Retinal image quality in myopic children undergoing orthokeratology alone or combined with 0.01% atropine.

BACKGROUND: The retinal image quality derived from lower-order (LOA) and higher-order aberrations (HOA) for fixed 3-mm and photopic pupil diameters, in children undergoing combined 0.01% atropine and orthokeratology (AOK) versus those receiving orthokeratology alone (OK) over two years was evaluated. METHODS: The visual Strehl ratio based on the optical transfer function (VSOTF), derived from 2nd- to 4th-order terms (LOA and HOA combined), 2nd-order terms (LOA only), and 3rd- to 4th-order terms (HOA only) for fixed 3-mm and natural photopic pupil diameters, was compared between the two treatment groups. The individual Zernike coefficients for a fixed 3-mm pupil size of 2nd- to 4th-orders, root mean square (RMS) of LOA ([Formula: see text], [Formula: see text], and [Formula: see text] combined), HOA (3rd to 4th orders inclusive), and Coma ([Formula: see text] combined) were also compared between the two groups. RESULTS: Right eye data of 33 AOK and 35 OK participants were analysed. Under photopic conditions, significantly lower VSOTF based on HOA only was observed in the AOK group compared with that in the OK group at all post-treatment visits (all P < 0.05); however, interactions between HOA and LOA resulted in comparable overall retinal image quality (i.e., VSOTF based on LOA and HOA combined) between the two groups at all visits (all P > 0.05). For a fixed 3-mm pupil size, the VSOTF based on HOA only, LOA only, or HOA and LOA combined, were not different between the two groups (all P > 0.05). AOK participants had slower axial elongation (mean ± SD, 0.17 ± 0.19 mm vs. 0.35 ± 0.20 mm, P < 0.001), a larger photopic pupil size (4.05 ± 0.61 mm vs. 3.43 ± 0.41 mm, P < 0.001) than OK participants, over two years. CONCLUSIONS: HOA profile related to an enlarged pupil size may provide visual signal influencing eye growth in the AOK group.

Higher order aberrations and axial elongation in combined 0.01% atropine with orthokeratology for myopia control.

PURPOSE: To compare the changes in higher order aberrations (HOA's) for photopic and mesopic pupil diameters in children undergoing orthokeratology treatment (OK) or combined 0.01% atropine with orthokeratology treatment (AOK), and their association with axial elongation. METHODS: Children aged 6 to <11 years with 1.00-4.00 D of myopia were randomly assigned to each treatment group. Photopic and mesopic pupil diameters were quantified using automated pupillometry and HOA's were measured with a Hartmann-Shack aberrometer and Badal system to control for accommodation. HOA's were rescaled to photopic and mesopic pupil diameters and fitted with a 6th order Zernike polynomial expansion. Axial length was measured using an optical biometer under cycloplegia. RESULTS: Baseline and six-month data from 25 AOK and 28 OK participants were analysed. At the six-month visit, pupil diameter was larger in the AOK group under photopic conditions (3.70 ± 0.42 vs 3.12 ± 0.33 mm, p < 0.001), along with a range of HOA metrics [3rd to 6th order and higher order root mean square error values (HO RMS), all p ≤ 0.003] and individual Zernike terms (primary spherical aberration, and oblique quadrafoil, both p ≤ 0.03). Axial elongation was greater in the OK treatment group (0.05 ± 0.08 vs -0.01 ± 0.12 mm, p = 0.02). In the AOK group, axial elongation was correlated with the increase in photopic pupil diameter (r = -0.45, p = 0.02) and with several HOA metrics; however, these associations were not observed in the OK group. CONCLUSION: AOK treatment resulted in increased photopic pupil size and HOA's, and significantly less axial elongation over a six-month period compared to OK treatment alone. The improved myopia control observed with combination 0.01% atropine and orthokeratology may be a result of an enhanced optical effect due to a larger photopic pupil size.

Comparing a new hydroexpression technique with conventional forceps method for SMILE lenticule removal.

BACKGROUND: We described a modified 'hydroexpression' technique for the lenticule removal during small-incision lenticule extraction (SMILE) surgery and compared the results with conventional forceps method. METHODS: This was a retrospective, comparative study of 50 patients who underwent SMILE surgery by the same surgeon. We compared the 1-week and 3-months postoperative results after SMILE using the hydroexpression technique with the conventional forceps technique. Main outcome measures included uncorrected distance visual acuity, corrected distance visual acuity, refractive accuracy, safety index and efficacy index. RESULTS: The baseline characteristics were comparable between both groups. At postoperative 1 week, the safety index in forceps and hydroexpression group was 0.93±0.11 and 0.97±0.10, respectively (P=0.246). At 3 months, they were 1.00±0.06 and 0.99±0.09 (P=0.850). For efficacy indices, at 1 week they were 0.84±0.17 and 0.91±0.17 (P=0.158). At 3 months, they were 0.92±0.13 and 0.94±0.19 (P=0.624). All eyes aimed for a plano target. 96% in forceps group and 90% in hydroexpression group were within ±0.50 dioptre (D) in spherical equivalent refraction (SEQ) correction at postoperative 3 months (P=0.567). The mean errors of SEQ correction were -0.10±0.21 D in forceps group and -0.08±0.30 D in hydroexpression group (P=0.705). CONCLUSION: Hydroexpression was simple and safe and had early results comparable to the conventional forceps technique. This technique was particularly useful for cases with more adhesions between lenticule and anterior cap, thin lenticule cases and for the inexperienced SMILE surgeons.

Effect of the Learning Curve on Visual and Refractive Outcomes of Small-Incision Lenticule Extraction.

PURPOSE: To investigate the effect of the learning curve for small-incision lenticule extraction during the first 2 years of experience. METHODS: Small-incision lenticule extraction was performed using the 500-kHz VisuMax femtosecond laser (Carl Zeiss Meditec) by the same surgeon. The initial 100 patients since the surgeon started operating independently were considered as group 1; the recent 100 patients were considered as group 2. The same laser settings and technique were used. The visual and refractive outcomes were compared between groups at postoperative 1 week and 6 months. Vector analysis was performed for eyes with astigmatic correction. RESULTS: Two hundred right eyes of 200 patients were included. Age, preoperative corrected visual acuity, manifest refraction, and central corneal thickness were similar between groups (P ≤ 0.154). Postoperatively, the efficacy index at 1 week was better in group 2 (group 1: 0.85 ± 0.16 vs. group 2: 0.91 ± 0.10, P = 0.019) but was similar between groups at 6 months (group 1: 0.91 ± 0.14 vs. group 2: 0.94 ± 0.08, P = 0.181). The safety index was higher in group 2 at 1 week (group 1: 0.93 ± 0.10 vs. group 2: 0.95 ± 0.08, P = 0.045) and 6 months postoperatively (group 1: 0.97 ± 0.07 vs. group 2: 0.99 ± 0.03, P = 0.011). Vector analysis showed that postoperative residual astigmatism and misalignment of astigmatic correction were lower in group 2 than in group 1 (P ≤ 0.039) at 1 week and 6 months. The duration of docking and that of lenticule extraction was shorter in group 2 (P ≤ 0.034). CONCLUSIONS: Our study showed that faster visual recovery, better safety profile, and more accurate astigmatic correction could be attained with increasing surgical experience.

Presbyopic Correction Using Monocular Bi-aspheric Ablation Profile (PresbyMAX) in Hyperopic Eyes: 1-Year Outcomes.

PURPOSE: To present the 1-year outcomes of combining monocular bi-aspheric ablation profile and contralateral monofocal LASIK in hyperopic patients with presbyopia. METHODS: In this retrospective case series, 36 consecutive patients (72 eyes) who underwent simultaneous bi-aspheric ablation (PresbyMAX: SCHWIND Eye-Tech-Solutions GmbH and Co KG, Kleinostheim, Germany) in the non-dominant eye and monofocal regular LASIK in the dominant eye for correction of hyperopia and presbyopia were reviewed for 1 year. Binocular uncorrected distance (UDVA), near (UNVA), corrected distance (CDVA), and distance corrected near (DCNVA) visual acuity and manifest refraction were analyzed postoperatively. RESULTS: At 1 year, the mean binocular UDVA improved significantly from 0.26 ± 0.25 to 0.039 ± 0.088 logMAR (P < .001). Binocular UNVA also improved from 0.73 ± 0.30 to 0.10 ± 0.22 logRAD (P < .001). Eighty-seven percent of patients achieved UDVA of 20/25 or better and 90% had UNVA of J3 or better. Simultaneous binocular distance and near vision of 20/25 and J2 or better was achieved in 70%. Only 17% of patients had a binocular DCNVA of J2 or better. No patient suffered from a loss of 2 lines of CDVA. Refractive stability was achieved for both eyes from 1 month postoperatively. The re-treatment rate was 14% for improvement of near vision within 6 months to 1 year. CONCLUSIONS: Presbyopic correction using monocular PresbyMAX combined with monofocal regular LASIK in the fellow eye is safe and acceptable in hyperopic patients. [J Refract Surg. 2017;33(1):37-43.].

Comparison of the Demarcation Line on ASOCT After Simultaneous LASIK and Different Protocols of Accelerated Collagen Crosslinking: A Bilateral Eye Randomized Study.

PURPOSE: To compare the demarcation line depth after 2 different protocols of simultaneous laser in situ keratomileusis and collagen crosslinking (LASIK Xtra). METHODS: Twenty-three patients receiving bilateral LASIK Xtra were included in this comparative interventional study. The corneal stroma was soaked with 0.22% riboflavin for 90 seconds before flap repositioning. One eye was then randomized to receive either 18 mW/cm of ultraviolet A irradiation for 120 seconds or for 180 seconds, whereas the fellow eye received the other irradiation duration. The demarcation line on anterior-segment optical coherence tomography and grading of corneal haze on slit lamp were compared at postoperative month 1. RESULTS: The average age was 29.0 ± 8.2 years. There was no statistical difference in preoperative spherical equivalent refraction (P > 0.05). At postoperative 1 month, a well-defined demarcation line was visible in 74% and 70% in the 2- and 3-minute groups, respectively. The demarcation line depth was 282 ± 51 µm and 284 ± 43 µm, respectively (P = 1), and the ratio of the demarcation line depth to the postoperative central corneal thickness was 0.69 ± 0.13 and 0.72 ± 0.10 (P = 0.61). There was no difference in the percentage of eyes with grade 1 or 2 corneal haze (P = 0.76). CONCLUSIONS: The depth of the demarcation line was the same after receiving 18-mW/cm irradiation for either 2 or 3 minutes. The amount of early postoperative corneal haze was also similar. We postulate that there was lack of oxygen in the corneal tissue to fuel the photochemical reaction despite given additional time.

Effect of location of opening incision on astigmatic correction after small-incision lenticule extraction.

We compared the visual and refractive outcomes between 2 different incisional sites in small incision lenticule extraction (SMILE) for low myopic astigmatism. This was a contralateral eye study. Consecutive cases that underwent bilateral SMILE surgery were included. Procedures for both eyes were identical apart from the location of opening incision. The incision was set on the temporal side for the right eye (Group 1), while a superior incision was set for the left eye (Group 2). Twenty-nine patients with a mean age of 35.0 ± 9.6 years were included. Preoperative visual and refractive parameters were comparable between the 2 groups (p > 0.250). At 3 months, the logMAR uncorrected distance visual acuity was 0.074 ± 0.090 in Group 1 and 0.084 ± 0.130 in Group 2 (p = 0.861). No difference was found in the postoperative manifest spherical equivalent (p = 0.501) and manifest cylinder (p = 0.178) between the 2 groups. The efficacy index was 0.85 ± 0.16 in Group 1 and 0.85 ± 0.20 in Group 2 (p = 0.828). Astigmatic correction was not significantly affected by the location of opening incisions using vector analysis. Our study did not find significant differences in visual and refractive outcomes with temporal or superior opening incision during SMILE surgery.

Corneal Astigmatism and Aberrations After Combined Femtosecond-Assisted Phacoemulsification and Arcuate Keratotomy: Two-Year Results.

PURPOSE: To investigate the stability of corneal astigmatism and higher-order aberrations after combined femtosecond-assisted phacoemulsification and arcuate keratotomy. DESIGN: Retrospective, interventional case series. METHODS: Surgery was performed using a VICTUS (Bausch & Lomb Inc, Dornach, Germany) platform. A single, 450-µm deep, arcuate keratotomy was paired at the 8-mm zone with the main phacoemulsification incision in the opposite meridian. The keratotomy incisions were not opened. Corneal astigmatism and higher-order aberration measurements obtained preoperatively and at 2 months and 2 years postoperatively were analyzed. RESULTS: Fifty eyes of 50 patients (mean age 66.2 ± 10.5 years) were included. The mean preoperative corneal astigmatism was 1.35 ± 0.48 diopters (D). This was reduced to 0.67 ± 0.54 D at 2 months and 0.74 ± 0.53 D at 2 years postoperatively (P < .001). There was no statistically significant difference between postoperative corneal astigmatism over 2 years (P = .392). Both magnitude of error and absolute angle of error were comparable between the 2 postoperative time points (P > .283). At postoperative 2 months and 2 years, 72% and 70% of eyes were within 15 degrees of preoperative meridian of astigmatism, respectively. All wavefront measurements increased significantly at 2 months and 2 years (P < .007), except spherical aberration (P > .150). There was no significant difference in higher-order aberrations between 2 months and 2 years postoperatively (P > .486). CONCLUSIONS: Our study showed the stability of femtosecond-assisted arcuate keratotomy. Further studies using other platforms and nomograms are needed to corroborate the findings of this study.

Comparison of the Early Clinical Outcomes between Combined Small-Incision Lenticule Extraction and Collagen Cross-Linking versus SMILE for Myopia.

Background. To compare the early outcome of combined SMILE and collagen crosslinking (SMILE Xtra) with SMILE. Method. Prospective, comparative interventional study of 21 eyes receiving SMILE Xtra using a low energy protocol and 32 control eyes receiving SMILE only. The outcomes were compared at 1, 3, and 6 months postoperatively. Results. Both groups had myopia with spherical equivalent refraction (SEQ) > 4.00 D. The SMILE Xtra group had thinner preoperative central corneal thickness and residual stromal bed thickness (p < 0.021). At 6 months, no eyes lost more than 1 line in corrected distance visual acuity. The safety index was 0.96 ± 0.06 and 1.00 ± 0.00 in SMILE Xtra and control, respectively (p < 0.001). 89% and 94% of eyes were within ±0.50 D of target refraction, respectively, with the mean error in SEQ correction being -0.17 ± 0.26 D for SMILE Xtra and +0.03 ± 0.25 D for control (p = 0.021). The efficacy index was 0.88 ± 0.13 and 0.97 ± 0.06, respectively (p = 0.005). Conclusion. SMILE Xtra had good overall safety profile and predictability at 6 months. However, when compared with control, the safety index and efficacy index were statistically significantly lower in the early postoperative period.

Vector analysis of astigmatic correction after small-incision lenticule extraction and femtosecond-assisted LASIK for low to moderate myopic astigmatism.

AIM: To compare astigmatic correction between femtosecond-assisted laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE). METHODS: A total of 111 patients were included in this prospective study. Fifty-seven eyes were treated with LASIK and 54 eyes were treated with SMILE for myopia with low to moderate (-0.25 to -4.0 D) astigmatism. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity and manifest refraction were measured preoperatively and at 1 and 3 months postoperatively. Visual and refractive outcomes were reported. Changes in refractive astigmatism were evaluated using vector analysis. RESULTS: Preoperative characteristics were similar between both groups. The UDVA at 1 and 3 months was better in the LASIK group compared with the SMILE group (p<0.009). Postoperative cylinder was higher in the SMILE group (p<0.001). Fewer eyes attained the attempted cylindrical correction in the SMILE group (p<0.029). Vector analysis showed no significant difference in target-induced astigmatism (p=0.091) and angle of error (p>0.596) between the two groups. Surgically induced astigmatism was significantly lower in the SMILE group (p<0.023), while the difference vector (p<0.001) and absolute angle of error (p<0.016) were significantly higher in the SMILE group. No significant difference was found in these parameters between 1 and 3 months in both groups (p>0.122). CONCLUSIONS: Our results showed that SMILE offered a less favourable astigmatic correction comparable to femtosecond-assisted LASIK in eyes with low to moderate myopic astigmatism. The alignment of treatment was more variable in SMILE, leading to a lower efficacy compared with LASIK by 3 months postoperatively.

Vector Analysis of Corneal Astigmatism After Combined Femtosecond-Assisted Phacoemulsification and Arcuate Keratotomy.

PURPOSE: To evaluate the outcomes of femtosecond-assisted arcuate keratotomy combined with cataract surgery in eyes with low to moderate corneal astigmatism. DESIGN: Retrospective, interventional case series. METHODS: This study included patients who underwent combined femtosecond-assisted phacoemulsification and arcuate keratotomy between March 2013 and August 2013. Keratometric astigmatism was evaluated before and 2 months after the surgery. Vector analysis of the astigmatic changes was performed using the Alpins method. RESULTS: Overall, 54 eyes of 54 patients (18 male and 36 female; mean age, 68.8 ± 11.4 years) were included. The mean preoperative (target-induced astigmatism) and postoperative astigmatism was 1.33 ± 0.57 diopters (D) and 0.87 ± 0.56 D, respectively (P < .001). The magnitude of error (difference between surgically induced and target-induced astigmatism) (-0.13 ± 0.68 D), as well as the correction index (ratio of surgically induced and target-induced astigmatism) (0.86 ± 0.52), demonstrated slight undercorrection. The angle of error was very close to 0, indicating no significant systematic error of misaligned treatment. However, the absolute angle of error showed a less favorable range (17.5 ± 19.2 degrees), suggesting variable factors such as healing or alignment at an individual level. There were no intraoperative or postoperative complications. CONCLUSIONS: Combined phacoemulsification with arcuate keratotomy using femtosecond laser appears to be a relatively easy and safe means for management of low to moderate corneal astigmatism in cataract surgery candidates. Misalignment at an individual level can reduce its effectiveness. This issue remains to be elucidated in future studies.

Intraocular pressure profiles during femtosecond laser-assisted cataract surgery.

PURPOSE: To document the intraocular pressure (IOP) profiles during femtosecond laser-assisted cataract surgery. SETTING: Refractive cataract surgery center. DESIGN: Prospective case series. METHODS: Intraocular pressure was measured using a handheld portable applanation tonometer (Tono-Pen Avia) during femtosecond laser-assisted cataract surgery using the Victus platform. RESULTS: Forty-one eyes of 35 patients were recruited. The mean age of the patients was 70.5 years ± 8.2 (SD) (range 51 to 85 years). The mean IOP before, during, and after suction was 17.2 ± 3.2 mm Hg (range 10 to 23 mm Hg), 42.1 ± 10.8 mm Hg (range 20 to 55 mm Hg), and 13.8 ± 3.4 mm Hg (range 9 to 25 mm Hg), respectively. The mean difference between IOP before and during suction was 25.0 ± 11.3 mm Hg (range 5 to 43 mm Hg) (P<.01, Wilcoxon signed-rank test). The mean difference between IOP during and after suction was -28.7 ± 10.8 mm Hg (range -45 to -10 mm Hg) (P<.01, Wilcoxon signed-rank test). The mean suction duration was 216 ± 15 seconds (range 180 to 245 seconds). CONCLUSIONS: The increase in IOP during the suction phase of femtosecond laser-assisted cataract surgery was statistically significant compared with the baseline IOP. Caution should be taken in patients with ocular conditions that are vulnerable to IOP fluctuation. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Temporal interactive response is resistant to cloudy ocular media in the slow double-stimulation multifocal electroretinogram.

AIM: To examine the influence of cloudy media on the slow double-stimulation multifocal electroretinogram (mfERG). METHODS: Slow double-stimulation mfERG responses were measured from 26 subjects with normal ocular health under normal and light scattering conditions (induced using acrylic sheets) (Experiment 1) and another nine cataract patients before and after cataract surgery (Experiment 2). The amplitudes and implicit times of the first (M(1)) and second (M(2)) stimulation were compared under normal and light scattering conditions in Experiment 1 and they were compared under precataract and postcataract surgery in Experiment 2. RESULTS: Compared with control conditions (normal and postcataract surgery), the M(1) amplitude in the central region was significantly reduced in light scattering conditions (acrylic sheets and precataract surgery); the M(2) amplitude and both M(1) and M(2) implicit times of all regions examined were moderately affected in precataract surgery. The M(1):M(2) amplitude ratio and implicit time ratio were virtually unaffected in cloudy media for either central or mid-peripheral regions. CONCLUSION: Cloudy media affects the mfERG amplitude and implicit time in the slow double-stimulation, but does not affect the response ratio (ie, M(1):M(2) amplitude ratio and implicit time ratio) between the two stimulations. This suggests that the ratio analysis can be applied in patients with mild to moderately cloudy ocular media to evaluate the functional integrity of the retina.

Objective method to measure corneal clarity before and after laser in situ keratomileusis.

PURPOSE: To develop, evaluate, and use an objective method to determine the effect of laser in situ keratomileusis (LASIK) on corneal clarity. SETTING: Centre for Myopia Research, The Hong Kong Polytechnic University, and the Hong Kong Laser Eye Center, Hong Kong, China. METHODS: Color photographs of corneal sections were taken using a digital camera and converted to 8-bit gray-scale images. The desired area of the photograph was isolated using a preset mask, and a gray-scale or corneal clarity index of the desired area was obtained by averaging the "intensity" indices of individual pixels within the area. The reliability of the clarity index measures was determined by comparing test and retest measures. The sensitivity of the method was quantified by its ability to identify a small (clinically undetectable) decrease in corneal clarity produced by tight-fitting soft contact lenses worn for 30 minutes. Finally, corneal clarity was measured and compared in 24 patients before and 1 day, 1 week, and 1 month after LASIK. RESULTS: The reliability value was 4.11 corneal clarity units, and the change in corneal clarity due to soft contact lens use was 16.24 units. In the LASIK patients, there were statistically significant decreases in corneal clarity from preoperatively to 1 day and 1 week but not to 1 month. CONCLUSIONS: The method measured changes in corneal clarity that were undetectable clinically and were 4 times greater than 95% of the differences between test and retest measures. The method is therefore reliable and sensitive. Corneal clarity decreased after LASIK and recovered within approximately 1 month.

Contrast sensitivity after laser in situ keratomileusis. one-year follow-up.

PURPOSE: To determine whether contrast sensitivity measurement, a more sensitive test of visual function than visual acuity, better characterizes visual outcomes after laser in situ keratomileusis (LASIK). SETTING: Hong Kong Laser Eye Centre, Hong Kong, China. METHODS: Contrast sensitivity was monitored in 41 LASIK patients for 1 year. Seven spatial frequencies (0.3, 0.8, 1.5, 3.4, 6.9, 10.3, and 20.5 cpd) were tested with 15 sequences per spatial frequency, and a staircase technique was used for target presentation. RESULTS: There was a general depression in the contrast sensitivity function after LASIK; 1.5 cpd and 3.4 cpd were the most affected frequencies. Recovery took at least 6 months. The reduction in contrast sensitivity was greater for higher amounts of myopia. CONCLUSION: The post-LASIK nonpermanent depression in contrast sensitivity was probably due to optical factors.