The assessment, diagnosis, treatment and monitoring of dry eye disease has evolved into one of the key services offered by modern eye care practices. What was once all-too-often dismissed as a nuisance feature of growing old, one managed by throwing hypromellose at the eyes of our patients. Advances in both instrumentation and the ongoing development of ever more specific treatment options means that, not only is it possible to distinguish different presentations of dry eye disease, it is also possible to address the various different components of the ongoing condition and offered a tailored and customised solution to each patient to relive their symptoms. Importantly, this tailored approach can be monitored and adapted over time as the disease profile evolves.
Basic Approach
In order to offer this service, the minimum requirement for assessment of the tears and ocular surface, as for example is required for qualification as an entry level optometrist at present, would require the following:
- History and symptoms
- Slit-lamp examination (white light); to assess the lid margins, palpebral (after eversion) and ocular surface for irregularity and the tears for debris, fringe patterns and bubbling
- Tear prism height; ideally central, nasal and temporal
- Slit-lamp examination (blue light); to assess staining (corneal and conjunctival) and fluorescein break-up time
All of this is possible in any practice with standard kit. Where there is facility to project an image onto the tear film (such as keratometry mires or use of a grid light-mounting), non-invasive tear break-up time is possible. Also, use of lissamine green dye helps to visualise lid-wiper epitheliopathy.
Improved Approach
Dry eye management is greatly improved by investment in an anterior imaging system. Slit-lamp photography greatly improves both the accuracy of testing and also makes things much easier to explain to patients, so improving compliance with management strategies. It also allows accurate monitoring of changes over time, to show how treatment is working or detect any disease progression. The better your slit-lamp and imaging system, the better the results.
There have also been advances in software that make it possible to measure changes viewed on the ocular surface more accurately and then generate a report summary. This capability might be incorporated into a dedicated instrument, such as with the Topcon Myah or the Visionix 120, or might be used as an adaptation to existing slit-lamp units, such as the Essilor IDRA. Other developments in software allow images to be enhanced and analysed by quantifying specific features, such as by automatically grading signs such as staining and hyperaemia; the AOS software is a good example of this.
So, it was just a matter of time for a slit-lamp with incorporated dry eye image capture and analysis software hit the market. Introducing the SK Med SL-7DS LED digital slit lamp with DS-1 Dry Eye Analyser (UK distributor, BIB Ophthalmic Instruments). I was able to try out the new system in clinic at the end of last year.
SK Med SL-7DS Slit Lamp
The BIB Dry Eye Analyser comprises a high specification slit-lamp incorporating image capture linked to a PC with dedicated software for the undertaking of a full battery of dry eye assessment tests and the generation of a summary report for dry eye disease management (figure 1).
Figure 1, 2 & 3 (left-right): The SK Med SL-7DS LED digital slit lamp with DS-1 Dry Eye Analyser (UK distributor, BIB Ophthalmic Instruments); The Canon Digital SLR 1500D camera, capable of 24.1 Megapixels for JPEG and video capture, is fully integrated with the slit lamp; Camera operation is possible via a single Bluetooth linked joystick button allowing image capture while viewing the patient. Note the two rheostats; one for main illumination, the other for the back lighter
The SK Med SL-7DS is a high end instrument capable of all one would wish from a slit-lamp. I confess that, on first seeing the Canon camera poised atop of the unit (figure 2), my heart sank with memories of having to press multiple buttons, requiring movement away from the eyepieces of the slit lamp, to achieve the best capture. Such concerns were soon assuaged as I realised that camera operation was fully integrated allowing capture via a Bluetooth linked joystick button on the main slit lamp while still viewing the patient (figure 3).
As well as full illumination control of both the slit lamp light and the back lighter, via separate rheostat controls, there is also an integrated aperture stop control (figure 4) allowing even greater control of the brightness and contrast of the captured image (figure 5).
Figure 4 & 5 (left-right): Aperture stop control button, seen to the right of the magnification control; Separate controllable light source for slit lamp and back light
A key adaptation of the slit lamp is to allow for specific tear and ocular surface analysis imaging. The viewing unit, as seen by the patient, has an LED-lit housing (figure 6a) capable of full annular LED illumination (figure 6b) or sectoral illumination (figure 6c), depending on the image function required. There are two magnetised mountings (figure 6d), which are easily positioned onto the unit: a Placido disc attachment (figure 6e) for topographical analysis and an annular diffuser attachment (figure 6f) for interferometry and general viewing, including viewing with infrared for meibography or with blue light for stain analysis (figure 6g).
Table 1 summarises some key features of the SK Med SL-7DS slit lamp:
Figure 6: Adaptations for dry eye analysis. (a) Viewing unit from the patient perspective. (b) Annular and (c) sectoral illumination. (d) Viewing adaptors. (e) Placido adaptor in situ. (f) Diffuse adaptor in situ. (g) Blue light via diffuse adaptor
Anterior Photography
As you would expect from such a high-resolution integrated camera, the quality of anterior photos and videos is excellent (figure 7). Each image is stored with the patient file on the connected computer and is easily displayed in gallery form for the benefit of both patient and practitioner.
Figure 7: Anterior photography. (a) Inferior lid margin showing inspissated meibomian gland opening and localised pigmentation. (b) Superior meibomian gland openings. (c) Upper lid view of cosmetic wearer showing 0.5mm papilloma. (d) Grade 1 anterior blepharitis on lower lid. (e) Temporal bulbar conjunctival hyperaemia and pigmentation. (f) Gallery display of images for patient demonstration
Dry Eye Analysis
Dry eye analysis is undertaken via the computer. Once patient details are input, they are then selected and captured images are automatically input into their file (figure 8a). Clicking the dry eye analysis icon in the top left corner takes you to a screen that allows you to run through each dry eye test in sequence, or to select any specific test as required (figure 8b).
Figure 8: Computer display. (a) Main screen with images/videos for individual patients displayed. (b) Dry eye analysis screen showing the various tests along the top (marked A; in this case, meibography is being undertaken) and the ‘analysis’ button (marked B)
Before image analysis, the system allows the recording of a dry eye questionnaire, such as the OSDI or the SPEED (figure 9). Results are stored with the patient and can be included in a final report.
Working through the full sequence, once you become adept at changing the adaptor heads and remembering how to centre and focus the light for best results, takes around seven to eight minutes.
Tear meniscus height
On screen callipers allows either manual or automatic measurement of the tear meniscus in up to five positions (figure 10). The automated accuracy is only as accurate as the clarity of the meniscus on the image, so care must be taken getting the best illumination.
Non-invasive tear break-up time
The ability to measure break-up time without fluorescein accurately and with indication of the localised break-up pattern is an important feature of dry eye analysis. The Placido rings are centred on the pupil and, after the patient’s forced blink, the video is started, which then captured the gradual degradation of the ring images (figure 11). Accurate centration and widened palpebral apertures are essential, but the results seemed both accurate and repeatable.
Lipid layer interferometry
The use of the diffuse adaptor allows the viewing of the polarise colour fringes from the lipid layer, essential for assessing the likelihood of evaporative tear problems for patients with MGD or with symptoms when exposed to environmental conditions likely to cause dryness (figure 12). A with all the tests, once the best images are selected, the software will automatically analyse the results by clicking the ‘A’ button (figure 8).
Hyperaemia
Images of vascular structures may be enhanced (figure 13) and the level of ‘redness’ automatically graded.
Meibography
The imaging of the meibomian glands with infrared light, to check for tortuosity, thickening or drop-out, is increasingly important for assessing MGD and evaluating the benefit of interventions. Images are easily enhanced and automatically graded (figure 14).
Fluorescein
Image capture under blue light and with fluorescein instillation was easy, and images taken can be enhanced to maximise the view of staining or can be automatically graded through a sectional grating view (figure 15).
Patient Reports
Key to success in any management plan is the complete buy in from a patient to ensure they comply fully with instruction and understand the likely timescale and changes hoped for. The Dry Eye Analyser offers a range of options to assist this, with either individual reports for specific signs or a summary overall report. Such reports are also important to demonstrate improvements over time.
Conclusion
Where this system clearly wins is its combination of dedicated dry eye analysis software with a high-end slit-lamp and imaging system. Anyone ready to buy a new slit lamp or anterior imaging system should take a look.
- For further information contact BIB on 01438 740823.