Effect of preoperative pupil size on quality of vision after wavefront-guided LASIK

Pupil size measurements with a multifunctional aberrometer/coherence interferometer/tomographer and two infrared-based pupillometers

PURPOSE

To compare precision of pupil size measurements of a multifunctional device (Pentacam AXL Wave [Pentacam]) and 2 infrared-based pupillometers (PupilX, Colvard) and to compare repeatability of Pentacam and PupilX.

SETTING

Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany.

DESIGN

Prospective, comparative trial.

METHODS

Pupil diameter of healthy eyes was measured with Colvard once and Pentacam without glare (WO) and with glare (WG), PupilX in 0, 1, and 16 lux 3 times each. In a second series, measurements with Pentacam WO and PupilX in 0.06 and 0.12 lux were assessed.

RESULTS

36 eyes of participants aged 21 to 63 years were included. Mean pupil diameter was 6.05 mm with Colvard, 5.79 mm (first series), 5.50 mm (second series) with Pentacam WO, 3.42 mm WG, 7.26 mm PupilX in 0, 4.67 mm 1, 3.66 mm 16, 6.82 mm in 0.06, and 6.39 mm in 0.12 lux. Measurements with Pentacam WO were significantly different to PupilX in 0, 0.06, 0.12, and 1 lux (all P < .001), but not to Colvard ( P = .086). Pupil size measured with Pentacam WG and PupilX in 16 lux was not significantly different ( P = .647). Consecutive measurements with Pentacam WO and WG had mean SD of 0.23 mm and 0.20 mm, respectively, and with PupilX 0.11 in 0, 0.24 mm 1, and 0.20 mm in 16 lux.

CONCLUSIONS

Pentacam provided good assessment of pupil size but was not equivalent to PupilX in low lighting conditions. Repeatability was more favorable for Pentacam.

Illumination levels in commonly used ophthalmic devices

Pupil diameter is a key parameter for corneal and multifocal intraocular lens surgery. Many devices are dedicated to measure the pupil size, but do not specify the illumination during capture. The aim of this study was to present illumination levels in routinely used ophthalmic devices which present pupil sizes. To obtain measurements, the lux meter was placed in the chin rest in the corneal plane and the room was completely dimmed. Ten measurements were taken for each device. The illumination levels for white and red Placido disk corneal topographers were 1253.1 ± 0.2 and 329.0 ± 0.2 lux, respectively (both photopic conditions). Scheimpflug corneal tomography should be considered as a mesopic measurement (14.5 ± 0.1 lux). Optical coherence tomography and autorefractometry are scotopic measurements (0.4-0.6 lux). We postulate that producers should provide illumination levels of their devices measuring pupil size. Moreover, when mentioning a pupil size, one should consider presenting to what lighting conditions it refers to.

Characteristics of disk halo size and its correlation with lenticule quality in small incision lenticule extraction for moderate to high myopia

PURPOSE

To investigate changes in disk halo size after small incision lenticule extraction (SMILE) and the correlation between halo size and lenticule quality in moderate to high myopia.

METHODS

Thirty eyes of 30 consecutive patients (mean age, 24.9 ± 4.5 years; mean spherical equivalent, -6.85 ± 1.18 D) undergoing SMILE were included in this prospective study. Lenticule surface quality was accessed with a scanning electron microscopy by a scoring system. Halo size was measured preoperatively and at 1, 3, and 6 months postoperatively. Multiple linear regression analysis was performed to explore associations between halo size and a range of factors, including lenticule quality.

RESULTS

Disk halo size increased slightly at 1 month and then recovered continually from 3 to 6 months postoperatively, with no difference between halo size during the preoperative period and at 6 months postoperatively (P > 0.05). One month after SMILE, halo size (1 cd/m2, 5 cd/m2) was associated only with uncorrected distance visual acuity (P ≤ 0.004). A halo size of 5 cd/m2 at 3 months postoperatively correlated with the anterior surface quality of the lenticule (P = 0.046). At 6 months postoperatively, a halo size of 1 cd/m2 was associated only with the baseline, accounting for 11.9% of the variability (P = 0.041); no correlations were found for the halo size of 5 cd/m2.

CONCLUSIONS

Disk halo size after SMILE was enlarged at an early stage postoperatively and subsequently declined to the baseline level during a 6-month follow-up. The quality of the lenticule surface influenced halo size changes in the early phase.

Comparison of visual quality after SMILE correction of low-to-moderate myopia in different optical zones

OBJECTIVE

To compare the effects of different optical zones for small-incision lenticule extraction (SMILE) on postoperative visual quality in low-to-moderate myopia.

METHODS

This retrospective case-control study involved patients who underwent SMILE using two optical-zone diameters: 6.5 mm (50 patients, 100 eyes) and 6.8 mm (50 patients, 100 eyes). Uncorrected visual acuity (UCVA), best corrected visual acuity, spherical equivalent (SE), corneal higher-order aberrations (HOAs), and subjective visual-quality questionnaire scores were assessed.

RESULTS

Postoperatively, UCVA and SE did not differ between the two groups (P > 0.05). In both groups, corneal HOAs, spherical aberration, and coma significantly increased at 1 and 3 months postoperatively (P < 0.05), while trefoil was unchanged after surgery (P > 0.05). Corneal HOAs, spherical aberration, and coma significantly differed between the groups at 1 and 3 months (P < 0.05), while trefoil did not (P > 0.05). Visual-quality scores were higher in the 6.8 mm group than in the 6.5 mm group at 1 month (P = 0.058), but not at 3 months (P > 0.05). In both groups, subjective scores significantly decreased at 1 month (P < 0.05) and gradually returned to the preoperative level at 3 months (P > 0.05). The subjective visual-quality scores were negatively and positively correlated with pupillary and optical-zone diameter, respectively (P < 0.05 for both). Objective visual-quality indicators (HOAs, spherical aberration, and coma) were negatively correlated with optical-zone diameter (P < 0.05) but not pupillary diameter (P > 0.05).

CONCLUSION

SMILE in different optical zones effectively corrected low-to-moderate myopia. The larger the optical-zone diameter, the better the early postoperative visual quality.

Bibliometric and visualized analysis of myopic corneal refractive surgery research: from 1979 to 2022

Background

Myopic corneal refractive surgery is one of the most prevalent ophthalmic procedures for correcting ametropia. This study aimed to perform a bibliometric analysis of research in the field of corneal refractive surgery over the past 40 years in order to describe the current international status and to identify most influential factors, while highlighting research hotspots.

Methods

A bibliometric analysis based on the Web of Science Core Collection (WoSCC) was used to analyze the publication trends in research related to myopic corneal refractive surgery. VOSviewer v.1.6.10 was used to construct the knowledge map in order to visualize the publications, distribution of countries, international collaborations, author productivity, source journals, cited references, keywords, and research hotspots in this field.

Results

A total of 4,680 publications on myopic corneal refractive surgery published between 1979 and 2022 were retrieved. The United States has published the most papers, with Emory University contributing to the most citations. The Journal of Cataract and Refractive Surgery published the greatest number of articles, and the top 10 cited references mainly focused on outcomes and wound healing in refractive surgery. Previous research emphasized "radial keratotomy (RK)" and excimer laser-associated operation methods. The keywords containing femtosecond (FS) laser associated with "small incision lenticule extraction (SMILE)" and its "safety" had higher burst strength, indicating a shift of operation methods and coinciding with the global trends in refractive surgery. The document citation network was clustered into five groups: (1) outcomes of refractive surgery: (2) preoperative examinations for refractive surgery were as follows: (3) complications of myopic corneal refractive surgery; (4) corneal wound healing and cytobiology research related to photorefractive laser keratotomy; and (5) biomechanics of myopic corneal refractive surgery.

Conclusion

The bibliometric analysis in this study may provide scholars with valuable to information and help them better understand the global trends in myopic corneal refractive surgery research frontiers. Two stages of rapid development occurred around 1991 and 2013, shortly after the innovation of PRK and SMILE surgical techniques. The most cited articles mainly focused on corneal wound healing, clinical outcomes, ocular aberration, corneal ectasia, and corneal topography, representing the safety of the new techniques.

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.

Sub-Bowman keratomileusis versus femtosecond laser in situ keratomileusis on the long-term visual recovery: A comparative study

Purpose

To explore the long-term visual quality of the same subjects after sub-Bowman keratomileusis (SBK) or femtosecond laser in situ keratomileusis (FS-LASIK).

Methods

This prospective study included patients screened for corneal refractive surgery at the Refractive Surgery Center of our Hospital between November 2017 and March 2018. One eye underwent SBK, while the other eye underwent FS-LASIK. Total higher-order aberrations, coma aberrations, and clover aberrations were evaluated before and at 1 month and 3 years after the procedure. The visual satisfaction of both eyes was investigated, respectively. The participants completed a surgical satisfaction questionnaire.

Results

Thirty-three patients were included. There were no significant differences in total higher-order aberrations, coma aberrations, and clover aberrations between the two procedures before and 1 month and 3 years after surgery (all P > 0.05), except for the total coma aberrations in FS-LASIK were significantly higher compared with the SBK group at 1 month after surgery [0.51 (0.18, 0.93) vs. 0.77 (0.40, 1.22), P = 0.019]. The surgical satisfaction questionnaire scores of the SBK group and the FS-LASIK group were 9.8 ± 0.8 and 9.8 ± 0.8, respectively, at 1 month, and 9.7 ± 0.9 and 9.7 ± 1.0, respectively, at 3 years (all P > 0.05).

Conclusion

There were no differences in corneal aberrations and satisfaction between SBK and FS-LASIK procedures at 1 month and 3 years.

Enhanced Ablation of Cornea Doped with a Fluorescein Dye Using a Visible Wavelength Laser

Myopia (nearsightedness) and presbyopia (aging eye) are the most common refractive errors of the human eye. Technology has advanced toward correcting aberration using various surgical procedures, including laser surgery, as well as prescribing corrective lenses. Hence, the effect of various laser wavelengths on the eye has been extensively studied over the last few decades. Usually, excimer lasers are used for this purpose, which increases the cost of the procedure because they are unique and difficult to manufacture and require regular maintenance. Due to the absorption properties, visible wavelengths do not interact with the corneal layers and hence are currently not used for eye surgery. This study presents the first clinical evidence that a 532 nm laser in combination with an eye-safe fluorescein dye that is in wide clinical use in ophthalmology can be utilized for high-precision ablation purposes due to the photochemical reaction that occurs on an ex vivo porcine eye. Our results show the promise of utilizing inexpensive visible wavelength lasers in the ablation of biological tissues, reducing the high costs of ophthalmological surgical procedures, as well as in other applications.

Higher-Order Aberrations of Topography-Guided LASIK and Wavefront-Optimized LASIK in High- and Low-Myopic Eyes: A Non-Randomized Controlled Trial

We aimed to investigate high-order aberration (HOA) change between topography-guided (TG) and wavefront-optimized (WFO) laser in situ keratomileusis (LASIK) in patients with different degrees of myopia. A non-randomized clinical trial was conducted, in which 40 eyes of 20 patients aged 20–50 years old were included. Participants received TG-LASIK in one eye and WFO-LASIK on the alternate eye. Corneal topography and HOAs including coma, trefoil, spherical aberration (SA), and contrast sensitivity (CS) were collected. Moreover, a quality of vision (QoV) questionnaire was completed by each participant. Non-parametric tests were used to infer the difference in HOAs and CS between the TG-LASIK and WFO-LASIK groups, and subgroup analyses stratified by myopia degree were performed. The high-myopia patients with TG-LASIK showed more coma and SA compared to low-myopia individuals (all 95% CI lower limits > 0), and subjects who received WFO-LASIK exhibited more SA in high-myopia status (both 95% CI lower limits > 0). The TG-LASIK group showed lower postoperative trefoil compared to the WFO-LASIK group in the high-myopia population (mean difference: −0.1267, 95% CI: −0.24 to −0.01). The TG-LASIK group yielded less surgically induced haze, better clarity at night, and better total quality scores (all p < 0.05). In conclusion, TG-LASIK might yield less postoperative trefoil in high-myopia patients and higher QoV in the general population compared to the WFO-LASIK procedure.

Effect of Wavefront Aberrations on Night Vision Problems and Mesopic Contrast Threshold After SMILE

PURPOSE

To investigate the effect of wavefront aberrations on night vision problems and mesopic contrast threshold after small incision lenticule extraction (SMILE).

METHODS

Forty-two participants (84 eyes) who underwent SMILE were included in this prospective observational study. Visual outcomes including uncorrected distance visual acuity (UDVA), subjective manifest refraction, mesopic contrast threshold (Binoptometer 4P; Oculus Optikgeräte GmbH), and higher order aberrations (HOAs) were analyzed before and 3 months after surgery. The patient's night vision satisfaction was assessed using a questionnaire.

RESULTS

The mean spherical equivalent was -5.30 ± 1.38 diopters (D) preoperatively and -0.06 ± 0.15 D postoperatively. UDVA was better than 20/20 in 98.81% of the patients and better than 20/25 in all patients. Scores of night vision satisfaction and glare changed significantly in the postoperative period (F = 8.463, P = .001; F = 69.518, P < .001, respectively). Preoperative spherical diopters (lower order aberrations) were positively correlated with night vision satisfaction (r = -0.329, P = .041) and glare score (r =-0.332, P = .039). Age (odds ratio [OR] = 1.272, 95% CI = 1.019 to 1.589) and preoperative spherical diopter (OR = 0.437, 95% CI = 0.199 to 0.975) were correlated with night vision satisfaction scores by analysis of binary regression. The root mean square value of total HOAs increased 3 months after surgery (t = -6.873, P < .001) with an increase in horizontal coma (Z₃¹) and spherical aberration (Z₄⁰) (P < .001). No correlation was observed between glare score and HOAs; however, patients with higher preoperative myopia demonstrated continuously decreasing contrast under mesopic conditions and higher postoperative horizontal coma.

CONCLUSIONS

Myopic patients with higher preoperative spherical errors experienced more glare at night after SMILE surgery. Postoperative horizontal coma was associated with worse mesopic contrast thresholds. [J Refract Surg. 2021;37(7):446-452.].

Long-term outcomes of intravitreal activated protein C injection for ischemic central retinal vein occlusion: an extension trial

Purpose

Our previous 1-year pilot study evaluated the efficacy of intravitreally injected activated protein C (APC) in 10 eyes with ischemic central retinal vein occlusion (CRVO). The reperfusion of the areas of retinal nonperfusion (RNP) exceeded 50% of the baseline in five (50%) eyes 1 year after the APC injection. The current study evaluated the long-term efficacy and safety of intravitreal APC.

Methods

The 10 eyes in the pilot study were included in this study. Other treatments were administered at the physicians’ discretion after the pilot study. We evaluated visual acuity (VA), central retinal thickness (CRT) and perfusion status, and adverse events and severity over the long term.

Results

The median follow-up was 60 months (range, 48–68 months). Compared with baseline, the post-treatment VA improved significantly (P < 0.001) from 1.39 to 1.06 logarithm of the minimum angle of resolution. The CRT improved significantly (P < 0.001) from 1090 to 195 μm at the last visit. The RNP areas decreased from an average 29.7 disc areas (DAs) at baseline to an average 16.5 DAs at the last examination (mean, 40 ± 6.5 months after the first APC treatment). No adverse events were related to intravitreal APC.

Conclusion

No complications were associated with intravitreal APC, the clinical course improved, and improved RNP was maintained for the long term, suggesting that intravitreal APC may be an alternative treatment for CRVO.

Temporal evolution of the biological response to laser-induced refractive index change (LIRIC) in rabbit corneas

Laser-induced refractive index change (LIRIC) is a new, non-incisional, non-ablative, femtosecond photo-modification technique being developed for vision correction in humans. Prior, exvivo studies showed intra-tissue refractive index change to induce minimal cell death, restricted to the laser focal zone in the corneal stroma, and with no observable damage to the epithelium or endothelium. Here, we used live rabbits to ascertain longer-term consequences of LIRIC in vivo. Specifically, we assessed cell death, fibrosis, corneal nerve distribution, endothelial cell density, and corneal structure for up to 3 months after LIRIC. A +2.5 D gradient-index LIRIC Fresnel lens was inscribed inside 20 applanated corneas of Dutch Belted rabbits, over a circular region of the mid-stroma measuring 4.5 mm in diameter. Twelve additional rabbit eyes were used as applanation-only controls to differentiate the effects of laser treatment and suction applanation on biological and structural parameters. In vivo optical measurements were performed pre-operatively, then immediately, 2, 4, and 12 weeks after the procedure, to measure endothelial cell density and changes in corneal structure. Groups of four rabbits were sacrificed at 4 hours, 2, 4, and 12 weeks after LIRIC for histological determinations; the TUNEL assay was used to evaluate cell death, H&E staining was used to assess inflammatory infiltration, and immunostaining for α-smooth muscle actin (α-SMA) and βIII tubulin (Tuj-1) was performed to assess myofibroblast differentiation and corneal nerve distribution, respectively. Consistent with prior ex vivo data, only minimal cell death was observed in the laser focal zone, with TUNEL-positive cells restricted to the stromal region of refractive index change 4 h after LIRIC. No TUNEL-positive cells were evident anywhere in the cornea 2, 4, or 12 weeks after LIRIC. Applanation-only corneas were completely TUNEL-negative. Neither LIRIC-treated nor applanation-only eyes exhibited α-SMA-positive staining or altered corneal nerve distributions at any of the time points examined. In vivo confocal imaging revealed normal endothelial cell densities in all eyes (whether LIRIC-treated or applanation-only) at all time points. Optical coherence tomography showed suction applanation to cause a temporary decrease in central corneal thickness, which returned to normal within 4 h. Corneas into which LIRIC Fresnel lenses were written while applanated did not undergo major structural or shape changes beyond the temporary thinning already described for suction applanation. The present findings suggest that LIRIC patterns, which generated a clinically-relevant refractive correction in the mid-stromal region of live rabbit corneas, induced little-to-no disruption to corneal structure and biology for 3 months after the procedure. This affirms the relative safety of LIRIC and predicts that compared to traditional laser vision correction surgeries, common post-operative complications such as dry eye, haze, or patient discomfort may be entirely avoided.

Pupillodynamics and corneal spherical aberrations in a set of Indian cataract patients and its implications for aberrometric customisation of intraocular lenses

Purpose:

Assessment of pupil diameter in various light conditions and the corresponding corneal spherical aberrations in a cohort of Indian eyes with bilateral senile cataracts and the possible use of this data in aberrometric customization of intraocular lenses (IOLs).

Methods:

In this prospective observational study done at a tertiary eye care centre in India, the selected patients were subjected to measurement of their pupil diameters in scotopic, mesopic, and photopic conditions as well as the corresponding corneal spherical aberrations, using the Sirius Topographer (Costruzione Strumenti Oftalmici, Florence, Italy). Shapiro–Wilk test, Independent t-test, ANOVA with Bonferroni correction on post-hoc testing were used for statistical analysis.

Results:

104 eyes of 52 patients were enrolled for the study. The mean age was 53 ± 11.88 years. The mean scotopic, mesopic, and photopic pupil sizes were 4.37 mm (4.11–4.63 mm), 3.92 mm (3.71 mm–4.15 mm), and 3.37 mm (3.18–3.67 mm), respectively. There was a statistically significant difference (P = <0.001) in the mean corneal spherical aberration measured at the 6 mm zone (0.23 ± 0.02 microns) and at the 4 mm zone (0.06 ± 0.01 microns).

Conclusion:

The mean corneal spherical aberration corresponding to the average mesopic pupil size of our patient population was substantially lower than that of the scotopic pupil size and also less than the amount corrected by most of the negative aspheric IOLs. This perhaps indicates the need for customising IOLs based on the spherical aberrations of cornea at the zone corresponding to the mesopic pupil diameter for optimal residual total postoperative spherical aberrations.

The effect of refractive surgery on blur thresholds

Purpose:

The aim of this study was to measure blur thresholds before and after refractive surgery.

Methods:

In this prospective cohort study conducted in a tertiary eye hospital in South India. Blur thresholds were measured for 30 young adult myopic patients 1 month prior to and after refractive surgery. Patients were asked to report three stages of blur, namely Detectable Blur (DB), Bothersome Blur (BB), and Non-resolvable Blur (NB). Blur was created by adding plus lenses (in steps of 0.12D) over their optimal subjective refraction. The blur judgments were made both monocularly and binocularly when looking through a 3 mm artificial pupil at one line above the best-corrected visual acuity.

Results:

A total of 30 participants were included in this study (mean age = 25.5 ± 3.8 (20–36) years; 77% female). The mean binocular preoperative blur of this group was: DB = 0.39 ± 0.26D, BB = 0.74 ± 0.28D and NB = 1.04 ± 0.42D. The corresponding mean binocular blur one-month post-operatively was DB = 0.46 ± 0.28D, BB = 0.83 ± 0.35D, and NB = 1.21 ± 0.44D. Although there was a marginal increase in the blur thresholds postoperatively, the difference was not statistically significant (DB: P = 0.320; BB: P = 0.229; NB: P = 0.054).

Conclusion:

All three blur thresholds showed an insignificant minimal increase at 1 month post-operatively suggesting that patients adapt to the induced blur following refractive surgery. A longer follow up would reveal how the adaptation to blur would change with time.

Relationships Between Haloes and Objective Visual Quality in Healthy Eyes

Purpose

To determine the normal values and relationships between haloes and objective optical quality in healthy eyes.

Methods

In this cross-sectional study, haloes, pupillary responses to light, and objective optical quality were measured with the optical quality analysis system (OQAS) and a vision monitor (MonCv3) in 138 right eyes of 138 healthy young men with mean spherical equivalent of 0.32 ± 0.47 D.

Results

The mean disc halo size was 77.17 ± 25.03 arcmin. The mean objective optical quality values were as follows: objective scatter index (OSI), 0.58 ± 0.33; Strehl ratio (SR), 0.21 ± 0.05; modulation transfer function cutoff, 36.27 ± 7.98 cpd; OQAS value (OV)100%, 1.21 ± 0.27; OV20%, 0.91 ± 0.23; and OV9%, 0.59 ± 0.16. Disc halo size correlated independently with OSI (P < 0.001) and minimum pupil size (P = 0.003) by forward stepwise regression analysis (disc halo size = 16.60 + 26.24 × OSI + 11.34 × minimum pupil size; R² value = 17.7%; F = 14.52; P < 0.001).

Conclusions

Reference values for disc halo size and objective optical quality in healthy young subjects were established. Eyes with worse objective vision quality exhibited larger haloes.

Translational Relevance

The study provided the knowledge and the relationships of OQAS and halo measurements from a well-defined group of healthy young subjects. Both measurements are useful in clinical practice to help quantify the vision quality and complement each other.

Quality of life impact of refractive correction (QIRC) results three years after SMILE and FS-LASIK

Background

This study aimed to compare long-term postoperative quality of life and satisfaction differences between SMILE and FS-LASIK for myopia correction.

Methods

This cross-sectional study enrolled patients under the age of 39 years, who chose to undergo SMILE or FS-LASIK surgery to both eyes 3 years previously. Patients completed a common vision test and Quality of Life Impact of Refractive Correction (QIRC) questionnaire, together with the surgical satisfaction, adverse symptoms subjective survey. Patients with preoperative corrected distance visual acuity and postoperative uncorrected distance visual acuity of 20/20 or greater were included. Propensity score matching (PSM) was used to match the preoperative and postoperative spherical equivalent, age, and designed optical zones of the left and right eyes between the two groups.

Results

Forty-nine patients were included in each group after PSM from 188 patients. No significant difference in the total QIRC score was found between the SMILE and FS-LASIK groups (45.89 ± 5.91 vs 45.09 ± 5.65, p = 0.492). There were no differences in surgical satisfaction between the groups (p = 0.178). Compared to the SMILE group, the FS-LASIK group had more glare (2.12 ± 2.25 vs 3.22 ± 2.54, p = 0.026) and severe dryness (1.80 ± 1.98 vs 2.79 ± 2.19, p = 0.021).

Conclusion

Postoperative quality of life is similar after SMILE or FS-LASIK. Dry eye symptoms and glare were milder in the SMILE group than in the FS-LASIK group.

Baseline clinical features predict visual outcome in young patients with central retinal vein occlusion

PURPOSE

To evaluate prognostic factors in young patients with central retinal vein occlusion (CRVO).

METHODS

Retrospective case series. CRVO patients aged ≤ 50 and follow-up ≥ 6 months were enrolled. The best corrected visual acuity (BCVA) and central retinal thickness (CRT) at baseline, 3 months, 6 months, and last visit were documented. Severity of retinopathy was graded by comparing to standard photos. Prognostic factors associated with visual outcome at 6 months were evaluated by multiple linear regression models.

RESULTS

A total of 73 eyes from 69 patients with mean age 37.6 ± 8.5 were enrolled. Forty-seven (68%) patients were male. The mean follow-up duration was 25.9 ± 23.0 months. LogMAR BCVA improved from 0.979 ± 0.785 at baseline to 0.594 ± 0.748 at the 6 months (p < 0.001) and CRT improved from 475 ± 222 μm to 299 ± 104 μm (p < 0.001). Forty-eight (66%) eyes required anti-vascular endothelial growth factor (anti-VEGF) treatment. The mean number of injections was 2.25 ± 1.41 in the first 6 months and 75% of eyes received ≦ 3 injections during the clinical course. The baseline BCVA (coefficient 0.518, p < 0.001), grade of retinal hemorrhage (coefficient 0.230, p = 0.006), grade of retinal venous engorgement (coefficient 0.238, p = 0.011), grade of optic disc edema (coefficient - 0.226, p = 0.005), and diabetes mellitus (coefficient 0.264, p = 0.047) were the independent factors associated with visual outcome at 6 months.

CONCLUSIONS

Baseline clinical features are useful for the prediction of visual outcome at 6 months in young CRVO patients.

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.].

Minimum pupil in pupillary response to light and myopia affect disk halo size: a cross-sectional study

OBJECTIVES

To evaluate the relationship between pupillary response to light, myopia and disk halo size.

DESIGN

Cross-sectional study.

SETTING

Single refractive surgery centre.

PARTICIPANTS

In this study, 197 right eyes of 197 patients between 20 and 35 years of age were evaluated for disk halo size and pupillary response to light with a vision monitor.

PRIMARY AND SECONDARY OUTCOME MEASURES

Halo radius, age, spherical equivalent (SE), axial length (AL), initial diameter, amplitude of contraction, latency of contraction, duration of contraction, velocity of contraction, latency of dilation, duration of dilation, velocity of dilation, maximum pupil, minimum pupil, average pupil and dark pupil.

RESULTS

Significant associations were found between disk halo size and SE (r=-0.219, P=0.002), AL (r=0.152, P=0.033) and minimum pupil (r=0.149, P=0.037). There were no associations between disk halo size and initial diameter, amplitude of contraction, latency of contraction, duration of contraction, velocity of contraction, latency of dilation, duration of dilation, velocity of dilation, maximum pupil, average pupil, dark pupil and age (P>0.05). A significant difference in disk halo size was detected between the low-moderate and high myopia (SE< -6 D) groups (P=0.002) and between the small and large (minimum pupil≥4 mm) minimum pupil size groups (P=0.014).

CONCLUSIONS

Patients with a high SE and large minimum pupil size (minimum pupil ≥4 mm) suffered more disability glare than those with a low SE and small minimum pupil size.

Comparing aspheric ablation profile with standard corneal ablation for correction of myopia and myopic astigmatism, a contralateral eye study

The purpose of this study is to compare visual outcomes of myopic refractive surgery, using tissue saving (TS), a standard ablation profile by a Technolas 217z100, and aberration smart ablation (ASA), an aspheric algorithm by a MEL 80 excimer laser in two eyes of one patient. In this prospective interventional paired-eye controlled study, a total of 100 eyes of 50 participants with myopia with or without astigmatism underwent thin-flap Femto-LASIK, using a Femto LDV femtosecond laser (Ziemer Ophthalmic Systems AG, Port, Switzerland). For each patient, one eye was randomly treated with tissue-saving algorithm (TS group) by the Technolas 217z100 excimer laser and the other eye was treated with optimized smart ablation profile (ASA group) by the MEL 80 excimer laser. Outcome measures were uncorrected distance visual acuities (UDVAs), corrected distance visual acuities (CDVAs), manifest refraction, higher-order aberrations (HOAs), contrast sensitivity, and patient satisfaction 12 months after surgery. At 12 months postoperative, "45 subjects returned with mean" UDVA was - 0.02 ± 0.08 Logarithm of mean angle of resolution (LogMAR) for TS group and - 0.02 ± 0.09 LogMAR for ASA group (P = 0.91). Of the TS eyes, 42/45 (93.3%) and 32/45 (71.1%) were within ± 0.5 D and ± 0.25 D of target refraction, respectively, and of the ASA eyes, 41/45 (91.1%) and 30/45 (66.6%) were within ± 0.5 D and ± 0.25 D of target refraction, respectively. No statistically significant differences were observed between groups in HOAs changes and contrast sensitivity function. Aspheric and non-aspheric LASIKs using the two different excimer lasers provide similar results in myopic and myopic astigmatism patients.

Q-optimized Algorithms: Theoretical Analysis of Factors Influencing Visual Quality After Myopic Corneal Refractive Surgery

PURPOSE

To model the effect of pupil size, optical zone, and initial myopic level on the retinal image quality after Q-optimized myopic corneal refractive surgery.

METHODS

Different Q-optimized and paraxial Munnerlyn algorithms were tested using a schematic myopic eye model to analyze the optical quality of the final retinal image for initial myopic errors from -1.00 to -7.00 diopters (D). Different optical zones (5.5, 6, and 6.5 mm in diameter) and two pupil diameters (5 and 7 mm, mesopic-scotopic conditions) were included in the comparison. Modulation transfer function (MTF) and area under the MTF from 0 to 60 cycles per degree (MTFa) were calculated by ray tracing to evaluate this retinal image quality.

RESULTS

The Q-optimized algorithm with Q = -0.45 provided the highest MTF and MTFa results for myopic corrections less than -5.00 D. For refractive errors greater than -5.00 D, Q = -0.26 provided the highest MTF and MTFa results.

CONCLUSIONS

Q-optimized algorithms improve the visual outcomes with respect to the paraxial Munnerlyn algorithm for myopic corneal surgery. The results show that the Q value that optimizes the results of the Q-optimized algorithm depends on the degree of myopia to correct and the size of the pupil. [J Refract Surg. 2016;32(9):612-617.].

Refractive Surgery: Malpractice Litigation Outcomes

PURPOSE

To review data on malpractice claims related to refractive surgery to identify common allegations and injuries and financial outcomes.

METHODS

The WestlawNext database was reviewed for all malpractice lawsuits/settlements related to refractive eye surgery. Data evaluated included patient demographics, type of operation performed, plaintiff allegation, nature of injury, and litigation outcomes.

RESULTS

A total of 167 cases met the inclusion criteria, of which 108 cases (64.7%) were found to be favorable and 59 cases (35.3%) unfavorable to the defendant. A total of 141 cases were tried by a jury with 108 cases (76.4%) favorable and 33 cases (23.6%) unfavorable to the defendant. Laser in situ keratomileusis was performed in 127 cases (76%). The most common allegations were negligence in treatment or surgery in 127 cases (76%) and lack of informed consent in 83 cases (49.7%). For all cases, the need for future surgery (P = 0.0001) and surgery resulting in keratoconus (P = 0.05) were more likely to favor the plaintiff. In jury verdict decisions, cases in which failure to diagnose a preoperative condition was alleged favored the defendant (P = 0.03), whereas machine malfunction (P = 0.05) favored the plaintiff. After adjustment for inflation, the overall mean award was $1,287,872. Jury verdicts and settlements led to mean awards of $1,604,801 and $826,883, respectively.

CONCLUSIONS

Malpractice litigation in refractive surgery tends to favor the defendant. However, large awards and settlements were given in cases that were favorable to the plaintiff. The need for future surgery and surgery leading to keratoconus increased the chance of an unfavorable outcome.

Quality of vision after wavefront-guided laser in situ keratomileusis or photorefractive keratectomy: Contralateral eye evaluation

PURPOSE

To compare quality of vision between laser in situ keratomileusis (LASIK) and 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 1 eye treated with LASIK and the other with PRK. Eyes were randomized for dominance. The patients completed a questionnaire assessing quality of vision in each eye at the initial visit and 1, 3, 6, and 12 months postoperatively.

RESULTS

The study comprised 34 patients (68 eyes). There were no initial differences in quality of vision. The PRK eyes had worse clarity during the day (P = .001) and at night (P = .001), worse overall vision (P = .024), more vision fluctuation (P = .006), and more double vision (P = .022) at 1 month. Eyes with higher preoperative higher-order aberrations (HOAs) having PRK had worse clarity during the day and at night (P = .006 and P = .012, respectively) and more vision fluctuation (P = .041); PRK eyes with lower preoperative HOAs had worse daytime clarity (P = .036) at 1 month. After 1 month, there were no differences.

CONCLUSIONS

The quality of vision was better in LASIK eyes after 1 month. At subsequent visits, there was no significant difference in quality of vision.

Quality of Vision After Wavefront-Guided or Wavefront-Optimized LASIK: A Prospective Randomized Contralateral Eye Study

PURPOSE

To compare the effect of wavefront-guided and wavefront-optimized LASIK using different laser platforms on subjective quality of vision.

METHODS

The dominant eyes of 55 participants with myopia were randomized to receive either wavefront-guided LASIK treatment by the VISX Star S4 IR Custom-Vue excimer laser system (Abbott Medical Optics, Inc., Santa Clara, CA) or wavefront-optimized treatment by the WaveLight Allegretto Wave Eye-Q 400-Hz excimer laser system (Alcon Laboratories, Inc., Fort Worth, TX), whereas the fellow eye had the alternate laser treatment. Patients completed a questionnaire assessing quality of vision and visual symptoms (daytime and nighttime glare, daytime and nighttime clarity, halos, haze, fluctuating vision, and double vision) preoperatively and at postoperative months 1, 3, 6, and 12.

RESULTS

At 3, 6, and 12 months postoperatively, there was no significant difference in any individual symptom between the wavefront-guided and wavefront-optimized groups, although at 12 months wavefront-guided eyes trended toward having more excellent vision (wavefront-guided vs wavefront-optimized; 2.26 vs 2.43; P = .039). In the subgroup of patients with preoperative root mean square (RMS) higher order aberrations (HOAs) less than 0.3 µm in both eyes, the wavefront-optimized group demonstrated a trend toward worsened nighttime clarity (P = .009), daytime clarity (P = .015), and fluctuating vision (P = .046), and less excellent vision (P = .009) at 12 months.

CONCLUSIONS

Twelve months after surgery, most patients' self-reported visual symptoms were similar in eyes receiving wavefront-guided or wavefront-optimized LASIK. In general, 36% of patients preferred wavefront-guided LASIK, 19% preferred wavefront-optimized LASIK, and 45% had no preference at 12 months. The wavefront-guided preference was more pronounced in patients with lower baseline HOAs (RMS < 0.3 µm).

Comparison of Visual Quality After SMILE and LASEK for Mild to Moderate Myopia

PURPOSE

To compare the objective and subjective quality of vision after femtosecond laser-assisted small incision lenticule extraction (SMILE) and laser-assisted subepithelial keratomileusis (LASEK) for mild to moderate myopia.

METHODS

This prospective, comparative study included 65 eyes of 33 patients in the SMILE group, with a mean spherical equivalent (SE) of -4.16 ± 0.82 diopters, and 50 eyes of 25 patients in the LASEK group, with a mean SE of -3.81 ± 0.97 diopters. Visual acuity, corneal topography, contrast sensitivity, and wavefront aberrations were recorded preoperatively and compared with postoperative measurements. A quality of vision questionnaire was scored and analyzed 3 months postoperatively.

RESULTS

Three months postoperatively, the SMILE group had fewer (P < .05) higher-order aberrations (HOAs) (0.390 ± 0.175 µm), including spherical aberration (SA) (0.262 ± 0.242 µm), than the LASEK group (HOAs = 0.479 ± 0.148 µm, SA = 0.576 ± 0.287 µm, trefoil = 0.465 ± 0.248 µm). There was no significant difference in the amount of coma and trefoil between the two groups after surgery. Analysis of the scores of glare and halos in the quality of vision questionnaire revealed that SMILE (night glare = 1.25 ± 1.22, halos = 0.97 ± 1.12) provided a better quality of vision (P < .05) than LASEK (night glare = 2.32 ± 1.99, halos = 1.96 ± 1.77). The two groups demonstrated no significant difference in contrast sensitivity 3 months postoperatively. No vision-threatening complications were noted at any stage in either group.

CONCLUSIONS

Both SMILE and LASEK are safe and effective surgical procedures in the correction of myopia. SMILE has a lower induction rate of HOAs and a higher degree of patient satisfaction than LASEK at 3 months postoperatively.

Effect of postoperative keratometry on quality of vision in the postoperative period after myopic wavefront-guided laser in situ keratomileusis

PURPOSE

To determine whether postoperative keratometry is a predictor of patient-reported satisfaction and night-vision phenomena after wavefront-guided myopic laser in situ keratomileusis (LASIK).

SETTING

Optical Express, Glasgow, United Kingdom.

DESIGN

Retrospective case series.

METHODS

Myopic eyes treated with wavefront-guided LASIK were analyzed in this study. All patients completed pre-operative and 1-month postoperative questionnaires, in which the satisfaction with visual outcomes and pre-operative and postoperative night-vision symptoms (glare, halos, starburst, ghosting/double-vision) were rated. Multivariate regression analysis was performed to determine factors associated with questionnaire outcomes.

RESULTS

This study evaluated 8672 myopic eyes of 4602 patients. The mean pre-operative manifest spherical equivalent was -3.72 diopters (D) ± 2.00 (SD) (range -0.50 to -11.00 D) and the mean pre-operative keratometry (K) value was 43.64 ± 1.43 D (38.38 to 49.00). At 1 month after surgery, 93.7% and 99.1% of eyes were within 0.50 D and 1.00 D of emmetropia, and 94.6% and 98.3% of eyes achieved monocular and binocular uncorrected-distance visual acuity(UDVA) of 20/20 or better, respectively. There were 48.7% of eyes that had the flat corneal meridian (minimum K) of 40.0 D or less. Although postoperative keratometry was a significant predictor of patient-reported satisfaction and the change in halo reports in the regression analysis, its relative contribution was very low and accounted for less than 0.50% of the variance explained by either model. Postoperative keratometry was not a significant predictor of a change in reports of glare, starburst, and ghosting or double vision.

CONCLUSION

In this large cohort of patients, postoperative keratometry played a minimal and clinically insignificant role in predicting post-LASIK halo visual phenomena and patient-reported satisfaction.

FINANCIAL DISCLOSURE

Dr. Schallhorn is a consultant to Abbott Medical Optics and Zeiss and a Global Medical Director for Optical Express. None of the other authors have a financial or proprietary interest in the products and materials presented in this paper.

Screening of refractive surgery candidates for LASIK and PRK

PURPOSE

The aim of this study was to evaluate exclusion criteria in screening patients for refractive surgery.

METHODS

Patients screened for initial refractive surgery by a single surgeon at the Cole Eye Institute (Cleveland Clinic) between 2007 and 2012 were reviewed. Exclusion criteria for patients who were not offered refractive surgery based on history and/or examination parameters were analyzed.

RESULTS

A total of 1067 refractive candidates were enrolled in the study. Five hundred nineteen (48.6%) were male and 548 (51.4%) were female with a mean age of 39 ± 12 (range, 17-78) years. Refractive surgery was performed in 657 (61.6%) patients, and photorefractive keratectomy was considered the best option for 106 (9.9%) patients. Four hundred ten (38.4%) of all screened patients did not have refractive surgery, and 134 of these patients (12.6%) were considered to have contraindications for laser in situ keratomileusis and photorefractive keratectomy. Among the excluded patients, 69 (51.5%) were male and 65 (48.5%) were female with a mean age of 40 ± 14 (range, 18-78) years. Abnormal corneal topography (34.3%) and low or insufficient corneal thickness (23.1%) were the most common reasons for exclusion. High myopia (10.5%) and (insipient or definite) cataract (9.7%) were also common reasons for exclusion. Other common factors for exclusion were high hyperopia (3.7%), need to wear reading glasses after surgery (3.7%), and severe dry eye unresponsive to treatment (3.7%).

CONCLUSIONS

Abnormal corneal topography and low, or insufficient, corneal thickness remain the most common exclusion factors for corneal refractive surgery. Factors such as cataract, too high of correction, and severe dry eye are also common reasons for exclusion of patients.

One-year eye-to-eye comparison of wavefront-guided versus wavefront-optimized laser in situ keratomileusis in hyperopes

Background

To compare wavefront (WF)-guided and WF-optimized laser in situ keratomileusis (LASIK) in hyperopes with respect to the parameters of safety, efficacy, predictability, refractive error, uncorrected distance visual acuity, corrected distance visual acuity, contrast sensitivity, and higher order aberrations.

Methods

Twenty-two eyes of eleven participants with hyperopia with or without astigmatism were prospectively randomized to receive WF-guided LASIK with the VISX CustomVue S4 IR or WF-optimized LASIK with the WaveLight Allegretto Eye-Q 400 Hz. LASIK flaps were created using the 150-kHz IntraLase iFS. Evaluations included measurement of uncorrected distance visual acuity, corrected distance visual acuity, <5% and <25% contrast sensitivity, and WF aberrometry. Patients also completed a questionnaire detailing symptoms on a quantitative grading scale.

Results

There were no statistically significant differences between the groups for any of the variables studied after 12 months of follow-up (all P>0.05).

Conclusion

This comparative case series of 11 subjects with hyperopia showed that WF-guided and WF-optimized LASIK had similar clinical outcomes at 12 months.

Prospective randomized contralateral eye evaluation of subjective quality of vision after wavefront-guided or wavefront- optimized photorefractive keratectomy

PURPOSE

To compare the effect of wavefront-guided (WFG) and wavefront-optimized (WFO) photorefractive keratectomy (PRK) on patient perceived quality of vision.

METHODS

Seventy-one patients (142 eyes) were enrolled in this prospective, randomized, fellow eye controlled study. One eye was randomized to undergo WFG PRK treatment by the AMO Visx CustomVue S4 IR excimer laser system (Abbott Medical Optics, Inc., Santa Clara, CA) and the fellow eye received WFO PRK treatment by the Alcon Allegretto Wave Eye-Q 400 Hz excimer laser system (Alcon Laboratories, Inc., Fort Worth, TX). Patients answered questionnaires on their visual symptoms and quality of vision preoperatively and at 1, 3, 6, and 12 months after surgery.

RESULTS

Patients in both groups reported better vision compared to baseline from 3 months onward (mean change in score of 1.56 to 2.51 in the WFO group and 1.54 to 2.28 in the WFG group, P ⩽ .003). Both groups experienced less nighttime glare from 6 months onward (P ⩽ .030). Halos, double vision, and visual clarity were initially worse (P ⩽ .025) but not significantly different after 1 month. Haze and fluctuating vision resolved after 3 months. Visual symptoms were similar between the two groups at all times (P ⩾ .059) except at 6 months, when patients felt their WFG eyes had more excellent vision (P = .029). A composite of all symptoms was also similar between the groups until 12 months when patients had fewer symptoms in their WFO eye (P = .044).

CONCLUSIONS

One year after surgery, patient self-reported visual symptoms were not significantly different in eyes receiving WFG or WFO PRK. However, the average of all symptoms was lower in eyes receiving wavefront-optimized treatment.

Pupil size and LASIK: a review

PURPOSE

To provide a literature review on the evidence both for and against pupil size as an independent predictor of adverse visual outcomes after LASIK.

METHODS

Peer-reviewed publications on the effect of pupil size on LASIK outcomes since 2002 are reviewed. Particular attention was paid to the following attributes of each publication: type of study, number of patients or eyes, mean age, mean level of myopia, mean pupil size, testing conditions, ablation zone diameter, presence or absence of blend zones, and mean follow-up period.

RESULTS

Among the 19 studies examined, none correlates a persistent relationship between pupil size and night vision complaints (NVCs) beyond 3 months when LASIK was performed with a 6.0-mm optical zone or larger ablation. The studies that did explicitly determine a correlation either included some or all patients with ablation zones smaller than 6.0 mm or did not specify ablation diameter at all. Among the studies that had drawn more mixed conclusions, the studies either covered short follow-up intervals (1 to 3 months) or showed a progressive improvement in NVCs over time in a relatively small patient cohort.

CONCLUSIONS

As keratorefractive technology continues to evolve, the role of pupil size warrants further investigation; however, based on the literature reviewed herein, modern LASIK has negated the role of the low light pupil in predicting adverse visual outcomes after LASIK outside of the early postoperative period.

Risk factors associated with night vision disturbances after phakic intraocular lens implantation

PURPOSE

To investigate the incidence and severity of night vision disturbances after implantable collamer lens surgery and to analyze the risk factors.

DESIGN

Retrospective, noncomparative study.

METHODS

Medical charts from 50 eyes of 25 patients who underwent implantable collamer lens implantation were retrospectively reviewed. The incidence and severity of night vision disturbances were evaluated using questionnaires administered 6 months after surgery. Univariate simple and multiple logistic regression analyses were used to detect risk factors associated with postoperative night vision disturbances. Potential risk factors included in the analysis were keratometric value, anterior chamber depth, postoperative residual refractive error, higher-order aberrations, preoperative and postoperative mesopic pupil size, the difference between preoperative and postoperative mesopic pupil size, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, white-to-white diameter, sulcus-to-sulcus diameter, and postoperative implantable collamer lens vaulting. The power, size, optic zone diameter, and toricity of the implantable collamer lens were also included as variables.

RESULTS

The incidence of night vision disturbances was 34.0% for halos and 26.0% for glare. Halos were found to be significantly related to the difference between mesopic pupil size and implantable collamer lens optic zone diameter (P = .013), white-to-white diameter of the cornea (P = .028), and implantable collamer lens optic zone diameter (P = .030). For glare, toricity of the implantable collamer lens was revealed as a significant risk factor (P = .047).

CONCLUSIONS

Although not severe, the incidence of night vision disturbances after implantable collamer lens implantation was not negligible. Possible risk factors for night vision disturbances include implantable collamer lens optic zone diameter, the difference between mesopic pupil size and implantable collamer lens optic zone diameter, and white-to-white diameter of the cornea for causing halos, and the toricity of the implantable collamer lens for causing glare.

[Avoidance and management of complications in laser in situ keratomileusis]

Laser in situ keratomileusis (LASIK) is now considered to be a safe and effective standard procedure for surgical correction of low to medium ametropia. Nevertheless, as in any other surgical intervention complex courses may occur in single rare cases. Possible complications include, but are not limited to, optically effective errors, such as too small or decentered optical zones as well as intraoperative flap cutting errors and postoperative complications, such as inflammation (e.g. diffuse lamellar keratitis, DLK), epithelial or flap folds, epithelial ingrowths or iatrogenic ectasia. Compliance to standards for indications and treatment based on the current scientific knowledge can significantly reduce the occurrence of complications. These standards include adjustment of the optical zone to the mesopic pupil diameter, the application of state of the art eye trackers, careful performance of intraoperative and postoperative procedures by a surgeon experienced in the entire spectrum of ocular surgery, the possibility of treating complications directly on occurrence and, last but not least, conservative patient selection and choice of treatment.

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.

One-year outcomes from a prospective, randomized, eye-to-eye comparison of wavefront-guided and wavefront-optimized LASIK in myopes

OBJECTIVE

To compare wavefront (WF)-guided and WF-optimized LASIK in myopes.

DESIGN

Prospective, randomized, eye-to-eye study.

PARTICIPANTS

A total of 72 eyes of 36 participants with myopia with or without astigmatism.

METHODS

Participants were randomized to receive WF-guided or WF-optimized LASIK with the WaveLight Allegretto Eye-Q 400-Hz excimer laser platform (Alcon, Inc., Hüenberg, Switzerland). LASIK flaps were created using the 150-kHz IntraLase iFS (Abbott Medical Optics, Santa Ana, CA). Evaluations included measurement of uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), <5% and <25% contrast sensitivity, and WF aberrometry. Patients also completed a validated questionnaire detailing symptoms on a quantitative scale.

MAIN OUTCOME MEASURES

Safety, efficacy, predictability, refractive error, UDVA, CDVA, contrast sensitivity, and higher-order aberrations (HOAs).

RESULTS

The frequency with which the WF-guided and WF-optimized groups achieved postoperative UDVA of ≥ 20/16 or ≥ 20/20 and the frequency with which the groups lost 1 or 2 or more lines or maintained their preoperative CDVA were not statistically different from each other (all P > 0.05). The frequency with which the WF-guided group attained a refractive error within ± 0.25 diopters of emmetropia was higher than in the WF-optimized group (67.6%, 95% confidence interval [CI], 50.4-84.8 vs. 41.2%, 95% CI, 23.2-59.2; P = 0.03). The WF-guided group's mean UDVA was better than the WF-optimized group's UDVA by approximately 1 Early Treatment Diabetic Retinopathy Study line (-0.17 ± 0.11 logarithm of the minimum angle of resolution [logMAR], slightly <20/12 Snellen vs. -0.13 ± 0.12, slightly >20/16; P = 0.05). There were no statistically significant differences in contrast sensitivity, astigmatism, coma, or higher-order root mean square error between the groups (all P > 0.05), but the WF-guided group had less trefoil compared with the WF-optimized group (0.14 ± 0.07 vs. 0.20 ± 0.09; P < 0.01). There were no statistically significant differences in subjective parameters between the groups (all P > 0.05).

CONCLUSIONS

Wavefront-guided and WF-optimized LASIK using the Alcon WaveLight Allegretto Eye-Q 400-Hz excimer laser platform provide similar results in myopic patients; however, the WF-guided approach may yield small gains in visual acuity, predictability, and HOAs.

Theoretical analysis of the effect of pupil size, initial myopic level, and optical zone on quality of vision after corneal refractive surgery

PURPOSE

To analyze the theoretical effect that pupil size, optical zone, and initial myopic level have on the final retinal image after corneal refractive surgery.

METHODS

A schematic myopic eye model corrected by the Munnerlyn formula was used to analyze the optical quality of the final retinal image. Root-mean-square radius spot and modulation transfer function were cal- culated by ray tracing to evaluate retinal image quality.

RESULTS

Pupil size had a negative effect on the retinal image only when it was greater than the diameter of the optical zone. In addition, the greater the initial myopic level, the more the pupil size affected image quality. Thus, a clear dependence exists between the initial myopic level and effect that the pupil size can have on the retinal image after laser refractive surgery.

CONCLUSIONS

Pupil size may be a risk factor for night vision disturbances, but only when it is larger than the theoretical optical zones utilized in this study. Its effect depends not only on the optical zone size, but also on the initial "myopic level. Therefore, this relationship should be taken into account during patient selection for refractive surgery

Mesopic pupil size in a refractive surgery population (13,959 eyes)

PURPOSE

To evaluate factors that may affect mesopic pupil size in refractive surgery candidates.

METHODS

Medical records of 13,959 eyes of 13,959 refractive surgery candidates were reviewed, and one eye per subject was selected randomly for statistical analysis. Detailed ophthalmological examination data were obtained from medical records. Preoperative measurements included uncorrected distance visual acuity, corrected distance visual acuity, manifest and cycloplegic refraction, topography, slit lamp examination, and funduscopy. Mesopic pupil size measurements were performed with Colvard pupillometer. Relationship between mesopic pupil size and age, gender, refractive state, average keratometry, and pachymetry (thinnest point) were analyzed by means of ANOVA (+ANCOVA) and multivariate regression analyses.

RESULTS

Overall mesopic pupil size was 6.45 ± 0.82 mm, and mean age was 36.07 years. Mesopic pupil size was 5.96 ± 0.8 mm in hyperopic astigmatism, 6.36 ± 0.83 mm in high astigmatism, and 6.51 ± 0.8 mm in myopic astigmatism. The difference in mesopic pupil size between all refractive subgroups was statistically significant (p < 0.001). Age revealed the strongest correlation (r = -0.405, p < 0.001) with mesopic pupil size. Spherical equivalent showed a moderate correlation (r = -0.136), whereas keratometry (r = -0.064) and pachymetry (r = -0.057) had a weak correlation with mesopic pupil size. No statistically significant difference in mesopic pupil size was noted regarding gender and ocular side. The sum of all analyzed factors (age, refractive state, keratometry, and pachymetry) can only predict the expected pupil size in <20% (R = 0.179, p < 0.001).

CONCLUSIONS

Our analysis confirmed that age and refractive state are determinative factors on mesopic pupil size. Average keratometry and minimal pachymetry exhibited a statistically significant, but clinically insignificant, impact on mesopic pupil size.

Visual outcome after correcting the refractive error of large pupil patients with wavefront-guided ablation

Purpose

To investigate the efficacy and predictability of wavefront-guided laser in situ keratomileusis (LASIK) treatments using the iris registration (IR) technology for the correction of refractive errors in patients with large pupils.

Setting

Horus Vision Correction Center, Alexandria, Egypt.

Methods

Prospective noncomparative study including a total of 52 eyes of 30 consecutive laser refractive correction candidates with large mesopic pupil diameters and myopia or myopic astigmatism. Wavefront-guided LASIK was performed in all cases using the VISX STAR S4 IR excimer laser platform. Visual, refractive, aberrometric and mesopic contrast sensitivity (CS) outcomes were evaluated during a 6-month follow-up.

Results

Mean mesopic pupil diameter ranged from 8.0 mm to 9.4 mm. A significant improvement in uncorrected distance visual acuity (UCDVA) (P < 0.01) was found postoperatively, which was consistent with a significant refractive correction (P < 0.01). No significant change was detected in corrected distance visual acuity (CDVA) (P = 0.11). Efficacy index (the ratio of postoperative UCDVA to preoperative CDVA) and safety index (the ratio of postoperative CDVA to preoperative CDVA) were calculated. Mean efficacy and safety indices were 1.06 ± 0.33 and 1.05 ± 0.18, respectively, and 92.31% of eyes had a postoperative spherical equivalent within ±0.50 diopters (D). Manifest refractive spherical equivalent improved significantly (P < 0.05) from a preoperative level of −3.1 ± 1.6 D (range −6.6 to 0 D) to −0.1 ± 0.2 D (range −1.3 to 0.1 D) at 6 months postoperative. No significant changes were found in mesopic CS (P ≥ 0.08), except CS for three cycles/degree, which improved significantly (P = 0.02). Magnitudes of primary coma and trefoil did not change significantly (P ≥ 0.34), with a small but statistically significant increase in primary spherical aberration.

Conclusion

Wavefront-guided LASIK provides an effective correction of low to moderate myopia or myopic astigmatism in large pupil patients without deterioration of visual quality.

Satisfaction level of physicians who have undergone corneal refractive surgery

Purpose

To evaluate the levels of satisfaction among physicians who have undergone corneal refractive surgery.

Methods

This study included 212 eyes of 107 consecutive patients who underwent laser in situ keratomileusis or laser sub-epithelial keratomileusis surgery. Patients were divided into two groups: one group of physicians and one group of other healthcare workers (HCWs). The physicians' group was also subdivided into two different groups: surgeons or doctors using microscopes and medical physicians. The main outcome measures were scale scores obtained by using the Visual Function Index-14 questionnaires; uncorrected distance visual acuity (UDVA), residual spherical equivalent (SE), optical zone diameter, and residual corneal thickness were also compared between the groups.

Results

No significant differences in preoperative parameters, with the exception of the ratio of types of refractive surgery, were noted between the physicians and the HCWs group. Additionally, no differences between the groups were noted in the postoperative UDVA, residual SE, optical zone diameter, residual corneal thickness, and level of satisfaction. When comparing the two subgroups of physicians, the differences in satisfaction rates were not statistically significant, even in terms of the performance of delicate manual work.

Conclusions

No statistically significant differences in the clinical outcomes and satisfaction scores were detected after surgery between the physicians and HCWs groups, nor were any significant differences detected between the surgeons and medical physicians groups. Corneal refractive surgery can conceivably be recommended even for physicians who perform intensive near vision-dependent activities and delicate operations.

Changing perspective of reasons for not performing laser-assisted in situ keratomileusis among candidates in a university eye clinic

BACKGROUND

The aim was to retrospectively analyse the reasons for not performing laser-assisted in situ keratomileusis (LASIK) surgery among refractive surgery candidates at a university eye clinic.

METHODS

Case records of patients who presented to a university eye clinic between June 2005 and June 2010 for consideration for LASIK surgery were examined. Cases that did not undergo LASIK were selected for analysis. Reasons for not performing surgery in these cases were analysed.

RESULTS

In total, 552 patients requested LASIK between July 2005 and June 2010 and 377 (68.3 per cent) of them received refractive surgery. Among 175 (31.7 per cent) patients who did not get LASIK, 62 (35.4 per cent) were male and 113 (64.6 per cent) were female, with a mean age at presentation of 36.4 ± 9.3 years (range: 19 to 78 years). The most common reasons for not offering LASIK were low corneal thickness (28.6 per cent), high myopia (15.4 per cent), large pupil (8.0 per cent) and keratoconus (7.4 per cent). Overall, 39 patients (22.3 per cent) changed their mind after their initial consultations with surgeons. The prevalence of rejection of LASIK decreased from 44.1 per cent between July 2005 and June 2006 to 3.5 per cent between July 2009 and June 2010.

CONCLUSIONS

Reasons for not performing refractive surgery are quite diverse. Inadequate corneal thickness and change of mind after initial consultation were the most common reasons in the present study. There was a marked change in magnitude and trend of reasons for not performing LASIK over the study period. Further studies from settings other than university hospitals would be beneficial to compare the trend in patient selection.

Comparison of 3 pupillometers for determining scotopic pupil diameter

PURPOSE

The pupil diameter under low ambient illumination is diagnostically valuable for refractive surgery. The aim of study was to compare the NeurOptics® Pupillometer, Sirius®, and Ocular Wavefront Analyser® in determining scotopic pupil diameter.

MATERIALS AND METHODS

A total of 96 eyes of 48 subjects were included. The scotopic pupil size was measured with 3 instruments and the measurements repeated following instillations of 1% cyclopentolate. Agreement between the instruments was assessed.

RESULTS

The mean measurement obtained by Sirius was significantly larger than Ocular Wavefront Analyser and NeurOptics. The Ocular Wavefront Analyser measured significantly smaller than the others. The mean cycloplegic pupillary diameters (7.73±0.70 mm with NeurOptics, 7.42±0.45 mm with Ocular Wavefront Analyser, and 8.06±0.76 mm with Sirius) were significantly different obtained by 3 instruments (p<0.001, for each; one-way analysis of variance and paired t tests).

CONCLUSIONS

The differences between measured pupil diameters with or without cycloplegia obtained by the NeurOptics, Sirius, and Ocular Wavefront Analyser were significant and have unacceptable levels of disagreement. These results may not be related to illumination and accommodation only, but also to measurement algorithms and technical differences of the devices.