Sir,

A common problem in patients with retinopathy is whether they will benefit from surgical correction of co-existent cataracts.1 The timing of surgery is dependent upon a clinical assessment of the degree of cataract compared to severity of retinopathy. The case presented here illustrates such a dilemma where cataract surgery exceeded all expectations of predicted benefit in the context of severe, widespread retinopathy.

Case report

A 28-year-old female was referred to our ophthalmic department in 1995. Her optometrist had noted reduced acuity and cataracts. Other medical history of note was chronic renal failure, due to nephronopthisis, that had required kidney transplantation in 1979. The patient reported no skeletal abnormalities and normal hearing. The patient’s identical sibling had also suffered from chronic renal failure that had resulted in death in infancy. The patient’s brother was also affected with renal failure and suffered from nyctalopia. There was no other family member affected, the parents of the patient were reported to have normal vision and their union was non-consanguineous.

At presentation in 1995, right visual acuity was 6/18 with a +0.75/−2.25 at 5° lens and 6/18 left with a +2.0/−2.0 at 177° lens. No nystagmus was present. Pupil responses were normal. Anterior segment examination revealed marked, bilateral, posterior subcapsular cataracts. Retina examination was difficult due to the lens opacities, no definite retinopathy was identified but both optic nerve heads were described as ‘abnormal’.

At that time, the cataracts were presumed secondary to the oral steroid immunosuppression and cataract surgery was offered. The patient underwent uneventful phacoemulsification cataract surgery in the right eye in 1995 and in the left eye 4 months later. The patient subsequently required bilateral YAG capsulotomy resulting in visual acuities of 6/9 right and left with appropriate spectacle correction.

By December 2000, the patient’s main complaints were of a significant deterioration in her night vision. Visual acuity was still 6/9 with spectacles. Retina examination revealed pale, non-cupped optic discs, attenuated blood vessels and featureless maculae (Figure 1). Visual field assessment revealed a mild abnormality in the right eye and an upper nasal defect in the left (Figure 2). This asymmetric field deficit did not correspond with the degree or extent of retinal abnormality seen clinically. Such field defects, especially those localised to the upper field are however commonly seen in moderately severe, panretinal, outer retinal dystrophy.2 Surprisingly, electrophysiological investigation (using ISCEV standard protocols and Goldfoil electrodes) reported pattern and full field electroretinograms (ERGs) as undetectable.3 Visual evoked potentials (VEPs) were delayed. It was concluded that these findings were indicative of severe, generalised, retinal dysfunction and VEP abnormalities were secondary to the retinal changes. The electrophysiological investigations, kidney disease and family history suggested a diagnosis of Senior–Loken syndrome.

Figure 1
figure 1

Retinal photographs of our patient with Senior–Loken syndrome demonstrating widespread pigmentary abnormalities, vascular attenuation and secondary optic atrophy.

Full size image
Figure 2
figure 2

Goldmann visual fields of our patient with Senior–Loken syndrome showing an essentially normal right visual field and an upper nasal defect in the left visual field.

Full size image

Comment

Nephronopthisis is a severe kidney disease due to renal tubular fibrosis, renal atrophy or dilatation and thickening of the tubular basement membrane. It is an important cause of renal failure in childhood. Senior–Loken syndrome accounts for an estimated 16% of nephronopthisis cases when a retinopathy and family history suggestive of autosomal recessive inheritance is seen.4 Loken et al5 first described this combination in a brother and sister in 1961. Senior et al6 and Fairley et al7 also reported the same combination in other families.

The retinopathy in Senior–Loken syndrome, on the basis of retinal appearance and electrophysiology, has been reported as severe, leading to blindness in childhood. This has been described as either a childhood-onset retinitis pigmentosa or a Leber’s congenital amaurosis type of abnormality.8 A single case report describes a sector retinitis pigmentosa with subnormal but detectable ERG.9 Recently, a patchy retinopathy without visual symptoms has been described with nephronopthisis in families with deletions of the NPH1 gene.10 ERG abnormalities have also been reported in asymptomatic heterozygotes.11 Other associated ocular abnormalities include congenital cataracts, Coat’s disease and keratoconus.12

The case presented here is notable for several reasons. Relatively good visual acuity and significant retention of useful visual field has not previously been described in adult patients with Senior–Loken syndrome. This was despite almost undetectable electrical responses on electrophysiological investigations. This serves to remind us that undetectable electrical responses in clinical practice do not necessarily correlate with functional blindness.

Also, this is the first reported case of cataract surgery in a patient with Senior–Loken syndrome in which a significant benefit was gained. With marked advances in renal medicine the long-term survival rate in Senior–Loken syndrome is extending and more adult cases are being seen. We conclude that such patients may well benefit from surgery where cataract is present. Severe electroretinographic abnormality should only be considered a relative contraindication to this. Other clinical measures may be more reliable predictors of a successful surgical outcome, such as the presence of nystagmus or information from potential acuity meter investigation.