Anomalies of binocular function in patients with longstanding asymmetric keratoconus.

AIMS: To study binocular function in patients with longstanding asymmetric keratoconus. METHODS: In 20 adult patients with longstanding asymmetric keratoconus managed with a scleral contact lens a full clinical and orthoptic assessment was performed with and without the scleral contact lens in the poorer eye. RESULTS: All 20 patients had a corrected acuity of at least 6/9 in their better eye. With the scleral lens in situ the acuity of the poorer eye ranged from 6/6 to 6/60 and without the lens from 6/18 to hand movements. Patients were aged from 18 to 68 years and had worn a scleral contact lens for between 3 and 106 months. Without the contact lens in their poorer eye all patients had a small exotropia and all showed suppression, with the exception of one patient who had a right hypertropia with diplopia. With the scleral lens in situ 12 patients had an exophoria or esophoria, six a microexotropia, and two a manifest exotropia with suppression. CONCLUSIONS: Binocular function breaks down in some adult patients with longstanding asymmetric keratoconus. This is probably caused by longstanding unilateral visual deprivation. There are similarities to the breakdown of binocular function seen in some patients with a longstanding dense unilateral adult onset cataract who can develop intractable diplopia following cataract surgery.

Scleral contact lenses for overnight wear in the management of ocular surface disorders.

PURPOSE: To describe the use of overnight wear scleral contact lenses (Scl CLs). The authors describe 7 patients using this modality of contact lens wear. Most of the lenses were made from highly gas-permeable materials, but a long-standing case is also reported when the lenses were made from PMMA, which is impermeable to gases. BACKGROUND: There is a range of therapeutic indications for the use of Scl CLs. The development of rigid gas-permeable (RGP) materials has widened this range. CASE REPORTS: Seven case reports are presented which describe patients in whom severe ocular surface disease has been managed with overnight-wear Scl CLs. The indications were: corneal exposure, post-radiotherapy complications, Stevens Johnson disease, recurrent erosion and congenital or post-surgical lid defects. CONCLUSION: Scl CLs provide a therapeutic option for a range of complicated corneal and ocular surface conditions for which the treatment by other methods is either unsuitable or less effective. They have several advantages over silicone rubber and hydrogel lenses. The relative ease of handling for some patients allows removal for cleaning, their rigidity gives stability and a high degree of protection to the ocular surface, and the presence of a pre-corneal fluid reservoir optically neutralises an irregular corneal surface. Highly oxygen-permeable materials enable consideration of overnight wear in appropriate circumstances.

The unique role of scleral lenses in contact lens practice.

The advantages and disadvantages of scleral lenses are reviewed. The indications for scleral lenses are cases where other types of contact lens fail to provide a satisfactory result. In other cases, the intrinsic nature of scleral lenses makes them the modality of first choice. Both the traditional approach to fitting scleral lenses and the procedures for fitting contemporary gas permeable designs are described.

A study of 530 patients referred for rigid gas permeable scleral contact lens assessment.

PURPOSE: The purpose of this study was to analyse the current application of scleral contact lenses in two specialist centres. METHODS: The case notes of 530 patients assessed for fitting or refitting with rigid gas permeable (RGP) scleral lenses were retrospectively analysed to determine the indication for contact lenses and the outcome. Scleral lenses had been offered as a conservative management option in suitable cases for a variety of visual and medical indications. RESULTS: Various types of primary corneal ectasia, ranging from low grade to advanced, including keratoconus, keratoglobus, and pellucid marginal degeneration, formed 53.0% of the total referred for assessment. The other principal indications for contact lenses were corneal transplant (15.8%), aphakia (10.3%), high myopia (8.9%), and various ocular surface disorders (8.2%). Sixty percent continued to use scleral lenses, 42.9% RGP, and 17.1% polymethylmethacrylate lenses. Twenty-two percent discontinued scleral lens wear or failed a trial of scleral lenses, with 9.3% in progress at the time of assessment and 8.7% lost to follow-up. CONCLUSIONS: In the authors' opinion, scleral lenses have retained their traditional role in the management of complex ametropia and ocular surface disease. That role has been further enhanced by the application of gas permeable materials.

Scleral lens induced corneal swelling: what is the effect of varying Dk and lens thickness?

PURPOSE: Scleral lenses remain an option for visual rehabilitation under some circumstances or when there are specific therapeutic indications. Wearing is often limited with polymethylmethacrylate lenses, but rigid gas permeable (RGP) scleral lenses offer a physiological improvement as measured with central corneal swelling. This study aimed to determine central corneal swelling with lenses of different oxygen transmissibilities and thicknesses. METHODS AND RESULTS: Central corneal swelling was measured in four normal subjects wearing sealed RGP scleral contact lenses for 3 hours. The lenses used were of Dk 32, 59, and 115 with thicknesses of 0.15, 0.30, 0.60, and 1.20 mm. A reduction in central corneal swelling was associated with an increase in Dk and a reduction in lens thickness (P < 0.05). This relationship was found to be non-linear for higher transmissibilities. CONCLUSIONS: The physiological improvement as measured by central corneal swelling was reduced with thin high Dk lenses, suggesting diminishing returns for further increases in Dk. For usual scleral lens thicknesses of 0.6 mm in a material with a Dk of 115, the mean central corneal swelling induced was less than 3%.

Medical applications of scleral contact lenses: 1. A retrospective analysis of 343 cases.

The medical indications for, and outcome of scleral contact lens wear in 517 eyes of 343 patients attending a Scleral Contact Lens Clinic during a 5-year period from July 1988 to June 1993 were analysed. Keratoconus was the most common condition requiring scleral lens wear (36.2%), followed by aphakia (18.4%), postpenetrating keratoplasty (12.0%), irregular astigmatism secondary to corneal disease (12.0%), high myopia (12.8%), and ocular surface disorders (6.4%). The main indication was visual (85.8%), whereas therapeutic indications accounted for 8.2% of cases. Seventy-six percent of cases had previously failed with other types of contact lenses. The majority of patients were initially fitted with impression moulded polymethylmethacrylate (PMMA) lenses (90.5%); other scleral lens types included preformed PMMA lenses, preformed high Dk gas-permeable (GP) lenses, and a GP/PMMA hybrid scleral lens design. Initial scleral lens fitting was successful in 93.2% of cases, and 71% remained successful with a mean duration of 11.8 years' follow-up. Complications included corneal vascularisation (13.3% of eyes), episodes of corneal oedema (7.4%), corneal abrasion (3.1%), and giant papillary conjunctivitis (1.7%). In addition to 19 eyes initially fitted with GP lenses, there were 99 eyes initially wearing PMMA lenses that were subsequently refitted with GP scleral lenses.

Medical applications of scleral contact lenses: 2. Gas-permeable scleral contact lenses.

The indications and outcome of the wear of gas-permeable (GP) scleral contact lenses in 118 eyes of 85 patients attending a Scleral Contact Lens Clinic during a 5-year period from July 1988 to June 1993 were analysed. Ninety-nine eyes (83.9%) were originally fitted with PMMA lenses and were subsequently changed to GP lenses, whereas 19 (16.1%) were fitted with GP lenses from the outset. The mean duration of GP scleral lens wear was 15.3 months, with a range between 3 and 58 months. The indications for refitting the cases previously wearing PMMA scleral lenses with GP material were related to problems of chronic hypoxia. Thirty-three eyes (26.8%) had previous episodes of corneal oedema, and of the 27 that had a minimum of 3 months' follow-up, none experienced further episodes of oedema. Of the 32 eyes (26%) that had developed corneal vascularisation associated with PMMA scleral lens wear, two eyes were noted to have significant vessel regression after a period of GP wear, whereas in the remainder of cases, vessels remained static and nonprogressive. Thirty additional eyes (24.2%) experienced inadequate wear times associated with discomfort, and in these eyes the change to GP scleral lenses produced a statistically significant reduction in the inability to wear lenses beyond 4 h (p < 0.05).