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A prospective study of noncompliance in contact lens wear
Abstracts (loss), connective tissue disease differing from 1”SS (CTD), and a normal control group (N) (for each group n = 50). Each patient was examined twice, with a 5-month interval (tear film break-up time [BUT], Schirmer-I test [SlT], conjunctival impression cytology for the presence of snake-like chromatin [SLC], tear lactoferrin assay [Lactoplate], rose hengal scoring [RBS], and central-cornea1 anesthesiometry [Cachet-Bonnet]). Keratoconjunctivitis sicca (KCS) was diagnosed when at least two of the following criteria were fulfilled: BUT 510 seconds; SIT 55 mm/5 minutes; RBS 24. A postal questionnaire was also used to evaluate subjective symptom experience. It was found that 12% of normals and 26% of CTD patients fulfilled the criteria for positive diagnosis of KCS. Positive symptom questionnaire responses were found to be more frequent in the 1”SS than in the N group (p 5 0.02). Positive symptom questionnaire responses were also more frequent in the 1”SS group than the CTD group, whereas the CTD without-dryness subjects reported more complaints of “dryness” than the N group (even though the presence of SLC was the only clinical parameter to be noticeably different between the two groups). With the exception of the Cachet-Bonnet results, the prevalence of abnormal clinical findings was more frequent in 1”SS than in normals (p 5 0.0009), with no discernible difference between 1”SS and CTD with KCS (with the exception of Lactoplate results). Questionnaire elements regarding the perception of ocular discomfort (dryness, sand/gravel, burning, and foreign-body sensation) had a high diagnostic sensitivity and specificity, and the authors suggest the use of such questions, for screening purposes, to be reasonable, unless the population is very old. The finding that CTD patients without KCS complained more of “dryness” than normals may suggest: (i) that there is a generally decreased tolerance in the severely ill patient; or (ii) that symptoms precede objective clinical changes. If the latter proposition holds true, symptom evaluation as part of a diagnostic battery may allow for the early diagnosis of Sjogren’s syndrome. BUT 5 10 seconds and SIT 5 10 mm/5 minutes both had very high diagnostic sensitivity but low specificity when considered independently; however, when used in combination, an increased specificity was achieved. RBS 24 and SlT 55 mm/5 minutes both had very high diagnostic specificities, but low sensitivities, even when used in combination. The presence of SLC and the Lactoplate test had low specificities and lower sensitivities than BUT and SlT. Central cornea1 sensitivity assessment was found to be of no diagnostic value. Symptoms were generally not significantly correlated to abnormal results of a single test. Repeated ocular examination showed that test results may vary markedly from one consultation to the next, indicating that most patients have good and bad periods reflecting activity in their disease. Therefore, to exclude a diagnosis of KCS, a patient should be examined at least twice. The authors advocate the use of the Copenhagen test
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1997
criteria and suggest that its diagnostic specificity may he increased by changing the SlT cut-off from 10 mm/5 minutes to 5 mm/5 minutes, with a decreased BUT cut-off also being of possible value.
Diurnal Variation
in Human Cornea1 Thickness.
Harper CL, Boulton ME, Bennett D, Marcyniuk A, JarvisEvans JH, Tulle AB, Ridgway AE: Br J O@u&nol 1996; 80:1068-1072. The physiologic status of the cornea can be evaluated from measurements of cornea1 thickness. The closed eyelids during sleep induce a degree of hypoxia in the normal healthy eye. Lactate in the cornea, which arises from anabolic metabolism, causes an osmotic influx of water. On eye opening, the cornea rapidly regains its normal thickness, although other factors such as tear film evaporation, intraocular pressure, and body temperature are also believed to affect cornea1 thickness. This study examines diurnal variation in human cornea1 thickness over a 48.hour period, using ultrasonic pachymetry. Eight healthy non-contact lens-wearing individuals ranging in age from 10 to 63 years participated in the study. All cornea1 thickness measurements were made in the subjects’ homes. Measurements were taken within the hour before sleep; immediately on waking; at 15, 30, and 45 minutes: at 1, 1.5, 2, 2.5, and, 3 hours; and at two-hourly intervals thereafter throughout the remainder of the day. Mean cornea1 thickness for all subjects was found to be 546 ? 14 pm. The mean overnight increase in central cornea1 thickness was 5.2%. For all but one subject, this was lower than the degree of diurnal variation (mean, 7.2%). No consistent pattern of variation was observed for the eight subjects throughout the waking hours. For three subjects, the first reading taken on eye opening was not the highest and cornea1 thickness continued to rise. There was found to be significant intersubject differences in the extent of overnight (1.9-12.6%) and maximum diurnal variation (2.1-14.3%). No overall gender differences in cornea1 thickness were observed. The study confirms previous findings of increased corneal thickness during eye closure, although the levels in this study were found to be higher than published reports of 3.0 to 4.4%. Considerable variation in cornea1 thickness during waking hours was also demonstrated by the authors. This suggests that the overnight change in human cornea1 thickness, previously assumed to be the maximal change, does not fully represent diurnal variation.
A Prospective Study of Noncompliance Lens Wear. Claydon BE, Nathan 1996;19(4):133-140. Contact
lens-related
in Contact
N, Woods C: +I Br Contact Lens Assoc
problems,
and ultimately
failure,
have
Craig and Blades been attributed to noncompliance in hygiene, lens care, and attendance of aftercare appointments. To determine the effect of a greater level of education on compliance, a prospective, randomized, controlled, and double-masked study is described. In the study, half of a group of 80 experienced contact lens patients were exposed to a “compliance enhancement strategy” in addition to a standard level of contact lens instruction, which was given to the remaining subjects. The strategy comprised extra education with a video, booklets, posters, a checklist, and a health-care contract. Free solutions (ReNu Multipurpose) and contact lenses (Medalist 38) were supplied to all patients. At a 12-month aftercare check, compliance levels were assessed by means of a demonstration and questionnaire. Both groups of subjects participating in the study were generally found to be compliant with successful contact lens wear and maintenance. No significant difference was found between the two groups. The results of this study are compared with those of a similar study carried out by Sager et nl. in 1992. The cleaning aspect of lens care appeared to be better adhered to in this study than in the earlier work (97% compared with 70%), but this may be due to differences in assessment technique (demonstration compared with verbal reports). Seven percent of subjects did not rinse their lenses after cleaning in this study, similar to the finding of 10% by Sager et al. The rinsing technique was found to be deficient in 40% of the patients who rinsed their lenses. The authors report that all subjects disinfected their lenses, with 7% using an inadequate technique and 3% not renewing the solution daily. This result is better than that of Sager et al., where 16% exhibited a poor technique and 12% reused their solutions. Previous studies have shown wide variation in noncompliance in handwashing (16-50%). This study found that 22% of subjects did not always wash their hands before lens handling. Of the same subjects, 32% reported poor compliance in lens case cleaning, which is lower than previous reports of between 28 and 86%. In this study, 17% of subjects did not air dry their lens case compared with 40% in the study by Sager et al. The authors report that wearing times were exceeded in 65% of cases,which is higher than previous reports of 22 to 27%. Eighty-nine percent of the current subjects were considered compliant in replacing lensesregularly (12 lensesper month). Ninety percent of subjectsin this study regularly attended aftercare appointments, which is a superior result to that of 56% reported previously. No relationship wasfound between compliance and patient age or yearsof contact lens wear. Over 80% of patients were found to understand the reasonsfor cleaning and rinsing their contact lenses and for handwashing. Thirty percent of the contact lens casescollected at the end of the 12-month assessment period were found to be contaminated with one of more of the pseudomonas,coliform, and staphylococcus microorganisms. No significant rela-
tionship was observed between the level of compliance and the presence of case contamination. Overall, patients tended to show good compliance with lens care. Areas of noncompliance were highlighted as handhygiene, cleaning technique, lens rinsing, and overwear of lenses. The authors consider that the results may be biased toward a good outcome because the subjects were volunteers, Such subject groups have been shown to exhibit better compliance in previous research studies. Free lenses and solutions provided in the study may also have encouraged regular attendance of aftercare checks. Previous contact lens experience of all subjects may additionally have formed a good basis for correct understanding initially. Practitioners are advised to pay particular attention to emphasizing the areas subject to noncompliance in this study. It is suggested that patients should be considered as potentially noncompliant and that time should be spent assessing the patient’s lifestyle so that personalized recommendations for lens care can be made.
An Apparent pH-Induced Effect on ExtendedWear Hydrogel Lens Water Content. Lattimore MR: Optom Vis Sci 1996;73:689-694. Several authors have reported studiesassessing tear pH and hydrogel contact lens water content individually, but none have investigated the two parametersin association. The author has previously shown a correlation between stabilized hydrogel lens anterior surfacepH and precorneal tear film pH. In this study the author compareshydrogel lens water content, measuredby two methods, with lens surface pH to determine if there is a predictable tear pH-related effect on hydrogel contact lens hydration. Either 38% (polymacon) or 58% (etafilcon A) water content hydrogel lenseswere fitted on an extended-wear basisto 65 volunteers. Lenseswere removed and replaced weekly after at least one lens-freenight. Five minutes after fitting, anterior lenssurfacepH wasmeasuredin situ with a flat-surfaced, self-referenced pH electrode. This was repeated at each follow-up visit. The associatedlens water content wasalso measuredon theseoccasionsby gravimetric and/or by refractive analysis. Gravimetric analysis was performed, for all 38% and half of the 58% water content lenses, by means of an analytical scale in a controlled environmental chamber that wasmaintained at ocular temperature. After reference standards were compiled, the change in lens weight from the fresh, hydrated state to the completely dehydrated state was usedto calculate the initial lens water content. Refractive analysis was performed on all 58% water content lenseswith a handheld Abbe refractometer. The two methods of lens water content analysiswere found to be comparable. Anterior lens surface pH increased significantly and nonlinearly (from approx. pH 7.0-7.45) over the first 2 days of extended lens wear for both types of contact lens.
ICLC, Vol. 24, March/April
1997
71
70
ICE,
Vol.
24,
March/April
1997
criteria and suggest that its diagnostic specificity may he increased by changing the SlT cut-off from 10 mm/5 minutes to 5 mm/5 minutes, with a decreased BUT cut-off also being of possible value.
Diurnal Variation
in Human Cornea1 Thickness.
Harper CL, Boulton ME, Bennett D, Marcyniuk A, JarvisEvans JH, Tulle AB, Ridgway AE: Br J O@u&nol 1996; 80:1068-1072. The physiologic status of the cornea can be evaluated from measurements of cornea1 thickness. The closed eyelids during sleep induce a degree of hypoxia in the normal healthy eye. Lactate in the cornea, which arises from anabolic metabolism, causes an osmotic influx of water. On eye opening, the cornea rapidly regains its normal thickness, although other factors such as tear film evaporation, intraocular pressure, and body temperature are also believed to affect cornea1 thickness. This study examines diurnal variation in human cornea1 thickness over a 48.hour period, using ultrasonic pachymetry. Eight healthy non-contact lens-wearing individuals ranging in age from 10 to 63 years participated in the study. All cornea1 thickness measurements were made in the subjects’ homes. Measurements were taken within the hour before sleep; immediately on waking; at 15, 30, and 45 minutes: at 1, 1.5, 2, 2.5, and, 3 hours; and at two-hourly intervals thereafter throughout the remainder of the day. Mean cornea1 thickness for all subjects was found to be 546 ? 14 pm. The mean overnight increase in central cornea1 thickness was 5.2%. For all but one subject, this was lower than the degree of diurnal variation (mean, 7.2%). No consistent pattern of variation was observed for the eight subjects throughout the waking hours. For three subjects, the first reading taken on eye opening was not the highest and cornea1 thickness continued to rise. There was found to be significant intersubject differences in the extent of overnight (1.9-12.6%) and maximum diurnal variation (2.1-14.3%). No overall gender differences in cornea1 thickness were observed. The study confirms previous findings of increased corneal thickness during eye closure, although the levels in this study were found to be higher than published reports of 3.0 to 4.4%. Considerable variation in cornea1 thickness during waking hours was also demonstrated by the authors. This suggests that the overnight change in human cornea1 thickness, previously assumed to be the maximal change, does not fully represent diurnal variation.
A Prospective Study of Noncompliance Lens Wear. Claydon BE, Nathan 1996;19(4):133-140. Contact
lens-related
in Contact
N, Woods C: +I Br Contact Lens Assoc
problems,
and ultimately
failure,
have
Craig and Blades been attributed to noncompliance in hygiene, lens care, and attendance of aftercare appointments. To determine the effect of a greater level of education on compliance, a prospective, randomized, controlled, and double-masked study is described. In the study, half of a group of 80 experienced contact lens patients were exposed to a “compliance enhancement strategy” in addition to a standard level of contact lens instruction, which was given to the remaining subjects. The strategy comprised extra education with a video, booklets, posters, a checklist, and a health-care contract. Free solutions (ReNu Multipurpose) and contact lenses (Medalist 38) were supplied to all patients. At a 12-month aftercare check, compliance levels were assessed by means of a demonstration and questionnaire. Both groups of subjects participating in the study were generally found to be compliant with successful contact lens wear and maintenance. No significant difference was found between the two groups. The results of this study are compared with those of a similar study carried out by Sager et nl. in 1992. The cleaning aspect of lens care appeared to be better adhered to in this study than in the earlier work (97% compared with 70%), but this may be due to differences in assessment technique (demonstration compared with verbal reports). Seven percent of subjects did not rinse their lenses after cleaning in this study, similar to the finding of 10% by Sager et al. The rinsing technique was found to be deficient in 40% of the patients who rinsed their lenses. The authors report that all subjects disinfected their lenses, with 7% using an inadequate technique and 3% not renewing the solution daily. This result is better than that of Sager et al., where 16% exhibited a poor technique and 12% reused their solutions. Previous studies have shown wide variation in noncompliance in handwashing (16-50%). This study found that 22% of subjects did not always wash their hands before lens handling. Of the same subjects, 32% reported poor compliance in lens case cleaning, which is lower than previous reports of between 28 and 86%. In this study, 17% of subjects did not air dry their lens case compared with 40% in the study by Sager et al. The authors report that wearing times were exceeded in 65% of cases,which is higher than previous reports of 22 to 27%. Eighty-nine percent of the current subjects were considered compliant in replacing lensesregularly (12 lensesper month). Ninety percent of subjectsin this study regularly attended aftercare appointments, which is a superior result to that of 56% reported previously. No relationship wasfound between compliance and patient age or yearsof contact lens wear. Over 80% of patients were found to understand the reasonsfor cleaning and rinsing their contact lenses and for handwashing. Thirty percent of the contact lens casescollected at the end of the 12-month assessment period were found to be contaminated with one of more of the pseudomonas,coliform, and staphylococcus microorganisms. No significant rela-
tionship was observed between the level of compliance and the presence of case contamination. Overall, patients tended to show good compliance with lens care. Areas of noncompliance were highlighted as handhygiene, cleaning technique, lens rinsing, and overwear of lenses. The authors consider that the results may be biased toward a good outcome because the subjects were volunteers, Such subject groups have been shown to exhibit better compliance in previous research studies. Free lenses and solutions provided in the study may also have encouraged regular attendance of aftercare checks. Previous contact lens experience of all subjects may additionally have formed a good basis for correct understanding initially. Practitioners are advised to pay particular attention to emphasizing the areas subject to noncompliance in this study. It is suggested that patients should be considered as potentially noncompliant and that time should be spent assessing the patient’s lifestyle so that personalized recommendations for lens care can be made.
An Apparent pH-Induced Effect on ExtendedWear Hydrogel Lens Water Content. Lattimore MR: Optom Vis Sci 1996;73:689-694. Several authors have reported studiesassessing tear pH and hydrogel contact lens water content individually, but none have investigated the two parametersin association. The author has previously shown a correlation between stabilized hydrogel lens anterior surfacepH and precorneal tear film pH. In this study the author compareshydrogel lens water content, measuredby two methods, with lens surface pH to determine if there is a predictable tear pH-related effect on hydrogel contact lens hydration. Either 38% (polymacon) or 58% (etafilcon A) water content hydrogel lenseswere fitted on an extended-wear basisto 65 volunteers. Lenseswere removed and replaced weekly after at least one lens-freenight. Five minutes after fitting, anterior lenssurfacepH wasmeasuredin situ with a flat-surfaced, self-referenced pH electrode. This was repeated at each follow-up visit. The associatedlens water content wasalso measuredon theseoccasionsby gravimetric and/or by refractive analysis. Gravimetric analysis was performed, for all 38% and half of the 58% water content lenses, by means of an analytical scale in a controlled environmental chamber that wasmaintained at ocular temperature. After reference standards were compiled, the change in lens weight from the fresh, hydrated state to the completely dehydrated state was usedto calculate the initial lens water content. Refractive analysis was performed on all 58% water content lenseswith a handheld Abbe refractometer. The two methods of lens water content analysiswere found to be comparable. Anterior lens surface pH increased significantly and nonlinearly (from approx. pH 7.0-7.45) over the first 2 days of extended lens wear for both types of contact lens.
ICLC, Vol. 24, March/April
1997
71