Magnon Sensing of NO, NO2 and NH3 Gas Capture on CrSBr Monolayer.

Air pollution and greenhouse emissions are significant problems across various sectors, urging the need for advanced technologies to detect and capture harmful gases. In recent years, two-dimensional (2D) materials have attracted increasing attention due to their large surface-to-volume ratio and reactivity. Herein, we investigate the potential of single-layer CrSBr for gas sensing and capturing by means of first-principles calculations. We explore the adsorption behaviour of different pollutant gases (H2S, NH3, NO, NO2, CO and CO2) on this 2D ferromagnet and the impact of intrinsic defects on its magnetic properties. Interestingly, we find that Br vacancies enhance the adsorption of NH3, NO and NO2 and induce a selective frequency shift on the magnon dispersion. This work motivates the creation of novel magnonic gas sensing devices based on 2D van der Waals magnetic materials.

Visual Quality Assessment and Comparison of Monofocal and Multifocal Scleral Lens Designs: A Pilot Study.

PURPOSE: To compare visual quality, contrast sensitivity, stereopsis, subjective vision, and comfort between monofocal and multifocal scleral lens (SL) designs. METHODS: An experimental, cross over and short-term pilot study has been performed. Nineteen presbyopic patients (51.9±3.8 years) with regular corneas participated voluntarily in the study and Onefit MED monofocal and multifocal SL designs were fitted bilaterally. Subjective vision and comfort, contrast sensitivity function, stereopsis, high- and low-contrast visual acuity (VA) at 4 m and 40 cm under photopic and mesopic conditions, and defocus curves were measured. Data analysis was performed with nonparametric tests. P<0.05 was considered as statistically significant. RESULTS: Mean addition power of the prescribed lenses was 1.72±0.38 diopters. Multifocal design showed a statistically significant improvement for intermediate and near vision in the defocus curve under photopic and mesopic conditions (P<0.05), however, worsening in stereopsis (P<0.05) and contrast sensitivity for high spatial frequencies (P<0.05). Distance visual acuity (VA) showed significantly lower values under mesopic conditions for high- and low-contrast tests (P<0.05), and on low-contrast test under photopic conditions (P<0.001) with the multifocal design. CONCLUSION: Multifocal SLs showed better visual performance at intermediate and near distances without compromising distance vision under photopic conditions for a high-contrast test when compared with monofocal design.

In Vitro Evaluation of Soft Contact Lens Wettability With a Nonmodified Commercial Videokeratoscope.

PURPOSE: To evaluate a new in vitro technique for measuring soft contact lens wettability using a nonmodified commercial videokeratoscope, the Medmont E300. To this end, the capability of different artificial tears containing hyaluronic acid (HA) to improve soft contact lens wettability in vitro was investigated. METHODS: An experimental in vitro study was conducted to assess the wetting properties of three artificial tears containing different concentrations of HA (0.1%, 0.2%, and 0.3%) on soft contact lenses. A saline solution was used as the control. For each solution, 15 hydrogel (Ocufilcon D) contact lenses and 15 silicone-hydrogel (Somofilcon A) contact lenses were evaluated. The in vitro wettability of the lenses was measured using the Medmont E300 with a self-developed technique, which involved measuring the tear film surface quality (TFSQ) mean, TFSQ area, TFSQ central, and TFSQ inferior. RESULTS: Compared with the saline solution, all the concentration of HA (0.1%, 0.2%, and 0.3%) improved the in vitro wettability of both soft contact lenses by decreasing their TFSQ mean and TFSQ area ( P <0.05). Regression models revealed an exponential relationship between contact lens wettability and the concentration of HA for both soft contact lenses ( R >0.5, P <0.05). Furthermore, the hydrogel contact lens presented a wetter surface than the silicone-hydrogel contact lens ( P <0.05). CONCLUSIONS: The measurement of in vitro wettability of soft contact lenses with a nonmodified Medmont E300 seems to be a useful technique to evaluate the wetting properties of contact lens products.

Increased ocular dopamine levels in rabbits after blue light stimulation of the optic nerve head.

The purpose was to quantify ocular dopamine in rabbits after stimulation of the optic nerve head with short-wavelength (blue) light to activate melanopsin expressed in the axons of intrinsically photosensitive retinal ganglion cells (ipRGCs). Dopamine levels in tears, aqueous humor, vitreous body, and retina (including choroid) were quantified after blue light stimulation of the optic nerve head of 15 rabbits with an optical fiber for 1 min, 10 min, or no stimulation (n = 5, each group). The left eye of all rabbits was operated on to introduce the optical fiber and stimulate the optic nerve, while the contralateral eye served as internal control. One minute of blue light stimulation significantly increased dopamine concentration in the vitreous body of the treated eyes compared to the contralateral ones (P = 0.015). Stimulation for 10 min significantly increased dopamine concentration in the vitreous body, as well as the aqueous humor (P < 0.05). Therefore, using an optical fiber approach to stimulate the optic nerve head with blue light significantly increased dopamine concentration in the aqueous humor and the vitreous body. This likely reflects an upregulation of retinal dopamine synthesis that could be attributed to ipRGC activation. However, the data provided in this study fell short of establishing a definitive link between dopamine release and ipRGC activation, mainly due to the lack of evidence supporting the expression of the melanopsin photopigment in the optic nerve.

Improvement of Soft Contact Lens Wettability After the Instillation of Hyaluronic Acid Eye Drops.

PURPOSE: To evaluate the effect of the topical instillation of hyaluronic acid eye drops with different viscosity on soft contact lens wettability and comfort. METHODS: A randomized and participant-masked study was performed, involving 20 participants (25.4±2.6 years). One eye wore hydrogel (ocufilcon D) contact lenses, and another eye wore silicone-hydrogel (somofilcon A) contact lenses. The in vivo wettability tear film surface quality (TFSQ) index and comfort were measured before and after the instillation of different eye drops: saline solution (control) and 0.1%, 0.2%, and 0.3% hyaluronic acid. RESULTS: Compared with saline solution, the instillation of 0.1%, 0.2%, and 0.3% hyaluronic acid improved the in vivo wettability of the hydrogel contact lenses by decreasing their TFSQ mean for 5, 10, and 30 min, respectively ( P <0.05). During silicone-hydrogel contact lens wear, the hyaluronic acid did not affect wettability because there were no changes in TFSQ mean ( P ≥0.05), but the 0.3% hyaluronic acid produced a decrease in comfort for the first 3 min ( P <0.05). CONCLUSIONS: The instillation of hyaluronic acid eye drops increased the in vivo wettability of the hydrogel contact lens, and the duration of this effect was directly related to its concentration and viscosity.

Therapeutic potential of topical administration of siRNAs against HIF-1α for corneal neovascularization.

Given the implications of the problem of neovascularization on ocular health, as well as the growth in the number of cases, the purpose of the present study has been testing the efficacy of siRNAs (small interfering RNA) designed to silence Hypoxia Inducible Factor -1α (HIF-1α) and to demonstrate that their use stops neovascularization in a model of corneal burn. Corneal wounds in the limbic zone were made in the eyes of New Zealand white rabbits. Topical applications of siRNAs were done the next day to the wound for four consecutive days and eyes were examined with a slit lamp. Evaluation of neovascularization progress was done by analyzing images by ImageJTM and to determine the neovascular area in Matlab ® was used. At the same time, a rabbit corneal cell line was used for in vitro study of hypoxia exposure and Western blot analysis of the cell's extracts were done. Under normal cell culture oxygenation, the expression of HIF-1α was lower than that observed under hypoxic conditions. After 2 h of hypoxia, there was a significant increase in the HIF-1α expression, effect that was maintained up to 6 h. The increased in HIF-1α was mimicked by a cell permeable prolyl-4-hydroxylase inhibitor. Cobalt chloride showed no capacity to increase HIF-1α in vitro. The effect of three different siRNA on HIF-1α was tested after 4 h of hypoxia. siRNA#1 was able to silence 80% of HIF-1α expression, siRNA#2 and siRNA#3 reduce the expression in 45% and 40% respectively. In addition, the three siRNA were tested in a corneal model of neovascularization. scrambledsiRNA#2 was the most effective inhibitor of blood vessel production, followed by siRNA#3 and siRNA#1. Compared to the scrambled siRNA (100% of blood vessel generation), siRNA#2 blocked the presence of blood vessels by 83 ± 2%, siRNA#3 inhibited 45 ± 7% and siRNA#1 only inhibited 18 ± 5%. The necessary time to observe the 50% of effect showed values of NV50 of 10.2 ± 2.4 days for the scrambled siRNA, 9.1 ± 1.4 for siRNA#1, 6.5 ± 1.85 for siRNA#2 and 4.8 ± 1.8 days for siRNA#3. In conclusion, the topical application of siRNA towards HIF-1α seems to be an effective and reliable method to stop neovascularization.

Corneal Confocal Analysis after Scleral Lens Wear in Keratoconus Patients: A Pilot Study.

SIGNIFICANCE: Scleral lenses rely on the scleroconjunctival region without bearing the cornea, which could improve the symptoms and modify the corneal nerve plexus morphology. PURPOSE: This study aimed to evaluate symptoms and changes in corneal nerve plexus morphology and density of Langerhans cells in keratoconus patients with and without intrastromal corneal ring before and after scleral lens wear. METHODS: Sixteen scleral lens wearers with keratoconus were recruited for this short-term experimental pilot study. Subjects were divided into two groups: keratoconus group and intrastromal corneal ring segment group. All subjects were examined in two visits: baseline (before scleral lens wear) and after 6 months of scleral lens wear, after lens removal. The Schirmer I test, the Ocular Surface Disease Index, tear breakup time, and in vivo confocal microscopy were evaluated. RESULTS: The mean age was 42.33 ± 11.27 years. A significant decrease in tear breakup time was found in the total group ( P = .01, Wilcoxon) compared with baseline. Ocular Surface Disease Index score had decreased after 6 months of scleral lens wear in the keratoconus with intrastromal corneal ring segment subgroup ( P = .03, Wilcoxon) and in the total group ( P = .001, Wilcoxon). No statistical changes in nerve density, tortuosity, and ramification were found for either the total group or the subgroup. However, the mean nerve length was higher in all groups, especially in the keratoconus subgroup ( P = .03, Wilcoxon) after 6 months of scleral lens wear. Regarding optical density, the total group showed a significant increase after 6 months of wearing ( P = .02, Wilcoxon). Finally, Langerhans cell density was not statistically different in any group. CONCLUSIONS: These results suggest that scleral lens wearing improves the symptoms and increased the mean length nerves after 6 months of wear use in keratoconus patients.

Dual-Mode Gold Nanoparticle-Based Method for Early Detection of Acanthamoeba.

Acanthamoeba keratitis is an aggressive and rapidly progressing ocular pathology whose main risk factor is the use of contact lenses. An early and differential diagnosis is considered the main factor to prevent the progression and improve the prognosis of the pathology. However, current diagnosis techniques require time, complex and costly materials making an early diagnosis challenging. Thus, there is a need for fast, accessible, and accurate methods for Acanthamoeba detection by practitioners for timely and suitable treatment and even for contact lens user as preventive diagnosis. Here, we developed a dual-mode colorimetric-based method for fast, visual, and accurate detection of Acanthamoeba using gold nanoparticles (AuNPs). For this strategy, AuNPs were functionalized with thiolated probes and the presence of target Acanthamoeba genomic sequences, produce a colorimetric change from red to purple. This approach allows the detection of 0.02 and 0.009 µM of the unamplified Acanthamoeba genome by the naked eye in less than 20 min and by color analysis using a smartphone. Additionally, real samples were successfully analyzed showing the potential of the technology considering the lack of point-of-care tools that are mostly needed.

A Comparison between Automated Subjective Refraction and Traditional Subjective Refraction in Keratoconus Patients.

SIGNIFICANCE: The performance of the Eye Refract (Luneau Technology, Chartres, France), a new instrument to perform aberrometry-based automated subjective refraction, has been previously evaluated in healthy subjects. However, its clinical implications in other ocular conditions are still unknown. PURPOSE: The purpose of this study was to evaluate the agreement between the Eye Refract and the traditional subjective refraction, as the criterion standard, in keratoconus patients with and without intracorneal ring segments (ICRSs). METHODS: A total of 50 eyes of 50 keratoconus patients were evaluated, dividing the sample into 2 groups: 27 eyes without ICRS (37.78 ± 9.35 years) and 23 eyes with ICRS (39.26 ± 13.62 years). An optometrist conducted the refraction with the Eye Refract, and another different optometrist conducted the traditional subjective refraction on the same day. Spherical equivalent (M), cylindrical vectors (J0 and J45), and corrected distance visual acuity were compared between both methods of refraction. In addition, Bland-Altman analysis was performed to assess the agreement between both methods of refraction. RESULTS: There were no statistically significant differences (P ≥ .05) between the Eye Refract and the traditional subjective refraction for all the variables under study in either group. Without ICRS, the mean difference and 95% limits of agreement (upper, lower) were -0.20 (+1.50, -1.89) D for M, -0.14 (+1.40, -1.68) D for J0, and +0.05 (+1.23, -1.14) D for J45. With ICRS, these values worsened to -0.62 (+3.89, -5.12) D for M, +0.06 (+2.46, -2.34) D for J0, and -0.02 (+2.23, -2.28) D for J45. CONCLUSIONS: The Eye Refract seems to offer similar results compared with the traditional subjective refraction in keratoconus patients not implanted with ICRS. However, some patients could show abnormal measurements, especially those with ICRS, who should be treated with caution in clinical practice.

Efficacy of Artificial Tears Based on an Extract of Artemia salina Containing Dinucleotides in a Rabbit Dry Eye Model.

(1) Background: Artemia salina is a brine shrimp containing high concentrations of dinucleotides, molecules with properties for dry eye treatment. For this reason, the purpose of the study was to evaluate the effect of the artificial tears based on an extract of Artemia salina in a rabbit dry eye model. (2) Methods: A prospective and randomized study was carried out. Twenty rabbits were divided into 4 groups (n = 5, each group): healthy rabbits, dry eye rabbits, dry eye rabbits treated with hypromellose (HPMC), and dry eye rabbits treated with Artemia salina. Dry eye was induced by the topical instillation of 0.2% benzalkonium chloride. The measurements were performed before and after the treatment for 5 consecutive days. (3) Results: The topical instillation of artificial tears containing Artemia salina showed beneficial effects on tear secretion, tear break-up time, corneal staining, the density of Goblet cells, heigh of mucin cloud secreted by these cells, and mRNA levels of IL-1ß and MMP9 in conjunctival cells. Compared with the HPMC, there was a statistically significant improvement (p < 0.05) with the Artemia salina in all the variables under study, except for the conjunctival hyperemia, density of Goblet cells, and mRNA levels of IL-6. (4) Conclusions: The potential of artificial tears based on Artemia salina as a secretagogue agent for dry eye treatment was confirmed, opening the door for future clinical trials and studies to extrapolate the findings for dry eye patients.

Changes in melatonin receptor expression in a murine model of glaucoma.

Purpose: The objective of this study was to evaluate the changes in the melatoninergic receptors of DBA/2J and C57BL/6J mice with the development of glaucoma. DBA/2J mice are widely used to study the physiopathology of glaucoma due to the similarities of their eyes to human eyes and the resulting similarity in the development of their pathology. In addition, melatoninergic receptors are known for their control of intraocular pressure (IOP), reducing the production of aqueous humor; however, little is known about their relationship with the development of this pathology. Methods: mRNA expression of MT1, MT2, and GPR50 melatoninergic receptors was performed with quantitative real-time PCR. In addition, receptor expression was performed with immunohistochemical techniques on the ciliary processes. To further investigate the effect of melatonin and its analog 5-methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT) on IOP, animals were instilled with these compounds and the corresponding melatoninergic antagonists to assess their effect on IOP. Results: All melatoninergic receptor expression decayed with the development of the glaucomatous pathology in the DBA/2J mice, and was especially visible for the MT2 receptor. However, receptor expression was consistent in the C57BL/6J control mice across all ages investigated. Furthermore, IOP blockage was stronger with 4PPDOT (MT2 antagonist) only in the DBA/2J mice which suggests a correlation of this receptor with the development of the glaucomatous pathology in DBA/2J animals. Conclusions: Melatonin receptor expression decays with the development of the glaucomatous pathology. This implies that the physiologic hypotensive effect of endogenous melatonin reducing IOP is not possible. A solution for such changes in receptor expression is the exogenous application of melatonin or any of its analogs that permit the activation of the remaining melatonin receptors.

Differences between Inferior and Superior Bulbar Conjunctiva Goblet Cells in Scleral Lens Wearers: A Pilot Study.

SIGNIFICANCE: Scleral lenses (SLs) rest on the scleroconjunctival region, which could result in a mechanical impact in the bulbar conjunctiva that can hypothetically modify some properties of conjunctival cells. PURPOSE: The purpose of this study was to evaluate the differences in goblet cell density (GCD) and mucin cloud amplitude (MCA) between superior and inferior bulbar conjunctiva in SL wearers. METHODS: A total of 26 eyes wearing SL were randomly selected from 26 subjects (11 females) with different grades of keratoconus enrolled in a prospective clinical series. Superior and inferior conjunctival impression cytologies were performed and therefore analyzed with scanning laser confocal microscopy to evaluate GCD and MCA. All subjects filled out the Ocular Surface Disease Index (OSDI) questionnaire. RESULTS: The mean ± standard deviation OSDI score was 23.62 ± 15.12. Although a higher density of goblet cells was observed in the samples taken in the superior conjunctiva (74.70 ± 57.55 cells/mm) than on the inferior conjunctiva (55.91 ± 34.80 cells/mm), there were no statistically significant differences between them (P = .14, Wilcoxon). Regarding MCA, no differences were found between superior (21.81 ± 3.30 µm) and inferior (20.72 ± 2.95 µm) samples (P = .201, Wilcoxon). No statistically significant differences were found in GCD and MCA regarding the time of SL wear. CONCLUSIONS: There were no differences in GCD and MCA in the samples taken in the superior and inferior conjunctival areas. Also, it seems that the SL wearing time does not affect the density and secretion of goblet cells. Prospective studies need to be conducted in larger samples to confirm those outcomes.

Correlation Between Anterior Corneal Elevation Differences in Main Meridians and Corneal Astigmatism.

PURPOSE: To assess the correlation between anterior corneal elevation (ACE) and anterior corneal astigmatism (ACA) obtained with two different topographers in healthy subjects at different corneal diameters. METHODS: A retrospective, comparative, and observational study was conducted. Topography data from 305 patients obtained with the Oculus Pentacam (Oculus, Wetzlar, Germany) and Sirius (CSO, Florence, Italy) systems were collected. Subjects were divided into four groups depending on the magnitude of ACA. The ACE was evaluated in the principal meridians at 2, 3, and 4 mm from the corneal apex. The difference in ACE between meridians (ACE-M) and in superior-inferior and nasal-temporal semimeridians (ACE-SM) was calculated. RESULTS: A strong positive correlation between ACE-M and ACA with both topographers was found for all corneal diameters (P<0.001). A linear equation to calculate the ACE-M differences as a function of the astigmatism at 8 mm of diameter was obtained: y=23.417x+1.40, where y is ACE-M in microns and x is ACA in diopters. Significant differences in ACE along SM were found for all groups studied according to the magnitude of ACA for the horizontal SM (P>0.001). The temporal meridian was more elevated at 4- and 6-mm diameters, and the nasal semimeridian was the most elevated for 8 mm. CONCLUSION: Anterior corneal astigmatism and elevation differences are strongly correlated, providing more corneal topography knowledge that could be applied in the contact lens fitting. A toric orthokeratology lens may be indicated in ACA greater than 0.75 D.

Effect of Melatonin and Its Analogs on Tear Secretion.

Melatonin has been shown to enhance tear secretion associated with dinucleotide diadenosine tetraphosphate. This study investigated the isolated action of melatonin and its analogs, agomelatine, N-butanoyl-2-(2-methoxy-6H-isoindolo[2,1-a]indol-11-yl) ethanamine (IIK7), and 5-methoxycarbonylamino-N-cetyltryptamine (5-MCA-NAT) (10 µl at 100 µM), on tear secretion when applied topically in the rabbit cornea and its relationship with the melatonin MT1, MT2, and MT3/quinone reductase QR2 receptors. The results showed a significant increase in tear secretion, with a maximal effect at 60 minutes for the agonists (138.9% ± 6.5%, 128.9% ± 6.4%, and 120.0% ± 5.2%, respectively; P < 0.05; 100% control) but not for melatonin (101.6% ± 7.9%; P > 0.05). Agonist action was tested combined with the antagonists DH97 (MT2 selective), prazosin (MT3/QR2 inhibitor), and luzindole (nonselective MT membrane receptor) (10 µl at 100 µM). DH97 reversed the effect of agomelatine, IIK7, and 5-MCA-NAT up to 30.85% ± 7.6%,108% ± 7.2%, and 87.01% ± 7.6%, respectively (P < 0.05; 100% control). Luzindole antagonized agomelatine and 5-MCA-NAT up to 67.35% ± 7.6% and 92.12% ± 8%, respectively (P < 0.05). Prazosin only reversed 5-MCA-NAT action up to 84.2% ± 7.7% (P < 0.05). These results suggest different pathways for the agonists to act through MT membrane receptors. Therefore, agomelatine, IIK7, and 5-MCA-NAT act through MT membrane receptors as secretagogues of tear secretion, and these analogs could be considered excellent therapeutic candidates for dry eye treatment. SIGNIFICANCE STATEMENT: Currently, dry eye with aqueous deficit is treated by adding artificial tears palliatively. This study shows that topical installation of three melatonin analogs (agomelatine, IIK7, and 5-MCA-NAT), but not melatonin, in therapeutic doses in the rabbit cornea significantly increases tear production, acting through different melatonin membrane receptor subtypes. Therefore, this study suggests that melatoninergic compounds could be considered excellent therapeutic candidates for dry eye treatment and ocular surface diseases occurring with a reduction in tear production.

Anterior Corneal Curvature and Aberration Changes After Scleral Lens Wear in Keratoconus Patients With and Without Ring Segments.

OBJECTIVE: To evaluate changes in the anterior corneal curvature and aberrometry after scleral contact lens wear in keratoconus (KC) subjects with and without intracorneal ring segments (ICRS). METHODS: Twenty-six subjects diagnosed with keratoconus were selected to participate in the study. Subjects were divided into 2 groups, those with ICRS (KC-ICRS group) and those without ICRS (KC group). Subjects were instructed to wear 16.5-mm scleral lenses for 8 hours. Topographic and aberrometric parameters were evaluated before lens wear and immediately after lens removal. Anterior corneal curvature was evaluated at corneal diameters of 2, 4, 6, and 8 mm, and corneal aberrations were measured at 4-, 6-, and 8-mm pupil diameters. RESULTS: The mean age of subjects was 36.95±8.95 years. In KC group, there was a statistically significant flattening of the central corneal curvature, from 6.98 to 7.09 mm (P<0.05). No changes were found in the central corneal curvature in the KC-ICRS group. The KC group showed anterior corneal curvature flattening, mainly in the nasal quadrant. The KC-ICRS group showed flattening primarily in the inferior hemisphere. In the KC group, spherical aberration for 6-mm pupil increased significantly. In the KC-ICRS group, changes in aberrations were significant for high-order root mean square at 4- and 6-mm pupil diameters (P<0.05), for oblique astigmatism for 4 mm and 6 mm, and for vertical coma for 4-mm pupil (P<0.05). CONCLUSION: Short-term scleral lens wear showed flattening of the anterior corneal surface in all subjects. In the KC group, the flattening was more pronounced in the nasal quadrant while changes were more pronounced inferiorly in KC-ICRS group.

Characterization of Corneoscleral Geometry Using Fourier Transform Profilometry in the Healthy Eye.

OBJECTIVE: To characterize peculiarities of the corneoscleral geometry in healthy eyes. METHODS: This is a prospective case series including 88 healthy eyes of 88 patients with an age ranging from 21 to 73 years. A complete ocular examination was performed with emphasis on the analysis of the corneoscleral topographic profile with the Fourier transform profilometer Eye Surface Profiler (Eaglet-Eye BV, Houten, the Netherlands). The distribution of different topographic parameters was evaluated, as well as the correlations between corneal and scleroconjunctival parameters. RESULTS: Mean values of 8.64±0.37 (range, 7.81-9.50 mm), 6.06±0.52 (4.88-7.63 mm) and 11.93±1.32 mm (8.17-15.89 mm) were obtained for inner, limbal, and outer best-fit sphere, respectively. Mean values of 8.54±0.38 (7.86-9.66 mm) and 13.35±1.29 mm (11.05-17.31 mm) were obtained for mean corneal and scleral radius, respectively. Regarding tangent angles at limbus, mean values of 35.31±6.55°, 38.76±5.90°, 32.75±7.04°, and 25.91±8.99° were obtained for nasal, temporal, superior, and inferior angles, respectively. Mean difference between temporal and nasal sagittal heights increased from -1.48±120.70 µm for a chord of 11 mm to 73.53±236.55 µm for a chord of 14 mm. A weak but statistically significant correlation was found between corneal and scleral radii (r=0.325, P=0.004). The maximum sagittal height for a diameter of 12 mm was significantly correlated with flattest keratometry, astigmatism, corneal diameter, and corneal eccentricity (R: 0.77, P<0.001). CONCLUSIONS: The scleroconjunctival surface in the healthy eye presents some level of nasotemporal asymmetry that is higher with increasing diameters of analysis.

Comparison Between Viscous Teardrops and Saline Solution to Fill Orthokeratology Contact Lenses Before Overnight Wear.

OBJECTIVE: To compare, in terms of efficacy, the differences between the use of saline solution and a viscous artificial tear to fill the lens during the first month of orthokeratology wear. METHODS: A pilot, double-masked, crossed, randomized, and prospective study was conducted. In this study, 20 subjects (14 males and 6 females) with a mean age of 16.29±6.22 years (range, 10-26) were fitted with orthokeratology contact lenses. For the study, nonpreserved 0.9% NaCl commercial saline solution (Avizor, Madrid, Spain) and nonpreserved artificial teardrops with 0.3% of hyaluronic acid (Ocudry 0.3%; Avizor, Madrid, Spain) were used. Corneal staining, tear break up time (TBUT), topography, refraction, visual acuity, and subjective comfort and vision with the visual analog scale (score from 0 to 10, being 10 better comfort and vision) were evaluated at 1 day, 1 week, and 1 month of contact lens wear. RESULTS: The corneal staining was statistically greater in the saline group than in the Ocudry group for the first day and during 1 week of wear (P<0.05). Comfort was found to be statistically better, with Ocudry 0.3% than saline solution, being 7.17±1.94 and 6.37±1.63, for the first day, and 8.78±0.43 and 8.15±0.62 for the day 28, respectively (P<0.05). However, no differences were found for subjective vision scores, TBUT, spherical equivalent, best-corrected visual acuity and uncorrected visual acuity, and mean keratometry between groups for any visit (P>0.05). CONCLUSION: Viscous artificial tears improve the subjective comfort of patients and reduce the corneal staining, compared with saline solution during the orthokeratology lenses fitting process. However, no differences between solutions for the treatment efficacy, in vision and corneal topography, were found.

Variation of Coma Aberration With Prismatic Soft Contact Lenses.

PURPOSE: To analyze the variation in vertical coma and the rest of ocular aberrations before and after fitting prismatic soft contact lenses (PSCL). METHODS: Thirty-seven eyes of 20 healthy subjects (24.30±2.03 years) were evaluated to analyze the variation in ocular wavefront aberrations before and after fitting PSCL of different base-down prism values (1.0, 1.5, and 2.0 prism diopters [PD]), designed to study its influence in the compensation of vertical coma aberration. A Hartmann-Shack sensor with a wavelength of 780 nm was used, considering a pupil size of 3 mm. In addition, the influence of PSCL in visual function under photopic conditions in terms of high-contrast visual acuity and contrast sensitivity was evaluated. RESULTS: There was statistically significant differences (P<0.05) in ocular aberrations from first to seventh order after fitting PSCL, but only the differences in vertical tilt, horizontal tilt, defocus, vertical astigmatism, and vertical coma were clinically relevant (Strehl ratio <0.8). The mean of vertical coma (µm) was 0.022±0.030 for control, 0.045±0.064 for 1.0 PD (P=0.645), 0.048±0.053 for 1.5 PD (P=0.037), and 0.074±0.047 for 2.0 PD (P<0.001). The changes in visual function under photopic conditions were not clinically relevant. CONCLUSIONS: PSCL induce a magnitude of vertical coma aberration directly proportional to prism value without affecting the rest of ocular high-order aberrations.

Ocular Surface Temperature During Scleral Lens Wearing in Patients With Keratoconus.

OBJECTIVE: To evaluate the ocular surface temperature using an infrared thermography camera before and after wearing scleral lens in patients with keratoconus and correlate these results with the tear production and stability. METHODS: A pilot, experimental, short-term study has been performed. Twenty-six patients with keratoconus (36.95±8.95 years) participated voluntarily in the study. The sample was divided into two groups: patients with intrastromal corneal ring (KC-ICRS group) and patients without ICRS (KC group). Schirmer test, tear breakup time (TBUT), and ocular surface temperature in the conjunctiva, limbus, and cornea were evaluated before and after wearing a scleral lens. RESULTS: The patients wore the scleral lenses from 6 to 9 hours with average of 7.59±0.73 hours. No significant changes in Schirmer test and TBUT were found for both groups. No temperature differences were found between the KC-ICRS and the KC groups for all zones evaluated. There was a slight, but statistically significant, increase in the inferior cornea, temporal limbus, and nasal conjunctival temperature for KC-ICRS group and temporal limbus temperature decreasing for the KC group after wearing scleral lens (P<0.05). The conjunctiva and limbus temperature was statistically higher than the central cornea for both groups before and after scleral lenses wearing (P<0.05), but no difference in the peripheral cornea was found. No statistically significant differences in the central corneal temperature were found between the groups after scleral lens wearing (P>0.05). CONCLUSION: Scleral contact lens seems not to modify the ocular surface temperature despite the presence of the tear film stagnation under the lens.

Short-term Effect of Scleral Lens on the Dry Eye Biomarkers in Keratoconus.

PURPOSE: To evaluate the most important signs of dry eye, such as osmolarity, inflammation, and diadenosine tetraphosphate (Ap(4)A) concentration before and after wearing scleral lenses for 8 h in keratoconus patients. METHODS: A pilot, experimental, short-term study involved 26 keratoconus patients (average age, 36.95 ± 8.95 years). They voluntarily enrolled in the study at the Optometry Clinic of the Faculty of Optics and Optometry in the University Complutense of Madrid. They were divided into two groups: patients with intrastromal corneal ring, the ICRS group, and patients without ICRS, the keratoconus (KC) group. Ocular Surface Disease Index questionnaire, the Schirmer test without anesthesia, tear break-up time, matrix metalloproteinase 9 (MMP-9) concentration, osmolarity, and Ap4A concentration were evaluated before and after wearing a scleral lens for 8 h. RESULTS: The patients wore the scleral lenses from 6 to 9 h, with a mean of 7.59 ± 0.73 h. The mean scleral lens sag for all patients was 4310 ± 166.31 µm, ranging from 4200 µm to 4800 µm. No significant changes in the Schirmer test and tear break-up time were found for either group. Ocular Surface Disease Index scores were statistically lower after wearing scleral lenses for both groups (p < 0.05). A significantly lower osmolarity and a significant rise of MMP-9 concentration after wearing scleral lenses were found in both groups (p < 0.05). Diadenosine tetraphosphate concentration was lower after wearing the scleral lens in the KC group (p < 0.05) but no significant difference was found for the ICRS group (p > 0.05). CONCLUSIONS: Short-term scleral lens wearing improves the symptomatology and some signs of dry eye, such as osmolarity and Ap4A concentration. The increase of MMP-9 concentration could be caused by tear film stagnation and use of preserved saline.