Experience and training as determinants of grading reliability when assessing the severity of contact lens complications

PURPOSE: A study was conducted to investigate the influence of experience and training on grading reliability when assessing the severity of contact lens complications. METHODS: Twenty-three optometry students who were unfamiliar with the use of grading scales each used the Efron Grading Tutor computer program to ascertain grading reliability at an 'initial' experimental session and a 'final' session 3 weeks later. Twelve subjects (the 'trained' group) were given a tutorial on grading techniques and were asked to complete two grading exercises between the initial and final sessions. The other 11 subjects (the 'untrained' group) received no such training between the two sessions. Differences in grading reliability between the initial and final grading sessions were evaluated. RESULTS: Grading reliability was superior (lower) for the combined subject cohort at the final session (mean +/- standard deviation 0.33 +/- 0.12) compared with the initial session (0.46 +/- 0.25) (p = 0.004). However, there was no difference in the improvement in grading reliability between the two groups. CONCLUSIONS: Grading reliability improves statistically with some experience, although perhaps not to a clinically meaningful extent. No added benefit can be derived from supplemental training.     

Validation of computer morphs for grading contact lens complications

Abstract An alternative to the use of printed grading scales for assessing the severity of contact lens-induced ocular pathology is to use computer-generated grading morphs. This technique involves manipulation of a continuously variable movie sequence until this matches the severity of the condition being observed. To validate the use of computer morphs, nine experienced optometrists were each invited to grade - to the nearest 0.1 increment - an image of each of 16 contact lens complications, using printed scales (Efron Grading Scales for Contact Lens Complications) and computer morphs (Efron Grading Morphs). This entire procedure was repeated approximately 2 weeks later, yielding a total data base comprising of 576 individual grading estimates. Good accuracy was achieved using computer morphs, as evidenced by the similarity between the mean of the test and retest grading estimates for the printed scales (2.8 +/- 0.7) and the computer morphs (2.6 +/- 0.8) (F1,8 = 2.7, p = 0.14). There was no difference in median reliability between the printed scales (+/- 0.41) and the computer morphs (+/- 0.43) (Z = 0.1, p = 0.95). Computer morphs are thus considered to have been validated in view of their accuracy and reliability compared with printed scales. In addition, computer morphs offer considerable utility in terms of computer-based clinical record keeping, teaching and learning, and clinical research.     

The combined influence of knowledge, training and experience when grading contact lens complications

PURPOSE: A study was conducted to evaluate the influence of knowledge, training and experience (clinical skills set) when assessing the severity of contact lens complications. METHODS: Nine optometrists (who were in possession of a relevant clinical skills set) and nine 'non-optometrists' (subjects without the clinical skills set) were each invited to grade - to the nearest 0.1 increment - an image of each of 16 contact lens complications using Efron Grading Scales for Contact Lens Complications. This procedure was repeated 2 weeks later, yielding a total data base comprising 576 individual grading estimates. RESULTS: The mean of the test and retest grading estimates was the same for the optometrists (2.8 +/- 0.7) and the non-optometrists (2.6 +/- 0.9) (F1,15,1 = 1.3, p = 0.26); that is, non-optometrists can grade accurately. Median grading reliability for optometrists (+/-0.41) was lower than (i.e. superior to) that for non-optometrists (+/-0.67) (p = 0.001). Non-optometrists tended to display a reluctance to grade by interpolation and to less reliably grade subtle clinical signs. CONCLUSIONS: When averaged over several attempts, non-optometrists will arrive at similar estimates of severity to optometrists when grading ocular complications of contact lens wear; however, they will do so less reliably. The relative contribution of the three attributes of the clinical skills set to grading performance is presently unclear.     

The physiologic effects of extended wear soft contact lenses

The major physiologic effect to the eyes of soft contact lenses in general and continuously worn hydrogel lenses in particular is a decrease in the amount of oxygen normally available to the cornea. This reduction in oxygen supply produces changes as minimal as clinically undetectable epithelial edema and as severe as the anoxic overwear syndrome that produces pain and decreased vision. Induced corneal edema can produce refractive error changes and endothelial cell changes. On a long-term basis the lenses produce physical trauma to the anterior surface of the cornea as well as certain metabolic changes and have been associated with a significant degree of corneal neovascularization. Because hydrogel lenses require a different type of care than standard, hard PMMA lenses, new complications are being described, such as giant papillary conjunctivitis, lens deposits, and acute red eye syndromes that may be associated with allergic or toxic reactions to preservatives used in the cleaning processes. Research is underway to develop hydrogel materials that will allow more oxygen to reach the corneal surface and prevent surface deposits from forming.     

DEEP CORNEAL STROMAL OPACITIES WITH CONTACT LENSES

Two patients with deep corneal stromal opacities occurring after prolonged contact lens wear are described. The opacities were associated with folds or striae in Descemet's membrane which they overlay. Development of the opacities was associated with ocular discomfort, photophobia, reduced vision and a history of prolonged daily wearing times. Although the corneal endothelial cell counts were within the normal range, the count was reduced in the affected eye in the patient with the unilateral deep stromal opacity and there was mild polymegathism of the endothelial cells. It is possible that the long-term effects of subtle endothelial cell changes may cause a keratopathy with later scarring and opacification. Poor oxygen trans-missibility, carbon dioxide build-up, or suction effects by the lens may all be aetiological factors. Early recognition and treatment, particularly with a better fitting lens of high oxygen transmissibility is important, as once developed the opacities regress only slowly and may result in permanent visual impairment.     

Spectral optical coherence tomography: a new imaging technique in contact lens practice

PURPOSE: Spectral optical coherence tomography (SOCT) is a new non-invasive, non-contact, high-resolution technique, which provides cross-sectional images of objects that weakly absorb and scatter light. The aim of this article is to demonstrate the application of SOCT to imaging of eyes fitted with contact lenses. METHODS: Nine eyes of six different subjects fitted with various contact lenses have been examined with a slit-lamp and a prototype SOCT instrument. RESULTS: Our SOCT system provides high-resolution (4-6 mum longitudinal, 10 mum transversal) tomograms composed of 3000-5000 A-scans with acquisition time of 100-250 ms. The quality of the images is adequate for detailed evaluation of contact lens fit. Design, shape and lens edge position were assessed, and complications of contact lens wear could be visualized. Thickness of the lens, corneal epithelium and stroma as well as the space between the lens and the eye surface have been measured. CONCLUSIONS: SOCT allows high-resolution, cross-sectional visualization of the eye fitted with a contact lens. The ability to carry out a detailed evaluation of the fitting relationship between the lens and the ocular surface might be useful in research and optometric practice. SOCT can also be helpful in diagnosis, evaluation and documentation of contact lens complications.     

Corneal Response to Extended Wear of CAB Contact Lenses in Aphakia

We studied 41 aphakic eyes in 30 patients who had been wearing CAB (cellulose acetate butyrate) contact lenses on an extended basis. Patients were 51 to. 81 years old and averaged 14.3 months of wearing time. Visual acuity was very good. Pachometry measurements ranged from 0.42 mm to 0.66 mm and averaged 0.550 mm. This compares favorably with data in the literature on corneal thickness seen with routine use of PMMA or hydrogel lenses or with extended wear of hydrogel lenses. Corneal thickness was also compared with unoperated fellow eyes and eyes using CAB lenses on a daily basis only.     

Solving soft contact lens problems

Soft contact lens wearers encounter a variety of problems affecting their vision and comfort. Six patients with soft lens-related problems are discussed, illustrating the various sources of problems and approaches to their solution.     

Extended-wear lenses. An update

Extended-wear lenses present problems to be overcome by both the lens fitter and the patient. Guidelines are given for selecting patients and lenses, fitting the lenses, educating the patient, and handling complications. It is emphasized that patients who are happy with their day-wear lenses should not be urged to change to extended-wear lenses, and that if extended-wear lenses are worn, conscientious followup is crucial.     

Trends in Australian contact lens prescribing 2000

Background: This study was conducted to ascertain current modes of contact lens prescribing in Australia. Methods: One thousand questionnaires were randomly distributed to proportionate samples of optometrists in each state of Australia. The profession fits the majority of contact lenses in Australia and the sample represents 55 per cent of all optometrists. We requested details of the first 10 patients fitted with contact lenses after receipt of the questionnaire. Results: We received 224 completed questionnaires, detailing contact lens fits to 2,230 patients. The mean age of the patient group was 32.3 ± 12.9 years and 65 per cent of these were female. Sixty per cent of patients were existing wearers, the remainder being new fits. The data indicated that 94 per cent of new fits were with soft lenses, of which six per cent were for extended wear. For refits 83 per cent were soft lenses and 24 per cent were extended wear. It was clear that the lens of first choice was mid‐water‐content (52 per cent of all soft lens fits). Only nine per cent of all soft fits were for lenses which were not replaced on a planned basis. The majority of rigid lenses were prescribed using mid‐Dk materials (71 per cent). Analysis of solution prescribing indicates that multipurpose products were the most common regimens for planned replacement soft lenses. The percentage of hydrogen peroxide prescribed increased as lens replacement became less frequent. Conclusions: Non‐planned replacement lenses are now rarely prescribed to patients. Extended wear lenses and rigid lenses are prescribed more to existing contact lens wearers. The impact of multifocal lens designs on contact lens prescribing is very small, namely, five per cent of soft contact lenses and eight per cent of rigid lenses, despite 20 per cent of patients being over 45 years of age.     

The influence of lens conditioning on signs and symptoms with new hydrogel contact lenses

Background: Daily disposable contact lenses are considered to be the pinnacle of safe contact lens wear, yet it has been suggested that it takes some period of wear for the lens surface to reach optimal compatibility with the ocular surface. This study assesses the influence of brief treatment with a conditioning drop on the ocular response to new contact lenses over a single day of wear. Methods: The study was a single‐masked, paired (contralateral) comparison of the signs and symptoms with wear of new Acuvue 2 contact lenses pretreated with a conditioning agent containing carboxymethylcellulose (carmellose, CMC) against new lenses inserted directly from the blister pack. Sixty‐one subjects participated in the study, of whom 59 were considered eligible for data analysis. Subjects were also divided into symptomatic and asymptomatic lens wearers based on their overall comfort level in lens wear. Symptoms and signs were recorded at lens delivery and following eight hours of wear. Results: A set of slitlamp signs, comprising corneal staining (p < 0.05), limbal redness (p < 0.05), bulbar conjunctival hyperaemia (p < 0.05), bulbar conjunctival staining (p < 0.01) and palpebral conjunctival redness (p < 0.05) showed small but statistically significant (p < 0.05) end‐ofday mean values in favour of the lens that was conditioned with the rewetting agent. These data were supported by the proportion of subjects showing lower gradings with conditioned lenses versus unconditioned lenses, as follows: corneal staining (35 per cent versus 12 per cent, p <0.05), limbal redness (43 per cent versus 22 per cent, p < 0.05), bulbar conjunctival hyperaemia (50 per cent versus 15 per cent, p < 0.05), bulbar conjunctival staining (46 per cent versus 30 per cent, p < 0.1) and palpebral conjunctival hyperaemia (28 per cent versus 17 per cent, NS). For those subjects reporting symptoms with lens wear (n = 12), there was a statistically significant (p < 0.05) preference in terms of comfort as a result of preconditioning. Conclusions: The results of the investigation suggest that use of a conditioning agent can provide a more physiologically suitable environment for a new lens, thereby reducing the clinical signs associated with lens discomfort. The protocol used here, which is based on a statistical paradigm using standard pictorial grading scales, allows high sensitivity in detecting small changes in ocular parameters.