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Tear production and elimination in normal eyes
Abstracts problems with tracking eye movements. convergence insufficiency. reduced fusional reserves and accommodative facility. all of which can be improved with specific exercises. attention should also be given to multisensory exercises. Visual space is a varymg mix of central and peripheral vision. The attention given to each will vary with visual task. and also from person to person. For best visual performance the correct balance between the two systems is required. If a person is too centrally orientated they tend to be \‘ery “focal” in their behavior. ignoring peripheral stimuli and payins too much attention to detail and tend to process sequentially. In cot;trast the peripherally biased person has poor concentration, jumps from one thing to the other and is easily distracted by peripheral stimuh: a particular problem in a busy classroom environment. The types of problems commonly found in youngsters with specific learning difficulties will be presented, with the emphasis on a multisensory exercise programme specifically designed to improve these problems.
The quantitative evaluation of total internal reflection in keratoconus A. Hood, C. Veen, S. Vuugha~~, M. P. Edwmds, I. Simmons, G. A4isson Dept. of Birmingham
Ophthalmology and Midland
Leeds General Eye Hospital
In.firmary;
Purpose: The phenomenon of aplcal total internal reflection in the cone of keratoconic patients has been described previously. This study was designed to assess the quantifiable nature of this sign and its ability to diagnose and monitor keratoconus. Method: A sample of 30 patients with varying severity of keratoconus was compared with a series of sex and age matched normal controls and selected cases of spherically equivalent myopia. Each patient had a comprehensive cornea1 assessment including pachymetry, cornea1 topography, and standardised oblique slit lamp phoiography. The slit lamp photographs were digitally analysed to assess the area of total internal reflections. The severity of keratoconus was graded with a six stage ranking system based on the clinical appearance. Results: The area of total internal reflection was compared to the ranking system of clinical grading. For moderate and marked cones. the area of total internal reflection correlates well with both the clinical appearance and cornea1 topography. For mild and borderhne cases, the photographs show a less well defined area but this is nevertheless distinguishable from normals or spherically-matched equivalents. Conclusions: The area of total internal reflection visible in a keratoconic cornea correlates with the established techrliques of grading keratoconus. Imaging this phenomenon may form the basis of a quantitative clinical for this condition.
Tear production and elimination in normal eyes J. P. Ci-uig’~2, T. E. Hilditclz’,
A. Tomlinson’, A. Elliott’
‘Department of Vision Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow, UK “Optometry Department, Glasgow Eye Infirmary, West Glasgow Hospital University NHS Trust, Sandyford Place, Glasgow, UK 3Department of Nuclear Medicine, Western Infirmary, West Glasgow Hospital University NHS Trust, Glasgow, UK Tear fluid dynamics were and 19 females) with an scintigraphy. A 51 drop (Tc-‘“) was instilled into
investigated in 41 healthy subjects 1122males age range of 13 to 75 years, using gamma of saline containing a radioactive tracer the left conjunctival sac of each subject and
543
the path of the tracer was observed for 15 minutes using a gamma camera. Turnover of the tears was found to follow a blphaslc pattern. with an initial high flow rate (3.23 k 1.97 limin) corresponding to a reflex component, and a secondary slow rate (0.55kO.31 limin) corresponding to basal tear flow. There was found to be significant variation in tear drainage characteristics amongst the subjects. It was expected that, in normal subjects. passage of the tracer would not be inhibited as it passed from the conjunctival sac, through the canaliculi. into the lacrimal sac and into the naso-lacrimal duct. However, an apparent ‘obstruction‘ was observed at the level of the top of the naso-lacrimal duct in many of the subjects. This was found to clear spontaneously at some point during the measurement period in most individuals and, m those m whom spontaneous drainage did not occur. instillation of 151 of saline induced drainage. It appears that the valve of Krause, between the lacrimal sac and the naso-lacrimal duct, is responsible for retainmg fluid within the lacrimal sac in asynlptomatic subjects. The stimulus for drainage. in this instance; may be fluid volume within the lacrimal sac. This feature of lacrimal drainage was observed less frequently in older individuals which may be a result of age-induced laxity of the valve of Krause.
Eye drops and contact lenses-is
there a problem?
M. P. Rubinstein and J.E. Evans Department Nottingham,
of UK
Ophthalmology,
University
Hospital,
Preservatives used m topical ophthalmic preparations can result in a wide variety of toxicity or hypersensitivity reactions mvolving the anterior segment of the eye. The use of eyedrops in patients wearing contact lenses is therefore a contentious issue. In one of the major contemporary contact lens texts advice is both confusing and contradictory. The British National Formularly and Monthly Index of Medical Specialities advise discontinuation of contact lens wear (particularly soft lenses) when using preserved ophthalmic preparations. Unpreserved drops are suggested as a safer alternative. There appears to be less concern regarding wearers of gas permeable lenses. This issue is of particular importance in medical contact lens practice were therapeutic lenses are widely used, often for extended periods and often in conjunction with topical medical therapy. In these circumstances, unpreserved drops are frequently described. at considerably greater cost than their preserved equivalent. A review of the literature indicates that this perceived problem has been greatly overstated. This may stem from previous studies of contact lens interactions with care solutions. This poster will present a review of the subject.
Megalocornea: a case report Fevgal A. Ennis Manchester
Royal Eye Hospital,
Manchester,
UK
Megalocornea is a rare, usually bilateral, congenital condition of the cornea which results in an abnormally large cornea1 diameter ( > = 13 mm), often in association with a deep anterior chamber, significant refractive error and abnormal cornea1 curvature. A literature search through Medline revealed 55 papers referring to this condition, none of which mentioned contact lens fitting. Contact lens text-books make few references to the condition. those that do stating that scleral lens fitting is the only treatment modality. In this case report, we look at one patient. who we fitted with a high water content soft contact lens. We discuss our approach to fitting this patient. and the possibility of fitting other patients with the same condition.
The quantitative evaluation of total internal reflection in keratoconus A. Hood, C. Veen, S. Vuugha~~, M. P. Edwmds, I. Simmons, G. A4isson Dept. of Birmingham
Ophthalmology and Midland
Leeds General Eye Hospital
In.firmary;
Purpose: The phenomenon of aplcal total internal reflection in the cone of keratoconic patients has been described previously. This study was designed to assess the quantifiable nature of this sign and its ability to diagnose and monitor keratoconus. Method: A sample of 30 patients with varying severity of keratoconus was compared with a series of sex and age matched normal controls and selected cases of spherically equivalent myopia. Each patient had a comprehensive cornea1 assessment including pachymetry, cornea1 topography, and standardised oblique slit lamp phoiography. The slit lamp photographs were digitally analysed to assess the area of total internal reflections. The severity of keratoconus was graded with a six stage ranking system based on the clinical appearance. Results: The area of total internal reflection was compared to the ranking system of clinical grading. For moderate and marked cones. the area of total internal reflection correlates well with both the clinical appearance and cornea1 topography. For mild and borderhne cases, the photographs show a less well defined area but this is nevertheless distinguishable from normals or spherically-matched equivalents. Conclusions: The area of total internal reflection visible in a keratoconic cornea correlates with the established techrliques of grading keratoconus. Imaging this phenomenon may form the basis of a quantitative clinical for this condition.
Tear production and elimination in normal eyes J. P. Ci-uig’~2, T. E. Hilditclz’,
A. Tomlinson’, A. Elliott’
‘Department of Vision Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow, UK “Optometry Department, Glasgow Eye Infirmary, West Glasgow Hospital University NHS Trust, Sandyford Place, Glasgow, UK 3Department of Nuclear Medicine, Western Infirmary, West Glasgow Hospital University NHS Trust, Glasgow, UK Tear fluid dynamics were and 19 females) with an scintigraphy. A 51 drop (Tc-‘“) was instilled into
investigated in 41 healthy subjects 1122males age range of 13 to 75 years, using gamma of saline containing a radioactive tracer the left conjunctival sac of each subject and
543
the path of the tracer was observed for 15 minutes using a gamma camera. Turnover of the tears was found to follow a blphaslc pattern. with an initial high flow rate (3.23 k 1.97 limin) corresponding to a reflex component, and a secondary slow rate (0.55kO.31 limin) corresponding to basal tear flow. There was found to be significant variation in tear drainage characteristics amongst the subjects. It was expected that, in normal subjects. passage of the tracer would not be inhibited as it passed from the conjunctival sac, through the canaliculi. into the lacrimal sac and into the naso-lacrimal duct. However, an apparent ‘obstruction‘ was observed at the level of the top of the naso-lacrimal duct in many of the subjects. This was found to clear spontaneously at some point during the measurement period in most individuals and, m those m whom spontaneous drainage did not occur. instillation of 151 of saline induced drainage. It appears that the valve of Krause, between the lacrimal sac and the naso-lacrimal duct, is responsible for retainmg fluid within the lacrimal sac in asynlptomatic subjects. The stimulus for drainage. in this instance; may be fluid volume within the lacrimal sac. This feature of lacrimal drainage was observed less frequently in older individuals which may be a result of age-induced laxity of the valve of Krause.
Eye drops and contact lenses-is
there a problem?
M. P. Rubinstein and J.E. Evans Department Nottingham,
of UK
Ophthalmology,
University
Hospital,
Preservatives used m topical ophthalmic preparations can result in a wide variety of toxicity or hypersensitivity reactions mvolving the anterior segment of the eye. The use of eyedrops in patients wearing contact lenses is therefore a contentious issue. In one of the major contemporary contact lens texts advice is both confusing and contradictory. The British National Formularly and Monthly Index of Medical Specialities advise discontinuation of contact lens wear (particularly soft lenses) when using preserved ophthalmic preparations. Unpreserved drops are suggested as a safer alternative. There appears to be less concern regarding wearers of gas permeable lenses. This issue is of particular importance in medical contact lens practice were therapeutic lenses are widely used, often for extended periods and often in conjunction with topical medical therapy. In these circumstances, unpreserved drops are frequently described. at considerably greater cost than their preserved equivalent. A review of the literature indicates that this perceived problem has been greatly overstated. This may stem from previous studies of contact lens interactions with care solutions. This poster will present a review of the subject.
Megalocornea: a case report Fevgal A. Ennis Manchester
Royal Eye Hospital,
Manchester,
UK
Megalocornea is a rare, usually bilateral, congenital condition of the cornea which results in an abnormally large cornea1 diameter ( > = 13 mm), often in association with a deep anterior chamber, significant refractive error and abnormal cornea1 curvature. A literature search through Medline revealed 55 papers referring to this condition, none of which mentioned contact lens fitting. Contact lens text-books make few references to the condition. those that do stating that scleral lens fitting is the only treatment modality. In this case report, we look at one patient. who we fitted with a high water content soft contact lens. We discuss our approach to fitting this patient. and the possibility of fitting other patients with the same condition.