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.     

The effect of long-term, daily contact lens wear on corneal sensitivity

PURPOSE: To assess the effect of long-term, daily-wear soft contact lenses and rigid gas permeable (RGP) contact lenses on corneal sensitivity using a noninvasive, air-pulse stimulus. METHODS: The central and peripheral (temporal, medial, inferior) corneal sensation thresholds of 40 non-lens wearers, 40 soft lens wearers, and 40 RGP lens wearers were assessed using the Non-Contact Corneal Aesthesiometer (NCCA). The individuals who wore contact lenses were grouped according to the number of years of lens wear (10 years or less, 11-20 years, and 21 years or more). RESULTS: Although a significant reduction in corneal sensitivity was found between the contact lens wearers and non-lens wearers (p = 0.000), no difference was found between the two lens-type subgroups (p = 0.939). This pattern of significance was repeated at each of the peripheral test locations. No relationship between corneal sensitivity and years of lens wear was found centrally (r2 = 0.004) or at any of the peripheral test locations. No significant difference was found between the central corneal sensation thresholds for the different subgroups of lens wear duration (p = 0.469) or for any of the peripheral test locations. CONCLUSIONS: Both soft and RGP lens wear produce a similar type of corneal sensitivity loss, although the mechanism for this loss is different for the two lens types. The extent of sensitivity loss is not related to the duration of lens wear and appears to plateau after the first few months of wear. No topographical variation in sensitivity loss was found with lens type or with the duration of lens wear.     

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.     

Corneal trauma from overnight wear of rigid or soft contact lenses.

To evaluate the mechanical or biochemical insult to the cornea induced by overnight rigid gas permeable (RGP) or soft contact lens (SCL) wear, punctate, stipple staining and corneal blotting were evaluated by biomicroscopy in a group of 23 subjects who participated in a single overnight in-laboratory test session. The soft lens-wearing corneas typically showed greater area of staining along with corneal blotting in comparison to RGP-wearing corneas which showed smaller areas of corneal staining, even in the presence of RGP adherence, and no corneal blotting. We investigated the effect of hypoxia on corneal staining by having subjects wear an RGP lens of Dk = 150 on one eye and a soft lens of Dk = 9 on the fellow eye. Pachometry measurements immediately following eye opening showed an average central corneal swelling of 5 percent for the RGP lens-wearing eye and an average of 11 percent for the SCL-wearing eye. It is likely that the differences in corneal effects of RGP and SCL overnight lens wear are the result of differences in the nature of rigid versus soft contact lens adherence.     

Overnight corneal reshaping versus soft disposable contact lenses: vision-related quality-of-life differences from a randomized clinical trial.

PURPOSE: The purpose of this article is to evaluate patients' visual acuity, symptoms, and perceptions of vision-related quality of life in a randomized crossover clinical trial of overnight corneal reshaping (OCR) and daily wear soft lenses (SCL). METHODS: Qualified subjects were randomly assigned to wear one mode of contact lens for 8 weeks and then, after a washout period, they wore the alternate mode for 8 weeks. On concluding each contact lens wear mode, subjects completed the NEI-RQL42 questionnaire. During the SCL mode, subjects wore lenses during their waking hours. During the OCR mode, subjects wore lenses only while sleeping. Soft lenses were Biomedics 55 2-week disposable lenses. OCR lenses were CRT lenses by Paragon. (Three subjects were fit with custom-designed OCR lenses in Boston XO material, manufactured by Art Optical.) LogMAR acuity was measured and slit lamp evaluation was performed at specified intervals during follow up. After completing both phases of the study, patients chose which mode they preferred. RESULTS: Of 81 enrolled patients, 65 completed both phases and 16 dropped out during the study. Significant differences (p<0.01) favoring SCL wear included better visual acuity and less trouble with glare. Significant differences (p<0.01) favoring OCR wear included less activity limitations, less trouble with symptoms, and less dependence on refractive correction. Of 65 completing both phases, 44 preferred the OCR lenses and 21 preferred the soft lenses. Subjects who preferred the OCR lenses were less myopic and had steeper K readings at baseline, and showed less difference between visual acuity during OCR wear and visual acuity with SCL. CONCLUSION: In subjects with mild myopia who experienced both SCL and OCR, better visual acuity and less glare resulted from SCL wear, whereas activity limitations, symptoms, and dependence on refractive correction were less troublesome with OCR wear. When the study was completed, 67.7% chose OCR lenses worn only while sleeping, whereas 32.3% preferred 2-week disposable soft lenses worn during the day as their preferred correction.     

Hypoxic effects on the anterior eye of high-Dk soft contact lens wearers are negligible.

PURPOSE: To determine whether the eyes of high-Dk soft contact lens wearing subjects can be discriminated from non-contact lens wearing subjects. METHODS: This study was a prospective masked assessment of 32 subjects, 16 of whom wore experimental high-Dk soft contact lenses and 16 of whom did not wear contact lenses. Subjects wore high-Dk lenses on a 30-night replacement schedule for an average of 9 months. Tear film characteristics, staining and vascularization of the cornea, conjunctival staining, and the presence of microcysts in the corneal epithelium were assessed using slitlamp microscopy. The endothelium was examined for polymegethism. RESULTS: No differences were found between the two groups in any of the variables that were examined (p > 0.05) except that the high-Dk lens wearing group had about twofold more tear film debris and 2.5-fold more severe conjunctival staining (p < 0.05). CONCLUSIONS: Hypoxia-associated effects were not apparent in the eyes of subjects wearing experimental high-Dk soft contact lenses. Conjunctival staining can generally distinguish lens wearers from non-lens wearers and can be used to discriminate between high-Dk lens wearing subjects and non-lens wearing subjects.     

The effect of rigid gas permeable lenses on corneal sensitivity

Long term wear of hard (PMMA) contact lenses decreases corneal sensitivity. Clinicians have noted that in some patients who are refitted with rigid gas permeable (RGP) lenses, there is often an increase in lens awareness. To document this symptom, we monitored changes in corneal sensitivity of long term PMMA wearers who were refitted with RGP lenses. Corneal sensitivity measurements were conducted over a 6-month period. During this time, corneal touch threshold decreased to normal levels within a few weeks after refitting with RGP lenses. These results suggest an oxygen dependency factor in the control of corneal sensitivity accompanying contact lens wear.     

Corneal swelling with overnight wear of scleral contact lenses

PURPOSE: The management of some ocular surface diseases may be enhanced by the overnight wear of a rigid gas-permeable (RGP) scleral contact lens (ScCL). There is little information of the hypoxic effect of extended RGP ScCL wear. The authors measured the corneal swelling after overnight wear of a rigid gas permeable scleral contact lens in normal subjects. METHODS: Four subjects wore an RGP ScCL overnight in 1 eye only on 4 occasions. The following morning the lens was removed immediately before optical pachymetry, and the corneal thicknesses of both eyes were measured by a masked observer. On another four occasions optical pachymetry was performed, but the lens was not worn the previous night. For each subject the lens was of the same thickness. Specular microscopy was used to estimate endothelial cell density. RESULTS: There were no adverse effects, and subjects reported no difficulties in handling the lenses. Overnight wear of ScCL induced a variable amount of corneal swelling among subjects from 4.9% to 17.5%. The overnight swelling correlated strongly with endothelial cell density. CONCLUSIONS: Overnight wear of ScCL caused an increased degree of corneal swelling compared with daytime wear. This degree of swelling should not rule out overnight therapeutic ScCL wear if the disease process is deemed to be more damaging than the hypoxic effect of an RGP ScCL worn overnight. However, when used for refractive correction, they should not be left in overnight.     

A European fitting philosophy for aspheric, high-Dk RGP contact lenses.

Microbial keratitis, the most serious complication of contact lens wear, is most frequently associated with soft contact lenses. Rigid gas permeable (RGP) lens wearers are less often affected. Increased use of high-Dk RGP lenses could reduce the number of cases of microbial keratitis. In Europe, aspheric high-Dk RGP lenses are very popular. This article presents practical guidelines for computer-aided fitting of aspheric RGP lenses. Base curve selection using the keratometer to determine the corneal topography is described. This method, which is inexpensive and time-saving, is suitable for fitting cosmetic contact lenses or lenses used in treating such corneal pathology as keratoconus.     

Rigid gas-permeable contact lenses are a safe and effective means of treating refractive abnormalities in the pediatric population.

PURPOSE: This study examined the safety, efficacy, and tolerance of rigid gas permeable (RGP) contact lenses in a pediatric population. The study also considered the economic impact of RGP contact lens wear in children. METHODS: Retrospectively, we reviewed 12 consecutive charts of children with multiple diagnoses of trauma (n = 5), high myopia (n = 1), surgical aphakia (n = 5), corneal scar (n = 4), and microophthalmia (n = 2) who were considered for RGP contact lenses. RESULTS: Fifteen eyes of 12 patients were originally fit with RGP contact lenses. Ten of 12 (83.3%) children were still wearing their RGP contact lenses after a mean follow-up of 17.8 months. Two of 12 patients (16.7%) stopped RGP use. Two of 10 (20%) patients wore their RGP contact lenses for extended wear. Eight of 10 (80%) patients were successful in daily insertion and removal of RGP contact lenses. There were no adverse events secondary to contact lens use in any patients. An average of 2.18 (range: 0.97-4.55) replacement lenses were needed per patient per 6 month interval. CONCLUSIONS: RGP contact lenses are a safe, effective, and tolerable means of treating refractive abnormalities in the pediatric population. With proper education, families can be successful with daily RGP insertion and removal. RGP contact lenses have the advantage of excellent oxygen transmissibility, low bacterial and protein adherence, and the potential to correct irregular astigmatism. Disadvantages include frequent lens replacement.     

Effects of low and hyper Dk rigid gas permeable contact lenses on Bcl-2 expression and apoptosis in the rabbit corneal epithelium.

PURPOSE: To study Bcl-2 expression and apoptotic cell shedding of the rabbit corneal epithelium during extended wear of low and hyper Dk rigid gas permeable (RGP) contact lenses. METHODS: Rabbits were fit with either a low or a hyper Dk RGP lens (Dk/Ltotal= 10 and 97). The rabbits wore the lenses for either 24 hours, 3 days, or 1 week at which point they were humanely sacrificed. Immunocytochemistry and western blot analyses were performed to detect Bcl-2 in the corneal epithelium; TUNEL assay (TdT-mediated dUTP nick-end labeling) was used to identify apoptotic epithelial cells. RESULTS: 1) Immunocytochemistry: In the normal cornea, antibodies to Bcl-2 uniformly stained nuclei of all epithelial cell layers. Occasional surface epithelial cells, however, showed no anti-Bcl-2 nuclear staining; concomitant TUNEL assay revealed that all TUNEL-labeled-surface cells were Bcl-2 negative. By contrast, RGP contact lens wear, regardless of test lens oxygen transmissibility or lens wearing interval, significantly decreased both the total number of Bcl-2 negative and TUNEL-labeled cells on the epithelial surface (P < 0.05). In addition, contact lens wear was associated with labeling of keratocytes with TUNEL assay in the anterior stroma. 2) Western blot analysis: Total epithelial layer Bcl-2 expression was markedly decreased in the low Dk lens test group but was similar to control values in the hyper Dk lens test group. CONCLUSION: Bcl-2 protein seems to play an important role in the regulation of apoptotic cell shedding in the normal rabbit corneal epithelium. The identical staining pattern was seen in previous studies of the normal human cornea. RGP contact lens wear, however, appears to block the changes in Bcl-2 protein prior to apoptotic surface cell shedding, suggesting a lens-related anti-apoptotic effect. Taken together, these findings may explain why contact lens wear reduces surface cell exfoliation as previously reported in human studies.     

Tolerance to different kinds of contact lenses in young atopic and non-atopic wearers.

PURPOSE: To study tolerance to three types of soft and onetype of rigid gas permeable (RGP) contact lens in young atopic and non-atopic subjects starting to wear contact lenses. METHODS: A prospective study was conducted in 73 young subjects (mean age: 18.7 years, range: 11-37 years). Each subject was allotted at random to one of four groups. Each group of subjects used a different type of contact lens for a year. Tolerance was determined by means of self-assessment by the subjects, ophthalmologic methods, and cytology. The study was conducted on a blind basis. The investigators assessing tolerance did not know what kind of lens a patient had been wearing. RESULTS: Fifty-six percent of subjects who had used soft contact lenses, but only 14% of RGP lens users described their lenses as very comfortable to wear. Sixty-three percent of non-atopic subjects but only 47% of atopic subjects described their lenses as very comfortable to wear. No differences were found between the three types of soft contact lens. Four cases of giant papillary conjunctivitis (GPC) and two cases of macropapillary reaction were recorded. No connections with atopy, type of lens, or lens care solution were found. CONCLUSIONS: Higher percentages of users of soft contact lenses than users of RGP contact lenses described their lenses as very comfortable to wear. Wearing of all types of lenses was associated with follicular or papillary reactions in some subjects. Young people can wear contact lenses safely only if monitoring takes place at least twice a year.     

Swelling and deswelling of rabbit corneas in response to rigid gas permeable, hydrogel and elastomer contact lens wear

We determined diurnal variation in corneal thickness in rabbits prior to and following overnight wear of: (i) selected rigid contact lenses with different Dk values; (ii) hydrogel lenses of low and high water content; and (iii) elastomer lenses. The degree of contact lens-induced corneal swelling observed during 24 hours of lens wear, and the rates of deswelling in the subsequent 24 hours, correlated well with the different oxygen transmissibilities of the individual RGP contact lenses. The greatest swelling (21.6 +/- 5.4%) followed the wear of PMMA lenses. The least swelling, 2.9 +/- 4.0%, followed the wear of rigid gas permeable (RGP) Menicon SF-P (melafocon A) lenses, a value nearly identical to the swelling observed in the morning following sleep without lenses, (0.0 +/- 3.1%). By contrast, low-water content hydrogel soft contact lens use was associated with drastic corneal deswelling rates (-15.1 +/- 4.5%) during the hours after lens wear. The difference between these and control corneas was significant by paired t-test (P less than 0.01). Eyes wearing high water content lenses had less deswelling than eyes with their low-water counterparts. Corneal swelling produced by elastomer lenses was similar to that seen with RGP lenses.     

Rigid gas-permeable extended wear: a comparative clinical study.

A 12-month clinical trial involving 88 subjects was undertaken to compare the clinical performance of rigid gas-permeable contact lens extended wear (EWRGP) with that of RGP daily wear (DWRGP) lenses and soft lens extended wear (SLEW) with medium water content lenses. Withdrawals from the EWRGP group tended to result from lens-related problems, whereas the SLEW withdrawals generally resulted from adverse effects on corneal physiology. Changes in spherical refractive error during the 1-year study were small (less than 1.00 D) and similar for both gas-permeable lens-wearing groups. Most of the SLEW group (58%) showed an increase in myopia and the mean increase was 0.38 D, which represented a significant difference from the EWRGP group. The EWRGP group showed a mean flattening in corneal curvature of 0.11 and 0.15 mm in the flattest and steepest corneal meridians, respectively. A positive correlation was noted between change in corneal curvature and baseline corneal astigmatism, which suggests corneal molding as a result of lid pressure as the most likely cause. The DWRGP and SLEW groups showed small, nonsignificant changes in corneal curvature. Most of the EWRGP subjects (69%) who completed the study showed increased corneal distortion. This compares with 30 and 17% with the DWRGP and SLEW groups, respectively. Likely corneal edema was a major contributory factor. For most of the slitlamp variables monitored, there were no significant differences between the groups. However, microcystic changes were detected in both EWRGP (35%) and SLEW subjects but not in the DWRGP group. Corneal staining was noted in all groups but was more prevalent among the EWRGP group. The findings of this study are discussed in relation to the clinical management of RGP extended wear.     

Corneal response to different oxygen levels during extended wear

In this study we explored the relationship between hypoxic exposure level and corneal response by assuming that the partial pressure of oxygen (PO2) under a contact lens during eye closure is directly related to oxygen transmissibility (Dk/L). To study this relationship, we monitored a group of subjects who wore RGP lenses of various Dk/L values on an extended wear basis. The results revealed that as Dk/L increases, there is a substantial decrease in overnight corneal edema and epithelial microcysts. However, other responses seemingly related to purely mechanical properties (e.g., lens adherence, corneal topographical changes, and 3-9 limbal superficial punctate keratitis) appear to be independent of Dk/L. Results also suggest that sufficient PO2 levels under a contact lens can minimize endothelial morphological changes associated with hypoxia. We conclude that metabolically driven complications accompanying RGP extended wear can be substantially eliminated with lenses having Dk/L values of 80 x 10(-9) (cm x mL O2)/(sec x mL x mm Hg) or greater.     

Giant papillary conjunctivitis associated with rigid gas permeable contact lenses

Giant papillary conjunctivitis (GPC) is an external ocular inflammatory disorder associated with contact lens wear. GPC seems to occur less frequently with hard than with soft contact lens wear. The management of soft contact lens related GPC has included refitting with hard lenses, specifically the newer rigid gas permeable (RGP) lenses. We retrospectively studied 14 RGP lens wearers in whom GPC developed. Three patients had had GPC associated with soft contact lens wear and had been fitted with RGP lenses in an effort to restore contact lens tolerance. The interval of time between the initiation of RGP lens wear and the onset of GPC was inversely related to the lens oxygen transmissibility (DK value). Ophthalmologists should be aware of the association between GPC and rigid gas permeable lens wear.     

Annexin V binding to rabbit corneal epithelial cells following overnight contact lens wear or eyelid closure.

PURPOSE: To determine the effects of open or closed eye and overnight contact lens wear on rabbit corneal epithelial surface cell death, detected by annexin V binding to cell surface phosphatidylserine and propidium iodide (PI) double-labeling. METHOD: New Zealand white rabbits (n = 42) weighing 2.5 to 3.5 kg were divided into 7 study groups: hyper Dk/t rigid gas-permeable (RGP) lens; high Dk/t RGP lens; low Dk/t RGP lens; hyper Dk/t soft lens; high Dk/t soft lens; eyelid closure; and nictitating membranectomy study group (n = 6 rabbits for each group). Each rabbit was randomly chosen to have either one eye fitted with a test contact lens or both eyelids sutured closed; the contralateral eye served as a control. Rabbits were humanely sacrificed after 24 hours. Corneal buttons including the limbus were excised and stained with annexin V-FITC and PI to identify the number of nonviable epithelial surface cells. A series of sequential microscopic adjacent fields (200 microm X560 microm) from the inferior limbus to the central cornea were evaluated using epifluorescence microscopy, and the total number of cells stained with annexin V or PI, or both, was counted in each field. RESULTS: Nonviable cells (cells with positive staining) were lowest in density at the limbus and gradually increased in numbers towards the central cornea under normal open eye conditions (P<0.05). Eyelid closure (no lens) caused a significant decrease in the numbers of nonviable cells in the peripheral and central cornea (P<0.05) but not at the limbus (P>0.05). Overnight wear of hyper Dk/t or high Dk/t RGP soft contact test lenses caused significant decreases in the numbers of nonviable cells on the central corneal surface (P<0.05). Hyper Dk/t and high Dk/t soft lenses had similar suppressive effects on the number of surface nonviable cells, independent of lens oxygen transmissibility. By contrast, the number of nonviable cells was dependent upon RGP lens oxygen transmissibility; hyper Dk/t RGP lens wear produced significantly less suppression of the number of nonviable cells in the central cornea than high Dk/t RGP lens wear (P<0.05). Wear of a nonphysiologic low oxygen transmissible RGP test lens however, produced a significant increase in nonviable cells in the central cornea. The number of nonviable epithelial surface cells was not affected by nictitating membranectomy under open eye conditions (P>0.05). CONCLUSIONS: This study revealed in the rabbit model a gradient of nonviable surface epithelial cells increasing towards the central cornea under open eye conditions and with central suppression of surface cell death following closed eye (no lens) or physiologic contact lens wear. Taken together, the results suggest that eyelid closure or contact lens wear may protect the corneal epithelial cells against the shear stress forces exerted by eyelid blinking, which are believed to drive central epithelial surface cell death and exfoliation. However, under very low oxygen tensions combined with lens effect, such as in low Dk/t RGP lens wear, surface cell death may be accelerated.     

Comparative clinical performance of rigid versus soft hyper Dk contact lenses used for continuous wear.

PURPOSE: The purpose of this study is to investigate the comparative clinical performance of two hyper Dk contact lenses: a silicone hydrogel lens (Focus Night & Day, Ciba Vision) and a rigid lens (Z-alpha, Menicon Co. Ltd.) when worn for up to 30 days of continuous wear (CW). The rigid lens was worn on an unplanned replacement basis, whereas the soft lens was replaced monthly. METHODS: One hundred subjects were recruited. Fifty neophyte subjects were randomly assigned into one of the lens types (25 subjects per lens type). Twenty-five existing daily wear (DW) rigid lens users wore the rigid study lens and 25 existing DW soft lens users wore the soft study lens. Visual acuity, lens fit, keratometry, refraction, lens surface assessment, physiological response, and subjective response were investigated at baseline and after 1 week of DW and 24 hours, 1 week, and 1, 3, 6, 9, and 12 months of CW. Analysis compared lens type (rigid vs. soft) and subject group (experienced vs. neophyte). RESULTS: Sixty-eight subjects completed the study. Visual acuity was similar for the two lens types and subject groups. Lens fit was judged to be adequate in all subjects. Corneal curvature of subjects in the rigid groups became flatter by 0.13 mm compared with 0.04 mm for subjects in the soft lens groups (F = 14.7, p = 0.0003); the refractive findings mirrored these corneal changes. The increasing rate of deposition on rigid lenses was consistent with the fact that these lenses were not replaced during the study. Conjunctival hyperemia and staining were similar for the two lens types but greater among experienced wearers at baseline (F = 13.8, p = 0.0005; F = 5.3, p = 0.02, respectively). Corneal staining was higher for the rigid lens wearers (F = 5.6, p = 0.02) but this was mainly the result of the initial higher scores in the rigid lens experienced group. The change in papillary conjunctivitis was greater for subjects in the soft lens groups than rigid lens groups (F = 4.6, p = 0.04). Comfort was initially lower for the rigid lens neophyte group (F = 4.2, p = 0.0001), but after the CW phase started, there were no differences between groups. CONCLUSIONS: Notwithstanding subtle differences in physiological responses, continuous wear hyper Dk rigid and soft silicone-containing contact lenses can be successfully worn by both those with previous contact lens experience and those with no history of contact lens wear.     

1-Day Acuvue vs. Focus Dailies: a comparison of comfort, user preference, and incidence of corneal complications.

PURPOSE: Two types of daily disposable soft contact lenses, 1-Day Acuvue (Johnson & Johnson K.K., Japan) and Focus Dailies (CIBA Vision Corp.), were compared for comfort, user preference, and any associated incidence of corneal complications. METHODS: 1-Day Acuvue and Focus Dailies were randomly prescribed for one eye each of 127 contact lens wearers. After 1 week of lens wear, user preference, anterior segment health, and tear film stability on the contact lenses were evaluated. RESULTS: Group A consisted of 45 subjects who had been wearing 1-Day Acuvue prior to the study and group B consisted of 82 subjects who had been wearing other types of soft contact lenses prior to the study. A statistically significant number of subjects in both group A and group B preferred 1-Day Acuvue. In group A there were significantly fewer corneal complications in the eyes with 1-Day Acuvue than in the eyes with Dailies. However, there was no difference in the incidence of corneal complications in group B. CONCLUSIONS: If Dailies are prescribed for current 1-Day Acuvue wearers, extra care may be required. 1-Day Acuvue lenses could be prescribed successfully for those who previously wore soft contact lenses other than 1-Day Acuvue.     

Contact lens fitting difficulties following refractive surgery for high myopia.

PURPOSE: To describe the clinical and optical problems encountered in contact lens fitting following refractive surgery for high myopia. METHODS: Following refractive surgery for high myopia (greater than -10.00 D) we corrected residual refractive errors with contact lenses in the four eyes of two patients. The first patient had undergone bilateral laser in situ keratomileusis (LASIK),with two subsequent LASIK retreatments in the left eye. Ten months later she was fit with rigid gas permeable (RGP) lenses in both eyes. The second patient had undergone a clear lens extraction in the right eye and radial keratotomy followed by photorefractive keratectomy(PRK) in the left eye. She was fit with toric soft lenses six years postoperatively. RESULTS: Final visual acuity obtained with contact lenses was 20/25-20/20 in all eyes. The first patient required significant minus lens power compensation. Furthermore, the RGP lens in the left eye was slightly decentered due to corneal irregularity induced by LASIK. The second patient had regular corneal surfaces and was successfully fit with daily wear toric soft lenses despite the 2.75 D of residual astigmatism in the left eye. CONCLUSIONS: Following refractive surgery for high myopia a proportion of patients will remain undercorrected. In these patients the alterations in corneal architecture that ensue make contact lens fitting more challenging. Patients with regular astigmatism may be fitted successfully with toric soft lenses. Patients with corneal irregularities should be fit with RGP lenses.