Pierre Forcier

Correlation of an exercise-induced increase in systemic circulation with neural retinal function in humans

Although the effects of physical exertion on intraocular pressure and systemic blood pressure are well established, the retinal response to such physiologic stress has not been examined. We studied the effect of short-term intense exercise on the principal waves in the scotopic and photopic flash electroretinograms, as well as the lower-amplitude oscillatory potentials. Sixteen healthy volunteers between 20 and 30 years of age participated in this experiment. The electroretinograms and oscillatory potentials were recorded with a Nicolet CA-1000 clinical averager, using DTL-type fiber electrodes. All retinal potentials were taken immediately before and after a minimum 20-min period of stationary bicycling that increased the heart rate to about 140 beats per minute. The electroretinograms were recorded from eyes with dilated pupils, 10 min after white-light adaptation of the right eye, and 30 min after dark adaptation of the left eye. Red flashes and dim white flashes were used to elicit photopic and scotopic electroretinograms, respectively. While no changes were recorded for any of the electroretinogram components recorded under photopic conditions, the amplitude of OP5 was decreased and the implicit time of OP4 was delayed after exercise for scotopic conditions. We concluded that exercise caused component-specific changes in the scotopic oscillatory potentials. Since it is well known that oscillatory potentials are vulnerable to ischemia, scotopic oscillatory potentials may be used as simple noninvasive indices of the reactivity of the retinal vascular autoregulatory system during exercise.

Macular hemodynamic responses to short-term acute exercise in young healthy adults

We investigated the effects of vigorous exercise on blood flow in the macular vasculature. The velocity and density of entoptically viewed leukocytes in the paramacular retinal capillaries were measured with an Oculix BFS-2000 blue field simulator in 18 healthy adults first at rest, and then after 20 min of exercise. Exercise typically increased the density of leukocytes with more variable effects on their velocity. When leukocyte velocity and density were factored together, macular blood flow increased only marginally after exercise. We conclude that retinal blood flow in the macula is subject to the influence of autoregulatory mechanisms presumably to sustain normal central visual function during increased systemic blood flow.

Contribution of soft lenses of various powers to the optics of a piggy-back system on regular corneas.

PURPOSE This study aims to report on the measured in vivo contribution of soft lenses of various powers to the optics of a piggyback system (PBS). METHODS This prospective, non-dispensing clinical study was conducted on regular wearers of contact lenses who showed regular corneal profiles. Subjects were masked to the products used. The study involved the use of a spherical soft lens of three different powers in a PBS, used as a carrier for a rigid gas permeable lens. Baseline data were collected and soft lenses were then fitted on both eyes of each subject. Both lenses were assessed for position and movement. Over-refraction was obtained. Soft lens power contribution to the optics (SLPC) of a PBS system was estimated by computing initial ametropia, lacrymal lens, rigid lens powers and over-refraction. A set of data on one eye was kept, for each subject, for statistical analysis. RESULTS Thirty subjects (12 males, 18 females), aged 24.4 (±4.5) years, were enrolled. The use of plus powered soft lenses enhanced initial RGP lens centration. Once optimal fit was achieved, all lenses showed normal movement. SLPC represented 21.3% of the initial soft lens power when using a -6.00 carrier, and 20.6% for a +6.00. A +0.50 did not contribute to any power induced in the system. These results are generally in accordance with theoretical model developed in the past. CONCLUSION On average, except for the low-powered carrier, the use of a spherical soft lens provided 20.9% of its marked power. To achieve better results, the use of a plus-powered carrier is recommended.

Comparing two different daily disposable lenses for improving discomfort related to contact lens wear.

PURPOSE This study aimed to compare two daily disposable lenses to reduce lens-induced discomfort (CLD) among different populations of symptomatic wearers. METHODS This was a multicenter, crossover, study. Subjects were contact lens wearers reporting CLD. Subjects (76) were randomly assigned to wear Nelfilcon A (NF) then Delefilcon A (DF)- group A- or vice-versa (group B). Tear break-up time (TBUT), corneal (CS) and conjunctival staining (CJS) were graded at every visit. Subjectssymptoms were evaluated with Contact Lens Dry Eye Questionnaire (CLDEQ-8) and a research questionnaire (Université de Montréal). RESULTS Compared to baseline (BL), TBUT did not vary (BL) 6.7+2.1s vs. 6.7+1.8s (NF) vs. 6.4+1.9 (DF) (F=1.69; p=0.201) NF wearers were more at risk of developing moderate CJS (odds ratio 14.324; 95% CI 3.103-66.126) and more likely to show increased CS (odds ratio 8.754; 95% CI 2.181-35.146). Comfortable hours of wear reported at BL (7.6+2.3h) did not improve significantly with NF lenses (8.5+ 2.6h; F=1.095; p=0.394) but increased by 22% with DF lenses (10.7+3.0h; F=2.434; p=0.031). The total CLDEQ-8 score was improved with DF lenses (BL 17.2 vs. NF 16.1, p=0.397; vs. DF 8.3, p<0.001), especially on more symptomatic subjects. In the end, 92% of patients preferred to switch over DD lenses, 78% selecting DF material for the future. CONCLUSION Outcome from switching CLD wearers to DD lenses is material related. It seems that initial severity of the symptoms could be also a factor to consider.

Prevalence of asymptomatic ocular conditions in subjects with refractive-based symptoms

BACKGROUND This study aims to determine the overall prevalence of ocular conditions in a population from 19 to 64 years old, presenting with refractive-based symptoms only. Results could impact clinical standard of eye care on a similar population. METHODS This is a retrospective study on patients seen for an eye examination at the Clinique Universitaire de la Vision (CUV), between January 2007 and 2009. Files of individuals who presented with refractive symptoms were only selected and classified by file number. Then, every third file from the beginning was kept and reviewed by a reader. A second reader did the same with every third file from the end. Both readers were trained to use the same analysis grid to classify the diagnosed ocular conditions. In the case of multiple findings, the most severe condition was considered. The overall prevalence of ocular conditions was determined by calculating their occurrence divided by the number of files analyzed. RESULTS A total of 860 charts were analyzed. In 26.1% of the cases an ocular condition was diagnosed. This work establishes a higher prevalence of ocular conditions compared to another study conducted in Canada in the past. This difference can be explained by a different analytical methodology and by the fact that all examinations, in this study, were made under pupillary dilation. CONCLUSION The presence of ocular conditions in 26% of asymptomatic patients supports the need to assess ocular health under pupil dilation as part of any eye examination. However, further cost-to-benefit analysis is required before establishing such a recommendation.