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Institute
Purpose: Although the frequency in which practitioners are fitting scleral
contact lenses is increasing, the recommendation for proper tear layer depth
(thickness) varies amongst experts. The main goal of this paper is to clinically
verify the effect of varying tear layer depths on induced corneal edema during
lens wear.
Methods: Ten subjects with healthy eyes were fitted with scleral lenses on their
right eye. Each of them was fit with two different lenses: one with an apical
clearance of 200 μm and another with an apical clearance of 600 μm. They wore
the lenses for 8 hours on two different days, with at least a one week wash-out
period. Lenses were applied at 8 a.m. on each of the testing days. Pachymetry
measurements were taken one day prior to lens wear at 4 p.m., on the day of
wear prior to lens application, and after removal of the lenses at 4 p.m.
Measurements were collected using both the Pentacam® HR Corneal
Tomographer, as well as the Visante Anterior Segment Optical Coherence
Tomographer (OCT). The apical clearance was measured using the
Visante OCT at two intervals during the test day: immediately after application of
the lens and immediately prior to the removal of the lens.
Results: In this study, there was found to be no significant difference in corneal
edematous response during lens wear between the two test groups. The study
shows that the eyes with the lenses have a statistically significantly thicker
cornea compared to the non-lens-wearing eye after wearing either lens for 8
hours, lying within clinically and physiologically acceptable limits.
Conclusion: Our clinical results do not correlate with current theoretical
calculations, which predict a greater amount of corneal swelling with increasing
tear layer thickness. It has to be evaluated if the effect on corneal edema
changes with longer wearing periods, larger samples or other influences.
Key words: scleral (contact) lens, corneal edema, pachymetry, tear layer
thickness, vaulting, apical clearance
Purpose: Recent studies found a reduction of myopia progression with multifocal contact lenses, however, with yet unclear mechanism. This raises the hypothesis that the addition zones of the multifocal contact lenses induce myopic defocus on the retina, which consequentially leads to choroidal thickening and therefore inhibited eye growth. We tested the effect of the optical design of multifocal contact lenses on choroidal thickness.
Methods: 18 myopic students wore four different contact lenses ((1) single-vision lens corrected for distance, (2) single-vision lens with +2.50 D full-field defocus, (3) “Multifocal center-distance” design, addition +2.50 D, (4) “Multifocal center-near” design, addition +2.50 D) for each 30 minutes on their right eye. Automated analysis of the macular choroidal thickness, vitreous chamber depth and eccentric photorefraction were performed before and after each contact lens.
Results: Choroidal thickness and vitreous chamber depth showed no significant differences to baseline with none of the contact lenses. Choroidal thickness increased the most with the “Multifocal center-distance” and the full-field defocus lens, followed by the “Multifocal center-near” and the single-vision contact lens (+2.1 ± 11.1 μm, +2.0 ± 11.1 μm, +1.6 ± 11.3 μm, +0.9 ± 11.2 μm, respectively). The “Multifocal center-distance” design showed an overall more myopic refractive profile than the other lenses. Changes of vitreous chamber depth occurred in anti-phase to these of choroidal thickness.
Conclusion: Multifocal contact lenses have no significant influence on choroidal thickness and after short-term wear. Therefore, it is assumed that it is not the main contributor to the protective effect of multifocal contact lenses in myopia control.
Comparing axial eye length to other physiological properties of the eye, body height and the head
(2022)
Purpose: To find, if there is any relationship between axial eye length and other physiological properties of the eye (horizontal corneal diameter, average corneal radius, central corneal thickness, objective spherical equivalent, pupillary distance), body height, and head size. Can any of these correlations eventually complement models in myopia progression or be the model for further research.
Telemedicine assisted non-mydriatic Fundus imaging for detection of Diabetic Retinopathy in Colombia
(2022)
Diabetic retinopathy (DR) is a well-recognized complication of diabetes mellitus where retinal function is compromised. It is considered a public health disease and is the fifth leading cause of visual impairment worldwide. But although the worldwide prevalence is continually increasing, little is known about the frequency of this disease in Colombia, South America. On the other hand, telemedicine is presented as a tool that has the potential to improve access to health care services, for remote or rural populations, and for those who have limited access due to physical or other disabilities. Recent technological advances in telecommunication and digital imaging, including fundus photography, telemedicine represents a valuable clinical aid for the documentation and diagnosis of ocular pathologies, and therefore helps to minimize adverse outcomes associated with chronic disease such as diabetes mellitus.
Purpose: The aim is to be able to advise patients on the choice of sports and exercises regarding the effects on the intraocular pressure.
Methods: The search engines Google Scholar and PubMed were used to search for suitable studies. The studies were summarized, and the most important data were collected in one table for each study. The effect on the IOP was extracted or, if not given in the article, calculated by the difference of means of the IOP after or during exercise, and the baseline IOP before, whenever these values were available.
Findings: A total of 47 studies out of the years 1990 to 2020 that investigated the influence on the IOP of the most popular sports actively practiced in Germany were reviewed and summarized: twelve for running, sixteen for fitness/ weight training, one for swimming/diving, twelve for cycling, four for hiking, and two for yoga.
Conclusions: Throughout all studies and sports it was seen that physical fitness stabilized the IOP. Higher
intensity of exercise led to higher fluctuations of the IOP. Moderate endurance training keeps the IOP fluctuations low and may lead to a lower baseline IOP if practiced on a regular base. Fitness and weight training lead to fluctuations of the IOP in a pronounced manner when performed at moderate and high intensity. Therefore, only a moderate training can be recommended if there is need to keep the IOP stable. Isometric exercise is not recommended as it provokes a rise of the IOP even when performed with light loads. The Valsalva Maneuver should always be avoided as it leads to additional fluctuations of the IOP. Also, the IOP behaved more stable during resistance training when higher fitness was present.
The direct ophthalmoscope is a retinal screening tool that has been in existence and development for more than 150 years, yet, the rapid influence of technological evolution in screening tools, has left the direct ophthalmoscope untouched. The main purpose of this master thesis is to determine if the direct ophthalmoscope has reached its maximum potential of development and, additionally, to determine if a further development, including a more electronic input, would be feasible.
The purpose of this master’s thesis is to evaluate the efficiency of state-provided eye exams as part of regular health check-ups for children aged between 6 and 18. This paper examines how capable these eye exams are at detecting reduced visual acuity and other vision related problems. It also investigates whether older children are better at noticing vision related problems then their younger peers. The results are obtained by a comprehensive questionnaire.
Purpose
The purpose of this study was to evaluate the validity of the iPad Aniseikonia Test for
measurement size lens-induced aniseikonia. The iPad Aniseikonia Test is a new
computer-based test designed for measuring aniseikonia in vertical direction. The iPad
Test uses red-green anaglyphs.
Methods
Aniseikonia was induced in 21 subjects by means of afocal size lenses. Resulting
aniseikonia was measured in vertical direction by the iPad Aniseikonia Test. The
measurement was performed in dark condition with appropriate correction of refractive
error. All subject were patients with normal vision with no anisometropia or other
ocular problem.
Results:
Afocal size lenses of known magnification were used to induce aniseikonia. 5
measurements were taken in each subject, ranging from zero to 7 % magnification.
When using the regression analysis, the slope of the fitted line significantly differs from
1. The average slope of regression line is 0,58.
Conclusions:
Only moderate accuracy was found for tested target size and orientation. In all cases the
iPad Aniseikonia Test underestimates the level of aniseikonia. However for gross
assessment of anisometropia in clinical practice it could be successfully used. Further
study with different target size should be addressed.
The purpose of this master thesis is to make a manual on cataracts so that optometrists in the Republic of Croatia have in one place everything about the causes, diagnosis, and treatment of cataracts. According to the World Health Organization cataract is one of the leading causes of vision impairment in the world. By properly diagnosing the type of cataract, we provide patients with a better quality of life and a visual aid with which they will achieve maximum visual acuity. This master’s thesis will summarize all the knowledge from the master's degree in Aalen in order to get a broader picture of the formation of cataracts. On daily basis optometrists encounter cataract pathology, the goal is to better understand what affects cataract formation, from drugs to systemic diseases, and to ultimately help the client see better after resolving cataract pathology.
A good stereopsis (depth perception) is needed in everyday life, regardless whether a person is a professional driver or chef. Good estimation of distance, and of what is further and what closer, could mean the difference between a crushed and a whole car or between a bloody and a healthy finger. The main theme of this Master thesis is detect and quantify major factors in depth perception. Do the younger estimate the depth better than the older; do they have better depth perception with greater or smaller pupil distance; does depth perception depend on gender; what happens with stereopsis when vision is fogged by +0,5 and +1,0 D? These are the questions dealt with in this Master thesis.
To answer these questions measurements were made on 51 subjects (mean age 45,0 +/- 13,32 years) of whom 25 were women, mean age 45,5 +/-13,55 years (12 with PD<62 mm, mean and 13 with PD>66 mm) and 26 men, mean age 44,4 +/- 13,34 years (13 with PD<62 mm and, 13 with PD >66 mm). Each of these four groups was further divided by age (one in range 20 to 35 years and second in range 50 to 65 years).
The measurements were made with a few assumptions. The first assumption was that stereopsis is in direct correlation with visual acuity, the second assumption was that persons with bigger interpupillar distance have better stereopsis, and the third assumption was that with age the stereopsis ability decreases.
The measurements were done with modified Frisby–Davis test expanded from four geometrical shapes to twenty-five circles. The stereopsis was measured with full refractive correction at 4,5 and 3,0 meters. Later, stereopsis was measured with fogging with +0,5 and +1,0 D at the 4,5 and 3,0 meter distances.
Statistically there is no correlation (or very weak) between stereopsis and the visual acuity for whole group of 51 test persons, but if only young test persons are taken in consideration, the correlation becomes significant, r(20)=0,566, p=0,009 at 4,5 m and r(20)=0,456, p=0,043 at 3,0 m and that matches the assumption. Stereopsis is in no or weak positive correlation with pupil distance r(51)=0,059, p=0,679, which is in total contrast to the assumption. Stereopsis is in positive correlation with age at 4,5 meters measuring distance, r(51)=0,371, p=0,007, which corresponds to assumption. In addition, stereopsis is better in females than in males by 32,5%.
Based on the results it can be concluded that the stereopsis is in negative correlation with age, in positive correlation with visual acuity, females have better stereopsis than males and statistically, the correlation between stereopsis and pupil distance (PD) has not been proved. The most important conclusion is that the decreased visual acuity brings significant fall of stereopsis. A deficit in refraction of -0,50 D decreases stereo acuity by about 90% (nearly 2x) and a deficit of -1,0 D decreases stereo acuity by about 220% (about 3x).
Keywords: Stereopsis, stereo acuity, depth perception, pupil distance (PD), visual acuity (VA).