Evaluation of Anterior Lenticonus in Alport Syndrome Using Tracey Wavefront Aberrometry and Transmission Electron Microscopy

Introduction

Alport syndrome is an inherited disorder characterized by progressive nephropathy with basement membrane structural defects, sensorineural hearing loss, and frequent ocular abnormalities. It is characterized by X-linked, autosomal recessive or autosomal dominant inheritance, but 85% of cases have been reported to be associated with X-linked inheritance. The responsible mutations affect the COL4A5 gene for the α5 chain of type IV collagen, which is the major constituent of the basement membrane in the glomerulus, cochlea, retina, lens capsule, and cornea.¹

The reported incidence of ocular manifestations in Alport syndrome ranges from 11% to 92%.² Ocular manifestations are characterized by retinal flecks,³ anterior lenticonus,⁴ cataracts,⁵ corneal arcus,⁶ recurrent corneal epithelial erosion,⁷ and corneal dystrophies.⁸ Arnott et al.⁹ reported that anterior lenticonus is a specific sign for Alport syndrome. In some reports, more than 90% of cases of anterior lenticonus were associated with Alport syndrome.¹⁰ Anterior lenticonus may lead to progressive visual loss as a result of either irregular astigmatism or cataract formation. Crystalline lens phacoemulsification is often indicated in patients with Alport syndrome because of progressively decreased visual acuity. ¹¹

The diagnosis of anterior lenticonus is based on findings on slit-lamp biomicroscopy. The findings of abnormal lens contour on slit-lamp examination and normal corneal topography strongly suggest lenticular irregular astigmatism. A scissors reflex is often found in both eyes, resulting in the oil droplet appearance that is associated with anterior lenticonus. However, these methods provide no quantitative analysis for lenticular irregular astigmatism. Recently, it became possible to measure the lenticular portion of an irregular astigmatism indirectly by subtracting the corneal irregular astigmatism measured with corneal topography from the irregular astigmatism of the entire eye measured with wavefront analysis. ^12,13

The current study evaluated irregular astigmatism of the lens and entire eye of a patient with Alport syndrome using a Tracey wavefront aberrometer (Tracey Technologies, Houston, TX) and described the results of histologic evaluation of the lens capsules acquired intraoperatively using transmission electron microscopy to clarify the underlying pathology.

Patients and Methods

A 25-year-old man was diagnosed as having Alport syndrome. He had a history of progressive bilateral decreased visual acuity beginning 5 years before he was seen in our clinic. He also had a history...