Therapeutic treatment of keratoconus: a survey of local optometric practice criteria.

BACKGROUND: Defining the threshold for therapeutic and surgical intervention in patients with keratoconus presents a considerable challenge given the lack of clear, evidence-based data. Little is known about the patterns of practice and referral criteria of optometrists within Australia. METHODS: All members of the NSW branch of Optometrist Association Australia were invited to complete an online survey in January 2013. This survey was designed to elicit practice information regarding the evaluation and therapeutic treatment of patients with keratoconus in the optometric setting. RESULTS: Responses were received from 71 optometrists, of whom 65.2 per cent had 15 years or greater experience as an optometrist. Many (35.4 per cent) responded that they prescribed soft contact lenses daily. This percentage dropped to 9.2 per cent for rigid gas-permeable lenses (RGP), although 47.7 per cent said they would prescribe RGP lenses at least once per month. The main barriers to prescribing were experience with fitting RGP lenses, time and low market demand. In terms of patient referral to an ophthalmologist, the results were variable, with 34.4 per cent stating that they would refer on progression of corneal signs, 23.4 per cent suggesting no set time and 7.8 per cent would refer on initial diagnosis. Many optometrists (62.9 per cent) would refer a patient for possible surgery, when visual acuity dropped to between 6/9 and 6/12. The size or location of the practice was not associated with the number of newly diagnosed cases of keratoconus. Optometrists with greater experience were more likely to prescribe RGP lenses and co-manage patients with ophthalmologists. Ownership of a corneal topographic unit suggested an increased likelihood of prescribing RGP lenses but did not appear to alter referral patterns. CONCLUSION: Optometrists have an integral role in the diagnosis and management of patients with keratoconus. Our survey provides a basic snapshot of current, local practice. Additionally, ophthalmology should continue to work with optometry to develop guidelines for referral and co-management to optimise future outcomes for our patients.

Is the superior cornea continuously swollen?

BACKGROUND: During waking hours, the upper eyelid typically covers the superior two millimetres of the cornea. This partial oxygen barrier is the presumed cause of the reversibly elevated epithelial oxygen uptake in this region of the cornea. We studied the thickness profile of the vertical corneal meridian before and after extended exposure to a uniform hypoxic stimulus to ascertain the extent of chronic superior corneal swelling that might be attributable to coverage by the upper lid. METHODS: Each of 16 male subjects, age 24 to 40 years, wore a uniformly thick polymacon lens (Dk/L = 5.7 x 10-9 cm ml O2/s ml mmHg) on one eye for four hours with the eyelid patched. Thickness was measured at five sites across the vertical corneal meridian prior to and immediately after patching. Baseline thickness and swelling were compared at the superior and inferior edges of selected central chord diameters. RESULTS: At baseline, the superior cornea was, on average, 31 mm thicker (p = 0.0002) at the 7.1 mm chord and 9 mm thicker (not significant) at the 3.75 mm chord, compared to the inferior cornea at the corresponding chords. Mean corneal swelling ranged from 70.5 mm centrally to approximately 48 mm at the 7.1 mm chord diameter. The extent of swelling at the corresponding superior and inferior sites was virtually identical for both chord diameters. CONCLUSION: Although the superior cornea is significantly thicker than the inferior cornea, this difference does not appear to be immediately related to the chronic differences in open eye oxygen tension between the superior and inferior regions.