Siva Balasubramanian, MBBS, DO is a clinician scientist and recently completed a PhD investigating tear film proteomics in keratoconus at the Brien Holden Vision Institute, Australia.The uses of scleral contact lenses are not well appreciated in clinical practice. The reason for this might be lack of training and unwarranted doubts in fitting these lenses. Siva Balasubramanian reviews a 2005 article by Kenneth W. Pullum et al. at Moorfields Eye Hospital, London, which emphasizes the role of scleral contact lenses in the management of various ocular conditions.
Pullum KW, Whiting MA, Buckley RJ. Scleral contact lenses: the expanding role. Cornea. 2005;24(3):269-77.
Pullum et al. conducted a retrospective analysis based on a database of 1003 patients (1560 eyes) of existing or new referrals for scleral contact lens fittings between September 1999 and May 2003. The information in this database included patient age, gender, description of the scleral lens, corrected visual acuity and indications for contact lens wear.
Conditions treated
Keratoconus or other primary corneal ectasias (59.9%), corneal transplants (18.7%) and ocular surface diseases (11.3%) were the three major ocular conditions managed by scleral lenses in this study, in addition to aphakia (2.6%), myopia (2.3%) and ptosis (1.8%). The authors have compared these data with their previous studies (1984 and 1996) and found an increasing trend in the percentage of scleral contact lens wear associated with primary corneal ectasia, corneal transplants and ocular surface disease.
Wearing schedules
Wearing schedules were flexible and varied. Some patients preferred to wear lenses during working hours, others on weekends or during leisure time. Many patients alternated between corneal and scleral contact lenses.
This information may be useful for practitioners deciding possible strategies to manage a particular ocular condition. The message is clear: Patients with special cases are willing to be flexible to achieve visual correction beyond the use of one particular contact lens design.
Fifty-nine percent of patients from this cohort were able to wear scleral contact lenses for 10 hours or more. Patients prescribed with these lenses to alleviate ocular discomfort wore the lenses all day. The main reason for fitting scleral lenses was unstable lens fit, uncomfortable wearing experience or inadequate handling skills with other lens types.
Increase in wear of scleral lenses
The total number of cases with primary corneal ectasia and corneal transplants fitted with scleral contact lenses increased dramatically, compared to the authors’ 1984 data. The authors mention that the availability of high oxygen permeable rigid gas permeable materials, newer designs and easier fitting techniques have significantly improved patients’ tolerance of these lenses. In the past, managing cases of primary corneal ectasia and corneal transplants was challenging but now these cases can be successfully managed using scleral contact lenses.
Interestingly, the use of scleral contact lenses in ptosis increased between 1999 and 2003. An increase in the number of people with ocular surface disease wearing scleral lenses was noted as well. The authors suggest that if overnight wear of contact lenses is not a requisite to manage ocular surface disease, scleral lenses can be considered when corneal hydration or ocular protection is essential. Potential applications of scleral lenses include Stevens-Johnson disease, mucous membrane disorders and exposure keratitis.
Visual performance
Eight-five percent of the patients with primary corneal ectasia had visual acuities <6/18, of which 30% had a visual acuity of 6/9 and only 14% had a visual acuity of 6/6.
The corneal transplant group had a similar distribution, with 84% of the subjects improving to <6/18 but 30% had 6/6, and 40% had 6/9, recording better 6/9 and 6/6 visual acuity than the group with primary corneal ectasia.
Visual performance was poor in the group with ocular surface disease; only 50% achieved <6/18 visual acuity and more patients had 6/60 or less compared to any other group. These patients mainly wore scleral lenses to retain hydration or ocular comfort in the non-sighted eye.
The myopes wearing scleral lenses had an even distribution of visual acuity, ranging from 6/6 to <6/60 and aphakes had a peak visual acuity at 6/9.
Subjects with keratoconus
The most common type of primary corneal ectasia is keratoconus, and contact lenses represent the management of choice in 90% of these patients.3 Scleral lenses are usually indicated during the advanced stages of primary corneal ectasia; however, with recent advances, mild stages can also be managed successfully. Scleral lenses can be considered if corneal RGP lenses do not offer acceptable visual acuity or adequate wearing time in patients with keratoconus.4
Keratoconus is the leading indication for corneal transplantation in many countries.5 In post-transplant corneas, irregular astigmatism, spherical anisometropia and astigmatic anisometropia are the main optical indications for use of contact lenses. The tear film trapped between the scleral lens and the graft neutralizes the post-surgical corneal astigmatism, thus improving visual acuity and ocular comfort, in most cases.
Subjects with ocular surface disease
The patients in the ocular surface disease study group were wearing scleral lenses mainly to improve corneal hydration and comfort in the affected eye with poor visual acuity. The oxygenated tear film filled behind the scleral lens acts as a precorneal fluid reservoir, providing continuous hydration to the cornea.
Scleral lenses might have significant therapeutic effects, particularly in the management of exposure keratitis and mucous deficiency syndromes. However, the authors do not advise the use of scleral lenses as the first line of management in ocular surface disease, since other lenses such as hydrogel or silicone hydrogel, limbal diameter rigid gas permeable lenses and silicone elastomer lenses have been used with favourable results.
Conclusion
The expanding role of scleral contact lenses in the management of primary corneal ectasia, post-corneal transplantation and ocular surface disease is evident from the present review. The introduction of newer rigid gas permeable materials and scleral lens designs has enabled the widespread use of these lenses to manage irregular corneas and some ocular surface disorders. The oxygenated precorneal fluid reservoir available during scleral lens wear neutralizes the astigmatism following corneal surgery and has therapeutic effects in treating corneal hydration problems.
An important message from this analysis is that patients are willing to try these contact lenses in a flexible manner in order to improve their visual experience and ocular health.
References
1. Bier N. The practice of ventilated contact lenses. Am J Optom Arch Am Acad Optom 1949;26(3):120-7.
2. Pullum KW, Stapleton FJ. Scleral lens induced corneal swelling: what is the effect of varying Dk and lens thickness? Clao J 1997;23(4):259-63.
3. Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42(4):297-319.
4. Schornack MM, Patel SV. Scleral lenses in the management of keratoconus. Eye Contact Lens 2010;36(1):39-44.
5. Wagoner MD, Ba-Abbad R. Penetrating keratoplasty for keratoconus with or without vernal keratoconjunctivitis. Cornea 2009;28(1):14-8.
