Gonzalo Carracedo

UTP and diadenosine tetraphosphate accelerate wound healing in the rabbit cornea.

Nucleotides are naturally occurring substances present in tear film that can stimulate tear secretion in animals and humans. We investigated whether certain nucleotides can affect the rate of wound healing in the cornea of white rabbits. In the absence of any added compound, the rate of healing was 72.4 ± 2.2 μm h−1. Of all the tested nucleotides, UTP and Ap4A were the most active ones, maximally increasing the rate of healing to 121.6 ± 3.7 and 93.7 ± 3.2 μm h−1, respectively. Responses to UTP were dose dependent. UTP had a pD2 value of 8.9 ± 0.1 (EC50: 1.25 nM). P2 purinoceptor antagonists such as suramin and reactive blue‐2, inhibited the effect of UTP indicating the involvement of P2Y receptors. Mitogen‐activated protein kinase (MAPK) cascade inhibitors also abolished the effects of UTP, suggesting that P2Y receptors are coupled to the MAPK cascade, and that this is involved in controlling the rate of epithelial cell migration.

High-resolution spectral domain optical coherence tomography technology for the visualization of contact lens to cornea relationships

Purpose: To study the utility of high-resolution spectral domain optical coherence tomography (HR SOCT) in imaging the contact lens (CL) to cornea relationships with advanced CL designs for ecstatic corneas and corneal refractive therapy. Methods: Copernicus HR SOCT (Optopol Technology SA, Zawiercie, Poland) was used to evaluate different lens materials and designs in situ and for the preliminary assessment of the materials and corneal response to hypoxic situations. Results: SOCT is capable of highlighting very subtle and interesting features of the CL-cornea relationships in a wide range of applications such as in rigid gas-permeable corneal and semiscleral lenses, in corneal refractive therapy and application of CLs in ocular pathology, and in the evaluation of the physiological response of the cornea. Conclusions: HR SOCT is a powerful tool capable of providing sharp images of the anterior ocular surface highlighting the relationship between lens and cornea with great detail. This methodology has several applications to enhance fitting modeling with modern designs for advanced CL treatments.

Diadenosine polyphosphates in tears of Sjogren syndrome patients.

PURPOSE To analyze the levels of diadenosine tetraphosphate (Ap(4)A) and diadenosine pentaphosphate (Ap(5)A) in tears of subjects with Sjögren syndrome and to compare them with those in a control group. METHODS Twelve subjects with a diagnosis of Sjögren syndrome and 20 healthy control subjects were invited to participate in the present study. Schirmer strips were used to measure tear secretion (Schirmer I test) and to collect tears. Ap(4)A and Ap(5)A were measured by high-pressure liquid chromatography (HPLC), and a dry eye questionnaire (DEQ) was used to evaluate dry eye symptomatology. RESULTS The mean concentrations of Ap(4)A and Ap(5)A in the Sjögren syndrome group were 2.54 ± 1.02 and 26.13 ± 6.95 μM, respectively. This group of patients was divided in two subgroups: four patients with normal tear production and eight patients with low tear production. Concentrations of Ap(4)A, and Ap(5)A in patients with normal tear production (Schirmer test result, 12.3 ± 1.2 mm) were 0.47 ± 0.20 and 8.03 ± 3.27 μM, respectively. In the patients with low tear production (Schirmer test result, 1.0 ± 0.3 mm), the concentrations were 4.09 ± 1.36 and 39.51 ± 8.46 μM, respectively and in the control group, 0.13 ± 0.03 and 0.04 ± 0.02 μM, respectively. CONCLUSIONS Patients with Sjögren syndrome have abnormally elevated concentrations of diadenosine polyphosphates, indicating that these compounds could be used in the diagnosis of this disease.

Signs and Symptoms of Dry Eye in Keratoconus Patients: A Pilot Study

Abstract Purpose: To compare signs and symptoms of dry eye in keratoconus (KC) patients versus healthy subjects. Methods: A total of 15 KC patients (KC group, n = 15 eyes) and 16 healthy subjects (control group, 16 eyes) were enrolled in this study. The Schirmer I test with no anesthetic, tear break-up time (TBUT), corneal staining characteristics, and ocular surface disease index (OSDI) scores were evaluated for both groups. Impression cytology, combined with/scanning laser confocal microscopy (LCM), was performed to evaluate goblet cell density, mucin cloud height (MCH), and goblet cell layer thickness (CLT). Finally, tear concentrations of di-adenosine tetraphosphate (Ap4A) were assessed. Results were statistically analyzed using Shapiro–Wilk and non-parametric Wilcoxon rank sum tests. Statistical significance was set at p < 0.05. Results: KC patients had lower tear volumes and greater corneal staining than did healthy subjects (p < 0.05). OSDI scores were 44.96 ± 8.65 and 17.78 ± 6.50 for the KC and control groups, respectively (p < 0.05). We found no statistically significant differences in TBUT between groups. Impression cytology revealed lower goblet cell densities in KC group patients versus control group subjects (84.88 ± 32.98 and 128.88 ± 50.60 cells/mm,2 respectively, p < 0.05). There was a statistically significant reduction in MCH and CLT in KC group patients compared with control group subjects. Ap4A tear concentrations were higher in KC group patients than in control group subjects (2.56 ± 1.10 and 0.15 ± 0.12 µM, respectively, p < 0.05). Conclusions: The parameters evaluated in this study indicate that KC patients suffer greater symptoms of dry eye and greater tear instability, primarily due to the decreased mucin production in their tears, than do healthy patients with no KC

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 (Ap4A) 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 &mgr;m, ranging from 4200 &mgr;m to 4800 &mgr;m. 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.

Ready for action.

An efficient transmission of knowledge to students must be the main goal of any university teacher. The practical activities are the most preferred by students as they learn something closer to what they are going to practice in the future after finishing their studies, and additionally they experience in their hands the topics learnt. In the field of optometry, clinical subjects with a lot of clinical activities such as optometry, contact lenses, binocular vision or low vision are crucial as they will become parts of the common daily tasks of the optometry activity once completed the Degree. Although the aim of the majority of optometry students may be to develop the corresponding clinical skills to be good practitioners, the introduction of MSc and PhD degrees have also generated the possibility of completing the education of some optometrists with knowledge in research on eye and vision. The implementation of new master subjects, such as ‘‘Research Methods in optics, optometry and vision’’, helps students to have a more realistic idea of how to conduct research activities. This was implemented in our degree and indeed some students started their PhDs potentially influenced by subjects such as that previously mentioned. However, teaching how to perform research to Master students has not demonstrated its usefulness in our context. This year, as lecturers in the Master of Optometry and Vision of the University Complutense of Madrid (Spain), we

Changes in Diadenosine Polyphosphates during Alignment-Fit and Orthokeratology Rigid Gas Permeable Lens Wear

PURPOSE To evaluate the levels of dinucleotides diadenosine tetraphosphate (Ap(4)A) and diadenosine pentaphosphate (Ap(5)A) in tears of patients wearing rigid gas permeable (RGP) contact lenses on a daily wear basis and of patients wearing reverse-geometry RGP lenses overnight for orthokeratology treatment. METHODS Twenty-two young volunteers (10 females, 12 males; 23.47 ± 4.49 years) were fitted with an alignment-fit RGP lens (paflufocon B) for a month, and after a 15-day washout period they were fitted with reverse-geometry RGP lenses for corneal reshaping (paflufocon D) for another month. During each period, tears were collected at baseline day 1, 7, 15, and 28. Ap(4)A and Ap(5)A were measured by high-pressure liquid chromatography (HPLC). Additionally, corneal staining, break-up time (BUT), Schirmer test, and dryness symptoms were evaluated. RESULTS Ap(4)A concentrations increased significantly from baseline during the whole period of daily wear of RGP lenses (P < 0.001); concentration was also significantly higher than in the orthokeratology group, which remained at baseline levels during the study period except at day 1 (P < 0.001) and day 28 (P = 0.041). While BUT and Schirmer remained unchanged in both groups, discomfort and dryness were significantly increased during alignment-fit RGP daily wear but not during the orthokeratology period. CONCLUSIONS Daily wear of RGP lenses increased the levels of Ap(4)A due to mechanical stimulation by blinking of the corneal epithelium, and this is associated with discomfort. Also, orthokeratology did not produce symptoms or signs of ocular dryness, which could be a potential advantage over soft contact lenses in terms of contact lens-induced dryness.

Clinical performance of a new hybrid contact lens for keratoconus.

Objectives: To compare the clinical performance of the Clearkone hybrid contact lens for the treatment of keratoconus against the habitual contact lens of the patients. Methods: A total of 33 eyes from 18 patients were fitted with the Clearkone. High- and low-contrast visual acuity (HCVA and LCVA), central corneal thickness (CCT), and contrast sensitivity acuity (CSF) were recorded with habitual lenses (prestudy visit) and after 1 week, 15 days, and 1 month of wear of prescribed Clearkone. Subjective vision and comfort were rated using visual analogue scales (VAS). Results: Three patients discontinued the study, one because of diffuse corneal staining after 1 day of use and the other two because of extreme discomfort. The rest of the patients completed the 1-month study. High contrast visual acuity and LCVA (logMAR) improved significantly from 0.16 ± 0.12 and 0.44 ± 0.22, respectively, with the patients habitual contact lenses to −0.006 ± 0.058 and 0.23 ± 0.13 after 1 day wearing Clearkone, remaining significant during all follow-up visits (P<0.001; repeated measures analysis of variance [RM-ANOVA]). There were no statistically significant differences in the mean CCT. The improvement of CSF was statistically significant with hybrid contact lenses prescribed compared with the patients habitual contact lenses (P<0.001; RM-ANOVA test). Improvement in VAS score, with prescribed Clearkone, was statistically significant for comfort (P=0.043; RM-ANOVA test), but not for the subjective vision (P=0.759; RM-ANOVA test). Conclusions: Clearkone provides an improvement in visual acuity, contrast sensitivity, and subjective comfort in patients with keratoconus when compared with other contact lens options. However, clinicians must get specific training to fit the lens and be aware of potential adverse events.

Diadenosine polyphosphates release by human corneal epithelium

Diadenosine polyphosphates are a type of dinucleotides that have been detected in rabbit and human tears. However, their origin and their mechanism of release have not been fully elucidated. In this work we investigated whether the dinucleotides Ap4A and Ap5A can be released from human corneal epithelia as a consequence of shear stress stimuli. In in vitro experiments, concentrations of Ap4A and Ap5A before mechanical stimulus of stratified human corneal epithelial cells were 3.18 ± 0.43 nM and 0.81 ± 0.13 nM, respectively. After shear stimulation, concentrations significantly increased to 12.01 ± 2.19 nM for Ap4A and 2.83 ± 0.41 nM for Ap5A. No significant differences in lactate dehydrogenase activity were detected between non-stimulated stratified human corneal epithelial cells and cells exposed to mechanical shear-stress, indicating that the rise of dinucleotide levels was not due to cell lysis. In in vivo experiments, individuals subjected to a rise in blinking frequency showed a significant increase of Ap4A (∼25-fold when experiment was performed without anaesthetic and 75-fold with anaesthetic) and Ap5A concentration in tears (∼50-fold when experiment was performed without anaesthetic and 125-fold with anaesthetic). Shear-stress stimuli induces Ap4A and Ap5A release from human corneal epithelium, thus explaining the origin of these relevant compounds for the ocular surface biochemistry and physiology.

Post‐lens tear turbidity and visual quality after scleral lens wear

The aim was to evaluate the turbidity and thickness of the post‐lens tear layer and its effect on visual quality in patients with keratoconus after the beginning of lens wear and before lens removal at the end of eight hours.