CLINICAL

  POSTERIOR

‘I’M SEEING DRIFTING STRINGS’

ARE FLOATERS RELATED TO SICKLE CELL RETINOPATHY?

SHERROL A. REYNOLDS, O.D., F.A.A.O.

A 45-YEAR-OLD African-American female presented complaining of “stringy” floaters OS, for a duration of about one week. The patient did not report flashes of lights and denied trauma. She reported taking medications for hypertension and hypercholesterolemia.

The patient’s BCVA was 20/20 OU. Pupils, ocular motilities and confrontation visual fields were normal OU. Anterior segment exam was unremarkable OU. However, dilated fundus exam showed an isolated dot hemorrhage and scattered drusen OD. Also, scattered drusen and an inferior-temporal branch retinal artery occlusion (BRAO) with adjacent “sea-fan” neovascularization was observed OS and confirmed on intravenous fluorescein angiography with leakage of the newly formed vessels.

The patient denied having diabetes, sarcoidosis or any other medical problems, but she did reveal she had sickle cell trait, a variant of sickle cell disease (SCD). Could her retinal changes stem from this disorder?

Here, I discuss the etiology, symptoms, clinical signs and diagnosis/management of SCD to help you decide.

ETIOLOGY

SCD occurs primarily in Mediterranean or African-American individuals. Millions of people throughout the world are affected by SCD, according to the CDC. Moreover, about 3 million people (8% to 10% of the population) in the United States have the sickle cell trait, in which individuals inherit one-normal hemoglobin (A) and one-sickle hemoglobin-S, known as AS, though some individuals are unaware of it, according to the American Society of Hematology.

SCD, on a whole, is a common inherited multisystem disorder in which genetic mutations lead to structural abnormalities within the hemoglobin. These structural abnormalities cause red blood cells (erythrocytes) to change into rigid sickle-shaped cells in response to hypoxia, acidosis, oxidative stress and infection. In turn, these cells do not provide enough oxygen to the body’s tissues, leading to systemic complications, such as chronic hemolytic anemia, episodes of recurrent pain and a host of ocular problems (explained below). SCD variants, such as sickle cell trait, mentioned above, are based on inheritance patterns and mutations within the sickle cell gene. In addition to sickle cell trait, other common types include sickle cell anemia (homozygous SS disease), sickle cell hemoglobin C disease (SC) and S-Thal (beta thalassemia).

SYMPTOMS

The Symptoms of SCD may include:

• Decreased VA

• Eye pain

• Flashes

• Floaters

• Peripheral vision loss

• Redness (especially with neovascular glaucoma or a hyphema complication.)

CLINICAL SIGNS

A myriad of ocular changes can be seen in SCD patients, and most are mild and can, therefore, go unrecognized. They are grouped as:

• Anterior segment. Conjunctival “comma or corkscrew-shape” vessels, sectoral iris atrophy, spontaneous hyphema, iris neovascularization or neovascular glaucoma are seen.

• Non-proliferative sickle cell retinopathy (NPSCR). Venous tortuosity of the peripheral vessels, intraretinal salmon-patch hemorrhages, iridescent spots, black sunburst, angioid streaks (leads to choroidal neovascular membrane) and discrete patches of the midperipheral darker retina associated with sickle cell disease, sickling maculopathy (microaneurysm, hairpin-shaped venular loops and irregularities of the foveal avascular zone) and small, dilated capillary vessels at the optic nerve head are seen.

• Proliferative SCR. Peripheral arteriolar occlusion, peripheral arteriovenous anastomoses, neovascular and fibrous proliferations with “sea-fan” formation, vitreous hemorrhage and tractional retinal detachment are seen.

DIAGNOSIS/MANAGEMENT

The following should be used to aid in the proper diagnosis of SCD:

• The Goldman 3-mirror lens. This provides a detailed view of peripheral SCR changes.

• Retinal photography. This captures early and subtle retinopathy and can be used to monitor SCR disease progression through time.

• Widefield retinal imaging. This can enhance the views of peripheral vasculature SCR changes and aid in identifying high-risk characteristics, such as neovascularization for proliferative SCR. Some platforms allow multimodal imaging fluorescein angiography and fundus autofluorescence.

• SD-OCT. This captures changes, such as choroidal neovascular membrane, in eyes with SCR-angioid streaks. A relatively new SCR OCT finding is paramacular temporal thinning, which occurs in about 50% of eyes with SCD, according to Archives of Ophthalmology. Atrophy of the inner retinal layers, due to macular infarction, can also be observed.

• Optical coherence tomography angiography. This can detect areas that have subtle ischemic changes, such as macular irregularities associated with SCD, as alteration of the deep capillary network.

• Intravenous Fluorescein and indocyanine green angiography (IVFA). This can show retinal capillary non-perfusion pattern and “sea-fan” neovascularization leakage.

• Ultrasound imaging. This allows for the assessment of proliferative SCR changes, such as tractional retinal detachment or vitreous hemorrhage.

Scattered drusen and more.

IVFA showing vessel leakage.

In terms of management, patients who have NPSR should be monitored with dilated follow-up every six months. Those with salmon patch hemorrhage should be evaluated every three months for resolution of the hemorrhage, while those with angioid streak choroidal neovascular membranes require co-management with a retinal specialist. Patients with the first two stages of proliferative SCR changes should be monitored every three months, while those with stages three to five should be co-managed with a retinal specialist. Indications for treatment (i.e. laser photocoagulation, intravitreal injection of anti-VEGF, vitrectomy and retinal detachment surgery) are not always clear because as much as 60% of “sea-fan” neovascularization will spontaneously resolve, states Ophthalmology.

THE ANSWER

If you diagnosed this patient with SCR, you are correct! She also had a BRAO, more likely due to her sickle cell trait and concomitant hypertension and hypercholesterolemia. She was monitored closely (three-months) with observation and co-managed with a retinal specialist and her treating hematologist. Subsequently, she was treated with anti-VEGF therapy and is still being closely monitored.

SCD remains a major public health concern because of its potentially significant morbidity and mortality. With millions diagnosed with this disorder, early diagnosis of vision-threatening complications is important. OM

DR. REYNOLDS is an associate professor at the Nova Southeastern University College of Optometry and clinical preceptor/attending in the college’s diabetes and macular clinic. She is a fellow of the Optometric Retina Society and chairperson for the Florida Optometric Association Healthy Eyes Healthy People Committee. Comment at tinyurl.com/OMcomment.