The case report describes the fitting of a spherical scleral lens to a set of relatively straight-forward keratoconic eyes.
Our patient, a 20 year old male, with two brothers with keratoconus, presented to our practice as over the past 6 months he had noticed that his left eye had become blurry. He had not been for an eye exam before.
Unaided vision was R 6/12, L 6/30 improving with refraction to R +1.00/-0.75 x 95 (6/7.5), L +0.75/-1.50 x 100 (6/20).
Topography showed keratoconus in both eyes but worse in the left.
CAPTION:Medmont topography maps showing the slighly decentered keratoconic ectasia.
There was faint corneal striae at the apex of the cone in the left eye.
CAPTION: Photo of the left eye showing faint corneal striae at the apex of the cone.
Corneal thicknesses measured with OCT at the apex of the cone was R 540um and L 470um.
As this patient played soccer at a competitive level he was interested in getting fitted with the same type of scleral lenses as his brothers, as they prefered the comfort and vision provided by sclerals compared to their previous smaller rigid gas permeable (RGP) lenses.
The patient had a horizontal visible iris diameter (HVID) of 11.6mm so we went straight to the 17.5mm diameter trial set of the EyeSpace Scleral lens in order to provide sufficient clearance over the limbus.
The trial lenses used were: R Lens 14 / 3900 microns / 8.2 / 17.5 / Standard SLZ / Plano L Lens 17 / 4200 microns / 7.9 / 17.5 / Standard SLZ / -1.50
These SAG@15mm of these trial lenses were decided based on the recommendations in the EyeSpace Scleral guide:
- Normal shaped and refractive surgery - 3900 micron
- Keratoconus and Pellucid Marginal Degeneration - 4200 microns
The method of taking the sag of the flat meridian at 10mm (R 1700 microns, L 1900 microns) and adding 2150 microns (R = 3850 microns, L = 4050 microns) also gave similar starting points for a trial fit.
After the lenses were given time to settle in the eyes both lenses showed even alignment of the SLZ in each meridian with no impingement of the conjunctival vessels. The following photo shows the fit of the left diagnostic lens inferiorly.
CAPTION: Photo showing the fit of the standard SLZ of the EyeSpace diagnostic sclereal lens at the 6 o'clock position of the left eye
Centrally there was apical clearance of both lenses although the right lens was sitting 75 microns from the cornea - a little too close as shown by the following OCTs.
The left lens had a little too much clearance at 250 microns. Both lenses had back optic zone radii (BOZR) that were a little flat - the tear layer thickness increased more peripherally. This was best shown in the the left eye’s OCT.
For the best alignment these BOZR should decrease by 0.2-0.3mm.
CAPTION:OCT of the right EyeSpace scleral diagnostic lens on eye, showing a post lens tear thickness (PLTT) of 75 microns.
CAPTION:OCT of the left EyeSpace scleral diagnostic lens on eye, showing a post lens tear thickness (PLTT) of 250 microns.
Over-refraction was R +1.00DS (6/7.5+2), L + 1.75DS (6/7.5). No flex was found in the over-topography.
Combining these findings gave us the parameters for our initial ordered lenses: R 7.9 / 4000 microns (100um more than the trial) / 17.5 / Standard SLZ / -0.50DS, L 7.7/ 4150 microns (50um less than the trial) / 17.5 / Standard SLZ / -0.75DS. (Note the power of the lenses was calculated with the SAM/FAP rule when steepening the BOZR 0.3mm and 0.2mm in the R and L lens respectively).
At delivery the lenses were providing good vision and the fit of the lens was reasonable. The patient was taught how to insert (with Lens Plus saline solution), remove and clean (Menicare plus) the lenses and asked to return in 2 weeks.
The patient returned 2 weeks later wearing the lenses. He reported good vision and reasonable comfort although after a few hours a haze developed which affected his sight. He was also more aware of the lens in the left eye.
With the lenses the patient was seeing R 6/7.5+2, L 6/7.5, B 6/5-. Over-refraction gave a small ATR cylinder in the right eye (+0.50/-0.75 x 90) and the left eye had a plano over-refraction.
Topography showed no real evidence of flex to match the right eye’s ROL as seen by the following topographies (the slight WTR flex seen in the right eye should produce cylinder in the overrefraction axis 180 degrees). You can see the slight temporal displacement of the lenses, a finding not uncommon in scleral lenses.
CAPTION:Topography maps of the EyeSpace scleral lenses one eye showing a slight with-the-rule astigmatism on the front surface of the right lens. Both lenses are slightly decentered on the horizontal meridian.
The alignment of the right scleral landing zone (SLZ) seemed pretty good under the slit lamp and OCT.
CAPTION:Photo showing the well aligned scleral landing zone in the principal meridians of the right eye.
CAPTION:OCT images confirms a well aligned SLZ in the vertical and horizontal meridians of the right eye
However slit lamp and OCT images demonstrated the left lens was one step too steep in the SLZ. We see this as the ‘toe’ of the lens compressing the conjunctival tissue more than the ‘heel’ as shown:
CAPTION:Slit lamp images showing the slightly tight SLZ which is noticable as mild conjunctival blanching at the lens edge.
CAPTION:The OCT images confirms that the SLZ in the principal meridians are slightly tight. The tight SLZ can be seen by the mild 'toe' down compression of conunctival tissue at lens edge. Also note some debris in the inferior post lens tear reservoir as seen in the top OCT image.
Central clearance was good in both eyes with the left having slightly more clearance of 211 microns versus 174 microns in the right eye.
The photo shows how practitioners can sometimes underestimate the clearance using the slit-lamp, especially when clearance is below 200 microns.
CAPTION:Slit lamp images showing the PLTT of both the left and right EyeSpace scleral lenses. Accurately judeging the PLTT with the slit lamp becomes challenging when the PLTT is less than 200 microns. Good practice is to use the scleral lens thickness as a guide and aim to get the PLTT about half the thickness of the scleral lens.
The OCT also shows that the whole cornea including the limbus is being vaulted in all meridians.
CAPTION: OCT images shows good lens clearance in both eyes. It is important that a scleral lens should never touch the cornea.
Slitlamp examination further showed a slight build-up of debris in the post-lens tear film. This is not uncommon early on as a patient adapts to wearing a scleral lens for the first time, especially in atopic keratoconics.
On questioning, the patient had also been cleaning his lens incorrectly with saline rather than his recommended cleaning solution. This lead to poor surface quality on the lens as seen after the instillation of NaFl with the lens in the eye. His cornea was normal and showed no staining or oedema after lens removal.
We decided there were no changes required on the right lens, but the left could do with 50 microns less clearance and a flat, rather than standard SLZ, to improve comfort. Less clearance in the left lens would mean there was a decreased thickness of tears to look through if any debris accumulated. This would help with the visual haze over time due to mucous.
The lens parameters became: L 7.7/ 4100 microns (50um less than the first lens) / 17.5 / Flat SLZ / -0.75DS.
The patient was also given Zaditen drops to use BID and asked to return after a week of wearing the left lens.
One month aftercare
The patient returned 2 weeks after wearing his new left lens and was very happy. The haze had greatly improved and he now maintained clear vision throughout the day. Comfort in the left eye had also improved, now equivalent to the right eye.
The new left lens is shown below with an ideal level of central clearance seen below on OCT and slit-lamp.
CAPTION:OCT of the left EyeSpace scleral lens on eye, showing a post lens tear thickness (PLTT) of 146 microns. Notice that the PLTT is not centrally measured as the apex of the cone, and closest point to the lens, is slighly decentred.
CAPTION:The slit lamp images shows good lens alignment. Notice that the PLTT is about half of the scleral lens thickness.
OCT of the SLZ also shows better alignment, which is contributing to the patient’s improved comfort.
CAPTION: OCT of the new left EyeSpace scleral lens shows a well aligned SLZ in the pricipal meridians. A proper aligned SLZ will eliminate any blanching and improve lens comfort.
As the lens fit seemed optimal and the patient was seeing well he was asked to return for routine follow-up in 1 month time to check the eye’s health and his adherence to lens care regime. He reported that he had tried using his scleral lenses in a few soccer trainings during the previous week and they were stable and improved his vision, especially under lights. He was looking forward to giving them a run during a game in the weekend coming!
At first presentation, this patient was referred to a corneal specialist for consideration for corneal cross-linking (CXL) given that the change in vision that prompted his appointment suggested keratoconus progression.
Some patients will be reluctant to invest in a cross-linking procedure as some ophthalmologists will require them to be out of their lenses for a couple of weeks prior to and following the procedure. Given the often debilitating effect on their life when out of their lenses this request is unrealistic in most cases.
A well-fitted scleral lens should never be in contact with the area of the cornea that is manipulated during CXL and should not have an effect on the topography or corneal integrity. We discussed this with our local corneal specialist and as a result patients are now permitted to wear their sclerals up until the day of their surgery, making the decision to have a potentially sight-saving procedure done far more realistic. This is another advantage to fitting keratoconics with scleral lenses over corneal RGPs.
This case demonstrates how keratoconus can be managed with EyeSpace Scleral lenses in the first instance to give stable and comfortable vision to a young active patient.
Although most cases will demonstrate a need for a toric periphery scleral lens to decrease lens flex, and in some cases a front surface toric to correct unwanted internal astigmatism, simple cases like this can be appropriately fitted with rotationally symmetric scleral lenses to give great results for the patient.