diff --git a/platform/core/package.json b/platform/core/package.json
index 93a9bea38..33d6f60ea 100644
--- a/platform/core/package.json
+++ b/platform/core/package.json
@@ -45,6 +45,7 @@
     "lodash.clonedeep": "^4.5.0",
     "lodash.merge": "^4.6.1",
     "mousetrap": "^1.6.3",
-    "validate.js": "^0.12.0"
+    "validate.js": "^0.12.0",
+    "immer": "6.0.2"
   }
 }
diff --git a/platform/core/src/redux/reducers/viewports.js b/platform/core/src/redux/reducers/viewports.js
index 5396e226c..88c4fc7bd 100644
--- a/platform/core/src/redux/reducers/viewports.js
+++ b/platform/core/src/redux/reducers/viewports.js
@@ -1,5 +1,5 @@
 import cloneDeep from 'lodash.clonedeep';
-import merge from 'lodash.merge';
+import produce from 'immer';
 
 import {
   CLEAR_VIEWPORT,
@@ -93,12 +93,13 @@ const viewports = (state = DEFAULT_STATE, action) => {
      * @return {Object} New state.
      */
     case SET_VIEWPORT_ACTIVE: {
-      const activeViewportIndex = getActiveViewportIndex(
-        state.numRows,
-        state.numColumns,
-        action.viewportIndex
-      );
-      return { ...state, activeViewportIndex };
+      return produce(state, draftState => {
+        draftState.activeViewportIndex = getActiveViewportIndex(
+          draftState.numRows,
+          draftState.numColumns,
+          action.viewportIndex
+        );
+      });
     }
 
     /**
@@ -163,21 +164,20 @@ const viewports = (state = DEFAULT_STATE, action) => {
      * @return {Object} New state.
      */
     case SET_VIEWPORT: {
-      const layout = cloneDeep(state.layout);
+      return produce(state, draftState => {
+        draftState.viewportSpecificData[action.viewportIndex] =
+          draftState.viewportSpecificData[action.viewportIndex] || {};
 
-      let viewportSpecificData = cloneDeep(state.viewportSpecificData);
-      viewportSpecificData[action.viewportIndex] = merge(
-        {},
-        viewportSpecificData[action.viewportIndex],
-        action.viewportSpecificData
-      );
+        Object.keys(action.viewportSpecificData).forEach(key => {
+          draftState.viewportSpecificData[action.viewportIndex][key] =
+            action.viewportSpecificData[key];
+        });
 
-      if (action.viewportSpecificData && action.viewportSpecificData.plugin) {
-        layout.viewports[action.viewportIndex].plugin =
-          action.viewportSpecificData.plugin;
-      }
-
-      return { ...state, layout, viewportSpecificData };
+        if (action.viewportSpecificData && action.viewportSpecificData.plugin) {
+          draftState.layout.viewports[action.viewportIndex].plugin =
+            action.viewportSpecificData.plugin;
+        }
+      });
     }
 
     /**
diff --git a/platform/viewer/src/components/ViewportGrid/ConnectedViewportGrid.js b/platform/viewer/src/components/ViewportGrid/ConnectedViewportGrid.js
index 774b10401..be4b693c0 100644
--- a/platform/viewer/src/components/ViewportGrid/ConnectedViewportGrid.js
+++ b/platform/viewer/src/components/ViewportGrid/ConnectedViewportGrid.js
@@ -2,15 +2,20 @@ import ViewportGrid from './ViewportGrid.js';
 import { MODULE_TYPES } from '@ohif/core';
 import { connect } from 'react-redux';
 import { extensionManager } from './../../App.js';
+import memoize from 'lodash/memoize';
 
-const mapStateToProps = state => {
+const getAvailableViewportModules = memoize(viewportModules => {
   const availableViewportModules = {};
-  const viewportModules = extensionManager.modules[MODULE_TYPES.VIEWPORT];
-
   viewportModules.forEach(moduleDefinition => {
     availableViewportModules[moduleDefinition.extensionId] =
       moduleDefinition.module;
   });
+  return availableViewportModules;
+});
+
+const mapStateToProps = state => {
+  const viewportModules = extensionManager.modules[MODULE_TYPES.VIEWPORT];
+  const availableViewportModules = getAvailableViewportModules(viewportModules);
 
   // TODO: Use something like state.plugins.defaultPlugin[MODULE_TYPES.VIEWPORT]
   let defaultPlugin;
diff --git a/platform/viewer/src/components/ViewportGrid/ViewportGrid.js b/platform/viewer/src/components/ViewportGrid/ViewportGrid.js
index ac17cd8c8..7aa497568 100644
--- a/platform/viewer/src/components/ViewportGrid/ViewportGrid.js
+++ b/platform/viewer/src/components/ViewportGrid/ViewportGrid.js
@@ -39,66 +39,68 @@ const ViewportGrid = function(props) {
     });
   }, [viewportData]);
 
-  const ViewportPanes = layout.viewports.map((layout, viewportIndex) => {
-    const displaySet = viewportData[viewportIndex];
+  const getViewportPanes = () =>
+    layout.viewports.map((layout, viewportIndex) => {
+      const displaySet = viewportData[viewportIndex];
 
-    if (!displaySet) {
-      return null;
-    }
+      if (!displaySet) {
+        return null;
+      }
 
-    const data = {
-      displaySet,
-      studies,
-    };
+      const data = {
+        displaySet,
+        studies,
+      };
 
-    // JAMES TODO:
+      // JAMES TODO:
 
-    // Use whichever plugin is currently in use in the panel
-    // unless nothing is specified. If nothing is specified
-    // and the display set has a plugin specified, use that.
-    //
-    // TODO: Change this logic to:
-    // - Plugins define how capable they are of displaying a SopClass
-    // - When updating a panel, ensure that the currently enabled plugin
-    // in the viewport is capable of rendering this display set. If not
-    // then use the most capable available plugin
-    const pluginName =
-      !layout.plugin && displaySet && displaySet.plugin
-        ? displaySet.plugin
-        : layout.plugin;
+      // Use whichever plugin is currently in use in the panel
+      // unless nothing is specified. If nothing is specified
+      // and the display set has a plugin specified, use that.
+      //
+      // TODO: Change this logic to:
+      // - Plugins define how capable they are of displaying a SopClass
+      // - When updating a panel, ensure that the currently enabled plugin
+      // in the viewport is capable of rendering this display set. If not
+      // then use the most capable available plugin
+      const pluginName =
+        !layout.plugin && displaySet && displaySet.plugin
+          ? displaySet.plugin
+          : layout.plugin;
 
-    const ViewportComponent = _getViewportComponent(
-      data, // Why do we pass this as `ViewportData`, when that's not really what it is?
-      viewportIndex,
-      children,
-      availablePlugins,
-      pluginName,
-      defaultPluginName
-    );
+      const ViewportComponent = _getViewportComponent(
+        data, // Why do we pass this as `ViewportData`, when that's not really what it is?
+        viewportIndex,
+        children,
+        availablePlugins,
+        pluginName,
+        defaultPluginName
+      );
 
-    return (
-      <ViewportPane
-        onDrop={({
-          viewportIndex,
-          StudyInstanceUID,
-          displaySetInstanceUID,
-        }) => {
-          setViewportData({
-            viewportIndex,
-            StudyInstanceUID,
-            displaySetInstanceUID,
-          });
-        }}
-        viewportIndex={viewportIndex} // Needed by `setViewportData`
-        className={classNames('viewport-container', {
-          active: activeViewportIndex === viewportIndex,
-        })}
-        key={viewportIndex}
-      >
-        {ViewportComponent}
-      </ViewportPane>
-    );
-  });
+      return (
+        <ViewportPane
+          onDrop={setViewportData}
+          viewportIndex={viewportIndex} // Needed by `setViewportData`
+          className={classNames('viewport-container', {
+            active: activeViewportIndex === viewportIndex,
+          })}
+          key={viewportIndex}
+        >
+          {ViewportComponent}
+        </ViewportPane>
+      );
+    });
+
+  const ViewportPanes = React.useMemo(getViewportPanes, [
+    layout,
+    viewportData,
+    studies,
+    children,
+    availablePlugins,
+    defaultPluginName,
+    setViewportData,
+    activeViewportIndex,
+  ]);
 
   return (
     <div
diff --git a/platform/viewer/src/connectedComponents/ViewerMain.js b/platform/viewer/src/connectedComponents/ViewerMain.js
index 1b12369b6..c55aa4da7 100644
--- a/platform/viewer/src/connectedComponents/ViewerMain.js
+++ b/platform/viewer/src/connectedComponents/ViewerMain.js
@@ -4,6 +4,10 @@ import { Component } from 'react';
 import { ConnectedViewportGrid } from './../components/ViewportGrid/index.js';
 import PropTypes from 'prop-types';
 import React from 'react';
+import memoize from 'lodash/memoize';
+import _values from 'lodash/values';
+
+var values = memoize(_values);
 
 class ViewerMain extends Component {
   static propTypes = {
@@ -140,9 +144,7 @@ class ViewerMain extends Component {
 
   render() {
     const { viewportSpecificData } = this.props;
-    const viewportData = viewportSpecificData
-      ? Object.values(viewportSpecificData)
-      : [];
+    const viewportData = values(viewportSpecificData);
 
     return (
       <div className="ViewerMain">
diff --git a/yarn.lock b/yarn.lock
index cb381a7db..10e7b245b 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -9922,6 +9922,11 @@ immer@1.10.0:
   resolved "https://registry.yarnpkg.com/immer/-/immer-1.10.0.tgz#bad67605ba9c810275d91e1c2a47d4582e98286d"
   integrity sha512-O3sR1/opvCDGLEVcvrGTMtLac8GJ5IwZC4puPrLuRj3l7ICKvkmA0vGuU9OW8mV9WIBRnaxp5GJh9IEAaNOoYg==
 
+immer@6.0.2:
+  version "6.0.2"
+  resolved "https://registry.yarnpkg.com/immer/-/immer-6.0.2.tgz#5bc08dc4930c756d0749533a2afbd88c8de0cd19"
+  integrity sha512-56CMvUMZl4kkWJFFUe1TjBgGbyb9ibzpLyHD+RSKSVdytuDXgT/HXO1S+GJVywMVl5neGTdAogoR15eRVEd10Q==
+
 immutable@>=3.6.0:
   version "3.8.2"
   resolved "https://registry.yarnpkg.com/immutable/-/immutable-3.8.2.tgz#c2439951455bb39913daf281376f1530e104adf3"