George P.M. Cheng

Autogenous palmaris longus tendon as frontalis suspension material for ptosis correction in children

PURPOSE To determine the safety and efficacy of autogenous palmaris longus tendon as a sling material in frontalis suspension surgery for ptosis correction in children. METHODS In a prospective study, the authors evaluated 15 frontalis sling suspension surgeries using palmaris longus tendon in 14 consecutive children with congenital ptosis. The method of harvesting the palmaris longus tendon is described in detail. RESULTS The mean age of the patients was 4.7 years (range, 2 to 7 years). At a mean follow-up of 30 months (range, 20 to 40 months), all ptotic eyelids were successfully corrected with good final lid position. No recurrence of ptosis was encountered. In one eye, knot slippage of the sling was related to upper eyelid trauma, which was readily repaired. Otherwise, no exposure keratitis, wound infection, eyelid contour abnormality, or ptosis overcorrection occurred. There were no complications associated with the palmaris longus tendon donor site. CONCLUSION Frontalis suspension with autogenous palmaris longus tendon appears to be an effective treatment for congenital ptosis with poor levator function in children. Its use as an alternative material to fascia lata for sling surgery in children can be considered.

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.

Early outcomes after small incision lenticule extraction and photorefractive keratectomy for correction of high myopia.

We prospectively compared visual and refractive outcomes in patients with high myopia and myopic astigmatism after small-incision lenticule extraction (SMILE) and photorefractive keratetctomy (PRK) with mitomycin C. Sixty-six eyes of 33 patients (mean age, 29.7 ± 5.6 years) were included (SMILE: 34 eyes, PRK 32 eyes). Preoperatively, no significant difference was noted in manifest spherical equivalent (p = 0.326), manifest sphere (p = 0.277), and manifest cylinder (p = 0.625) between both groups. At 1 month, there were significant differences in logMAR uncorrected distance visual acuity, efficacy index and manifest refraction spherical equivalent between SMILE and PRK (p ≤ 0.029). At 6 months, the logMAR corrected distance visual acuity (p = 0.594), logMAR uncorrected visual acuity (p = 0.452), efficacy index (p = 0.215) and safety index was (p = 0.537) was comparable between SMILE and PRK. Significant differences were observed in postoperative manifest spherical equivalent (p = 0.044) and manifest cylinder (p = 0.014) between both groups. At the end of 6 months, 100% of the eyes in SMILE group and 69% of the eyes in PRK group were within ±0.50 D of the attempted cylindrical correction. The postoperative difference vector, magnitude of error and absolute angle of error were significantly smaller after SMILE compared to PRK (p ≤ 0.040) implying a trend towards overcorrection of cylindrical correction following PRK.

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.

Combined application of prophylactic corneal cross-linking and laser in-situ keratomileusis - a review of literature

Laser in‐situ keratomileusis (LASIK) is safe and effective laser refractive procedures in treating refractive errors. However, regression of treatment and iatrogenic keratectasia remain to be a major concern, especially in treating thin cornea with high ametropia. Collagen cross‐linking (CXL) is an effective method in stopping keratoconus progression through increasing the biomechanical strength of the cornea. Adjuvant cross‐linking to refractive procedures can theoretically help prevent regression and reduce the risk of keratectasia development by increasing the mechanical stability of cornea. During the procedure, riboflavin is directly applied to the corneal stroma, thereby reducing the need of de‐epithelialization as in the conventional protocol for keratoconus. Currently, there is still no consensus regarding the indication of CXL during refractive procedure, nor any standardized treatment protocol. This article aims to summarize the current evidence regarding the use of adjuvant CXL in LASIK.

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.

Comparison of corneal biomechanics after microincision lenticule extraction and small incision lenticule extraction

Objectives To evaluate and compare the change in corneal biomechanical properties after microincision lenticule extraction (MILE) and small incision lenticule extraction (SMILE). Methods In this prospective study, 60 eyes received MILE surgery with 2 mm opening incision, while 64 eyes received SMILE procedure with 5 mm opening incision. Corneal hysteresis (CH), corneal resistance factor (CRF) and 37 other biomechanical waveform parameters were quantitatively assessed using ocular response analyser (ORA) preoperatively and up to 6 months postoperatively. All changes were calculated as the difference between preoperative and postoperative values (Δ). Results Both CH and CRF values decreased significantly after MILE and SMILE (p<0.001). ΔCRF (o=0.028) and ΔCRF index (ΔCRF/preoperative CRF) (p=0.043) were statistically lower for all eyes at 1-week follow-up. ΔCH index (ΔCH/preoperative CH) was statistically lower at 1-week (p=0.043) and 1-month (p=0.015) follow-ups in MILE group when compared with SMILE group. In both MILE and SMILE group, ΔCH index and ΔCRF index were positively correlated with preoperative manifest refraction spherical equivalent, residual stromal thickness (RST) index (RST/preoperative central corneal thickness) and negatively correlated with lenticule thickness (p<0.05). Conclusions Both MILE and SMILE procedures significantly altered the biomechanical characteristics of cornea. Smaller opening incision was associated with less reduction in ORA parameters during early postoperative period.

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.