, respectively). TV with CLs was significantly better in both groups compared to the TV with spectacles at the baseline visit ( P = 0.0011 in SCL group; P = 0.0001 in RGPCL group), and at the follow-up visit, this significance was proven for the RGPCL group ( P = 0.001). Also, spectacle TV showed a significant improvement on the follow-up visit ( P = 0.0022 in SCL group; P = 0.0269 in RGPCL group).

CONCLUSION

Contact lens wear improves visual performance compared to spectacles. TV results showed superiority of CLs compared to the spectacles, without a statistical difference regarding the CL type.

CLEAR - Scleral lenses

Scleral lenses were the first type of contact lens, developed in the late nineteenth century to restore vision and protect the ocular surface. With the advent of rigid corneal lenses in the middle of the twentieth century and soft lenses in the 1970's, the use of scleral lenses diminished; in recent times there has been a resurgence in their use driven by advances in manufacturing and ocular imaging technology. Scleral lenses are often the only viable form of contact lens wear across a range of clinical indications and can potentially delay the need for corneal surgery. This report provides a brief historical review of scleral lenses and a detailed account of contemporary scleral lens practice including common indications and recommended terminology. Recent research on ocular surface shape is presented, in addition to a comprehensive account of modern scleral lens fitting and on-eye evaluation. A range of optical and physiological challenges associated with scleral lenses are presented, including options for the clinical management of a range of ocular conditions. Future applications which take advantage of the stability of scleral lenses are also discussed. In summary, this report presents evidence-based recommendations to optimise patient outcomes in modern scleral lens practice.

Contact Lens Technology: From Fundamentals to Applications

Contact lenses are ocular prosthetic devices used by over 150 million people worldwide. Primary applications of contact lenses include vision correction, therapeutics, and cosmetics. Contact lens materials have significantly evolved over time to minimize adverse effects associated with contact lens wearing, to maintain a regular corneal metabolism, and to preserve tear film stability. This article encompasses contact lens technology, including materials, chemical and physical properties, manufacturing processes, microbial contamination, and ocular complications. The function and the composition of the tear fluid are discussed to assess its potential as a diagnostic media. The regulatory standards of contact lens devices with regard to biocompatibility and contact lens market are presented. Future prospects in contact lens technology are evaluated, with particular interest given to theranostic applications for in situ continuous monitoring the ocular physiology.

Fabrication of Hydrophilic Surface on Rigid Gas Permeable Contact Lenses to Enhance the Wettability Using Ultraviolet Laser System

The widely used rigid gas permeable (RGP) contact lenses provide higher oxygen permeability and tear exchange rate than do soft contact lenses. However, their wettability warrants improvement to enhance the wearing comfort. This study used UV laser (wavelength = 355 nm) to modify the surface properties of RGP contact lenses with materials of Boston XO^® (Bausch & Lomb Incorporated). Briefly, the mesh pattern was fabricated on the RGP contact lens surface by using the laser and smoothed by using oxygen plasma; the enhanced hydrophilic efficiency was analyzed using contact angle measurement. The experiment results indicated that the contact angle of the lens material decreased by approximately 10°–20° when the pitch of mesh pattern was <50 μm under a 500-mm/s scanning speed. The oxygen plasma enhanced surface wettability with a decreased contact angle (40°). The hydrophilic characteristic of the UV laser and oxygen plasma–treated surface was twice that of oxygen plasma–treated and untreated surfaces. In the future, RGP contact lens edges could be treated with UV laser and oxygen plasma to enhance the tear wettability and wearing comfort.

Repeatability of in-vitro optical quality measurements of intraocular lenses with a deflectometry technique effect of the toricity

AIM

To evaluate the repeatability of an optical device for measuring the Zernike coefficients of toric intraocular lenses (IOLs) and assess whether its toricity has any impact in its repeatability.

METHODS

An experienced technician used the NIMO TR1504 to measure the Zernike coefficients 30 times for an aperture of 4.50 mm for all lenses included. The IOLs included were divided into two group: toric and non-toric ones. The cylindrical powers of the toric lenses included in the present study were 1.00, 1.50, 2.25, 3.00 and 3.75 D. Finally, the repeatability of the NIMO TR1504 was described in terms of within subject standard deviation (Sw) and repeatability limit.

RESULTS

The Sw was smaller than 0.011 µm for both lens groups and all Zernike coefficients, and the difference between both groups was smaller than 0.004 µm for all Zernike coefficients. Regarding the repeatability limit, this value was smaller than 0.025 µm for the toric lens group, and smaller than 0.031 µm for the non-toric lens one for all Zernike coefficients. Furthermore, the maximum difference between both lens groups was 0.010 µm.

CONCLUSION

The repeatability of the NIMO TR1504 to measure the optical quality is high and independent of the lens toricity. These results reflect that this system is robust and could be used to measure the in-vitro optical quality of either toric or non-toric IOLs.

Power Profiles and In Vitro Optical Quality of Scleral Contact Lenses: Effect of the Aperture and Power

OBJECTIVE

To assess the power profile and in vitro optical quality of scleral contact lenses with different powers as a function of the optical aperture.

METHODS

The mini and semiscleral contact lenses (Procornea) were measured for five powers per design. The NIMO TR-1504 (Lambda-X) was used to assess the power profile and Zernike coefficients of each contact lens. Ten measurements per lens were taken at 3- and 6-mm apertures. Furthermore, the optical quality of each lens was described in Zernike coefficients, modulation transfer function, and point spread function (PSF). A convolution of each lens PSF with an eye-chart image was also computed.

RESULTS

The optical power fluctuated less than 0.5 diopters (D) along the optical zone of each lens. However, the optical power obtained for some lenses did not match with its corresponding nominal one, the maximum difference being 0.5 D. In optical quality, small differences were obtained among all lenses within the same design. Although significant differences were obtained among lenses (P<0.05), these showed small impact in the image quality of each convolution.

CONCLUSIONS

Insignificant power fluctuations were obtained along the optical zone measured for each scleral lens. Additionally, the optical quality of both lenses has showed to be independent of the lens power within the same aperture.