Kathryn Dumbleton

Vascular response to extended wear of hydrogel lenses with high and low oxygen permeability

Purpose. The purpose of this study was to determine the impact of extended wear of high and low oxygen permeability (Dk) lenses on the development or resolution of limbal hyperemia and corneal neovascularization in a randomized prospective clinical trial. Methods. Adapted daily-wear contact lens wearers were randomly assigned to one of two groups. The low-Dk group (N = 23) wore etafilcon A lenses (Dk/t = 40) for up to 7 days and 6 nights, and the high-Dk group (N = 39) wore lotrafilcon A lenses (Dk/t = 175) for up to 30 days and nights. Limbal hyperemia and neovascularization were assessed and graded during 9 months of extended wear. A stratified analysis to determine how change in ocular redness depended on initial presentation was also conducted. Results. On a 0 to 100 scale, extended wear of low-Dk lenses resulted in a 16-point increase in limbal hyperemia (p < 0.0001); no significant change occurred with the high-Dk lenses. The difference was greatest for low-Dk participants who initially presented with lower levels of hyperemia (N = 18). There was a slight resolution of redness in participants who initially presented with higher levels of hyperemia (N = 10) after wearing the high-Dk lenses. Neovascularization increased by an average of 0.5 on a scale of 0 to 4 in low-Dk lens wearers (p < 0.0001) but remained unchanged in the high-Dk lens wearers. The increase was most marked for the low-Dk group with lower levels of neovascularization at baseline. Conclusions. Subjects who wore lenses with higher oxygen permeability for 9 months of extended wear exhibited a lower vascular response of the ocular surface compared with subjects who wore lenses of lower oxygen permeability for the same period. This result was found both for the surface limbal vessels and in the deeper neovascular stromal vessels. Moderate neovascularization also developed after 3 months of extended wear of low-Dk hydrogels, whereas high-Dk lenses caused no neovascularization.

Dryness and Discomfort with Silicone Hydrogel Contact Lenses

Purpose. The purpose of this study was to determine whether symptoms of dryness and discomfort are experienced differently with silicone hydrogel lenses compared to conventional hydrogels, in symptomatic and asymptomatic subjects. Methods. Thirty-nine symptomatic and asymptomatic subjects wore four types of lenses: Focus NIGHT & DAY (CIBA Vision), Focus DAILIES (CIBA Vision), ACUVUE 2 (Johnson & Johnson Visioncare) and Proclear Compatibles (CooperVision) contralaterally for 7 hours and rated comfort and dryness on a zero-to-100 point visual analog scale at 0, 1, 3, 5 and 7 hours. Results. In both groups, no lens differences were found for comfort and dryness, but the comfort and dryness ratings of the symptomatic group decreased significantly (became worse) over the 7-hour period. Conclusions. These results demonstrate that dryness and comfort is the same over time with silicone hydrogel as with the other three lenses.

Objective and subjective responses in patients refitted to daily-wear silicone hydrogel contact lenses.

Purpose. Silicone hydrogel (SiH) lenses offer many physiological advantages for daily wear (DW) in addition to the continuous-wear modality for which they were originally developed. The purpose of this study was to investigate the clinical performance and physiological responses in a group of successful long-term wearers of conventional hydrogel lenses when refitted with DW SiH contact lenses. Methods. Eighty-seven successful soft lens wearers (8.4 ± 4.7 years of prior lens wear) participated in this study. Bulbar and limbal hyperemia were subjectively graded and digitally photographed for subsequent masked objective evaluation. Subjective symptoms were scored using visual analog scales. In addition, refractive error, corneal curvature, and corneal thickness were measured. All subjects were refitted with Focus Night & Day (lotrafilcon A) SiH lenses; however, to reduce the potential for bias, they were informed that they were being randomly assigned to wear either low oxygen permeability (Dk) lenses or high Dk SiH lenses and were “masked” as to their lens assignment. Subjects returned after 1 week, 1 month, and 2 months of DW, at which time all gradings, photographs, and measurements were repeated. End-of-day subjective symptoms were also graded periodically during the study. Results. Ninety-three percent of subjects were successfully refitted. Both objective and subjective evaluations showed that bulbar and limbal hyperemia decreased significantly in all quadrants during the study (p < 0.001), particularly for those subjects with greater baseline hyperemia (p < 0.001). Subjects reported a concurrent reduction in end-of-day dryness and improved end-of-day comfort compared with their habitual lenses (p < 0.001). No significant changes in refractive error, tarsal papillary response, corneal curvature, or corneal thickness were found during the study. Conclusions. Hyperemia in contact lens wearers may be attributed to a number of factors, including hypoxia. Refitting existing low Dk lens wearers with SiH lenses on a DW basis can result in a decrease in hyperemia, which may be significant for some subjects and also results in improvements in symptoms of dryness and discomfort.

Soft contact lens-related dryness with and without clinical signs.

Purpose. To report demographics, wearing patterns, and symptoms from soft contact lens (SCL) wearers with significant SCL-related dryness symptoms with and without significant ocular signs of dryness. Methods. In a multicenter, prospective observational clinical trial, symptomatic SCL wearers reported significant SCL-related dryness via self-administered questionnaire of frequency and intensity of dryness after a dry eye (DE) examination. DE etiology was assigned post hoc by an expert panel, and those with and without significant DE-related signs were analyzed by univariate logistic regression. Possible DE etiologies were aqueous tear deficiency, SCL-induced tear instability, meibomian gland dysfunction, or “other.” Wearers without signs that qualified for any DE etiology were designated as No DE Signs (NDES). Results. Of the 226 SCL symptomatic wearers examined, 23% were without signs, 30% had aqueous tear deficiency, 25% had SCL-induced tear instability, 14% had meibomian gland dysfunction, and 8% had “other” diagnoses. The NDES wearers had significantly longer pre-lens break-up time (9.8 vs. 6.6 s, p < 0.0001), better lens wetting (3.4 vs. 2.4 0 to 4 scale, p < 0.0001), lower levels of film deposits on lenses (0.45 vs. 0.92, 0 to 4 scale, p < 0.0001), and of most slit lamp signs. The NDES wearers were significantly more likely to be male (36% vs.19%, p = 0.013), were less likely to have deteriorating comfort during the day (81% vs. 97%, p = 0.001), reported longer average hours of comfortable wear (11 ± 3 vs. 9 ± 4 h, p = 0.014), had older contact lenses (18 ± 14 vs. 13 ± 12 days, p = 0.029), and greater intensity of photophobia early and late in the day (p = 0.043 and 0.021). Conclusions. Symptoms of dryness in SCL wearers stem from a variety of underlying causes. However, nearly one-quarter of these symptomatic SCL wearers appear to be free of signs of dryness. The effective management of CL-related dryness requires a comprehensive range of clinical assessments and the use of a diverse range of management strategies.

Effect of lens base curve on subjective comfort and assessment of fit with silicone hydrogel continuous wear contact lenses

Purpose. To study the effect of base curve on subjective comfort of silicone hydrogel extended wear lenses. Methods. Ninety-five subjects were first trial fitted with 8.6-mm base curve lotrafilcon A (Focus Night & Day) lenses and then with 8.4-mm lenses only if poor subjective comfort or poor fit was present. Comfort and fit were assessed after 15 min. Subjects with discomfort or signs of poor fit were then trial fitted with 8.4-mm lenses. Results. Of 190 eyes, 74.2% were fitted with 8.6-mm lenses, and 23.7% required 8.4-mm lenses. Two (2.1%) subjects could not be fitted with either base curve. Mean steep keratometry (K) reading for eyes dispensed with 8.6-mm lenses was 43.88 D and 45.56 D for eyes dispensed in the 8.4-mm lenses (p < 0.001). Conclusions. A clinically useful criterion showing the need for 8.4-mm lenses was steep K of ≥45.50 D; 77% of these eyes required the steeper lens for good comfort and fit. Subjective discomfort with 8.6-mm lenses was also a useful signal for the need of a steeper lens; mean comfort scores for those subjects rose from 6.33 with 8.6-mm lenses to 9.44 with the 8.4-mm lenses for eyes requiring the steeper lens (p < 0.001).

Protection from acute exposure to ultraviolet radiation by ultraviolet-absorbing RGP contact lenses*

One eye in each of 12 female pigmented rabbits was irradiated with UVB while wearing an EqualensR I rigid gas‐permeable contact lens. The other eye served as a control. The irradiance level was 625 μ W cm ‐2 (285‐315 nm total band pass) with exposure times up to 2364s. Eyes evaluated 24 h and 48 h after exposure by biomicroscopy and pachometry, and later by scanning electron microscopy (SEM). The contact lens was found to protect the central cornea from radiant exposures up to 60 times threshold. The exposed areas of cornea showed characteristic ultraviolet damage with an arc of demarcation indicating the position of the lens. With time the area formed a ridge of damaged cells (confirmed by SEM). At radiant exposure over 0.75 J cm ‐2 some oedema was seen in the ‘protected’ region, apparently by extension rather than as a direct effect. These findings suggest that in the human being exposed to ultraviolet radiation this ultraviolet‐obsorbing RPG lens would permit nasal and temporal photoketatitis with sparing of the central cornea and provide some protection of more posterior ocular structures.