Although this quote applies to all aspects of life, it is remarkably true for various pathological conditions, among which this article aims to shed light on peripheral retinal degenerations.

There are two major areas constituting the retina: the central and the peripheral retina. Detailed visual activity falls in the realm of the macula, which lies in the centre of the retina. It is composed of tightly packed cells called “cones,” while the reverse is true for the peripheral retina, which is responsible for night vision and mainly dominated by “rods.” Although the periphery makes up more than 90% of the retina, its defects remain relatively under-discussed.

It is of vital importance to acknowledge the role of the vitreous in such cases. The vitreous acts as a supporting gel for the eye, holding it in place and aiding the retina in visual perception. However, with age, its consistency begins to waver, resulting in gradual liquefaction and degeneration. The appearance of vitreous floaters (to varying degrees) is a hallmark of this. Floaters can appear in multiple ways: as tiny moving dots, thin lines, or grey specks. Individuals with significant vitreous degeneration in turn develop posterior vitreous detachment (PVD), which is the absolute separation of the posterior vitreous from the internal limiting membrane (first layer) of the retina. Etiologically, it is characterised by two main phenomena, known as synchysis (vitreous liquefaction) and syneresis (aggregation of collagen fibrils leading to vitreous collapse).

Apart from age, there are several other factors that influence the otherwise spontaneous process of posterior vitreous detachment. Recent eye surgery, trauma, uveitis, cataracts, and a family history of the pathology are among them. The pattern of progression of posterior vitreous detachment is of enormous significance. Symptoms are mild in steady and uniform progression, but if there is a greater force of separation or an abnormal adhesion present between the vitreous and the retina, the posterior vitreous degeneration can take the ugly form of a retinal tear.

Therefore, it is crucial to understand the implications as well as the complications of vitreous detachment and how it can lead to peripheral retinal degenerations.

Simply put, peripheral retinal degenerations are common lesions of the surrounding retina. Based on the depth of retinal changes observed on optical coherence tomography (OCT), they can be classified into three broad categories: Intraretinal, Vitreoretinal and Chorioretinal. Among these, the influence of posterior vitreous detachment is specifically seen in Vitreoretinal degenerations. Its different types include lattice degeneration, retinal holes, snail track degeneration, retinal tufts, and peripheral retinal tears.




Lattice degeneration refers to an abnormal thinning of the retinal tissue, causing a “lattice-like” appearance and indicating weak side vision. It is usually found in high-myopic patients and may also appear in rare genetic diseases such as Ehlers-Danlos, Stickler syndrome, and Marfan syndrome.

Lattice degeneration, along with vitreous detachment, can act as a precursor of retinal detachment. These tears or breaks appear at the thin edge of the retina, and may be either horseshoe or circular shaped. Lattices are notorious for being typically asymptomatic, sometimes accompanied by flashes of light or floaters. Therefore, the only way to diagnose the condition is through a dilated fundus examination. Clinically, it is identified by patches of thinned retina,

which may be oval or straight in shape, along with clumps of pigment. In a technique known as scleral depression, a negligible amount of pressure is exerted around the eye to gain a better view of the peripheral retina, and these lesions are diagnosed.

Given its unpredictability, it is especially necessary to look into the predisposing factors of lattice degeneration to gain a better understanding of whether the patient requires treatment or not. Certain questions help us determine this, such as:

    * Does the patient have a family history of retinal detachment?
    * Has the patient experienced retinal detachment in one eye already?
    * Does the patient have only one functional eye?
    * Does the patient exhibit the relevant symptoms, such as multiple flashes, floaters, or blurred vision?
    * Does the patient have a horse shoe tear with surrounding sub-retinal fluid?


The answers to all of these questions can lead to a simpler, more definitive diagnosis of the condition and make room for earlier treatment and a better prognosis. The treatment, however, is quite straightforward, in terms of performing a barrage laser photocoagulation. The goal of this treatment is to form adhesions around the thinned-out lattice or retinal break in order to prevent retinal detachment. It is extremely vital to understand and reiterate that these procedures are not the total cure for the condition, and may only assure that it doesn’t progress into further complications leading to vision loss. Periodic dilated eye examinations are necessary not just for patients with lattice degeneration, but also for those who are vulnerable to developing it.



It is highly crucial to emphasise that a laser barrage is not a 100% assurance against developing a retinal detachment in the future. It is more like wearing a helmet while driving; that is, it would minimise the risk of having a complication in case of an accident, but there is no guarantee whatsoever. Henceforth, awareness and understanding of the disease are almost as important as the treatment itself. All roads of vitreo-retinal impairment could ultimately lead to different retinal complications, which may prove to be a dead end if not treated wisely. Hence, in the case of peripheral retinal degeneration, a dilated retinal examination is of prime importance, and a judgement can be made thereafter as to whether a laser barrage is required or not.


Authors:

Dr. Dhaivat Shah (Vitreoretinal Surgeon)

Dr. Ananta Barvey (Medical student)