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PubMed2001

Laser in situ keratomileusis after penetrating keratoplasty.

PURPOSE: To assess the outcomes of laser in situ keratomileusis (LASIK) after penetrating keratoplasty (PKP). SETTING: Hospital de Clínicas de Porto Alegre, Department of Ophthalmology, Federal University of Rio Grande do Sul, Porto Alegre, RS, Brazil. METHODS: Fourteen eyes of 13 patients who had LASIK after PKP were retrospectively reviewed. The interval between LASIK and PKP was at least 1 year, and the follow-up after LASIK was also at least 1 year. All patients had a stable refractive error for a minimum of 6 months after all sutures were removed, regular and symmetric topographic astigmatism, and a minimal ultrasonic central corneal pachymetry of 500 microm. The Chiron Automatic Corneal Shaper and the Meditec Aesculap MEL 60 excimer laser were used. RESULTS: At 12 months, mean myopia decreased from -5.33 diopters (D) +/- 4.22 (SD) to 0.19 +/- 1.71 D, mean hyperopia decreased from +5.04 +/- 3.32 D to + 0.42 +/- 0.46 D, and mean astigmatism decreased from 5.37 +/- 2.12 D to 2.82 +/- 2.42 D (47.5% of mean percentage reduction). Retreatment was necessary in 42.9% of eyes because of cylindrical undercorrection. Uncorrected visual acuity improved in 11 eyes (78.6%). Best spectacle-corrected visual acuity improved in 6 eyes (42.8%) and was maintained in 4 eyes (28.6%); 5 eyes (35.7%) lost 1 Snellen line. Intraoperative complications included 1 buttonhole flap. Postoperative complications included interface epithelial ingrowth at the periphery (2 eyes) and pseudophakic retinal detachment 2 years after LASIK (1 eye). CONCLUSION: Laser in situ keratomileusis after PKP safely and predictably corrected the spherical component of the refraction. However, the predictability of LASIK in correcting post-PKP astigmatism was poor.

Adult↗
PubMed2000

The activities of daily vision scale: a useful tool to assess fall risk in older adults with vision impairment.

OBJECTIVE: To evaluate the validity of the Activities of Daily Vision Scale (ADVS) as a tool to assess fall risk in older adults with vision impairment. DESIGN: Cross-sectional assessments of visual function and retrospective collection of fall data. SETTING: The outpatient medical clinics of an academic tertiary care community hospital. PARTICIPANTS: Randomly selected sample (n = 143) of older (> or = 65 years) patients seen at the outpatient medical clinics at Nassau County Medical Center in Long Island, New York. These patients had one or more of five ocular conditions: refractive errors (n = 90), cataracts (n = 77), glaucoma (n = 29), diabetic retinopathy (n = 19), and/or macular degeneration (n = 6). MEASUREMENTS: Visual function, assessed using the ADVS, demonstrated scores ranging from 0 (marked visual disability) to 100 (no visual difficulty). Fall history and the presence of eye disease were based on the self-recall of patients. Fall history was assessed retrospectively over a 1-year period from the time of the interview. RESULTS: Thirteen percent of the subjects reported having one or more falls during the 1-year period before the time of the interview. These subjects scored significantly lower on the ADVS compared with the scores of the group that did not report falls (74 +/- 22 vs 85 +/- 14, P < .01). Using a cutoff score of 90 points (10% loss of visual function on the ADVS), the ADVS had a 67% sensitivity in identifying those patients who had falls. Among the patients with glaucoma and those with diabetic retinopathy, the ADVS had a 100% sensitivity in identifying those patients who reported a history of falls. In patients with cataracts and refractive errors, the ADVS had a sensitivity of 82% and 64%, respectively, in identifying patients with a history of falls. The number of falls reported by the subjects showed no relationship with the ADVS scores. CONCLUSION: The results from this study suggest that the ADVS may prove to be a useful tool to assess fall risk in older adults with vision impairment, especially in those persons with glaucoma, diabetic retinopathy, and/or cataracts.

Accidental Falls↗
PubMed2002

Progress in the development of a synthetic corneal onlay.

PURPOSE: This study evaluated an improved perfluoropolyether polymer formulation designed for use as a corneal onlay to correct refractive error. METHODS: Collagen I coated perfluoropolyether lenticules were implanted in feline corneas exposing a 6-mm diameter area of lenticule surface for epithelial growth. A parallel series of sham-wounded corneas were also studied. All corneas were monitored clinically for 4 or 8 weeks after surgery when animals were terminated and corneas used for histology with light and electron microscopy. RESULTS: Postoperative epithelial growth began on days 1 and 2. Lenticule surfaces were fully epithelialized by days 5 to 11. Corneas remained clear, and the lenticules maintained epithelial cover until the designated time points. Histology of the implanted corneas showed that the lenticules were well tolerated by the cornea. Each lenticule was fully covered by a multilayered epithelium with microvilli, desmosomes, and a differentiated basal cell layer. Epithelial adhesive structures (basal lamina, hemidesmosomes, and anchoring fibrils) had assembled at the tissue-lenticule interface. CONCLUSIONS: Collagen coated perfluoropolyether lenticules implanted in the feline cornea supported the growth of a stable stratified squamous epithelium. These encouraging results are a step further in the development of a corneal onlay for correction of refractive error.

Animals↗
PubMed2002

The relationship between self-esteem of myopic children and ocular and demographic characteristics.

PURPOSE: To evaluate self-esteem and its relationship with various ocular and demographic characteristics in 469 myopic children participating in the Correction of Myopia Evaluation Trial (COMET), an ongoing, randomized, multicenter clinical trial designed to evaluate the effects of progressive addition lenses vs. single vision lenses on the progression of juvenile-onset myopia. METHODS: Baseline data collection included demographic information, refractive error measurements, parent-reported myopia history, child-reported visual symptoms, and self-esteem in several areas (scholastic/athletic competence, physical appearance, social acceptance, behavioral conduct, and global self-worth) as measured by the Self-Perception Profile for Children. Univariate and multiple regression analyses were used to identify factors associated with self-esteem. RESULTS: The Self-Perception Profile for Children is a reliable measure of self-esteem in COMET children as indicated by the high internal consistency reliabilities (0.74 to 0.81) obtained for the various domains. COMET children's mean self-esteem scores ranged from 2.72 +/- 0.69 for athletic competence to 3.36 +/- 0.56 for global self-worth and were similar to normative samples. Multiple regression analyses showed that less symptomatic children had higher self-esteem in all areas (p < 0.05), except athletic competence, after adjusting for other ocular and demographic characteristics. Self-esteem also varied significantly by age, gender, and ethnicity (p < 0.05). CONCLUSIONS: Baseline self-esteem is associated with visual symptoms, age, gender, and ethnicity, but not with magnitude of refractive error. Follow-up reports will assess whether there are changes in self-esteem associated with myopia progression and lens assignment.

Child↗
PubMed1995

Small letter contrast sensitivity: an alternative measure of visual resolution for aviation candidates.

Exceptional vision is needed to maintain high levels of aviation performance. Current standards for helicopter pilot training include superior visual acuity with minimal refractive error. Despite these demanding criteria, it is likely that visual ability varies among those who meet the standards for pilot training. A more complete knowledge of visual capabilities in these individuals will allow us to better correlate vision with performance and to develop more incisive criteria for selection. The purpose of this study was to investigate an alternative test of visual resolution for aviation candidates using small letter contrast sensitivity (SLCS). Computer-generated letter charts were used to measure visual acuity (VA) and SLCS in 16 candidates who had satisfied military vision standards for pilot training. The acuity and contrast charts varied, by line, in equal log steps such that the letter recognition task was comparable for the two types of measurement. VA and SLCS were highly correlated in these subjects, indicating that the two tests measure similar aspects of visual resolution. Scores were distributed across two lines on the acuity chart, but across four lines on the contrast chart, suggesting that SLCS offers a more discriminating test of resolution. This assumption was confirmed in that SLCS was more highly correlated with small amounts of refractive error in the candidates tested. SLCS offers a sensitive, adjunctive measure of visual resolution which may be useful for identifying the unique visual abilities required for aviation.

Analysis of Variance↗
PubMed2001

Phototherapeutic keratectomy for decentration and central islands after photorefractive keratectomy.

PURPOSE: To determine visual outcomes after treatment of decentration and central islands occurring after photorefractive keratectomy (PRK). DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Patients (n = 14) who exhibited decentration or central islands after PRK and photoastigmatic keratectomy (PARK). METHODS: Fourteen eyes with post-PRK decentration (group I) or central islands (group II) were treated by transepithelial phototherapeutic keratectomy guided by epithelial fluorescence without modulating agents, and subsequently were treated with PRK or PARK. Mean follow-up time was 9 months (range, 45 days-21 months). MAIN OUTCOME MEASURES: We analyzed pre- and postoperative keratometry, refractive errors, uncorrected visual acuity (UCVA), best-corrected visual acuity, and haze. In group I, we also measured pre- and postoperative decentration; in group II, we compared pre- and postoperative central island power. RESULTS: Group I showed improvement in centration (P = 0.003). Group II showed decreased central island power (P = 0.18). -LogMAR UCVA improved from 0.59 (20/80(+1)) to 0.17 (20/30) (P = 0.03) and from 0.74 (20/100(-1)) to 0.21 (20/30(-1)) (P = 0.01) after retreatment of groups I and II, respectively. CONCLUSIONS: Retreatment of patients having decentration and central islands after PRK results in improved visual outcomes.

Adult↗
PubMed1998

Baltimore Vision Screening Project. Phase 2.

BACKGROUND: Vision screening in preschool and school age children remains a valuable method of identifying potentially treatable visual abnormalities, as well as refractive errors in the school age population. A major difficulty in conducting these types of programs is the inconsistent follow-up encountered frequently in children identified by the screening program. The Baltimore Vision Screening Project was designed to address the issue of access to care for a group of inner city elementary school students by providing on-site evaluation and treatment. METHODS: A standard vision-screening protocol was administered to prekindergarten and kindergarten students attending an inner city elementary school and access to care provided at the school. Children identified by the screening were examined at the school, and appropriate treatment was prescribed. The second phase of the study details a return to the school 1 year after the initial screening. The purpose of this was to reassess the level of visual morbidity in this population and to evaluate the effects of providing treatment in the previous year. RESULTS: Two hundred eighty-five children were screened during the 1994-1995 school year. Visual morbidity statistics from the follow-up year were similar to those of the previous screening: 5.3% diagnosed with amblyopia, 3.2% with strabismus, and 7.4% with refractive errors. Forty of the 68 children identified, examined, and treated in the previous year still were attending the school during the follow-up investigation. Compliance with recommended treatment was 30% in this group, with only 20% of the students passing the vision screening the following year. CONCLUSIONS: The follow-up screening confirmed the presence of significant visual morbidity in this group of preschool and kindergarten students. Nearly two thirds of the students had not complied with the recommended treatment or spectacle wear or both, despite providing immediate access to this care through the vision-screening program.

Baltimore↗
PubMed2006

Accommodative facility in eyes with and without myopia.

PURPOSE: To compare accommodative facility in eyes with myopia to that in eyes with emmetropia or hyperopia and to determine whether accommodative facility can be used to predict an association with myopia. METHODS: In the Sydney Myopia Study, year-1 school children (6.7 +/- 0.4 years) were assessed for accommodative facility at distance (3 m) and near (33 cm) with semiautomated flippers. Spherical equivalent refractive error (RE) was defined as myopia (< or = -0.50 D), emmetropia (> -0.50 D, but < +1.50 D), and hyperopia (> or = +1.50 D) based on postcycloplegia readings. Only right eye data were considered. Differences between groups were analyzed with the Brown-Forsythe F test after adjustment for age and gender. Multiple comparisons were adjusted with the by the Games-Howell METHOD RESULTS: Of the 1328 right eyes assessed, 20 (1.5%) eyes were myopic, 977 (73.6%) were emmetropic, and 331 (24.9%) were hyperopic. At distance, mean facility was less for myopic eyes at 5.5 +/- 2.0 cycles per minute (cpm) in comparison to 6.9 +/- 1.7 cpm for eyes with emmetropia or hyperopia (P = 0.005). Myopic eyes recorded greater positive and negative accommodative response times than did emmetropic or hyperopic eyes (P < 0.05). There were no differences among the groups in near facility. The area under the receiver operating characteristic (ROC) curve for distance facility was 0.692 (P = 0.003, 95% CI, 0.580-0.805). CONCLUSIONS: Myopic eyes have reduced accommodative facility at distance, and accommodative responsiveness to both positive and negative defocus is slow. However, accommodative facility as a test does not have sufficient power to discriminate eyes with myopia from other refractive errors.

Accommodation, Ocular↗
PubMed1999

Central bump-like opacity as a complication of high hyperopic photorefractive keratectomy.

PURPOSE: A new complication is reported in association with high hyperopic excimer laser photorefractive keratectomy. METHODS: One thousand consecutive eyes were treated with a Meditec MEL-60 excimer laser (Meditec Inc, Heroldsberg, Germany) for hyperopic refractive error between +1 diopters and +7 diopters. RESULTS: Three eyes with high hyperopic corrections between +5 and +6 diopters had a central, round bump-like subepithelial scar develop 1 month after hyperopic photorefractive keratectomy, which reduced the uncorrected and spectacle-corrected visual acuity. CONCLUSION: Central bump-like opacity is a new, visually significant complication of unknown origin associated with high hyperopic photorefractive keratectomy. Possible causes of this complication include drying and edema of the cornea as a result of prolonged exposure, interruption of the peripheral superficial nerve plexus affecting the central anterior stroma, and abnormal epithelial or tear film function resulting from excessive central steeping.

Adult↗
PubMed2004

Utilization of eye care services by Victorians likely to benefit from eye care.

AIM: To assess the utilization of eye care services by Australians most likely to benefit from eye assessment. METHODS: The Melbourne Visual Impairment Project was a population-based study that collected demographic, health and vision-related information including use of eye care services. A standardized detailed ophthalmic examination was performed. Utilization of eye care services by those who might most benefit from eye care was assessed and compared to the general population. These participants include those with undiagnosed glaucoma, unoperated visually significant cataract, undercorrected refractive error, diabetes mellitus, age-related macular degeneration and visual acuity < 6/12. Sociodemographic characteristics were assessed for their influence on eye care utilization among these participants. RESULTS: A total of 4744 urban and rural residents participated (86% of those eligible) and 4612 (83% of total eligible) of these had a complete data set for the use of eye care services and were included. There were 933 participants (20.2%) who did not report eye assessment in the previous 5 years, and 891 participants (19.3%) had one or more aforementioned conditions potentially benefiting from eye care. Of these, between 34.4% and 59.4% reported no examination in the previous year and between 9% and 25% reported no examination within the previous 5 years. These participants were more likely to seek eye care within the short term (1 year) if they had a family history of eye disease, otherwise a noticed change in vision was the main influence in the longer term (2-5 years). Male participants, younger participants and those whose main spoken language was not English were less likely to seek eye care in the longer term. CONCLUSIONS: In Victoria 19% of those >40 years of age have potentially unmanaged eye disease including glaucoma, unoperated visually significant cataract, undercorrected refractive error, age-related macular degeneration, diabetes mellitus or visual acuity < 6/12. A substantial proportion of these report no eye assessment in the previous 1, 2 or 5 years or ever before. Younger age, male sex and main language other than English make assessment less likely. Many may have these conditions despite having had a recent eye assessment.

Adult↗
PubMedDate not supplied

Viewing distance with minimum heterophoria.

BACKGROUND: The purposes of this study are to determine the viewing distance with minimum heterophoria and its relationship with refractive error and the resting position of accommodation. METHODS: The heterophoria and the accommodation responses of 36 optometry students (25 emmetropes and 11 myopes) were tested. Heterophoria was measured with the Free-Space Heterophoria Card at five different viewing distances (25 cm, 33 cm, 50 cm, 100 cm and 300 cm). The dioptric viewing distance with minimum heterophoria for each individual was estimated from the graph, where heterophoria in prism dioptres was plotted against viewing distance in centimetres. The Canon R-1 autore-fractor was used to determine the accommodation response at six different viewing distances (25 cm, 33 cm, 50 cm, 100 cm, 300 cm and 600 cm). The resting position of accommodation for each individual was estimated from the graph where the accommodative stimulus in dioptres was plotted against the accommodative response in dioptres. RESULTS: The dioptric viewing distance with minimum heterophoria ranges from 0.003 D to 0.65 D in emmetropes and ranges from 0.03 D to 2.36 D in myopes. There is no difference in the dioptric viewing distance with minimum heterophoria between myopes and emmetropes. Our results show a possible but not significant correlation between the dioptric viewing distance with minimum heterophoria and the resting position of accommodation. CONCLUSIONS: The viewing distance with minimum heterophoria is not affected by refractive error (stable early-onset myopia) and is poorly correlated with the resting position of accommodation.

Journal Article↗
PubMed2001

The Berkeley Contact Lens Extended Wear Study. Part II : Clinical results.

OBJECTIVE: To describe the principal clinical outcomes associated with 12 months use of rigid gas-permeable (RGP) extended wear contact lenses and address two primary study questions: (1) does extended wear (EW) of high oxygen transmissibility (Dk/t) RGP lenses reduce the incidence of ocular complications, and (2) does the wearing of high-Dk/t lenses reduce the rate of failure to maintain 6-night RGPEW over 12 months? DESIGN: A randomized, concurrently controlled clinical trial. INTERVENTION: Subjects who adapted to EW with high Dk (oxygen permeability) RGP lenses were randomized to either high Dk or medium-Dk RGP lenses for 12 months of 6-night EW. MAIN OUTCOME MEASURES: Contact lens-associated keratopathies (CLAK), changes in refractive error and corneal curvature, and survival in EW. RESULTS: Two hundred one subjects were randomized to medium or high-Dk lenses for 12 months of EW. Sixty-two percent of the subjects in each group completed 12 months of EW; however, the probability of failure was significantly greater for the medium-Dk group. Although the risk of complications was similar for the two groups, the number of CLAK events that led to termination were 16 versus 5 for the medium-Dk and high-Dk groups, respectively. This suggests that the type of adverse response or the inability to reverse an adverse event was different for the group being exposed to the lower oxygen dose. CONCLUSIONS: The level of oxygen available to the cornea has a significant impact on maintaining successful RGP extended contact lens wear, but not on the initial onset of CLAK. The number of clinical events leading to termination was substantially higher for the medium Dk group, which suggests that corneal hypoxia is an important factor in the development of CLAK. Although overnight contact lens wear should be recommended with caution and carefully monitored for early detection of ocular complications, it appears that high-Dk RGP lenses can be a safe and effective treatment for correction of refractive error for most individuals who can adapt to EW.

Adult↗
PubMed2002

Discriminant analysis formulas of optic nerve head parameters measured by confocal scanning laser tomography.

PURPOSE: To evaluate whether discriminant analysis formulas of optic disc variables measured by confocal laser scanning tomography can detect glaucomatous visual field defects, to compare the diagnostic precision of these formulas to detect glaucomatous visual field defects in different types of chronic open-angle glaucoma, and to assess whether gender or refractive error influence the results obtained by the formulas. METHODS: One hundred and sixty-one patients with perimetrically defined glaucomatous optic nerve damage and 194 healthy subjects were recruited. All patients underwent confocal laser scanning tomography of the optic disc. The data were analyzed with three linear discriminant analysis formulas (sectorial, Bathija, and Mikelberg) obtained in sets of data different from those used in the present study. RESULTS: The areas under the receiver-operating characteristic curves of the three formulas and of the cup shape measure as a single parameter ranged from 0.649 to 0.81 in the entire group, and the results did not change when age-matched eyes were considered (0.618-0.812). In each of the glaucoma subgroups with primary open-angle, pseudoexfoliative, and normal-pressure glaucoma, and additionally in the hyperopic, myopic, female, and male subgroups, the sectorial formula had the highest diagnostic precision and the highest correlation coefficients with the visual field indices, followed by the Bathija and Mikelberg formulas, without major differences between the subgroups. All three formulas were more effective than the cup shape measure as a single parameter. CONCLUSION: In the various chronic open-angle glaucomas, the sectorial and Bathija formulas tended to have higher diagnostic precision than the Mikelberg formula and the cup shape measure. Gender and refractive error do not markedly influence the diagnostic precision of the formulas tested. The scores of the formulas are mild indicators of the amount of glaucomatous visual field loss. All three formulas are superior to the single cup shape measure in the detection of glaucomatous optic nerve damage.

Adult↗
PubMed1996

Photorefractive keratectomy (PRK) in the military aviator: an aeromedical perspective.

Refractive surgery to visually rehabilitate refractive errors of the eye continues to evolve at a significant pace and is here to stay. The surgical manipulation of the cornea by carefully planned incisions, as in radial keratotomy, represented the first procedure to evolve for the correction of ametropia and is an area of continued active development and improvement. However, many concerns mitigate against this procedure in the aeromedical arena. More recently, photorefractive keratectomy using laser technology to ablate and recontour the corneal surface has emerged as a viable modality. This paper explores the aeromedical factors surrounding this new revolutionary procedure and discusses the issues relevant to evaluating its applicability to the modern military aviator as well as reviewing results of the latest clinical trials currently in progress. The goal is to provide the aeromedical community with the fundamental information required to formulate aeromedical decisions and policy-making in regard to a new procedure that is certain to have tremendous impact on the selection of future aircrew candidates.

Aerospace Medicine↗
PubMed2005

[Laser in situ keratomileusis (LASIK) and scanning laser ophthalmoscopy].

BACKGROUND: To determine the influence of Laser in situ keratomileusis (LASIK) on the measurements of retinal thickness and optic nerve head topography using the Retinal Thickness Analyzer (RTA). METHODS: RTA measurements were performed before and after LASIK. Forty-eight eyes of 25 healthy subjects were included. Mean age was 40.0+/-10.6 years. Mean preoperative refractive error (spherical equivalent) was -3.3+/-3.6 dpt, and 0.2+/-0.9dpt postoperatively. Correlation between ablation depth and duration and change of retinal thickness postoperatively was performed. All patients received a pachymetry preoperatively. RESULTS: Postoperatively, mean retinal nerve fiber layer thickness (MRNFL) and cross sectional area (RNFL cross section area) significantly decreased after LASIK (MRNFL preop: 0.18 mm, postop: 0.11 mm, P =0.026, RNFL cross section preop: 1.17 mm(2), postop: 0.71 mm(2), P =0.015). Ablation depth revealed a significant correlation with changes in retinal thickness measurements postoperatively (Delta MRNFL: Ablation depth, P =0.001, r=-0.5). Duration of the ablation was not significantly correlated to the MRNFL measurements postoperatively (P =0.27, r=-0.08). No correlation was found between the central corneal thickness and the change in retinal thickness after LASIK (P =0.51). CONCLUSION: Due to changes in corneal architecture after LASIK, measurements using RTA reveal a decrease in MRNFL and RNFL cross section area. These changes are likely artifacts. Further studies with a longer follow-up are desirable.

Adult↗
PubMedDate not supplied

Super vision: dream or reality.

PURPOSE: To present and evaluate the early clinical experience of laser in situ keratomileusis (LASIK) using the custom guided corneal ablation system by NIDEK, which includes an OPD-Scan, Final Fit program, and Nidek Multipoint EC-5000 excimer laser. METHODS: The OPD-Scan diagnostic system containing a scanning slit refractometer using skiascopic technology with simultaneous Placido disc corneal topography is described. The Final Fit program that converts the refractive error and topography data into custom algorithms to couple with the Nidek EC-5000 Multipoint excimer laser is explained. Thirty-eight cases of LASIK using the Nidek MK-2000 microkeratome and the Nidek Multipoint excimer laser with custom and conventional treatments are presented. Eyes were divided into two groups: LASIK custom group and LASIK conventional group. RESULTS: Predictability and attempted correction were similar in both groups. One month after surgery, all eyes were between +/-1 line of visual acuity. In the custom LASIK group there was a gain of one line in 50% and two lines of visual acuity in 25% of patients at 1 month after surgery. In the conventional LASIK group there was no gain of lines of visual acuity at 1 month. In the comparative group (one eye custom LASIK and the other eye conventional LASIK) there was data available for six patients (75%). At one month, all patients preferred the vision in their custom LASIK-treated eye. CONCLUSION: The Nidek LASIK custom and conventional treatments were safe and predictable. There was more accuracy, better visual acuity, and more subjective satisfaction in the custom LASIK custom treatment group.

Adult↗
PubMed2005

Contrast sensitivity of wildtype mice wearing diffusers or spectacle lenses, and the effect of atropine.

PURPOSE: To find out how spatial vision in mice is affected by wearing of spectacle lenses or diffusers, and by atropine eye drops. This information is necessary to determine which treatments could effectively induce refractive errors in young mice. METHODS: Whole-body optomotor responses were recorded by automated video analysis in freely ranging mice in a large rotating drum that was covered inside with vertical square-wave gratings with spatial frequencies of 0.03, 0.10 and 0.30 cyc/deg, both at "dim light" (0.10 cd/m(2)), and under photopic conditions (30 cd/m(2)). Contrast thresholds were determined by varying the contrasts of the gratings. Mice wore either no lenses, or binocular plano lenses, or lenses with powers ranging from +25 D to -25 D, or diffusers. In another experiment, contrast thresholds were determined 30 min after binocular installation of one drop of 1% atropine solution which is known to suppress myopia development in other animal models. RESULTS: The range of spatial frequencies, at which the mice still responded to stripes with less than the maximal grating contrast, was rather small. At 0.03 cyc/deg, the mice responded to stripes with low contrast down to 24%. At 0.10 cyc/deg, the minimal contrast was 45%, but at 0.30 cyc/deg, only the maximum contrast elicited a significant response. In dim light, spatial vision was severely impaired and only the lowest spatial frequencies, presented at the highest contrast (91%), were detected. The whole-body optomotor response was largest with spectacle lens powers of plano diopters and +7D lenses. The magnitude of the response decreased symmetrically with increasing lens powers for both signs, providing information on the behavioral depth of field (a second-order fit through the data placed the extreme limits of a response at around +25 D and -25 D lens powers). Finally, atropine improved contrast sensitivity, at least at the lowest spatial frequency tested, a result that was previously obtained also in the chicken and could help to explain the inhibitory effect of atropine on myopia. CONCLUSIONS: The study shows that mice have sufficient spatial vision to respond to treatment with powerful spectacle lenses or diffusers. Accordingly, these devices should be effective in inducing refractive errors in this animal model, although primarily under photopic conditions.

Animals↗
PubMed2003

Effect of linoleic acid and gamma-linolenic acid on tear production, tear clearance and on the ocular surface after photorefractive keratectomy.

BACKGROUND: The aim of this study was to evaluate the effect of linoleic acid (LA) and gamma-linolenic acid (GLA), both precursors of PGE(1), on tear production, tear fluorescein clearance and on the ocular surface after photorefractive keratectomy (PRK). METHODS: Sixty subjects (age 25+/-10 years; refractive error -3+/-2 diopters (spherical equivalent), mean +/- standard deviation) undergoing PRK were enrolled. The inclusion criteria were: Schirmer 1 test >10 mm/5 min, no corneal fluorescein staining, low irritation symptoms (questionnaire score <5), standardised visual scale (to evaluate tear fluorescein clearance) score <3. Patients were randomly divided into two groups. One group of 31 subjects was treated once daily orally with tablets containing LA (28.5 mg) and GLA (15.1 mg) (from 3 days before PRK to 1 month after PRK). The control group (29 subjects) underwent PRK and received no treatment with LA and GLA. A symptoms questionnaire, Schirmer 1 test and fluorescein clearance test (FCT) using the standardised visual scale were performed before starting therapy (T(0)) and 30 days after PRK (T(1)). RESULTS: All patients completed the study. The Schirmer 1 test varied from 16.3+/-6.9 (T(0)) to 17.6+/-7.2 (T(1)) for the treated group and from 18.3+/-6.2 (T(0)) to 15.7+/-7.4 (T(1)) for the untreated group ( P<0.0001, two-tailed unpaired t-test). FCT was 1.9+/-0.6 at T(0) and 1.6+/-0.8 at T(1) for the treated group and 1.7+/-0.7 at T(0) and 2.0+/-0.9 at T(1) for the untreated group ( P<0.0001). The symptoms score was 4.7+/-1.9 at T(0) and 7.6+/-7.2 at T(1) for the treated group and 4.2+/-2.0 at T(0) and 10.1+/-7.6 at T(1) for the untreated group ( P<0.05). CONCLUSION: Reduced corneal sensitivity has already been proved after PRK. This could be the main reason for a decrease in tear production and for a reduced blinking rate leading to delayed tear clearance. The oral precursors of PGE(1), LA and GLA, could be helpful in increasing tear production and clearance after PRK.

Adult↗