Changes in higher order wavefront aberrations after contact lens corneal refractive therapy and LASIK surgery

Orthokeratology in adults and effect on quality of life

OBJECTIVE

To determine changes in various ocular parameters of adults wearing orthokeratology (ortho-k) lenses and their levels of satisfaction and quality of life (QoL) after commencing treatment.

METHODS

Adults aged 18-38 years, with mild to moderate myopia and astigmatism < 1.50D, were wearing ortho-k lenses for one year. Data collection, which included history taking, refraction, axial length (AL), corneal topography, corneal biomechanics, and biomicroscopy examination, was performed at baseline and every 6 months during the study period. The level of satisfaction with the treatment and QoL was determined via questionnaires.

RESULTS

Forty-four subjects completed the study. AL was shortened significantly at the 12-month visit: AL -0.03 (-0.45 to 0.13) mm compared to baseline (p < 0.05). A significant number of subjects in both groups presented with overall and central corneal staining, but the majority were mild (Grade 1). Central endothelial cell density was reduced by 40/mm² (loss rate 1.4 %) (p < 0.05). High scores were obtained in the satisfaction questionnaire, with no significant differences between visits. At the 12-month visit, NEI-RQL-42 total score, dependence on correction, activity limitation, appearance, and satisfaction with the treatment all significantly increased compared to baseline values.

CONCLUSIONS

Results suggest that ortho-k can be an effective and safe myopia correction technique for adults with low to moderate myopia, improving daytime vision without serious adverse events. Satisfaction with ortho-k lens wear was high, particularly those who were dependent on vision correction and found spectacles or contact lenses limiting specific activities or cosmetically undesirable.

Effect of Orthokeratology Lens on Contrast Sensitivity Function and High-Order Aberrations in Children and Adults

OBJECTIVES

Overnight orthokeratology (OOK) lenses are used to temporarily decrease myopic refractive error and improve uncorrected vision. Overnight orthokeratology lenses significantly increase ocular and corneal high-order aberrations (HOAs) and compromise contrast sensitivity function (CSF) to a degree correlated with myopic correction achieved. In Taiwan, OOK lenses are mainly used in children for myopia control. However, information regarding its effects in this population remains limited. This study discusses the change in HOAs and CSF after 28 nights of OOK lens use in children compared with that in adults.

METHODS

In total, 46 children (9-18 years) and 26 adults (>18 years) who visited Ophthalmology Department of Mackay Memorial Hospital from October to December 2013 were enrolled. Contrast sensitivity and ocular/corneal total high-order, coma, and spherical aberrations (SA) were tested before OOK treatment. After 28 days of overnight use, CSF and topography were reexamined, and data were collected and analyzed using t test and Pearson correlation coefficients.

RESULTS

In total, 23 eyes of 23 children and 14 eyes of 14 adults were evaluated. The treatment resulted in a significant increase in ocular total HOA, coma, and SA in both groups. However, CSF declined more in adults than children.

CONCLUSION

Our study revealed that OOK lenses decrease CSF to a greater extent in adults than that in children despite no significant differences in the change of ocular HOAs between both subject groups. We proposed children may have better neural adaptation to compensate for optical aberrations induced by OOK lens use.

Orthokeratology in adults and factors affecting success: Study design and preliminary results

OBJECTIVE

To report the study design and one month's preliminary results of a randomized, single-masked, one-year prospective study of orthokeratology (ortho-k) in adults wearing lenses of different compression factors.

METHODS

Adults aged 18-38 years, with myopia of -0.75 to -5.00 D and astigmatism < 1.50 D, were recruited and randomly assigned into two groups: a conventional compression factor or Jessen Factor (CCF) group (compression factor = 0.75 D) and an increased (extra 1.00D) compression factor (ICF) group. Clinical outcomes, including spherical equivalent refraction (SER) reduction, visual acuity, corneal hysteresis (CH) and corneal resistance factor (CRF), and signs and symptoms were collected at the one-month follow-up visit. Indicators of the level of satisfaction and quality of life after commencing treatment were determined via a satisfaction questionnaire and the NEI-RQL-42 questionnaire.

RESULTS

Baseline data from 26 CCF and 24 ICF participants were analysed and no significant differences were observed between the two groups (p > 0.05). The first fit success rates were 90 % for CCF group and 83 % for the ICF group, SER reductions were 97 % and 95 % for the CCF and ICF group, respectively, with uncorrected high-contrast visual acuity of -0.06 (-0.18 to 0.42) and 0.00 (-0.16 to 0.52), respectively (p > 0.05) at the 1-month visit. Overall, the incidence of corneal staining was 77 % in the CCF and 79 % in ICF group; central corneal staining was 15 % and 33 %, respectively. However, the differences of corneal staining between the groups did not reach significance in any visit (p > 0.05). The main complaint from participants was glare (both groups). No significant differences in CRF and CH were found in the first month (p > 0.05). Both groups recorded high scores in the level of satisfaction questionnaire, with no significant differences between groups (p > 0.05). Compared with baseline scores, 1-month NEI-RQL-42 subscales of dependence on correction, appearance, and satisfaction with correction significantly increased, and the glare score significantly decreased in both groups (all p < 0.05).

CONCLUSIONS

The majority of participants were satisfied with the treatment and no serious corneal adverse effects were observed. These results demonstrate that ortho-k lenses of default and increased compression factor (1D) demonstrated similar clinical performance and ortho-k can be a safe and well-accepted option for myopia correction in adults, but long-term observation is warranted.

Accommodation response and spherical aberration during orthokeratology

PURPOSE

To evaluate the changes in the accommodative response and in the corneal and internal spherical aberration during 3 months of wear of orthokeratology lenses from the baseline.

METHODS

Fifty children aged 8 to 17 were recruited for a prospective study and were fitted with orthokeratology lenses. Refraction without cycloplegia, high and low uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), accommodation lag, horizontal near phoria without correction, corneal topography, corneal, and total wavefront aberration were performed at baseline, 1 day, 1 week, 1 month, and 3 months. Data were analyzed by Student's t test for related samples, repeated measures ANOVA test, and Pearson correlation test.

RESULTS

The spherical equivalent (SE) before and after 3 months was - 3.33 ± 1.60 D and - 0.30 ± 0.46 D, respectively. Accommodation lag was 0.53 ± 0.38 D and 0.20 ± 0.33 D at baseline and at 3 months, respectively. A moderate correlation between lag at the baseline and its change between baseline and the 3-month visit was found (P < 0.05; R = 0.748). The spherical aberration (SA) increased for anterior corneal and total measurement, being statistically significant for all visits (P < 0.05). The internal SA decreased: - 0.105 ± 0.006 at baseline and - 0.196 ± 0.203 at 1 week (P < 0.05). No difference between baseline and the follow-up visits in posterior corneal SA was found (P > 0.05) CONCLUSION: The negative SA of the lens increases during OK treatment compensated for the increase of the anterior corneal surface positive SA, in addition to increasing the accommodative response.

Relative peripheral refraction across 4 meridians after orthokeratology and LASIK surgery

Background

To characterize the axial and off-axis refraction across four meridians of the retina in myopic eyes before and after Orthokeratology (OK) and LASIK surgery.

Methods

Sixty right eyes with a spherical equivalent (M) between − 0.75 to − 5.25 D (cylinder <− 1.00 D) underwent LASIK (n = 26) or OK (n = 34) to treat myopia. Axial and off-axis refraction were measured with an open-field autorefractometer before and after stabilized treatments. Off-axis measurements were obtained for the horizontal (35° nasal and temporal retina) and vertical (15° superior and inferior retina) meridians, and for two oblique directions (45–225° and 135–315°) up to 20° of eccentricity. The refractive profile was addressed as relative peripheral refractive error (RPRE).

Results

OK and LASIK post-treatment results showed an increase of myopic relative refraction at several eccentric locations. At the four meridians evaluated, the M component of the pre-treatment RPRE values was not statistically different (p > 0.05) from the post-treatment RPRE within 30° and 20° of the central visual field after LASIK and OK, respectively. These results demonstrated that the treatment zone warrants an optimal central field of vision.

Conclusions

The present study gives an overview of RPRE after refractive corneal reshaping treatments (OK and LASIK) across vertical, horizontal and two oblique meridians together. This allows a 3D representation of RPRE at the retina and shows that the myopic shift induced by both treatments is more relevant in horizontal directions.

Effect of Iris registration on visual outcome in wavefront-guided LASEK for myopic astigmatism

PURPOSE

This study aimed to investigate the effect of iris registration (IR) on visual outcomes in wavefront-guided LASEK for myopic astigmatism.

METHODS

The retrospective chart review was performed for wavefront-guided LASEK using VISX Star S4 in patients with myopic astigmatism (cylinder ≥ 1.00 diopter[D]). Eyes were divided into IR group (LASEK with IR at the time of surgery) and Non-IR group (LASEK without IR system + failed-IR engagement during LASEK). Visual acuity (VA), astigmatism, higher-order aberration (HOA), and contrast sensitivity were assessed preoperatively and 3 months postoperatively. The IR and Non-IR groups were subcategorized depending on the spherical equivalent (lower myopia ≤-5.00 D vs. higher myopia >-5.00 D) for the comparison of HOA changes.

RESULTS

Postoperative uncorrected VAs showed no differences between IR (n = 30) and Non-IR (n = 46). In astigmatic vector analyses, no differences were noted in the mean magnitude of error and the mean angle of error between two groups. There were no differences in postoperative total HOA, spherical aberration (SA), coma, and trefoil between the groups, either. The total HOA and SA increased in both groups, while coma increased only in Non-IR. In higher myopia, ΔRMS of coma was smaller in IR. Preoperative and postoperative total HOA were linearly correlated in Non-IR, but not for IR. Contrast sensitivity of 12 cycles per degree improved in both groups.

CONCLUSION

IR had similar outcomes to conventional trackers in wavefront-guided LASEK, with less tendency of inducing coma, especially in higher myopia.

Prospective Cohort Comparison of Visual Acuity and Contrast Sensitivity Between Femto Laser In Situ Keratomileusis and Orthokeratology for Low-to-Moderate Myopia

PURPOSE

To compare the visual acuity and contrast sensitivity (CS) after femto laser in situ keratomileusis (fLASIK) and orthokeratology (OK) in patients with low-to-moderate myopia.

METHODS

A total of 68 patients were enrolled in this prospective cohort study. Of these, 40 eyes from 40 patients with low-to-moderate myopia underwent fLASIK and 28 eyes from 28 patients underwent OK. In addition to uncorrected distance visual acuity and corrected distance visual acuity, photopic and mesopic CS (with CSV-1000E) were tested before treatment and at 1, 3, and 6 months after treatment.

RESULTS

The preoperative refraction and CS were not significantly different between the groups (P>0.05). Postoperative visual acuity and refraction were similar (P>0.05). The photopic CS of the fLASIK group was better than that of the OK group (P<0.01). The fLASIK mesopic CS was better than the OK at 3 c/d (P=0.023). In the fLASIK group, only the photopic CS of postoperative 12 c/d decreased at 1 month and 3 months (P<0.01) and 18 c/d decreased at 1 month (P=0.002); whereas in the OK group, all the postoperative photopic CS values decreased at 1 month (all P<0.01) and 3 months (P<0.05) and increased to the normal level at 6 months (P>0.05). While as to the mesopic CS, in the fLASIK group, the 3 c/d, 6 c/d, and 18 c/d decreased at 1 month (P<0.05) and in the OK group, the 3 c/d decreased at 1 month and 3 months (P<0.05) and the 6 c/d decreased at 3 months (P=0.041), and the 12 c/d and 18 c/d decreased at 1 month (P<0.01).

CONCLUSIONS

These results show that fLASIK provides better visual quality than OK for patients with low-to-moderate myopia.

Laser in situ keratomileusis in 2012: a review

Laser in situ keratomileusis (LASIK) is a safe and effective treatment for refractive error. A combination of technological advances and increasing surgeon experience has served to further refine refractive outcomes and reduce complication rates. In this article, we review LASIK as it stands in late 2012: the procedure, indications, technology, complications and refractive outcomes.

Effect of temporal location of correction of monochromatic aberrations on the dynamic accommodation response

Dynamic correction of monochromatic aberrations of the eye is known to affect the accommodation response to a step change in stimulus vergence. We used an adaptive optics system to determine how the temporal location of the correction affects the response. The system consists of a Shack-Hartmann sensor sampling at 20 Hz and a 37-actuator piezoelectric deformable mirror. An extra sensing channel allows for an independent measure of the accommodation level of the eye. The accommodation response of four subjects was measured during a +/- 0.5 D step change in stimulus vergence whilst aberrations were corrected at various time locations. We found that continued correction of aberrations after the step change decreased the gain for disaccommodation, but increased the gain for accommodation. These results could be explained based on the initial lag of accommodation to the stimulus and changes in the level of aberrations before and after the stimulus step change. Future considerations for investigations of the effect of monochromatic aberrations on the dynamic accommodation response are discussed.