Clinical experimental trials on changes in ocular surface induced by soft contact lenses wear

Ph.D. Thesis in Sciences Specialization in PhysicsContact lenses (CL) are an important method of refractive error correction. Every year, millions of people commence CL wear. About 140 million people in the world wear CL and almost 90% of them wear soft contact lenses (SCL). Every year, several lenses with different materials, designs or chemical composition come in the market. It is becoming one of the important businesses with billions of dollars investment. As CL are placed directly on eyes, it may affect the cornea, conjunctiva, eyelids, and tears either mechanically, physiologically and/or immunologically. The present thesis work was developed to analyse some of these aspects. The main objective of this thesis was to study the changes in ocular surface induced by SCL. Several experiments were conducted to study the effect of SCL wear on the cornea, conjunctiva and tear film in more than 75 subjects who had never worn lenses before. One of the objectives was to determine the goblet cell density (GCD) in healthy eyes of non-CL wearers and to find out the relationship between GCD and tear function and ocular surface physiology. It was also investigated the changes on conjunctival epithelial cell morphology and GCD with SCL wear. Conjunctival impression cytology was performed on superior bulbar conjunctiva for this cytological experiment. The next experiment was designed to determine the effect of SCL wear on conjunctival bulbar and limbal redness and conjunctival and corneal staining. Changes on corneal biomechanical properties [corneal resistance factor (CRF) and corneal hysteresis (CH)] with CL wear were also evaluated with the Ocular Response Analyzer (ORA). The objectives of the experiments on intraocular pressure (IOP) were to investigate the accuracy of IOP measurement over SCL and to determine the changes in IOP after three months of CL wear. It was measured Goldmann-correlated intraocular pressure (IOPg) and corneal-compensated intraocular pressure (IOPcc) with ORA. The effect of CL wear on contrast sensitivity function (CSF) was evaluated with CSV-1000 VectorVision. From the experiments on conjunctival cytology, it was observed high variation on GCD on the superior bulbar conjunctiva and the stability of the tear film was correlated with this parameter. SCL wear affected conjunctival GCD and the reduction observed in GCD was dependent upon lens materials. Epithelial cell metaplasia grading increased by at least one grade in more than twothirds of the eyes, but this was not statistically significant. SCL wear increased conjunctival bulbar and limbal redness, conjunctival and corneal staining independent upon the wearing modality. Even the lenses with hyperpermeability materials could not maintain the same ocular surface physiology. It was associated with lens materials and the increment was higher during the early period of wear. Higher conjunctival redness was observed on the temporal and nasal region while higher corneal staining was observed on the inferior cornea. It was also found that SCL wear affected corneal biomechanical properties, however, different properties were affected differently. CRF reduced significantly and was associated with lens materials, but no change was observed on CH. It was found that ORA underestimates IOP measured over SCL and this underestimation was more than 3 mmHg in about one-third of the eyes. Moreover, IOPcc was more affected than IOPg. It was observed that three-months of SCL wear reduced IOP and this was associated with lens materials as well as corneal properties. In the present study it was found that CSF was better with CL than with spectacles and three months of SCL wear did not change the CSF in any spatial frequencies. In general, these experiments showed that a variety of changes can occur on the ocular surface by three-months of SCL wear which were associated with lens materials. Reduction in GCD affects the tear film stability which may cause lens-related dry eye. Current CL with high oxygen permeability also affect ocular surface physiology like conjunctival redness and corneal staining. Although these changes can be clinically non-significant, these can affect the comfort level of lens wearers. Effect of SCL wear on IOP should be remembered on the treatment of glaucoma risk subjects. Since the same lens material affects differently on conjunctival cytology or ocular surface physiology or on IOP, there may not be an ideal CL for every subject. Lens materials should be selected for a particular subject depending upon his/her ocular health status.As Lentes de Contacto (LC) são um importante método de compensação dos erros refrativos. Todos os anos, milhões de pessoas iniciam o uso de LC. Cerca de 140 milhões de pessoas no mundo usam LC e aproximadamente 90% destes usam lentes de contacto hidrófilas (LCH). Todos os anos, várias lentes com diferentes materiais, desenhos ou composições químicas entram no mercado. Está a tornar-se um dos mais importantes negócios com biliões de dólares de investimento. Uma vez que as LC são colocadas diretamente nos olhos, podem afetar a córnea, conjuntiva, pálpebras e lágrima tanto mecânica, fisiológica como imunologicamente. O presente trabalho de doutoramento foi desenvolvido de forma a avaliar alguns destes aspetos. O principal objetivo desta tese foi estudar as alterações na superfície ocular induzidas pelo uso de LCH. Foram levados a cabo vários ensaios de forma a estudar o efeito do uso das LCH na córnea, conjuntiva e no filme lacrimal em mais de 75 indivíduos que nunca tinham usado lentes. Um dos objetivos foi determinar a densidade de células caliciformes (DCC) em olhos saudáveis em não utilizadores de LC e encontrar a relação entre a DCC, a função lacrimal e a fisiologia da superfície ocular. Foram também pesquisadas as alterações na morfologia das células epiteliais e DCC com o uso das LCH através de citologia de impressão conjuntival na conjuntiva bulbar superior. Foi ainda determinado o impacto do uso de LCH na hiperemia da conjuntiva bulbar e limbal, tingido corneal e conjuntival. As alterações nas propriedades biomecânicas da córnea [fator de resistência corneal (CRF – Corneal Resistance Factor) e histerese corneal (CH – Corneal Hysteresis)] com o uso de LC foram também avaliadas com o Ocular Response Analyzer (ORA). A avaliação da pressão intraocular (PIO) serviu para investigar a exatidão da medição da PIO sobre as LCH e determinar ainda as alterações neste parâmetro após três meses de uso de LC. Foi ainda medida a pressão intraocular correlacionada Goldmann (PIOg) e pressão intraocular compensada (PIOcc) com o ORA. O efeito do uso de LC na sensibilidade visual ao contraste (SVC) foi também avaliado, utilizando-se para isso o CSV-1000 VectorVision. Nos estudos realizados para a avaliação da citologia conjuntival, observou-se uma grande variação da DCC da conjuntiva bulbar superior e encontrou-se um correlação entre a estabilidade do filme lacrimal e este parâmetro. O uso de LCH afetou a DCC conjuntival e a redução observada foi dependente do material das lentes. Na classificação da metaplasia das células epiteliais observou-se um aumento de pelo menos um grau em mais de dois terços dos olhos, mas esta diferença não foi estatisticamente significativa. O uso de LC provocou um aumento da hiperemia conjuntival bulbar e limbal mas os tingidos corneal e conjuntival não apresentaram relação com a modalidade de uso das lentes. Mesmo as lentes com materiais hiperpermeavéis não conseguiram manter a fisiologia da superfície ocular. Estas alterações mostraram estar relacionadas com os materiais das lentes e o incremento foi maior durante o período inicial de uso. A maior hiperemia conjuntival foi observada na região temporal e nasal enquanto o maior tingido corneal foi observado na zona inferior. Também se observou que o uso de LC afetou as propriedades biomecânicas da córnea, no entanto, as diferentes propriedades não foram afetadas da mesma forma. O CRF diminuiu significativamente, verificando-se uma relação com o tipo de material das lentes; no entanto, não foram observadas alterações na CH. Verificou-se ainda que o ORA subestima a PIO medida sobre as LC e esta diferença ascendeu a 3 mmHg em cerca de um terço dos olhos avaliados; além disso, a PIOcc foi mais afetada do que a PIOg. Observou-se ainda que durante os três meses de uso de LC houve uma redução da PIO. Este efeito das lentes na PIO foi relacionado com o material da LC assim como com as propriedades corneais. Este estudo permitiu observar que a SVC era maior com LC do que com óculos e que não sofreu nenhuma alteração durante os três meses de uso das lentes para nenhuma frequência espacial. Em geral, este estudo mostrou que são várias as alterações que podem ocorrer na superfície ocular durante três meses de uso de LCH e que estas se encontram relacionadas com o tipo de material das lentes. A redução da DCC afeta a estabilidade do filme lacrimal o que pode levar a sintomas de secura ocular. As LC com elevada permeabilidade ao oxigénio também afetaram a fisiologia da superfície ocular induzindo hiperemia conjuntival e tingido corneal. No entanto, emboras estas alterações não sejam clinicamente significativas, podem afetar o nível de conforto dos utilizadores de LC. O efeito do uso de LCH na PIO deve ser tida em conta no tratamento de indivíduos com risco de glaucoma. Uma vez que o mesmo material de lente afeta de forma diferente a citologia conjuntival, a fisiologia da superfície ocular ou a PIO, pode não haver uma LC ideal para todos os pacientes. Assim, o material das lentes deve ser selecionado para um determinado indivíduo dependendo da saúde ocular do mesmo

Effect of soft contact lens wear on tear level and subjective comfort level

Purpose: The purpose of this study was to determine the effect of three months of soft contact lens (CL) wear on Schirmer score and tear break-up time (TBUT). We also evaluated the effect of change in tear level on subjective comfort level. Methods: This was a longitudinal prospective study conducted in normal myopic subjects who had never worn CL before. Schirmer I test and fluorescein TBUT were measured in each subject. Subjects were fitted with a daily disposable (Nelfilcon A or Stenofilcon A) in one eye and a monthly disposable (Lotrafilcon B or Comfilcon A) in the other eye. Level of comfort was subjectively evaluated two times a day (after commencing lens wear and before taking out the lens) every day in a 100 division scale. The average values were used in the analysis. Level of comfort on first month was compared with the comfort on third month. Tear level tests were repeated after three months of lens wear. Results: Schirmer score reduced by 5.8±9.3 mm (p = 0.000) and TBUT reduced by 2.8±7.9 secs (p = 0.009) after three months of CL wear. The changes in Schirmer score and TBUT were not associated with the lens materials (One way ANOVA, p > 0.05). Subjective comfort level during first month and third month remained same (p = 0.272). There was no correlation of tear Schirmer socre and TBUT with subjective comfort level (p > 0.05). Conclusion: Three months of soft contact lens wear reduced tear level; however, it did not reduce the subjective comfort level.info:eu-repo/semantics/publishedVersio

Intraocular pressure measurement with ocular response analyzer over soft contact lens

Purpose: To compare intraocular pressure (IOP) measured with ocular response analyzer (ORA) with and without soft contact lenses (CL) on eye. Methods: Goldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) were measured in 56 eyes of 28 subjects without any ocular pathology, using ORA. One eye was fitted with Narafilcon A (1-Day Acuvue True Eye, Johnson & Johnson) and the other eye with Nelfilcon A (Daily AquaComfort Plus, Ciba Vision), each with −3.00D and IOPg and IOPcc were again measured over CL. The variation in the IOP with and without CL was determined. Results: Out of 28 subjects, 54% (15) were female. Mean age of the subjects was 29.4 ± 9.8 years. Both the IOPg and IOPcc when measured with CL, were found statistically significantly lower than without CL (p < 0.05). In subjects wearing Narafilcon A lens, IOPg and IOPcc were found 0.88 ± 2.04 mmHg and 1.55 ± 2.16 mmHg lower than without CL, respectively. Similarly, with Nelfilcon A lens, IOPg and IOPcc were found to be 1.03 ± 1.93 mmHg and 1.62 ± 3.12 mmHg lower, respectively. IOPcc was highly affected and underestimated by more than 3 mmHg in upto 36% of the subjects. Conclusion: Measurement of IOP over minus (−3.00D) CL with ORA is dependent upon CL properties when measured in normal IOP population. It showed lower IOP over Narafilcon A and Nelfilcon A soft CL in comparison to the pressures measured without lenses. IOPg was found less affected by CL. For the accurate measurement of IOP with ORA, CL should be removed

Central and peripheral ocular high-order aberrations and their relationship with accommodation and refractive error: a review

High-order aberrations (HOAs) are optical defects that degrade the image quality. They change with factors such as pupil diameter, age, and accommodation. The changes in optical aberrations during accommodation are mainly due to lens shape and position changes. Primary spherical aberration (Z(4.0)) is closely related to accommodation and some studies suggested that it plays an important role in the control of accommodation. Furthermore, central and peripheral HOAs vary with refractive error and seem to influence eye growth and the onset and progression of myopia. The variations of central and peripheral HOAs during accommodation also appear to be different depending on the refractive error. Central and peripheral high-order aberrations are closely related to accommodation and influence the accuracy of the accommodative response and the progression of refractive errors, especially myopia.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/ FISOTI/31486/2017 and POCI-01-0145-FEDER-031486. The author Jessica Gomes is also supported by PhD grant 2020.08737.BD from the FCT

Contrast sensitivity function with soft contact lens wear

Purposes: To compare contrast sensitivity function (CSF) with soft contact lens (SCL) and spectacles wear. To investigate the effect of a three-month period of SCL wear on CSF.Methods: Forty-seven myopic subjects with no history of contact lens (CL) wear were included in this longitudinal prospective study. CSF was measured with spectacles using the CSV-1000 (VectorVision, Greenvile, OH). Subsequently, subjects were fitted with a daily disposable lens (Nelfilcon-A, Stenofilcon-A or Nesofilcon-A) in one eye and a monthly disposable lens (Lotrafilcon-B. Comfilcon-A or Balafilcon-A) in the other eye and wore the same type of CLs for three months. CSF was measured again on the same day and after three months wearing CLs. Differences in CSF with spectacles and CLs on baseline and changes to CSF after three months of CLs wear were assessed. The effect of lens materials and wearing modality on CSF change was also investigated.Results: CSF was higher with CLs in comparison to the values with spectacles for spatial frequencies of 3, 6 and 12 cycles per degree (cpd) (p 0.05). There was no difference in CSF between hydrogel and silicone CLs as well as when comparing daily with monthly wear CLs (p > 0.05).Conclusion: CSF is better with CLs than with spectacles. CSF values with CL are similar between =baseline and after 3 months of lens wear. (C) 2020 Spanish General Council of Optometry. Published by Elsevier Espana, S.L.U.This work was supported by the Portuguese Foundation for Science and Technology (FCT) within the framework of the Strategic Funding UID/FIS/04650/2019

Effect of accommodation on coma at central and peripheral retina

Coma is one of the most common ocular higher order aberrations and highly affects the quality of image. It is assumed that corneal aberrations are balanced by internal (lenticular) aberrations so that retinal image quality may not have great impact. However, during accommodation, the shape, position, and curvature of the crystalline lens changes which might disrupt this balance between internal and corneal aberration. This study aimed to investigate the effect of accommodation on primary coma (3 −1 and 3 1 ) and secondary coma (5 −1 and 5 1 ) in relaxed and accommodated eyes. Zernike coefficients were measured in 53 subjects with Hartmann-Shack aberrometer both at the central and peripheral retina up to 30º off-axis in horizontal and vertical meridians. The process was repeated with 2.50 D accommodation stimulus and comas were compared with and without accommodation. Root-mean-square of total coma was also assessed. With accommodation, vertical comas changed to more negative value and horizontal comas changed to more positive values in most of the off-axis positions. In contrast, the secondary vertical comas became less negative and secondary horizontal comas became more negative with accommodation in most of the off-axis fixations. Thus, the results showed that accommodation affects coma which depends up on position of the fixation.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FIS-OTI/31486/2017 and POCI-01-0145-FEDER-031486

Assessment of central and peripheral accommodative lag by aberrometry

Accommodation lag is important factor for normal vision. Higher lag of accommodation may cause various ocular symptoms particularly during near tasks. In this study, the lag of accommodation was assessed in the peripheral retina and it was compared with the central accommodative lag with aberrometer. In this cross-sectional study, fifty-three young subjects with normal visual acuity and without any active ocular disease or past ocular surgery were included. Aberrations in the central and peripheral field of view up to 30° off axis from the centre in horizontal and vertical meridian in 10° steps were measured with Hartmann-Shack aberrometer with stimulation of accommodation by -2.50D lens. Accommodative stimulus and accommodative response were calculated with defocus and hence accommodative lag was obtained. Accommodative lag in the centre and periphery was compared. Repeated measure of ANOVA showed that there were significant differences in lag of accommodation in various eccentricities (F(8.912, 454.514) = 2.372, p = 0.013). Pairwise test showed that lag in the centre was similar with lag on other peripheral field of view (p > 0.05). However, accommodative lag at 10° nasal field was significantly lower than the lag at 20° temporal, 20° nasal, 30° temporaland 30° nasal (p < 0.05). Similarly, lag at 10° superior fixation was lower than lag at 20° temporal, 20° nasal, 30° temporal and 30° nasal fixations (p < 0.05). We found higher lag of accommodation in horizontal off-axis fixations in comparison to that of vertical off-axis fixations (p < 0.05). Lag of accommodation was positive correlated with vertical coma and primary spherical aberrations but negative correlated with secondary spherical aberrations (p < 0.05). Thus, Hartmann-Shack aberrometer was successfully used to assess accommodative lag in the peripheral field of view up to 60° visual field. Peripheral lag of accommodation depends up on eccentricity. Lag was found higher in horizontal off-axis fixation than at vertical fixations. Coma and spherical aberration had association with lag.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FISOTI/31486/2017 and POCI-01-0145-FEDER-031486.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FIS-OTI/31486/2017 and POCI-01-0145-FEDER-031486

Real-time wavefront aberrometry in subjects with accommodative excess

The purpose of this study was to use real-time wavefront aberrometry to detect accommodative excess (AE) and to analyse the optical quality of the eye in subjects with this dysfunction. AE was detected from the accommodative response obtained by real-time wavefront aberrometry. These subjects had a significant accommodative lead to all stimuli and had difficulty relaxing accommodation. The root mean square (RMS) of high order aberrations (HOA) was higher in subjects with AE for lower stimulus and for disaccommodation than in the control group. However, the subjects with AE showed a decrease in the RMS of HOA with an increase in accommodative response. Primary spherical aberration tended to become more negative with accommodation in both subjects and there was no difference between the groups. Real-time wavefront aberrometry can be used as an objective method to detect accommodative excess.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FIS-OTI/31486/2017 and POCI-01-0145-FEDER-031486. The author Jessica Gomes is also supported by the PhD grant 2020.08737.BD from FCT

Wavefront sensing for objective assessment of vision therapy efficacy: preliminary results

The aim of this study was to use wavefront sensing to objectively evaluate the effects of vision therapy in subjects with insufficiency (AI) and infacility of accommodation (AINF). Aberrometry was performed with a Shack-Hartmann wavefront aberrometer for different accommodative stimuli in one subject with AI and one with AINF before and after treatment with vision therapy (VT). A control subject received a placebo treatment. Real-time accommodative response, accommodation and disaccommodation reaction time, accommodative microfluctuations and root mean square of higher order aberrations were compared before and after VT/placebo. VT was effective and wavefront sensing can be used to detect AI and AINF and evaluate these subjects during VT.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FISOTI/31486/2017 and POCI-01-0145-FEDER031486. The author Jessica Gomes is also supported by the PhD grant 2020.08737.BD from FCT

Spherical aberration and accommodative insufficiency: Is there a Link?

Given the relationship between spherical aberrations and accommodation, the study of these aberrations can be helpful to understand accommodative response in subjects with accommodative dysfunctions. The purpose of this study was to evaluate on-axis and off-axis changes of primary and secondary spherical aberrations, Z(4,0) and Z(6,0), with accommodation in subjects with accommodative insufficiency (AI). Ten subjects with AI and eleven without any accommodative dysfunction (control) participated in this study. On-axis defocus Z(2,0), Z(4,0), and Z(6,0) were obtained in both groups with a Hartmann–Shack aberrometer for the unaccommodated state and with 1.00 D, 2.44 D, 3.83 D, and 4.73 D of accommodative stimuli. Z(4,0) and Z(6,0) were also measured on 11.5◦ and 23◦ temporal, nasal, superior, and inferior retinal areas for unaccommodated state and for 2.44 D of accommodative stimulus. In the control group, Z(4,0) became more negative with accommodation and Z(6,0) became more positive, as was expected according to previous studies. This tendency was not observed in the group of subjects with AI group for Z(4,0) or for Z(6,0). No differences on off-axis Z(4,0) and Z(6,0) were observed between the groups. The changes of spherical aberrations with accommodation seem different in subjects with AI compared to those without any accommodative dysfunction. Those with AI do not present a decrease in Z(4,0) and an increase in Z(6,0) with accommodation as occurs in eyes without this type of dysfunction. Understanding how the optics of the eye changes with accommodation can be helpful to understand the origin of accommodative dysfunctions.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2019 and by the project PTDC/FISOTI/31486/2017 and POCI-01-0145-FEDER-031486. The author Jessica Gomes is also supported by the PhD grant 2020.08737.BD from FCT