The gradient filter test to assess amblyopia

A new technique, the gradient filter test, was developed for evaluating changes in the visual acuity of preverbal children undergoing treatment for amblyopia. The gradient filter test consists of a series of calibrated photographic fog filter and prism lenses. The combined prism-filter lenses are placed in front of the normal fixing eye. The greatest density (fogging value) filter that causes a switch in fixation from the amblyopic to the normal eye is noted. In both normal eyes of 20 nonamblyopic patients and the fellow (non-amblyopic) eyes of 20 amblyopic patients, visual acuity decreased as the density of the prism-filter lens increased. The gradient filter test accurately detected an improvement in visual acuity when compared with optotype measurements in eight patients undergoing occlusion therapy. The gradient filter test is a useful clinical tool that can assess changes in visual acuity in preverbal children who are being treated for amblyopia.     

Corneal deswelling response to hard and hydrogel extended wear lenses

The amount of initial corneal swelling and the time course of corneal deswelling were measured after overnight wear of several types of hard and hydrogel lenses. Deswelling occurred in the right eye with the lens still on the cornea. In the left eye the lens was removed at eye opening and left off the cornea during deswelling. For lenses of equal nominal oxygen transmissibility, hard lenses initially induced greater corneal swelling than hydrogel lenses after overnight wear. The rate of deswelling during the first 15 min after hard lens wear was significantly greater than a comparable time period after hydrogel lens wear both with the lenses on and off the eye during deswelling. After the initial 15 min of eye opening, no significant difference in the deswelling rates with hard or hydrogel lenses could be shown under either deswelling condition.     

青少年近视眼雾视配镜法的临床观察

目的 观察低度雾视配镜法的准确性、实用性.方法 眼视光门诊就诊91例(182只眼)青少年近视患者,男46例,女45例,年龄8～18岁,平均(12.82+0.51)岁,屈光度-0.50D～4.00D,均值(-2.18±0.14)D,裸眼视力(0.41±0.03).电脑验光后先戴比实际度数低1.00～2.00D的镜片,试戴30min后,检查视力.达不到1.0者再适当增加凹透镜度数、调整散光度数及散光轴使视力达到1.0,记录矫正度数.当日对低度雾视验光矫正试镜后患者用美多丽-P散瞳,每5min滴药一次,共6次,最后一次滴药40min后再次电脑验光,并插片矫正使视力达1.0.结果 美多丽-P散瞳前平均屈光度(-2.18±0.14)D,散瞳后平均屈光度(-1.94±0.14)D,二者配对t检验差异有显著意义(t-6.982;P＜0.001).美多丽-P散瞳配镜平均度数(-1.69±0.131)D,低度雾视配镜平均度数(-1.694±0.14)D.二者配对t检验差异无统计学意义(t-0.453;P＞0.05).结论 低度雾视配镜法与美多丽-P散瞳后配镜法等效球镜值差异无统计学意义.不同性别及年龄组患者分别用这两种方法配镜等效球镜差异无显著性.青少年近视眼雾视配镜法是科学、准确、实用、方便的验光配镜方法.对于8岁以上疑似近视眼的青少年可以用雾视配镜法代替美多丽-P快速散瞳配镜法.     

Effect of eyelid closure and overnight contact lens wear on viability of surface epithelial cells in rabbit cornea.

PURPOSE: To determine the effects of open, closed eye, and overnight contact lens wear on homeostatic epithelial surface cell death in the rabbit cornea. METHODS: One eye of each rabbit was either closed by eyelid suture or fitted with one of the following test contact lenses: (1) low Dk/t rigid gas permeable (RGP) lens, (2) hyper Dk/t RGP lens, (3) hyper Dk/t soft lens. The other eye served as a control. After 24 hours, whole corneas were carefully excised and immediately stained with a calcein-acetoxymethyl ester-ethidium homodimer viability assay to quantify the number of nonviable surface epithelial cells. In addition, exfoliated corneal epithelial cells were collected with an eye irrigation chamber to determine cell viability. RESULTS: In the normal cornea, open-eye conditions showed significantly more nonviable surface cells in the central cornea than in the periphery (p < 0.05). Overnight wear of all test lenses and eyelid closure induced significant decreases in the number of nonviable cells on the central corneal surface compared with controls (p < 0.05). All exfoliated corneal epithelial cells collected by eye irrigation were nonviable. CONCLUSION: In the rabbit model, overnight contact lens wear significantly downregulated spontaneous epithelial surface cell death independent of lens rigidity or material oxygen transmissibility. These effects were similar to eyelid closure without lens wear. Taken together, these results suggest that eyelid closure and the physical presence of the contact lens may protect against the shear stress forces exerted by eyelid blinking, which are believed to cause central surface cell death and subsequent exfoliation.     

Differences in contact lens-induced responses in the corneas of Asian and non-Asian subjects.

PURPOSE: To investigate ethnic differences in corneal endothelia bleb formation and corneal swelling during contact lens wear under closed-eye conditions, with the use of lenses of varying oxygen transmissibilities (Dk/L) in Asian and non-Asian subjects METHODS: Asian and non-Asian contact-lens naive subjects were fitted with one of four different types of contact lenses at each 20-minute session. During lens wear, the eyelid was closed Endothelial bleb formation was determined by specular microscopy or confocal microscopy immediately on eye opening. Some Asian contact-lens naive subjects were asked to wear one of two types of lenses (Dk/L values of 24 and 175) on each eye for 1 hour Corneal swelling was determined immediately after opening of the eyes. RESULTS: Asian subjects had a significantly higher degree of endothelial bleb formation than the non-Asian population for all closed eye conditions, p=0.0001. There was no significant difference in endothelial bleb formation between closed eves with or without lenses in the non-Asian population. There was a significantly higher degree of bleb formation with low Dk/L lenses, < or = 40, compared to high Dk/L lenses, > or = 110, in Asian subjects, p=0.0001. CONCLUSIONS: There is a significant difference between Asian and non-Asian subjects in the corneal response to stress. Under a closed eyelid only contact lenses with very high levels of Dk/L do not cause cornea stress in Asian patients.     

眼科工伤评残标准及其应用

本文介绍了眼科工伤评残分析标准，共分１０级４０条。对评残依据作了详细说明，如视功能（视力、视野）障碍的评定，立体视觉损伤程度的评价，非工伤致残眼在评残时的处理及职业眼病评残等。     

Omafilcon A (Proclear) soft contact lenses in a dry eye population.

PURPOSE: We conducted a 3-month, randomized, comparative cross-over study to evaluate the clinical performance of lenses manufactured from omafilcon A on subjects with signs and symptoms of dry eye. The subjects' own daily wear soft lenses were used as controls. METHODS: Seventy-six subjects with objective evidence of dry eye, as defined in the NEI/Industry Workshop Report 1995, were fit with either the omafilcon A lenses (Proclear) or new control lenses. Subjects wore the lenses for 6 weeks and then crossed over to bilateral wear of the other lenses for an additional 6 weeks. During each part of the study, we examined subjects at 1 week, 1 month, and 6 weeks. Signs and symptoms of dry eye were evaluated, and on-eye dehydration of the lens was assessed. RESULTS: When the subjects were wearing the omafilcon A lenses, there was a statistically significant improvement in a number of subjective parameters including comfort, dryness, frequency of eye irritation, and frequency of burning. We found significantly less on-eye dehydration of the lens and fluorescein corneal staining with the omafilcon A lenses. CONCLUSIONS: This study indicated that the daily wear of omafilcon A lenses provided better comfort, fewer symptoms, less on-eye dehydration, and less fluorescein corneal staining than other soft daily wear contact lenses in subjects with mild to moderate dry eye.     

Models of Oxygen Performance for the Static,Dynamic and Closed-lid Wear of Hydrogel Contact Lenses

ABSTRACT Contact lenses can restrict the amount of oxygen available to the cornea, often resulting in corneal oedema and visual dysfunction. Predictions of the likely physiological response of the cornea to contact lens wear can be facilitated by developing models of the oxygen performance characteristics of lenses. An equivalent oxygen technique was modified for use in the in vivo human eye; this technique involved equating the corneal oxygen demand following contact lens wear to the demand following exposure to known oxygen levels. A human eye model relating static equivalent oxygen percentages (EOP) to lens oxygen transmissibility (Dk/L) was derived using five hydrogel contact lenses; the discrepancies between this and other models could be explained in terms of the differing criteria upon which they were based. The effect of blinking on the EOP beneath hydrogel lenses was found to be minimal, confirming earlier findings. Attempts to derive an EOP v Dk/L model for hydrogel lens wear under closed-lid conditions were unsuccessful; individual variations in the supply of oxygen to the cornea under these conditions were thought to contribute to this failure. The validity of similar models was questioned in view of the simplified assumptions which were made.     

Safety goggles should be worn by Australian workers

Eye injuries in the workplace are a major cause of morbidity and disability, despite well publicised standards for industrial eye protection. A prospective survey of 51 patients presenting to a metropolitan emergency department with a work-related eye injury revealed that 32 injuries (63%), occurred to workers wearing some form of protective eye wear. However only seven (14%) were wearing eye protection that complied with the Australian Standard AS 1336 for occupational eye protection. Thirty-six patients (71 %) had suffered previous eye injuries at work. Most injuries were'caused by medium velocity particles generated by power tools, generally causing superficial corneal injury. We conclude that education to reduce the widespread misuse of safety glasses by tradespeople and trades assistants during tasks for which goggles are recommended could considerably reduce the incidence of occupational eye injuries.     

Treatment, material, care, and patient-related factors in contact lens-related dry eye

PURPOSE: To examine the effect of general contact lens and material characteristics, care solutions, treatment, and patient-related factors on contact lens-related dry eye. METHODS: The data were derived from the Contact Lens and Dry Eye Study, designed as a cross-sectional and nested case-control study including 360 subjects. In separate statistical models, logistic regression was used to examine general contact lens characteristics, specific hydrogel lens materials, care solutions, and patient-related factors associated with dry eye status (controlled for age, gender, and current treatments). RESULTS: Several factors were significantly associated with dry eye, including treatment factors such as a recent contact lens refitting (odds ratios [OR] = 5.75, 95% confidence intervals [CI] = 2.14 to 15.46) and use of artificial tears/rewetting drops (OR = 1.09, 95% CI = 1.02 to 1.16), in addition, currently worn materials including Food and Drug Administration (FDA) group II (OR = 2.98, 95% CI = 1.14 to 6.19) and IV (OR = 1.87, 95% CI = 1.08 to 3.24). Significant patient-related factors included decreased overall satisfaction (OR = 3.57, 95% CI = 2.08 to 5.88,), dry eye in the absence of contact lens wear (OR = 6.54, 95% CI = 2.57 to 16.62), reduced daily lens wear duration (OR = 1.16, 95% CI = 1.06 to 1.26), and reduced ability to wear lenses as long as desired (OR = 2.44, 95% CI = 1.30 to 4.54). Care solutions were not associated with contact lens-related dry eye. CONCLUSIONS: The strong association of common treatment factors with dry eye status in contact lens wearers suggests that these treatments are not entirely effective. The use of high water content materials was strongly related to dry eye in lens wearers, whereas care solutions were not. Contact lens-related dry eye was also associated with several patient-related factors such as greater ocular discomfort (without lenses), dissatisfaction, and inability to wear lenses for desired durations.     

Protein accumulation on disposable extended wear lenses

We investigated protein accumulation on disposable extended wear contact lenses. Fifteen volunteers were fit with one low water content, non-ionic lens (Bausch & Lomb's SeeQuence) randomly assigned to one eye and a high water content ionic lens (Vistakon's Acuvue) assigned to the fellow eye. During the first 7 weeks of extended wear the lenses were removed weekly for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of protein deposition, and replacement lenses were inserted. Four subjects completed additional test sessions of 1 minute, 15 minutes, 24 hours, and 1 week extended wear. Lysozyme accumulation, as measured by SDS-PAGE, increased with wearing times up to one week on all Acuvue lenses, but after 24 hours wear lysozyme accumulation did not increase on the SeeQuence lens. Proteins falling into the reported molecular weight ranges of albumin, PMFA, IgG, IgA (sec), lactoferrin and subunits of protein G were evident on all gels at 1 minute of wear, but these protein groups did not have a detectable increase in deposition after 24 hours wear for either the SeeQuence or the Acuvue lenses. In most cases, the protein accumulation evident from SDS-PAGE analysis was not observable by biomicroscopy using standard clinical methods. A few patients reported preference for the initial comfort and vision achieved by the Acuvue lens, but no preference was found after adaptation.     

Contact lens wear enhances adherence of Pseudomonas aeruginosa and binding of lectins to the cornea

Extended wear soft contact lenses are associated with an increased incidence of Pseudomonas aeruginosa keratitis. Because the first step in the pathogenesis of this disease is adherence of the microorganism to the corneal surface, we studied the effect of soft contact lens wear on the adherence of P. aeruginosa to the cornea. Rabbits were fitted for extended wear soft contact lenses in the left eye, and the right eye served as a control. Both eyes were then closed with a partial tarsorrhaphy. After 1-5 days of wear, the lenses were removed and the corneas of the left and right eye were removed. Differences in the number of adherent Pseudomonas and in lectin binding to lens-wearing corneas and non-lens-wearing corneas were determined. After 1, 3, and 5 days of soft contact lens wear, there was a significant increase in the number of P. aeruginosa adherent to the lens-wearing cornea. Three to eight times as many bacteria adhered to the lens-wearing eye as compared with the control eye (p less than 0.05). In addition, a soft contact lens placed in the eye followed by the immediate application of P. aeruginosa resulted in an eightfold increase in adherence of bacteria to the lens-wearing cornea (p less than 0.05). Lens wear also led to an increase in binding of concanavalin A (Con A), wheat germ agglutinin (WGA), and Maclura pomifera agglutinin (MPA) to surface epithelium covered by the lens. These corneal epithelial changes induced by extended wear soft contact lenses may provide some insight as to why soft contact lens wearers are predisposed to Pseudomonas keratitis.     

Surface interactions on hydrogel extended wear contact lenses: microflora and microfauna

The microbial flora and fauna of 25 high water content nonionic "soft" contact lenses worn by patients on an extended wear basis, 4 hand-cleaned patient-worn lenses, and 4 improperly maintained lenses were compared. Almost all the patient-worn lenses (24 of 25) were free of viable microorganisms, whereas all the hand-cleaned lenses (4 of 4) were contaminated with different microorganisms. This study showed that hand contact is a major source of microbial contamination of a lens and that usually the hand-transported microorganisms do not survive permanently on the lens in a healthy, normal eye. Improperly maintained lenses demonstrated pathogenic microbial associations. Proof of the eye's potent antimicrobial environment was demonstrated. Thus, microorganism-lens associations are largely due to lens handling and inappropriate maintenance regimens. Typically there are few microorganisms on an extended wear soft lens while it is being worn.     

Serious eye injury in badminton players.

Serious eye injury can occur in badminton players and may become more frequent. The causes and nature of such injuries in this sport in six patients are discussed. All were playing competitive doubles matches. Penetrating eye injury due to a shattered glass spectacle lens occurred. Players should be advised not to wear spectacles with glass lenses. Ocular protection in this sport is desirable, and the forward player should hold the racket in front of the face.     

Rigid gas-permeable vs. hydrogel contact lenses for extended wear

A clinical trial was conducted to compare the extended wear performance of rigid gas-permeable (RGP) contact lenses with that of soft lenses. Subjects were fitted with a RGP lens (Boston IV) in one eye and a soft lens (Bausch & Lomb "O" series) in the other eye, and wore them on an extended wear basis for up to 3 months. No subjects developed any acute adverse reactions in the RGP lens-wearing eye. After the initial adaptation period, subject acceptance of RGP extended wear in terms of vision and comfort was superior. The RGP lenses also induced less chronic hypoxic stress than hydrogel lenses of comparable Dk/L, as evidenced by the presence of epithelial microcysts. Several complications of RGP extended wear were observed including lens binding, blepharoptosis, transient pupil size increases, and corneal staining. As hypoxia-induced corneal changes, such as microcysts and striae, were observed in the RGP lens-wearing eyes, we consider that these particular RGP lenses do not have adequate oxygen transmissibility for successful long-term extended wear. However, if RGP lens materials of higher oxygen transmissibility and better designs can be attained, the potential of RGP extended wear would appear promising.     

Microbial flora of tears of orthokeratology patients, and microbial contamination of contact lenses and contact lens accessories.

PURPOSE: The purpose of this study is to determine if there are changes in the ocular flora of overnight orthokeratology (ortho-k) patients, and the levels of contamination of their lenses and lens accessories, and to correlate compliance with levels of contamination. METHOD: Normal ocular flora of 41 subjects was determined twice before commencing ortho-k lens wear by culture of the lower conjunctiva. Further specimens were collected on six follow-up visits after beginning lens wear, as were samples from their lenses, cases, and suction holders. A questionnaire on lens care was administered after the fifth visit. RESULTS: Three subjects provided conjunctival samples yielding Staphylococcus aureus on one occasion before lens wear, one being positive for this organism after beginning lens wear. Of 38 subjects yielding no growth or only normal eye flora before use, 28 remained free of ocular pathogens after beginning lens wear. Only four subjects had positive cultures on more than one occasion after lens wear. There was no significant difference in isolation levels of pathogens with lens wear (p = 0.423). Lens culture of 54% of subjects yielded no growth or normal flora only; lenses of 16 subjects yielded potential pathogens, including three subjects contaminated on more than one occasion. Lens isolates did not match the organisms transiently colonizing the eye. Lens case, the most frequently contaminated item, was associated with lens contamination (p < 0.001), the same organism being isolated from both items in 11 subjects. Lens suction holder was less frequently contaminated. Neither lens case nor suction holder contamination was associated with isolates from the eye. Reported good compliance correlated with lack of contamination in all but one subject. The most frequent breaches in the lens care protocol were failure to clean, disinfect, and replace the lens case. CONCLUSION: Ocular flora was not altered by ortho-k lens wear over an extended period, and patients remained free of infection. Contaminants identified were generally of a transient nature. Most patients had significant contamination of at least one item, most frequently the lens case. Lens case isolates were significantly associated with those from the lens. The majority of patients reporting good compliance had low or no contamination of their lenses and accessories.     

Characterization of the visual performance with soft daily wear disposable contact lenses

We investigate the visual performance associated with adaptation to a daily wear soft contact lens on the human eye. For this purpose, we used four parameters, one of which was an objective parameter, while the rest were subjective parameters. The objective parameter was a single quality parameter, a Merit function (Mf) derived from the modulation transfer function (MTF) of the overall [eye + contact lens] system The subjective parameters were the visual acuity (VA), the contrast sensitivity function (CSF) and the standard adaptation criterion of Terry et al. (1993). The normality criterion for the MTF was determined by evaluating the fluctuations of the Mf over a day in five emmetropic observers. Fluctuations with no statistically significant differences in the merit function ( p >0.05) and their standard deviation (8%) defined our standard criterion. The CSF and the VA were similarly measured (for emmetropic observers). The results obtained with emmetropic observers allowed us to establish a standard criterion for the evaluation parameters we propose. When this criterion is applied to daily soft wear disposable contact lenses, their performance proves to be good, since both the objective (MTF) and the subjective parameters (CSF, VA, adaptation criterion) always lie within the range defined by our criterion.     

Dehydration of hydrogel lenses during overnight wear

We studied the extent of dehydration of hydrogel lenses during overnight wear. Seven subjects used a hand refractometer to measure the water content of five different lenses (Hydron zero-6 (nominal water content 38.6%), -0.50 D; Snoflex 50 (52.5%), -0.50 and + 15.00 D, and Hydron Z-67 (67.5%), -0.50 and + 15.00 D) before and after 7 h of both open- and closed-eye wear. No statistically significant difference was observed in dehydration between open and closed eye lens wear. Thick and thin lenses made of the same material were found to dehydrate to an equal extent. Contrary to expectations, the medium water content Snoflex 50 lenses displayed a greater absolute decrease in water content than the higher water content Hydron Z-67 lenses (p less than 0.01). Factors that may influence the extent of dehydration under open- and closed-eye wearing conditions, and the clinical implications of these results, are discussed.     

Light scattering in artificial fog and simulated with light scattering filter

Disability glare, affecting e.g. road safety at night, may result either from intraocular light scattering or from external conditions such as fog. Measurements were made of light scattering in fog and compared with intraocular straylight data for normal eyes and eyes with simulated cataract. All measurements were made with a direct compensation flicker method. To estimate light scattering levels in fog, straylight measurements were carried in a fog chamber for different densities of fog. Density was characterized by the meteorological term visibility V and ranged from 7 to 25. Test distance for measurements in the fog was constant at 5 m. Cataract eye conditions were simulated by placing a light scattering polymer dispersed liquid crystal (PDLC) filter with scatterers of submicron size in front of the normal eye. All measurements were made using each of three broad-band color stimuli – red, green and blue (produced either with LEDs or a color CRT monitor). Differences were found in both the level and the spectral characteristics of scattering under the different conditions. The measured values of the straylight parameter, s , in artificial fog showed no noticeable spectral dependence at any visibility range. Increasing the visibility range caused an exponential decrease in the straylight. Intraocular straylight measured with the clear eye showed an increase at the red and blue ends of the spectrum as compared to the green. Straylight measured using PDLC plates with different transparency levels showed a spectral dependence which decreased with wavelength. The scattering introduced by the PDLC plate therefore failed to give a valid simulation of cataract and fog conditions for polychromatic stimuli, due to its erroneous spectral dependence.     

Extended wear hydrogel lenses. Long-term effectiveness and costs

During the period 1976-79, 1,201 of 1,552 aphakic patients were successfully fitted with third generation extended wear hydrogen lenses of thin-membrane design (CSI® lens) and highly hydrated polymer design (Permalens,® Sauflon®) without significant or permanent visual loss. Between 79% and 82% of the patients who failed did so in the first 90 days, and thereafter failure rates declined with time. Replacement rates for lenses approximated one lens per eye per year. Rates of required removal for cleaning varied. Ten to 13% of patients required cleaning at less than three-month intervals, and 5–6% at less than one month. For average patients with unilateral devices and no complications, extended wear lenses in Georgia are estimated to cost approximately three times as much as an intraocular lens over a 20-year follow-up period. General advantages of extended wear third generation lenses include: (1) an acceptably safe and visually effective way to correct aphakia when patients are carefully selected, fitted, educated, and followed; (2) can be easily removed, refitted or updated as technology advances; and (3) will not replace intraocular lenses, but can be used when implantation is contraindicated and should prevent the need for secondary or bilateral implantation or keratophakia in most cases.