A comprehensive review on corneal crosslinking.

Corneal crosslinking (CXL) represents a paradigm shift in the management of corneal ectatic disorders. Before CXL was introduced, patients would need specialty contact lenses and possible corneal transplantation. CXL involves a biochemical reaction in which ultraviolet A light is used in conjunction with Riboflavin to form crosslinks in between corneal stromal collagen. This leads to strengthening and stabilizing of the collagen lamellae, resulting in mechanical stiffening of the cornea. Multiple protocols have been proposed including epithelium on versus off and varying light intensity and duration of treatment. All protocols appear to be safe and effective with few reported complications including infection, stromal haze, scarring, and endothelial toxicity. Overall, CXL has demonstrated to halt the progression of the disease clinically and in keratometry readings and improve the quality of life for patients. It is a minimally invasive, cost-effective procedure that can be performed in an outpatient setting with a fast recovery time and long-lasting results.

Comparison of Subjective Visual Experiences and Ocular Symptoms After Wavefront-Guided and Wavefront-Optimized LASIK in a Prospective Fellow Eye Study.

PURPOSE: The purpose of this study was to compare the subjective visual experience and ocular symptoms of fellow eyes treated with wavefront-optimized laser-assisted in situ keratomileusis (WFO-LASIK) and wavefront-guided laser-assisted in situ keratomileusis (WFG-LASIK). DESIGN: Prospective randomized fellow eye, controlled study. METHODS: A total of 200 eyes of 100 subjects from a single academic center were enrolled and randomly assigned to treatment with WFO-LASIK in one eye and WFG-LASIK in the fellow eye. Subjects filled out a validated 14-part questionnaire for each eye at the preoperative visit and at postoperative months 1, 3, 6, and 12. RESULTS: In comparing the number of subjects who reported symptoms in the WFG- vs WFO- LASIK eyes, there was no difference in the number reporting any visual experience (glare, halos, starbursts, hazy vision, blurred vision, distortion, double or multiple images, fluctuations in vision, focusing difficulties, and depth perception; all P > .05) or ocular symptoms (photosensitivity, dry eye, foreign body sensation, ocular pain; all P > .05). There was no preference for WFG-LASIK-treated (28%) or the WFO-LASIK-treated eye (29%), with the majority of subjects reporting no preference (43%; χ2P = .972). Of the subjects who preferred one eye or the other, the preferred eye saw statistically better than the fellow eye (0.8 ± 1.4 Snellen line, P = .0002). There was no other difference in subjective visual experience, ocular symptoms, or refractive characteristics when taking into account eye preference. CONCLUSIONS: The majority of subjects had no eye preference. For subjects who did have eye preference, the only detectable difference was better visual acuity in the preferred eye.

Patient-Reported Outcomes With Wavefront-Guided Laser in Situ Keratomileusis (PROWL) Study Outcomes From a Single Institution.

PURPOSE: To determine patient-reported outcomes after laser in situ keratomileusis (LASIK) using wavefront-guided technology at a single institution. METHODS: In this prospective observational study, 62 participants underwent examination and questionnaire at baseline, 1 month, and 3 months after surgery. The questionnaire included questions from validated questionnaires and new items to assess patient satisfaction with current vision and LASIK surgery, and existence/degree of visual symptoms. RESULTS: At month 1, patients reported an improvement in far vision (P = .01), activity limitations (P ≤ .001), and less worry about vision (P ≤ .001), as well as new visual symptoms, including halos (P ≤ .001) and double images (P = .03). At month 3, patients still noted an improvement in near vision (P = .05), far vision (P ≤ .001), activity limitation (P ≤ .001), and worry (P ≤ .001) along with halos (P = .05), double images (P = .01), and dry eye (P = .01). A total of 3.3% of patients at month 1 and 0% at month 3 had difficulty performing any activity due to symptoms, and 34.6% and 25.0% of patients reported decreased quality of life at months 1 and 3, respectively. CONCLUSIONS: After LASIK, patients experience new visual symptoms. Patients have high rates of satisfaction overall but with some patients reporting a decrease in quality of life 1 month after surgery; quality of life improves by postoperative month 3, with 25% patients reporting a decrease in visual well-being after surgery. [J Refract Surg. 2023;39(3):198-204.].

Patient-reported quality of vision in a prospective randomized contralateral-eye trial comparing LASIK and small-incision lenticule extraction.

PURPOSE: To compare patient-reported quality of vision and visual symptoms in participants undergoing laser in situ keratomileusis (LASIK) and small-incision lenticule extraction (SMILE). SETTING: Byers Eye Institute, Stanford University, Palo Alto, California. DESIGN: Prospective randomized contralateral-eye clinical trial. METHODS: Patients with myopia were randomized to receive wavefront-guided femtosecond LASIK in one eye and SMILE in the fellow eye. Participants reported the presence and severity of adverse visual symptoms through the Patient-Reported Outcomes With Laser In Situ Keratomileusis questionnaire and reported which eye had better vision at the preoperative and the postoperative 1-month, 3-month, 6-month, and 12-month visits. RESULTS: 80 eyes of 40 participants were treated. There was no difference in the presence or severity of double vision, glare, halos, or starbursts between eyes that underwent LASIK or SMILE at each visit ( P ≥ .85 for each comparison). Scaled scores for the presence of visual symptoms improved from the preoperative visit to the postoperative month 12 visit for double vision (88 vs 97, P = .03), glare (77 vs 92, P = .02), halos (68 vs 87, P < .01), and starbursts (60 vs 86, P < .01). At the postoperative month 12 visit, 17 (46%) of 37 participants preferred the vision from the eye that underwent LASIK compared with 7 (19%) of 37 who underwent SMILE. The preferred eye was correlated with uncorrected distance visual acuity ( r = 0.52, P < .01). CONCLUSIONS: Rates of visual symptoms were similar for LASIK and SMILE, and visual symptoms improved with time. More patients preferred vision from the eye that underwent LASIK compared with SMILE.

Corneal Sensitivity and Patient-Reported Dry Eye Symptoms in a Prospective Randomized Contralateral-Eye Trial Comparing Laser In Situ Keratomileusis and Small Incision Lenticule Extraction.

PURPOSE: To prospectively compare corneal sensation and patient-reported symptoms of dry eye in individuals undergoing laser in situ keratomileusis (LASIK) and small incision lenticule extraction (SMILE). DESIGN: Prospective randomized contralateral-eye clinical trial. METHODS: 80 eyes of 40 patients with myopia at Byers Eye Institute at Stanford University were randomized to receive wavefront-guided femtosecond LASIK in one eye and SMILE in the fellow eye. Cochet-Bonnet esthesiometry was performed to assess corneal sensitivity preoperatively and at the 1-, 3-, 6-, and 12-month postoperative visits. Participants also completed questionnaires at each visit to determine the Ocular Surface Disease Index (OSDI). RESULTS: Eyes that underwent LASIK compared to SMILE demonstrated more corneal denervation at the postoperative 1-month (mean 2.1 vs 3.6 cm, P < .001), 3-month (3.5 vs 5.4 cm, P < .001), and 6-month (4.7 vs 5.7 cm, P < .001) visits. At the 12-month visit, both groups had returned to baseline corneal sensitivity (5.9 vs 5.9 cm, P = .908). There was no difference in OSDI between the 2 groups at any visit. Mean OSDI improved from the preoperative to the postoperative 12-month visit in both LASIK (15.3 to 8.6, P = .020) and SMILE (15.1 to 9.5, P = .029) groups. CONCLUSIONS: LASIK resulted in greater corneal denervation compared to SMILE in the early postoperative period, though this difference was no longer apparent after 12 months. Despite this, there was no difference in self-reported dry eye symptoms between the 2 groups. Patient-reported dry eye symptoms improved after both LASIK and SMILE procedures.

Effect of corneal epithelial remodeling on visual outcomes of topography-guided femtosecond LASIK.

PURPOSE: To assess the effect of epithelial remodeling on visual outcomes over a 9 mm diameter corneal surface after topography-guided laser in situ keratomileusis (LASIK) for myopia correction using spectral-domain anterior segment optical coherence tomography (AS-OCT). SETTING: Outpatient clinical practice at the Stanford University Byers Eye Institute in Palo Alto, California. DESIGN: Prospective nonrandomized observational study. METHODS: Visual acuity, including uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA), 5% and 25% contrast sensitivity CDVA, manifest refraction, and corneal epithelial thickness after topography-guided femtosecond LASIK were analyzed. Corneal epithelial thickness was mapped across 13 sections and 3 concentric zones using AS-OCT preoperatively and at 1 month, 3 months, 6 months, and 12 months postoperatively. RESULTS: 60 eyes of 30 patients with a mean age of 32.8 years (range 23 to 52 ± 7.03 years) undergoing myopic LASIK correction were assessed. In eyes with complete follow-up data (n = 30), mean preoperative UDVA was logMAR 1.48 ± 0.45 and logMAR -0.11 ± 0.08 at postoperative 12 months. Mean preoperative CDVA was logMAR -0.08 ± 0.11 and logMAR -0.13 ± 0.07 at 12 months. Linear mixed modeling demonstrated a significant correlation between improvement in UDVA and decreased superior and nasal corneal epithelial thickness and between improvement in CDVA and increased central epithelial thickness 12 months postoperatively. CONCLUSIONS: Improvement in UDVA and CDVA at 12 months after topography-guided femtosecond LASIK was correlated with nonuniform epithelial remodeling, including epithelial thickening in the central zone and thinning in the superior and nasal sections as measured by AS-OCT.

Outcomes After Corneal Crosslinking for Keratoconus in Children and Young Adults.

PURPOSE: The aim of this study was to assess the effect of corneal crosslinking on vision and keratometry in children and young adults with progressive keratoconus. METHODS: A retrospective medical records review of patients aged 22 years or younger with keratoconus who underwent corneal crosslinking between January 2013 and November 2019 at Byers Eye Institute at Stanford University was conducted. Outcome measures included logarithm of the Minimum Angle of Resolution corrected distance visual acuity (CDVA); keratometry, including maximum keratometry (Kmax); pachymetry; and total wavefront aberration. Measurements were taken at baseline and at 12 and 24 months postoperatively. RESULTS: Fifty-seven eyes of 49 patients aged 12 to 22 years were assessed. The mean preoperative CDVA was logarithm of the Minimum Angle of Resolution 0.38 ± 0.32 (20/48), with a mean postoperative CDVA of 0.29 ± 0.31 (20/39) and 0.31 ± 0.31 (20/41) at 12 and 24 months postoperatively, respectively. Compared with preoperative mean Kmax, there was an improvement of -0.8 diopters (D) to a mean postoperative Kmax of 59.1 ± 9.1 D at 12 months and -1.3 D to 59.7 ± 8.8 D at 24 months. Subanalysis excluding the second eye of patients who underwent bilateral crosslinking showed similar results. Linear mixed modeling showed significant improvement in Kmax at both 12 and 24 months postoperatively. Minimum central corneal thickness initially decreased but stabilized at 24 months after crosslinking. Total wavefront aberration remained stable. CONCLUSIONS: Corneal crosslinking stabilizes, and in some cases improves, visual and corneal parameters in pediatric and young adult patients with keratoconus. The procedure is safe and well-tolerated and may prevent keratoconus progression in young patients.

Prospective, Randomized Contralateral Eye Comparison of Wavefront-Guided Laser In Situ Keratomileusis and Small Incision Lenticule Extraction Refractive Surgeries.

PURPOSE: Wavefront-guided laser in situ keratomileusis (WFG-LASIK) and small incision lenticule extraction (SMILE) are keratorefractive surgeries that can improve uncorrected visual acuity in myopic patients. Comparison of visual outcomes in myopic patients treated with LASIK and SMILE is needed. DESIGN: Prospective, randomized contralateral eye-controlled trial. METHODS: We performed a single-center prospective, randomized contralateral eye comparison of WFG-LASIK and SMILE (NCT03067077). Myopic patients with low levels of astigmatism were treated with WFG-LASIK in one eye and SMILE in the fellow eye from March 2017 to March 2021. Treatments were randomized by ocular dominance. WFG-LASIK and SMILE were performed. Postoperative evaluation at 1 day consisted of uncorrected distance visual acuity (UDVA), wavefront aberrometry, and a slit-lamp examination. On subsequent postoperative visits at 1 month, 3 months, 6 months, and 12 months, UDVA, manifest refraction, 5% and 25% low-contrast visual acuity, wavefront aberrometry, and slit-lamp examination were performed. MAIN OUTCOME MEASURE: The primary outcome measure was UDVA at 12 months. RESULTS: Eighty-eight eyes of 44 patients with myopia were enrolled in the study. Seventy-four eyes of 37 patients had successful treatments and completed 12 months of follow-up. At postoperative month 12, there were a significantly higher proportion of WFG-LASIK eyes that had ≥20/20 UDVA compared with SMILE eyes (94% vs 83%, P < .05). There was no difference between spherical equivalent between WFG-LASIK eyes and SMILE eyes (-0.17 ± 0.25 vs -0.29 ± 0.38, P > .05); there was no difference in higher order aberrations, including coma, trefoil, and spherical aberrations (P > 0.05); and there were a significantly higher proportion of WFG-LASIK eyes that had improved 5% and 25% low-contrast visual acuity compared with SMILE eyes (P < 0.05). CONCLUSIONS: WFG-LASIK and SMILE both offered marked improvements in corrected distance visual acuity and excellent predictability in both eyes. Compared with SMILE, WFG-LASIK resulted in faster visual recovery, better low-contrast visual acuity, and greater gains in uncorrected visual acuity.

Drug delivery to the anterior segment of the eye: A review of current and future treatment strategies.

Research in the development of ophthalmic drug formulations and innovative technologies over the past few decades has been directed at improving the penetration of medications delivered to the eye. Currently, approximately 90% of all ophthalmic drug formulations (e.g. liposomes, micelles) are applied as eye drops. The major challenge of topical eye drops is low bioavailability, need for frequent instillation due to the short half-life, poor drug solubility, and potential side effects. Recent research has been focused on improving topical drug delivery devices by increasing ocular residence time, overcoming physiological and anatomical barriers, and developing medical devices and drug formulations to increase the duration of action of the active drugs. Researchers have developed innovative technologies and formulations ranging from sub-micron to macroscopic size such as prodrugs, enhancers, mucus-penetrating particles (MPPs), therapeutic contact lenses, and collagen corneal shields. Another approach towards the development of effective topical drug delivery is embedding therapeutic formulations in microdevices designed for sustained release of the active drugs. The goal is to optimize the delivery of ophthalmic medications by achieving high drug concentration with prolonged duration of action that is convenient for patients to administer.

A Prospective Comparison of Wavefront-Guided LASIK versus Wavefront-Guided PRK After Previous Keratorefractive Surgery.

PURPOSE: To compare the results of retreatment with wavefront-guided LASIK versus wavefront-guided PRK for residual refractive error following previous myopic keratorefractive surgery. METHODS: In this prospective study, 32 eyes of 28 patients after prior myopic keratorefractive surgery underwent retreatment with flap-lift wavefront-guided LASIK (n = 12) or wavefront-guided PRK (n = 20) for residual refractive error. Safety, efficacy, predictability, and wavefront outcomes were evaluated. RESULTS: At last follow-up, both LASIK and PRK retreatment resulted in similar improvement in visual acuity with respective mean ± standard deviation (SD) uncorrected distance visual acuity of -0.07 ± 0.11 logMAR and -0.06 ± 0.13 logMAR (p = 0.87). In the study, 16.7% of LASIK and 33.3% of PRK eyes gained one or more lines of best-corrected distance visual acuity (CDVA), while 16.7% and 9.5% of eyes lost one or more lines of CDVA with LASIK and PRK, respectively. One hundred % of LASIK eyes and 89.5% of PRK eyes were within ± 0.50 diopters of emmetropia. Wavefront analysis demonstrated similar reductions in total RMS error higher-order aberrations (p = 0.84) with no difference in coma, trefoil, or spherical aberration between eyes undergoing LASIK or PRK retreatment. CONCLUSION: Wavefront-guided LASIK and wavefront-guided PRK following previous keratorefractive surgery demonstrate similar safety, efficacy, and predictability with comparable wavefront outcomes.

One-Year Outcomes From a Prospective, Randomized, Eye-to-Eye Comparison of Wavefront-Guided and Wavefront-Optimized PRK in Myopia.

PURPOSE: To compare wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) in patients with myopia using objective and self-reported quality of vision outcomes. METHODS: A total of 40 eyes from 20 participants were prospectively randomized to receive WFG or WFO PRK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser (Alcon Laboratories, Inc., Fort Worth, TX). The primary outcome measured was uncorrected distance visual acuity (UDVA) at 12 months postoperatively. Secondary outcome measures included corrected distance visual acuity (CDVA), less than 5% and less than 25% contrast visual acuity, changes in higher order aberrations (HOAs), and self-reported quality of vision. Patients completed a validated, Rasch-tested, linear-scaled 30-item questionnaire assessing the quality of vision and visual symptoms preoperatively and at each visit. RESULTS: There was no statistically significant difference (P > .05) between the WFG and WFO groups in the frequency of attaining a refractive error within ±0.25 diopters of emmetropia, achieving postoperative UDVA of 20/16 or better or 20/20 or better, losing one or two or more lines or maintaining their preoperative CDVA, or differences in UDVA, CDVA, low contrast acuity, or HOAs. None of the measured quality of vision parameters exhibited statistically significant differences between the groups preoperatively or at 12 months postoperatively (all P > .05). The WFG and WFO groups each showed significant improvement in multiple subjective measures compared to pretreatment values in the same eye. A total of 12.5% of patients preferred their WFG PRK eye, 31.25% preferred their WFO PRK eye, and 56.25% had no preference at 12 months postoperatively. CONCLUSIONS: WFG and WFO PRK using the Alcon Wave-Light Allegretto Eye-Q 400-Hz excimer laser platform provide similar results and self-reported visual symptoms in myopic eyes at 12 months postoperatively. [J Refract Surg. 2020;36(3):160-168.].

Prospective, randomized, eye-to-eye comparison of a new silicone corneal shield versus conventional bandage contact lens after photorefractive keratectomy.

PURPOSE: To compare uncorrected distance visual acuity (UDVA) and patient-reported outcomes with a new silicone corneal shield and a conventional bandage contact lens (BCL) after photorefractive keratectomy (PRK). SETTING: Stanford Eye Laser Center (Palo Alto, California) and Slade & Baker Vision (Houston, Texas). DESIGN: Prospective randomized cohort study. METHODS: Standardized bilateral wavefront-guided or wavefront-optimized PRK was performed in 25 patients with myopia. Each patient's dominant eye was randomized to either a silicone corneal shield or a conventional BCL, which was placed at the conclusion of surgery. The contralateral eye was assigned the other intervention. The UDVA and patient-reported outcomes were measured preoperatively, 1 hour after surgery, and at 1, 2, 3, 4, and 7 days postoperatively. RESULTS: At 1 day postoperatively, the mean logarithm of the minimum angle of resolution (logMAR) UDVA was 0.04 ± 0.16 (SD) in the silicone corneal shield group and 0.29 ± 0.22 in the BCL group (P < 0.01). At 7 days postoperatively, the mean logMAR UDVA was 0.09 ± 0.17 in the silicone corneal shield group and 0.23 ± 0.24 in the BCL group (P = .01). At 1 day through 3 days postoperatively, the patients reported greater pain, discomfort, foreign body sensation, and heavy eyelid in the eye with the silicone corneal shield. There was no statistically significant difference in the survey outcomes between the two groups at 4 days and 7 days postoperatively. CONCLUSIONS: The new silicone corneal shield was safe and effective, with faster visual recovery and a trend toward quicker epithelialization; however, it might be less comfortable than a conventional BCL.

Hydrogel sealant to prevent recurrent epithelial ingrowth in the setting of a LASIK flap buttonhole.

PURPOSE: To report the first case of hydrogel sealant to prevent the recurrence of epithelial ingrowth in a LASIK flap buttonhole. OBSERVATIONS: A 67-year-old female presented ten years after undergoing bilateral LASIK with diffuse lamellar keratitis and flap dislodgement after blunt trauma to the right eye. She was found to have epithelial ingrowth with diffuse debris and striae, so her flap was lifted and the epithelial ingrowth was removed. However, a central buttonhole was noted intraoperatively. Once all the epithelium was removed, the flap was repositioned and hydrogel sealant (ReSure, Ocular Therapeutix, Bedford, MA) was used to fill the buttonhole as well as seal down the edges of the flap. Sixteen months postoperatively, the patient's uncorrected visual acuity was 20/50-2 and there was no recurrence of the epithelial ingrowth at the edges of the buttonhole. CONCLUSIONS AND IMPORTANCE: Preventing the recurrence of epithelial ingrowth is a challenging situation, especially in the setting of a LASIK flap buttonhole. The use of hydrogel sealant in the buttonhole and around the edges of the flap may offer an elegant and effective solution.

Prospective, Randomized, Contralateral Eye Comparison of Wavefront-Guided and Wavefront-Optimized Laser in Situ Keratomileusis.

PURPOSE: To compare outcomes in wavefront-optimized (WFO) laser in situ keratomileusis (LASIK) to high-resolution wavefront-guided (WFG) LASIK. DESIGN: Randomized, fellow eye controlled, clinical trial. METHODS: A total of 200 eyes of 100 patients with myopia or compound myopic astigmatism undergoing bilateral LASIK between October 2015 and February 2017 underwent wavefront-optimized (WFO) LASIK in 1 eye and wavefront-guided (WFG) LASIK in the fellow eye. Each eye was evaluated for uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), contrast sensitivity, refractive error, and wavefront aberrometry. Outcome measurement primarily UDVA at 12 months. Secondary outcomes were safety, predictability, stability, refractive error, CDVA, contrast sensitivity, and higher-order aberrations at 12 months. RESULTS: WFG LASIK had higher levels of supervision and better contrast sensitivity compared to WFO. Both types had excellent postoperative UDVA results, without a significant difference in either mean UDVA or frequency of achieving a specified UDVA, for example, 20/16 or better (all P > 0.05). The mean gain in lines of CDVA was significantly higher in the WFG than in the WFO group (0.80 ± 0.75 vs 0.62 ± 0.72, respectively; P = 0.04). The WFG cohort had significantly better contrast sensitivity for mean and frequency of achieving >20/40 for <5% low-contrast sensitivity (37.1%; 95% confidence interval [CI], 27.5-46.7 vs 24.7%; 95% CI, 16.2-33.3, respectively; P = 0.01) and >20/32 for <25% low-contrast sensitivity (10.3%; 95% CI, 4.3-16.4 vs 4%, respectively; 95% CI, 0.0-8.1, respectively; P = 0.04). The WFO group had a significantly higher frequency of <0.25 diopters (D) of refractive astigmatism at 12 months (82.5%; 95% CI, 75.0-90.0; vs 72.1%, respectively; 95% CI, 63.2-81.2; P = 0.02) but not <0.50 D (95.6%; 95% CI, 91.9-99.8; vs 96.9, respectively; 95% CI, 93.5-100; P = 0.61). The WFG group was significantly closer to emmetropia for both sphere and spherical equivalents at all time points. Trefoil was significantly lower in the WFG group and was also significantly lower than preoperative measurements. CONCLUSIONS: Wavefront-optimized and high-resolution wavefront-guided LASIK achieve excellent visual outcomes. Nonetheless, treatments based on a high-resolution aberrometer appear to offer superior results in some regards.

Patient-reported vision-related quality of life after bilateral wavefront-guided laser in situ keratomileusis.

PURPOSE: To evaluate functional vision and quality-of-life outcomes after bilateral wavefront-guided laser in situ keratomileusis (LASIK). SETTING: Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California, USA. DESIGN: Prospective case series. METHODS: Visual acuity, refractive error, and aberrometric measurements were obtained preoperatively and 1, 6, and 12 months after bilateral wavefront-guided LASIK. The Refractive Status and Vision Profile questionnaire scores were completed at each timepoint and compared with baseline scores. RESULTS: The study comprised 84 eyes of 42 patients (aged 24 to 47 years). At 1 year, 76 eyes (90.5%) had an uncorrected distance visual acuity of 20/20 or better and 88.1% of patients were satisfied with their vision without correction. Total refractive status and vision profile scores improved significantly from a mean of 30.9 points at baseline to 20.7 points 1 year postoperatively (P < .001). The visual function, perceptions, and problems with corrective lenses subscales statistically significantly improved from preoperatively to postoperatively (all P < .001). In contrast, the driving (P = .286) and visual symptoms subscales (P = .199) did not show significant changes from baseline to 1 year. CONCLUSION: Wavefront-guided LASIK not only afforded clinically measurable improvements in vision but also significant improvements in subjective functional vision and vision-related quality of life 1 year after surgery.

Prospective evaluation of a novel silicone corneal shield after PRK: 6-month efficacy, safety, and predictability outcomes.

PURPOSE: The aim of this study was to report the 1-week and 6-month refractive outcomes of eyes treated with a novel silicone corneal shield designed to improve visual recovery after photorefractive keratectomy (PRK). PATIENTS AND METHODS: This prospective, observational clinical trial recruited 45 myopic eyes with or without astigmatism at a university eye clinic to undergo wavefront-guided PRK followed by application of an investigational silicone corneal shield that was removed on postoperative day 4. The primary outcome measures were efficacy, predictability, and safety at the 6-month visit. The secondary end points included short-term uncorrected distance visual acuity (UDVA) and pain. RESULTS: No adverse outcomes occurred using the device. At 6 months, 79.5% of eyes achieved UDVA >20/20, 94.9% achieved ≥20/25, and 97.4% achieved ≥20/40. Also, 2.6% lost one line of corrected distance visual acuity and none lost two lines; 71.8% and 97.4% measured within ±0.25 and ±0.50 D of emmetropia, respectively. During the first week, preoperative UDVA improved from 1.34 logarithm of the minimum angle of resolution (logMAR; <20/400 Snellen) to 0.14 logMAR (>20/30) on postoperative day 1 (P<0.0001) and remained stable on days 2-3 (all P>0.05). After removal of the shield on day 4, UDVA declined by two lines before rebounding to 0.16 logMAR (>20/30) on day 7 (both P<0.001). Subjective metrics of pain all peaked between days 2 and 3 before declining. CONCLUSION: The investigational silicone corneal shield is safe and effective when used after PRK and may aid early visual recovery and patient comfort, but comparative studies are needed to validate these preliminary findings. PRECIS: One-week and 6-month refractive outcomes of a novel silicone corneal shield used after PRK show that the device is not only safe and effective but may also speed visual recovery.

Astigmatic outcomes in myopic wavefront-guided laser in situ keratomileusis versus wavefront-guided photorefractive keratectomy using vector analysis.

PURPOSE: To compare astigmatic outcomes between eyes having wavefront-guided laser in situ keratomileusis (LASIK) and eyes having wavefront-guided photorefractive keratectomy (PRK). SETTING: Byers Eye Institute, Stanford University School of Medicine, Palo Alto, California, USA. DESIGN: Prospective randomized case series. METHODS: Patients had refractive surgery, with one eye treated with LASIK and the other treated with PRK. Eyes were randomized according to ocular dominance. Astigmatism vectors were evaluated using the Alpins vector analysis of astigmatism. RESULTS: Thirty-four patients (68 eyes) had vector analysis; the LASIK and PRK groups had similar target-induced astigmatism vectors (P = 0.75), surgically induced astigmatism vectors (P = 0.86), difference vectors (P = 1.0), indices of success (P = 0.4), correction indices (P = 0.28), and flattening indices (P = 0.5). CONCLUSION: Based on Alpins vector analysis of astigmatism, there were no statistically significant differences between eyes that had LASIK and eyes that had PRK.

Comparison of simulated keratometric changes following wavefront-guided and wavefront-optimized myopic laser-assisted in situ keratomileusis.

PURPOSE: The aim of the study was to determine and compare the relationship between change in simulated keratometry (K) and degree of refractive correction in wavefront-guided (WFG) and wavefront-optimized (WFO) myopic laser-assisted in situ keratomileusis (LASIK). METHODS: A total of 51 patients were prospectively randomized to WFG LASIK in one eye and WFO LASIK in the contralateral eye at the Byers Eye Institute, Stanford University. Changes in simulated K and refractive error were determined at 1 year post-operatively. Linear regression was employed to calculate the slope of change in simulated K (ΔK) for change in refractive error (ΔSE). The mean ratio (ΔK/ΔSE) was also calculated. RESULTS: The ratio of ΔK to ΔSE was larger for WFG LASIK compared to WFO LASIK when comparing the slope (ΔK/ΔSE) as determined by linear regression (0.85 vs 0.83, p = 0.04). Upon comparing the mean ratio (ΔK/ΔSE), subgroup analysis revealed that ΔK/ΔSE was larger for WFG LASIK for refractive corrections of >3.00 D and >4.00 D (0.89 vs 0.83; p = 0.0323 and 0.88 vs 0.83; p = 0.0466, respectively). Both linear regression and direct comparison of the mean ratio (ΔK/ΔSE) for refractive corrections <4.00 D and >4.00 D revealed no difference in ΔK/ΔSE between smaller and larger refractive corrections. CONCLUSION: WFO LASIK requires a smaller amount of corneal flattening compared to WFG LASIK for a given degree of refractive correction. For both, there was no significant difference in change in corneal curvature for a given degree of refractive error between smaller and larger corrections.

Vector Analysis of 1-Year Astigmatic Outcomes From a Randomized Fellow Eye Comparison of Photorefractive Keratectomy Using 2 Excimer Laser Platforms.

OBJECTIVE: To compare the astigmatic outcomes of photorefractive keratectomy (PRK) with a wavefront-guided (WFG) and a wavefront-optimized (WFO) excimer laser performed on two different platforms. METHODS: Setting: institutional. DESIGN: Prospective, randomized, fellow eye comparison clinical trial. PARTICIPANTS: A total of 142 eyes of 71 patients with myopia of 12 diopters (D) or less and astigmatism of 3D or less were enrolled at the Byers Eye Institute at Stanford between April 2009 and March 2011. INTERVENTION: One eye of each patient underwent WFG-PRK with the VISX CustomVue Star S4 IR (Abbott Medical Optics, Abbott Park, IL) and the contralateral eye underwent WFO-PRK with the Wavelight Allegretto Eye-Q 400-Hz laser platform (Alcon, Inc., Hüenberg, Switzerland). Alpins vector analysis of astigmatism was performed using manifest refraction measured preoperatively and 12 months postoperatively and vertexed to the corneal plane. Eyes were stratified for subgroup analysis based on preoperative manifest astigmatism. RESULTS: WFG-PRK and WFO-PRK were similar regarding surgically induced astigmatism, difference vector, magnitude of error, correction index, flattening index, and index of success. The angle of error was 60% less in the WFG group compared with the WFO group (4.9±1.1° vs. 11.8±2.4°, P=0.01). CONCLUSIONS: WFG-PRK with the VISX CustomVue Star S4 IR and WFO-PRK with the Alcon WaveLight Allegretto Eye-Q 400-Hz excimer laser platform produce similar astigmatic results in myopic patients; however, the WFG mode may produce slightly more predictable astigmatic corrections.