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 In the mid-1900 ’ s , corneal contact lenses were introduced . 7 They were also originally made of PMMA but were smaller than scleral lenses , which made oxygen and tear exchange as well as fitting easier .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