Rickettsial retinitis-an Indian perspective

Treatment Outcomes of Presumed Rickettsial Retinitis: Evidence from OCTA Based Quantitative Analysis

AIM

To quantify retinal ischemia following presumed rickettsial retinitis (RR). To compare outcomes between initial treatment with Doxycycline (Group 1) versus steroids (Group 2).

METHODS

Retrospective analysis of patients with presumed RR was done. ImageJ software was used to obtain %area of ischemia on swept-source optical coherence tomography angiography (SS-OCTA).

RESULTS

Eleven eyes of 8 patients belonged to Group1 and 6 eyes of 3 patients belonged to Group 2. The BCVA improved from logMAR 0.8 ∓ 0.7 to logMAR 0.06 ∓ 0.08 (p < 0.002) and central foveal thickness (CFT) changed from 479μ ∓ 341.3μ to 163.5μ ∓ 20.5μ (p < 0.005) after a median of 5 weeks in Group 1. In Group 2, BCVA improved from logMAR 1.03 ∓ 0.05 to logMAR 0.23 ∓ 0.23 (p < 0.004) and CFT changed from 286.5μ ∓ 158.8μ to 177.5μ ∓ 25.9μ (>0.05) following a mean of 11 weeks. Mean %area of ischemia was 4.6 ∓ 1.5 in Group 1 and 13.9 ∓ 4.1 in Group 2.

CONCLUSION

Analysis of flow deficit on SS-OCTA confirms that treatment with Doxycycline in presumed RR results in less ischemia and quicker recovery than initial treatment with steroids.

Post-fever Retinitis With a Positive Weil-Felix Test: A Study From a Tertiary Center in South India

Background Post-fever retinitis (PFR) is reported two to six weeks after fever and affects one or both eyes. Rickettsial fever is one of the most common causes of PFR. This study aimed to report the clinical features and treatment outcomes of PFR cases with a positive Weil-Felix test. Methodology In this study, we collected demographic data, fever details, eye symptoms, ocular examination findings, optical coherence tomography (OCT) and fundus fluorescein angiography findings, laboratory findings, and length of follow-up of consecutive PFR cases with a positive Weil-Felix test. All cases were treated with oral doxycycline and prednisolone. Final best-corrected visual acuity (BCVA) and ocular examination findings were recorded. Visual field examination and follow-up OCT results were noted if available. Results A total of nine patients (eight males) with a mean age of 39.1 years with fever before ocular symptoms and positive Weil-Felix test were included. Six patients had bilateral disease. The mean initial and final BCVA in the affected eyes was 1.16 and 0.35 logMAR units, respectively (p < 0001). All 15 eyes had typical white retinitis patches and retinal hemorrhages which resolved after treatment. OCT showed hyperreflectivity and inner retinal disorganization over retinitis patches. White subretinal lines were noted in three patients and retinal nerve fiber bundle defect with corresponding visual field defect was seen in one eye. Conclusions In this study, PFR due to rickettsia infections has been reported from our region for the first time. Hence, eye specialists in the region should be aware of this entity.

Serological profile of patients suspected with non-scrub typhus rickettsioses

BACKGROUND

Rickettsial pathogens are Gram-negative, obligate intracellular bacteria. They are transmitted by arthropods and are responsible for a wide variety of disease, from minor to life-threatening, which have a global effect on human health. Limited data are available on the prevalence of rickettsial diseases from India, and the disease epidemiology is not fully described. This study aimed to diagnose non-scrub typhus rickettsioses including spotted fever and typhus group of Rickettsia in clinically suspected patients by using standard serological tests and recognition of common epidemiological conditions and clinical manifestations.

METHODS

During the study period, a total of 700 patients of all ages with acute febrile illness were enrolled. Patients were screened for rickettsial infection using IgM Enzyme-linked immunosorbent assay (ELISA) and Immunofluorescence assay (IFA) was performed to confirm the ELISA positive results. The relevant demographic, clinical, and laboratory details of patients were documented and analyzed.

RESULTS

Of 700 samples tested, 141 (20.2%) were found to be positive for IgM antibodies against rickettsioses using ELISA and IFA. SFGR was positive in 15 (2.2%), TGR was positive in 112 (16%) and 14 (2%) samples were positive for both groups. 20 (14.2%) patients required admission to the intensive care unit (ICU), and 24 (17%) in-hospital deaths occurred.

CONCLUSIONS

The prevalence of rickettsioses in India appears to be underestimated; therefore, increased awareness and improved diagnostic testing could facilitate early detection of cases, pathogen-targeted appropriate treatment, and improved outcomes for patients. Despite the fact that Rickettsiae can be isolated or detected using molecular techniques in clinical specimens, serology still remains the most commonly used diagnostic method for rickettsioses around the world. Our study helps bridge the gap of limited data on Rickettsia in north India and could be useful for future epidemiological investigation of rickettsial diseases and outbreaks.

A Review of Rickettsial Diseases Other Than Scrub Typhus in India

Rickettsial diseases (RD) are widely reported all over the world. Scrub typhus (ST) is a major tropical infection which is well documented all over India. Therefore, the index of suspicion of scrub typhus is high among physicians with regard to patients presenting with acute febrile illness (AFI) and acute undifferentiated febrile illness (AUFI) in India. Rickettsial diseases other than ST (non-ST RDs), which include spotted fever group (SFG) rickettsioses and typhus group (TG) rickettsioses are not uncommon in India, but the index of suspicion is not as high as ST unless there is a history of the presence of fever with rashes and/or recent arthropod bites. This review aims to look into the Indian scenario on the epidemiology of non-ST RDs, especially the SFG and TG rickettsioses based on various investigations, spectrum of clinical presentation, challenges and gaps in knowledge to suspect and diagnose these infections.

Stepwise approach for fundus imaging in the diagnosis and management of posterior uveitis

An array of retinochoroid imaging modalities aid in comprehensive evaluation of the immunopathological changes in the retina and choroid, forming the core component for the diagnosis and management of inflammatory disorders such as uveitis. The recent technological breakthroughs have led to the development of imaging platforms that can evaluate the layers of retina and choroid and the structural and functional alteration in these tissues. Ophthalmologists heavily rely on imaging modalities such as dye-based angiographies (fluorescein angiography and indocyanine green angiography), optical coherence tomography, fundus autofluorescence, as well as dye-less angiography such as optical coherence tomography angiograph,y for establishing a precise diagnosis and understanding the pathophysiology of the diseases. Furthermore, these tools are now being deployed with a 'multimodal' approach for swift and accurate diagnosis. In this comprehensive review, we outline the imaging platforms used for evaluation of posterior uveitis and discuss the organized, algorithmic approach for the assessment of the disorders. Additionally, we provide an insight into disease-specific characteristic pathological changes and the established strategies to rule out disorders with overlapping features on imaging.

Epidemic Retinitis with Positive or Negative Weil Felix Test - a Comparative Study and Outcome with Doxycycline

PURPOSE

To compare clinical manifestations and disease outcomes in Epidemic Retinitis (ER) with positive or negative Weil Felix Test (WFT).

METHODS

Retrospective, observational, comparative study. WFT positive or negative patients formed Group 1 and 2, respectively. Patients receiving oral doxycycline monotherapy formed subgroup A and B. Duration of resolution of macular edema and retinitis was compared.

RESULTS

Novel finding of "ring retinitis" was observed equally in group 1 and 2. Complete resolution of macular edema took 41.3 days (range: 30-60 days) and 43.68 days (range: 20-105 days) (p = .668) and retinitis lesions resolved in 34.3 days (range: 14-65 days) and 34 days (range: 12-60 days) (p = .875) in group A and B, respectively. All (n = 14) eyes with retinitis within 1 disc diameter of fovea improved better than 20/80 except 1.

CONCLUSION

No significant difference with respect to clinical, imaging findings and the treatment outcome was observed in WFT positive or negative cases.

Bilateral optic disc edema with subconjunctival hemorrhage: Attributed to scrub typhus?

A 15-year-old female patient presented with complaints of headache, blurring of vision, and redness of both eyes for 15 days and fever for 20 days. Her best-corrected visual acuity (BCVA) was 20/40 in both eyes. Anterior segment examination was normal except for subconjunctival haemorrhage in both eyes. Examination of the posterior segment showed disc oedema in both eyes. Her blood investigations revealed platelet count to be 1.5 lakhs per cubic mm, and leucocyte count to be10,700 per cubic mm. CSF culture showed seven cells per microlitre,76% lymphocytes and CSF samples negative for gram stain, acid-fast bacilli, and culture. Further investigation for IgM titre for scrub typhus was positive. She was treated with oral doxycycline. On follow up after three weeks, both the subconjunctival haemorrhage and bilateral disc oedema resolved with BCVA of 20/20 in both eyes. She was kept on follow up and has not presented with any fresh complaints until six months after the initial presentation."

Macular infarction in presumed rickettsial retinitis with late vascular remodelling

A middle-aged man had been diagnosed as retinitis and treated with steroids previously. The patient had developed macular infarction in the course of illness. We diagnosed him to have rickettsial retinitis on the basis of clinical features and positive Weil-Felix test. The patient's condition improved after treatment with oral antibiotics. The vasculature of the infarcted macula showed partial reperfusion late in the course of follow-up.

Ocular manifestation of rickettsial disease in South Indian population

Purpose

The aim of this work was to study the ocular manifestations and its management in spotted fever and typhus group of rickettsial disease.

Methods

A retrospective analysis of 50 patients with serologically confirmed Rickettsial disease. In all patients, relevant history, investigations and treatment details were collected and they underwent complete ophthalmic evaluation including measurement of best-corrected visual acuity, anterior segment examination and dilated fundus examination.

Results

Mean age was 12.5 ± 8.99 years. Of the 50 patients, 40 patients were ≤18 years of age and 27 (54%) had ocular involvement. Out of 27 patients, bilateral involvement was seen in 10 patients. Most of the patients had no ocular symptoms. Ocular findings included, Retinal vasculitis 6 (22.22%); macular edema 4 (14.81%); vasculitis with macular edema 1 (3.7%); Retinitis 7 (25.92%); Papilloedema 6 (22.22%); Papilloedema with 6^th cranial nerve palsy 1 (3.7%); Isolated 6^th cranial nerve palsy 1 (3.7%) and optic neuritis 1 (3.7%). Ocular involvement was more common in double antigen group (68%) than spotted fever group (50%) or Scrub typhus group (21%) (P = 0.01). Ocular involvement was seen in 94% of the patients with CNS involvement. Cases with bilateral involvement (P = 0.01), pediatric age group (P = 0.01) and CNS involvement (P = 0.02) had poor visual outcome.

Conclusion

Rickettsioses patients can have ocular manifestations with predominant posterior segment involvement during acute phase of illness. Ocular involvement was more common in the double antigen group. For any patient who presents with fever and rash living in endemic area, ophthalmic evaluation should be part of routine checkup during the acute phase of illness associated with less frequent ocular symptoms.

Epidemic retinitis and community outbreaks

Purpose:

The objective of this study was to correlate seasonal variation of epidemic retinitis (ER) with concurrent community outbreaks.

Methods:

This is a retrospective, observational, comparative study conducted in a tertiary care eye hospital in south India. Monthly variation in number of ER cases in comparison with reported community outbreaks by Integrated Disease Surveillance Program (IDSP) from 2009 to 2020 in the same region were studied. Month-wise graphs against number of patients were plotted for ER and for each community outbreak.

Results:

ER was diagnosed in 163 patients. Diagnosis of presumed rickettsial ER was made in 48 cases (29.44%), chikungunya in 5, dengue in 3 and typhoid in 6 cases, while in other cases the etiological diagnosis remained uncertain (n = 101). Multiple positive serological tests were seen in 6 patients (Weil Felix Test (WFT) with WIDAL in 4 and chikungunya IgM with WFT in 2 patients). Relevant reported outbreaks by IDSP were: Pyrexia of unknown origin (PUO) (n = 5148), Chikungunya (n = 6577), Dengue (n = 7350), Measles (n = 1422), Mumps (n = 881), Rubella (n = 288), Malaria (n = 2262), Chicken Pox (n = 2385), Typhoid (n = 597), Kyasanur Forest Disease (n = 381), Scrub Typhus (n = 13), Typhus fever (n = 4), Japanese Encephalitis (n = 15). None of the outbreak graphs pattern was identical or similar to the graph of ER. Inverse relation of the graph of dengue outbreak with ER was observed.

Conclusion:

Inverse correlation between dengue and ER should be further studied for causation, which we believe may prove dengue as least common cause. Reporting of rickettsial outbreaks should be enhanced by undertaking statewide awareness and procurement of gold standard tests.

Clinical features, optical coherence tomography findings and treatment outcomes of post-fever retinitis

Objectives:

To study the clinical features, optical coherence tomography (OCT) findings, treatment options and follow-up outcomes of post-fever retinitis (PFR).

Subjects:

A total of 19 eyes of 13 patients, diagnosed with PFR (retinitis following febrile episode) over 2 years were retrospectively studied.

Methods:

Documented history, baseline clinical features and systemic investigations performed for PFR were reviewed. Fundus findings, foveal architecture on swept-source OCT, the treatment options and the follow-up outcomes including best-corrected visual acuity (BCVA) and central foveal thickness (CFT) were reviewed and analyzed.

Results:

Common fundus findings included whitish retinitis lesions (100%), macular star (95%, 18eyes), retinal flame-shaped hemorrhages (63%, 12 eyes), inflammatory retinal vessels (30%, 6 eyes), vitreous hemorrhage (one eye) and OCT findings included neuro-sensory detachment (79%, 15 eyes), intraretinal white dots (89.5%,17 eyes). The baseline median log MAR BCVA and CFT were 1.30 (interquartile range (IQR):0.8–1.8) and 423 microns (IQR:182–555). Overall, nine patients (12 eyes) received a combination of oral doxycycline and oral steroids and four patients (7 eyes) received a combination of oral doxycycline, oral steroid and intravitreal anti-vascular endothelial growth factor (IVA). Significant improvement was evident at 8 weeks in median BCVA (0.50, IQR: 0.3–0.8, p < 0.05) and median CFT (223 micron, IQR: 170–256, p < 0.05) though only 26% (5 eyes) attained BCVA > = 6/12.

Conclusion:

Our study puts forth certain characteristic fundus and OCT features of PFR. A combination of oral doxycycline and oral steroids as a treatment option showed improvement in BCVA and CFT. Additional IVA helps in faster visual recovery in patients presenting with severe macular edema at onset.

Recent Advances in Diagnosis and Treatment of Infectious Uveitis Prevalent in Asia-Pacific Region

ABSTRACT

The role of infections in intraocular inflammation is being increasingly recognized across the world. The Asia-Pacific region, being the single largest and most populous geographical entity on the planet, is home to a wide variety of such infections. Not surprisingly, there has been an explosion in the literature on infectious uveitis emerging from Asia-Pacific countries. In this review, we have covered recent advances in the diagnosis, treatment, and pathogenesis of common forms of infectious uveitis from the Asia-Pacific region. Much of the literature is focussed on the diagnosis of these infections by clinical criteria and laboratory investigations. There has also been an increased emphasis on the application of newer modes of ocular imaging and understanding pathomechanisms of ocular inflammation in these infections. Together this research has significantly improved our understanding of the diagnosis and management of infectious uveitis.

Role of Ocular Imaging in Diagnosis and Determining Response to Therapeutic Interventions in Posterior and Panuveitis

ABSTRACT

This review provides a comprehensive description and careful interpretation of various ocular imaging techniques to visualize the different ocular structures in posterior and panuveitis. This can help in the diagnosis, follow-up, and monitoring the response to treatment in patients with different posterior and panuveitic entities.

Post-fever retinitis - Newer concepts

Post-fever retinitis (PFR) is an infectious or para-infectious uveitic entity caused by bacterial or viral agents and seen mainly in tropical countries. Systemic symptoms such as joint pain, skin rash are common during the febrile stage. On the basis of only clinical presentation, it is difficult to pin-point the exact etiology for PFR. Serological investigations, polymerase chain reaction, and knowledge of concurrent epidemics in the community may help to identify the etiological organism. Bacterial causes of PFR such as rickettsia and typhoid are treated with systemic antibiotics, with or without systemic steroid therapy, whereas PFR of viral causes such as chikungunya, dengue, West Nile virus, and Zika virus have no specific treatment and are managed with steroids. Nevertheless, many authors have advocated mere observation and the uveitis resolved with its natural course of the disease. In this article, we have discussed the clinical features, pathogenesis, investigations, and management of PFR.

Anti-vascular endothelial growth factor in the treatment of macular edema in epidemic retinitis

PURPOSE

To study efficacy of anti-vascular endothelial growth factor (anti-VEGF) in resolution of macular edema in epidemic retinitis (ER).

METHODS

In this retrospective, comparative study, patients diagnosed as ER with central macular thickness (CMT) ≥ 600 μm on SD-OCT at presentation were studied. Eyes which did not receive intravitreal anti-VEGF formed group A and eyes receiving additional anti-VEGF formed group B. Eyes receiving anti-VEGF monotherapy were studied separately. Cases with subsequent OCT scans with interval of more than 20 days and cases without OCT scan at the resolution were excluded. Treatment details, visual outcome, and days to resolution of macular edema were studied.

RESULTS

Mean CMT in group A (n = 8) was 820.1 μm (range 607-1004 μm) and in Group B (n = 4) was 756.0 μm (range 603-1000 μm). Macular edema resolved in 34.8 days (range: 16-65) and 39.0 days (range: 21-45) in group A and B, respectively. Two eyes with anti-VEGF monotherapy recovered in 45 and 18 days, respectively. Mean corrected distance visual acuity (CDVA) at presentation in group A was 19.1 (range: 0-61) ETDRS letters and in group B was 14.3 (range: 0-35) ETDRS letters. Mean CDVA improved to 65.7 (range: 0-85) and 50.8 (range: 20-76) ETDRS letters in group A and B, respectively. Anti-VEGF monotherapy eyes improved from 35 and 46 ETDRS letters to 70 and 85 ETDRS letters, respectively.

CONCLUSION

Additional anti-VEGF therapy has no added advantage in speed of resolution of macular edema due to ER. A randomized controlled trial with steroids sparing "anti-VEGF monotherapy" may verify our observations.

Rickettsia conorii retinitis: an emerging infection in the southeast of the Iberian Peninsula

CASE REPORT

A case is presented of a 60-year-old patient with loss of visual acuity in both eyes after fever and skin rash with palmoplantar involvement. After a complete examination and relevant complementary tests, the diagnosis of retinitis was made in the context of Rickettsia conorii infection. The evolution after treatment with doxycycline and prednisone at six weeks with significant anatomical and functional improvement is presented. Rickettsiosis is an emerging zoonosis that can present with ocular involvement. This is usually a multifocal retinitis affecting posterior pole with macular serous detachment and vitritis. Clinical suspicion will require serological confirmation for a definitive diagnosis. Treatment with antibiotics and corticosteroids has been shown to be effective. It should be taken into account in Mediterranean endemic areas, and in in the summer period, where the risk is much higher.

Epidemic Retinitis with Macular Edema -Treatment Outcome with and without Steroids

Purpose: To study treatment outcomes with and without oral corticosteroids in epidemic retinitis (ER).Method: A retrospective, observational study of 35 eyes of 29 patients diagnosed as ER. Days taken for resolution of macular edema and retinitis lesions were compared in patients treated with oral antibiotics (Group 1) and with corticosteroids-antibiotics combination (Group 2).Result: Eighteen eyes of 14 patients and 17 eyes of 15 patients formed Groups 1 and 2, respectively. At the presentation, mean best-corrected visual acuity (BCVA) was 40 and 44 letters and mean central macular thickness was 648 (±243) and 626 (±256) microns in Groups 1 and 2, respectively. Macular edema resolved in 30.83 and 31.94 days; retinitis lesions resolved in 36.71 and 41.41 days in Groups 1 and 2, respectively. BCVA improved to 74 and 77 letters in Groups 1 and 2, respectively.Conclusion: ER with macular edema can be well managed without corticosteroids.

Optical coherence tomography angiography features of retinitis post-rickettsial fever

The intraocular manifestations of rickettisial retinitis include retinal vasculitis, maculopathy, optic neuritis, and neurosensory detachment. Extensive leakage of dye on the fundus fluorescein angiography may obscure visualization in eyes with retinitis. We report the vascular changes in eyes with rickettsial retinitis and its response to treatment using optical coherence tomography angiography. The microvascular abnormalities we noted were, capillary drop out areas corresponding to retinitis patches, vascular loops, and pruning of vessels. The choriocapillary slabs showed signal void areas. Post-treatment there was vascular remodeling with decrease in non-perfused area, appearance of new vascular lateral branching, and appearance of collaterals.

Ocular manifestations of Rickettsia conorii in South India

Purpose:

Among the major groups of rickettsiosis, the commonly reported diseases in India are: (a) Typhus group induced—scrub typhus, murine flea-borne typhus; (b) Spotted fever group induced—Indian tick typhus; and (c) Q fever. Though many scrub typhus outbreaks have been reported from India, only one outbreak of spotted fever—serologically proven Indian tick typhus (Rickettsia conorii)—has been reported. We report for the first time ocular manifestations of serologically proven R. conorii infection in a cluster of patients.

Methods:

In this retrospective study, case records patients with serologically proven Indian tick typhus (Rickettsia conorii) were reviewed for clinical manifestations and treatment outcomes.

Results:

In the months of February to April 2016, a cluster of 12 patients (23 eyes) visited us with defective vision. Examination showed multifocal retinitis; mostly bilateral; patients had a history of fever approximately 4 weeks prior to onset of symptoms. After excluding other causes of multifocal retinitis, a diagnosis of rickettsial retinitis was made after Weil–Felix test (WFT) was significantly positive, and enzyme-linked immunosorbent assay was positive for R. conorii. Course of the disease, visual outcome, and investigations are discussed. Doxycycline along with oral corticosteroids was effective in treating the condition.

Conclusion:

Systematic fundus examination should be part of the routine evaluation of any patient who presents with fever and/or skin rash living in or returning from a specific endemic area. Clinical clues to diagnosing ocular rickettsiosis could be multifocal retinitis predominantly involving the posterior pole and macular involvement in the form of serous macular detachment or macular hard exudates. A positive WFT still serves as a useful and cheap diagnostic tool for laboratory diagnosis of rickettsial disease. Doxycycline along with oral corticosteroids was effective in treating the condition.

Clinical Profile of Scrub Typhus Meningoencephalitis among South Indian Children

Re-emerging scrub typhus is gaining recognition as an important cause of paediatric meningoencephalitis in tropics. We studied the clinical profile of scrub typhus meningoencephalitis (STME) in children <12 years. Of 270 serology-confirmed cases of scrub typhus, 14 (5%) had features consistent with STME and 9 (64%) of these children were between 5 and 12 years of age; 12 (85%) children presented to the hospital during the second week of illness. Fever, headache and altered sensorium were observed in all children, while meningeal signs, papilledema and seizures were observed in 8 (57%), 7 (50%) and 6 (43%) children, respectively. The mean CSF protein level, glucose level, cell count and percentage of lymphocytes were 75 mg/dl, 46 mg/dl, 41 cells and 86%, respectively. STME should be considered in febrile children from endemic area with neurological features, such as headache or altered sensorium. Lumbar puncture is mandatory to confirm STME and rule out close differential diagnosis, such as pyogenic and tubercular meningitis.

An imaging-based treatment algorithm for posterior focal retinitis

Background:

In this paper, our aim was to describe an imaging-based empirical approach for categorizing and initiating treatment of immunocompetent patients with posterior focal retinitis, prior to the availability of results of expensive laboratory investigations.

Materials and methods:

The hospital records of 13 patients with posterior focal retinitis were reviewed.

Results:

Of the 13 patients, 9 were women and 4 were men. The mean age was 24 ± 8 years. Based on similarities in clinical presentation and imaging, we categorized our cases into three groups with different first-line therapeutic strategies. In the first group, patients had presumed toxoplasmosis (treated with oral cotrimoxazole); in the second group, patients had presumed viral (herpetic) etiology (treated with oral valacyclovir); and in the third group, patients had presumed nonherpetic, nontoxoplasma retinitis (treated with oral doxycycline). Positive serology results included Rickettsia (two patients), Borrelia (one patient), Toxoplasma (two patients), and herpes simplex virus (one patient).

Conclusion:

An empirical approach for early initiation of therapy in retinitis cases based on imaging features is described.

Ocular manifestations of rickettsia in children: common but frequently overlooked

We review two cases of ocular manifestations of Rickettsia conorii infection in children. A girl who presented unilateral visual loss with focal retinitis and macular oedema and a boy with unilateral central scotoma and bilateral anterior uveitis. Progressive functional and anatomic recovery was observed after oral antibiotics and steroids were initiated.

Epidemic Retinitis

Purpose: To study demography, seasonal variation, clinical presentation, and treatment outcome of "retinitis post febrile illness." (RpFI) Method: Case records of patients diagnosed as RpFI, from July 2009 to May 2017 were studied retrospectively. Patients with complete follow up were evaluated for treatment and visual outcomes. Results: Two hundred and five eyes of 119 patients were studied. The peak incidence of RpFI was from November to March each year. Diagnosis of fever largely remained unknown. Chikungunya IgM, Dengue IgM, and Weil-Felix test was positive in 22.22%, 15.38%, and 39.75%, respectively, in investigated cases. The mean visual acuity at presentation and at resolution was 20/63 and 20/32, respectively, in 122 eyes with complete follow up. Conclusion: We suggest a term "Epidemic Retinitis" for RpFI due to its seasonal variation and to differentiate it from other sporadic forms of retinitis. Although RpFI has aggressive presentation, it resolves over 3-4 months and the overall visual outcome is satisfactory.

Rickettsial retinitis: Direct bacterial infection or an immune-mediated response?

Infectious retinitis postfebrile illness is known to be caused by chikungunya, dengue, West Nile virus, Bartonella, Lyme's disease, Rift Valley fever, rickettsia, Herpes viruses etc. Rickettsia is Gram-negative bacteria transmitted by arthropods vectors. Ocular involvement is common including conjunctivitis, keratitis, anterior uveitis, panuveitis, retinitis, retinal vascular changes, and optic nerve involvement. Retinitis lesions in rickettsia can occur because of an immunological response to the bacteria or because of direct invasion and proliferation of bacteria in the inner retina. We report such a case of bilateral rickettsial retinitis proven by serology which worsened on systemic steroids and responded dramatically to therapy with oral doxycycline and steroid taper. We thus believe that direct bacterial invasion plays a major role in the pathogenesis of rickettsial retinitis.

Author's reply to 'Rickettsia retinitis cases in India: a few comments'

Diagnosis of rickettsial retinitis remains presumptive when gold standard tests are not available or not done due to financial constrains. History of tick bite followed by fever with skin rash particularly in winter and spring season may point towards Rickettsiosis. The absence of scarring post resolution of rickettsial retinitis suggests inner retinal involvement in contrast to toxoplasmosis. Bilaterality of the disease, 2–4 weeks of latent period, and multifocal nature of retinitis lesions (cotton wool spot-like lesions) especially around the disc and posterior pole may suggest an immune response to recent systemic infection. The use of only antibiotics or only steroids or both together for treatment of rickettsial retinitis is controversial and warrants randomized controlled trials.

Rickettsia retinitis cases in India: a few comments

An important cause of infectious retinitis, not well-described in Indian literature, has been analyzed in detail systematically by Kawali A. and colleagues. However, Rickettsia retinitis (RR) was diagnosed at titres of 1:160 by the Weil–Felix test (WFT). The sensitivity and specificity of WFT at this level are poor compared to the gold standard immunofluorescent antibody assay. However, we understand that financial constraints of the Indian patients limit the availability of more definite tests. In our opinion, the optical coherence tomography features of RR described by the authors may be mimicked by other causes of retinitis, such as toxoplasma retinitis or even cotton wool spots. Infectious retinitis including RR should be treated by an antimicrobial agent with or without oral steroids until larger series or randomized controlled trials prove otherwise.