That the visual acuity is reduced to this great an extent could be accounted for by, I suppose, one of the generalized photoreceptor dystrophies. The presence of a mild RAPD, which is presumably in the right eye [though nothing has been mentioned with respect to the RAPD and the EYE] hints at a) massive retinal damage, which can be clearly observed in the photographs and b) an optic nerve conduction anomaly; however, the anomaly is unlikely, still undeniable. ‘The left eye is normal’ casts doubt on our knowledge as vision is not the only yardstick of the status of the eye. The right eye has this reduced a level of vision because of substantial retinal changes, esp those in the macula. And this early loss of vision in the right eye prompted an exotropia in the right eye, for 'oculo-motor coordination and balance' at an early stage of life is possible only after adequately good vision is present in each of the eyes. I am here interested to know, the status of dark- and light-adaptations, and if nystagmus is present.

Appears to have some neurological involvement as well

You have presented an interesting case of an adult male with a history of poor vision OD since childhood, a sensory exotropia, healthy nerves and vessels, and a unilateral pigmentary retinopathy. Most likely this is due to old infection, but other possibilities include an old foreign body with siderosis, inflammatory causes such as Harada's disease or AZOOR, old retinal vascular occlusive events or perhaps an atypical presentation of a bilateral process such as retinitis pigmentosa or vitamin A deficiency. Likely infectious causes are onchocerciasis, diffuse unilateral subacute neuroretinitis, syphilis, ophthalmomyiasis, toxoplasmosis, or rubella. As he is from Africa, there are probably several more infectious diseases that may cause a pigmentary retinopathy that I am unfamiliar with. Perhaps someone with expertise in tropical medicine could add to my list. I recommend a careful history, consider a plain-film x-ray if there is a chance of a retained foreign body, then a laboratory work-up for the most likely infectious diseases. If that does not lead to a diagnosis then I would consider electrophysiology studies to rule out unilateral retinitis pigmentosa, but this is unlikely. There are many good papers on the differential diagnosis of unilateral pigmentary retinopathy. Here is one:

Silveira C, Belfort R Jr, Nussenblatt R, Farah M, Takahashi W, Imamura P, Burnier M Jr. Unilateral pigmentary retinopathy associated with ocular toxoplasmosis. Am J Ophthalmol. 1989 Jun 15;107(6):682-4.

Thank you again for presenting an interesting case. Please let us know what you find.

Hi Mohammed

This is an interesting case and initially looks like an atypical RP, however the normal disc and vessels as well as the pigment changes and the fact that the left eye is normal (I assume you mean that the acuity is 20/20) does not sit well with RP. The question would be if the squint is due to the retinal changes or to other reasons, assuming its due to the retinal changes it quite odd that the left eye still has good vision but on the fundus photo looks similar to the right eye. Did you perhaps do an OCT or electrophysiology? What was the colour vision like and how does the visual field look in the left eye? What about FAF images

Probably a rare RPE/ Chorio-retinal dystrophy?

You can add to the differential enhanced S-cone syndrome and Goldmann-Favre syndrome

Definitely looks like an atypical presentation of some form of RP as suggested in the comments ! 

Both photographs are of the right eye. It is a little confusing because the top photo is of the nasal retina OD, but it could easily be mistaken for OS. I agree with Dr. Loft that fundus photos OS would be helpful.

Interesting case Dr Abdull. Exhaustive D/D has been given already by Dr. Lane. I'll just give my perspective. The differential diagnoses should be in 2 categories: etiological and anatomical. Etiology should include inflammation, hereditary degeneration/dystrophy, trauma and settled RRD. Anatomically, we need to look at retinal level of disease: this case looks like outer retinal, RPE and choriocapillaris are hit predominantly, inner retina and blood vessels are apparently spared (There may some arterial attenuation: please recheck; did you actively looked for vascular sheathing, esp. in midperiphery?)

Since there is no visible pattern of pigmentation, disc and vessels are not visibly affected and it's unilateral, dystrophic conditions are less likely as already suggested.

Trauma (mainly blunt, closed globe) should have some vitreous base and pars plana disturbances; please look for them. There may be no history in an old case of childhood trauma.

A spontaneously settled RRD can also present this way, again, please look at the pattern of pigmentation superiorly, are there any borders/demarcation lines?

The most likely diagnosis is inflammatory, though I'd like to see some vascular sheathing and some evidence of fibroglial scarring to firm up that hypothesis. Please check pars plana, esp. inferiorly to look for it. If the patient spent childhood in a coastal area, one more possibility besides Dr Lane's list is DUSN. Again, lack of disc pallor goes against it, to some extent. 

I differ from others in not advising ANY investigations, serological or psychophysical...esp. expensive ones. Inactive uveitis doesn't need to be investigated, esp. 4 decades after the episode. The other eye is unlikely to be affected which is our only concern right now. Functional tests like ERG/EOG won't help: very likely to be abnormal, but that won't point to any genetic disease. OCT is likely to show retinal atrophy and nothing more. Better to examine the family members if available to investigate that aspect. Keep the patient on yearly follow-up.

Thank you all very much for these interesting answers. i will try to get the patient again to get the image of the other eye for you to see. The VA was 20/20 in the "normal eye" and it had no abnormal changes visible to me at the time of the first examination.I will also follow up with some of the other investigations as you all suggested.

Hi Mohammed

If the other eye has no retinal signs I will tend to agree with a local cause such as an infection in the right eye. RP and the other dystrophies will typically affect both eyes albeit with different severity. As he is from Africa (West, Central or East?) my vote would be Onchocerciasis. Look for the other typical associated signs, leopard skin on the shins, lizard skin, onchoceromas, chorioretinitis which leads to the fundus changes observed. 

Amblyopia-agree with Kieran loft

I am happy with the interest this has generated. Dirk, the patient is from West Africa in an area where Onchocerciasis is endemic. But he has no other signs of oncho. It has been ruled out. And most oncho cases we see around here affect both eyes though not always to the same extent.

Dear Mohammed,,

Thank you for sharing this case with us. As said, RP is less likely in such a case but still an important differential diagnosis, therefore, electrophysiology is important. Other differential diagnosis will include infectious causes ( namely choroiditis ) , onchocerciasis , syphilis and sarcoidosis ( I had a patient with similar picture that was biopsy diagnosed with sarcoidosis ). Dystrophies are usually bilateral and less likely,,,

I agree with you Osama.

This is indeed a very interesting case. My recommendation is that although the IOP is 14 this does not rule of glaucoma completely. Poor vision from childhood may be indicative of amblyopia. An OCT is imperative and a field test is also important. How was IOP checked?

Dear all,

my contribution is about the diagnosis of amblyopia that some of you suggested. Just wanted to remind that an eye would be consider amblyopic when there is no organic damage, but function not developing.

In this case, it is not amblyopia as we can clearly see the damage to the retina with obvious pigmentary changes.

Agree that left eye wide field would be more helpful as there might also be some subtle changes.

Need to think congenital infective cause such as rubella, syphilis.

In the African context, parasite like onchocerca volvulus should be bore in mind and ruled out.

The image looks like an atypical form of RP.