CaseWise 24

Association of Retinal Nerve Fiber Layer Thickness and Systemic Hypertension

Dr. Swati Mishra, Dr. Sarang Lambat, Dr. Vinay Nangia
Suraj Eye Institute, Nagpur, India

Introduction:
Autoregulation is an important blood flow regulatory mechanism existing in retina and optic nerve head. It helps to keep the blood flow relatively constant during changes in perfusion pressure. The perfusion pressure depends on blood pressure. ⁽¹⁾ Several studies have reported that changes in systemic BP can affect ocular blood flow, which is associated with the progression of glaucoma. It has been reported that hypertensive patients with no retinal abnormalities or glaucomatous changes showed inner retinal layer thinning including the ganglion cell-inner plexiform layer (GC-IPL) and peripapillary retinal nerve fiber layer (RNFL).  It is speculated that chronic ischemia caused by retinal microvascular disorders might cause changes in retinal structure. ⁽²⁾
Case details:
A male, 42 years of age, came with complaints of blurred vision in left eye and diplopia since 3 days. There was no history of similar complaints in the past. Patient was not a known diabetic or hypertensive and was not on any systemic medications. Upon examination his visual acuity was 6/6, N6 in both eyes (BE). Anterior segment examination was normal with IOP of 13 mmHg in BE. Posterior segment examination showed sclerosed vessels with cotton wool spots in right eye (RE) (Fig 1). Left eye (LE) showed infero-temporal  RNFL wedge defect (Fig 2). Spectral domain optical coherence tomography (SD-OCT) of right eye showed reduced RNFL thickness in supero-temporal quadrant (Fig 3).  SD-OCT of left eye showed reduced RNFL thickness in infero-temporal quadrant. (Fig 4) . OCT findings were correlating to the clinical findings. His random blood sugar was 142 mg/dL and BP was 204/134 mmHg.

Discussion:
In our case with evidence of retinal microvascular changes and RNFL loss we were able to subject the patient for systemic evaluation which led to the diagnosis of glaucoma. Hypertension has a range of effects on the eye. Hypertensive retinopathy refers to retinal microvascular changes that develop in response to raised blood pressure.  Hypertension is also a major risk factor for the development of other retinal vascular diseases including retinal vein and artery occlusion, and ischaemic optic neuropathy. It has also been implicated in the pathogenesis of glaucoma and age-related macular degeneration.⁽³⁾  RNFL analysis on SDOCT provides an objective assessment of the optic nerve and neuroretinal rim as well as a quantitative estimation of retinal ganglion cell axonal loss that happens in glaucoma.⁽⁴⁾ Numerous studies have reported that retinal microvascular abnormalities lead to glaucoma and are related to both the presence and severity of hypertension. The strength of association between retinal microvascular abnormalities and hypertension has been observed to vary with age and race. The association appears to be stronger in younger compared to older persons.⁽⁵⁾ We demonstrated the effects of hypertension on the RNFL with this case.

References

1. Wong T., Mitchell P Gangwani Rita A., Lee Jacky W.Y., H.Y. Mo, Sum Rita, Kwong Alfred S.K.; The Correlation of Retinal Nerve Fiber Layer Thickness With Blood Pressure in a Chinese Hypertensive Population. Medicine (Baltimore). 2015 Jun; 94(23): e947. DOI: 10.1097/MD.0000000000000947
2. Lim H, Lee M, Park J, Kyeung K, Joon Y, Kim J; Changes in Ganglion Cell-Inner Plexiform Layer Thickness and Retinal Microvasculature in Hypertension: An OCT Angiography Study  DOI: 10.1016/j.ajo.2018.11.016
3. The eye in hypertension; Lancet 2007; 369: 425–35. DOI: 10.1016/S0140-6736(07)60198-6
4. Luis E. Vazquez and Linda Y. Huang; RNFL Analysis in the Diagnosis of Glaucoma. Glaucoma Today May/June 2016. https://glaucomatoday.com/articles/2016-may-june/rnfl-analysis-in-the-diagnosis-of-glaucoma
5. Wong T.,Klein R., Klein B., Tielsch M., Hubbard L, Nieto J.: Retinal Microvascular Abnormalities and their Relationship with Hypertension, Cardiovascular Disease, and Mortality. Survey Ophthalmol. Jul-Aug 2001;46(1):59-80 DOI: 10.1016/s0039-6257(01)00234-x