Sir,

Introduction

We studied 15 patients who suffered solar retinopathy as a result of viewing the subtotal (98%) solar eclipse in East Sussex on 11th August 1999.

Methods

Patients who viewed the eclipse were defined as having solar retinopathy if they were symptomatic with visible retinal signs consistent with a solar burn. At 3 months achromatic contrast sensitivity (ACS) and chromatic contrast thresholds (CCT) were tested. They were reviewed at 8–12 months if still symptomatic.

ACS and CCT were measured using a cathode-ray-tube based gratings system.1 Our system tests the central four degrees of vision. ACS was measured at six spatial frequencies: 0.33, 0.66, 2.2, 3.4, 10.0, and 17.0 cycles per degree. The system presents vertical sinusoidal gratings of light and dark bars of varying luminance. CDT used low spatial frequency sinusoidal gratings with standardized equiluminance along either the red/green or tritan confusion axes.

Results

No symptom at presentation predicted long-term visual loss (Table 1). Most patients experienced a central, dark, positive scotoma.

Table 1 Clinical case summaries
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One patient (case 9) used approved protective sunglasses bought from a supermarket. These were double aluminised, neutral density 5 optical quality polyester lenses and claimed transmittance of 0.001% of visible light and no transmittance of ultraviolet or infrared light.

One patient (case 14) admitted to taking ‘speed’ (presumably an amphetamine-based drug) and viewed the eclipse for 30 min unprotected with resulting severe burns (Figure 1).

Figure 1
figure 1

Colour fundus photographs of the right and left eyes of a 17-year-old female patient taken 3 months after the eclipse. These show classical slightly eccentric foveal deep retinal hypopigmentation. She said she had watched the eclipse for 30 min under the influence of ‘speed’. Visual acuity was 6/9 on the right and 6/6 left at this time (Case 14). On review at 1 year these signs had almost disappeared except for a small approximately 200-μm pseudohole at the right fovea.

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Only two eyes of two patients (cases 5 and 14) had worse than 6/6 vision at final follow-up and one of these was lost to follow-up after 3 months. However, in many patients subtle visual disturbances persisted. In none of the patients did visual acuity deteriorate after presentation.

Most patients initially had a deep white spot centrally or slightly eccentrically in the foveal region which persisted at 3 months in some of the worst affected (Figure 1) but eventually resolved. Pseudoholes remained in some cases (Table 1).

Significantly abnormal ACS and CCT (worse than two standard deviations from the means of age-matched controls) were only detected in two patients. In one eye of each of these patients there were moderate deficits at low and medium spatial frequencies but severe deficits at high spatial frequencies. CCT were also significantly worse than 2 SD from the mean CCT of aged-matched controls for both red-green and tritan contrast thresholds in these eyes. The other eye of patient 14 also had significantly affected red-green and tritan colour vision and milder but significantly affected CCS at low and high spatial frequencies.

Discussion

Eclipse retinopathy is the commonest cause of solar retinopathy.2 Victims of solar retinopathy may complain of blurred vision, a central black spot and metamorphopsia. After 6 months the visual acuity is usually in the range of 6/5 to 6/12 but frequently with a small central subjective scotoma. Visual acuity does not always recover and has reportedly remained as low as 3/60 with permanent retinal damage in the form of retinal holes and pseudoholes.3

After a week the initial deep yellow exudate shrinks and may be surrounded by a red halo followed by retinal pigment epithelium hypopigmentation with surrounding pigment clumping at 6 weeks. The appearance of a lamellar macular hole at or adjacent to the foveal reflex may develop.4

Ultrastructurally, photoreceptors suffer fragmentation and vesiculation of the rod and cone outer segment lamellae as well as pyknosis of nuclei especially of parafoveal rods. Relative survival of foveal cones may account for the good prognosis for visual acuity.5

Two large studies of solar retinopathy were found. Rai et al6 describe 3-year follow-up of 319 solar retinopathy patients, 126 of whom had observed a solar eclipse. They found a similar good prognosis for visual acuity and only a small proportion with longstanding metamorphopsia (11 eyes of 319 patients). Abnormal tritan colour contrast sensitivity was found in five patients investigated.

Another study7 was of 58 solar eclipse-related solar retinopathy patients with a mean of 4.2 years follow-up. This found a rapid initial improvement in visual acuity over the first month with no further improvement after 18 months.

Our study concurs that patients can make an excellent recovery in the first 3 months following a solar retinal injury. 6/6 visual acuity was attained in cases 4, 14 and 15 despite initial visual acuities of 6/36, 6/24 and 6/18 respectively. Persistence of foveal hypopigmentation at 3 months in cases 5 and 14 may have been predictive of worse long-term visual acuity as may have been significantly abnormal achromatic contrast sensitivity (ACS) and chromatic contrast thresholds (CCT).

Conclusion

Visual acuity can improve considerably in the majority of eclipse-related solar burns. However, the persistence of visual symptoms in those with mild burns would suggest that even brief glimpses of a solar eclipse should be avoided.