Abstract
Congenital aniridia is a rare genetic eye disorder often associated with PAX6 gene mutations, leading to complex ocular manifestations, including aniridia-associated keratopathy (AAK) and cataracts. The surgical management of cataracts in these patients is particularly challenging due to severe corneal opacities, which obscure key surgical steps such as capsulorhexis and phacoemulsification. This report presents two cases of congenital aniridia with severe AAK, in which chandelier retroillumination-assisted cataract surgery was employed. This technique, typically used in vitreous surgery, provided enhanced visualization of the lens through posterior segment illumination, facilitating successful cataract extraction and intraocular lens implantation. Both patients showed significant postoperative improvement in visual acuity. These cases demonstrate the feasibility and effectiveness of chandelier retroillumination-assisted cataract surgery in patients with congenital aniridia complicated by severe corneal opacity.
Plain language summary
Congenital aniridia is a rare genetic eye condition that often involves problems with a gene called PAX6. It affects the eyes in various ways, including causing cloudy corneas and cataracts, where the lens of the eye becomes cloudy. Performing cataract surgery on patients with this condition is tricky because the cloudy corneas make it hard for surgeons to see clearly during the operation.
This report discusses two patients with congenital aniridia who had severe clouding of their corneas. To help with their cataract surgery, the surgeons used a special technique called chandelier retroillumination, which shines light from behind the lens, making it easier for the surgeon to see and remove the cataracts. The surgery was successful for both patients, and they experienced noticeable improvements in their vision after the procedure. These cases show that using this special lighting technique can make cataract surgery safer and more effective for patients with severe corneal problems caused by congenital aniridia.
Keywords
Introduction
Congenital aniridia is a rare yet daunting condition with panocular manifestations. A great proportion of congenital aniridia is associated with a defect of the PAX6 gene, leading to profound developmental disorders of the eye that include but are not limited to hypoplasia of the fovea, anridia-associated keratopathy (AAK), glaucoma, and cataracts.
The surgical removal of cataracts and intraocular lens (IOL) implantation in these patients could present as a challenging task due to the corneal opacities caused by the aniridia-associated keratopathy. Key steps in cataract surgery such as capsulorhexis (CCC) and phacoemulsification are difficult due to the poor visibility of the crystalline lens and anterior capsule through the hazy cornea.
We describe two siblings from the same family suffering from congenital aniridia and cataracts associated with mutations in the PAX6. They successfully underwent cataract surgery using a chandelier illumination-system that is often used during vitreous surgery.
Case presentation
Case 1
A 45-year-old man with bilateral congenital aniridia related to mutation in the PAX6 gene presented with decreased visual acuity in the left eye. In his family, all three of the siblings (two female and one male) and the mother were diagnosed with PAX6 mutation.
He had cataract surgery in his right eye at the age of nine and subsequently suffered from aphakia and bullous keratopathy. He has undergone penetrating keratoplasty and amniotic membrane grafting in his right eye. He has glaucoma bilaterally and uses bimatoprost and sulfamethoxazole eyedrops regularly.
His best-corrected visual acuity was counting fingers at 30 cm in the right eye and 20/2000 in the left eye. On slit lamp exam, there was keratopathy affecting the central part of the cornea with neovascularization and involvement toward the central cornea, consistent with the findings of grade-3 AAK. 1 (Figure 1) There was congenital cataract with mostly nuclear sclerotic and central posterior subcapsular patterned opacity in his left eye.
Aniridia-associated keratopathy, Grade 3, in the left eye of a 45-year-old male patient who suffered from congenital aniridia related to PAX6 mutation prior to cataract surgery. Note the keratopathy affecting central part of the cornea with neovascularization.
Chandelier retroillumination-assisted phacoemulsification with IOL insertion was performed in his left eye. His best-corrected visual acuity improved from 20/2000 to 20/200 3 weeks after operation.
Case 2
A 46-year-old woman, who is the sister of the previous patient, suffered from blurred vision in both eyes since childhood due to congenital cataract related to PAX6 gene mutation. She was referred by another tertiary hospital in the region due to the difficulty of the cataract surgery given the severe corneal opacity. She had congenital aniridia and glaucoma bilaterally. Extracapsular cataract extraction (ECCE) with amniotic membrane grafting was performed a year ago in her left eye, and her best-corrected visual acuity in her left eye improved from hand motion at 30 cm to 20/1000 over the past year.
On exam, her best-corrected visual acuity was counting fingers at 30 cm in her right eye. Slit lamp examination showed a macula cornea with diffuse neovascularization, consistent with the findings of grade-4 AAK 1 (Figure 2). There was congenital cataract with cortical opacity and central posterior subcapsular patterned opacity of her lens in her right eye.
Aniridia-associated keratopathy, Grade 4, in the right eye of a 46-year-old female patient who suffered from congenital aniridia related to PAX6 mutation prior to cataract surgery. The entire cornea is affected with diffuse neovascularization with thick, irregular opacities.
Chandelier retroillumination-assisted phacoemulsification with IOL insertion was performed on her right eye. Her best-corrected visual acuity improved from counting fingers at 30 cm to 20/1000 3 weeks postoperation.
Surgical technique
Cataract surgery was initiated with microscope lights on. Retrobulbar anesthesia were induced with lidocaine 2%, and the conjunctiva was disinfected using povidone–iodine solution. A 25-gauge trochar system using Alcon Constellation Vitrectomy machine (Alcon Laboratories, Inc, Fort Worth, TX, USA) was placed at the infratemporal position. In fact, the trochar and the chandelier probe can be placed at pars plana of any direction as preferred by the operator. Then, Indocyanine green staining was used to stain the lens capsule.
Then, chandelier probe (25G for Alcon Constellation – Alcon Laboratories, Inc) was introduced into the trochar. Microscope lights are then turned off, and Chandelier light was turned on. This enabled clear visualization of the lens particles compared to having both chandelier lights and microscope lights on (Figure 3). Continuous curvilinear CCC, phacoemulsification, and IOL insertion were then performed under retroillumination.
Clear visualization of lens and anterior capsule intraoperatively with chandelier retroillumination in case 1, a 45-year-old man with Grade-3 aniridia-associated keratopathy.
Discussion
Congenital aniridia is a rare genetic eye disorder characterized by the partial or complete absence of the iris from birth. It is typically associated with mutations in the PAX6 gene, which are inherited in an autosomal dominant pattern with high penetrance. 1 PAX6 gene mutations result in premature termination codon, leading to conditions such as keratitis, iris hypoplasia, and congenital cataracts.
AAK is a PAX6 mutation-related condition found in up to 80% of congenital aniridia cases. 2 Multiple classification systems have been proposed, and AAK is commonly graded on a five-point scale. The five-point grading scale for AAK begins with Grade 0, where the limbal border is intact and healthy. In Grade 1, there is an initial breakdown of the limbal border, with conjunctival tissue encroaching within 1 mm of the limbus. Grade 2 shows further conjunctival ingrowth into the peripheral and paracentral cornea, sparing the central 2 mm, and is marked by vascular pannus and clouding. By Grade 3, the central cornea is affected, with vascularization and stromal keratopathy. Finally, Grade 4 represents the most severe stage, characterized by total corneal conjunctivalization, vascularization, and the transformation of the cornea into an opaque, irregular structure. 1 As the severity of AAK increases, it complicates cataract surgery due to reduced vision from stromal corneal opacity. 3
For lower-grade AAK, where only epithelial edema is present, glycerin-containing eye drops (5%) can be applied to reduce the swelling of the cornea, and corneal epithelium scraping could be attempted to improve visualization. However, in higher-grade AAK (Grades 3 and 4), these strategies are often inadequate due to the extent, irregularity, and depth of corneal opacity, rendering many cases inoperable with standard techniques. Alternative options such as ECCE have been used in these cases.
Chandelier retroillumination-assisted cataract surgery offers a promising solution for high-grade AAK patients with cataracts. This technique enhances visualization of the lens using a diffuse light source from the posterior segment, enabling cataract surgery with continuous curvilinear CCC and phacoemulsification even in patients with severe corneal opacities. The chandelier light source improves the red reflex, facilitating better visualization of the lens structure and capsule. To reduce reflection and glare from the hazy cornea, it is recommended that the microscope lights be turned off while the chandelier light is in use. Gently adjusting the chandelier light probe, using slight back-and-forth movements, to change the angle of the incident light can enhance visibility during the operation. Additionally, the self-retaining feature of the chandelier light allows the surgeon to perform the surgery bimanually, reducing the complexity of performing surgery in reduced visibility.
In fact, endoillumination has been previously reported in cataract surgeries where lens visualization is compromised by various conditions. In these cases, a fiberoptic light source was used to improve visualization by placing it externally on a less-scarred area of the cornea during CCC and in the anterior chamber during phacoemulsification. 4 Fiberoptic endoscope-assisted cataract surgery has been reported in a patient with congenital aniridia, and it has been successful with the aid of endoscopic visualization and intracameral illumination. 5 In 2007, Oshima et al invented the chandelier retroillumination-assisted cataract surgery by placing a 25-gauge chandelier endoilluminator into the vitreous cavity transconjunctivally through the pars plana for cataract surgery in patients with severe bullous keratopathy. 6 Similar techniques have then been reported to be used in cataract extraction in eyes with vitreous hemorrhage. 7
To our knowledge, this is the first report of the chandelier retroillumination technique used in cataract surgery with aniridia-associated keratopathy. It demonstrates the feasibility of this technique in not only diffuse corneal swelling, such as bullous keratopathy, but also in severe keratopathy with irregular opacities and neovascularization.
Conclusion
In conclusion, congenital aniridia presents significant challenges in cataract surgery due to the associated AAK and corneal opacity. Chandelier retroillumination-assisted cataract surgery emerges as a valuable technique for these patients, offering enhanced visualization of the lens through posterior segment illumination. The successful application of chandelier retroillumination in AAK cases highlights the feasibility of cataract surgery to patients with severe and irregular corneal opacities and neovascularization.
