In the first article in this series (click here) we looked at the full assessment and management of a patient presenting with symptoms of ocular discomfort likely associated with ocular surface compromise. After some intervention, the patient presented at the three-month review with improved signs including resolution of the inferior corneal staining, improved meibomian gland expressibility and quality, massively improved NIBUT and TBUT (see figure 1), improvement in tear volume measurements and consistently low conjunctival hyperaemia (figure 2). Table 1 summarises the clinical findings at this visit.
The patient reports good compliance and noticed an overall improvement in her symptoms (mirrored by slightly improved Speed index score). However, the symptoms of photosensivity during VDU work and the pain in and around her eye remain and are therefore still causing her quite some concern. The Speed index score, although improved, is still very high.
All pain and no stain – neuropathic dry eye
So what options do we have when the patient is still symptomatic despite our best efforts?
Despite a relatively normal clinical picture where the patient has healthy tear volume, healthy tear evaporation rate, healthy meibomian gland output, no visible inflammation, no hyperaemia, no corneal or conjunctival staining, no sign of infection or blepharitis the patient still suffers from severe symptoms.
Table 1: Slit lamp examination
This patient may to be suffering from neuropathic pain with associated neuropathic photosensitivity (photoallodynia) as a result of corneal hyper-algesia and hyper-evaporating tears, possibly with sub-clinical levels of corneal inflammation. More detailed questioning of the patients symptoms yielded a variety of descriptors of spontaneous pain including burning hot, sharp, needle-like pressure and aching. The pain was described as radiating from the eyes around the orbit. Comorbid headaches with associated hypersensitivity to sound (hyperacusis) were also mentioned after prolonged questioning all of which have been associated with neuropathic forms of dry eye like symptoms.
Figure 1: Improvement in tear break up characteristics
To investigate these symptoms and the likelihood of neuropathic dry eye we attempted to simulate the patients work environment at a VDU in our practice, this induced the patient’s symptoms within 30 minutes. Topical corneal anaesthesia via Proxymetacaine hydrochloride 0.5% eye drops also failed to fully suppress the patient’s symptoms. Cycloplegia with 1% Cyclopentolate had no beneficial effect on the patient’s symptoms. Diagnostic mini-scleral lenses were placed on the eye and had an instant impact on the patient’s symptoms. The patient was therefore offered a scleral lens fitting appointment.
Figure 2: Hyperaemia assessment
Why scleral contact lenses?
Scleral and semi-scleral (mini-scleral) contact lenses are experiencing a huge resurgence in popularity in recent years. The therapeutic application of scleral lenses in conditions such as post-graft, post-refractive surgery, keratoconus and an array of corneal surface diseases has been well documented.1-6 The fitting process was previously more of an art than a science and was somewhat of a cumbersome time-consuming process lacking in precision.7 However, with the improvements in anterior eye imaging via high definition wide field anterior OCT (see figure 3 - above) and enhanced corneal topography combined with advances in lens design and materials the process is now much simpler, more attainable and therefore more successful.
Scleral contact lenses have a unique capability of completely blocking corneal surface evaporation, maintaining an optimal hydrating environment and protecting the external corneal surface from the friction of blinking; all of which may be beneficial in reducing the symptoms of corneal evaporative hyper-algesia.8 The lens creates an expanded pre-corneal tear film or ‘liquid bandage’ that modifies the environment at the corneal surface. It is plausible that the lens reduces hyperosmolarity, desiccation and shear forces from the lids and thus reduces local insult, pathologic neurogenic and immunologic responses at the ocular surface. This modification of responses may account for the mitigation of patient symptoms and hopefully an improvement in quality of life.9,10
Scleral lens fitting
The exact fitting process will vary depending on the lens design and manufacturer. A simplified fitting process for a normal eye involves measuring the sagittal depth with a 10mm chord (using anterior OCT or enhanced corneal topography) and simply adding approximately 2,400µm to this figure to produce the lens of first fit. Assessment of the central corneal clearance zone (CCZ), peripheral corneal clearance zone (PCCZ), limbal clearance zone (LCZ), scleral landing zone (SLZ) and over-refraction can then be completed to achieve an optimal fit. Slit-lamp examination combined with anterior OCT can be utilised to assess and improve the lens fit (see figures 4 to 6).
Figure 4: Anterior OCT showing lens and pre-corneal tear layer
10mm chord sagittal measurement
R: 1901µm
L: 1809µm
First fit trial lens used
R: Sag: 4300µm, Diameter 16.5mm, Power -3.00D Material: HDS 100 Design ICD
L: Sag 4200µm, Diameter 16.5mm, Power -3.00D Material: HDS 100 Design ICD
Assessment of fit
Initial CCZ approximately 360µm on insertion. This reduced to approximately 240µm (see figure 4). Mildly tight SLZ, minus 1 modification SLZ which improved fit (see figure 5). Over-refraction completed and final lens ordered.
Figure 5: OCT image of lens – picture on left reveals tight SLZ. Image on the right shows minus 1 modification to SLZ
Final lens
R: 4.30 / 16.50 / -14.00 ICD Single Vision Lens, Paragon HDS100 Material
L: 4.20 / 16.50 / -10.50 ICD Single Vision Lens, Paragon HDS100 Material
Care system
Hydrogen peroxide clean.
Patient outcome
The patient has been wearing scleral lenses for six months and reports a significant improvement in her symptoms. Her left eye is completely devoid of any issues; her right eye still causes occasional irritation at work but now at an acceptable and tolerable level. Her visual acuity is stable R: 6/4 (N4), L: 6/4 (N4). The fit of the lenses remains optimal and the CCZ reduced to approximately 190µm after prolonged wear. Her Speed index score is now under 10 and at a level considered to be normal.
Figure 6: Slit lamp assessment and fluorescein fit of final lens in situ
Occasional ‘mid-day fog’ is the only minor annoyance reported by the patient. This requires removal of the lenses and replacement of the saline to alleviate the issue; however, this is only necessary a few days per month. Mid-day fog is a relatively common finding in scleral lens fitting. At present the causative mechanisms are not fully understood. It is seen as a mild inconvenience and unlikely to cause drop-out of lens wear.
Discussion
Utilising the holistic approach, albeit initially time consuming, in patients of this nature is hugely beneficial. Spending the additional time with the patient to ensure you fully understand the severity of their symptoms and can sympathise and even empathise with them is important in their management. Often patients with symptoms of this sort will have been dismissed or ignored by numerous ECPs before attending your practice, this can further fuel their feelings of isolation and depression, which in turn are a potential driver of their ocular symptoms. Positively and delicately explaining that the clinical picture looks good despite the severity of their symptoms and further explaining that you have dealt with other patients with similar experiences will play be important in successful management of these difficult cases.11 As primary care givers ECPs are well placed to help diagnose patients with depression-related symptoms and offer appropriate referral to care pathways via the patient’s GP.
Craig McArthur is involved in a dedicated anterior eye clinic service at Peter Ivins Eyecare practice in Glasgow.
References
1 Rosenthal P, Cotter J, Baum J. Treatment of persistent corneal epithelial defect with extended wear of a fluid-ventilated gas-permeable scleral contact lens. Am J Ophthalmol 2000; 130:33-41.
2 Kok JH, Visser R. Treatment of ocular surface disorders and dry eyes with high gas-permeable scleral lenses. Cornea 1992; 11:518-522.
3 Pullum KW, Whiting MA, Buckley RJ. Scleral contact lens: The expanding role. Cornea 2005;24:269 –277.
4 Schein OD, Rosenthal P, Ducharme C. A gas-permeable scleral contact lens for visual rehabilitation. Am J Ophthalmol 1990; 109: 318-322.
5 Segal O, Barkana Y, Hourovitz D, et al. Scleral contact lenses may help where other modalities fail. Cornea 2003; 22:308-310.
6 Foss AJ, Trodd TC, Dart JK. Current indications for scleral contact lenses. CLAO J 1994; 20:115-118.
7 Pullum K. The unique role of scleral lenses in contact lens practice. Cont Lens Anterior Eye 1999; 22(suppl):S26 –S34.
8 Gemoules G. A Novel Method of Fitting Scleral Lenses Using High Resolution Optical Coherence Tomography. Eye & Contact Lens 34(2): 80-83, 2008.
9 Rosenthal P et al. Corneal Pain Without Stain: Is it Real? The Ocular Surface. Jan 2009: Vol 7, No 1
10 Jacobs, DS. Perry Rosenthal P. Boston Scleral Lens Prosthetic Device for Treatment of Severe Dry Eye in Chronic Graft-Versus-Host Disease. Cornea 2007; 26:1195-1199
11 Nichols KK, Nichols JJ, Mitchell GL. The lack of association between signs and symptoms in patients with dry eye disease. Cornea. 2004; 23:762-770.