lenses were first described in medical literature in the late 19th century. Adolf Fick proposed his use of glass blown shells in 1888. Eugene Kalt then used these vesicles to improve the vision of a patient with keratoconus. August Mueller later described his attempts to correct his own myopia with these glass lenses. Although these lenses did improve vision, they were not widely used due to challenges with manufac-turing and wearing. 7 In the 1940’ s, polymethylmethacylate( PMMA), a new lens material was developed by workers such as Feinbloom, Obrig and Gyoffry. 8 The lenses were molded based on an impression of the cornea, which facilitated manufacture. However, the poor reproducibility and permeability of these lenses limited their distribu-tion. In the mid-1900’ s, corneal contact lenses were introduced. 7 They were also originally made of PMMA but were smaller than scleral lenses, which made oxygen and tear exchange as well as fitting easier. With the later development of rigid gas permeable( RGP) materials, as first described by Ezekiel in 1983, oxygen was readily able to penetrate through the lenses themselves and further reduced complications related to contact lens wear. 7 These, in addition to soft lenses, stopped the further development of LDRGP fitting. 7,8
A few years ago, only few specialized practitioners were fitting LDRGP lenses. Since then, there has been a slow but steady increase in the demand for these lenses as a solution for more challenging cases. 8 LDRGP designs have become more and more popular and are available in several options: a corneo-scleral lens( 12.5 mm to 15 mm), supported partly by the cornea and partly by the sclera; a mini-scleral lens( 15 mm to 18 mm) vaulting the cornea, supported by the fluid layer and the conjunctiva; or a larger scleral lens( 18 mm to 25 mm) with the same fitting philosophy as the mini-scleral lens but with different parameters. 8
This case describes the use of mini-scleral lens technology in restoring vision and protecting the ocular surface in a patient suffering from Möbius syndrome.
Background
In the fall of 2010, an 8-year-old Caucasian female was referred for a contact lens evaluation by an ophthalmologist for the treatment of neurotrophic keratopathy. She had been diagnosed with encephalopathy, likely of prenatal origin, resulting in a forme frustre of Möbius-like syndrome. Systemic manifestations of her condition included epilepsy, recurrent episodes of rigidity( especially when tired), agitated sleep, decreased pain sensation resulting in frequent injuries, complete deafness of the right ear, absent gag reflex, nasal congestion and trouble walking due to lower limb deformities. Her ocular history was remarkable for a trigeminal nerve( V) palsy, leading to loss of corneal sensitivity, as well as abdu-cens nerve( VI) palsy. She also presented with lagophthalmia secondary to facial nerve( VII) malfunction. Combined, these anomalies triggered the develop-ment of neurotrophic corneas, worse in the right eye than the left. Consequently, she required ocular lubricants several times a day to preserve both the ocular surface and her vision. She was seen in the con-tact lens clinic in order to be fitted in RGP contact lenses to maintain constant lubrication of her cornea. The idea was to protect the ocular surface from eventual abrasions as well as improve her vision.
Clinical findings
Initial clinical findings are summa-rized in Table II.
Corneal topography was mea-sured using a Medmont E-300. An axial power map displaying the paraxial power of the surface in diopters with respect to the kerato-scope axis was selected( Figure 1). The color scale on the left repre-sents the range of powers that can be found on the cornea, with dark red being the highest and dark blue being the lowest. 10 The E values at the top left, formerly what Med-mont called Shape Factor, indicate the elliptical shape index for the Steep( in red) and Flat( in blue) axes of the cornea. The Sim-K values at the bottom left indicate the values for the Steep( in red) and Flat( in blue) axes of the cornea. 9 The patient’ s topography showed many irregular zones of the corneal surfaces in both eyes, but mostly in the right eye( Figure 1). There were large and rapid changes in power and shape. The interruptions in the image rep-resent the device’ s inability to cap-ture that part of the corneal surface
C a n a d i a n J o u r n a l o f O p t o m e t r y | R e v u e c a n a d i e n n e d’ o p t o m é t r i e Vol 75 | No 2 2013 43