Preoperative Assessment of Corneal and Refractive Stability in Soft Contact Lens Wearing Photorefractive Candidates

Impact of removing soft contact lenses 1 day versus 1 month before surgery on the outcomes of microkeratome laser in situ keratomileusis

PURPOSE

To compare the outcomes, safety, efficacy, and predictability of microkeratome laser in situ keratomileusis (LASIK) 24 h and one month or more after removing soft contact lenses.

SETTING

ULTRALASIK Eye Center, Dubai, United Arab Emirates.

METHODS

The patients were divided based on the time of discontinuation of the soft contact lenses before LASIK (Group 1 at 24 h and Group 2 at one month or longer), and the two groups were well matched. Schirmer's testing, tear break-up time, corrected distance visual acuity, uncorrected distance visual acuity, manifest refraction spherical equivalent, and infection rate were evaluated preoperatively and at one week, one month, and six months after treatment.

RESULTS

Group 1 (G1) comprised 1025 eyes, and group 2 (G2) had 1052 eyes. The groups were comparable preoperatively. The overall-mentioned outcomes were comparable between groups with uncorrected distance visual acuity of - 0.084 ± 0.12 logMAR in G1 and - 0.078 ± 0.17 logMAR in the G2 at 6 months (P = 0.322). Tear break-up time as well as Schirmer's testing results was also comparable with no evidence of increased risk of dry eyes or non-inflammatory complications in any of the groups on follow-up visits at 1 week (P = 0.421), 1 month (P = 0.101), and 6 months (P = 0.399) postoperatively. Finally, no infectious complications were recorded in either of the groups.

CONCLUSION

With the absence of corneal warpage, no statistical or clinical difference in microkeratome LASIK outcomes and safety was spotted between the groups despite the difference in SCL discontinuation time before the procedure.

Managing Post-Keratoplasty Astigmatism: High-Tech vs. Low-Tech Imaging Techniques for Guiding Suture Manipulation

Astigmatism is a visually significant condition that can develop after keratoplasty. The management of post-keratoplasty astigmatism can be performed both when transplant sutures are in place and when they have been removed. Fundamental for astigmatism management is its identification and characterization in terms of type, amount, and direction. Commonly, post-keratoplasty astigmatism is evaluated through corneal tomography or topo-aberrometry; however, many other techniques can be used in case these instruments are not readily available. Here, we describe several low-tech and high-tech techniques used for post-keratoplasty astigmatism detection in order to quickly understand if it contributes to low vision quality and to determine its characteristics. The management of post-keratoplasty astigmatism through suture manipulation is also described.

Assessment of the reliability (repeatability) of corneal thickness measurements in soft contact lens wearers using a non-contact specular microscope

PURPOSE

To assess variability across 3 measures of central corneal thickness (CCT) obtained with a non-contact specular microscope and taken over a few minutes from habitual soft contact lens wearers.

METHODS

One eye from 200 healthy adults (with an average age of 21 y, half of whom had a 3.5 ± 2.1 year history of successful daily wear of soft contact lenses while the control group had nominally normal eyes) were assessed using the auto-focus Topcon 2000P instrument to obtain an image of the endothelium and CCT.

RESULTS

The individual CCT values encountered in the 200 subjects ranged from 0.449 mm to 0.591 mm, with the average of 3 measures ranging from 0.459 to 0.591 mm in the control group and between 0.449 and 0.585 mm for the SCL wearers. The group mean CCT values were the same for both groups (at 0.524 mm), but the group mean SD value was marginally higher (at 0.028 mm) for the SCL group as compared to controls (SD = 0.026 mm). The normalized intra-subject variability (as the group-mean coefficient of variation, COV value) was 0.843 ± 0.401 for the control group and higher at 1.08 ± 0.546 for the SCL group (p < 0.001).

CONCLUSIONS

Repeat measures of central corneal thickness, using a non-contact specular microscope, is very similar to those taken on age-matched non-contact lens wearers. These results may not equally apply to similar pachymetry measures in patients wearing RGP lenses or for older patients wearing soft contact lenses.

Shape of the anterior surface of the cornea after extended wear of silicone hydrogel soft contact lenses

PURPOSE

To measure geometrical changes in the anterior surface of the cornea after wearing silicon hydrogel (SiH) soft contact lenses continuously for 1 week.

METHODS

Forty-three eyes with 3.0D of myopia and 22 eyes with 3.0D of hyperopia were enrolled in the prospective, interventional study. All subjects underwent a general eye examination, corneal tomography with wavefront aberration analysis, corneal thickness measurements and epithelial thickness mapping before and after wearing SiH lenses (Acuvue Oasys) for 7 days.

RESULTS

No significant changes in average keratometry were observed in either refractive group. In the myopic group, keratometry findings for the flat meridian (K1) and central corneal thickness decreased significantly. After +3.0 D lens wear in the hyperopic group, a significant decrease in epithelial thickness up to 3.19 µm was observed in the central and paracentral cornea, (p < 0.001). In both refractive groups, the largest epithelial thickness increase was seen in the periphery. A decrease in spherical aberration was noted in myopic eyes, while an increase of both higher order corneal aberrations and coma was found in hyperopic subjects.

CONCLUSION

Extended wear of SiH lenses results in a significant change in epithelial thickness leading to alteration in the geometry of the anterior surface of the cornea, particularly in hyperopic patients. These epithelial thickness variations lead to changes in the higher order aberrations of the cornea.

Duration of contact lens removal before myopic refractive surgery

PURPOSE

To compare refractive surgery outcomes in patients with different periods without contact lenses prior laser surgery.

MATERIALS AND METHODS

Patients included in this study underwent myopic keratorefractive laser surgery between January 2005 and December 2014. Patients were divided into three groups based on the duration of time passed free of soft contact lens wearing prior to final preoperative evaluation and surgery (<24 h, 1-3 days or >3 days). Spectacle wearers served as a control group. Postoperative safety index, efficacy index and % of eyes within 0.5 D of the four groups were compared. A general linear model was used to compare main outcomes while adjusting for age, gender, preoperative measurements, and procedure type (LASIK vs PRK).

RESULTS

Overall, 19,747 eyes were included. Soft contact lenses were worn by 42.3% (<24 h: 4.8%, 1-3 days: 18.5% and >3 days: 19.0%) and spectacles by 57.7% prior to surgery. In the PRK group, after adjusting for differences in baseline variables, the <24-h group had a significantly lower efficacy index than all the other groups. There were no significant differences between groups in terms of % eyes within ±0.5 D of intended correction (p = 0.55) or safety index (0.20). In the LASIK group, after adjusting for differences in baseline variables, there were no significant differences between groups in all primary outcomes.

CONCLUSION

Soft contact lenses should be removed at least 24 h prior to final preoperative evaluation and refractive surgery, especially for patients undergoing PRK.

The effect of the timing of the cessation of contact lens use on the results of biometry

BACKGROUND

Current guidelines vary regarding when to remove contact lenses prior to performing biometry, and there is no clear evidence behind these guidelines. This study aimed to determine the effect of soft contact lens wear on biometric measurements by examining the change in predicted lens power for emmetropia at several time points following removal of soft contact lenses.

METHODS

A prospective, controlled study of healthy soft contact lens wearers. Biometry was performed immediately after removing contact lenses and then after 2, 4 and 7 days of no contact lens use. Healthy non-contact lens wearers were used as controls. All measurements were taken with the Zeiss IOLMaster.

RESULTS

In all, 14 subjects and 13 controls were recruited. There was no significant difference in age or gender between groups. Eight of the fourteen subjects wore daily disposable CLs, two wore 2-weekly and four wore monthly soft CLs. Measurements from controls and contact lens-wearing subjects showed similar degrees of variation over time. The within-subject SD in predicted intraocular lens (IOL) power for emmetropia for contact lens wearers was 0.20 D (95% CI 0.16-0.25 D) compared to 0.18 D (95% CI 0.12-0.26 D) for controls.

CONCLUSIONS

There is a significant variation in UK practice regarding advice on the timing of cessation of contact lens wear prior to having biometry performed. Our study suggests that it is likely that soft contact lens wearers are currently being advised to remove their contact lenses for an unnecessarily long period of time prior to having biometry performed.

Influence of soft contact lens material on corneal warpage: prevalence and time to resolution

OBJECTIVE

Corneal warpage represents a reversible distortion of the corneal surface induced by soft contact lens (SCL) wear. The aim of the study is to assess the influence of SCL materials, age, wearing duration, cylindrical refraction, and spherical equivalence on the prevalence and time to resolution of corneal warpage.

METHODS

This is an interventional prospective study in which SCL wearers volunteered to remove their SCLs and underwent, on each visit, a corrected distance visual acuity and anterior and posterior segment evaluation, along with keratometry measurement and corneal topography. Visits were scheduled 30 minutes after SCL removal, on day 4, day 7, and then weekly after SCL removal until warpage resolution.

RESULTS

A total of 17 volunteers (34 eyes) were included, with 9 (18 eyes) in the hydrogel SCL group and 8 (16 eyes) in the silicone hydrogel SCL group. The difference in warpage prevalence between the hydrogel group (28%, 5 eyes) and silicone hydrogel group (31%, 5 eyes) was not statistically significant (p > 0.90). Duration necessary for warpage resolution ranged from 7 to 21 days with no statistically significant difference between the 2 groups (p = 0.12).

CONCLUSIONS

Both types of SCL had similar corneal warpage prevalence and time to resolution, with slightly longer mean time to resolution with silicone hydrogel. All eyes had resolution of warpage by 3 weeks. It seems more cautious to wait longer than the usual 1-week interval before performing refractive surgery, especially in patients wearing SCL for long periods and regardless of the type of material.

Corneal Biomechanical Findings in Contact Lens Induced Corneal Warpage

Purpose. To evaluate the difference in biomechanical properties between contact lens induced corneal warpage and normal and keratoconic eyes. Method. Prospective observational case control study, where 94 eyes of 47 warpage suspicious and 46 eyes of 23 keratoconic patients were included. Warpage suspected cases were followed until a definite diagnosis was made (warpage, normal, or keratoconus). Results. 44 eyes of 22 patients had contact lens related corneal warpage. 46 eyes of 23 people were diagnosed as nonwarpage normal eyes. 46 eyes of 23 known keratoconus patients were included for comparison. The mean age of the participants was 23.8 ± 3.8 years, and 66.2% of the subjects were female. The demographic and refractive data were not different between warpage and normal groups but were different in the keratoconus group. The biomechanical properties (corneal hysteresis or CH and corneal resistance factor or CRF) were different with the highest value in the warpage group followed by normal and keratoconus groups. CRF was 10.08 ± 1.75, 9.23 ± 1.22, and 7.38 ± 2.14 and CH was 10.21 ± 1.57, 9.59 ± 1.21, and 8.69 ± 2.34 in the warpage, normal, and keratoconus groups, respectively. Conclusion. Corneal biomechanics may be different in people who develop contact lens induced warpage.

The influence of soft contact lens wear and two weeks cessation of lens wear on corneal curvature

INTRODUCTION

Accurate corneal measurements are crucial in corneal refractive surgery (CRS) to ensure successful outcomes. Soft contact lens (SCL) wear may result in changes to corneal curvature and structure. United States Food and Drug Administration (FDA) pre-operative guidelines recommend that prior to CRS, SCL wearers cease SCL wear for "at least two weeks before examination and treatment" [1]. Corneal curvature changes induced by SCL wear may take longer than two weeks to resolve.

PURPOSE

To examine the effect of SCL wear on corneal curvature before and following two weeks SCL wear cessation. To explore the possible impact of different SCL materials and years of SCL wear.

METHODS

Retrospective data analysis, between a group of SCL wearers (SCL: n=45); and a non-contact lens control group (NCL: n=45). Corneal curvature parameters were measured using the Pentacam (Oculus, Germany), before and following two weeks cessation of SCL wear.

RESULTS

No significant differences in keratometry or Sagittal radius of curvature between SCL and NCL groups prior to or following SCL cessation. Tangential radius of curvature showed significant inferior steepening for the SCL group prior to SCL cessation (SCL vs. NCL; 7.77±0.30mm vs. 7.90±0.30mm; p=0.04). Following two weeks cessation of SCL wear this appeared to have resolved.

CONCLUSIONS

Two weeks cessation of SCL wear appears sufficient for resolution of corneal curvature changes with modern SCL materials and years of SCL wear. However, further studies with longer lens deprivation periods are required to ensure stability for all SCL wearing patients.