Higher order aberrations and visual function in a young Asian population of high myopes.

Purpose: To examine the associations between higher order aberrations (HOAs), visual performance, demographics, and ocular characteristics in a young Asian population with high myopia. Methods: This was a retrospective review of military pre-enlistees conducted between March 2014 to September 2018. Visual acuity and contrast sensitivity were tested under photopic, mesopic and simulated night conditions. Ocular, corneal and internal HOAs were measured with a Hartmann-Shack wavefront aberrometer (KR-1W, Topcon Co., Tokyo, Japan). Results: 522 eyes of 263 consecutive subjects with severe high myopia (defined as spherical equivalent refraction [SER] ≤ -10.00D) in at least one eye, and high myopia (SER ≤ -6.00D) in the fellow eye, [mean (SD) SER -11.85 (2.03D)] were analysed. The mean (SD) age of subjects was 18.5 (1.6) years. Chinese eyes had significantly greater internal total HOA root-mean-square (RMS) compared to Malay eyes [mean difference (SD) 0.0246 (0.007) µm, p < 0.001). More negative SER was associated with greater ocular total HOA (p = 0.038), primary coma (p = 0.003) and tetrafoil (p = 0.025) RMS, as well as more positive ocular (p = 0.003) and internal primary spherical aberration (p = 0.009). Greater ocular total HOAs was associated with reduced visual acuity in simulated night conditions and low contrast, decreased contrast sensitivity under mesopic and simulated night conditions (all p < 0.05). Conclusions: Greater HOAs were associated with Chinese ethnicity and more negative SER in a young Asian population with high myopia. Greater HOAs were associated with poorer visual performance in low luminance and reduced contrast conditions.

Refractive outcomes, corneal haze and endothelial cell loss after myopic photorefractive keratectomy in an Asian population: The Singapore Armed Forces' experience.

IMPORTANCE: This study reports outcomes of myopic photorefractive keratectomy (PRK) in a mainly ethnic Chinese population in Singapore. BACKGROUND: To assess the incidence and associations of corneal haze and endothelial cell count (ECC) loss up to 12 months after PRK. DESIGN: This was a retrospective case series conducted in a tertiary eye centre. PARTICIPANTS: A total of 158 patients (309 eyes) with a mean age of 22.1 ± 3.4 years were included. The majority was Chinese (97.4%) and male (97.4%). Mean preoperative spherical equivalent was -3.33 ± 1.15 D. METHODS: Eyes were categorized based on postoperative haze severity. A multivariate analysis adjusting for age and use of intraoperative mitomycin-C (MMC), preoperative sphere and cylinder was performed. MAIN OUTCOME MEASURES: Refractive outcomes and corneal haze 3 and 12 months after PRK were assessed. ECC measurements were obtained before PRK and at variable periods postoperatively. RESULTS: At 12 months, overall efficacy index was 0.98, and safety index was 1.09. Eight (2.5%) eyes underwent enhancement surgery. An analysis was performed on 295 eyes that did not undergo enhancement and had complete clinical data, which demonstrated a decrease in the incidence of haze from 38.2% at 3 months to 9.3% at 12 months. Higher myopia was associated with increased haze severity at 3 months (OR, 1.36; P = .005). Higher astigmatism was associated with increased haze severity at 3 (OR, 1.65; P = .018) and 12 months (OR, 2.32; P = .015). Intraoperative MMC was not associated with haze severity or ECC loss. CONCLUSIONS AND RELEVANCE: Myopia and astigmatism were associated with increased corneal haze severity. Intraoperative MMC did not accelerate ECC loss. Overall, PRK is effective, predictable and safe in Asian eyes.

Peripheral retinal changes in highly myopic young Asian eyes.

PURPOSE: To determine the type and prevalence of peripheral retinal changes and its relationship with axial length (AL) in a population of young Asian adult males. METHODS: This was a cross-sectional study of male subjects aged between 19 and 25 years old. High myopes [spherical equivalent refraction, (SER) < -6.00 D] were recruited and underwent further ocular investigations including dilated retinal photography and binocular indirect ophthalmoscopy by two trained ophthalmologists. The frequency of peripheral retinal changes within high myopes was correlated with axial length and also compared with a group of emmetropes (SER between -0.50 D and +1.00 D). RESULTS: A total of 593 high myopes and 156 emmetropes were recruited. White without pressure (WWOP; n = 458, 46.5%) and lattice degeneration (LD; n = 109, 14.6%) were the commonest findings, and their prevalence was significantly higher among high myopes (LD, 16.9% versus 5.8%; WWOP, 57.2% versus 5.8%; both p < 0.001). Among high myopes, temporal LD was more common (71%) and 35% had more than one area in the same eye. Increasing AL was associated with LD (odds ratio 1.28, p = 0.01) and retinal holes (odd's ratio 1.44, p = 0.02) on multivariate analysis. CONCLUSION: White without pressure (WWOP) and LD were the commonest peripheral retinal changes. One-third of high myopes with LD had more than one area in the same eye. Increasing AL was associated with LD and retinal holes. Studies in older adults should be conducted to develop clinical guidelines for the management of high myopes.

Relationship between Myopia Severity and Macular Retinal Thickness on Visual Performance under Different Lighting Conditions.

OBJECTIVE: To evaluate the relationship between both spherical equivalent (SE) and retinal thickness (RT) on best-corrected visual acuity (BCVA) among young Asian adult men under photopic, mesopic, and simulated night-vision goggle (NVG) lighting conditions. DESIGN: Community-based cross-sectional study. PARTICIPANTS: Total of 698 myopic and 148 emmetropic subjects. METHODS: All participants underwent a complete ophthalmic examination and color fundus photography. BCVA and subjective refraction were assessed under standardized photopic, mesopic, and simulated NVG lighting conditions. Retinal thickness in various Early Treatment Diabetic Retinopathy Study (ETDRS) subfields was measured using spectral-domain OCT using a standardized protocol. Univariate and multiple linear regression analyses were performed to assess the relationship between BCVA and both SE and RT. MAIN OUTCOME MEASURES: Relationship between BCVA and both SE and RT. RESULTS: The mean age of all subjects was 21.1 years, with mean SE of -8.44 diopter (D) among the myopic subjects (range, -3.75 D to -23.0 D) and +0.10 among the emmetropic subjects (range, -0.49 D to +1.00 D). BCVA worsened progressively with increasing myopia under all lighting conditions (standardized coefficient -0.581 under photopic conditions, P < 0.001). RT was thickest among participants with LogMAR VA ≤0.00, and became thinner in the groups including those with VA >0.00 to ≤0.10 and >0.10 (mean inner subfield RT: 342.7 µm vs. 338.1 µm vs. 331.0 µm, respectively, P < 0.001) under all lighting conditions. When multiple linear regression was performed, higher degrees of myopia and decreasing RT were associated with reduced BCVA (all P < 0.05). For each diopter increase in myopia, mean BCVA decreased by 0.01 LogMAR in photopic conditions and 0.02 LogMAR in mesopic conditions (both P < 0.001). The mean BCVA reduced by 0.05 LogMAR (P = 0.003) and 0.04 LogMAR (P = 0.037), under photopic and scotopic lighting conditions respectively, for each 100-µm decrease in RT. CONCLUSIONS: Both the severity of myopia and macular RT independently affect visual performance under photopic, mesopic, and simulated NVG conditions.

Risk factors for early-onset corneal haze after photorefractive keratectomy in an Asian population: Outcomes from the Singapore Armed Forces Corneal Refractive Surgery Programme 2006 to 2013.

PURPOSE: To assess the incidence and risk factors for early corneal haze after myopic photorefractive keratectomy (PRK). SETTING: Tertiary eye center, Singapore. DESIGN: Retrospective case series. METHODS: The refractive results and corneal haze severity 3 months after PRK were analyzed. Eyes were categorized into 4 groups based on haze severity. Multivariate ordinal logistic regression analysis adjusting for age, ethnicity, sex, use of intraoperative mitomycin-C (MMC), preoperative sphere, and preoperative cylinder was performed. RESULTS: The study reviewed data from 177 patients (347 eyes) with a mean age of 22.6 years ± 4.1 (SD). The majority of the patients were Chinese (98.3%) and men (98.3%). The mean preoperative spherical equivalent (SE) was -3.34 ± 1.19 diopters (D). One hundred thirty-five eyes (38.9%) had PRK with MMC. Ten eyes (2.9%) had enhancement surgery. The overall efficacy index was 0.88 and the safety index was 1.07. At 3 months, 187 eyes (53.9%) had no haze, 76 eyes (21.9%) had a haze grade of more than 0 and less than 1, 76 eyes (21.9%) had a haze grade of 1 or more and less than 2, and 8 eyes (2.3%) had grade 2 haze. Higher degrees of myopia (odds ratio [OR], 1.36; 95% confidence interval [CI], 1.13-1.63; P = .001) and astigmatism (OR, 1.56; 95% CI, 1.09-2.24; P = .014) were associated with increased severity of corneal haze, whereas older age (OR, 0.94; 95% CI, 0.88-0.99; P = .023) had a protective effect. CONCLUSION: Myopia and astigmatism were associated with increased severity of haze, and older age was protective against early corneal haze development after PRK in an Asian population. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Myopic Maculopathy and Optic Disc Changes in Highly Myopic Young Asian Eyes and Impact on Visual Acuity.

PURPOSE: To determine the prevalence and risk factors of myopic maculopathy and specific optic disc and macular changes in highly myopic eyes of young Asian adults and their impact on visual acuity. DESIGN: Prospective cross-sectional study. METHODS: In total, 593 highly myopic (spherical equivalent refraction [SER] less than -6.00 diopters [D]) and 156 emmetropic (SER between -1.00 and +1.00 D) male participants from a population-based survey were included. All participants underwent standardized medical interviews, ophthalmic examination, and color fundus photographs. These photographs were graded systematically to determine the presence of optic disc and macular lesions. Myopic maculopathy was classified based on the International Classification of Myopic Maculopathy. RESULTS: The mean age was 21.1 ± 1.2 years. The mean SER for the highly myopic and emmetropic group was -8.87 ± 2.11 D and 0.40 ± 0.39 D, respectively (P < .001). Compared to emmetropic eyes, highly myopic eyes were significantly more likely to have optic disc tilt, peripapillary atrophy (PPA), posterior staphyloma, chorioretinal atrophy, and myopic maculopathy (all P < .001). The main findings included PPA (98.3%), disc tilt (22.0%), posterior staphyloma (32.0%), and chorioretinal atrophy (8.3%). Myopic maculopathy was present in 8.3% of highly myopic eyes and was associated with older age (odds ratio [OR] 1.66; 95% CI: 1.22, 2.26), reduced choroidal thickness (OR 0.99; 95% CI: 0.98, 0.99), and increased axial length (AL) (OR 1.52; 95% CI: 1.06, 2.19). The presence of disc tilt, posterior staphyloma, and chorioretinal atrophy were associated with reduced visual acuity. CONCLUSIONS: Our study showed that myopia-related changes of the optic disc and macula were common in highly myopic eyes even at a young age. The risk factors for myopic maculopathy include increased age, longer AL, and reduced choroidal thickness. Some of these changes were associated with reduced central visual function.

Peripapillary choroidal thickness in young Asians with high myopia.

PURPOSE: To describe the topography and predictors of peripapillary choroidal thickness (PPCT) in highly myopic eyes of young, healthy, Asian subjects. METHODS: A total of 870 young male subjects aged 21.63 ± 1.15 years were recruited from the Singapore military. Choroidal imaging was performed using enhanced depth imaging (EDI) spectral-domain optical coherence tomography (SD-OCT). Peripapillary choroidal thickness was manually measured at eight locations around the optic disc. RESULTS: We analyzed 448 subjects with high myopia (defined as spherical equivalent [SE] worse than -6.0 diopters [D]) and 116 with emmetropia (SE > -0.5 and < 0.5 D). The mean SE was -8.52 ± 1.20 D for the high-myopic group, and 0.11 ± 0.24 D for the emmetropic group. The mean peripapillary choroid was significantly thinner (142.62 ± 43.84 µm) in high myopes compared with emmetropes (181.90 ± 46.43 µm, P < 0.001). Likewise, PPCT showed further decrease with increase in degree of myopic refractive error. Distribution of PPCT showed a markedly different pattern in high-myopic eyes (thickest superiorly) and emmetropic eyes (thickest temporally). However, peripapillary choroid in both the groups was thinnest at the inferior location. Among the ocular factors studied, axial length, IOP, presence of posterior staphyloma, and chorioretinal atrophy were the factors significantly associated with PPCT. CONCLUSIONS: Highly myopic eyes have significantly thinner peripapillary choroid and showed different distribution of thickness, compared with emmetropes. Axial length, IOP, and presence of posterior staphyloma and chorioretinal atrophy significantly influence PPCT and should be taken into consideration during clinical interpretation of PPCT measurement.

Choroidal thickness and high myopia: a case-control study of young Chinese men in Singapore.

PURPOSE: To determine the distribution of choroidal thickness (CT) and ocular factors associated with CT in high myopic eyes in comparison with emmetropic eyes of young healthy adults. METHODS: A case-control study of 648 young, male subjects, including 520 high myopes and 128 emmetropes. Choroidal imaging was performed using enhanced depth imaging spectral domain optical coherence tomography. Images were postprocessed using adaptive compensation for quality enhancement. CT was measured at nine locations, including subfovea and 1.5 and 3 mm nasal, temporal, superior and inferior to fovea. RESULTS: The CT at the subfovea was significantly thinner (mean ± standard error: 225.87 ± 5.51 µm) for high myopes compared to emmetropes (375.15 ± 6.58 µm, p < 0.001). Likewise, CT in high myopic group was significantly thinner than emmetropic control group at all locations (p for trend <0.001 for all locations). Distribution of CT showed a markedly different pattern in high myopic eyes (thickest superiorly at 3 mm, 265.97 ± 5.97 µm) and emmetropic eyes (thickest subfoveally, 375.15 ± 6.58 µm). Choroid was thinnest at nasal 3 mm location in both the myopic (108.85 ± 3.97 µm) and emmetropic (238.25 ± 6.72 µm) groups. Among the ocular factors studied, axial length, posterior staphyloma and chorio-retinal atrophy were the significant predictors of CT. CONCLUSIONS: Highly myopic eyes have significantly thinner choroid and showed different distribution pattern, compared to emmetropes. Axial length, posterior staphyloma and chorio-retinal atrophy are the strongest determinants of CT.

Correlation of structural and electrophysiological changes in the retina of young high myopes.

PURPOSE: Despite a high prevalence of myopia among young East Asian adults, there is a lack of data on the myopic retina structure-function relationship in this group. We examined the association between optical coherence tomography (OCT) and electroretinogram (ERG) measurements in highly myopic young Asian adults to provide this information and also determined if OCT can be used as an alternative screening tool to assess retinal function in young myopic adults. METHODS: This was a prospective study comprising young adults aged between 18 and 25 years with spherical equivalent refraction of worse than -6.00 D. A comprehensive ophthalmic examination comprising fundus examination and grading, ocular biometry, time-domain OCT (fovea, macular and retinal nerve fibre layer thickness) and ERG (full field and multifocal) were performed for all the eyes. RESULTS: A total of 32 eyes (mean spherical equivalent ± standard deviation -10.17 ± 1.51 D, mean age 23.8 ± 1.3 years) were included. None of the eyes showed visible myopic retinopathy and the central retina thickness of all eyes was classified as within the normal range. Full-field ERG amplitude and multifocal ERG P1 amplitudes in the outer rings (R3-R5) were, however, inversely associated with axial length. The multifocal ERG P1 amplitudes were also positively correlated with mean retinal nerve fibre layer thickness in R2, 4, 5 rings and outer macular thickness in R 2-5 rings. CONCLUSION: These findings suggest that full field ERG changes may precede fundus and OCT changes in highly myopic young adults. Although there was some correlation between multifocal ERG amplitudes with OCT outer macular and retinal nerve fibre layer thickness, the OCT may not be useful as a retinal function screening tool, being within normal limits in all eyes. Further longitudinal studies are required to determine how the relationship between ERG and OCT will evolve over time.

Differences in prevalence of refractive errors in young Asian males in Singapore between 1996-1997 and 2009-2010.

PURPOSE: To determine the differences in prevalence rates of refractive errors in young Singaporean males over a 13-year period between 1996-1997 and 2009-2010 METHODS: Non-cycloplegic autorefraction data were obtained in a survey of 15,085 young male subjects (mean age 19.5 ± 1.4 years, range 16-25 years) in 1996-1997 using a Nikon NRK-8000 autorefractor. A second survey of 28,908 male subjects (mean age 19.8 ± 1.2 years, range 17-29 years) was conducted in 2009-2010 using a Huvitz MRK-3100 autorefractor. RESULTS: The overall prevalence of myopia (spherical equivalent, SEq, worse than -0.5 diopters, D) was similar in 2009-2010 (81.6%) and 1996-1997 (79.2%; odds ratio 1.38, 95% confidence interval 1.31-1.46; p < 0.001). The prevalence of high myopia (SEq worse than -6.0D) increased from 13.1% in 1996-1997 to 14.7% in 2009-2010 (p < 0.001). The prevalence of refractive astigmatism increased significantly from 41.4% in 1996-1997 to 50.9% in 2009-2010 (p < 0.001). CONCLUSIONS: Our results show that the prevalence of myopia and high myopia remained high and the prevalence of astigmatism increased in young male adults in Singapore over a 13-year period after controlling for age, education and ethnicity.

Photorefractive keratectomy in young Asian aviators with low-moderate myopia.

INTRODUCTION: The high prevalence of myopia among Asians led the Republic of Singapore Air Force (RSAF) to introduce photorefractive keratectomy (PRK) as a means of enlarging its pilot recruitment pool at the end of 2005. This study aims to address the efficacy and safety of PRK performed on young Asian patients with low-moderate myopia, as well as audit the RSAF's corneal refractive surgery (CRS) program. METHODS: This is a retrospective case series of 149 eyes of 76 consecutive patients that underwent PRK as part of the RSAF CRS program over the 5-yr period from 1 January 2006 to 31 December 2010. RESULTS: The median patient age was 21 yr (range, 18-26 yr) and the mean preoperative spherical equivalent (SE) refraction was -3.39 - 1.19 D. Of the patients, 96.1% were men and all were of Asian origin. At the 12-mo follow-up, 98.5% of eyes had an uncorrected distance visual acuity (UDVA) of < or = 0.00 LogMAR, 100.0% of eyes had an SE refraction of within + 0.50 D of intended correction, and 2.300% of eyes had a loss of corrected distance visual acuity (CDVA) of 0.20 LogMAR. The cumulative incidence of retreatments was 6.7% and cumulative incidence of grade II or worse corneal haze requiring retreatment was 6.0%. Refractive stability was achieved at 3 mo postsurgery. CONCLUSION: The results of this study suggest that PRK performed within the context of a stringent and structured CRS program on young Asian eyes with low-moderate myopia is both efficacious and safe, with refractive stability achieved by 3 mo.

Pathologic changes in highly myopic eyes of young males in Singapore.

INTRODUCTION: This study describes the pathologic changes in the retina of a group of young Asian subjects with myopia worse than -10 diopters spherical equivalent (SE) refraction. MATERIALS AND METHODS: The study population consists of 20 male subjects undergoing preemployment screening for public service for a 1-year period from 2009 to 2010. A detailed series of visual tests of function, fundus examination and grading, ocular biometry and posterior segment optical coherence tomography were performed for all eyes. RESULTS: A total of 21 eyes with mean SE of -10.88 diopters, [standard deviation (SD) , 1.28 diopters], and mean age of 21.8 years (SD, 1.3 years) were included. Out of 21 eyes, 17 (81.0%) had beta peripapillary atrophy, 10 (47.6%) had clinically detectable optic disc tilt, 1 (4.8%) had positive T-sign and 18 (85.7%) had retinal tessellation, 4 (19.0%) had posterior vitreous detachment and 14 (66.7%) had peripheral retina degeneration. The mean retinal nerve fibre layer (RNFL) thickness was 92.48 mm (SD, 9.99 mm). CONCLUSION: None of the 21 highly myopic eyes had features of myopic retinopathy but most of these young males had clinically visible myopia-associated abnormalities of the optic disc, vitreous and peripheral retina. Generally, these eyes had thinner RNFL. Further longitudinal studies are required to investigate if these eyes will eventually develop complications of pathological myopia.

Positional and rotational stability of the toric phakic intraocular lens under high +Gz environments.

BACKGROUND: Phakic intraocular lens (PIOL) implantation is a surgical option for correction of refractive errors. PIOLs can be use to correct myopia, hyperopia, and astigmatism. It is a surgical option available to patients in addition to methods such as laser cornea refractive surgery, e.g., laser assisted in-situ keratomileusis (LASIK) and photo-refractive keratectomy (PRK). Visian implantable collamer lens (ICL) are posterior chamber lenses which are surgically positioned in a phakic eye in the sulcus between the iris diaphragm and the natural crystalline lens. CASE REPORT: This case report describes the stability of Visian toric ICL in a candidate with bilateral implants under high +Gz force exposure in a human centrifuge trainer. The subject was sequentially exposed to three incremental +Gz profiles of +5 Gz, +7 Gz, and +9 Gz. Pre- and post-+Gz exposure, ophthalmic examination revealed no ICL displacement, implant touch or induced cataract, or change in refractive error. DISCUSSION: The rotational stability of the toric implants was also demonstrated by identical subjective refractions in both eyes taken pre- and post-+Gz, exposure. A search of the literature did not reveal any published articles on intraocular stability of ICL in the +Gz environment. This case report suggests that ICL may be considered an alternative to laser refractive surgery for patients subjected to a high +G, environment such as military aviators.

Maculopathy associated with Dengue fever in a military pilot.

Dengue fever is the most prevalent vector-borne flavivirus infection in humans. Its ocular manifestations have only recently been reported with increasing frequency. We present a case of an air force rotary wing pilot who presented with dengue-related maculopathy and decrement in visual function. The pilot ultimately recovered full visual function and was returned to full unrestricted flying duties with the proviso of regular ophthalmic monitoring. Dengue-related maculopathy may present with retinal edema, blot hemorrhages, and vasculitis. Less common features include exudative retinal detachment, cotton wool spots, and anterior uveitis. It is generally self-resolving with good prognosis. Treatment is controversial, but a course of corticosteroids has been tried in view of a postulated underlying immune-mediated pathology. It is recommended that aviators who have recovered from dengue fever undergo a clinical ophthalmological examination before return to flying duties.

Ophthalmic complications of dengue.

We report 13 cases of ophthalmic complications resulting from dengue infection in Singapore. We performed a retrospective analysis of a series of 13 patients with dengue fever who had visual impairment. Investigations included Humphrey automated visual field analyzer, Amsler charting, fundus fluorescein angiography, and optical coherence tomography. Twenty-two eyes of 13 patients were affected. The mean age of patients was 31.7 years. Visual acuity varied from 20/25 to counting fingers only. Twelve patients (92.3%) noted central vision impairment. Onset of visual impairment coincided with the nadir of serum thrombocytopenia. Ophthalmologic findings include macular edema and blot hemorrhages (10), cotton wool spots (1), retinal vasculitis (4), exudative retinal detachment (2), and anterior uveitis (1). All patients recovered visual acuity to 20/30 or better with residual central scotoma by 12 weeks. These new complications suggest a widening spectrum of ophthalmic complications in dengue infection.

Selective argon laser suturelysis versus needle suturelysis to treat induced corneal astigmatism after cataract surgery.

PURPOSE: To compare the complications and subjective experience of patients having argon laser suturelysis (LS) with those of patients having needle suturelysis (NS) for corneal astigmatism after extracapsular cataract extraction (ECCE). SETTING: Department of Ophthalmology, Tan Tock Seng Hospital, Singapore. METHODS: This prospective study comprised 30 patients (30 eyes) with more than 3.00 diopters of with-the-rule astigmatism after ECCE. A minimum of 5 weeks after surgery, 2 sutures along the steepest meridian were lysed by the same surgeon, 1 by a needle and the other by laser using a Hoskins lens. Patients were randomized to receive NS first followed by LS or LS followed by NS. The complications were recorded. The patients subjectively graded their fear and discomfort/pain during suturelysis using a scale from 0 to 10. Patient preference for either procedure was also recorded. RESULTS: The complications of NS were conjunctival epithelial defect (17/30), subconjunctival hemorrhage (13/30), and corneal abrasion (4/30) and of LS, minor conjunctival burn (1/30) and conjunctival epithelial defect (1/30). The mean subjective fear and discomfort/pain scores in the NS group were significantly higher than in the LS group (P =.0010 and P =.0014, respectively). Nineteen patients preferred LS, 3 preferred NS, and 8 had no preference for either procedure. CONCLUSION: Argon laser suturelysis was associated with fewer complications than NS and was preferred by patients.