Successful visual rehabilitation in a case of anterior megalophthalmos.

We report a case of 40-year-old female who presented with diminution of vision in both eyes. Ocular evaluation showed presence of bilateral megalocornea with deep anterior chamber, iridodonesis, cataract, and anterior embryotoxon. She was diagnosed with bilateral anterior megalophthalmos. She underwent an uneventful cataract extraction with standard posterior chamber intraocular lens implantation of overall large diameter in the left eye. Zonular dialysis was not evident intraoperatively despite the presence of iridodonesis. Postoperatively the intraocular lens was well centered throughout follow up. This case report reviews this rare disorder and highlights successful visual rehabilitation.

INTRODUCTION

Megalocornea is a nonprogressive bilateral congenital enlargement of the anterior segment in the absence of raised intraocular pressure.1 It can occur in three forms—simple megalocornea unassociated with other ocular abnormalities; anterior megalophthalmos with megalocornea; and iris and angle abnormalities as well as buphthalmos in infantile glaucoma.

Anterior megalophthalmos is a rare hereditary disorder characterized by presence of megalocornea (horizontal corneal diameter more than 13 mm) in association with enlarged lens iris diaphragm and ciliary ring.2 Secondary complications include presence of iridodonesis, miosis, atrophy of iris stroma, and cataractous lens. Marfan's syndrome, Apert syndrome, Down syndrome, and mucolipidosis type 2 are some systemic associations seen with this condition.

Premature development of cataract is the most common cause for visual impairment in this condition. Cataract extraction in these patients is prone to complications due to presence of weak zonules and ciliary ring enlargement. One of the major challenges in the management of cataract is placing the correct size of intraocular lens (IOL) in the capsular bag to prevent IOL decentration. Possible options would include use of a large custom-made posterior chamber (PC) IOL or use of anterior chamber iris sutured IOL.34 This case report describes the use of standard posterior chamber IOL of larger diameter in the management of cataract in anterior megalophthalmos.

CASE REPORT

A 40-year-old healthy woman presented with gradual progressive painless diminution of vision in both eyes for 1 year duration. There was no relevant family history. On examination, her best corrected visual acuity (BCVA) OD was 6/18 and light perception with projection, OS. Anterior segment examination in both eyes revealed presence of megalocornea [Figure 1] and clear cornea with mild pigment on endothelium. Anterior chamber were deep bilaterally. Iridodonesis with ectropion uveae was also present. The pupil of either eye could not be fully dilated by pharmacological mydriasis. There was grade I nuclear sclerosis (by Lens Opacity Classification System II) OD and total cortical cataract with phacodonesis OS. Biometric measurements were as shown in Table 1. Gonioscopy showed open angles with broad pigmented trabecular meshwork and anterior embryotoxon [Figure 2]. Intraocular pressure by applanation was 16 mmHg OD and 14 mmHg OS. The central corneal thickness (CCT) using ultrasound pachymetry was 0.445 mm OD and 0.465 mm OS. Fundus examination of the right eye was normal. B scan of the left eye was normal. Vitreous index was 63% OD and 66% OS. Based on the above findings, the patient was diagnosed with anterior megalophthalmos. Systemic examination was normal.

Figure 1

Horizontal corneal diameter measured by using a Castroviejo calipers

Table 1

Biometric data of a patient with anterior megalophthalmos

Figure 2

Gonioscopy photograph showing presence of broad pigmented portion of trabecular meshwork

Manual small incision cataract surgery with use of capsular tension ring (CTR) with peribulbar block was planned for the left eye. IOL power was calculated with the SRK II formula. Preoperatively we were not able to assess the capsular bag diameter. Cataract surgery was uneventful in the left eye. The zonular dialysis was not evident intraoperatively despite iridodonesis precluding the use of CTR. A single piece rigid Poly Methyl MethaAcrylate posterior chamber IOL of +15.00 D power, with 6.5 mm diameter optic and an overall diameter of 13.5 mm (Aurolab, Tamil Nadu, India) was implanted [Figure 3]. Follow up was performed at 1, 3, 4, 6, 12 weeks postoperatively. At 3 months postoperatively, BCVA in the left eye was 6/9 with +2.00 D sphere and +1.0 D cylinder at 90° and the PCIOL was well centered.

Figure 3

Per operative photograph after the intraocular lens implantation

DISCUSSION

Anterior megalophthalmos is a rare inherited condition that is characterized by the presence of megalocornea, ciliary ring enlargement and secondary effects of iridodonesis, miosis, atrophy of iris stroma, and occurrence of cataract.5 X-linked genetic transmission is found in 50% of cases of anterior megalophthalmos (possibly located on Xq21.3-q22), autosomal transmission in 40%, and sporadic transmission in the remaining 10%. It is commonly seen in males (90%) because X-linked inheritance is common. Our case being a female, with a negative family history probably suggests a sporadic occurrence. She had megalocornea, deep anterior chamber, hypoplasia of iris stroma as pupils failed to fully dilate pharmacologically as well as anterior embryotoxon with presenile cataract fitting into the diagnosis of anterior megalophthalmos.

The lens in anterior megalophthalmos is of normal size,6 but the ciliary ring is enlarged, which is responsible for weakened zonules and subluxation of lens. One of the major challenges in the management of cataract in patients with anterior megalophthalmos is prevention of IOL decentration. Various techniques have been recommended including placement of iris clip IOL in the posterior chamber7 and custom IOL.8 Javadi et al.9 have reported safe implantation of standard IOL (13.4 mm in length with 7 mm optic) in six eyes without complications. Tsai et al.10 have also reported the use of standard IOLs (13 mm in length and 6 mm optic) in a case of anterior megalophthalmos who underwent phacoemulsification. In our case we were able to implant a standard IOL (13.5 mm overall length with 6.5 mm optic) successfully.

Introduced in 1991, CTRs have become indispensable in stabilizing the capsular bag in the presence of generalized weakness or dehiscence of less than 150°.11 Hence, placement of conventional CTRs are not limited to only zonular dialysis and can be used in generalized weakness of zonules. Even though there was phacodonesis, zonular dialysis was not evident and IOL implantation was possible in our case without the use of CTR.

Zare et al.12 have suggested preoperative use of ultrasound biomicroscopy (UBM) in anterior megalophthalmos to measure the actual size of the capsular bag. Zare et al.12 were able to implant a standard foldable IOL as the capsular bag diameter in their case was found to be normal by ultrasound biomicroscopy. The hyperopic shift could be explained with greater posterior shift of the IOL due to long zonules. In our case it was not possible to assess the capsular bag diameter, we assume that it would have been of normal size as there was no IOL decentration for the entire follow-up period.

Anterior megalophthalmos is a rare condition with a male preponderance. However, there is relative paucity of female cases (such as the current case) in the literature. Presence of iris stromal atrophy and zonular dialysis can cause difficulties during cataract surgery. However, good visual rehabilitation can be achieved with standard IOL in these anatomically challenged eyes, even in centers with limited or no access to investigative techniques such as UBM.