Comparison of two ophthalmoscopes for direct ophthalmoscopy

Background: To measure the ease of use and performance of the Optyse lens‐free ophthalmoscope compared with the standard Keeler pocket ophthalmoscope, and to assess its suitability as an inexpensive ophthalmoscope for medical students. Design: Randomized cross‐over study. Participants: Twenty second‐year medical students, 10 as ophthalmoscopists (‘observers’) and 10 as ‘patients’. Methods: Students used both ophthalmoscopes to examine the optic disc in each eye of 10 ‘patients’. They were randomized as to the order in which they were used. A Consultant ophthalmologist was used as the gold standard. Main Outcome Measures: Main outcome measures were accuracy in estimating vertical cup:disc ratio (VCDR), ease of use (EOU) for each examination, and overall ease of use (OEOU). Results: Of 400 attempted eye examinations, sufficient visualization was achieved in 220 cases to allow a VCDR estimation: 107/200 VCDR estimates with the Optyse and 113/200 with the Keeler. Accuracy of VCDR estimates was better with the Optyse by the equivalent of 0.05 VCDR (P = 0.002). There was no significant difference in EOU or OEOU between the two ophthalmoscopes. EOU for 400 examinations: median (IQR) of 6 (3–8) for Optyse versus 6 (3–8) for Keeler (P = 0.648). OEOU for 20 scores: median (IQR) of 6.5 (2–9) for Optyse versus 5.5 (3–8) for Keeler (P = 0.21). Conclusion: Medical students found the Optyse and Keeler pocket ophthalmoscopes to be of similar ease of use and performed slightly better with the Optyse when estimating VCDR. The lens‐free Optyse ophthalmoscope is a reasonable alternative to the standard Keeler pocket ophthalmoscope.     

Comparison of photocoagulation with the argon, krypton, and diode laser indirect ophthalmoscopes in rabbit eyes.

PURPOSE: The purpose of this study is to compare photocoagulation with the argon green, krypton red, and diode infrared laser indirect ophthalmoscopes in an experimental setting. METHODS: Photocoagulation was performed with each of the laser indirect ophthalmoscopes in a grid pattern within one sector of the same eye of 14 Dutch-belted rabbits. Treatment was performed either with or without scleral depression. Measurements of the retinal burn diameters were performed after hemisecting the globes, and the burns were examined with light microscopy. RESULTS: Variation in burn intensity and diameter (10% to 28%) was common with all 3 laser indirect ophthalmoscopes. Five times more output energy was required to make equivalent burns with the diode laser indirect ophthalmoscope than with the argon or krypton laser indirect ophthalmoscopes. Choriovitreal hemorrhages only occurred during scleral depression. Histopathologically, the argon green laser indirect ophthalmoscope burns spared the choroid and inner sclera, while the intense krypton and diode burns had full-thickness choroidal involvement and even thermal injury to the inner sclera. Scleral depression reduced the mean energy required to create equivalent burns with all three laser indirect ophthalmoscopes. There was a 10% to 40% reduction in the mean retinal burn diameter with scleral depression (argon green, P < 0.0005; krypton red, P < 0.0005; and diode, P < 0.025). CONCLUSION: Photocoagulation with the argon green, krypton red, or diode infrared laser indirect ophthalmoscopes is a safe and effective method of retinal ablation. Decreasing the posterior nodal distance of the eye with scleral depression will produce a smaller spot on the retina with the laser indirect ophthalmoscope.     

Imaging the retina by en face optical coherence tomography

PURPOSE: To present the possibilities of a new system that combines optical coherence tomography (OCT) and confocal ophthalmoscopy, producing en face OCT images in patients with retinal diseases. METHODS: A prototype OCT Ophthalmoscope (OTI, Toronto, Canada) was used to scan patients with retinal conditions. The system uses a super luminescent diode (lambda = 820 nm; Deltalambda = 20 nm) and currently scans at a rate of 2 frames per second. In each frame, the OCT Ophthalmoscope simultaneously produces a transversal OCT scan and a confocal image in the X/Y plane. Both images correspond pixel to pixel. RESULTS: Between January 2002 and August 2003, >800 patients with various retinal diseases were scanned with the OCT Ophthalmoscope. Illustrative cases with regularly seen macular diseases are presented, such as macular hole and central serous retinopathy. CONCLUSION: Current difficulties as well as future possibilities of this new en face OCT ophthalmoscope are discussed. By presenting normal and pathologic transversal OCT images made by a prototype OCT Ophthalmoscope, we show that it can provide information not available using conventional OCT imaging.     

A simple accurate method of cataract classification. Cataract-I

A simple and accurate system of cataract classification using slit lamp and direct ophthalmoscope is reported. Lens opacities are classified into cortical (anterior and posterior), nuclear and posterior sub-capsular and each sub-type of opacity is graded, extent and density wise, using both slit lamp and direct ophthalmoscope. A circle representing enface view of opacity divided into 100 equal parts is used in calculating the area of each opacity. This classification takes into account both the area and depth of opacity in arriving at the total extent of sub-type of each opacity. For density determination, we do not recommend the use of a resolution target projection ophthalmoscope. Intra-observer and inter-observer variability studies using this classification system indicated that the classification system is fairly reliable.     

Grading contact lens complications under time constraints.

PURPOSE: To investigate the effect of observation time on the precision of grading the severity of contact lens complications. METHODS: Twenty-five optometry students used the Efron Grading Scales for Contact Lens Complications to grade the severity of one image of each of the 16 forms of anterior eye pathology depicted in the Efron scales. This procedure was repeated for observation times of 0.1, 2, and 60 s. RESULTS: Overall, significantly greater grading precision (smaller standard deviation of mean grades) was demonstrated for longer observation times (p < 0.004); however, certain complications appear to require longer observation times for precise grading. There was a highly significant dependence of the mean grade on image (p < 0.0001), observation time (p < 0.0001), and observation time-image interaction (p < 0.0001). CONCLUSIONS: Overall, a brief viewing time of a few seconds is typically all that is required for precise grading of ocular complications of contact lens wear. Some forms of pathology are more complex and may require more time to grade precisely.     

Image quality characteristics of a novel colour scanning digital ophthalmoscope (SDO) compared with fundus photography

PURPOSE: To establish a set of quality parameters for grading image quality and apply those to evaluate the fundus image quality obtained by a new scanning digital ophthalmoscope (SDO) compared with standard slide photography. METHODS: On visual analogue scales a total of eight image characteristics were defined: overall quality, contrast, colour brilliance, focus (sharpness), resolution and details, noise, artefacts and validity of clinical assessment. Grading was repeated after 4 months to assess repeatability. Fundus images of 23 patients imaged digitally by SDO and by Zeiss 450FF fundus camera using Kodak film were graded side-by-side by three graders. Lens opacity was quantified with the Interzeag Lens Opacity Meter 701. RESULTS: For all of the eight scales of image quality, good repeatability within the graders (mean Kendall's W 0.69) was obtained after 4 months. Inter-grader agreement ranged between 0.31 and 0.66. Despite the SDO's limited nominal image resolution of 720 x 576 pixels, the Zeiss FF 450 camera performed better in only two of the subscales - noise (p = 0.001) and artefacts (p = 0.01). Lens opacities significantly influenced only the two subscales 'resolution' and 'details', which deteriorated with increasing media opacities for both imaging systems. CONCLUSIONS: Distinct scales to grade image characteristics of different origin were developed and validated. Overall SDO digital imaging was found to provide fundus pictures of a similarly high level of quality as expert photography on slides.     

Fundus imaging in patients with cataract: role for a variable wavelength scanning laser ophthalmoscope.

AIMS--An investigation was carried out to compare the image quality of the ocular fundus obtained clinically, photographically, and with the scanning laser ophthalmoscope (SLO) at visible and infrared wavelengths in patients with significant cataract. METHODS--Nineteen patients admitted for routine cataract extraction were examined clinically by two independent observers to ascertain cataract type and clarity of fundus view with an indirect ophthalmoscope. Fundus photography and both confocal and direct (non-confocal) SLO imaging at 590 nm, 670 nm, and 830 nm were carried out after pupillary dilatation. Images obtained were graded independently using a recognised grading system. RESULTS--Quality of SLO images appeared to be superior to indirect ophthalmoscopy (p < 0.01) and fundus photography (p < 0.001) when graded subjectively. Quantitative analysis of contrast of retinal vessels demonstrated significantly higher contrast for the SLO compared with digitised fundus photographs at all wavelengths tested (p < 0.001), with highest contrast at 590 nm. Use of a confocal aperture significantly improved vessel contrast but may reduce overall image intensity. CONCLUSIONS--Scanning laser ophthalmoscopy may offer a method to observe and record fine fundus detail in patients who have marked cataract.     

Wide-angle fluorescein angiographic scanning with high resolution using a scanning laser ophthalmoscope through a mirror image fixation target

Internal and moving targets of scanning laser ophthalmoscopes are not capable of observing the fundus beyond a field of more than 80 degrees with high resolution. The authors enabled wide-angle fundus examination with high resolution through a modification of the target. Mirror image fixation targets(MIFT), which fixated the opposite side of the examined eye onto the mirror image of five lamps placed 1.5 m away from the patient, were used to observe the fundus during fluorescein angiography in five diabetic retinopathy patients. In three of them, the ranges of the fundus examinations were measured using conventional internal fixation targets. The mean ranges of the fundus examinations when using MIFT (77.2 +/- 2.5 degrees horizontally, 67.9 +/- 2.1 degrees vertically) were significantly wider than when using internal fixation targets (65.5 +/- 2.6 degrees horizontally, 44.4 +/- 2.8 degrees vertically). MIFT provided a wide angle fundus view with high resolution equal to that of 40 degrees angle images using a scanning laser ophthalmoscope.     

Panoptic versus conventional ophthalmoscope

Background: The ‘ease of use’ and accuracy in measurement of the vertical optic cup/disc ratio (VCDR) was compared between the conventional direct ophthalmoscope (CO) and Panoptic direct ophthalmoscope (PO) in a group of ‘naïve’ first year medical students to determine which would be more suitable for non‐ophthalmologists. Methods: In this quasi‐randomized method comparison study, eight students received an introductory session on ophthalmoscopy then examined 18 eyes (9 left, 9 right) with each ophthalmoscope in a private practice. The subjects were the eight students themselves plus two other subjects. Each subject (n = 10) had one eye dilated. Students determined a VCDR and a subjective score of ‘ease of use’ on a scale of 1 (difficult) to 10 (easy). A consultant ophthalmologist (GAG) determined the benchmark VCDR for each eye with each ophthalmoscope. Results: Of 288 eye examinations, there were 111 measure­ments of VCDR using the CO (47 undilated, 64 dilated), and 140 measurements using the PO (75 undilated, 65 dilated). Differences in the students’ estimated VCDR and the benchmark were similar for the CO and PO (P = 0.67). ‘Ease of use’ was scored in 288 eyes and the median score was higher in the PO overall (CO: median 8, IQR 6?9; PO median 9, IQR 8?10; P < 0.0001), and within each session (P < 0.0001 for each session). Conclusions: Medical students found the PO much easier to use, with accuracy of rating the VCDR similar to the CO. This comparison would support the wider use of the PO amongst medical students, general practitioners and other primary care providers.     

Addressing the ‘forgotten art of fundoscopy': evaluation of a novel teaching ophthalmoscope

Background

Direct ophthalmoscopy is an essential skill that students struggle to learn. A novel ''teaching ophthalmoscope'' has been developed that allows a third person to observe the user''s view of the fundus.

Objectives

To evaluate the potential use of this device as an aid to learning, and as a tool for objective assessment of competence.

Methods

Participants were randomised to be taught fundoscopy either with a conventional direct ophthalmoscope (control) or with the teaching device (intervention). Following this teaching session, participant competence was assessed within two separate objective structured clinical examination (OSCE) stations: the first with the conventional ophthalmoscope and the second with the teaching device. Each station was marked by two independent masked examiners. Students were also asked to rate their own confidence in fundoscopy on a scale of 1-10. Scores of competence and confidence were compared between groups. The agreement between examiners was used as a marker for inter-rater reliability and compared between the two OSCE stations.

Results

Fifty-five medical students participated. The intervention group scored significantly better than controls on station 2 (19.8 vs 17.6; P=0.01). They reported significantly greater levels of confidence in fundoscopy (7.3 vs 4.9; P<0.001). Independent examiner scores showed significantly improved agreement when using the teaching device during assessment of competence, compared to the conventional ophthalmoscope (r=0.90 vs 0.67; P<0.001).

Conclusion

The teaching ophthalmoscope is associated with improved confidence and objective measures of competence, when compared with a conventional direct ophthalmoscope. Used to assess competence, the device offers greater reliability than the current standard.     

显微镜下行孔源性视网膜脱离复位术的临床观察

目的:评价显微镜直视下行孔源性视网膜脱离复位手术与直接检眼镜下行孔源性视网膜脱离复位手术的疗效。方法:对93例93眼孔源性视网膜脱离随机分为两组,A组47例采用显微镜直视下行孔源性视网膜脱离复位手术;B组46例采用直接检眼镜下行孔源性视网膜脱离复位手术。观察术后2wk手术成功率及视力提升率。结果:A组视网膜复位率为95.74%,B组为80.43%。A组术后视力提升率为82.98%,B组67.39%。A组手术时间明显短于B组。结论:显微镜直视下手术较直接检眼镜下行孔源性视网膜脱离复位手术成功率更高,且更简便、精确、易操作,能有效延长主刀医师的手术年限。     

Potential hazards from specific ophthalmic devices

The retinal light exposure a patient might receive from ophthalmoscopes, slit lamps, surgical microscopes, and overhead surgical lamps is documented. Monkey exposures to microscopes and slit lamps were performed to substantiate the findings. A “typical” indirect ophthalmoscope is seen to be “unsafe” after 23 sec of exposure in a patient with dilated pupils and clear media, if compared with laser safety standards. Slit lamp biomicroscopy of the macula produces 2–3 times greater retinal exposure than the indirect ophthalmoscope. Operating microscope internal light sources produce a surprising retinal exposure of up to 10 times greater than the indirect ophthalmoscope over an area of several disc diameters, causing severe choroioretinal lesions in monkeys after 1 hr of continuous exposure. The surgeon's retina receives 44 mW/cm² from the corneal specular reflection of the microscope source. Using the laser safety standards, this is “unsafe” after one minute. A prototype surgical illuminator is described which reduces retinal irradiance to 1/900th of that from conventional microscope light sources, while maintaining equivalent illumination of the anterior segment.     

直接检眼镜数字化图像系统的研究

目的进行直接检眼镜数字化图像系统的可行性研究。方法在光学实验室中,通过对光学适配器的计算与设计,完成光学适配器的构建,同时对传像光纤束、彩色数字式摄像机(CCD)像素进行不断的优化。应用该光学适配器、传像光纤束、CCD与图像采集卡连接直接检眼镜与电子计算机,可使直接检眼镜观察的模型眼的眼底图像,以数字信号的形式显示在计算机的显示屏上。运用图像采集卡的应用程序TVPlus3.0以及捕捉按钮,采集眼底图像,并储存到指定的硬盘上。运用图像处理软件对储存图像进行各种处理。结果在光学平台上构建了直接检眼镜数字化图像系统。通过该系统可以完成眼底图像的动态观察、储存及处理,并可同步示教。结论直接检眼镜数字化图像系统在眼底病的研究、教学和临床实践中是一种有用的工具。     

Lens autofluorescence and light scatter in relation to the lens opacities classification system, LOCS III.

PURPOSE: To compare values of the human lens autofluorescence and back light scatter measurements with the improved Lens Opacities Classification System, LOCS III. METHODS: We measured autofluorescence and back light scatter of the lens from 122 smoking males aged 57 to 76 years who participated in a cancer prevention study. The retroillumination and slit-lamp photographs of the lenses were graded according to LOCS III by the Center for Ophthalmic Research in Boston. Lens fluorometry was carried out with a previously described technique using blue-green (495 nm/520 nm) autofluorescence range. Interzeag Lens Opacity Meter 701 was used for light scatter measurements. RESULTS: LOCS III nuclear opalescence and color grades were statistically significantly correlated with lens autofluorescence as well as with light scatter values. The lens transmission index of autofluorescence measurements showed the highest correlation with the nuclear color (r = -0.71; p < 0.0001) and the light scatter value with nuclear opalescence (r = 0.64; p < 0.0001). There was no correlation between autofluorescence measurements and LOCS III grades of cortical or posterior subcapsular cataract. A weak relation could be found between the grades of cortical cataract and light scatter values. CONCLUSIONS: The lens fluorometry provides a practical clinical technique to evaluate the yellow coloration and opalescence of the human lens nucleus. It may be a useful additional tool together with a subjective grading system in the follow-up of optical changes occurring in the nuclear region of the lens.     

The prevalence of cataract in a population with and without type 2 diabetes mellitus

Purpose: To evaluate the prevalence and risk factors of lens opacities in a geographically defined population of subjects with type 2 diabetes mellitus compared with a control population. Methods: Subjects in the community of Laxå with a diagnosis of type 2 diabetes mellitus (n = 275) and a control group (n = 256) participated in the study. Lens opacities were graded with Lens Opacities Classification System II in all participants. Lens Opacities Classification System score ≥2 was considered as significant lens opacity. Anthropometric and blood chemistry data were collected for all participants in connection with the eye examination. For the diabetic population, yearly updated information on glucose control, blood pressure and body mass index was available through medical records from diabetes diagnosis until the time of the eye examination. Results: The prevalence of significant cortical, posterior subcapsular and nuclear cataract was 65.5%, 42.5% and 48.0%, respectively, in the type 2 diabetes population in Laxå. In logistic regression analyses, all types of lens opacities were strongly associated with age (p < 0.0001). Cortical lens opacity was also associated with a diagnosis of diabetes (p < 0.0001), posterior subcapsular lens opacity with HbA1c (p < 0.0001) and nuclear lens opacity with female gender and higher heart rate (both p = 0.0004). In the diabetic population, all types of cataract were likewise strongly associated with age (p < 0.0001), posterior subcapsular cataract with HbA1c (p = 0.0032), nuclear cataract with female gender (p = 0.0002) and higher heart rate (p = 0.0008). Conclusions: Our study shows that cortical cataract is associated with diabetes mellitus, not necessarily defined by glucose control, whereas posterior subcapsular cataract is associated with glucose levels. Nuclear cataract is not associated with diabetes mellitus, but is more frequent in women and is also associated with higher heart rate.     

Modernization of ophthalmoscopic techniques

The great principles of ophthalmoscopy have been known for many decades. This paper intends show the new possibilities allowed by modern technology, especially in two fields. First of all, it is possible, even in keeping basic principles, to improve previous machines with, for example, better magnification, new ophthalmoscopic lens, or to create new materials as telescopes for clinical practice or intra-ocular surgery, wide angle or high magnification fundus cameras for posterior pole examination. Secondary, by revolutionary principles, it is possible to introduce laser in the ophthalmoscopic field and to imagine new ophthalmoscopes: SLO i.e. Scanning Laser Ophthalmoscope or SLM i.e. Scanning Laser Microscope, which opens a window on the future.     

Fluorescein filling defects of the optic nerve head in normal tension glaucoma, primary open-angle glaucoma, ocular hypertension and healthy controls

BACKGROUND: To evaluate fluorescein filling defects of the optic nerve head in normal tension glaucoma (NTG), primary open-angle glaucoma (POAG), ocular hypertension (OHT) and controls. METHODS: Forty patients with NTG (mean age 55 +/- 10 years), 40 patients with POAG (mean age 55 +/- 11 years), 40 patients with OHT (mean age 53 +/- 13 years), and 40 age-matched controls (mean age 54 +/- 11 years) were included in a prospective study. Video fluorescein angiograms were performed by means of a scanning laser ophthalmoscope. The extent of absolute filling defects of the optic nerve head was assessed (as a percentage of the disc area) using digital image analysis. Visual fields were tested by automatic static perimetry (Humphrey Field Analyzer, programme 24-2). RESULTS: Absolute filling defects were significantly larger in patients with NTG (12.2 +/- 15.5%) and POAG (12.9 +/- 13.1%) compared to patients with OHT (1.2 +/- 3.6%) and healthy controls (0.1 +/- 0.5%) (p < 0.0001). The area under the receiver operating characteristic (ROC) curve was 0.806 for NTG vs healthy controls, and 0.812 for POAG vs OHT. Absolute filling defects are significantly correlated to the global indices mean deviation (r = -0.63, p < 0.0001), pattern standard deviation (r = 0.61, p < 0.0001), and corrected pattern standard deviation (r = 0.62, p < 0.0001) and significantly correlated to horizontal (r = 0.50, p < 0.0001) and vertical (r = 0.53, p < 0.0001) cup-to-disc-ratios. CONCLUSIONS: Fluorescein filling defects of the optic disc representing capillary dropout are present in NTG and POAG. The extent of these filling defects is correlated to visual field loss and morphological damage. Fluorescein angiography may be useful in the diagnosis and management of NTG and POAG.     

A novel instrument for assessing the retinal red reflex for non‐ophthalmic health professionals

Background : The direct ophthalmoscope is the standard instrument for assessing retinal red reflexes when screening for cataract, however, it is expensive and often not available to non‐ophthalmic health professionals. The pen torch ophthalmoscope is a new economic alternative for this purpose. This study aimed to determine its accuracy in assessing retinal red reflexes and to compare it to the direct ophthalmoscope. It is anticipated that this instrument will be useful in detecting both congenital and adult type cataracts. Methods : Eighteen health professionals evaluated the retinal red reflexes of 68 subjects at the Dunedin Hospital Eye Clinic with both the direct ophthalmoscope and the pen torch ophthalmoscope. Three groups of seven, six and five observers assessed both eyes of 24, 21 and 23 subjects, respectively, resulting in 1,574 examinations. Results : Compared to the direct ophthalmoscope, the pen torch ophthalmoscope exhibited lower sensitivity (68 per cent versus 75 per cent), but higher specificity (72 per cent versus 63 per cent) and lower over‐referral (false positive) rates by nine per cent. The positive predictive value in respect to identifying for cataract was better for the pen torch ophthalmoscope (71 per cent) than for the direct ophthalmoscope (66 per cent), while the negative predictive value was slightly worse (70 per cent and 73 per cent, respectively). When compared to the direct ophthalmoscope, 15/18 observers felt the pen torch ophthalmoscope was accurate enough, one felt it was just as good and two did not respond. Conclusions : This pilot study demonstrates that the pen torch ophthalmoscope is comparable to the direct ophthalmoscope in detecting abnormal retinal red reflexes in adults with cataracts. At six per cent of the cost of a direct ophthalmoscope, it may appeal to non‐ophthalmic health professionals in developed and developing countries. It may also increase the frequency of screening for cataract in children and adults. Further development and study of this pen torch ophthalmoscope prototype is warranted.     

直接检眼镜下行巩膜扣带术治疗视网膜脱离

目的观察直接检眼镜下行巩膜扣带术治疗原发性(孔源性)非增生性视网膜脱离的疗效。方法42例孔源性非增生性视网膜脱离行巩膜扣带术。手术均在直接检眼镜直视下进行,术中给予准确的裂孔定位,适度的冷凝,放液或不放液和恰当的放置外垫压物。术后随访,观察视网膜复位情况、视力、眼压及并发症。结果视网膜复位40眼(95.24%),失败2眼(4.76%)。术后视力提高39眼,不变2眼,下降1眼。眼压升高3眼,服药后恢复正常。冷凝过度1眼。结论巩膜扣带术治疗原发性(孔源性)非增生性视网膜脱离简单可靠。直接检眼镜直视下手术成功率较高。     

Adherence of Acanthamoeba to unworn conventional and disposable soft contact lenses

PURPOSE: To compare the adherence of Acanthamoeba trophozoites and cysts to two types of unworn conventional and disposable contact lenses included in groups 1 and 4 of the Food and Drug Administration and to assess the adherence to the center and edge of the lenses. METHODS: We used 10 conventional and 10 disposable contact lenses belonging to groups 1 and 4 of the Food and Drug Administration. Each lens was divided into four segments. A human corneal isolate of Acanthamoeba suspended in saline (1x 105 amoebae/mL) was used. Lens segments were exposed to Acanthamoeba cysts and trophozoites for 2 hours. After removal, the count was made with an optical microscope at 100x magnification. Three fields at the center and three fields at the edge were read on each segment. RESULTS: Acanthamoeba adhered to both types of contact lenses, with a proportion of trophozoites to cysts between 6:4 and 7:3. There was a significantly higher adherence to disposable (8.14 +/- 3.57 organisms/mm(2)) than to conventional (4.94 +/- 2.33 organisms/mm(2)) (p < 0.0001) contact lenses. We also found that the greatest adherence was to the edge of the conventional (12.05 +/- 4.03 organisms/mm(2)) and disposable (26.10 +/- 7.84 organisms/mm(2) (p < 0.0001) contact lenses. CONCLUSIONS: This study shows that Acanthamoeba has varying adherence affinity for different new hydrogel contact lenses. The affinity for disposable lenses (etafilcon A) is significantly higher than that for conventional lenses (polymacon). This adherence is greater for ionic material and high water content. The use of low water content, nonionic contact lenses may reduce the adherence of Acanthamoeba. Finally, the edge may play an important role as an Acanthamoeba vector.